Influence of the prediction error of the first eye undergoing cataract surgery on the refractive outcome of the fellow eye

Introduction

In addition to measurement errors, individual anatomical conditions could be made responsible for unexpected prediction errors in the determination of the correct intraocular lens power for cataract surgery. Obviously, such anatomical conditions might be relevant for both eyes. The purpose of this study was to evaluate whether the postoperative refractive error of the first eye has to be taken in account for the biometry of the second.

Methods

In this retrospective study, we included 670 eyes of 335 patients who underwent phacoemulsification and implantation of a foldable intraocular lens in both eyes. According to the SRK/T formula, the postoperative refractive error of each eye was determined and compared with its fellow eye.

Results

Of 670 eyes, 622 showed a postoperative refractive error within ±1.0 D (93%), whereas the prediction error was 0.5 D or less in 491 eyes (73%). The postoperative difference between both eyes was within 0.5 D in 71% and within 1.0 D in 93% of the eyes. Comparing the prediction error of an eye and its fellow eye, the error of the fellow eye was about half the value of the other.

Conclusion

Our results imply that substitution of half of the prediction error of the first eye into the calculation of the second eye may be useful to reduce the prediction error in the second eye. However, prospective studies should be initiated to demonstrate an improved accuracy for the second eye’s intraocular lens power calculation by partial adjustment.

Refractive errors in a Brazilian population: age and sex distribution

PURPOSE

To determine the prevalence of refractive errors and their distribution according to age and sex in a Brazilian population.

METHODS

This population-based cross-sectional study involved 7654 Brazilian inhabitants of nine municipalities of Sao Paulo State, Brazil, between March 2004 and July 2005. Participants aged >1 year were selected using a random, stratified, household cluster sampling technique, excluding individuals with previous refractive or cataract surgery. Myopia was defined as spherical equivalent (SE) ≤-0.5D, high myopia as SE ≤-3.0D, hyperopia as SE ≥+0.5D, high hyperopia as SE ≥+3D, astigmatism as ≤-0.5DC and anisometropia as ≥1.0D difference between eyes. Age, sex, complaints and a comprehensive eye examination including cycloplegic refraction test were collected and analysed using descriptive analysis, univariate and multivariate methods.

RESULTS

The prevalence of astigmatism was 59.7%, hyperopia 33.8% and myopia was 25.3%. Astigmatism had a progressive increase with age. With-the-rule (WTR) axes of astigmatism were more frequently observed in the young participants and the against-the-rule (ATR) axes were more frequent in the older subjects. The onset of myopia occurred more frequently between the 2nd and 3rd decades of life. Anisometropia showed a prevalence of 13.2% (95% CI 12.4-13.9; p < 0.001). There was an association between age and all types of refractive error and hyperopia was also associated with sex. Hyperopia was associated with WTR axes (odds ratio 0.73; 95% CI: 0.6-0.8; p < 0.001) and myopia with ATR axes (odds ratio 0.66; 95% CI: 0.6-0.8; p < 0.001).

CONCLUSIONS

Astigmatism was the most prevalent refractive error in a Brazilian population. There was a strong relationship between age and all refractive errors and between hyperopia and sex. WTR astigmatism was more frequently associated with hyperopia and ATR astigmatism with myopia. The vast majority of participants had low-grade refractive error, which favours planning aimed at correction of refractive error in the population.

Comprehensive replication of the relationship between myopia-related genes and refractive errors in a large Japanese cohort

PURPOSE

We investigated the association between refractive error in a Japanese population and myopia-related genes identified in two recent large-scale genome-wide association studies.

METHODS

Single-nucleotide polymorphisms (SNPs) in 51 genes that were reported by the Consortium for Refractive Error and Myopia and/or the 23andMe database were genotyped in 3712 healthy Japanese volunteers from the Nagahama Study using HumanHap610K Quad, HumanOmni2.5M, and/or HumanExome Arrays. To evaluate the association between refractive error and recently identified myopia-related genes, we used three approaches to perform quantitative trait locus analyses of mean refractive error in both eyes of the participants: per-SNP, gene-based top-SNP, and gene-based all-SNP analyses. Association plots of successfully replicated genes also were investigated.

RESULTS

In our per-SNP analysis, eight myopia gene associations were replicated successfully: GJD2, RASGRF1, BICC1, KCNQ5, CD55, CYP26A1, LRRC4C, and B4GALNT2.Seven additional gene associations were replicated in our gene-based analyses: GRIA4, BMP2, QKI, BMP4, SFRP1, SH3GL2, and EHBP1L1. The signal strength of the reported SNPs and their tagging SNPs increased after considering different linkage disequilibrium patterns across ethnicities. Although two previous studies suggested strong associations between PRSS56, LAMA2, TOX, and RDH5 and myopia, we could not replicate these results.

CONCLUSIONS

Our results confirmed the significance of the myopia-related genes reported previously and suggested that gene-based replication analyses are more effective than per-SNP analyses. Our comparison with two previous studies suggested that BMP3 SNPs cause myopia primarily in Caucasian populations, while they may exhibit protective effects in Asian populations.

The effects of simultaneous dual focus lenses on refractive development in infant monkeys

PURPOSE

We investigated the effects of two simultaneously imposed, competing focal planes on refractive development in monkeys.

METHODS

Starting at 3 weeks of age and continuing until 150 ± 4 days of age, rhesus monkeys were reared with binocular dual-focus spectacle lenses. The treatment lenses had central 2-mm zones of zero power and concentric annular zones with alternating powers of +3.0 diopter [D] and plano (pL or 0 D) (n = 7; +3D/pL) or -3.0 D and plano (n = 7; -3D/pL). Retinoscopy, keratometry, and A-scan ultrasonography were performed every 2 weeks throughout the treatment period. For comparison purposes data were obtained from monkeys reared with full field (FF) +3.0 (n = 4) or -3.0 D (n = 5) lenses over both eyes and 33 control animals reared with unrestricted vision.

RESULTS

The +3 D/pL lenses slowed eye growth resulting in hyperopic refractive errors that were similar to those produced by FF+3 D lenses (+3 D/pL = +5.25 D, FF +3 D = +4.63 D; P = 0.32), but significantly more hyperopic than those observed in control monkeys (+2.50 D, P = 0.0001). One -3 D/pL monkey developed compensating axial myopia; however, in the other -3 D/pL monkeys refractive development was dominated by the zero-powered portions of the treatment lenses. The refractive errors for the -3 D/pL monkeys were more hyperopic than those in the FF -3 D monkeys (-3 D/pL = +3.13 D, FF -3D = -1.69 D; P = 0.01), but similar to those in control animals (P = 0.15).

CONCLUSIONS

In the monkeys treated with dual-focus lenses, refractive development was dominated by the more anterior (i.e., relatively myopic) image plane. The results indicate that imposing relative myopic defocus over a large proportion of the retina is an effective means for slowing ocular growth.

Effects of dopaminergic agents on progression of naturally occurring myopia in albino guinea pigs (Cavia porcellus)

PURPOSE

Disruption of dopaminergic signaling has been implicated in the abnormalities of ocular development in albinism, and many experiments have shown that retinal dopamine is a major regulator of postnatal eye growth and myopia in animal models. Therefore, in the present study we investigated whether progressive myopia, which can occur in albino guinea pigs without experimental manipulation of visual conditions, is affected by dopaminergic agents.

METHODS

Two-week-old albino guinea pigs, selected for being myopic (range refractive error [RE], -2 to -10 diopters [D]), received unilateral peribulbar injections of apomorphine (nonselective dopamine receptor agonist; 0, 7.5, 25, 75, 250, 750, and 2500 ng; n = 112), SKF38393 (D1-like agonist; 0, 10, 100, 1000 ng; n = 63), SCH23390 (D1-like antagonist; 0, 2500 ng; n = 27), quinpirole (D2-like agonist; 0, 10, 100, 1000 ng; n = 58), or sulpiride (D2-like antagonist; 0, 2500 ng; n = 24) once a day for four weeks. One noninjected group (n = 19) served as untreated control. Refractive states and axial dimensions of the eyes were measured without cycloplegia or general anesthetic, using eccentric infrared photoretinoscopy and A-scan ultrasonography, respectively, before treatment, and after 2 and 4 weeks of treatment. The main drug effects were analyzed by paired t-test or 2-way repeated measures ANOVA, as required.

