Looking for online definition of ocular refraction in the Medical Dictionary? ocular refraction explanation free. What is ocular refraction? Meaning of ocular refraction medical term. What does ocular refraction mean?

The mean prediction error of the refractive outcome obtained in our study was 1.03 D (SD, 0.69 D) for SRK II group and 1.14 D (SD, 1.19 D) in Pediatric IOL Calculator group. This showed both groups ended more myopic than anticipated. However, there was no statistically significant different in the mean prediction error in both groups. Even though, the SRK II group had a lower prediction error of 0.11 D compared to the Pediatric IOL Calculator, we could not prove that SRK II is better than Pediatric IOL Calculator or vice versa. Our results showed that for the overall group, the prediction error is satisfactory and is comparable with errors demonstrated in adult group [21].. In our study, we further divided and analyzed the prediction error according to age group, axial lengths and keratometry. We divided the groups according to the age at time of surgery to less than 3 years old, and equal or older than 3 years old; axial length of less than 22 mm, and equal or more than 22 mm; and keratometry ...

Purpose : To investigate the axial length and corneal radius of curvature (AL/CR) ratio in high versus low myopes and its relationship with myopia progression. Methods : Baseline AL/CR ratio of the right eyes of 310 high myopes (aged 7 to 16; myopia ≤ -6.00D) from the ZOC-BHVI High Myopia Registry (2012- 2013, Guangzhou, China) and 733 low myopes (aged 6 to 16; myopia -0.50D to -3.50D) from Vision CRC studies (2010-2014, Guangzhou, China) were calculated. Exclusion criteria were ocular disease, surgery or previous treatment for myopia. All participants underwent measurement of axial lengths (AL), corneal radii of curvature (CR) and cycloplegic objective refraction. Low myopes were followed 6 monthly for 12 months. Parental myopia was documented. General linear model was used to test the relationship between AL/CR ratio and spherical equivalent (SE) after adjusting for parental myopia, gender, age, and high versus low myopia. The progression in AL/CR ratio with progression in SE was assessed in ...

Baseline J0 data showed an average WTR keratometric astigmatism of 0.85 D and an average ATR internal astigmatism of 0.31 D (Table 1), resulting in WTR refractive astigmatism (J0 +0.54 D). J0 measurements of keratometric and internal astigmatism (Table 4) were positively correlated, indicating a decrease in ATR internal astigmatism with increasing level of ATR keratometric astigmatism. However, correlations were weak, and the relation explained little variability (r2 values , 0.05). Regression analyses predicting baseline refractive astigmatism from keratometric astigmatism provided further evidence of the independence of magnitude of WTR keratometric astigmatism and ATR internal astigmatism (Table 5). The constant and slope in these regressions represent the influence of internal astigmatism. For WTR astigmatism (J0), regression constants were significantly less than 0, reflecting a fixed component of internal compensation. Regression slopes tended to be close to 1 (not significantly different ...

A patients risk of myopia onset can be influenced by various things, including parental myopia, female gender, longer axial length, reduced outdoor time, increased near work time and accommodative insufficiency. Since cycloplegia isnt readily available for most medical practitioners outside of eyecare offices, assessment of spherical equivalent (SE) refraction-commonly used in myopia studies-has limited applicability for other care providers. A recent cohort study observed the performance of SE obtained using non-cycloplegic methods as a predictor of myopia, which would be more accessible across the board for patient assessment. Researchers included 1,022 children aged six to 10 years from two elementary schools in Wenzhou, China. The participants were evaluated at baseline and annual follow-up appointments for three years. The doctors performed non-cycloplegic refraction, ocular biometry and accommodation measurements. A total of 830 of the students were non-myopic at baseline. Two years into ...

Looking for online definition of Complex index of refraction in the Medical Dictionary? Complex index of refraction explanation free. What is Complex index of refraction? Meaning of Complex index of refraction medical term. What does Complex index of refraction mean?

PURPOSE. To examine the association between the anthropometric measurements of height, weight, body mass index (BMI) and refraction and other ocular parameters in Singapore Chinese children. METHODS. In a cross-sectional study of 1449 Chinese school-children, aged 7 to 9 years, from three Singapore schools, height and weight were measured according to standard protocol, and BMI was calculated. Refractive error and corneal curvature measures were determined by autorefraction in eyes under cycloplegia. Axial length, vitreous chamber depth, lens thickness, and anterior chamber depth were measured using A-scan biometry ultrasonography. RESULTS. In comparison with the children with height in the first quartile for a given age and gender, the eyeball length in children in the fourth quartile was 0.46 mm longer, the vitreous chamber depth 0.46 mm deeper, the corneal radius of curvature 0.10 mm greater (i.e., flatter), refraction more negative by 0.47 D (-0.76 D versus -0.29 D), and axial ...

We present parsimonious refraction interferometry and tomography where a densely populated refraction data set can be obtained from two reciprocal and several infill shot gathers. The assumptions are that the refraction arrivals are head waves, and a pair of reciprocal shot gathers and several infill shot gathers are recorded over the line of interest. Refraction traveltimes from these shot gathers are picked and spawned into O(N2) virtual refraction traveltimes generated by N virtual sources, where N is the number of geophones in the 2D survey. The virtual traveltimes can be inverted to give the velocity tomogram. This enormous increase in the number of traveltime picks and associated rays, compared to the many fewer traveltimes from the reciprocal and infill shot gathers, allows for increased model resolution and a better condition number with the system of normal equations. A significant benefit is that the parsimonious survey and the associated traveltime picking is far less time consuming ...

