Unequal curvature of the refractive surfaces of the eye. Thus a point source of light cannot be brought to a point focus on the retina but is spread over a more or less diffuse area. This results from the radius of curvature in one plane being longer or shorter than the radius at right angles to it. (Dorland, 27th ed)
Refraction of LIGHT effected by the media of the EYE.
The measurement of curvature and shape of the anterior surface of the cornea using techniques such as keratometry, keratoscopy, photokeratoscopy, profile photography, computer-assisted image processing and videokeratography. This measurement is often applied in the fitting of contact lenses and in diagnosing corneal diseases or corneal changes including keratoconus, which occur after keratotomy and keratoplasty.
Deviations from the average or standard indices of refraction of the eye through its dioptric or refractive apparatus.
An objective determination of the refractive state of the eye (NEARSIGHTEDNESS; FARSIGHTEDNESS; ASTIGMATISM). By using a RETINOSCOPE, the amount of correction and the power of lens needed can be determined.
A refractive error in which rays of light entering the EYE parallel to the optic axis are brought to a focus in front of the RETINA when accommodation (ACCOMMODATION, OCULAR) is relaxed. This results from an overly curved CORNEA or from the eyeball being too long from front to back. It is also called nearsightedness.
A refractive error in which rays of light entering the eye parallel to the optic axis are brought to a focus behind the retina, as a result of the eyeball being too short from front to back. It is also called farsightedness because the near point is more distant than it is in emmetropia with an equal amplitude of accommodation. (Dorland, 27th ed)
Clarity or sharpness of OCULAR VISION or the ability of the eye to see fine details. Visual acuity depends on the functions of RETINA, neuronal transmission, and the interpretative ability of the brain. Normal visual acuity is expressed as 20/20 indicating that one can see at 20 feet what should normally be seen at that distance. Visual acuity can also be influenced by brightness, color, and contrast.
Partial or total replacement of all layers of a central portion of the cornea.
Techniques for securing together the edges of a wound, with loops of thread or similar materials (SUTURES).
A condition of an inequality of refractive power of the two eyes.
The transparent anterior portion of the fibrous coat of the eye consisting of five layers: stratified squamous CORNEAL EPITHELIUM; BOWMAN MEMBRANE; CORNEAL STROMA; DESCEMET MEMBRANE; and mesenchymal CORNEAL ENDOTHELIUM. It serves as the first refracting medium of the eye. It is structurally continuous with the SCLERA, avascular, receiving its nourishment by permeation through spaces between the lamellae, and is innervated by the ophthalmic division of the TRIGEMINAL NERVE via the ciliary nerves and those of the surrounding conjunctiva which together form plexuses. (Cline et al., Dictionary of Visual Science, 4th ed)
The removal of a cataractous CRYSTALLINE LENS from the eye.
Diseases of the cornea.
A noninflammatory, usually bilateral protrusion of the cornea, the apex being displaced downward and nasally. It occurs most commonly in females at about puberty. The cause is unknown but hereditary factors may play a role. The -conus refers to the cone shape of the corneal protrusion. (From Dorland, 27th ed)
Insertion of an artificial lens to replace the natural CRYSTALLINE LENS after CATARACT EXTRACTION or to supplement the natural lens which is left in place.
A pair of ophthalmic lenses in a frame or mounting which is supported by the nose and ears. The purpose is to aid or improve vision. It does not include goggles or nonprescription sun glasses for which EYE PROTECTIVE DEVICES is available.
Artificial implanted lenses.
Gas lasers with excited dimers (i.e., excimers) as the active medium. The most commonly used are rare gas monohalides (e.g., argon fluoride, xenon chloride). Their principal emission wavelengths are in the ultraviolet range and depend on the monohalide used (e.g., 193 nm for ArF, 308 nm for Xe Cl). These lasers are operated in pulsed and Q-switched modes and used in photoablative decomposition involving actual removal of tissue. (UMDNS, 2005)
A surgical procedure to correct MYOPIA by CORNEAL STROMA subtraction. It involves the use of a microkeratome to make a lamellar dissection of the CORNEA creating a flap with intact CORNEAL EPITHELIUM. After the flap is lifted, the underlying midstroma is reshaped with an EXCIMER LASER and the flap is returned to its original position.
Asymmetries in the topography and refractive index of the corneal surface that affect visual acuity.
The use of an aberrometer to measure eye tissue imperfections or abnormalities based on the way light passes through the eye which affects the ability of the eye to focus properly.
A surgical technique to correct REFRACTIVE ERRORS of the EYE, such as MYOPIA and ASTIGMATISM. In this method, a flap of CORNEAL EPITHELIUM is created by exposure of the area to dilute alcohol. The flap is lifted and then replaced after laser ablation of the subepithelial CORNEA.
Presence of an intraocular lens after cataract extraction.
Application of tests and examinations to identify visual defects or vision disorders occurring in specific populations, as in school children, the elderly, etc. It is differentiated from VISION TESTS, which are given to evaluate/measure individual visual performance not related to a specific population.
Materials used in closing a surgical or traumatic wound. (From Dorland, 28th ed)
Surgical procedures employed to correct REFRACTIVE ERRORS such as MYOPIA; HYPEROPIA; or ASTIGMATISM. These may involve altering the curvature of the CORNEA; removal or replacement of the CRYSTALLINE LENS; or modification of the SCLERA to change the axial length of the eye.
A procedure to surgically correct REFRACTIVE ERRORS by cutting radial slits into the CORNEA to change its refractive properties.
Surgical techniques on the CORNEA employing LASERS, especially for reshaping the CORNEA to correct REFRACTIVE ERRORS.
A type of refractive surgery of the CORNEA to correct MYOPIA and ASTIGMATISM. An EXCIMER LASER is used directly on the surface of the EYE to remove some of the CORNEAL EPITHELIUM thus reshaping the anterior curvature of the cornea.
Relatively bright light, or the dazzling sensation of relatively bright light, which produces unpleasantness or discomfort, or which interferes with optimal VISION, OCULAR. (Cline et al., Dictionary of Visual Science, 4th ed)
A procedure for removal of the crystalline lens in cataract surgery in which an anterior capsulectomy is performed by means of a needle inserted through a small incision at the temporal limbus, allowing the lens contents to fall through the dilated pupil into the anterior chamber where they are broken up by the use of ultrasound and aspirated out of the eye through the incision. (Cline, et al., Dictionary of Visual Science, 4th ed & In Focus 1993;1(1):1)
The use of statistical and mathematical methods to analyze biological observations and phenomena.
A nonspecific term referring to impaired vision. Major subcategories include stimulus deprivation-induced amblyopia and toxic amblyopia. Stimulus deprivation-induced amblyopia is a developmental disorder of the visual cortex. A discrepancy between visual information received by the visual cortex from each eye results in abnormal cortical development. STRABISMUS and REFRACTIVE ERRORS may cause this condition. Toxic amblyopia is a disorder of the OPTIC NERVE which is associated with ALCOHOLISM, tobacco SMOKING, and other toxins and as an adverse effect of the use of some medications.
Partial or total replacement of the CORNEA from one human or animal to another.
Polymers where the main polymer chain comprises recurring amide groups. These compounds are generally formed from combinations of diamines, diacids, and amino acids and yield fibers, sheeting, or extruded forms used in textiles, gels, filters, sutures, contact lenses, and other biomaterials.
Albinism affecting the eye in which pigment of the hair and skin is normal or only slightly diluted. The classic type is X-linked (Nettleship-Falls), but an autosomal recessive form also exists. Ocular abnormalities may include reduced pigmentation of the iris, nystagmus, photophobia, strabismus, and decreased visual acuity.
Each of the upper and lower folds of SKIN which cover the EYE when closed.
An abnormal triangular fold of membrane in the interpalpebral fissure, extending from the conjunctiva to the cornea, being immovably united to the cornea at its apex, firmly attached to the sclera throughout its middle portion, and merged with the conjunctiva at its base. (Dorland, 27th ed)
Lenses, generally made of plastic or silicone, that are implanted into the eye in front of the natural EYE LENS, by the IRIS, to improve VISION, OCULAR. These intraocular lenses are used to supplement the natural lens instead of replacing it.
A series of tests used to assess various functions of the eyes.
The dioptric adjustment of the EYE (to attain maximal sharpness of retinal imagery for an object of regard) referring to the ability, to the mechanism, or to the process. Ocular accommodation is the effecting of refractive changes by changes in the shape of the CRYSTALLINE LENS. Loosely, it refers to ocular adjustments for VISION, OCULAR at various distances. (Cline et al., Dictionary of Visual Science, 4th ed)
A surgical specialty concerned with the structure and function of the eye and the medical and surgical treatment of its defects and diseases.
A bilateral retinopathy occurring in premature infants treated with excessively high concentrations of oxygen, characterized by vascular dilatation, proliferation, and tortuosity, edema, and retinal detachment, with ultimate conversion of the retina into a fibrous mass that can be seen as a dense retrolental membrane. Usually growth of the eye is arrested and may result in microophthalmia, and blindness may occur. (Dorland, 27th ed)
Agents that dilate the pupil. They may be either sympathomimetics or parasympatholytics.
Measurement of the thickness of the CORNEA.
Pieces of glass or other transparent materials used for magnification or increased visual acuity.

Results of small incision extracapsular cataract surgery using the anterior chamber maintainer without viscoelastic. (1/358)

AIMS: To assess the efficacy of extracapsular cataract surgery using the anterior chamber maintainer (ACM) without the use of viscoelastic. To compare the effects of this surgical technique on non-diabetic and diabetic patients. METHODS: A prospective single armed clinical trial of 46 eyes in 46 patients undergoing cataract surgery using the ACM without viscoelastic. Patients were assessed preoperatively and at 3 weeks, 3 months, and 12 months postoperatively. The main outcome variables included visual acuity, surgically induced astigmatic change (SIAC), changes in endothelial cell density (ECD), and morphology affecting the central and superior regions of the cornea. RESULTS: Postoperatively, 56% and 70% of patients had unaided visual acuities of 6/12 or better at 3 weeks and 3 months respectively. Even after excluding those patients with pre-existing maculopathy (including diabetic maculopathy), there remains a significant difference between the non-diabetic and diabetic groups in terms of the proportion of patients attaining an unaided visual acuity of 6/12 or better at both 3 weeks (p = 0.003) and 3 months (p = 0.001). Three months postoperatively, the SIAC based upon the keratometric and refractive data was 1.1 dioptres (D) and 1.3 D respectively. There was no statistically significant difference in the SIAC when the non-diabetic and diabetic groups were compared. The mean central and superior endothelial cell losses at 3 months postoperatively were 16% and 22% respectively and at 12 months postoperatively were 20% and 25% respectively. The diabetic group demonstrated greater endothelial cell losses and a more marked and protracted deviation of endothelial cell morphology from normality when compared with the non-diabetic group; however, the differences did not reach statistical significance. CONCLUSIONS: The efficacy of small incision cataract surgery using the ACM in terms of visual outcome and induced astigmatism is comparable with the results obtained using other techniques that utilise a similar size of incision. However, in view of the magnitude and range of the endothelial cell losses associated with this technique the concurrent use of viscoelastic is suggested. There does not appear to be a statistically or clinically significant difference between non-diabetic and diabetic patients in terms of the magnitude of the endothelial cell losses or in the wound healing response in the 12 months after cataract surgery using the ACM.  (+info)

Off-axis monochromatic aberrations estimated from double pass measurements in the human eye. (2/358)

Off-axis monochromatic aberrations in the human eye impose limits on peripheral vision. However, the magnitude of the aberrations off-axis, and in particular coma, has not been yet completely determined. We have developed a procedure to estimate third order aberrations in the periphery of the human eye. The technique is based on recording series of double pass retinal images with unequal entrance and exit pupil diameters (Artal, Iglesias, Lopez-Gil & Green (1995b). J. Opt. Soc. Am. A, 12, 2358-2366.) which allows the odd asymmetries in the retinal image be assessed. The procedure that is described provides accurate estimates of the main off-axis aberrations: astigmatism, defocus and coma. We have measured these aberrations in four normal subjects. For a given eccentricity, the measured amount of coma and astigmatism are relatively similar among subjects, because the angular distance from the axis is the dominant factor in determining the magnitude of these aberrations. However, we found considerable variability in the values of peripheral defocus, probably due to a complicate combination of off-axis aberrations and fundus shape. The final off-axis optical performance of the eye for a given object location is determined by a particular mixture of defocus, astigmatism, coma and higher order aberrations.  (+info)