RESULTS

The naturally occurring progression of myopic RE was inhibited by apomorphine at relatively high doses (250 and 750 ng), SKF38393 at 100 ng (D1-like agonist), and sulpiride at 2500 ng (D2-like antagonist), but promoted by apomorphine at a lower dose (25 ng), quinpirole at 100 ng (D2-like agonist), and SCH23390 at 2500 ng (D1-like antagonist). All drugs affected primarily vitreous chamber depth, rather than anterior segment dimensions.

CONCLUSIONS

Our data suggest that the activation of D1-like receptors inhibits, whereas activation of D2-like receptors promotes, progressive myopia in this animal model. The robust effects of antagonists suggest that ocular dopamine receptors in these albinos may be in a chronic state of partial excitation. The precise location and identity of the receptors responsible for these effects remain to be determined.

Prevalence of refractive error, presbyopia and spectacle coverage in Kahama District, Tanzania: a rapid assessment of refractive error

BACKGROUND

In Tanzania, the prevalence of refractive error and presbyopia have not been comprehensively assessed, limiting appropriate planning and implementation of delivery of vision care. This study sought to determine the prevalence of refractive error and presbyopia, spectacle coverage and the barriers to uptake of refractive services in people aged 15 years and older in the Kahama district of Tanzania.

METHODS

A cross-sectional community-based survey was conducted using 54 randomly selected clusters. Respondents 15 years and older were interviewed and underwent standardised clinical eye examinations. Uncorrected refractive error (URE) was defined as presenting vision worse than 6/12 that could be corrected to better than 6/12 using a pinhole. Spectacle coverage was defined as the proportion of need that was met (those that improved from unaided vision with their own spectacle correction).

RESULTS

A total of 3,230 subjects (99.75 per cent of 3,240 eligible) participated in the study with 57.2 per cent males and the median age of participants was 35 years (inter-quartile range, 24 to 49). The prevalence of visual impairment was 10.4 per cent (95% CI 9.4 to 11.4) and was lower in those who had completed their primary school education (odds ratio (OR) 0.54, 95% CI: 0.40 to 0.72) and highest in subjects 40 years and older (OR 3.17, 95% CI: 2.14 to 4.70) and farmers (OR 8.57 95% CI: 2.27 to 32.43). Refractive error prevalence was 7.5 per cent (95% CI: 6.65 to 8.54) and this was highest in participants over 40 years (OR 1.60, 95% CI: 1.14 to 2.25) and in students (OR 3.64, 95% CI: 1.35 to 9.86). Prevalence of presbyopia was 46.5 per cent (773/1,663, 95% CI: 44.34 to 48.75). Spectacle coverage for refractive error and presbyopia was 1.69% (95% CI: 0 to 3.29) and 0.42% (95% CI: 0 to 1.26), respectively.

CONCLUSION

Uncorrected refractive error is a public health challenge in the Kahama district and sustainable service delivery and health promotion efforts are needed.

Racial disparities in uncorrected and undercorrected refractive error in the United States

PURPOSE

To identify risk factors for inadequately corrected refractive error in the United States.

METHODS

This cross-sectional study included 12,758 participants 12 years of age and older from the 2005 to 2008 National Health and Nutrition Examination Survey. The primary outcome was the proportion of individuals with inadequate refractive correction for whom refractive correction would result in a visual acuity of 20/40 or better. The primary predictor was race/ethnicity. Secondary predictors included age, sex, annual household income, education, insurance, type of refractive error, current corrective lens use, presenting and best corrected visual acuity, cataract surgery, glaucoma, and age-related macular degeneration.

RESULTS

Overall, 50.6% of subjects had a refractive error which was correctable to 20/40 or better with refraction. The percentage of subjects with correctable refractive error who were inadequately corrected was 11.7%. Odds of inadequate refractive correction were significantly greater in Mexican Americans and non-Hispanic blacks than in their non-Hispanic white counterparts in all age groups, with the greatest disparity in the 12- to 19-year-old group. Other risk factors associated with inadequate refractive correction in adults but not in teenagers included low annual household income, low education, and lack of health insurance.

CONCLUSIONS

Racial disparities in refractive error correction were most pronounced in those under 20 years of age, as well as in adults with low annual household income, low education level, and lack of health insurance. Targeted efforts to provide culturally appropriate education, accessible vision screening, appropriate refractive correction, and routine follow-up to these medically underserved groups should be pursued as a public health strategy.

Ocular morbidity among street children in Kathmandu Valley

PURPOSE

Prevalence of ocular morbidity among street children is largely unknown. The present study was carried out to determine the prevalence of ocular morbidity among street children in the Kathmandu Valley.

METHODS

A cross-sectional study consisting of an eye examination program among 569 street children aged younger than 18 years was conducted from March 2013 to February 2014. Children were included from 11 safe houses of 6 non-governmental organizations and an independent eye camp. Eye examination included visual acuity testing, anterior segment and posterior segment examination, retinoscopy and refraction, cover test, convergence, accommodation and color vision tests. Chi-square test was used to analyze the association of ocular morbidity with age, sex and living conditions.

RESULTS

The majority of children (43.8%) were in the age group of 12-15 years, and the male to female ratio was 3.9:1. Uncorrected and best-corrected visual acuity ≥6/9 in at least one eye was found in 89.8% and 98.4% of children, respectively. Total ocular morbidity was observed at 31.6%. The most common types of ocular morbidity were conjunctivitis (11.0%) and refractive error (11.6%). Ocular morbidity was more common in children over 15 years of age (40.9%; p < 0.01; odds ratio 1.8).

CONCLUSIONS

Ocular infection and refractive error represent the most common ocular morbidities in street children in the Kathmandu Valley.

Macular choroidal thicknesses in healthy adults--relationship with ocular and demographic factors

PURPOSE

To determine the differences in choroidal thickness (CT) among different groups of refractive errors and axial lengths, and to describe the rates of change of CT with ocular and demographic factors in various regions of the macula.

METHODS

Prospective cohort study of 150 healthy volunteers. Spectral-domain optical coherence tomography was performed on both eyes using a standardized imaging protocol. Manual grading of the choroidal boundaries was independently performed by trained graders to determine Early Treatment Diabetic Retinopathy Study (ETDRS) subfield choroidal thickness. Multiple linear regression analyses were performed to determine the effects of spherical equivalent, axial length and age on choroidal thickness in each subfield.

RESULTS

The mean central subfield CT was 324.9 μm (range, 123-566 μm) and varied significantly with both spherical equivalent (P < 0.001) and axial length (P < 0.001), but not age or sex. On multiple linear regression analysis using spherical equivalent, the coefficients were 20.0 for the central subfield, ranged from 16.9 to 19.9 for the inner subfields, and decreased to 13.9 to 16.2 for the outer subfields. Performing regression analysis using axial length, the coefficients were -36.4 for the central subfield, -30.5 to -34.5 for the inner subfields, and -24.6 to -27.3 for the outer subfields.

CONCLUSIONS

Choroidal thickness varies significantly with spherical equivalent and axial length in all regions of the macula, but exhibits different rates of change among different subfields. The rates of change were greater in the central and inner subfields compared with the outer subfields.

Axial eye growth and refractive error development can be modified by exposing the peripheral retina to relative myopic or hyperopic defocus

PURPOSE

Bifocal contact lenses were used to impose hyperopic and myopic defocus on the peripheral retina of marmosets. Eye growth and refractive state were compared with untreated animals and those treated with single-vision or multizone contact lenses from earlier studies.