Mean spherical equivalent refraction treated was -6.56±2.74D (range: -2.25 to -13.00D). Median age was 33 years (range: 19 to 66 years). After SMILE, central corneal sensation dropped from 54-mm preoperatively to 32-mm (day one), rising to 40-mm (1 week), 44-mm (1 month), 49-mm (3 months), 54-mm (6 months), and 55-mm (12 months). Corneal sensation had reached baseline by 1, 3, 6, and 12 months in 62%, 76%, 89%, and 90% of eyes respectively. Twenty LASIK studies were identified; central corneal sensation dropped from 56-mm preoperatively to 9-mm (day one), rising to 15-mm (1 week), 22-mm (1 month), 33-mm (3 months), 44-mm (6 months), and 50-mm (12 months). Across the LASIK studies, mean spherical equivalent refraction treated was -4.30D and mean age was 34.2 years ...

PURPOSE: Proper refractive eye growth depends on several features of the visual image and requisite retinal pathways. In this study, we determined the contribution of rod pathways to normal refractive development and form deprivation (FD) myopia by testing Gnat1-/- mice, which lack functional rods due to a mutation in rod transducin-α. METHODS: Refractive development was measured in Gnat1-/- (n = 30-36) and wild-type (WT) mice (n = 5-9) from 4 to 12 weeks of age. FD was induced monocularly from 4 weeks of age using head-mounted diffuser goggles (Gnat1-/-, n = 9-10; WT, n = 7-8). Refractive state and ocular biometry were obtained weekly using a photorefractor, 1310 nm optical coherence tomography, and partial coherence interferometry. We measured retinal dopamine and its metabolite, DOPAC, using HPLC. RESULTS: During normal development, the refractions of WT mice started at 5.36 ± 0.68 diopters (D) and became more hyperopic before plateauing at 7.78 ± 0.64 D. In contrast, refractions in ...

Advanced computerized optical diagnostic equipment is revolutionizing eye care in the 21st century. Refraction is no exception. Traditionally, the refraction of the eye was given with spherical and cylindrical lens powers assumed to be valid across the entire pupil. However, using wavefront sensing, adaptive optics, and new treatment technologies, higher-order aberrations can be measured across the pupil and then modified or eliminated. Research has clearly shown that there are many applications involving these aberrations with diagnosis, treatment, and management of disorders, such as myopia, corneal disorders, presbyopia, cataract, and intraocular lens application and the dynamic changes in refractive state and retinal image quality produced by tear film thinning and accommodation. There are also many related questions that need to be answered regarding the natural stimulus for focusing, the patients perception of the aberrations and their correction, and vision simulation with computational ...

The spherical equivalent before surgery was −4.52 ± 1.96 diopters, falling to −0.22 ± 0.48 diopters after the procedure. Mean uncorrected distance visual acuity post-surgery (UDCVA) was −0.03 ± 0.11 LogMAR. 90.4% achieved UDCVA of at least 0.1 LogMAR (0.8 decimal). 88% showed no refraction one month after surgery and 96.5% had postoperative refraction of ≤0.50 D. Mean asphericity was −0.26 ± 0.19 before surgery and 0.19 ± 0.29 after surgery. Statistically significant differences were found for steep K, flat K, mean K, asphericity, spherical aberration and vertical coma (p < 0.005). On the other hand, no significant differences were found in the Root Mean Square (RMS) for higher order aberrations, horizontal coma or trefoil. Postoperative asphericity correlated strongly with 4th order spherical aberration and vertical coma. Six eyes developed intraoperative complications (confusion between the anterior and posterior planes with stromal damage, loss of suction during the creation of ...

The AOAs stance on these companies prompts the question: Does online refraction actually threaten optometrys model? Consider the lesson of Google Maps.11 Google managed to topple the navigation device market (remember your Tom Tom GPS?) on four main selling points: price, quality, convenience and personalization. Improving on all four of these aspects disrupted the personal navigation device market forever.10 It may be worth discussing with patients whether online refraction companies can beat optometry in any of these selling points. Price. No optometrist would provide a refraction separate from a comprehensive eye exam, explains John Rumpakis, OD, CEO of Practice Resource Management, Inc. However, since thats what these companies are doing, a hypothetical price-by-price comparison may be an appropriate point to discuss with patients. Opternative offers a glasses or contacts prescription for $40 ($60 for both). Although optometry offers a comprehensive exam at an average Medicare ...