Image quality in polypseudophakia for extremely short eyes. (3/358)

AIM: To evaluate the image quality produced by polypseudophakia used for strongly hypermetropic and nanophthalmic eyes. METHODS: Primary aberration theory and ray tracing analysis were used to calculate the optimum lens shapes and power distribution between the two intraocular lenses for two example eyes: one a strongly hypermetropic eye, the other a nanophthalmic eye. Spherical aberration and oblique astigmatism were considered. Modulation transfer function (MTF) curves were computed using commercial optical design software (Sigma 2100, Kidger Optics Ltd) to assess axial image quality, and the sagittal and tangential image surfaces were computed to study image quality across the field. RESULTS: A significant improvement in the axial MTF was found for the eyes with double implants. However, results indicate that this may be realised as a better contrast sensitivity in the low to mid spatial frequency range rather than as a better Snellen acuity. The optimum lens shapes for minimum spherical aberration (best axial image quality) were approximately convex-plano for both lenses with the convex surface facing the cornea. Conversely, the optimum lens shapes for zero oblique astigmatism were strongly meniscus with the anterior surface concave. Correction of oblique astigmatism was only achieved with a loss in axial performance. CONCLUSIONS: Optimum estimated visual acuity exceeds 6/5 in both the hypermetropic and the nanophthalmic eyes studied (pupil size of 4 mm) with polypseudophakic correction. These results can be attained using convex-plano or biconvex lenses with the most convex surface facing the cornea. If the posterior surface of the posterior intraocular lens is convex, as is commonly used to help prevent migration of lens epithelial cells causing posterior capsular opacification (PCO), then it is still possible to achieve 6/4.5 in the hypermetropic eye and 6/5.3 in the nanophthalmic eye provided the anterior intraocular lens has an approximately convex-plano shape with the convex surface anterior. It was therefore concluded that consideration of optical image quality does not demand that additional intraocular lens shapes need to be manufactured for polypseudophakic correction of extremely short eyes and that implanting the posterior intraocular lens in the conventional orientation to help prevent PCO does not necessarily limit estimated visual acuity.  (+info)

Cataract extraction and lens implantation with and without trabeculectomy: an intrapatient comparison. (4/358)

OBJECTIVE: To determine whether cataract extraction and lens implantation combined with trabeculectomy provides better long-term results than cataract extraction and lens implantation alone in a group of patients with primary open-angle glaucoma and cataract randomly selected to receive surgery with trabeculectomy in one eye and without in the other. METHODS: A prospective, randomized clinical trial involving 35 patients with bilateral symmetric primary open-angle glaucoma and visually disabling cataracts with procedures performed by a single surgeon in a private practice setting with follow-up for more than 5 years in all cases. RESULTS: After an average of 87 months of follow-up, cataract extraction and lens implantation reduced intraocular pressure 4.4 mm Hg, reduced number of medications by 1.28, increased diopter vector of astigmatism by 1.49, and was associated with visual field loss in 6 of 35 eyes. After an average of 80 months of follow-up, cataract extraction, lens implantation, and trabeculectomy reduced intraocular pressure 8.2 mm Hg, reduced number of medications by 1.76, increased diopter vector of astigmatism by 1.14, and was associated with visual field loss in 1 eye. Both groups had similar improvement in visual acuity and perioperative complications. CONCLUSIONS: Extracapsular cataract extraction, lens implantation, and trabeculectomy is a complex procedure that was beneficial in the long-term control of intraocular pressure and in prevention of visual field loss. This procedure should be considered in patients who may not be able to comply with a complex medical regimen, in whom pressure elevation in the immediate postoperative period would be undesirable, or in whom long-term pressure control at a lower level would be beneficial in preventing further optic nerve damage.  (+info)

Topographic and keratometric astigmatism up to 1 year following small flap trabeculectomy (microtrabeculectomy). (5/358)

AIM: To determine the induced corneal astigmatism by measuring the changes in manual keratometry and computerised corneal videokeratoscopy up to 1 year following small flap trabeculectomy (microtrabeculectomy). METHOD: A prospective study of a case series of small flap trabeculectomy procedures performed at the 90 degree meridian on 16 eyes of 16 patients, all followed to 1 year postoperatively. Changes in manual keratometry and computerised videokeratoscopy (Eyesys) readings were analysed by vector analysis and vector decomposition techniques. RESULTS: By vector analysis, the mean surgically induced refractive change (SIRC) cylinder power vectors induced at 1, 3, 6, and 12 months as measured by manual keratometry were 0.68, 0.38, 0.52, and 0.55 dioptres, and by keratography 0.75, 0.66, 0.59, and 0.64 dioptres. Vector decomposition on the induced vector cylinders on manual keratometry resulted in a "with the rule" mean vector of 0.52 and 0.22 dioptres at 1 and 3 months and an "against the rule" mean vector of 0.16 and 0.16 dioptres at the same time points (p=0.03 and 0.28 respectively). Vector decomposition at 6 and 12 months revealed no significant with the rule changes induced. Similar analysis on the videokeratoscopy results revealed significant induced with the rule astigmatism until 3 months, but not at 6 and 12 months postoperatively. CONCLUSION: Small flap trabeculectomy (microtrabeculectomy) produces smaller changes in corneal curvature that resolve sooner than previous reports of larger flap techniques.  (+info)

Screening for refractive errors in children: accuracy of the hand held refractor Retinomax to screen for astigmatism. (6/358)

AIMS: To assess the reliability of the hand held automated refractor Retinomax in measuring astigmatism in non-cycloplegic conditions. To assess the accuracy of Retinomax in diagnosing abnormal astigmatism in non-cycloplegic refractive screening of children between 9 and 36 months. METHODS: Among 1205 children undergoing a non-cycloplegic refractive screening with Retinomax, 299 (25%) had repeated non-cycloplegic measurements, 302 (25%) were refracted under cycloplegia using the same refractor, and 88 (7%) using retinoscopy or an automated on table refractor. The reproducibility of non-cycloplegic cylinder measurement was assessed by comparing the cylindrical power and axis values in the 299 repeated measurements without cycloplegia. The influence of the quick mode on cylinder measurement was analysed by comparing the cylinder and axis value in 93 repeated measurements without cycloplegia where normal mode was used in one measurement and quick mode in the other. Predictive values of the refractive screening were calculated for three different thresholds of manifest astigmatism (> or = 1.5, > or = 1.75, and > or = 2 D) considering as a true positive case an astigmatism > or = 2 D under cycloplegic condition (measured by retinoscopy, on table, or hand held refractor). RESULTS: The 95% limits of agreement between two repeated manifest cylinder measurements with Retinomax attained levels slightly less than plus or minus 1 D. The 95% limits of agreement for the axis were plus or minus 46 degrees. The comparison of non-cycloplegic measurements in the quick and normal mode showed no significant difference and 95% limits of agreement plus or minus 0.75 D. The mean difference between non-cycloplegic and cycloplegic cylinder values measured by Retinomax reached 0.17 D and was statistically significant. Manifest thresholds of > or = 1.5 D, > or = 1.75 D, > or = 2 D cylinder value diagnosed 2 D of astigmatism under cyclplegia respectively with 71-84%, 59-80%, 51-54% of sensitivity (right eye-left eye) and 90-92%, 95%, 98% of specificity. CONCLUSION: Without cycloplegia, Retinomax is able to measure cylinder power with the same reproducibility as cycloplegic retinoscopy. No significant difference was found in the cylinder values obtained with the quick and the normal modes. Therefore, the quick mode of measurement is recommended as it is more feasible in children. No difference, which is significant from a screening point of view, exists between the non-cycloplegic and the cycloplegic cylinder value (< 0.25 D). Retinomax diagnoses abnormal astigmatism (> or = 2 D) in a non-cycloplegic refractive screening at preschool ages with 51-84% sensitivity rates and 98-90% specificity rates, depending on the chosen threshold of manifest astigmatism. If 2 D of manifest astigmatism is chosen as a positive test, the positive predictive value of the screening reaches 81-84% and the negative predictive value 91-90% (right eye-left eye).  (+info)

Proposed classification for topographic patterns seen after penetrating keratoplasty. (7/358)

AIMS: To create a clinically useful classification for post-keratoplasty corneas based on corneal topography. METHODS: A total of 360 topographic maps obtained with the TMS-1, from 95 eyes that had undergone penetrating keratoplasty (PKP), were reviewed independently by two examiners in a masked fashion, and were categorised according to a proposed classification scheme. RESULTS: A high interobserver agreement (88% in the first categorisation) was achieved. At 12 months post-PKP, a regular astigmatic pattern was observed in 20/85 cases (24%). This was subclassified as oval in three cases (4%), oblate symmetric bow tie in six cases (7%), prolate asymmetric bow tie in six cases (7%), and oblate asymmetric bow tie in five cases (6%). An irregular astigmatic pattern was observed in 61/85 cases (72%), subclassified as prolate irregular in five cases (6%), oblate irregular in four cases (5%), mixed in seven cases (8%), steep/flat in 11 cases (13%), localised steepness in 16 cases (19%), and triple pattern in three cases (4%). Regular astigmatic patterns were associated with significantly higher astigmatism measurements. The surface asymmetry index was significantly lower in the regular astigmatic patterns. CONCLUSIONS: In post-PKP corneas, the prevalence of irregular astigmatism is about double that of regular astigmatism, with a trend for increase of the irregular patterns over time.  (+info)

LASIK for post penetrating keratoplasty astigmatism and myopia. (8/358)

AIMS: To report the results of a series of patients who were treated with LASIK to correct post penetrating keratoplasty ametropia. METHODS: 26 eyes of 24 patients underwent LASIK to correct astigmatism and myopia after corneal transplantation; 14 eyes also received arcuate cuts in the stromal bed at the time of surgery. The mean preoperative spherical equivalent was -5.20D and the mean preoperative astigmatism was 8.67D. RESULTS: The results of 25 eyes are reported. The mean 1 month values for spherical equivalent and astigmatism were -0.24D and 2.48D respectively. 18 eyes have been followed up for 6 months or more. The final follow up results for these eyes are -1.91D and 2.92D for spherical equivalent and astigmatism. The patients undergoing arcuate cuts were less myopic but had greater astigmatism than those not. The patients receiving arcuate cuts had a greater target induced astigmatism, surgically induced astigmatism, and astigmatism correction index than those eyes that did not. One eye suffered a surgical complication. No eyes lost more than one line of BSCVA and all eyes gained between 0 and 6 lines UCVA. CONCLUSIONS: LASIK after penetrating keratoplasty is a relatively safe and effective procedure. It reduces both the spherical error and the cylindrical component of the ametropia. Correction of high astigmatism may be augmented by performing arcuate cuts in the stromal bed.  (+info)

Astigmatism is a common eye condition that occurs when the cornea or lens has an irregular shape, causing blurred or distorted vision. The cornea and lens are typically smooth and curved uniformly in all directions, allowing light to focus clearly on the retina. However, if the cornea or lens is not smoothly curved and has a steeper curve in one direction than the other, it causes light to focus unevenly on the retina, leading to astigmatism.

Astigmatism can cause blurred vision at all distances, as well as eye strain, headaches, and fatigue. It is often present from birth and can be hereditary, but it can also develop later in life due to eye injuries or surgery. Astigmatism can be corrected with glasses, contact lenses, or refractive surgery such as LASIK.

Ocular refraction is a medical term that refers to the bending of light as it passes through the optical media of the eye, including the cornea and lens. This process allows the eye to focus light onto the retina, creating a clear image. The refractive power of the eye is determined by the curvature and transparency of these structures.