METHODS

Thirty juvenile marmosets wore one of three experimental annular bifocal contact lens designs on their right eyes and a plano contact lens on the left eye as a control for 10 weeks from 70 days of age (10 marmosets/group). The experimental designs had plano center zones (1.5 or 3 mm) and +5 diopters [D] or -5 D in the periphery (referred to as +5 D/1.5 mm, +5 D/3 mm and -5 D/3 mm). We measured the central and peripheral mean spherical refractive error (MSE), vitreous chamber depth (VC), pupil diameter (PD), calculated eye growth, and myopia progression rates prior to and during treatment. The results were compared with age-matched untreated (N=25), single-vision positive (N=19), negative (N=16), and +5/-5 D multizone lens-reared marmosets (N=10).

RESULTS

At the end of treatment, animals in the -5 D/3 mm group had larger (P<0.01) and more myopic eyes (P<0.05) than animals in the +5 D/1.5 mm group. There was a dose-dependent relationship between the peripheral treatment zone area and the treatment-induced changes in eye growth and refractive state. Pretreatment ocular growth rates and baseline peripheral refraction accounted for 40% of the induced refraction and axial growth rate changes.

CONCLUSIONS

Eye growth and refractive state can be manipulated by altering peripheral retinal defocus. Imposing peripheral hyperopic defocus produces axial myopia, whereas peripheral myopic defocus produces axial hyperopia. The effects are smaller than using single-vision contact lenses that impose full-field defocus, but support the use of bifocal or multifocal contact lenses as an effective treatment for myopia control.

Generational difference of refractive error and risk factors in the Handan Offspring Myopia Study

PURPOSE

To report the refractive error difference (RED) between parents and their children, and its risk factors, in a rural area of China.

METHODS

Children (6-17 years) and their parents (36.2 ± 4.1 years) from the Handan Offspring Myopia Study (HOMS) were enrolled. Cycloplegic autorefraction (cyclopentolate 1%, Topcon KR8800) of the children and noncycloplegic autorefraction of their parents were assessed. A detailed vision-based questionnaire was also completed. Refractive error difference was defined as the difference between the parental spherical equivalent (SE) and their children's SE. Generational myopic shift was defined as the estimated RED when a child would be 18 years old according to a prediction model.

RESULTS

Three hundred fifty-six pairs of parents and 585 children were enrolled. The RED (median, quartiles) increased from -1.33 (-1.99, -0.98) diopters (D) in children aged 6 to 7 years to 0.81 (-0.16, 2.28) D in children aged 16 to 17 years. The children's SE was predicted to approach the parental SE at 14 years of age. Moreover, the children's estimated myopic shift would be 1.03 D. Multiple linear regression revealed that older children (β = 0.23 D/y, P < 0.0001) and girls (β = 0.24, P = 0.01) tended to have a higher RED.

CONCLUSIONS

In this rural Chinese population, the children's refraction was estimated to be similar to the parental refraction at 14 years of age. Moreover, the generational myopic shift was estimated to be approximately 1 D at 18 years of age. These data suggest that the generational difference reflects the increasing prevalence of myopia in the younger generation, which is likely due to changes in environmental exposure.

Uncorrected refractive error and associated factors among primary school children in Debre Markos District, Northwest Ethiopia

BACKGROUND

Uncorrected Refractive Error is one of the leading cause amblyopia that exposes children to poor school performance. It refrain them from productive working lives resulting in severe economic and social loses in their latter adulthood lives. The objective of the study was to assess the prevalence of uncorrected refractive error and its associated factors among school children in Debre Markos District.

METHOD

A cross section study design was employed. Four hundred thirty two students were randomly selected using a multistage stratified sampling technique. The data were collected by trained ophthalmic nurses through interview, structured questionnaires and physical examinations. Snellens visual acuity measurement chart was used to identify the visual acuity of students. Students with visual acuity less than 6/12 had undergone further examination using auto refractor and cross-checked using spherical and cylindrical lenses. The data were entered into epi data statistical software version 3.1 and analyzed by SPSS version 20. The statistical significance was set at α ≤ 0.05. Descriptive, bivariate and multivariate analyses were done using odds ratios with 95% confidence interval.

RESULT

Out of 432 students selected for the study, 420 (97.2%) were in the age group 7-15 years. The mean age was 12 ± 2.1SD. Overall prevalence of refractive error was 43 (10.2%). Myopia was found among the most dominant 5.47% followed by astigmatism 1.9% and hyperopia 1.4% in both sexes. Female sex (AOR: 3.96, 95% CI: 1.55-10.09), higher grade level (AOR: 4.82, 95% CI: 1.98-11.47) and using computers regularly (AOR: 4.53, 95% CI: 1.58-12.96) were significantly associated with refractive error.

CONCLUSION

The burden of uncorrected refractive errors is high among primary schools children. Myopia was common in both sexes. The potential risk factors were sex, regular use of computers and higher grade level of students. Hence, school health programs should work on health information dissemination and eye health care services provision.

Egr-1 mRNA expression is a marker for the direction of mammalian ocular growth

PURPOSE

The immediate early gene Egr-1 is thought to form part of the pathway that mediates abnormal ocular growth. This study investigated whether the mRNA expression levels of Egr-1 in a mammalian retina are modulated differentially, depending on the direction of ocular growth.

METHODS

To induce accelerated growth and myopia, guinea pigs wore a -5 diopter (D) lens over one eye from 4 to 11 days of age. To induce inhibited growth, the lens was removed after 7 days of -5 D lens wear, and the eye allowed to recover from myopia for 3 days. Ocular parameters and Egr-1 mRNA levels were subsequently assessed, and compared to untreated fellow eyes and eyes from untreated littermates. Possible circadian changes in Egr-1 mRNA levels were also determined in 18 additional animals by taking measures every 4 hours during a 24-hour cycle.

RESULTS

Ocular compensation to a -5 D lens occurred after 7 days (Δ -4.8 D, Δ +147 μm growth, N = 20). In 5 highly myopic eyes (Δ -7.4 D), Egr-1 mRNA levels in the retina were significantly downregulated relative to contralateral control (51%) and age-matched untreated (47%) eyes. Three days after the -5 D lens was removed, eyes had recovered from the myopia (Δ -0.5 D, relative change of +2.9 D, N = 4) and Egr-1 mRNA levels were significantly elevated relative to contralateral (212%) and untreated (234%) eyes, respectively. Normal Egr-1 mRNA expression was higher in the middle of the day than in the middle of the night. Immunolabeling showed strong Egr-1 reactivity in cell bodies in the inner nuclear and ganglion cell layers.

CONCLUSIONS

Egr-1 mRNA levels in a mammalian retina show a bi-directional persistent response to opposing ocular growth stimuli. This suggests retinal Egr-1 might act as a signal for the direction of ocular growth in different species.

Longitudinal study of iris concavity, corneal biomechanics, and correlations to ocular biometry in a cohort of 10- to 12-year-old UK schoolboys: 2-year follow-up data

PURPOSE

To explore changes in iris curvature over a 2-year period. To investigate associations between iris curvature and ocular biometric parameters. To explore relationships between a number of nonocular measurements and ocular biometric parameters.

METHODS

Schoolboys enrolled 2 years previously were invited to return for anterior segment optical coherence tomography, corneal hysteresis (CH), corneal resistance factor (CRF), and axial biometric measurements. Refractive error was assessed and measures of height, weight, waist circumference, digit ratio, and percentage body fat taken.

