Corneal Topography
Keratoconus
Cornea
Lasers, Excimer
Astigmatism
Photorefractive Keratectomy
Keratomileusis, Laser In Situ
Myopia
Refractive Surgical Procedures
Keratoplasty, Penetrating
Aberrometry
Visual Acuity
Refractive Errors
Zernike representation of corneal topography height data after nonmechanical penetrating keratoplasty. (1/329)
PURPOSE: To demonstrate a mathematical method for decomposition of discrete corneal topography height data into a set of Zernike polynomials and to demonstrate the clinical applicability of these computations in the postkeratoplasty cornea. METHODS: Fifty consecutive patients with either Fuchs' dystrophy (n = 20) or keratoconus (n = 30) were seen at 3 months, 6 months, and 1 year (before suture removal) and again after suture removal following nonmechanical trephination with the excimer laser. Patients were assessed using regular keratometry, corneal topography (TMS-1, simulated keratometry [SimK]), subjective refraction, and best-corrected visual acuity (VA) at each interval. A set of Zernike coefficients with radial degree 8 was calculated to fit two model surfaces: a complete representation (TOTAL) and a representation with parabolic terms only to define an approximate spherocylindrical surface (PARABOLIC). The root mean square error (RMS) was calculated comparing the corneal raw height data with TOTAL (TOTALRMS) and PARABOLIC (PARABOLICRMS). The cylinder of subjective refraction was correlated with the keratometric readings, the SimK, and the respective Zernike parameter. Visual acuity was correlated with the tilt components of the Zernike expansion. RESULTS: The measured corneal surface could be approximated by the composed surface 1 with TOTALRMS < or = 1.93 microm and by surface 2 with PARABOLICRMS < or = 3.66 microm. Mean keratometric reading after suture removal was 2.8+/-0.6 D. At all follow-up examinations, the SimK yielded higher values, whereas the keratometric reading and the refractive cylinder yielded lower values than the respective Zernike parameter. The correlation of the Zernike representation and the refractive cylinder (P = 0.02 at 3 months, P = 0.05 at 6 months and at 1 year, and P = 0.01 after suture removal) was much better than the correlation of the SimK and refractive cylinder (P = 0.3 at 3 months, P = 0.4 at 6 months, P = 0.2 at 1 year, and P = 0.1 after suture removal). Visual acuity increased from 0.23+/-0.10 at the 3-month evaluation to 0.54+/-0.19 after suture removal. After suture removal, there was a statistically significant inverse correlation between VA and tilt (P = 0.02 in patients with keratoconus and P = 0.05 in those with Fuchs' dystrophy). CONCLUSIONS: Zernike representation of corneal topography height data renders a reconstruction of clinically relevant corneal topography parameters with a marked reduction of redundance and a small error. Correlation of amount/axis of refractive cylinder with respective Zernike parameters is more accurate than with keratometry or respective SimK values of corneal topography analysis. (+info)Changes in corneal wavefront aberrations with aging. (2/329)
PURPOSE: To investigate whether corneal wavefront aberrations vary with aging. METHODS: One hundred two eyes of 102 normal subjects were evaluated with videokeratography. The data were decomposed using Taylor and Zernike polynomials to calculate the monochromatic aberrations of the cornea for both small (3-mm) and large (7-mm) pupils. RESULTS: For a 3-mm pupil, the amount of total aberrations (Spearman rank correlation coefficient r(s) = 0.145; P = 0.103) and spherical-like aberrations (r(s) = -0.068; P = 0.448) did not change with aging, whereas comalike aberrations exhibited a weak but statistically significant correlation with age (r(s) = 0.256; P = 0.004). For a 7-mm pupil, total aberrations (r(s) = 0.552; P < 0.001) and comalike aberrations (r(s) = 0.561; P < 0.001) significantly increased with aging, but spherical-like aberrations showed no age-related changes (r(s) = 0.124; P = 0.166). Simulated pupillary dilation from 3 mm to 7 mm caused a 38.0+/-28.5-fold increase in the total aberrations, and the extent of increases significantly correlated with age (r(s) = 0.354; P < 0.001). Pupillary dilation influenced the comalike aberrations more in the older subjects than in the younger subjects (r(s) = 0.243; P = 0.006), but such age dependence was not found for spherical-like aberrations (r(s) = 0.141; P = 0.115). CONCLUSIONS: Comalike aberrations of the cornea correlate with age, implying that the corneas become less symmetrical along with aging. Spherical-like aberrations do not vary significantly with aging. Pupillary dilation markedly increases wavefront aberrations, and those effects are more prominent in older subjects than in younger subjects. (+info)Evaluation of corneal thickness and topography in normal eyes using the Orbscan corneal topography system. (3/329)