In a normal eye, light rays are bent or refracted in such a way that they converge at a single point on the retina, producing a sharp and focused image. However, if the curvature of the cornea or lens is too steep or too flat, the light rays may not converge properly, resulting in a refractive error such as myopia (nearsightedness), hyperopia (farsightedness), or astigmatism.

Ocular refraction can be measured using a variety of techniques, including retinoscopy, automated refraction, and subjective refraction. These measurements are used to determine the appropriate prescription for corrective lenses such as eyeglasses or contact lenses. In some cases, ocular refractive errors may be corrected surgically through procedures such as LASIK or PRK.

Corneal topography is a non-invasive medical imaging technique used to create a detailed map of the surface curvature of the cornea, which is the clear, dome-shaped surface at the front of the eye. This procedure provides valuable information about the shape and condition of the cornea, helping eye care professionals assess various eye conditions such as astigmatism, keratoconus, and other corneal abnormalities. It can also be used in contact lens fitting, refractive surgery planning, and post-surgical evaluation.

Refractive errors are a group of vision conditions that include nearsightedness (myopia), farsightedness (hyperopia), astigmatism, and presbyopia. These conditions occur when the shape of the eye prevents light from focusing directly on the retina, causing blurred or distorted vision.

Myopia is a condition where distant objects appear blurry while close-up objects are clear. This occurs when the eye is too long or the cornea is too curved, causing light to focus in front of the retina instead of directly on it.

Hyperopia, on the other hand, is a condition where close-up objects appear blurry while distant objects are clear. This happens when the eye is too short or the cornea is not curved enough, causing light to focus behind the retina.

Astigmatism is a condition that causes blurred vision at all distances due to an irregularly shaped cornea or lens.

Presbyopia is a natural aging process that affects everyone as they get older, usually around the age of 40. It causes difficulty focusing on close-up objects and can be corrected with reading glasses, bifocals, or progressive lenses.

Refractive errors can be diagnosed through a comprehensive eye exam and are typically corrected with eyeglasses, contact lenses, or refractive surgery such as LASIK.

Retinoscopy is a diagnostic technique used in optometry and ophthalmology to estimate the refractive error of the eye, or in other words, to determine the prescription for eyeglasses or contact lenses. This procedure involves shining a light into the patient's pupil and observing the reflection off the retina while introducing different lenses in front of the patient's eye. The examiner then uses specific movements and observations to determine the amount and type of refractive error, such as myopia (nearsightedness), hyperopia (farsightedness), astigmatism, or presbyopia. Retinoscopy is a fundamental skill for eye care professionals and helps ensure that patients receive accurate prescriptions for corrective lenses.

Myopia, also known as nearsightedness, is a common refractive error of the eye. It occurs when the eye is either too long or the cornea (the clear front part of the eye) is too curved. As a result, light rays focus in front of the retina instead of directly on it, causing distant objects to appear blurry while close objects remain clear.

Myopia typically develops during childhood and can progress gradually or rapidly until early adulthood. It can be corrected with glasses, contact lenses, or refractive surgery such as LASIK. Regular eye examinations are essential for people with myopia to monitor any changes in their prescription and ensure proper correction.

While myopia is generally not a serious condition, high levels of nearsightedness can increase the risk of certain eye diseases, including cataracts, glaucoma, retinal detachment, and myopic degeneration. Therefore, it's crucial to manage myopia effectively and maintain regular follow-ups with an eye care professional.

Hyperopia, also known as farsightedness, is a refractive error in which the eye does not focus light directly on the retina when looking at a distant object. Instead, light is focused behind the retina, causing close-up objects to appear blurry. This condition usually results from the eyeball being too short or the cornea having too little curvature. It can be corrected with eyeglasses, contact lenses, or refractive surgery.

Visual acuity is a measure of the sharpness or clarity of vision. It is usually tested by reading an eye chart from a specific distance, such as 20 feet (6 meters). The standard eye chart used for this purpose is called the Snellen chart, which contains rows of letters that decrease in size as you read down the chart.

Visual acuity is typically expressed as a fraction, with the numerator representing the testing distance and the denominator indicating the smallest line of type that can be read clearly. For example, if a person can read the line on the eye chart that corresponds to a visual acuity of 20/20, it means they have normal vision at 20 feet. If their visual acuity is 20/40, it means they must be as close as 20 feet to see what someone with normal vision can see at 40 feet.

It's important to note that visual acuity is just one aspect of overall vision and does not necessarily reflect other important factors such as peripheral vision, depth perception, color vision, or contrast sensitivity.

Penetrating keratoplasty (PK) is a type of corneal transplant surgery where the entire thickness of the host's damaged or diseased cornea is removed and replaced with a similar full-thickness portion of a healthy donor's cornea. The procedure aims to restore visual function, alleviate pain, and improve the structural integrity of the eye. It is typically performed for conditions such as severe keratoconus, corneal scarring, or corneal ulcers that cannot be treated with other, less invasive methods. Following the surgery, patients may require extended recovery time and rigorous postoperative care to minimize the risk of complications and ensure optimal visual outcomes.

Suture techniques refer to the various methods used by surgeons to sew or stitch together tissues in the body after an injury, trauma, or surgical incision. The main goal of suturing is to approximate and hold the edges of the wound together, allowing for proper healing and minimizing scar formation.

There are several types of suture techniques, including:

1. Simple Interrupted Suture: This is one of the most basic suture techniques where the needle is passed through the tissue at a right angle, creating a loop that is then tightened to approximate the wound edges. Multiple stitches are placed along the length of the incision or wound.
2. Continuous Locking Suture: In this technique, the needle is passed continuously through the tissue in a zigzag pattern, with each stitch locking into the previous one. This creates a continuous line of sutures that provides strong tension and support to the wound edges.
3. Running Suture: Similar to the continuous locking suture, this technique involves passing the needle continuously through the tissue in a straight line. However, instead of locking each stitch, the needle is simply passed through the previous loop before being tightened. This creates a smooth and uninterrupted line of sutures that can be easily removed after healing.
4. Horizontal Mattress Suture: In this technique, two parallel stitches are placed horizontally across the wound edges, creating a "mattress" effect that provides additional support and tension to the wound. This is particularly useful in deep or irregularly shaped wounds.
5. Vertical Mattress Suture: Similar to the horizontal mattress suture, this technique involves placing two parallel stitches vertically across the wound edges. This creates a more pronounced "mattress" effect that can help reduce tension and minimize scarring.
6. Subcuticular Suture: In this technique, the needle is passed just below the surface of the skin, creating a smooth and barely visible line of sutures. This is particularly useful in cosmetic surgery or areas where minimizing scarring is important.

The choice of suture technique depends on various factors such as the location and size of the wound, the type of tissue involved, and the patient's individual needs and preferences. Proper suture placement and tension are crucial for optimal healing and aesthetic outcomes.

Anisometropia is a medical term that refers to a condition where there is a significant difference in the refractive power between the two eyes. In other words, one eye has a significantly different optical prescription compared to the other eye. This condition can cause issues with binocular vision and depth perception, and can sometimes lead to amblyopia (lazy eye) if not corrected early in life. It is typically diagnosed through a comprehensive eye examination and can be corrected with glasses or contact lenses.

The cornea is the clear, dome-shaped surface at the front of the eye. It plays a crucial role in focusing vision. The cornea protects the eye from harmful particles and microorganisms, and it also serves as a barrier against UV light. Its transparency allows light to pass through and get focused onto the retina. The cornea does not contain blood vessels, so it relies on tears and the fluid inside the eye (aqueous humor) for nutrition and oxygen. Any damage or disease that affects its clarity and shape can significantly impact vision and potentially lead to blindness if left untreated.

Cataract extraction is a surgical procedure that involves removing the cloudy lens (cataract) from the eye. This procedure is typically performed to restore vision impairment caused by cataracts and improve overall quality of life. There are two primary methods for cataract extraction:

1. Phacoemulsification: This is the most common method used today. It involves making a small incision in the front part of the eye (cornea), inserting an ultrasonic probe to break up the cloudy lens into tiny pieces, and then removing those pieces with suction. After removing the cataract, an artificial intraocular lens (IOL) is inserted to replace the natural lens and help focus light onto the retina.

2. Extracapsular Cataract Extraction: In this method, a larger incision is made on the side of the cornea, allowing the surgeon to remove the cloudy lens in one piece without breaking it up. The back part of the lens capsule is left intact to support the IOL. This technique is less common and typically reserved for more advanced cataracts or when phacoemulsification cannot be performed.

Recovery from cataract extraction usually involves using eye drops to prevent infection and inflammation, as well as protecting the eye with a shield or glasses during sleep for a few weeks after surgery. Most people experience improved vision within a few days to a week following the procedure.

Corneal diseases are a group of disorders that affect the cornea, which is the clear, dome-shaped surface at the front of the eye. The cornea plays an important role in focusing vision, and any damage or disease can cause significant visual impairment or loss. Some common types of corneal diseases include:

1. Keratoconus: A progressive disorder in which the cornea thins and bulges outward into a cone shape, causing distorted vision.
2. Fuchs' dystrophy: A genetic disorder that affects the inner layer of the cornea called the endothelium, leading to swelling, cloudiness, and decreased vision.
3. Dry eye syndrome: A condition in which the eyes do not produce enough tears or the tears evaporate too quickly, causing discomfort, redness, and blurred vision.
4. Corneal ulcers: Open sores on the cornea that can be caused by infection, trauma, or other factors.
5. Herpes simplex keratitis: A viral infection of the cornea that can cause recurrent episodes of inflammation, scarring, and vision loss.
6. Corneal dystrophies: Inherited disorders that affect the structure and clarity of the cornea, leading to visual impairment or blindness.
7. Bullous keratopathy: A condition in which the endothelium fails to pump fluid out of the cornea, causing it to swell and form blisters.
8. Corneal trauma: Injury to the cornea caused by foreign objects, chemicals, or other factors that can lead to scarring, infection, and vision loss.

Treatment for corneal diseases varies depending on the specific condition and severity of the disease. Options may include eyedrops, medications, laser surgery, corneal transplantation, or other treatments.

Keratoconus is a degenerative non-inflammatory disorder of the eye, primarily affecting the cornea. It is characterized by a progressive thinning and steepening of the central or paracentral cornea, causing it to assume a conical shape. This results in irregular astigmatism, myopia, and scattering of light leading to blurred vision, visual distortions, and sensitivity to glare. The exact cause of keratoconus is unknown, but it may be associated with genetics, eye rubbing, and certain medical conditions. It typically starts in the teenage years and progresses into the third or fourth decade of life. Treatment options include glasses, contact lenses, cross-linking, and corneal transplantation in advanced cases.

Intraocular lens (IOL) implantation is a surgical procedure that involves placing a small artificial lens inside the eye to replace the natural lens that has been removed. This procedure is typically performed during cataract surgery, where the cloudy natural lens is removed and replaced with an IOL to restore clear vision.

During the procedure, a small incision is made in the eye, and the cloudy lens is broken up and removed using ultrasound waves or laser energy. Then, the folded IOL is inserted through the same incision and positioned in the correct place inside the eye. Once in place, the IOL unfolds and is secured into position.

There are several types of IOLs available, including monofocal, multifocal, toric, and accommodating lenses. Monofocal lenses provide clear vision at one distance, while multifocal lenses offer clear vision at multiple distances. Toric lenses correct astigmatism, and accommodating lenses can change shape to focus on objects at different distances.

Overall, intraocular lens implantation is a safe and effective procedure that can help restore clear vision in patients with cataracts or other eye conditions that require the removal of the natural lens.

Eyeglasses are a medical device used to correct vision problems. Also known as spectacles, they consist of frames that hold one or more lenses through which a person looks to see clearly. The lenses may be made of glass or plastic and are designed to compensate for various visual impairments such as nearsightedness, farsightedness, astigmatism, or presbyopia. Eyeglasses can be custom-made to fit an individual's face and prescription, and they come in a variety of styles, colors, and materials. Some people wear eyeglasses all the time, while others may only need to wear them for certain activities such as reading or driving.

Intraocular lenses (IOLs) are artificial lens implants that are placed inside the eye during ophthalmic surgery, such as cataract removal. These lenses are designed to replace the natural lens of the eye that has become clouded or damaged, thereby restoring vision impairment caused by cataracts or other conditions.