RESULTS

Mean spherical equivalent refraction reduced by 0.76 diopters and mean iris concavity, defined as a measurement of less than or equal to -0.1 mm, increased by 0.018 mm at distance fixation and 0.04 mm on accommodation. Compared with 2 years previously, the prevalence of iris concavity increased from 24% to 32% on distance fixation and from 65% to 84% on accommodation. Variables significantly associated with nonaccommodating iris curvature were anterior chamber depth (ACD, P = 0.029) and mean scleral spur angle (P = 0.0001). Variables significantly associated with accommodating iris curvature were ACD (P = 0.02), lens vault (P = 0.047), and scleral spur angle (P < 0.0001). Significant association was again found between CH and accommodating spur-to-spur distance (R(2) = 0.13, P = 0.007).

CONCLUSIONS

Iris concavity was more prevalent in this cohort of schoolboys than 2 years earlier. The degree of concavity remains related to ACD and lens vault. The association between spur-to-spur distance and CH was similar at baseline and after 2 years.

Gene expression signatures in tree shrew choroid during lens-induced myopia and recovery

Gene expression in tree shrew choroid was examined during the development of minus-lens induced myopia (LIM, a GO condition), after completion of minus-lens compensation (a STAY condition), and early in recovery (REC) from induced myopia (a STOP condition). Five groups of tree shrews (n = 7 per group) were used. Starting 24 days after normal eye-opening (days of visual experience [DVE]), one minus-lens group wore a monocular -5 D lens for 2 days (LIM-2), another minus-lens group achieved stable lens compensation while wearing a monocular -5 D lens for 11 days (LIM-11); a recovery group also wore a -5 D lens for 11 days and then received 2 days of recovery starting at 35 DVE (REC-2). Two age-matched normal groups were examined at 26 DVE and 37 DVE. Quantitative PCR was used to measure the relative differences in mRNA levels in the choroid for 77 candidate genes that were selected based on previous studies or because a whole-transcriptome analysis suggested their expression would change during myopia development or recovery. Small myopic changes were observed in the treated eyes of the LIM-2 group (-1.0 ± 0.2 D; mean ± SEM) indicating eyes were early in the process of developing LIM. The LIM-11 group exhibited complete refractive compensation (-5.1 ± 0.2 D) that was stable for five days. The REC-2 group recovered by 1.3 ± 0.3 D from full refractive compensation. Sixty genes showed significant mRNA expression differences during normal development, LIM, or REC conditions. In LIM-2 choroid (GO), 18 genes were significantly down-regulated in the treated eyes relative to the fellow control eyes and 10 genes were significantly up-regulated. In LIM-11 choroid (STAY), 10 genes were significantly down-regulated and 12 genes were significantly up-regulated. Expression patterns in GO and STAY were similar, but not identical. All genes that showed differential expression in GO and STAY were regulated in the same direction in both conditions. In REC-2 choroid (STOP), 4 genes were significantly down-regulated and 18 genes were significantly up-regulated. Thirteen genes showed bi-directional regulation in GO vs. STOP. The pattern of differential gene expression in STOP was very different from that in GO or in STAY. Significant regulation was observed in genes involved in signaling as well as extracellular matrix turnover. These data support an active role for the choroid in the signaling cascade from retina to sclera. Distinctly different treated eye vs. control eye mRNA signatures are present in the choroid in the GO, STAY, and STOP conditions. The STAY signature, present after full compensation has occurred and the GO visual stimulus is no longer present, may participate in maintaining an elongated globe. The 13 genes with bi-directional expression differences in GO and STOP responded in a sign of defocus-dependent manner. Taken together, these data further suggest that a network of choroidal gene expression changes generate the signal that alters scleral fibroblast gene expression and axial elongation rate.

Genome-wide association studies of refractive error and myopia, lessons learned, and implications for the future

The investigation of the genetic basis of refractive error and myopia entered a new stage with the introduction of genome-wide association studies (GWAS). Multiple GWAS on many ethnic groups have been published over the years, providing new insight into the genetic architecture and pathophysiology of refractive error. This is a review of the GWAS published to date, the main lessons learned, and future possible directions of genetic studies of myopia and refractive error.

Developments in Ocular Genetics: 2013 Annual Review

PURPOSE

To highlight major advancements in ocular genetics from the year 2013.

DESIGN

Literature review.

METHODS

A literature search was conducted on PubMed to identify articles pertaining to genetic influences on human eye diseases. This review focuses on manuscripts published in print or online in the English language between January 1, 2013 and December 31, 2013. A total of 120 papers from 2013 were included in this review.

RESULTS

Significant progress has been made in our understanding of the genetic basis of a broad group of ocular disorders, including glaucoma, age-related macular degeneration, cataract, diabetic retinopathy, keratoconus, Fuchs' endothelial dystrophy, and refractive error.

CONCLUSIONS

The latest next-generation sequencing technologies have become extremely effective tools for identifying gene mutations associated with ocular disease. These technological advancements have also paved the way for utilization of genetic information in clinical practice, including disease diagnosis, prediction of treatment response and molecular interventions guided by gene-based knowledge.

Risk factors for astigmatism in the Vision in Preschoolers Study

PURPOSE

To determine demographic and refractive risk factors for astigmatism in the Vision in Preschoolers Study.

METHODS

Three- to 5-year-old Head Start preschoolers (N = 4040) from five clinical centers underwent comprehensive eye examinations by study-certified optometrists and ophthalmologists, including monocular visual acuity testing, cover testing, and cycloplegic retinoscopy. Astigmatism was defined as the presence of greater than or equal to +1.5 diopters (D) cylinder in either eye, measured with cycloplegic refraction. The associations of risk factors with astigmatism were evaluated using the odds ratio (OR) and its 95% confidence interval (CI) from logistic regression models.

RESULTS

Among 4040 Vision in Preschoolers Study participants overrepresenting children with vision disorders, 687 (17%) had astigmatism, and most (83.8%) had with-the-rule astigmatism. In multivariate analyses, African American (OR, 1.65; 95% CI, 1.22 to 2.24), Hispanic (OR, 2.25; 95% CI, 1.62 to 3.12), and Asian (OR, 1.76; 95% CI, 1.06 to 2.93) children were more likely to have astigmatism than non-Hispanic white children, whereas American Indian children were less likely to have astigmatism than Hispanic, African American, and Asian children (p < 0.0001). Refractive error was associated with astigmatism in a nonlinear manner, with an OR of 4.50 (95% CI, 3.00 to 6.76) for myopia (≤-1.0 D in spherical equivalent) and 1.55 (95% CI, 1.29 to 1.86) for hyperopia (≥+2.0 D) when compared with children without refractive error (>-1.0 D, <+2.0 D). There was a trend of an increasing percentage of astigmatism among older children (linear trend p = 0.06). The analysis for risk factors of with-the-rule astigmatism provided similar results.

CONCLUSIONS

Among Head Start preschoolers, Hispanic, African American, and Asian race as well as myopic and hyperopic refractive error were associated with an increased risk of astigmatism, consistent with findings from the population-based Multi-ethnic Pediatric Eye Disease Study and the Baltimore Pediatric Eye Disease Study. American Indian children had lower risk of astigmatism.

Influence of spherical aberration, stimulus spatial frequency, and pupil apodisation on subjective refractions

PURPOSE

To test competing hypotheses (Stiles Crawford pupil apodising or superior imaging of high spatial frequencies by the central pupil) for the pupil size independence of subjective refractions in the presence of primary spherical aberration.

METHODS

Subjective refractions were obtained with a variety of test stimuli (high contrast letters, urban cityscape, high and low spatial frequency gratings) while modulating pupil diameter, levels of primary spherical aberration and pupil apodisation. Subjective refractions were also obtained with low-pass and high-pass stimuli and using 'darker' and 'sharper' subjective criteria.

RESULTS

Subjective refractions for stimuli containing high spatial frequencies focus a near paraxial region of the pupil and are affected only slightly by level of Seidel spherical aberration, degree of pupil apodisation and pupil diameter, and generally focused a radius of about 1-1.5 mm from the pupil centre. Low spatial frequency refractions focus a marginal region of the pupil, and are significantly affected by level of spherical aberration, amount of pupil apodisation, and pupil size. Clinical refractions that employ the 'darker' or 'sharper' subjective criteria bias the patient to use lower or higher spatial frequencies, respectively.