AIMS: To map the thickness, elevation (anterior and posterior corneal surface), and axial curvature of the cornea in normal eyes with the Orbscan corneal topography system. METHODS: 94 eyes of 51 normal subjects were investigated using the Orbscan corneal topography system. The anterior and posterior corneal elevation maps were classified into regular ridge, irregular ridge, incomplete ridge, island, and unclassified patterns, and the axial power maps were grouped into round, oval, symmetric bow tie, asymmetric bow tie, and irregular patterns. The pachymetry patterns were designated as round, oval, decentred round, and decentred oval. RESULTS: The thinnest point on the cornea was located at an average of 0.90 (SD 0. 51) mm from visual axis and had an average thickness of 0.55 (0.03) mm. In 69.57% of eyes, this point was located in the inferotemporal quadrant, followed by the superotemporal quadrant in 23.91%, the inferonasal quadrant in 4.35%, and the superonasal quadrant in 2.17%. Among the nine regions of the cornea evaluated (central, superotemporal, temporal, inferotemporal, inferior, inferonasal, nasal, superonasal, and superior) the central cornea had the lowest average thickness (0.56 (0.03) mm) and the superior cornea had the greatest average thickness (0.64 (0.03) mm). The mean simulated keratometry (SimK) was 44.24 (1.61)/43.31 (1.66) dioptres (D) and the mean astigmatism was 0.90 (0.41) D. Island (71.74%) was the most common elevation pattern observed in the anterior corneal surface, followed by incomplete ridge (19.57%), regular ridge (4.34%), irregular ridge (2.17%), and unclassified (2.17%). Island (32.61%) was the most common topographic pattern in the posterior corneal surface, following by regular ridge (30.43%), incomplete ridge (23. 91%), and irregular ridge (13.04%) patterns. Symmetric bow tie was the most common axial power pattern in the anterior cornea (39.13%), followed by oval (26.07%), asymmetric bow tie (23.91%), round (6. 52%), and irregular (4.53%) patterns. In the pachymetry maps, 47.83% of eyes had an oval pattern, and round, decentred oval, and decentred round were observed in 41.30%, 8.70%, and 2.18% of eyes, respectively. CONCLUSION: The information on regional corneal thickness, corneal elevation and axial corneal curvature obtained with the Orbscan corneal topography system from normal eyes provides a reference for comparison with diseased corneas. The Orbscan corneal topography system is a useful tool to evaluate both corneal topography and corneal thickness. (+info)Proposed classification for topographic patterns seen after penetrating keratoplasty. (4/329)
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)Reassessment of the corneal endothelial cell organisation in children. (5/329)
AIM: To assess uniformity of the corneal endothelial cell mosaic in children. METHODS: 36 healthy children (5-11 years old, 16 boys, 20 girls) were assessed by specular microscopy. Endothelial cell density (ECD) was calculated from measured cell areas, and the number of sides/cell noted. RESULTS: Average values for ECD and cell areas were 3987 cells/mm(2) (95% CI 3806 to 4168 cells/mm(2)) and 278 (SD 85) mm(2) respectively, with normal distribution (COV 28. 2%, range 17.4 to 39.2%) and with the average percentage of six sided cells being 66.6% (8.8%). Cell area was positively correlated to number of cell sides (p <0.01, r(2)=0.993), but the percentage of six sided cells was negatively correlated to ECD (p <0.01, r=0.493). CONCLUSION: A high ECD occurs in children, but this does not mean there is a high percentage of "hexagons". (+info)Pterygium-induced corneal astigmatism. (6/329)
BACKGROUND: Previous work has suggested an association between increasing size of pterygium and increasing degrees of induced corneal astigmatism. OBJECTIVES: To assess the quantitative relation between pterygium size and induced corneal astigmatism using a computerized corneal analysis system (TMS II) and slit-lamp beam evaluation of pterygium size, and to conclude whether corneal astigmatism is an early indication for surgical intervention. METHODS: We evaluated 94 eyes of 94 patients with unilateral primary pterygium of different sizes, using TMS II and slit-lamp beam measurements of the size of the pterygium (in millimeters) from the limbus to assess parameters of pterygium size with induced corneal astigmatism. Best corrected visual Snellen acuity was