This excellent Manual of Refraction has 45 pages and includes the following sections: basic optics visual acuity pinhole refractive errors accommodation presbyopia neutralisation focimetry transposition spherical best sphere equivalent crossed cylinder retinoscopy cycloplegia refraction optical lense basic spectacle dispensing. Price : £5/US$9 + post and packing Post and Packing: Please add £5/$9 (surface) or £9/$16…

PURPOSE: To investigate the association between ocular dominance and refraction. METHODS: A retrospective study of the cycloplegic refraction of 2453 consecutive patients with a mean age of 46 +/- 12 years (range: 18 to 79 years) was performed. One t

A dioptre (uk), or diopter (us), is a unit of measurement of the optical power of a lens or curved mirror, which is equal to the reciprocal of the focal length measured in metres (that is, 1/metres). It is thus a unit of reciprocal length. For example, a 3-dioptre lens brings parallel rays of light to focus at ​1⁄3 metre. A flat window has an optical power of zero dioptres, and does not converge or diverge light. Dioptres are also sometimes used for other reciprocals of distance, particularly radii of curvature and the vergence of optical beams. The usage was proposed by French ophthalmologist Ferdinand Monoyer in 1872, based on earlier use of the term dioptrice by Johannes Kepler. The main benefit of using optical power rather than focal length is that the lensmakers equation has the object distance, image distance, and focal length all as reciprocals. A further benefit is that when relatively thin lenses are placed close together their powers approximately add. Thus, a thin 2-dioptre lens ...

Ray-tracing data are usually given as angles of arrival and departure, transmitter and receiver coordinates, ray length and delay, received power level, and polarity. Usually, these values are given in raw data with some resolution that covers the area of interest where the simulation is performed. There are two main drawbacks of such approach: first, a huge amount of storage capacity is typically needed and second, although the area of interest is covered by a certain resolution, it is nearly impossible to interpolate between sample points and new time, and memory consuming simulations are necessary in order to increase the resolution of the simulations. This paper addresses the two mentioned drawbacks of ray tracing, suggesting a procedure based on the concept of ray entities both to enable continuous interpolation of ray-tracing data and reduce the memory needed for storing data. Ray entity is a set of rays that all undergo the same series of propagation phenomena (direct ray, diffraction, ...

The prevalence rate of myopia is rising rapidly in several Asian countries. A prevalence survey conducted in 1995 of 11178 school children in Taiwan were 12 percent for six year old and 84 percent for teenagers 16 o 18 years. Among them, twenty percent were high myopes. While in the United States and Europe the prevalence rate in older adults is 20% to 50%. The rate of progression of myopia is highest in young children, and the average age of stabilization of myopia is approximately 16 years.The onset of myopia may occur at a relatively young age, leading to higher risks of high myopia (myopia at least 6.0 diopters ) in adulthood. High myopia is associated with potentially blinding complications. Therefore, prevention of myopia progression is important in Taiwan, especially in young children.. There is some evidence that atropine eyedrops retard myopia progression in three randomized clinical trials. It is believed that atropine act on muscarinic receptor located in the sclera and through some ...

Topography & Autorefraction are done at the same time. Topography is a topographical map of your cornea. You may have this done if you have corneal trouble such as Keratoconus or if you have cataracts. Autorefraction provides an objective measurement of your refractive error (the strength glasses you wear). It is particularly important to know your refraction prior and after cataract surgery to calculate the most suitable artificial lens. Currently Medicare does not offer a refund for this vital test.. ...

We have used a modified double-pass apparatus with unequal entrance and exit pupil sizes to measure the optical transfer function in the human eye and have applied the technique to three different problems. First, we confirm that in the eye the double-pass spread function is the cross correlation of the input spread function with the output spread function [ J. Opt. Soc. Am. A 12, 195 ( 1995)]. Consequently, when entrance and exit pupil sizes are equal, phase information is lost from the double-pass images. Second, we show that in double-pass measurements the eye behaves like a reversible optical system. That is, when entrance and exit pupils are equal, the double-pass image results from two passes through an optical system having a transfer function that is the same in both directions. To test for reversibility in the living eye we have used a double-pass apparatus with different exit and entrance pupil sizes (one of them small enough to consider the eye diffraction limited), so that the ...

Case report: A 63 year old female patient consult our clinic for a cataract surgery with IOL implantation. In 1993 she underwent a PRK for her myopia. Her original refraction was 8.0/-0.75/40° at the right eye and -6.75/-0.5/10° at the left eye. As PRK was performed at an other clinic and it was not possible to get any information about keratometry, corneal topography or axial lengt of her eyes before PRK. At her first visit at our eyeclinic her refraction was -3.0/-0.75/18°=20/40 right and -2.75/-0.5/96°=30/50 left. Target refraction after cataract surgery was -2.5 right and -2.5 left. Preoperativly a biometry by IOL-Master® and a corneal topography by C-Scan® were performed. IOL calculation was done with the Oculix-program®. On the first postoperativ day the patient reached a visual acuity of -2.0=40/50 ...

astigmatism - MedHelps astigmatism Center for Information, Symptoms, Resources, Treatments and Tools for astigmatism. Find astigmatism information, treatments for astigmatism and astigmatism symptoms.