There are several types of intraocular lenses available, including monofocal, multifocal, toric, and accommodative lenses. Monofocal IOLs provide clear vision at a single fixed distance, while multifocal IOLs offer clear vision at multiple distances. Toric IOLs are designed to correct astigmatism, and accommodative IOLs can change shape and position within the eye to allow for a range of vision.

The selection of the appropriate type of intraocular lens depends on various factors, including the patient's individual visual needs, lifestyle, and ocular health. The implantation procedure is typically performed on an outpatient basis and involves minimal discomfort or recovery time. Overall, intraocular lenses have become a safe and effective treatment option for patients with vision impairment due to cataracts or other eye conditions.

An excimer laser is a type of laser that is used in various medical procedures, particularly in ophthalmology and dermatology. The term "excimer" is derived from "excited dimer," which refers to a short-lived molecule formed when two atoms combine in an excited state.

Excimer lasers emit light at a specific wavelength that is determined by the type of gas used in the laser. In medical applications, excimer lasers typically use noble gases such as argon, krypton, or xenon, combined with halogens such as fluorine or chlorine. The most commonly used excimer laser in medical procedures is the excimer laser that uses a mixture of argon and fluoride gas to produce light at a wavelength of 193 nanometers (nm).

In ophthalmology, excimer lasers are primarily used for refractive surgery, such as LASIK and PRK, to correct vision problems like myopia, hyperopia, and astigmatism. The laser works by vaporizing tiny amounts of tissue from the cornea, reshaping its curvature to improve the way light is focused onto the retina.

In dermatology, excimer lasers are used for various skin conditions, including psoriasis, vitiligo, and atopic dermatitis. The laser works by emitting high-energy ultraviolet (UV) light that selectively targets and destroys the abnormal cells responsible for these conditions while leaving surrounding healthy tissue intact.

Excimer lasers are known for their precision, accuracy, and minimal side effects, making them a popular choice in medical procedures where fine detail and tissue preservation are critical.

Laser In Situ Keratomileusis (LASIK) is a type of refractive surgery used to correct vision issues such as myopia (nearsightedness), hyperopia (farsightedness), and astigmatism. The procedure involves reshaping the cornea, which is the clear, dome-shaped surface at the front of the eye, using an excimer laser.

In LASIK, a thin flap is created on the surface of the cornea using a femtosecond or microkeratome laser. The flap is then lifted, and the excimer laser is used to reshape the underlying tissue. After the reshaping is complete, the flap is replaced, allowing for quicker healing and visual recovery compared to other refractive surgery procedures.

LASIK is an outpatient procedure that typically takes about 30 minutes or less per eye. Most people can expect to see improved vision within a few days of the procedure, although it may take several weeks for vision to fully stabilize. LASIK has a high success rate and is generally considered safe when performed by a qualified surgeon. However, as with any surgical procedure, there are risks involved, including dry eye, infection, and visual complications such as glare or halos around lights.

Corneal wavefront aberration is a measurement of the irregularities in the shape and curvature of the cornea, which can affect the way light enters the eye and is focused on the retina. A wavefront aberration test uses a device to measure the refraction of light as it passes through the cornea and calculates the degree of any distortions or irregularities in the wavefront of the light. This information can be used to guide treatment decisions, such as the prescription for eyeglasses or contact lenses, or the planning of a surgical procedure to correct the aberration.

Corneal wavefront aberrations can be classified into two types: low-order and high-order aberrations. Low-order aberrations include myopia (nearsightedness), hyperopia (farsightedness), and astigmatism, which are common refractive errors that can be easily corrected with glasses or contact lenses. High-order aberrations are more complex irregularities in the wavefront of light that cannot be fully corrected with traditional eyeglasses or contact lenses. These may include coma, trefoil, and spherical aberration, among others.

High-order corneal wavefront aberrations can affect visual quality, causing symptoms such as glare, halos around lights, and decreased contrast sensitivity. They are often associated with conditions that cause changes in the shape of the cornea, such as keratoconus or corneal surgery. In some cases, high-order aberrations can be corrected with specialized contact lenses or refractive surgery procedures such as wavefront-guided LASIK or PRK.

Aberrometry is a medical diagnostic technique used to measure the amount and type of aberration or distortion in the optical system of the eye. It is often used to evaluate the quality of vision, particularly in cases where traditional methods of measuring visual acuity are not sufficient.

During an aberrometry test, the patient looks into a specialized instrument called a wavefront sensor while a series of light patterns are projected onto the retina. The sensor then measures how the light is distorted as it passes through the eye's optical system, including the cornea and lens. This information is used to create a detailed map of the eye's aberrations, which can help doctors identify any irregularities that may be contributing to visual symptoms such as blurred vision, glare, or halos around lights.

Aberrometry is often used in conjunction with other diagnostic tests to evaluate patients who are considering refractive surgery, such as LASIK or PRK. By identifying any abnormalities in the eye's optical system, doctors can determine whether a patient is a good candidate for surgery and make more informed decisions about how to proceed with treatment.

Subepithelial laser-assisted keratectomy (SELAK) is a type of refractive surgery used to correct vision problems such as myopia (nearsightedness), hyperopia (farsightedness), and astigmatism. In this procedure, a precise and controlled laser beam is used to remove a thin layer of tissue from the cornea, specifically from the subepithelial region, which lies just beneath the surface epithelium.

The goal of SELAK is to reshape the cornea and improve its focusing power, thereby reducing or eliminating the need for corrective lenses such as glasses or contact lenses. The laser-assisted technique allows for a high degree of precision and customization, enabling the surgeon to tailor the procedure to each patient's individual needs.

It is important to note that while SELAK can be an effective treatment option for many people, it may not be suitable for everyone. A thorough eye examination and consultation with an eye care professional are necessary to determine whether this procedure is appropriate for a particular individual.

Pseudophakia is a medical term that refers to the condition where a person's natural lens in the eye has been replaced with an artificial one. This procedure is typically performed during cataract surgery, where the cloudy, natural lens is removed and replaced with a clear, artificial lens to improve vision. The prefix "pseudo" means false or fake, and "phakia" refers to the natural lens of the eye, hence the term "Pseudophakia" implies a false or artificial lens.

Vision screening is a quick and cost-effective method used to identify individuals who are at risk of vision problems or eye diseases. It is not a comprehensive eye examination, but rather an initial evaluation that helps to determine if a further, more in-depth examination by an eye care professional is needed. Vision screenings typically involve tests for visual acuity, distance and near vision, color perception, depth perception, and alignment of the eyes. The goal of vision screening is to detect potential vision issues early on, so that they can be treated promptly and effectively, thereby preventing or minimizing any negative impact on a person's overall vision and quality of life.

In medical terms, sutures are specialized surgical threads made from various materials such as absorbable synthetic or natural fibers, or non-absorbable materials like nylon or silk. They are used to approximate and hold together the edges of a wound or incision in the skin or other tissues during the healing process. Sutures come in different sizes, types, and shapes, each designed for specific uses and techniques depending on the location and type of tissue being sutured. Properly placed sutures help to promote optimal healing, minimize scarring, and reduce the risk of infection or other complications.

Refractive surgical procedures are a type of ophthalmic surgery aimed at improving the refractive state of the eye and reducing or eliminating the need for corrective eyewear. These procedures reshape the cornea or alter the lens of the eye to correct nearsightedness (myopia), farsightedness (hyperopia), presbyopia, or astigmatism.

Examples of refractive surgical procedures include:

1. Laser-assisted in situ keratomileusis (LASIK): A laser is used to create a thin flap in the cornea, which is then lifted to allow reshaping of the underlying tissue with another laser. The flap is replaced, and the procedure is completed.
2. Photorefractive keratectomy (PRK): This procedure involves removing the outer layer of the cornea (epithelium) and using a laser to reshape the underlying tissue. A bandage contact lens is placed over the eye to protect it during healing.
3. LASEK (laser-assisted subepithelial keratomileusis): Similar to LASIK, but instead of creating a flap, the epithelium is loosened with an alcohol solution and moved aside. The laser treatment is applied, and the epithelium is replaced.
4. Small Incision Lenticule Extraction (SMILE): A femtosecond laser creates a small lenticule within the cornea, which is then removed through a tiny incision. This procedure reshapes the cornea to correct refractive errors.
5. Refractive lens exchange (RLE): The eye's natural lens is removed and replaced with an artificial intraocular lens (IOL) to correct refractive errors, similar to cataract surgery.
6. Implantable contact lenses: A thin, foldable lens is placed between the iris and the natural lens or behind the iris to improve the eye's focusing power.

These procedures are typically performed on an outpatient basis and may require topical anesthesia (eye drops) or local anesthesia. Potential risks and complications include infection, dry eye, visual disturbances, and changes in night vision. It is essential to discuss these potential risks with your ophthalmologist before deciding on a refractive surgery procedure.

Radial Keratotomy (RK) is a type of refractive surgery used to correct vision problems such as nearsightedness and astigmatism. The procedure involves making small, precise incisions in the cornea in a radial pattern, like the spokes of a wheel. These incisions cause the cornea to change shape, which can help to improve the way that light is focused onto the retina and reduce the need for corrective lenses.

During the procedure, the surgeon uses a specialized blade or laser to make the incisions in the cornea. The incisions are typically made at the periphery of the cornea, leaving the central portion of the cornea untouched. This helps to preserve the strength and stability of the cornea while still allowing it to change shape enough to improve vision.

Radial keratotomy was first developed in the 1970s and was widely used in the 1980s and 1990s. However, it has largely been replaced by newer procedures such as LASIK and PRK, which are considered to be safer and more effective. RK is still occasionally performed in cases where other procedures are not an option or when a patient prefers this type of surgery.

It's important to note that any surgical procedure carries risks, including infection, scarring, and changes in vision. Patients considering radial keratotomy should discuss the potential benefits and risks with their eye care provider before making a decision.

Corneal surgery, laser refers to a type of surgical procedure performed on the cornea (the clear, dome-shaped surface at the front of the eye) using a laser. The most common type of laser used in corneal surgery is an excimer laser, which can be used to reshape the cornea and correct refractive errors such as nearsightedness, farsightedness, and astigmatism. This procedure is commonly known as LASIK (Laser-Assisted In Situ Keratomileusis).

Another type of laser corneal surgery is PRK (Photorefractive Keratectomy) which uses a laser to reshape the surface of the cornea. This procedure is typically used for patients who have thin corneas or other conditions that make them ineligible for LASIK.

Additionally, there are other types of laser corneal surgeries such as LASEK (Laser Epithelial Keratomileusis), Epi-LASIK (Epithelial Laser-Assisted Keratomileusis) and SBK (Sub Bowman's Keratomileusis) which are variations of the above procedures.

It is important to note that, as with any surgical procedure, laser corneal surgery has risks and potential complications, including dry eye, infection, and visual symptoms such as glare or halos around lights. It is essential for patients to have a thorough examination and consultation with an ophthalmologist before deciding if laser corneal surgery is the right choice for them.

Photorefractive Keratectomy (PRK) is a type of refractive surgery used to correct vision issues such as nearsightedness, farsightedness, and astigmatism. It works by reshaping the cornea using a laser, which alters how light enters the eye and focuses on the retina.

In PRK, the surgeon removes the thin outer layer of the cornea (epithelium) with an alcohol solution or a blunt surgical instrument before using the laser to reshape the underlying stromal layer. The epithelium then grows back during the healing process, which can take several days.

Compared to LASIK (another type of refractive surgery), PRK has a longer recovery time and may cause more discomfort in the first few days after surgery. However, it is an option for people who are not good candidates for LASIK due to thin corneas or other eye conditions.

It's important to note that while refractive surgeries like PRK can significantly improve vision and reduce dependence on glasses or contact lenses, they may not completely eliminate the need for corrective eyewear in all cases. Additionally, as with any surgical procedure, there are potential risks and complications associated with PRK, including infection, dry eye, and visual disturbances such as glare or halos around lights.