CONCLUSIONS

In the presence of significant levels of spherical aberration, the pupil size independence of subjective refractions occurs with or without Stiles Crawford apodisation for refractions that optimise high spatial frequency content in the image. If low spatial frequencies are optimised by a subjective refraction, spherical refractive error varies with spherical aberration, pupil size, and level of apodisation. As light levels drop from photopic to scotopic, therefore, we expect a shift from pupil size independent to pupil size dependent subjective refractions. Emphasising a 'sharper' criterion during subjective refractions will improve image quality for high spatial frequencies and generate pupil size independent refractions.

Iris concavity, corneal biomechanics, and their correlations with ocular biometry in a cohort of 10- to 12-year-old UK school boys: baseline data

PURPOSE

Pigment dispersion syndrome is associated with iris concavity. This study investigated the prevalence of iris concavity, defined as a measurement of ≤-0.1 mm, in a cohort of 10- to 12-year-old boys, and explored the relationship between iris curvature and anterior segment biometry. Associations with corneal biomechanical parameters also were explored.

METHODS

A cohort of school boys (n = 96) was recruited from a local school. Anterior segment optical coherence tomography (AS-OCT) was performed under accommodative and nonaccommodative conditions, and iris curvature quantified. Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured with the ocular response analyzer (ORA). Noncontact axial biometry was performed using laser interferometry.

RESULTS

The prevalence of iris concavity was 24% on distance fixation, increasing to 65% on accommodation. Variables significantly associated with nonaccommodating iris curvature were lens vault (P = 0.02) and mean keratometry (P = 0.02). For both variables acting jointly, R(2) = 0.30. Variables associated significantly with accommodating iris curvature were anterior chamber depth (P = 0.009), lens vault (P = 0.049), and mean scleral spur angle (P < 0.0001). For these three variables acting jointly, R(2) = 0.33. Significant association was found between CH and spur-to-spur distance (R(2) = 0.07, P = 0.025).

CONCLUSIONS

Iris concavity was a common finding in this cohort and related to anterior segment biometric parameters. Further work is required to clarify whether anatomical differences exist between iris concavity seen in the adolescent eye and that found in adults with pigment dispersion syndrome.

A retrospective analysis of children with anisometropic amblyopia in Nepal

PURPOSE

Anisometropia is one of the main causes of amblyopia. This study was conducted to investigate the association between the depth of amblyopia and the magnitude of anisometropia.

METHODS

A retrospective record review was conducted at the Nepal Eye Hospital between July 2006 and June 2011. Those children included in this study were aged ≤13 years and diagnosed with unilateral anisometropic amblyopia, no strabismus and ocular pathology. Associations between the depth of amblyopia and the age and/or gender of the subjects, the laterality of the amblyopic eyes, the type and magnitude of refractive error of amblyopic eyes, and the magnitude of anisometropia were statistically analyzed.

RESULTS

Out of the 189 children with unilateral anisometropic amblyopia (mean age 9.1 ± 2.8 years), 59% were boys. Amblyopia was more commonly found in left eye (p < 0.001). The most common type of refractive error was astigmatism (61%). The depth of amblyopia was not associated with the gender (p = 0.864) or age (p = 0.341) of the subjects or the laterality of the eyes (p = 0.159), but it was associated with the type (p = 0.049) and magnitude (p = 0.013) of refractive error of the amblyopic eye and the magnitude of anisometropia (p = 0.002).

CONCLUSION

Nepalese anisometropic amblyopic children were presented late to hospital. The depth of amblyopia was highly associated with the type and magnitude of refractive error of the amblyopic eye and the magnitude of anisometropia. So, basic vision screening programs may help to find out the anisometropic children and reefer them to the hospital for timely management of anisometropic amblyopia if present.

Accuracy of noncycloplegic retinoscopy, retinomax autorefractor, and SureSight vision screener for detecting significant refractive errors

PURPOSE

To evaluate, by receiver operating characteristic (ROC) analysis, the ability of noncycloplegic retinoscopy (NCR), Retinomax Autorefractor (Retinomax), and SureSight Vision Screener (SureSight) to detect significant refractive errors (RE) among preschoolers.

METHODS

Refraction results of eye care professionals using NCR, Retinomax, and SureSight (n = 2588) and of nurse and lay screeners using Retinomax and SureSight (n = 1452) were compared with masked cycloplegic retinoscopy results. Significant RE was defined as hyperopia greater than +3.25 diopters (D), myopia greater than 2.00 D, astigmatism greater than 1.50 D, and anisometropia greater than 1.00 D interocular difference in hyperopia, greater than 3.00 D interocular difference in myopia, or greater than 1.50 D interocular difference in astigmatism. The ability of each screening test to identify presence, type, and/or severity of significant RE was summarized by the area under the ROC curve (AUC) and calculated from weighted logistic regression models.

RESULTS

For detection of each type of significant RE, AUC of each test was high; AUC was better for detecting the most severe levels of RE than for all REs considered important to detect (AUC 0.97-1.00 vs. 0.92-0.93). The area under the curve of each screening test was high for myopia (AUC 0.97-0.99). Noncycloplegic retinoscopy and Retinomax performed better than SureSight for hyperopia (AUC 0.92-0.99 and 0.90-0.98 vs. 0.85-0.94, P ≤ 0.02), Retinomax performed better than NCR for astigmatism greater than 1.50 D (AUC 0.95 vs. 0.90, P = 0.01), and SureSight performed better than Retinomax for anisometropia (AUC 0.85-1.00 vs. 0.76-0.96, P ≤ 0.07). Performance was similar for nurse and lay screeners in detecting any significant RE (AUC 0.92-1.00 vs. 0.92-0.99).

CONCLUSIONS

Each test had a very high discriminatory power for detecting children with any significant RE.

Self-adjustable glasses in the developing world

Uncorrected refractive errors are the single largest cause of visual impairment globally. Refractive errors are an avoidable cause of visual impairment that are easily correctable. Provision of spectacles is a cost-effective measure. Unfortunately, this simple solution becomes a public health challenge in low- and middle-income countries because of the paucity of human resources for refraction and optical services, lack of access to refraction services in rural areas, and the cost of spectacles. Low-cost approaches to provide affordable glasses in developing countries are critical. A number of approaches has been tried to surmount the challenge, including ready-made spectacles, the use of focometers and self-adjustable glasses, among other modalities. Recently, self-adjustable spectacles have been validated in studies in both children and adults in developed and developing countries. A high degree of agreement between self-adjustable spectacles and cycloplegic subjective refraction has been reported. Self-refraction has also been found to be less prone to accommodative inaccuracy compared with non-cycloplegic autorefraction. The benefits of self-adjusted spectacles include: the potential for correction of both distance and near vision, applicability for all ages, the empowerment of lay workers, the increased participation of clients, augmented awareness of the mechanism of refraction, reduced costs of optical and refraction units in low-resource settings, and a relative reduction in costs for refraction services. Concerns requiring attention include a need for the improved cosmetic appearance of the currently available self-adjustable spectacles, an increased range of correction (currently −6 to +6 diopters), compliance with international standards, quality and affordability, and the likely impact on health systems. Self-adjustable spectacles show poor agreement with conventional refraction methods for high myopia and are unable to correct astigmatism. A limitation of the fluid-filled adjustable spectacles (AdSpecs, Adaptive Eyecare Ltd, Oxford, UK) is that once the spectacles are self-adjusted and the power fixed, they become unalterable, just like conventional spectacles. Therefore, they will need to be changed as refractive power changes over time. Current costs of adjustable spectacles are high in developing countries and therefore not affordable to a large segment of the population. Self-adjustable spectacles have potential for “upscaling” if some of the concerns raised are addressed satisfactorily.