Purpose: To investigate whether myopia is becoming more common across Europe and explore whether increasing education levels, an important environmental risk factor for myopia, might explain any temporal trend. Design: Meta-analysis of population-based, cross-sectional studies from the European Eye Epidemiology (E3 ) Consortium. Participants: The E3 Consortium is a collaborative network of epidemiological studies of common eye diseases in adults across Europe. Refractive data were available for 61 946 participants from 15 population-based studies performed between 1990 and 2013; participants had a range of median ages from 44 to 78 years. Methods: Noncycloplegic refraction, year of birth, and highest educational level achieved were obtained for all participants. Myopia was defined as a mean spherical equivalent 0.75 diopters. A random-effects metaanalysis of age-specific myopia prevalence was performed, with sequential analyses stratified by year of birth and highest level of educational ...

The differences that prevail between the cornea that creates the astigmatism and the refractive cylinder that corrects it optically are prevalent and signiftcant, and can play a role in adverse refractive and qualitative outcomes. Addressing these differences during the planning of the surgery provides a uniform paradigm for all astigmatism procedures. Including corneal in addition to refractive values in the treatment plan reduces the amount of overall astigmatism in the eye and provides advantages in outcomes for any corneal refractive astigmatism surgery ...

Screening of refractory defect is one of major reason for amblyopy. Photorefraction is a new method with some advantages in treatment of this problem. In this study the investigators are going to compare the results of this surgery in children between 1 to 10 years old with cycloautorefraction in children above 3 years old ...

In a nearer order from its object, a first lens group which has a negative refractive power, a brightness diaphragm, and a second lens group which has a positive refractive power, and a moving lens group which moves on an optical axis, conditions such as 2≦DL/fW≦6, and −2≦DVH/fW≦0.37 are satisfied under condition that DL (mm) indicates an air-converged length from an end surface near an image in the first lens group to an end surface nearer to an object in the moving lens group, fW (mm) indicates a focal length in an entire system in a wide angle end, DVH (mm) indicates a distance from the end surface near the object in the moving lens group to a front principal point. By doing this, it is possible to provide an objective optical system which can obtain a high magnification while securing a sufficient distance between the diaphragm which is disposed behind the optical axis direction converting element such as a prism to the moving lens group.

I think you will have an easier time viewing the index of refraction from a speed-point of view.. Consider the following: The energy of a given photon is determined by its frequency (color): $E = h \nu $ (h being the Planck constant) Assuming the photon does not lose energy when entering the material, its frequency must be conserved. However, as light is an electromagnetic wave, its propagation in a material differs fundamentally between the vacuum and a crystalline material. In the material, the electric field of the photon will be harder to produce, since the crystals electrons will react to it. The higher the frequency, the stronger this effect is - the light gets increasingly slower. The refractive index for photons with a certain wavelength is $n(\nu) = \frac{c_0}{c_m(\nu)}$ with $c_0$ being the speed of light in vacuum (equal for all wavelengths as far as we know) and $c_m(\nu)$ the speed of a photon of a certain frequency $\nu$ in the material.. Using $c = \lambda \nu$ (and assuming ...

The invention is a method of depositing a rugate filter coating on a substrate, with the coating having an index of refraction that varies with the depth thereof. In detail, the method comprising the steps of: a) placing the substrate in an apparatus capable of depositing the coating by a plasma-enhanced chemical vapor deposition process, the apparatus having the capacity to deposit a coating from a mixture of at least two gases and means to control the mixture of gases as a function of time; b) calculating the required refractive index profile wherein the index of refraction is a function of depth thereof using the filter parameters; c) calculating the required total depth of the coating; d) dividing the total depth of the filter into a series of increments having a specific length; e) calculating the index of refraction for each of the series of increments; f) calculating the specific mixture of the at least two gases required to provide the index of refraction for each of the series of increments and

Fingerprint Dive into the research topics of Numerical simulations of surface wave refraction in the North Sea, part 1: Kinematics. Together they form a unique fingerprint. ...

A modified ray-tracing model is applied to analyze the dependence of external quantum efficiency and far-field radiation pattern of AlGaInN light-emitting

Eye practices are valuable in rectifying an assortment of vision issues. These eye practice methods can redress vision conditions, for example, partial blindness and farsightedness. Eye activities can likewise remedy another vision condition called Astigmatism. Astigmatism is characterized as an eye condition whereby your vision is foggy at any separation. A portion of the reasons for astigmatism incorporates sporadically formed ebb and flow has the cornea or eye focal point. You can read at cloud chasers for other Astigmatism causes incorporate eye damage, and complications related with eye surgery.. High glucose levels and issues related with diabetes are likewise contributing components to this vision condition as to diabetes. Such an issue can prompt the development of an abnormally formed eye focal point. This is related with a condition called Lenticular Astigmatism. The most ideal approach to rectify this issue is to bring glucose levels once more into the ordinary range by and by. ...

This page provides relevant content and local businesses that can help with your search for information on Astigmatism Treatment. You will find informative articles about Astigmatism Treatment, including Astigmatism Symptoms And Treatment. Below you will also find local businesses that may provide the products or services you are looking for. Please scroll down to find the local resources in Aztec, NM that can help answer your questions about Astigmatism Treatment.

This page provides relevant content and local businesses that can help with your search for information on Astigmatism Treatment. You will find informative articles about Astigmatism Treatment, including Astigmatism Symptoms And Treatment. Below you will also find local businesses that may provide the products or services you are looking for. Please scroll down to find the local resources in Fairmont, WV that can help answer your questions about Astigmatism Treatment.