In the context of ophthalmology and optometry, glare refers to a visual sensation caused by excessive brightness or contrast that interferes with the ability to see comfortably or clearly. It can be caused by direct or reflected light sources that enter the eye and scatter within the eye or on the surface of the eye, reducing contrast and visibility. Glare can lead to discomfort, disability, or both, and it can significantly impact visual performance in various activities such as driving, reading, and using digital devices. There are different types of glare, including direct glare, reflected glare, and veiling glare, each with its own characteristics and effects on vision.

Phacoemulsification is a surgical procedure used in cataract removal. It involves using an ultrasonic device to emulsify (break up) the cloudy lens (cataract) into small pieces, which are then aspirated or sucked out through a small incision. This procedure allows for smaller incisions and faster recovery times compared to traditional cataract surgery methods. After the cataract is removed, an artificial intraocular lens (IOL) is typically implanted to replace the natural lens and restore vision.

Biometry, also known as biometrics, is the scientific study of measurements and statistical analysis of living organisms. In a medical context, biometry is often used to refer to the measurement and analysis of physical characteristics or features of the human body, such as height, weight, blood pressure, heart rate, and other physiological variables. These measurements can be used for a variety of purposes, including diagnosis, treatment planning, monitoring disease progression, and research.

In addition to physical measurements, biometry may also refer to the use of statistical methods to analyze biological data, such as genetic information or medical images. This type of analysis can help researchers and clinicians identify patterns and trends in large datasets, and make predictions about health outcomes or treatment responses.

Overall, biometry is an important tool in modern medicine, as it allows healthcare professionals to make more informed decisions based on data and evidence.

Amblyopia is a medical condition that affects the visual system, specifically the way the brain and eyes work together. It is often referred to as "lazy eye" and is characterized by reduced vision in one or both eyes that is not correctable with glasses or contact lenses alone. This occurs because the brain favors one eye over the other, causing the weaker eye to become neglected and underdeveloped.

Amblyopia can result from various conditions such as strabismus (eye misalignment), anisometropia (significant difference in prescription between the two eyes), or deprivation (such as a cataract that blocks light from entering the eye). Treatment for amblyopia typically involves correcting any underlying refractive errors, patching or blurring the stronger eye to force the weaker eye to work, and/or vision therapy. Early intervention is crucial to achieve optimal visual outcomes.

Corneal transplantation, also known as keratoplasty, is a surgical procedure in which all or part of a damaged or diseased cornea is replaced with healthy corneal tissue from a deceased donor. The cornea is the clear, dome-shaped surface at the front of the eye that plays an important role in focusing vision. When it becomes cloudy or misshapen due to injury, infection, or inherited conditions, vision can become significantly impaired.

During the procedure, the surgeon carefully removes a circular section of the damaged cornea and replaces it with a similarly sized piece of donor tissue. The new cornea is then stitched into place using very fine sutures that are typically removed several months after surgery.

Corneal transplantation has a high success rate, with more than 90% of procedures resulting in improved vision. However, as with any surgical procedure, there are risks involved, including infection, rejection of the donor tissue, and bleeding. Regular follow-up care is essential to monitor for any signs of complications and ensure proper healing.

I believe there may be some confusion in your question. "Nylons" is a common term for a type of synthetic fiber often used in clothing, hosiery, and other textile applications. It is not a medical term or concept. If you have any questions related to medical terminology or concepts, I would be happy to try and help clarify!

Ocular albinism is a type of albinism that primarily affects the eyes. It is a genetic disorder characterized by the reduction or absence of melanin, the pigment responsible for coloring the skin, hair, and eyes. In ocular albinism, melanin production is deficient in the eyes, leading to various eye abnormalities.

The main features of ocular albinism include:

1. Nystagmus: Rapid, involuntary back-and-forth movement of the eyes.
2. Iris transillumination: The iris appears translucent due to the lack of pigment, allowing light to pass through easily. This can be observed using a light source shone into the eye.
3. Foveal hypoplasia: Underdevelopment or absence of the fovea, a small pit in the retina responsible for sharp, central vision.
4. Photophobia: Increased sensitivity to light due to the lack of pigment in the eyes.
5. Strabismus: Misalignment of the eyes, which can result in double vision or lazy eye.
6. Reduced visual acuity: Decreased ability to see clearly, even with corrective lenses.

Ocular albinism is typically inherited as an X-linked recessive trait, meaning it primarily affects males, while females can be carriers of the condition. However, there are also autosomal recessive forms of ocular albinism that can affect both males and females equally. Treatment for ocular albinism usually involves managing symptoms with corrective lenses, low-vision aids, and vision therapy to improve visual skills.

Eyelids are the thin folds of skin that cover and protect the front surface (cornea) of the eye when closed. They are composed of several layers, including the skin, muscle, connective tissue, and a mucous membrane called the conjunctiva. The upper and lower eyelids meet at the outer corner of the eye (lateral canthus) and the inner corner of the eye (medial canthus).

The main function of the eyelids is to protect the eye from foreign particles, light, and trauma. They also help to distribute tears evenly over the surface of the eye through blinking, which helps to keep the eye moist and healthy. Additionally, the eyelids play a role in facial expressions and non-verbal communication.

A pterygium is a benign, triangular-shaped growth of the conjunctiva (the clear, thin tissue that covers the white part of the eye) that extends onto the cornea (the clear front "window" of the eye). It typically forms on the side of the eye closest to the nose and can sometimes grow large enough to interfere with vision.

Pterygium is believed to be caused by a combination of environmental factors, such as prolonged exposure to sunlight, wind, and dust, and genetic predisposition. Chronic inflammation and dry eye syndrome may also contribute to its development.

While pterygium is not cancerous, it can cause discomfort, redness, and irritation. In some cases, surgery may be recommended to remove the growth, especially if it affects vision or becomes cosmetically bothersome. However, recurrence of pterygium after surgery is relatively common.

Phakic Intraocular Lenses (PIOLs) are a type of surgical implant used in refractive eye surgery to correct vision problems such as myopia (nearsightedness), hyperopia (farsightedness), and astigmatism. These lenses are placed inside the eye, specifically between the cornea and the natural lens (crystalline lens) of the eye, without removing the natural lens. This is why they are called "phakic," which means the natural lens remains in place.

PIOLs can provide an alternative to other refractive surgeries like LASIK or PRK, particularly for individuals with high levels of refractive error who may not be suitable candidates for those procedures. The procedure to implant a phakic intraocular lens is typically performed on an outpatient basis and takes only a few minutes.

There are two main types of PIOLs: anterior chamber phakic lenses, which are placed in front of the iris, and posterior chamber phakic lenses, which are placed behind the iris but in front of the natural lens. Both types of lenses have their own advantages and disadvantages, and the choice between them depends on various factors such as the patient's eye anatomy and the specific type and degree of refractive error.

It is important to note that, like any surgical procedure, there are potential risks associated with PIOL implantation, including infection, increased intraocular pressure, cataract formation, and changes in vision. Therefore, a thorough evaluation by an eye care professional is necessary before deciding if this type of surgery is appropriate for an individual patient.

Vision tests are a series of procedures used to assess various aspects of the visual system, including visual acuity, accommodation, convergence, divergence, stereopsis, color vision, and peripheral vision. These tests help healthcare professionals diagnose and manage vision disorders, such as nearsightedness, farsightedness, astigmatism, amblyopia, strabismus, and eye diseases like glaucoma, cataracts, and macular degeneration. Common vision tests include:

1. Visual acuity test (Snellen chart or letter chart): Measures the sharpness of a person's vision at different distances.
2. Refraction test: Determines the correct lens prescription for glasses or contact lenses by assessing how light is bent as it passes through the eye.
3. Color vision test: Evaluates the ability to distinguish between different colors and color combinations, often using pseudoisochromatic plates or Ishihara tests.
4. Stereopsis test: Assesses depth perception and binocular vision by presenting separate images to each eye that, when combined, create a three-dimensional effect.
5. Cover test: Examines eye alignment and the presence of strabismus (crossed eyes or turned eyes) by covering and uncovering each eye while observing eye movements.
6. Ocular motility test: Assesses the ability to move the eyes in various directions and coordinate both eyes during tracking and convergence/divergence movements.
7. Accommodation test: Evaluates the ability to focus on objects at different distances by using lenses, prisms, or dynamic retinoscopy.
8. Pupillary response test: Examines the size and reaction of the pupils to light and near objects.
9. Visual field test: Measures the peripheral (side) vision using automated perimetry or manual confrontation techniques.
10. Slit-lamp examination: Inspects the structures of the front part of the eye, such as the cornea, iris, lens, and anterior chamber, using a specialized microscope.

These tests are typically performed by optometrists, ophthalmologists, or other vision care professionals during routine eye examinations or when visual symptoms are present.

Ocular accommodation is the process by which the eye changes optical power to maintain a clear image or focus on an object as its distance varies. This is primarily achieved by the lens of the eye changing shape through the action of the ciliary muscles inside the eye. When you look at something far away, the lens becomes flatter, and when you look at something close up, the lens thickens. This ability to adjust focus allows for clear vision at different distances.

Ophthalmology is a branch of medicine that deals with the diagnosis, treatment, and prevention of diseases and disorders of the eye and visual system. It is a surgical specialty, and ophthalmologists are medical doctors who complete additional years of training to become experts in eye care. They are qualified to perform eye exams, diagnose and treat eye diseases, prescribe glasses and contact lenses, and perform eye surgery. Some subspecialties within ophthalmology include cornea and external disease, glaucoma, neuro-ophthalmology, pediatric ophthalmology, retina and vitreous, and oculoplastics.

Retinopathy of Prematurity (ROP) is a potentially sight-threatening proliferative retinal vascular disorder that primarily affects prematurely born infants, particularly those with low birth weight and/or young gestational age. It is characterized by the abnormal growth and development of retinal blood vessels due to disturbances in the oxygen supply and metabolic demands during critical phases of fetal development.

The condition can be classified into various stages (1-5) based on its severity, with stages 4 and 5 being more severe forms that may lead to retinal detachment and blindness if left untreated. The pathogenesis of ROP involves an initial phase of vessel loss and regression in the central retina, followed by a secondary phase of abnormal neovascularization, which can cause fibrosis, traction, and ultimately, retinal detachment.

ROP is typically managed with a multidisciplinary approach involving ophthalmologists, neonatologists, and pediatricians. Treatment options include laser photocoagulation, cryotherapy, intravitreal anti-VEGF injections, or even surgical interventions to prevent retinal detachment and preserve vision. Regular screening examinations are crucial for early detection and timely management of ROP in at-risk infants.

Mydriatics are medications that cause mydriasis, which is the dilation of the pupil. These drugs work by blocking the action of the muscarinic receptors in the iris, leading to relaxation of the circular muscle and constriction of the radial muscle, resulting in pupil dilation. Mydriatics are often used in eye examinations to facilitate examination of the interior structures of the eye. Commonly used mydriatic agents include tropicamide, phenylephrine, and cyclopentolate. It is important to note that mydriatics can have side effects such as blurred vision, photophobia, and accommodation difficulties, so patients should be advised accordingly.

Corneal pachymetry is a medical measurement of the thickness of the cornea, which is the clear, dome-shaped surface at the front of the eye. This measurement is typically taken using a specialized instrument called a pachymeter. The procedure is quick, painless, and non-invasive.

Corneal pachymetry is an essential test in optometry and ophthalmology for various reasons. For instance, it helps assess the overall health of the cornea, identify potential abnormalities or diseases, and determine the correct intraocular lens power during cataract surgery. Additionally, corneal thickness is a crucial factor in determining a person's risk for developing glaucoma and monitoring the progression of the disease.

In some cases, such as with contact lens fitting, corneal pachymetry can help ensure proper fit and minimize potential complications. Overall, corneal pachymetry is an essential diagnostic tool in eye care that provides valuable information for maintaining eye health and ensuring appropriate treatment.