Seasonal variations in the progression of myopia in children enrolled in the correction of myopia evaluation trial

PURPOSE

To investigate monthly and seasonal variations in the progression of myopia in children enrolled in the Correction of Myopia Evaluation Trial (COMET).

METHODS

An ethnically diverse cohort of 469 myopic 6- to <12 year-old children was randomized to single vision or progressive addition lenses and followed for 3 years with 98.5% retention. Progression of myopia was measured semiannually by noncycloplegic autorefraction (Nidek ARK 700A) and annually by cycloplegic autorefraction, with the former measurements used in these analyses. The semiannual progression rate was calculated as (change in spherical equivalent refraction between two consecutive semiannual visits/number of days between the two visits) times 182.5. Months were categorized as the midpoint between two visit dates. Seasons were classified as winter (October through March) or summer (April through September). The seasonal difference was tested using a linear mixed model adjusting for demographic variables (age, sex, ethnicity), baseline refraction, and treatment group.

RESULTS

Data from 358 children (mean [± SD] age = 9.84 ± 1.27 years; mean myopia = -2.54 ± 0.84 diopters [D]) met the criteria for these analyses. Myopia progression varied systematically by month; it was slower in April through September than in the other months. Mean progression in winter was -0.35 ± 0.34 D and in summer was -0.14 ± 0.32 D, a statistically significant difference (0.21 D, P < 0.0001). The same seasonal pattern was found by age, sex, ethnicity (except in the small sample of Asians), lens type, and clinical center.

CONCLUSIONS

The slower progression of myopia found in summer is likely related to children's spending more time outdoors and fewer hours in school. The data have clinical implications regarding the time of year and the frequency with which myopic children have eye examinations and the need for precise timing of visits in clinical trials testing new myopia treatments. (ClinicalTrials.gov number, NCT00000113.).

Prevalence of vision impairment and refractive error in school children in Ba Ria - Vung Tau province, Vietnam

Background

To assess the prevalence of vision impairment and refractive error in school children 12–15 years of age in Ba Ria – Vung Tau province, Vietnam.

Design

Prospective, cross-sectional study.

Participants

2238 secondary school children.

Methods

Subjects were selected based on stratified multistage cluster sampling of 13 secondary schools from urban, rural and semi-urban areas. The examination included visual acuity measurements, ocular motility evaluation, cycloplegic autorefraction, and examination of the external eye, anterior segment, media and fundus.

Main Outcome Measures

Visual acuity and principal cause of vision impairment.

Results

The prevalence of uncorrected and presenting visual acuity ≤6/12 in the better eye were 19.4% (95% confidence interval, 12.5–26.3) and 12.2% (95% confidence interval, 8.8–15.6), respectively. Refractive error was the cause of vision impairment in 92.7%, amblyopia in 2.2%, cataract in 0.7%, retinal disorders in 0.4%, other causes in 1.5% and unexplained causes in the remaining 2.6%. The prevalence of vision impairment due to myopia in either eye (–0.50 diopter or greater) was 20.4% (95% confidence interval, 12.8–28.0), hyperopia (≥2.00 D) was 0.4% (95% confidence interval, 0.0–0.7) and emmetropia with astigmatism (≥0.75 D) was 0.7% (95% confidence interval, 0.2–1.2). Vision impairment due to myopia was associated with higher school grade and increased time spent reading and working on a computer.

Conclusions

Uncorrected refractive error, particularly myopia, among secondary school children in Vietnam is a major public health problem. School-based eye health initiative such as refractive error screening is warranted to reduce vision impairment.

Longitudinal study of spherical refractive error in infantile nystagmus syndrome

PURPOSE

To explore the onset and progression of spherical refractive error in a population with infantile nystagmus syndrome.

METHODS

Retrospective refractive error data were obtained from 147 medical records of children with infantile nystagmus syndrome (albinism n = 98; idiopathic infantile nystagmus n = 49), attending a low vision clinic in Northern Ireland, over a 24 year period (1986-2010). Data were categorised by age to allow for comparisons with published studies. A prospective group of participants with Infantile nystagmus syndrome (INS) [n = 22 (albinism n = 18, idiopathic infantile nystagmus n = 4)] (aged 0-4) were also recruited. Cycloplegic streak retinoscopy was performed biannually, over a 3 year period. Spherical equivalent refractive error and most ametropic meridian were analysed.

RESULTS

The mean spherical equivalent refractive errors for albinism and idiopathic infantile nystagmus groups (across all age categories) were hypermetropic, with highest levels demonstrated by the participants with albinism aged 1 ≤ 4 years (Mann-Whitney U test, p = 0.013). Mean most ametropic meridian was highest in the albinism group aged 1 ≤ 12 years (Mann-Whitney U test, p < 0.05). Individual data demonstrated relatively static spherical equivalent refractive errors over time. Prospective participants were hypermetropic at all visits and those with albinism had, on average, higher refractive errors than those with idiopathic infantile nystagmus (IIN). No significant correlations were noted between visual acuity and spherical equivalent refractive errors or most ametropic meridian.

CONCLUSIONS

Hypermetropia is the most prevalent spherical refractive error in the INS population, irrespective of level of visual acuity. Individuals with infantile nystagmus syndrome fail to demonstrate typical patterns of emmetropisation, particularly in the presence of albinism.

Heritability of lenticular myopia in English Springer spaniels

PURPOSE

We determined whether naturally-occurring lenticular myopia in English Springer spaniels (ESS) has a genetic component.

METHODS

Streak retinoscopy was performed on 226 related ESS 30 minutes after the onset of pharmacologic mydriasis and cycloplegia. A pedigree was constructed to determine relationships between affected offspring and parents. Estimation of heritability was done in a Bayesian analysis (facilitated by the MCMCglmm package of R) of refractive error in a model, including terms for sex and coat color. Myopia was defined as ≤-0.5 diopters (D) spherical equivalent.

RESULTS

The median refractive error for ESS was 0.25 D (range, -3.5 to +4.5 D). Median age was 0.2 years (range, 0.1-15 years). The prevalence of myopia in related ESS was 19% (42/226). The ESS had a strong correlation (r = 0.95) for refractive error between the two eyes. Moderate heritability was present for refractive error with a mean value of 0.29 (95% highest probability density, 0.07-0.50).

CONCLUSIONS

The distribution of refractive error, and subsequently lenticular myopia, has a moderate genetic component in ESS. Further investigation of genes responsible for regulation of the development of refractive ocular components in canines is warranted.

The Tromsø Eye Study: study design, methodology and results on visual acuity and refractive errors

PURPOSE

To describe the study design and methodology of the Tromsø Eye Study (TES), and to describe visual acuity and refractive error in the study population.

METHODS

The Tromsø Eye Study is a sub-study of the Tromsø Study, a population-based multipurpose longitudinal study in the municipality of Tromsø, Norway. The Tromsø Eye Study was a part of the sixth survey of the Tromsø Study, conducted from October 2007 through December 2008. The eye examination included information on self-reported eye diseases, assessment of visual acuity and refractive errors, retinal photography and optical coherence tomography. Retinal images were graded for diabetic retinopathy and age-related macular degeneration, and with computer-assisted measurements of arteriolar and venular diameters. In addition, TES researchers have access to the large comprehensive Tromsø Study database including physical examination results, carotid artery ultrasound, electrocardiogram, bone densitometry, cognitive tests, questionnaires, DNA, blood and urine samples and more from the present and the five previous surveys.

RESULTS

Visual acuity was assessed in 6459 subjects and refraction in 6566 subjects aged 38-87 years. Snellen visual acuity <20/60 was found in 1.2% (95% CI 0.95-1.5) of the participants and there was no gender difference. Visual impairment increased with age, and in the age group 80-87 years, the overall visual acuity <20/60 was 7.3% (95% CI 3.3-11.2). Spherical equivalent showed an increasing trend with age and there was no clinically relevant difference between men and women. Retinal photography was performed in 6540 subjects.