A total of 800 unrelated subjects of Han Chinese ancestry were enrolled in this study, including 300 unrelated individuals with high myopia and 308 emmetropic controls in Guangzhou of other than Chaoshanese origin, and 96 unrelated subjects with moderate to high myopia and 96 emmetropic controls in Guangzhou but from Chaoshan. Two additional cohorts of European ancestry available through dbGAP included 526 unrelated subjects with myopia and 413 emmetropic controls from the KORA cohort and 562 unrelated subjects with myopia and 922 emmetropic controls from the TwinsUK cohort. The baseline characteristics of the subjects are shown in Table 1. The details of the clinical data from individuals of Han Chinese ancestry (Guangzhou and Chaoshan) were described previously [28]. Briefly, the sex and the age between cases and controls were similar, at 50-65% male and with an average age of 21.6-22.2 years. The refraction between the left and right eyes showed no statistical difference. The refraction in ...

0065]The switching point is either a predetermined voltage value or a predetermined optical power value, which is used to determine whether the optical power value is retrieved from the first data table or the second data table. In the case where the switching point is a predetermined voltage value E-set, it is set equal to E-set1 in FIG. 3A (or E-set2 in FIG. 4A), and an optical power level is retrieved from the first data table (or the second data table). In this case, when the signal E-mon1 (or the signal E-mon2) is equal to or higher (or lower) than the voltage value E-set1 (or E-set2), the optical power value retrieved from the first data table (or the second data table) is used as a measured optical power value Pout. On the other hand, when the signal E-mon1 (or the signal E-mon2) is lower (or equal to or higher) than the voltage value E-set1 (or E-set2), the optical power value retrieved from the second data table (or the first data table) is used as a measured optical power value Pout. ...

The effect of myopic defocus on myopia progression was assessed in a two-year prospective study on 94 myopes aged 9{14 years, randomly allocated to an undercorrected group or a fully corrected control group. The 47 experimental subjects were blurred by approximately +0.75 D (blurring VA to 6/12), while the controls were fully corrected. Undercorrection produced more rapid myopia progression and axial elongation (ANOVA, F(1,374)=14.32, p,0.01). Contrary to animal studies, myopic defocus speeds up myopia development in already myopic humans. Myopia could be caused by a failure to detect the direction of defocus rather than by a mechanism exhibiting a zero-point error ...

DR MCQUAID: So the objectives of my talk today are hopefully that when were done here you will, first of all, be able to describe some ways in which to gain a childs trust, so that you can actually make a vision assessment, and perform some retinoscopy or refraction. Id like you to be able to name a few conditions which can be revealed by your first impression of seeing the child, and some very simple binocular assessments. You should be able to explain when were done here why retinoscopy is such an important, vital skill to have when it comes to dealing with children. And then you should also be able to mention a couple of ways to manage pediatric refractive error. So now the thing is - is Im not going to stand up here and teach you how to did retinoscopy or how to do refraction on a child or anybody else. What Im gonna do here is just give you some insight and some quick non-confrontational-type tests, and that sort of thing. Im going to assume that many, if not most of you, at least ...

Results Sphere changed from −1.77±6.57D (−11.00 to 7.00) preoperatively to 0.08±0.79D (−1.25 to 1.75) postoperatively (p=0.211), and cylinder changed from −2.95±1.71D (−7.00 to −0.75) to −1.40±1.13D (−3.25 to 0.00) (p=0.016). UDVA (logMAR) changed from 1.33±0.95 (0.40 to 2.77) to 0.32±0.38 (0.00 to 1.30) (p=0.008) and CDVA (logMAR) changed from 0.32±0.45 (0.01 to 1.77) to 0.20±0.36 (−0.03 to 1.30) (p=0.013). Efficacy and safety indexes were 1.38±0.58 and 1.17±0.66, respectively. Refraction and corneal topography were stable during the follow-up (9.10±5.54 months, 3-15). ...

Purpose: To determine the testability of several vision and refraction tests in preschool-aged children. Design: Population-based study of Chinese preschool-aged children in Singapore. Methods: One thousand five hundred and forty-two Singaporean Chinese children aged 6 to 72 months were recruited through door-to-door screening of government-subsidized apartments in Singapore. Trained eye professionals administered all tests, including monocular logarithm of the minimum angle of resolution visual acuity with the Sheridan Gardiner chart, monocular Ishihara color testing (Richmond Products Inc, Albuquerque, New Mexico, USA), biometric measurements using IOLMaster (Carl Zeiss, Jena, Germany), and Randot stereoacuity (Stereo Optical Co, Chicago, Illinois, USA) for children 30 to younger than 72 months. Cycloplegic refraction and keratometry measurements also were determined using a table-mounted autorefractor (Canon Autorefractor RK-F1; Canon, Tokyo, Japan) in children 24 to younger than 72 months. ...