In the context of medical terminology, "lenses" generally refers to optical lenses used in various medical devices and instruments. These lenses are typically made of glass or plastic and are designed to refract (bend) light in specific ways to help magnify, focus, or redirect images. Here are some examples:

1. In ophthalmology and optometry, lenses are used in eyeglasses, contact lenses, and ophthalmic instruments to correct vision problems like myopia (nearsightedness), hypermetropia (farsightedness), astigmatism, or presbyopia.
2. In surgical microscopes, lenses are used to provide a magnified and clear view of the operating field during microsurgical procedures like ophthalmic, neurosurgical, or ENT (Ear, Nose, Throat) surgeries.
3. In endoscopes and laparoscopes, lenses are used to transmit light and images from inside the body during minimally invasive surgical procedures.
4. In ophthalmic diagnostic instruments like slit lamps, lenses are used to examine various structures of the eye in detail.

In summary, "lenses" in medical terminology refer to optical components that help manipulate light to aid in diagnosis, treatment, or visual correction.

There are three primary types of astigmatism: myopic astigmatism, hyperopic astigmatism, and mixed astigmatism. Cases can be ... Astigmatism was first reported by Thomas Young in 1801. Although astigmatism may be asymptomatic, higher degrees of astigmatism ... The dictionary definition of astigmatism at Wiktionary Media related to Astigmatism (eye) at Wikimedia Commons Astigmatism at ... Simple myopic astigmatism - first focal line is in front of the retina, while the second is on the retina. Compound astigmatism ...
In this case, astigmatism is observed even for rays from on-axis object points. This form of astigmatism is extremely important ... Astigmatism is quite common. Studies have shown that about one in three people suffers from it. The prevalence of astigmatism ... Astigmatism causes difficulties in seeing fine detail. Astigmatism can be often corrected by glasses with a lens that has ... Although a person may not notice mild astigmatism, higher amounts of astigmatism may cause blurry vision, squinting, asthenopia ...
... and as a result can correct for astigmatism. Another way is by using a rigid gas permeable lens; since most astigmatism is ... "Astigmatism". www.aoa.org. Retrieved 6 August 2020. "Advantages and Disadvantages of Various Types of Contact Lenses". www.aoa. ... This means that a spherical rigid contact lens can correct corneal astigmatism. Rigid lenses can also be made as a front-toric ... There are two ways that contact lenses can correct astigmatism. One way is with toric soft lenses that work essentially the ...
The same holds for the errors depending upon the angle of the field of view, w: astigmatism, curvature of field and distortion ... 4) After eliminating the aberration On the axis, coma and astigmatism, the relation for the flatness of the field in the third ... Wide angle lens; necessary corrections are - for astigmatism, curvature of field and distortion; errors of the aperture only ... The most common monochromatic aberrations are: Defocus Spherical aberration Coma Astigmatism Field curvature Image distortion ...
Searle has astigmatism. He often cannot even see where his darts land. 2019: Fourth round (lost to Michael Smith 1-4) 2020: ...
... astigmatism is typically not corrected, as astigmatism is mainly attributable to a deformation of the cornea. Toric IOLs may be ... Underlying regular astigmatism can also be managed by RLE, even beyond the scope of corneal incisional techniques, by toric ... Astigmatism can also be treated with limbal relaxing incisions or an excimer laser procedure. About 40% of Americans have ... If misaligned, preexisting astigmatism may not be corrected completely or may even increase.[citation needed] When standard ...
Waner had an astigmatism; he did not like wearing glasses on the field as it made the ball appear smaller and in focus, but ...
"CRT Projector Astigmatism Adjustments". www.curtpalme.com. "CRT Projector Astigmatism Adjustments". www.curtpalme.com. "CRT ... Projector CRTs may have adjustment rings just like color CRTs to adjust astigmatism, which is flaring of the electron beam ( ... compensating for electron beam defocusing and astigmatism. The fact that the CRT screen is not spherical leads to geometry ...
The system underpins astigmatism analysis approaches developed by the American National Standards Institute (ANSI) Astigmatism ... Morlet, N; D Minassian; J Dart (December 2002). "Astigmatism and the analysis of its surgical correction". British Journal of ... Noel Alpins AM is an Australian ophthalmologist who developed the Alpins method of astigmatism analysis used in refractive, ... "Practical Astigmatism: Planning and Analysis". Retrieved 17 February 2020. "International Society of Refractive Surgery". ...
Jin, Ki Won; Shin, Young Joo; Hyon, Joon Young (2017-03-31). "Effects of chalazia on corneal astigmatism". BMC Ophthalmology. ... typically none-to-mild Increased tearing Heaviness of the eyelid Redness of conjunctiva A large chalazion can cause astigmatism ...
... that case is called general astigmatism. Formulas for an incidence angle θi were derived in Massey and Siegman's 1969 paper. ...
Post operative astigmatism following cataract surgery. Causes of decreased vision after cataract surgery ( < 6/24 ). Surgery ...
This is used for correcting astigmatism. In this context, the term cylinder is based on a mathematical approximation, which is ... Toric lenses are used primarily in eyeglasses, contact lenses and intraocular lenses to correct astigmatism. A torus is the ...
... is a lens used to diagnose and measure astigmatism. American ophthalmologist Edward Jackson revised the Stokes lens ... Ferrer-Altabás, Sara; Micó, Vicente (10 April 2020). "Characterization of a compact low-cost Stokes lens for astigmatism ... Dennett, WS (1885). "The Stokes' Lens for Measuring Astigmatism". Transactions of the American Ophthalmological Society. 4: 106 ... English mathematician and astronomer George Biddell Airy invented the cylindric lens and used it to correct astigmatism. Irish ...
Hodge, Gerald P.; Ravin, James G. (1967-08-01). "EL GRECO: ASTIGMATISM OR CALCULATED DISTORTION". Journal of Pediatric ...
Alpins, Noel; JK Ong; G Stamatelatos (2015). "Corneal topographic astigmatism (CorT) to quantify total corneal astigmatism". ... Another novel use of corneal topographic data is called CorT, which has been shown to quantify refractive astigmatism more ... Alpins, Noel; JK Ong; G Stamatelatos (2012). "New method of quantifying corneal topographic astigmatism that corresponds with ... Biro, A (25 November 2012). "New measurement method quantifies corneal astigmatism". Ocular Surgery News. US edition. Retrieved ...
AK is often used for the correction of high post-keratoplasty astigmatism or post-cataract surgery astigmatism. Limbal relaxing ... It can also be used to treat selected types of astigmatism. It is now generally replaced by laser thermal keratoplasty/laser ... Koch, DD (2006). "Astigmatism analysis: the spectrum of approaches". Journal of Cataract and Refractive Surgery. 32 (12): 1977- ... Alpins, NA (1993). "A new method of analyzing vectors for changes in astigmatism". Journal of Cataract and Refractive Surgery. ...
There may be 'with the rule' astigmatism. Lens may be luxated due to zonular stretching.In rare cases, it might be associated ...
However, if astigmatism is present, the aim of this step is to position the 2 focal lines so as to straddle the retina. This is ... 2) SEARCH FOR Astigmatism The Jackson cross cylinder (JCC) is used in this step. The patient's fixation is directed to a round ... In order to determine if the patient has astigmatism at a particular meridian, the -0.50 JCC is presented at the following axes ... This is used to search for astigmatism. Snellen chart Duochrome test: used to check the spherical component of the refraction ...
They've Taken the Stigma Out of Astigmatism. Baseball Digest (Lakeside Publishing Co.). pp. 53-54. ISSN 0005-609X. H. G. ...
Maddox, Ernest Edmund (1889). New kind of spectacles for astigmatism (Thesis). University of Edinburgh. hdl:1842/24112. ...
Astigmatism can be cancelled by including a third curved optical element. When this element is a mirror, the result is a three- ... If the mirror is made parabolic, to correct the spherical aberration, then it still suffers from coma and astigmatism, since ... However, such designs still suffer from astigmatism. The basic Ritchey-Chrétien two-surface design is free of third-order coma ... However, the two-surface design does suffer from fifth-order coma, severe large-angle astigmatism, and comparatively severe ...
Seiler T, Bende T, Wollensak J, Trokel S (February 1988). "Excimer laser keratectomy for correction of astigmatism". American ... of astigmatism. For myopia, Asians had the highest prevalence (19%), followed by Hispanics (13%). Caucasian children had the ...
Defective vision occurs due to marked corneal astigmatism. Treatment consists of localised staphylectomy under heavy doses of ...
Levy, Richard Lawrence; Rogers, Gary F.; Mulliken, John B.; Proctor, Mark R.; Dagi, Linda R. (2007). "Astigmatism in unilateral ... particularly astigmatism, due to asymmetrical development of the orbits. Unilateral lambdoid synostosis is also called ...
... oblique astigmatism). Refractive errors containing higher order aberrations (sometimes referred to as irregular astigmatism) ... Astigmatism: A person with astigmatic refractive error sees lines of a particular orientation less clearly than lines at right ... Near-sightedness is due to the length of the eyeball being too long, far-sightedness the eyeball too short, astigmatism the ... In the case of regular astigmatism, refractive error needs to be expressed as 3 values: classically as sphere, cylinder and ...
Many older people have a slight, comfortable astigmatism. At the high resolution of modern computer screens, they better see ...
"Kilmanjaro and Young Clancy team up on Astigmatism". Red Bull. Retrieved 2021-02-18. "Meet the talent heading to RBMA Bass Camp ...
Sources of this astigmatism include misaligned objectives, non-uniform magnetic fields of the lenses, which was especially hard ... A stigmator is a component of electron microscopes that reduces astigmatism of the beam by imposing a weak electric or magnetic ... In most cases, the astigmatism can be corrected using a constant stigmator field which is adjusted by the microscope operator. ... The main cause of astigmatism, the non-uniform magnetic field produced by the lenses, usually does not change noticeable during ...
There is an induced astigmatism that is correctable. This deflection idea has been tested and verified. Deflection angles of 50 ...
Dr Garg discusses a paper from Girish Valluru and colleagues on astigmatism and its effect on cataract surgery. ... We know that ATR astigmatism increases with age and often can be more visually impactful that WTR astigmatism. Overall, this ... In the early cohort, astigmatism was determined by retinoscopy, whereas in the 2000s, astigmatism was determined by automated ... Astigmatism. How much is really out there? Does it need to be treated? What is the best way to measure it? Is it stable? Does ...
Astigmatism is a type of refractive error of the eye. Refractive errors cause blurred vision. They are the most common reason ... If astigmatism gets worse, it may be a sign of keratoconus.. Astigmatism is very common. It sometimes occurs after certain ... The cause of astigmatism is unknown. It is most often present from birth. Astigmatism often occurs together with ... Astigmatism is easily diagnosed by a standard eye exam with refraction test. Special tests are not required in most cases. ...
Learn about the symptoms, causes, diagnosis, and treatment of astigmatism. ... Astigmatism is a common eye problem that can make your vision blurry or distorted. It happens when your cornea (the clear front ... What is astigmatism? Astigmatism is a common eye problem that can make your vision blurry or distorted. It happens when your ... What causes astigmatism? Astigmatism happens when your cornea or lens has a different shape than normal. The shape makes light ...
The surgical correction of astigmatism was first attempted with astigmatic keratotomy, which is described in this article, ... encoded search term (LASIK for Correction of Astigmatism) and LASIK for Correction of Astigmatism What to Read Next on Medscape ... LASIK for Correction of Astigmatism Workup. Updated: May 21, 2019 * Author: David R Hardten, MD; Chief Editor: Michael ... Photorefractive keratectomy for astigmatism greater than -2.00 diopters in eyes with low, high, or extreme myopia. J Cataract ...
Can I ignore my astigmatism?. March 23, 2012 4:49 PM Subscribe. I am a new eyeglass wearer and the astigmatism correction (the ... so obviously I dont need an astigmatism correction, plus it seems as though whatever astigmatism I have flips around ... My glasses had astigmatism correction and my contacts do not. I cant tell the difference. If your optometrist says you need ... How new of a wearer are you? I only have astigmatism correction and when I got new glasses last year it took a few weeks to get ...