CONCLUSION

Prevalence of visual impairment was low but increased with age. There was a trend towards hyperopia with age and no clinically relevant difference in refraction between the sexes. TES aims to provide epidemiological research on several eye and eye-related diseases. Owing to a comprehensive data collection, it has the opportunity to explore issues related to environmental factors, cognition and their interaction with diseases in this community.

Incidence of strabismus and amblyopia in preverbal children previously diagnosed with pseudoesotropia

BACKGROUND AND PURPOSE

We previously reported that 12% of children under age 3 diagnosed with pseudoesotropia without significant refractive error later developed strabismus or mild refractive amblyopia. Mohan and Sharma recently reported on fifty-one patients with pseudoesotropia and hyperopia and noted that esotropia developed in 53.9% of the children with >1.50 D of hypermetropia compared to 2.6% of those who had ≤1.50 D hypermetropia, implying a low risk of esotropia unless hyperopia was greater than 1.50 D on initial exam. We reviewed our data to see if we had similar findings in our patients.

METHOD

Medical records between January 1, 2001, and February 26, 2010, were reviewed retrospectively. Three hundred ninety-four patients diagnosed with pseudoesotropia with an otherwise normal examination were reviewed, and 253 with follow-up were analyzed.

RESULTS

Forty-six children were 36 months or older at initial presentation; none developed strabismus; 207 children were <36 months at initial presentation; twenty-two children (11%) were later found to have strabismus. Seventy-eight of these children had hyperopia > 1.50 D; eight children (10%) later developed strabismus. One hundred twenty-nine children had hyperopia ≤ 1.50 D, and fourteen (11%) developed strabismus. Our analysis showed an equal risk of strabismus developing in pseudoesotropia patients under age 3 with greater or less than 1.50 D of hyperopia.

CONCLUSION

There is a significant risk of esotropia developing in children under three diagnosed with pseudoesotropia. Hyperopia less than 1.50 D, does not obviate the need for careful follow-up.

Gene expression signatures in tree shrew sclera in response to three myopiagenic conditions

PURPOSE

We compared gene expression signatures in tree shrew sclera produced by three different visual conditions that all produce ocular elongation and myopia: minus-lens wear, form deprivation, and dark treatment.

METHODS

Six groups of tree shrews (n = 7 per group) were used. Starting 24 days after normal eye-opening (days of visual experience [DVE]), two minus-lens groups wore a monocular -5 diopter (D) lens for 2 days (ML-2) or 4 days (ML-4); two form-deprivation groups wore a monocular translucent diffuser for 2 days (FD-2) or 4 days (FD-4). A dark-treatment (DK) group was placed in continuous darkness for 11 days after experiencing a light/dark environment until 17 DVE. A normal colony-reared group was examined at 28 DVE. Quantitative PCR was used to measure the relative differences in mRNA levels for 55 candidate genes in the sclera that were selected, either because they showed differential expression changes in previous ML studies or because a whole-transcriptome analysis suggested they would change during myopia development.

RESULTS

The treated eyes in all groups responded with a significant myopic shift, indicating that the myopia was actively progressing. In the ML-2 group, 27 genes were significantly downregulated in the treated eyes, relative to control eyes. In the treated eyes of the FD-2 group, 16 of the same genes also were significantly downregulated and one was upregulated. The two gene expression patterns were significantly correlated (r(2) = 0.90, P < 0.001). After 4 days of treatment, 31 genes were significantly downregulated in the treated eyes of the ML-4 group and three were upregulated. Twenty-nine of the same genes (26 down- and 3 up-regulated) and six additional genes (all downregulated) were significantly affected in the FD-4 group. The response patterns were highly correlated (r(2) = 0.95, P < 0.001). When the DK group (mean of right and left eyes) was compared to the control eyes of the ML-4 group, the direction and magnitude of the gene expression patterns were similar to those of the ML-4 (r(2) = 0.82, P < 0.001, excluding PENK). Similar patterns also were found when the treated eyes of the ML-4, FD-4, and DK groups were compared to the age-matched normal eyes.

CONCLUSIONS

The very similar gene expression signatures produced in the sclera by the three different myopiagenic visual conditions at different time points suggests that there is a "scleral remodeling signature" in this mammal, closely related to primates. The scleral genes examined did not distinguish between the specific visual stimuli that initiate the signaling cascade that results in axial elongation and myopia.

Small-aperture corneal inlay in patients with prior radial keratotomy surgeries

This paper describes the 3-month results of two patients who underwent KAMRA™ (AcuFocus, Inc, Irvine, CA, USA) inlay implantation surgery with a history of prior radial keratotomy. The refractive error just before KAMRA inlay implantation was corrected in one patient with a laser-assisted in situ keratomileusis (LASIK) procedure. The post-inlay implantation surgery results showed effective uncorrected near visual acuity outcomes with no impact on uncorrected distance visual acuity in both patients.

Myopia and the long-term incidence of cataract and cataract surgery: the Blue Mountains Eye Study

BACKGROUND

To assess the association between refractive errors and the 10-year incidence of cataract and cataract surgery.

DESIGN

Population-based prospective study.

PARTICIPANTS

Three thousand six hundred fifty-four persons aged 49+ years living in a well-defined geographical region were examined at baseline; 2564 were re-examined after 5 and/or 10 years.

METHODS

Baseline refractive error was measured using autorefraction with subjective refinement. Lens photographs were taken at each visit and assessed using the Wisconsin Cataract Grading System.

MAIN OUTCOME MEASURES

Long-term incidence of cataract and cataract surgery.

RESULTS

Compared with emmetropia, high myopia was associated with increased incidence of nuclear cataract (adjusted odds ratio 3.01, 95% confidence intervals 1.35-6.71). Low (odds ratio 1.86, confidence interval 1.03-3.35) and high myopia (odds ratio 7.80, confidence interval 3.51-17.35) were significantly associated with higher incidence of posterior subcapsular cataract. Low, moderate and high myopia were associated with increased incidence of cataract surgery (odds ratio 2.54, confidence interval 1.76-3.68; odds ratio 2.61, confidence interval 1.45-4.69; and odds ratio 4.81, confidence interval 2.33-9.93, respectively). Either any (odds ratio 1.35, confidence interval 1.08-1.69) or moderate hyperopia (odds ratio 1.76, confidence interval 1.32-2.34) was associated with increased incidence of nuclear cataract.

CONCLUSION

Our longitudinal study confirms the association between myopia and an increased risk of nuclear and posterior subcapsular cataract. It also suggests that hyperopia may increase the risk of nuclear cataract.

Costs of eye care services: prospective study from a faith-based hospital in Zambia

PURPOSE

To estimate the mean costs of cataract surgery and refractive error correction at a faith-based eye hospital in Zambia.

METHODS

Out-of-pocket expenses for user fees, drugs and transport were collected from 90 patient interviews; 47 received cataract surgery and 43 refractive error correction. Overhead and diagnosis-specific costs were determined from micro-costing of the hospital. Costs per patient were calculated as the sum of out-of-pocket expenses and hospital costs, excluding user fees to avoid double counting.

RESULTS

From the perspective of the hospital, overhead costs amounted to US$31 per consultation and diagnosis-specific costs were US$57 for cataract surgery and US$36 for refractive error correction. When including out-of-pocket expenses, mean total costs amounted to US$128 (95% confidence interval [CI] US$96--168) per cataract surgery and US$86 (95% CI US$67--118) per refractive error correction. Costs of providing services corresponded well with the user fee levels established by the hospital.

CONCLUSION

This is the first paper to report on the costs of eye care services in an African setting. The methods used could be replicated in other countries and for other types of visual impairments. These estimates are crucial for determining resources needed to meet global goals for elimination of avoidable blindness.

Population-based survey of refractive error among school-aged children in rural northern China: the Heilongjiang eye study

BACKGROUND

The prevalence of refractive error in the north of China is unknown. The study aimed to estimate the prevalence and associated factors of refractive error in school-aged children in a rural area of northern China.