Results Asymmetry of axial length, corneal power, vitreous chamber depth, anterior chamber depth, lens thickness and lens power were significantly more among participants who were anisometropic than those who were non-anisometropic. The correlation of anisometropia with axial length asymmetry was 0.735, 0.273 with corneal power, 0.183 with anterior chamber depth and 0.311 with lens power (p,0.001). In a multiple linear regression model, anisometropia was found to have significant associations with axial length asymmetry (standard coefficient (SC)=0.905), corneal power asymmetry (SC=0.350), lens power asymmetry (SC=0.454), nuclear opacity asymmetry (SC=0.074) and age (SC=0.28) (R2=85.1%). According to the linear regression model, corneal power had the strongest association with anisoastigmatism.. ...

Yam JC, Jiang Y, Tang SM, Law AKP, Chan JJ, Wong E, Ko ST, Young AL, Tham CC, Chen LJ, Pang CP.. PURPOSE: Low-concentration atropine is an emerging therapy for myopia progression, but its efficacy and optimal concentration remain uncertain. Our study aimed to evaluate the efficacy and safety of low-concentration atropine eye drops at 0.05%, 0.025%, and 0.01% compared with placebo over a 1-year period.. DESIGN: Randomized, placebo-controlled, double-masked trial.. PARTICIPANTS: A total of 438 children aged 4 to 12 years with myopia of at least -1.0 diopter (D) and astigmatism of -2.5 D or less.. METHODS: Participants were randomly assigned in a 1:1:1:1 ratio to receive 0.05%, 0.025%, and 0.01% atropine eye drops, or placebo eye drop, respectively, once nightly to both eyes for 1 year. Cycloplegic refraction, axial length (AL), accommodation amplitude, pupil diameter, and best-corrected visual acuity were measured at baseline, 2 weeks, 4 months, 8 months, and 12 months. Visual Function ...

The mean refractive power of the eye (M) shifted slightly in the myopic direction in downward gaze in the no accommodation condition, consistent with previous findings (Ripple, 1952; Takeda et al., 1992). While the change in mean spherical refractive power was small (about −0.12 D) in magnitude, it was consistent and statistically significant. A study with monkeys observed a downward sag of the crystalline lens during centrally stimulated accommodation, presumably due to the action of gravity (Glasser & Kaufman, 1999). Another recent study reported that anterior chamber depth in human eyes may alter under the influence of gravity due to lens movement (Kasthurirangan, Markwell, Atchison, & Pope, 2011). Therefore, the myopic shift in refractive power in downward gaze that we observed may be the result of a small forward movement of the crystalline lens under the action of gravity. From previously reported modeling, we expect that the crystalline lens would be required to move about 100 μm ...

Myopilux® lenses concept has been validated through two major clinical trials with approximately 600 children, with third party ethics committees approval.. The concept at the heart of Myopilux® Lite and Myopilux® Plus lenses was tested in the Correction of Myopia Evaluation Trial (COMET) study. The purpose was to evaluate the effect of progressive addition lenses (PALs) compared with single vision lenses (SVLs) on the progression of juvenile-onset myopia.[59] A total of 469 children were recruited in this study. The children were randomly assigned to either wearing single vision lenses or PALs with +2.00 D addition. The children were monitored for three years with six monthly follow-up visits. The primary outcome measure was progression of myopia, which was determined by auto-refraction after cycloplegia. The retention rate was extremely high with only 1% dropout rate. At the end of three years, the overall PALs group had a statistically significant reduction of 14% in myopia progression ...

We present the optical models and calculation results of thin-film organic solar cells (OSCs) at oblique incidence of light, using the transfer matrix method. The simple expression for the optical power dissipation is derived at oblique incidence for s- and p-polarized light. The spatial distribution of the electric field intensity, the optical power density, and the optical power dissipation are calculated in both s- and p-polarized light with respect to the incidence angle. We identify how the light absorption efficiency for p-polarized light becomes relatively larger than that for s-polarized light as the incidence angle increases.. © 2012 Optical Society of Korea. PDF Article ...

OPHTHALMOLOGY ORTHOPTIST. SYLLABUS Ist SEMESTER:. Anatomy of eye. Physiology of eye General consideration of different terms used in ophthalmology.. Common diseases of eyelids Common diseases of conjunctiva Common diseases of cornea Common diseases of sclera - Common diseases of lens & silliary body. Glaucoma - Cataract Orbit Examination of eye. Special investigation of eye. Demonstrations- on above subjects. IInd SEMESTER: - Visual acuity Amplitude of accommodation. Colour vision Principle of Retinoscopy. Static refractions Subjective refractions Errors of refraction * Myopia * Hypermetropia. * Astigmatism Aphlcia Presbyopia. Anisometropia Anisokomia IIIrd SEMESTER: - Accommodation & Convergene.. Heterophoria. Measurement of phoria s ________. Principles & therapy of squint. less charting. Diplopia charting.. Orthoptic exercises. Pleoptics. ...

PURPOSE: This work investigates how short-term changes in blood glucose concentration affect the refractive components of the diabetic eye in patients with long-term Type 1 and Type 2 diabetes. METHODS: Blood glucose concentration, refractive error components (mean spherical equivalent MSE, J0, J45), central corneal thickness (CCT), anterior chamber depth (ACD), crystalline lens thickness (LT), axial length (AL) and ocular aberrations were monitored at two-hourly intervals over a 12-hour period in: 20 T1DM patients (mean age ± SD) 38±14 years, baseline HbA1c 8.6±1.9%; 21 T2DM patients (mean age ± SD) 56±11 years, HbA1c 7.5±1.8%; and in 20 control subjects (mean age ± SD) 49±23 years, HbA1c 5.5±0.5%. The refractive and biometric results were compared with the corresponding changes in blood glucose concentration. RESULTS: Blood glucose concentration at different times was found to vary significantly within (p,0.0005) and between groups (p,0.0005). However, the refractive error components ...