performed. RESULTS: Primary pterygium induced with-the-rule astigmatism. Pterygium extending > 16% of the corneal radius or 1.1 mm or less from the limbus produced increasing degrees of induced astigmatism of more than 1.0 diopter. Significant astigmatism was found in 16.16% of 24 eyes with pterygium of 0.2 up to 1.0 mm in size, in 45.45% of 22 eyes with pterygium of 1.1 up to 3.0 mm in size (P < or = 0.0004), and in 100% of 3 eyes with pterygium of 5.1 up to 6.7 mm in size (P = 0.0005). We found that visual acuity was decreased when topographic astigmatism was increased. CONCLUSIONS: When primary pterygium reaches more than 1.0 mm in size from the limbus it induces with-the-rule significant astigmatism (> or = 1.0 diopter). This significant astigmatism tends to increase with the increasing size of the lesion. Topographic astigmatism tends to be improved by successful removal of the pterygium. These findings suggest that early surgical intervention in the pterygium may be indicated when the lesion is more than 1.0 mm in size from the limbus. (+info)Effect of disagreement between refractive, keratometric, and topographic determination of astigmatic axis on suture removal after penetrating keratoplasty. (7/329)
BACKGROUND/AIMS: Post-keratoplasty astigmatism can be managed by selective suture removal in the steep axis. Corneal topography, keratometry, and refraction are used to determine the steep axis for suture removal. However, often there is a disagreement between the topographically determined steep axis and sutures to be removed and that determined by keratometry and refraction. The purpose of this study was to evaluate any difference in the effect of suture removal, on visual acuity and astigmatism, in patients where such a disagreement existed. METHODS: 37 cases (from 37 patients) of selective suture removal after penetrating keratoplasty, were included. In the first group "the disagreement group" (n=15) there was disagreement between corneal topography, keratometry, and refraction regarding the axis of astigmatism and sutures to be removed. In the second group "the agreement group" (n=22) there was agreement between corneal topography, keratometry, and refraction in the determination of the astigmatic axis and sutures to be removed. Sutures were removed according to the corneal topography, at least 5 months postoperatively. Vector analysis for change in astigmatism and visual acuity after suture removal was compared between groups. RESULTS: In the disagreement group, the amount of vector corrected change in refractive, keratometric, and topographic astigmatism after suture removal was 3.45 (SD 2.34), 3.57 (1.63), and 2.83 (1. 68) dioptres, respectively. In the agreement group, the amount of vector corrected change in refractive, keratometric, and topographic astigmatism was 5.95 (3.52), 5.37 (3.29), and 4.71 (2.69) dioptres respectively. This difference in the vector corrected change in astigmatism between groups was statistically significant, p values of 0.02, 0.03, and 0.03 respectively. Visual acuity changes were more favourable in the agreement group. Improvement or no change in visual acuity occurred in 90.9% in the agreement group compared with 73.3% of the disagreement group. CONCLUSIONS: Agreement between refraction, keratometry, and topography was associated with greater change in vector corrected astigmatism and was an indicator of good prognosis. Disagreement between refraction, keratometry, and topography was associated with less vector corrected change in astigmatism, a greater probability of decrease in visual acuity, and a relatively poor outcome following suture removal. However, patients in the disagreement group still have a greater chance of improvement than worsening, following suture removal. (+info)Corneal topography by keratometry. (8/329)
AIMS: To investigate the ability of a telecentric keratometer to describe the asphericity and curvature of convex ellipsoidal surfaces and human corneas. METHODS: 22 conicoidal convex surfaces and 30 human corneas were examined by conventional keratometry. Additional keratometric measurements were made when the surface was tilted in the horizontal plane relative to the instrument optical axis. This resulted in a series of radius measurements derived from different regions of the surface. These measurements were used to determine the apical radius and the p value of the horizontal meridian of each surface. The results were compared with those derived from measurements using the EyeSys videokeratoscope and form Talysurf analysis. The method was repeated on 30 human corneas and the results compared with those of a videokeratoscope. RESULTS: For the aspheric buttons, the keratometric and the EyeSys results tended to give higher values for both apical radius and the p values than those of the Talysurf analysis. The best agreement was between the Talysurf and the keratometer where the results were not significantly different. For the human corneas, the apical radii were significantly different comparing the keratometer with the videokeratoscope but the p values were not significantly different. CONCLUSION: The keratometric method for assessing curvature and asphericity appears to hold promise as a method for quantifying the corneal topography. (+info)While there is no cure for keratoconus, there are several treatment options available to help manage the condition. These include eyeglasses or contact lenses, specialized contact lenses called rigid gas permeable (RGP) lenses, and corneal transplantation in severe cases. Other treatments that may be recommended include phototherapeutic keratectomy (PTK), which involves removing damaged tissue from the cornea using a laser, or intacs, which are tiny plastic inserts that are placed into the cornea to flatten it and improve vision.
Keratoconus is relatively rare, affecting about 1 in every 2,000 people worldwide. However, it is more common in certain groups of people, such as those with a family history of the condition or those who have certain medical conditions, such as Down syndrome or sickle cell anemia. It typically affects both eyes, although one eye may be more severely affected than the other.
While there is no known cause for keratoconus, researchers believe that it may be linked to genetics, environmental factors, or a combination of both. The condition usually begins in adolescence or early adulthood and can progress over several years. In some cases, keratoconus can also be associated with other eye conditions, such as cataracts, glaucoma, or retinal detachment.
Astigmatism can occur in people of all ages and is usually present at birth, but it may not become noticeable until later in life. It may also develop as a result of an injury or surgery. Astigmatism can be corrected with glasses, contact lenses, or refractive surgery, such as LASIK.
There are different types of astigmatism, including:
1. Corneal astigmatism: This is the most common type of astigmatism and occurs when the cornea is irregularly shaped.
2. Lens astigmatism: This type of astigmatism occurs when the lens inside the eye is irregularly shaped.
3. Mixed astigmatism: This type of astigmatism occurs when both the cornea and lens are irregularly shaped.
Astigmatism can cause a range of symptoms, including:
* Blurred vision at all distances
* Distorted vision (such as seeing objects as being stretched out or blurry)
* Eye strain or fatigue
* Headaches or eye discomfort
* Squinting or tilting the head to see clearly
If you suspect you have astigmatism, it's important to see an eye doctor for a comprehensive eye exam. Astigmatism can be diagnosed with a visual acuity test and a retinoscopy, which measures the way the light enters the eye.
Astigmatism is a common vision condition that can be easily corrected with glasses, contact lenses, or refractive surgery. If you have astigmatism, it's important to seek professional treatment to improve your vision and reduce any discomfort or strain on the eyes.
Myopia can be caused by a variety of factors, including:
1. Genetics: Myopia can run in families, and people with a family history of myopia are more likely to develop the condition.
2. Near work: Spending too much time doing close-up activities such as reading or using digital devices can increase the risk of developing myopia.
3. Poor posture: Slouching or leaning forward can cause the eye to focus incorrectly, leading to myopia.
4. Nutritional deficiencies: A diet lacking in essential nutrients such as vitamin D and omega-3 fatty acids may contribute to the development of myopia.
5. Eye stress: Prolonged eye strain due to excessive near work or other activities can lead to myopia.
Symptoms of myopia include:
1. Difficulty seeing distant objects clearly
2. Headaches or eye strain from trying to focus on distant objects
3. Squinting or rubbing the eyes to try to see distant objects more clearly
4. Difficulty seeing in low light conditions
5. Blurry vision at a distance, with close objects appearing clear.
Myopia can be diagnosed with a comprehensive eye exam, which includes a visual acuity test, refraction test, and retinoscopy. Treatment options for myopia include:
1. Glasses or contact lenses: These corrective lenses refract light properly onto the retina, allowing clear vision of both close and distant objects.