A:The patient seems to have high astigmatism (compound myopic astigmatism). The dictum in prescription is to usually prescribe ... How to treat high astigmatism?. Answered by: Dr Rishi Mohan , Consultant Ophthalmologist, Indraprastha Apollo Hospital,. New ... Home » Frequently asked Questions on Health » How to treat high astigmatism?. ...
Bausch and Lomb PureVision 2 HD Astigmatism contact lenses (6 pack) online. Lens has a best price guarantee, with rebates. View ... About Astigmatism. Astigmatism is an imperfection in the eyes curvature that causes blurred vision. Ideally, the eye is shaped ... PureVision 2 HD for Astigmatism FAQs. Can I wear PureVision 2 HD for Astigmatism contact lenses for extended periods of time? ... Most people who have astigmatism are born with it, but its unclear why this is the case. You can also get astigmatism after an ...
The difference between the astigmatism of anterior corneal surface and total cornea was detected in the measurement of ... Total corneal astigmatism measured by IOLMaster was consistent with that measured by Pentacam. ... A-ACS: corneal astigmatism of anterior corneal astigmatism. (b) Correlation of total corneal astigmatism. TCA: total corneal ... f) Astigmatism of total cornea (TCA) between IOLMaster and Pentacam. (g) Astigmatism of anterior corneal surface (A-ACS) and ...
... stable vision to correct your astigmatism. Buy Toric TR8 Brown lenses from Lensupermart to get clear and stable vision. ... Introducing Dueba Toric - TR8 Brown, the perfect solution for astigmatism. With a high prescription range up to -10.00, these ...
... provides an update on the currently available phakic intraocular lenses for the correction of myopia or myopic astigmatism. ... The use of these devices for the correction of myopia with or without astigmatism has become a popular topic in the ... Phakic Intraocular Lenses: An Update and Review for the Treatment of Myopia and Myopic Astigmatism in the United States. ... available in the United States for the correction of myopia or myopic astigmatism and offer a clinical approach to their proper ...
Shop Biotrue ONEday for Astigmatism 30pk contact lenses at Eyeconic. We accept VSP, MetLife and Cigna vision insurance, plus ... Biotrue® ONEday for Astigmatism daily disposable contact lenses have more moisture than any other contact lens and maintain ... Biotrue® ONEday for Astigmatism daily disposable contact lenses have more moisture than any other contact lens and maintain ... With stable High Definition Optics, the Biotrue® ONEday for Astigmatism lenses help reduce halos and glare in low light ...
How is astigmatism treated?. People with astigmatism have several options to regain clear vision. They include:. *Eyeglasses. ... Sometimes astigmatism may develop following an eye injury or eye surgery.. Astigmatism also occurs due to a relatively rare ... How is astigmatism diagnosed?. An optometrist can diagnose an astigmatism through a comprehensive eye examination. Testing for ... What causes astigmatism?. The curvature of the cornea and lens bends the light entering the eye in order to focus it precisely ...
Astigmatism. Astigmatism, together with nearsightedness and farsightedness, is a type of refractive error. In 2010, astigmatism ... Astigmatism may even develop during childhood. Astigmatism is caused by an irregular curvature of the cornea , which in this ... The exact cause of astigmatism formation has not been fully documented, but the development of this eye defect may involve ... Discovering the presence of potential disease-causing genes involved in the development of astigmatism can be helpful for ...
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Everything you need to know about astigmatism. Definition, prevalence, causes, treatment and more, expert reviewed by eye Dr. ... Can you have astigmatism in one eye?. In the vast majority of cases, astigmatism appears in both eyes. Cases with astigmatism ... Regular astigmatism is more common than irregular astigmatism. Irregular astigmatism is more often the result of an eye injury. ... Can astigmatism go away on its own?. Astigmatism will not go away on its own. It will either stay the same or get worse with ...
AstigmatismClear LensesColor LensesMultifocalToricBlack LensesBrown LensesBlue LensesGold LensesGray LensesGreen LensesRed ... Astigmatism Contact Lenses. Filter. Showing: 1-4 of 4Results Sort By. Sort By. Featured. Best Selling. A-Z. Z-A. Lowest Price. ... Air Optix for Astigmatism Contact Lenses 3 Pack. Regular price$38.95 USD ... Acuvue Oasys 1 Day with Hydraclear for Astigmatism Contacts 30 Pack. Regular price$44.95 USD ...
CooperVision defines the causes of astigmatism, its symptoms and cure. Find out how our toric contact lenses can improve your ... Treatment for astigmatism. As weve said, most forms of astigmatism are easy to treat. You have several corrective choices. ... How do you get astigmatism?. Simply put, astigmatism is a condition derived from a cornea or lens thats stretched into an ... Contact lenses for astigmatism. Toric contact lenses are usually prescribed for eye care patients with astigmatism. ...
If you have astigmatism - a subtle difference in the shape of your cornea that can cause blurry vision - it doesnt mean you ... Because lenses for astigmatism require two prescriptions that must stay in place relative to the eye, stability is key to clear ... AIR OPTIX® for Astigmatism (lotrafilcon B) contact lenses: High oxygen transmissible lenses. Dk/t = 108 @ -3.00D -1.25D x 180. ... AIR OPTIX® for Astigmatism contact lenses offer exceptionally stable vision and a breakthrough design that delivers outstanding ...
Astigmatism And Lifestyle: Tips For Managing Astigmatism And Minimizing Its Impact On Daily Activities. Astigmatism is a common ...
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What can be done for astigmatism?. There are multiple treatments that may be appropriate for astigmatism. When the curvature is ... Astigmatism is an asymmetrical curve of the cornea. In the healthiest scenario, this structure would exhibit a rounded curve. ... If you have any of the symptoms of astigmatism, such as frequent headaches or eye fatigue, blurred or distorted vision up-close ... Your vision is blurry, and that could mean that you have astigmatism. It could also mean that you have presbyopia. Both ...
Learn about astigmatism and how a Pearle Vision eye doctor can help treat it so you can see clearly. Schedule an eye exam today ... How to Correct Astigmatism. An eye doctor can help determine whether you have astigmatism, and if so, to what degree. In some ... What causes Astigmatism?. AWhile astigmatism is often present at birth, it can also be acquired later in life due to various ... What Does Astigmatism Look Like?. Astigmatism is a common eye condition that causes blurry vision. This is due to an ...
ATR astigmatism is the most common type of astigmatism in adults greater than 40 years of age . The amount of ATR change per ... What is Astigmatism and how can cataract surgery correct it?. Astigmatism relates to the curvature of your cornea, the clear, ... Astigmatism Surgery Options That You Should Know. Astigmatism is a common vision problem that can make things look blurry or ... This Is The Best Cataract Surgery For Astigmatism. So you have astigmatism? You are not alone. In fact, there are millions just ...
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Astigmatism Surgeon Dr. Arun Gulani provides treatment solutions to restore your vision to 20/20. ... Jacksonville Astigmatism Doctor Dr. Gulani provides information about Astigmatism correction, which is not intended as medical ... Gulani is a world renowned eye surgeon and Astigmatism specialist. Former Chief of the Cornea service and Asst. Professor at ... Our office specializes in Astigmatism Jacksonville, Florida and also serves, Jacksonville Beach, Orange Park, Ponte Vedra and ...
What is astigmatism? Astigmatism occurs when the cornea is shaped like a rugby ball, as opposed to spherical like a football. ... PRECISION1® FOR ASTIGMATISM. Easy-to-wear, easy-to-love daily disposable contact lenses for people with astigmatism.3 4** ... Alcon, DAILIES® AquaComfort® PLUS Toric,PRECISION1® for Astigmatism, AIR OPTIX® PLUS HYDRAGLYDE® FOR ASTIGMATISM and Alcon ... Toric contact lenses are specially designed to correct astigmatism. Each lens requires a unique prescription and must be fitted ...
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  • In keratoconus, progressive thinning and steepening of the cornea cause irregular astigmatism. (wikipedia.org)
  • Astigmatism often occurs together with nearsightedness or farsightedness. (medlineplus.gov)
  • Laser surgery can help change the shape of the cornea surface to eliminate astigmatism, along with nearsightedness or farsightedness. (medlineplus.gov)
  • When it comes to nearsightedness, farsightedness, and astigmatism, most people aren't quite sure of the differences. (rebuildyourvision.com)
  • According to the World Health Organization, refractive errors (nearsightedness, farsightedness, astigmatism and presbyopia) account for 43% of visual impairments occurring globally. (levelaccess.com)
  • Lastly, astigmatism can occur combined with other refractive errors such as simple and compound myopic, simple and compound hyperopic, and mixed with both nearsightedness and farsightedness. (momwithfive.com)
  • Unlike farsightedness or nearsightedness, astigmatism causes blurred vision at any distance. (voaeye.com)
  • Many people have astigmatism as well as farsightedness or nearsightedness. (voaeye.com)
  • More than 8 million people had vision impairment caused by an uncorrected refractive error, such as nearsightedness or astigmatism. (cdc.gov)
  • LASEK is specifically used to correct astigmatism, hyperopia (farsightedness), and myopia (nearsightedness). (medscape.com)
  • In a study conducted in 2011 on various Asian populations, variants in the PDGFRA gene on chromosome 4q12 were identified to be associated with corneal astigmatism. (wikipedia.org)
  • A follow-up study in 2013 on the European population, however, found no variant significantly associated with corneal astigmatism at the genome-wide level (single-nucleotide polymorphism rs7677751 at PDGFRA). (wikipedia.org)
  • They successfully replicated the previously identified genome-wide significant locus for corneal astigmatism near the PDGFRA gene, with a further success of identifying three novel candidate genes: CLDN7, ACP2, and TNFAIP8L3. (wikipedia.org)
  • Another recent follow-up study again had identified four novel loci for corneal astigmatism, with two also being novel loci for astigmatism: ZC3H11B (associated with axial length), NPLOC4 (associated with myopia), LINC00340 (associated with spherical equivalent refractive error) and HERC2 (associated with eye color). (wikipedia.org)
  • Astigmatism may also occur following a cataract surgery or a corneal injury. (wikipedia.org)
  • There may be errors in the preoperative assessments of axial length and corneal power, an unknown history of prior refractive surgery, incorrect IOL placement or positioning, or residual regular or irregular corneal astigmatism. (crstodayeurope.com)
  • It is important to remember that these procedures specifically treat postoperative refractive cylinder, not corneal astigmatism alone. (crstodayeurope.com)
  • For example, if the cornea is distorted, it's called corneal astigmatism. (momwithfive.com)
  • One notable limitation was the lack of inclusion of posterior corneal astigmatism in toric calculations. (medscape.com)
  • Concepts of corneal refractive surgery, such as keratectomy, keratotomy, and thermokeratoplasty, were first described in 1898 by Lans who published a set of experiments that focused on treating astigmatism in rabbits. (medscape.com)
  • Since its introduction, LASIK has been associated with various complications, specifically when performed on eyes with decreased corneal thickness, irregular astigmatism, dryness, preexisting ocular surface disease, or glaucoma, to the point where several of these entities have become relative contraindications to performing LASIK. (medscape.com)
  • Asimetrías en la topografía e índice de refracción de la superficie corneal que afectan a la agudeza visual. (bvsalud.org)
  • The underlying mechanism involves an irregular curvature of the cornea and protective reaction changes in the lens of the eye, called lens astigmatism, that has the same mechanism as spasm of accommodation. (wikipedia.org)
  • Irregular astigmatism - principal meridians are not perpendicular. (wikipedia.org)
  • Additionally, the surgeon must accurately assess the spherical and astigmatic refractive error and differentiate between regular and irregular astigmatism. (crstodayeurope.com)
  • However, there is also the division into regular and irregular astigmatism, based on their meridians, as well as other types of astigmatism that occur with a refractive error. (momwithfive.com)
  • Irregular astigmatism is similar but differs in that the curvature is uneven or goes in multiple directions. (momwithfive.com)
  • Astigmatism is one common form of visual impairment that results from irregular anatomy. (voaeye.com)