TY - JOUR. T1 - Comparison of refractive outcomes using immersion ultrasound biometry and IOLMaster biometry. AU - Landers, John. AU - Goggin, Michael. PY - 2009. Y1 - 2009. M3 - Article. VL - 37. SP - 566. EP - 569. JO - Clinical and Experimental Ophthlamology. JF - Clinical and Experimental Ophthlamology. SN - 1442-9071. IS - 6. ER - ...

People can be born with astigmatism - in fact, most people probably are born with some degree of astigmatism - and they may have it along with other refractive errors: nearsightedness (myopia) or farsightedness (hyperopia).. While adults with a higher degree of astigmatism may realize their vision isnt as good as it should be, children who have astigmatism symptoms may not be aware they have this condition, and are unlikely to complain about blurred or distorted vision. But uncorrected astigmatism can seriously impact a childs ability to achieve in school and sports. And some forms of astigmatism can be a sign of keratoconus, a cone-like bulge of the cornea, which can distort vision. Thats why it is crucial that children have regular eye exams to detect astigmatism or other vision problems as early as possible.. fonte: https://www.aao.org/eye-health/diseases/what-is-astigmatism. ...

The ability of the crystalline lens to change shape and bring near objects into focus is known as accommodation. Over time, the deformability of the lens decreases, deteriorating near visual function. This condition is known as presbyopia. There are many ways in which presbyopia correction is addressed, but currently there does not exist a method capable of restoring a dynamic visual range. In order to better understand the accommodative process and evaluate future corrective approaches, we require a system capable of dynamically acquiring refraction and biometric information. The goal of this work was to design, develop, and test a system that is capable of measuring dynamically the optical and physical changes that occur in the eye during stimulated accommodation. The system consists of: a high dynamic range Shack-Hartmann based autorefractor, an extended-depth spectral domain optical coherence tomography (SD-OCT) system for anterior segment imaging, a 1300 nm SD-OCT system for trans-scleral ciliary

The longer the mean axial length in both eyes, the greater the differences in axial length, mean keratometry, anterior chamber depth, and corneal astigmatism in both eyes. This outcome is assumed to be attributable to the difference in axial length. It was observed that the longer the axial length in one eye, the deeper the anterior chamber depth, and the flatter the mean keratometry value, the greater the corneal astigmatism. The anterior chamber depth was shallower and the mean keratometry value increased with increasing age, whereas corneal astigmatism tended to decrease until the patients were in their sixth decade, but increased afterward ...

Myopia progression is the progressive increase in the amount of nearsightedness in children due to eyeball elongation (axial elongation).

The predictability and self-reported clarity of vision of wavefront-guided LASIK were better with the small-spot scanning laser than with a variable-spot scanning laser, according to a study. C.Q. Yu and E.E. Manche prospectively compared LASIK outcomes between two wavefront-guided excimer laser systems in the treatment of myopia in 100 eyes of 50 patients. One eye of patients was treated with the Allegretto Wave Eye-Q system (small-spot scanning laser, Alcon, Fort Worth, Texas) and the fellow eye with the VISX Star CustomVue S4 IR system (variable-spot scanning laser, Abbott Medical Optics, Santa Ana, Calif.). The mean preoperative spherical equivalent refraction was -3.89 D1.67 D and -4.18 D1.73 D in the small-spot scanning laser group and variable-spot scanning laser group, respectively. There were no significant differences in preoperative higher order aberrations between the groups. At 12 months postoperatively, all eyes in the small-spot scanning laser group and 92% in the variable-spot ...

VA and CS are, of course, not directly comparable, as benefits at a particular low spatial frequency may not result in improvements in a VA task; this would depend upon whether or not observers used information at that spatial frequency in making their decision in the VA task. The high spatial frequency cutoff of the CS function (usually only detectable at 100% contrast) can be considered the grating acuity limit (expressed in MAR) (Thorn & Schwartz, 1990). Unfortunately, previous studies that looked at CS after AO correction did not measure CS out to the high spatial frequency cutoff. Liang et al. (1997) approached it by measuring out to 55 cpd, but Yoon and Williams (2002) only tested out to 32 cpd. If they had, it is likely that they would have found a higher spatial frequency cutoff after AO correction than before (as Liang et al., 1997, did). The modest improvements found in VA may be due to the fact that letter acuity is more sensitive than grating acuity to changes in resolution resulting ...