2. Laser eye surgery: Procedures such as LASIK can reshape the cornea to improve its curvature and reduce myopia.
3. Orthokeratology (ORTHO-K): A non-surgical procedure that uses a specialized contact lens to reshape the cornea while you sleep.
4. Myopia control: This involves using certain treatments or techniques to slow down the progression of myopia in children and young adults.
5. Multifocal lenses: These lenses have multiple focal points, allowing for clear vision of both near and distant objects without the need for glasses or contact lenses.
In conclusion, myopia is a common vision condition that can be caused by a variety of factors and symptoms can include difficulty seeing distant objects clearly, headaches, and eye strain. Treatment options include glasses or contact lenses, laser eye surgery, ORTHO-K, myopia control, and multifocal lenses. It is important to consult an eye doctor for a comprehensive evaluation and to determine the best course of treatment for your specific case of myopia.
1. Keratoconus: This is a progressive thinning of the cornea that can cause it to bulge into a cone-like shape, leading to blurred vision and sensitivity to light.
2. Fuchs' dystrophy: This is a condition in which the cells in the innermost layer of the cornea become damaged, leading to clouding and blurred vision.
3. Bullous keratopathy: This is a condition in which there is a large, fluid-filled bubble on the surface of the cornea, which can cause blurred vision and discomfort.
4. Corneal ulcers: These are open sores on the surface of the cornea that can be caused by infection or other conditions.
5. Dry eye syndrome: This is a condition in which the eyes do not produce enough tears, leading to dryness, irritation, and blurred vision.
6. Corneal abrasions: These are scratches on the surface of the cornea that can be caused by injury or other conditions.
7. Trachoma: This is an infectious eye disease that can cause scarring and blindness if left untreated.
8. Ocular herpes: This is a viral infection that can cause blisters on the surface of the cornea and lead to scarring and vision loss if left untreated.
9. Endophthalmitis: This is an inflammation of the inner layer of the eye that can be caused by bacterial or fungal infections, and can lead to severe vision loss if left untreated.
10. Corneal neovascularization: This is the growth of new blood vessels into the cornea, which can be a complication of other conditions such as dry eye syndrome or ocular trauma.
These are just a few examples of the many different types of corneal diseases that can affect the eyes. It's important to seek medical attention if you experience any symptoms such as pain, redness, or blurred vision in one or both eyes. Early diagnosis and treatment can help prevent complications and preserve vision.
Myopia occurs when the eyeball is too long or the cornea is too steep, causing light to focus in front of the retina instead of directly on it. Hyperopia is the opposite, where the eyeball is too short or the cornea is too flat, causing light to focus behind the retina. Astigmatism is caused by an irregularly shaped cornea, which causes light to focus at multiple points instead of one. Presbyopia is a loss of near vision that occurs as people age, making it harder to see close objects clearly.
In addition to these common refractive errors, there are other, less common conditions that can affect the eyes and cause blurred vision, such as amblyopia (lazy eye), strabismus (crossed eyes), and retinal detachment. These conditions can be caused by a variety of factors, including genetics, injury, or disease.
Refractive errors can have a significant impact on daily life, affecting everything from work and school performance to social interactions and overall quality of life. Fortunately, with the help of corrective lenses or surgery, many people are able to achieve clear vision and lead fulfilling lives.