  • Another possible complication of these infections is uneven healing of the stroma, resulting in irregular astigmatism (that may require a gas-permeable contact lens or PTK to improve vision). (medscape.com)
  • These initial attempts were complex and unpredictable, often leading to keratoconus and other irregular astigmatisms. (medscape.com)
  • SMILE is a safe, effective, predictable, and stable means of correcting high myopia and myopic astigmatism over a 4-year postoperative period. (frontiersin.org)
  • As such, the present study was designed to assess postoperative visual and refractive outcomes of SMILE-based correction of myopia and myopic astigmatism of over −10 D, with the goal of evaluating the safety, efficacy, predictability, and stability of this procedure over a 4-year postoperative period. (frontiersin.org)
  • Bausch + Lomb ????? ?????? ??? Biotrue ONEday for Astigmatism. (linzshop.ru)
  • ACUVUE OASYS Brand for ASTIGMATISM is a combination of ACUVUE's BLINK STABILIZED lens design and the comfort of HYDRACLEAR PLUS Technology to create a lens for consistently clear vision for persons with astigmatism, blurred or fluctuating vision. (eyewearsolutions.com)
  • Acuvue Oasys Astigmatism Rebate - Although Acuvue contact lens are highly regarded for their high-quality and comfort they can also be quite expensive. (acuvuerebate.com)
  • Acuvue Oasys Astigmatism Rebates - Acuvue contact lenses are known for their comfort and quality however, they can sometimes be expensive. (acuvuerebate.com)
  • Acuvue Oasys With Astigmatism Rebate - Contact lenses from Acuvue are known for their comfort and high-quality. (acuvuerebate.com)
  • Acuvue Oasys for Astigmatism by Johnson and Johnson is a fortnightly disposable contact lens that is specially made for contact lens wearers with astigmatism. (contactsasia.com)
  • Like other lenses of the Acuvue product family, Acuvue Oasys for Astigmatism also uses the unique Accelerated Stabilisation Design (ASD) and the patented Hydraclear Plus Technology that makes the lens ultra smooth, more moist and transmits more oxygen than conventional contact lenses. (contactsasia.com)
  • In this situation, early diagnosis of visual problems is essential for patients to progress in the neurological and motor fields, and there are complications such as refractive errors (myopia, astigmatism and hyperopia), strabismus and hypoactomy. (bvsalud.org)
  • If astigmatism gets worse, it may be a sign of keratoconus . (medlineplus.gov)
  • An increasingly popular way to manage astigmatism is with the use of a toric (astigmatism correcting) intraocular lens (IOL). (medscape.com)
  • Most commonly, treatment for astigmatism consists of prescription eyeglasses or contact lenses. (voaeye.com)
  • Astigmatism can be corrected with prescription eyeglasses or contact lenses. (msdmanuals.com)
  • ??????? Bausch+Lomb , ??? ?????? ????? ?????? ??? ???????? ????????? ??? Ultra for Astigmatism. (linzshop.ru)
  • It is important to note that nearly everyone has some degree of astigmatism, as ocular structures are rarely perfectly shaped. (voaeye.com)
  • According to dioptric value astigmatism patient are classified low, moderate and high degree of astigmatism patient. (optography.org)
  • Therefore, it was determined that the residual myopic astigmatism would best be corrected with laser vision correction. (crstodayeurope.com)
  • Asthenopic symptoms are more compenivel by hypermetropic astigmatism patients than myopic patients. (optography.org)
  • Hypermetropic Astigmatism patients are more symptomatic then the myopic astigmatism patient. (optography.org)
  • Laser vision correction can most often eliminate, or greatly reduce astigmatism. (medlineplus.gov)
  • Because of the coupling effect, LRIs can reduce astigmatism without changing the spherical power. (crstodayeurope.com)
  • Glasses or contact lenses will correct astigmatism, but do not cure it. (medlineplus.gov)
  • Li and associates, however, found no consistent or strong genetic signals for refractive astigmatism while suggesting a possibility of widespread genetic co-susceptibility for spherical and astigmatic refractive errors. (wikipedia.org)
  • That being said, the markerless guidance group showed a statistically significant improvement in mean remaining refractive astigmatism compared with intraoperative aberrometry in this matched cohort. (medscape.com)
  • This case illustrates decreased visual acuity from residual astigmatism despite a spherical equivalent near plano. (crstodayeurope.com)
  • Contraction of the scar due to wound or cataract extraction causes astigmatism due to flattening of the cornea in one direction. (wikipedia.org)
  • Control of astigmatism in cataract surgery. (bmj.com)
  • Cite this: Minimizing Astigmatism in Cataract Surgery - Medscape - Oct 19, 2017. (medscape.com)
  • A three-dimensional (3D) single fluorescent particle tracking strategy based on temporal focusing multiphoton excitation microscopy (TFMPEM) combined with astigmatism imaging is proposed for delivering nanoscale-level axial information that reveals 3D trajectories of single fluorospheres in the axially-resolved multiphoton excitation volume without z-axis scanning. (ncu.edu.tw)
  • The author concludes that the tolerances for sphere power, axial astigmatism, and prism in a single lens given in Z87.1 were adequate. (cdc.gov)
  • Astigmatism often occurs at birth and can change or develop later in life. (wikipedia.org)
  • Astigmatism is a fairly common eye problem, as it occurs in a third of Americans. (momwithfive.com)
  • Astigmatism occurs when either the cornea or the lens is abnormally curved. (voaeye.com)
  • While astigmatism by itself is not a life-threatening condition, it can be an indirect cause of serious trauma or death if a vehicle driver refrains from wearing corrective lenses while driving, especially at night or in poor weather conditions. (wikipedia.org)
  • Astigmatism may change with time, requiring new glasses or contact lenses. (medlineplus.gov)
  • Astigmatism Lenses. (foreyes.com)
  • DAILIES TOTAL1® are the only contact lenses for astigmatism to feature water gradient technology, which increases the water content to almost 100% near the surface of the lens. (lensesforless.com)
  • Acuvue Astigmatism Rebate - Contact lenses made by Acuvue have a reputation for their quality and comfort however, they aren't cheap. (acuvuerebate.com)
  • While conventional treatments like eyeglasses, contact lenses, or refractive surgeries are widely used, many individuals seek natural remedies to address astigmatism and improve their vision without invasive procedures. (ayurhealing.net)
  • 2.00 DS/ -1.00 DC × 90° this type of glass prescription are example of astigmatism. (optography.org)
  • With-the-rule astigmatism - the vertical meridian is steepest (a rugby ball or American football lying on its side). (wikipedia.org)
  • The most prevalent form of astigmatism where the vertical meridian has more plus power, i.e., the eye is steepest in the vertical meridian. (eyepatient.net)
  • Most of the astigmatism patients are belong to asthenopic symptoms. (optography.org)
  • There notified that low astigmatism patients are more complained of Asthenopic symptoms. (optography.org)
  • Regular astigmatism entails a curvature of the eye that is not completely round, with the eye curved in one direction more. (momwithfive.com)
  • Astigmatism is an irregularity in the curvature of the cornea or lens. (msdmanuals.com)
  • Some research has pointed to the link between astigmatism and higher prevalence of migraine headaches. (wikipedia.org)
  • Some studies have estimated the prevalence of astigmatism in children aged 5-17 to be as high as 28 percent, a number that's widely believed to increase with age. (rebuildyourvision.com)
  • Against-the-rule astigmatism - the horizontal meridian is steepest (a rugby ball or American football standing on its end). (wikipedia.org)
  • It focused in two different meridian focus, For this reason the astigmatism patients are not see the clearly. (optography.org)
  • According to a recent study of 2,523 children in the United States between the ages of 5 and 17, more than 28% have astigmatism of 1.0 diopters (D) or greater. (levelaccess.com)
  • Do you know what will be the problem occur if someone have astigmatism? (optography.org)
  • It is Emmetropic (normal condition of the Eye) but when the light rays entering the eye and can't coverage to a point focus, instead it formed a focal lines, then astigmatism occur. (optography.org)
  • Speaking of contacts, they also offer astigmatism correction. (momwithfive.com)
  • A comprehensive optometry exam checks your eye anatomy and vision for signs of astigmatism. (voaeye.com)
  • In children, uncorrected astigmatism in only one eye may cause amblyopia . (medlineplus.gov)
  • Astigmatism is a visual condition where there is a refractive error that impedes the eye from focusing light evenly on the retina. (levelaccess.com)
  • Genetics, based on twin studies, appear to play only a small role in astigmatism as of 2007. (wikipedia.org)
  • There are a few factors which can influence the development of astigmatism, such as genetics and ethnicity, but your anatomy of your eye, such as how your eyelids sit against your cornea determine whether you have astigmatism or not. (eyemountain.com)
  • In Europe and Asia, astigmatism affects between 30% and 60% of adults. (wikipedia.org)
  • Astigmatism is a type of refractive error that affects how you see. (momwithfive.com)
  • Astigmatism is a common refractive error of the eye that affects how light enters the eye, causing blurred or distorted vision. (ayurhealing.net)
  • Astigmatism is created completely separately than how a concussion affects your vision. (eyemountain.com)
  • Astigmatism really has an anatomical basis mostly in the cornea. (eyemountain.com)
  • RÉSUMÉ Le diagnostic et la prise en charge précoces d'un strabisme sont nécessaires pour éviter les complications telles qu'une amblyopie. (who.int)
  • Astigmatism is very common. (medlineplus.gov)
  • Astigmatism may not be the best-known eye disorder, but it's certainly among the most common. (rebuildyourvision.com)
  • Astigmatism is a common issue, so even if it turns out you have it, don't worry. (momwithfive.com)
  • Astigmatism is very common and relatively easy to treat. (voaeye.com)
  • Fortunately, the only thing astigmatism has in common with a concussion is that they can both cause blurred vision. (eyemountain.com)
  • Maintaining good eye health through diet is crucial for managing astigmatism. (ayurhealing.net)
  • As such, the management of astigmatism is crucial in delivering optimal outcomes to patients. (medscape.com)
  • Astigmatism patient complain that he/she are not see the object clearly. (optography.org)
  • The astigmatic patient who are belongs to low astigmatism, sometimes they complains that transient blurring of vision when doing precision work at a fixed distance, which is relived by closing or rubbing the eyes. (optography.org)
  • Here notified that with the rule of astigmatism patients are more symptomatic but it's get clear vision then the same amount of against the rule of astigmatism patient. (optography.org)
  • If you get hit in the head and there is an injury to the cornea that must be repaired with stitches, then you can end up with astigmatism from that injury. (eyemountain.com)
  • Ayurveda, the ancient Indian system of medicine, offers holistic approaches to treating various health conditions, including eye disorders like astigmatism. (ayurhealing.net)
  • Amla is a powerhouse of vitamin C and antioxidants, making it a valuable herbal remedy for improving vision and preventing eye disorders like astigmatism. (ayurhealing.net)
  • Oblique astigmatism - the steepest curve lies in between 120 and 150 degrees and 30 and 60 degrees. (wikipedia.org)
  • Aside from Ayurvedic remedies, making lifestyle modifications can significantly contribute to managing astigmatism and promoting better vision. (ayurhealing.net)
  • But subjective methods are almost always inaccurate if lens astigmatism is not fully removed first with a week of eye drops. (wikipedia.org)
  • This effect is known to reduce text readability and is particularly bad for people with astigmatism because it can cause terrible headaches. (levelaccess.com)
  • 1-Day Acuvue Moist for Astigmatism is a 58% water, daily disposable lens that is not only visibility tinted for easy handling but also has a moisturizer and UV blocking capability. (foreyes.com)
  • People of all ages can be affected by astigmatism. (wikipedia.org)
  • Astigmatism is one of those buzzwords in the eye care world that most people have heard of, but very few know what it actually means. (rebuildyourvision.com)
  • Know your users - astigmatism impacts a wide range of people, young and old. (levelaccess.com)
  • In fact, for most people, you're either born to have astigmatism or you are not. (eyemountain.com)
  • Astigmatism is easily diagnosed by a standard eye exam with refraction test . (medlineplus.gov)
  • To see if you have astigmatism, you should go to an eye doctor who will do a comprehensive eye exam. (momwithfive.com)
  • A person with astigmatism (each eye should be tested separately) tends to see certain lines more boldly (that is, in better focus) than the others. (msdmanuals.com)