To compare the outcomes of intraoperative wavefront aberrometry versus optical biometry alone for intraocular lens (IOL) power calculation in eyes undergoing cataract surgery with monofocal IOL implantation.. Preoperative data were obtained with the IOLMaster. Intraoperative aphakic measurements and IOL power calculations were obtained in some patients with the optiwave refractive analysis (ORA) system. Analysis was performed to determine the accuracy of monofocal IOL power prediction and postoperative manifest refraction at 1 month of the ORA versus IOLMaster.. Two hundred and ninety-five eyes reviewed, 61 had only preoperative IOLMaster measurements and 234 had both IOLMaster and ORA measurements. Of these 234 eyes, 6 were excluded, 107 had the same recommended IOL power by ORA and IOLMaster. Sixty-four percent of these eyes were within ±0.5D. 95 eyes had IOL power implantation based on ORA instead of IOLMaster. Seventy percent of these eyes were within ±0.5D of target refraction. 26 eyes ...

MYOPIA is a REFRACTIVE ERROR disturbing the clear focus of distant objects caused by a combination of the eye being too long, or the cornea - lens focusing too strongly.. Myopia is also called Nearsightedness and can be treated with minus, concave spectacles or contact lenses.. Refractive errors change with age. In many children, especially those with myopic parents, and this children who spend lots of time indoors looking at near objects, or text-books, myopia may progress substantially through the teen years.. ...

Cost: Free. Optogenetics continues to be one of the easiest ways to directly and quickly manipulate the behavior of cells, and the lasers necessary to employ this method are often inexpensive and easy to find. However, an essential yet sometimes overlooked step is making sure that your laser is emitting an accurate power of light. The Optical Power Meter app, combined with a Bluetooth-enabled physical power meter, offers an interesting solution to making sure your lasers are firing at the correct wattage. The app connects to the PM160 device wirelessly, allowing users to seamlessly measure the optical power of their laser. The advantage of this device over typical power meters is that the app allows you to record, save, and upload your readings, making it easier than ever to keep an eye on how stable your laser is over time.. ...

Part physics, part material science and part chemistry, refractometry is the process which measures the composition of known substances by means of calculating their respective refractive indexes (RI). RIs are evaluated via a refractometer, a device which measures the curve, or refraction, resulting when the wavelength of light moves from the air into and through a tested substance. The unitless number given by the refractometer, usually between 1.3000 and 1.7000, is the RI. The composition of substances is then determined when the RI is compared to a standard curve specific to the material of the substance ...

The clinical characteristics of the study subjects are shown in Table 2 and Figure 1. Although there was a slight preponderance of men (about 65%) in the myopia and control groups from Chaoshan, only about 49% of the Han Chinese patients with myopia were male as opposed to 64% of the control group. The ages of the patients and controls in both groups were similar, averaging about 21.6-22.2 years old (Table 2). Although the diagnosis of high myopia in this study was based on refraction, the axial lengths of patients with myopia in the Chaoshan and Guangzhou groups were similar, about 26 mm, while those of the controls in both groups averaged between 23 and 24 mm. The refraction in diopters was also similar between patients in both groups, although the mean was slightly higher (−6.52 OD, −6.37 OS) in the Chaoshan group than in the Guangzhou group (−7.28 OD, −7.20 OS); the values for the controls from both groups were close to 0. All markers were in Hardy-Weinberg equilibrium (p,0.05) in ...

An objective lens system for endoscopes comprising, in the order from the object side, a first lens component having a negative refractive power, a second lens component having a positive refractive power, an aperture stop arranged right after the second lens component, and a rear lens unit comprising a third lens component designed as a cemented doublet consisting of a lens element having a positive refractive power and a lens element having a negative refractive power. Said objective lens system for endoscopes has a wide field angle, a compact design, a small number of lens elements and favorably corrected aberrations.

On ophthalmological examination at presentation, uncorrected visual acuity was 20/20 in the right eye and 20/250 in the left eye. Manifest refraction was −3.00 −2.00 x 162 in the left eye, resulting in a best-corrected visual acuity of 20/60, and −0.05 −2.50 x 149 in the right eye. Figure 1 shows the curvature with marked central corneal steepening in the left eye. The keratometry was 46.17/43.44 D in the right eye and 49.20/45.61 D in the left eye, with central corneal thickness (CCT) of 396 um in the right eye and 374 um in the left eye. Attempts to lower the patient fs IOP with brimonidine on the left showed no change in corneal topography. ICRSs (Intacs; Addition Technology, Sunnyvale, CA) were implanted in the left eye using the femtosecond laser for tunnel creation. Two standard segment implants of 400 um (7.0 mm optical zone) were placed at axis 60, with a tunnel depth of 400 um. The implants resulted in some improvement (see Table 1 for visual and keratometric results), but the ...

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Optical Power vs. Voltage. The optical power (ability of a lens to converge or diverge light) of Corning® Varioptic® Lenses is a linear response versus voltage. See graph on the right.. The relation between optical power (OP, in diopters) and focusing distance (d, in meters) is given by: OP = 1/d. Optical Quality. The optical quality of each adjustable lens is specified by the Wave Front Error (WFE). The WFE characterizes the deviation of the actual shape of the lens compared to a perfectly spherical lens (aberrations) - and measured in nanometers rms. The typical WFE of the lens is in the range of 50 nm rms, which is the equivalent of a lambda/10 lens for visible light, commonly accepted as a high-quality grade lens. ...

Ebook `The refraction of the eye; including a complete treatise on ophthalmometry; a clinical text-book for students and practitioners`: ebooks list of Achilles Edward Davis