Corneal topography
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Pellucid marginal degeneration
Feminizing hormone therapy
Astigmatism
Hudson-Stahli line
LASIK
Peter Hersh
Keratoconus
Anastasios John Kanellopoulos
List of examples of lengths
Orders of magnitude (length)
Astigmatism (optical systems)
PiXL
Topography
Tadpole pupil
Refractive surgery
Intraocular lens
TMEM248
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OCT Biomicroscopy
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Orthokeratology
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MeSH Browser
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Keratoconus18
- To present the results after simultaneous photorefractive keratectomy (PRK) followed by corneal collagen cross-linking (CXL) for progressive keratoconus. (keratoconuscanada.org)
- Twelve patients (14 eyes) with progressive keratoconus were prospectively treated with customized topography-guided PRK with the Pulzar Z1 (wavelength 213 nm, CustomVis) immediately followed by corneal collagen CXL with the use of ribofl avin and ultraviolet A irradiation. (keratoconuscanada.org)
- Keratoconus is a progressive corneal disorder that can lead to severe vision deterioration through the development of irregular astigmatism and corneal scarring. (keratoconuscanada.org)
- The irregular astigmatism in keratoconus can be confronted with the use of customized laser ablations that restore the refractive properties of the anterior corneal surface. (keratoconuscanada.org)
- The application of customized topography-guided surface ablation has been reported in patients with stable or subclinical keratoconus with promising visual outcomes.6-8 The disadvantage of ablative procedures is that tissue removal might lead to further destabilization of corneal biomechanics and progression of the ectatic disorder. (keratoconuscanada.org)
- In this case series, we present a new technique and the results of simultaneous customized topography-guided surface ablation followed by CXL in patients with keratoconus. (keratoconuscanada.org)
- Inclusion criteria were progressive keratoconus, hard contact lens and full spectacle correction intolerance, expected central corneal thickness (CCT) after PRK 400 μm, and no other corneal pathological signs. (keratoconuscanada.org)
- Outcomes included severe keratoconus at presentation (steep keratometry ≥52 diopters), disease progression (≥0.75 diopters increase from the first to the most recent clinical visit), and corneal transplantation. (nih.gov)
- Trial rigid lens fitting is considered the best approach to determine whether the correction of residual defocus and irregular astigmatism might improve the visual acuity in patients with corneal disorders including keratoconus. (hindawi.com)
- The pinhole test should be used in patients with corneal diseases such as keratoconus to determine whether optical aberrations associated with the disease cause their visual impairment. (hindawi.com)
- The development of interventions such as cornea crosslinking, photorefractive keratectomy, intrastromal corneal ring segment implantations, and combined treatment provide clinicians with a range of treatment options for visual rehabilitation in patients with keratoconus [ 2 - 4 ]. (hindawi.com)
- 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. (nih.gov)
- Fortunately, corneal collagen cross-linking is FDA-approved and has been shown in hundreds of clinical trials to effectively halt progression of keratoconus in most patients by strengthening the cornea, which stabilizes and often improves the corneal shape. (ophthalmologytimes.com)
- Because progression of keratoconus can occur in any patient, it is important that clinicians follow the corneal shape of patients with keratoconus over time, to help identify progression. (ophthalmologytimes.com)
- Despite extensive knowledge regarding the diagnosis and management of keratoconus and ectatic corneal diseases, many controversies still exist. (lww.com)
- Corneal Collagen Crosslinking - a procedure used for the treatment of early to moderate keratoconus and other types of ectasia that can happen after refractive surgery. (columbiadoctors.org)
- He gave two talks about corneal inlays for the treatment of presbyopia and corneal ring segments for the treatment of keratoconus. (doctorawwad.com)
- Conclusions: The 揃harat� Protocol to arrest keratectasia progression and improve corneal regularity is a safe and efficacious alternative as a keratoconus management option. (who.int)
Cornea10
- A hard contact lens trial may help determine the contribution of corneal aberrations to the patient's decreased vision, although visual disturbances are often the result of the combined effects of the lens and cornea. (aao.org)
- The ability to see the contour of the cornea, the transparent portion of the outer coat of the eyeball is an important tool in the identification of corneal disorders. (uic.edu)
- The keratometer offers a limited evaluation of the cornea and is greatly enhanced by the corneal topography unit. (uic.edu)
- The corneal topography unit projects a series of light rings onto the surface of the cornea. (uic.edu)
- For corneal shape, comparison maps, also called difference maps, can help highlight areas of the cornea that change shape over time. (ophthalmologytimes.com)
- The difference map demonstrated that the steep part of the cornea became steeper, and the flap part of the cornea flattened further, resulting in a significant worsening of irregular corneal astigmatism that resulted in loss of best-corrected vision. (ophthalmologytimes.com)
- If the patient is interested in a presbyopia-correcting or even a toric IOL but the cornea demonstrates corneal staining and irregular topography, I am hyper-aggressive in optimizing the ocular surface. (crstodayeurope.com)
- In my experience, these patients, if compliant, will quickly separate into two groups: those who return with a cornea that is almost completely normalized (objectively and topographically) and those who return with ongoing corneal pathology. (crstodayeurope.com)
- Typically, the more visits that are required to normalize the cornea and topography, the less willing I am to implant a diffractive IOL. (crstodayeurope.com)
- Phototherapeutic keratectomy (PTK) - surgery which can treat recurrent corneal erosions, remove some corneal scarring, and treat certain cornea dystrophies. (columbiadoctors.org)
Thickness3
- Average central corneal thickness is about 550 µm, increasing to about 700 µm in the periphery. (medscape.com)
- The surgeon makes a flap using a femtosecond laser at 30% of the corneal thickness, somewhat deeper than a standard LASIK flap. (crstoday.com)
- INTRODUCTION: Corneal thinning and changes in the corneal thickness profile are major symptoms of corneal ectasia. (bvsalud.org)
Astigmatism4
- Preoperative topography shows minimal astigmatism in the left eye of the patient described in the case example. (aao.org)
- What about posterior corneal astigmatism? (medscape.com)
- For refractive corneal and refractive cataract, surgeons' management of astigmatism is extremely important when it comes to delivering outcomes. (medscape.com)
- In order to treat astigmatism (in cataract surgery), it is important to quantify the amount and regularity of corneal astigmatism, which is best done with either topography or tomography. (medscape.com)
Tomography4
- Screening for corneal irregularities us-ing topography, tomography, or other advanced imaging is recommended in patients considering MF-IOL correc-tion. (aao.org)
- Evaluations should typically include uncorrected and best-corrected visual acuity, refraction, and corneal shape measurements with topography and/or tomography. (ophthalmologytimes.com)
- Tests are the same as LASIK: corneal topography, corneal tomography, and optical or ultrasound pachymetry, as well as evaluation for dry eye including tear osmolarity and meibography. (crstoday.com)
- Each patient underwent a standard ophthalmological examination (visual acuity, tonometry, slit lamp examination, fundus biomicroscopy), a corneal topography with OCULUS Keratograph 5M, and an anterior segment optical coherence tomography with RTVue-100. (bvsalud.org)
Penetrating keratoplasty1
- Therefore, they have been also successfully used to treat other corneal ectasias, including irregular corneas following photorefractive surgery, penetrating keratoplasty, and corneal dystrophies [ 10 - 12 ]. (hindawi.com)
Irregular1
- I believe that patient education is key, so I often rely on visual aids in the clinic, especially irregular corneal topography images, to demonstrate how keratopathy affects the accuracy of IOL calculations. (crstodayeurope.com)
Stromal bed3
- The surgical technique involves the creation of a hinged lamellar corneal flap, after which an excimer laser is used to make a refractive cut on the underlying stromal bed. (medscape.com)
- Pallikaris developed the technique of performing the excimer laser corrective ablation in the corneal stromal bed under a hinged flap. (medscape.com)
- We decided to compare, using atomic force microscopy (AFM), the roughness of the corneal stromal bed, after a femtosecond lasers device flap was created with or without an excimer myopic ablation. (bvsalud.org)
Partial corneal2
- Descemet's stripping endothelial keratoplasty (DSEK) - a partial corneal transplant to treat for corneal edema or swelling. (columbiadoctors.org)
- Besides the indices automatically generated by the software of the device, we measured the following custom parameters: partial corneal area (PCA), partial chamber area (PCA), and an index that reflects the relation between the two (CpC). (bvsalud.org)
Diseases1
- He has been published several times and lectures nationally on various topics including OSD, dry eye, cataract surgery, pharmacology, corneal diseases and LASIK. (aaopt.org)
Ectasia2
- AIM: To determine the diagnostic value of newly developed custom anterior segment OCT indices in diagnosing corneal ectasia. (bvsalud.org)
- PATIENTS AND METHODS: Two sets of patients were included in the current study - healthy controls in the first and patients with corneal ectasia in the second, 80 eyes per group of 43 patients each. (bvsalud.org)
Dystrophies1
- Early and late clinical landmarks of corneal dystrophies. (medlineplus.gov)
Outcomes1
- We analyzed visual outcomes, Scheimpflug topography, and corneal haze evaluation. (who.int)
Ablation2
- Burratto's original work involved performing a corrective excimer laser ablation on the back of a resected disc of corneal tissue. (medscape.com)
- Mittal, Vikas Abstract: Purpose: Outcome of topography?guided excimer laser ablation in conjunction with accelerated, high?fluence cross?linking in corneal ecstatic disease using the NIDEK CXIII equipped with CATz algorithm from the FinalFit software棓Bharat Protocol. (who.int)
Cataract surgery1
- He specializes in corneal and cataract surgery as well as laser refractive surgery. (medscape.com)
Inlays1
- Among the growing number of options that are intended to decrease spectacle dependence-including mono-vision, mini-monovision, accommoda-tive IOLs, corneal inlays, and bioptic re-finements-multifocal IOLs (MF-IOLs) continue to play an important role. (aao.org)
Curvature1
- 2005). Curvature sensor for the measurement of the static corneal topography and the dynamic tear film topography in the human eye . (city.ac.uk)
Refractive surface1
- RGP lenses have the benefit of masking corneal irregularities, thus providing a regular anterior refractive surface [ 10 ]. (hindawi.com)
Correction1
- Campos, Mauro Abstract: Purpose: Compare the safety and efficacy of wavefront?guided photorefractive keratotomy (PRK) 6 months after cross?linking (CXL) to wavefront?guided PRK alone for refractive correction in patients with bilateral asymmetric corneal topography. (who.int)
Placido1
- The workhorse of my evaluation is the OPD-Scan III (Nidek) to assess corneal aberration profiles and Placido disc mires. (crstodayeurope.com)
Lamellar1
- Jose Barraquer is generally credited with much of the early work leading to corneal lamellar refractive procedures as they are currently practiced. (medscape.com)
Aberrations3
- Characterizing corneal aberrations is helpful when selecting IOLs. (aao.org)
- Analysis of corneal aberrations may guide the decision to implant a mono-focal IOL with aspheric offsets (zero or negative) to neutralize spherical aberrations. (aao.org)
- There are many devices that provide topography and concomitant measurement of higher-order aberrations in one capture that are excellent. (crstodayeurope.com)
Transplantation2
Flap2
- However, as currently practiced, it is perhaps best thought of as photorefractive keratectomy (PRK) performed under a flap instead of on the corneal surface. (medscape.com)
- The corneal flap is then replaced. (crstoday.com)
Implant1
- A straightforward corneal implant provides the near vision patients want. (crstoday.com)
Tear film1
- A contact lens exam may include a corneal topography exam and a tear film evaluation, in addition to tests performed during a comprehensive eye exam. (advantagedental.com)
Classification1
- 11. Neural network classification of corneal topography. (nih.gov)
Improves1
- As their corneal health improves (or doesn't), the lens choice becomes clearer. (crstodayeurope.com)
Progression1
- For patients at high risk of progression, cross-linking should be considered as a first step to prevent worsening of the corneal shape, which can lead to permanent visual loss. (ophthalmologytimes.com)
Imaging1
- AFM imaging of the remaining corneal stroma was performed. (bvsalud.org)
IOLs1
- MF-IOLs should not be placed in eyes with significant oph-thalmic comorbidities such as retinop-athy, corneal disease, uveitis, and optic neuropathy. (aao.org)
Patients1
- Two patients in the CXL + PRK group presented corneal haze. (who.int)
Surgical1
- Nonsurgical and surgical treatments for these conditions, including the use of corneal cross-linking and corneal transplantations, were presented in a stepwise approach. (lww.com)
Central2
- Ten different square areas of 20 µm x 20 µm at the central area of the stroma of each corneal sample were studied. (bvsalud.org)
- Conversely, if he had used indentation tonometry, it would not have considered the misclassification resulting from the presence of a thin central corneal (1). (cdc.gov)