DESIGN

Cross-sectional study.

PARTICIPANTS OR SAMPLES

The cluster random sampling method was used to select the sample.

METHODS

A total of 1700 subjects of 5 to 18 years of age were examined. All participants underwent ophthalmic evaluation. Refraction was performed under cycloplegia. Association of refractive errors with age, sex, and education was analysed.

MAIN OUTCOME MEASURES

The main outcome measure was prevalence rates of refractive error among school-aged children.

RESULTS

Of the 1700 responders, 1675 were eligible. The prevalence of uncorrected, presenting, and best-corrected visual acuity of 20/40 or worse in the better eye was 6.3%, 3.0% and 1.2%, respectively. The prevalence of myopia was 5.0% (84/1675, 95% CI, 4.8%-5.4%) and of hyperopia was 1.6% (27/1675, 95% CI, 1.0%-2.2%). Astigmatism was evident in 2.0% of the subjects. Myopia increased with increasing age, whereas hyperopia and astigmatism were associated with younger age. Myopia, hyperopia and astigmatism were more common in females. We also found that prevalence of refractive error were associated with education. Myopia and astigmatism were more common in those with higher degrees of education.

CONCLUSION

This report has provided details of the refractive status in a rural school-aged population. Although the prevalence of refractive errors is lower in the population, the unmet need for spectacle correction remains a significant challenge for refractive eye-care services.

Clinical comparison of the Welch Allyn SureSight™ handheld autorefractor vs. streak retinoscopy in dogs

OBJECTIVE

To compare the Welch Allyn SureSight™ wavefront autorefractor with retinoscopy in normal dogs.

ANIMALS STUDIED

Fifty privately owned dogs (100 eyes) of 20 breeds, free of ocular disease. Mean ± SD age: 5.7 ± 3.25 years (range: 6 months-13 years).

PROCEDURES

The refractive error was determined in each eye by two experienced retinoscopists using streak retinoscopy as well as by an autorefractor operated by two different examiners. Measurements were performed before and approximately 30-45 min after cycloplegia was induced by cyclopentolate 0.5% and tropicamide 0.5% ophthalmic solutions.

RESULTS

Mean ± SD noncyclopleged retinoscopy net sphere was -0.55 ± 1.14 (range: -3.75 to 3.5) diopters (D). Mean cyclopleged retinoscopy net sphere was -0.52 ± 1.18 (range: -4.25 to 2) D. Mean ± SD noncyclopleged autorefractor spherical equivalent (SE) was -0.42 ± 1.13 D (range: -3.36 to 2.73) D. Mean cyclopleged autorefractor SE was 0.10 ± 1.47 (range: -5.62 to 3.19) D. Noncyclopleged autorefraction results were not significantly different from streak retinoscopy (whether noncyclopleged or cyclopleged, P = 0.80 and P = 0.26, respectively). Cyclopleged autorefraction results were significantly different from noncyclopleged or cyclopleged streak retinoscopy (P < 0.0001 in both states). There was no significant difference between noncyclopleged and cyclopleged streak retinoscopy (P = 0.97).

CONCLUSIONS

Noncyclopleged autorefraction shows good agreement with streak retinoscopy in dogs and may be a useful clinical technique. Cycloplegia does not significantly affect streak retinoscopy results in dogs.

Refractive change after vitrectomy for epiretinal membrane in pseudophakic eyes

PURPOSE

To report the change in refraction in pseudophakic eyes following 23-gauge vitrectomy for epiretinal membrane (ERM), without use of silicone oil, intraocular gas or scleral buckling.

METHODS

Retrospective review of the records of 28 pseudophakic eyes in 28 patients undergoing 23-gauge pars plana vitrectomy for ERM. All 28 eyes had a measured preoperative refraction in their records and were seen minimum 2 months after vitrectomy for measuring their refraction. Fellow eyes (28 eyes) were used as controls.

RESULTS

The mean preoperative refraction was -0.15 ± 0.85 dioptre (D), and the mean postoperative refraction was -0.41 ± 0.93 D. Thus, a myopic shift was observed following vitrectomy with a mean change in refraction of -0.26 ± 0.60 D (range +0.75 to -2.13 D, p = 0.032). The postoperative change in refraction was within ±0.25, ±0.50 and ±1.00 D in 39%, 68% and 96% of the eyes, respectively. The mean absolute refractive error was 0.47 ± 0.44 D. The change in refraction in fellow eyes was +0.01 D (p = 0.82).

CONCLUSION

The change in refraction following 23-gauge pars plana vitrectomy for ERM in pseudophakic eyes was -0.26 D.

Is myopia a public health problem in India?

Myopia, a form of refractive error is a leading cause of visual disability throughout the world. In India uncorrected refractive errors are the most common cause of visual impairment and second major cause of avoidable blindness. Due to this the public health and economic impact of myopia is enormous. Although school vision screening programme is very successful in many states, still a significant number of school going children remain unidentified and the unmet need for correcting refractive errors in children appears to be significant.

A prospective study of spherical refractive error and ocular components among Northern Irish schoolchildren (the NICER study)

PURPOSE

To explore 3-year change in spherical refractive error and ocular components among white Northern Irish schoolchildren.

METHODS

Baseline data were collected among 6- to 7-year-old and 12- to 13-year-old children. Three years after baseline, follow-up data were collected. Cycloplegic refractive error and ocular components measurements (axial length [AL], anterior chamber depth [ACD], corneal radius of curvature [CRC]) were determined using binocular open-field autorefraction and ocular biometry. Change in spherical equivalent refractive error (SER) and ocular components were calculated.

RESULTS

A statistically significantly greater change in SER was found between 6 to 7 years and 9 to 10 years (younger cohort) compared to between 12 to 13 years and 15 to 16 years (older cohort) (-0.38 diopter [D] and -0.13 D, respectively) (P<0.001). A statistically significantly greater change in AL was found among the younger compared to the older cohort (0.48 mm and 0.14 mm, respectively) (P<0.001). Change in ACD was minimal across both groups (0.12 mm younger and 0.05 mm older cohort) as were changes in CRC. Change in SER was associated with change in AL in both age groups (both P<0.01).

CONCLUSIONS

There is a greater change in both spherical refractive error and axial length in younger children when compared with teenagers. Although increase in axial length drives refractive change during childhood and teenage years, lens compensation continues to occur in an attempt to maintain emmetropia. White children living in Northern Europe demonstrate dramatically less change in spherical refractive error over a fixed period of time than their East Asian counterparts. In contrast, they appear to exhibit more rapid myopic progression than UK children studied in the mid-20th century.

Region-specific relationships between refractive error and ciliary muscle thickness in children

PURPOSE

To determine if there is a relationship between refractive error and ciliary muscle thickness in different muscle regions.

METHODS

An anterior segment optical coherence tomographer was used to measure cycloplegic ciliary muscle thicknesses at 1 mm (CMT1), 2 mm (CMT2), and 3 mm (CMT3) posterior to the scleral spur; maximum (CMTMAX) thickness was also assessed. An autorefractor was used to determine cycloplegic spherical equivalent refractive error (SPHEQ). Apical ciliary muscle fibers were obtained by subtracting corresponding CMT2 values from CMT1 and CMTMAX. Multilevel regression models were used to determine the relationship between ciliary muscle thickness in various regions of the muscle and refractive error.

RESULTS

Subjects included 269 children with a mean age of 8.71 ± 1.51 years and a mean refractive error of +0.41 ± 1.29 diopters. In linear models with ciliary muscle thicknesses and SPHEQ, SPHEQ was significantly associated only with CMT2 (β = -11.34, P = 0.0008) and CMT 3 (β = -6.97, P = 0.007). When corresponding values of CMT2 were subtracted from CMT1 and CMTMAX, apical fibers at CMT1 (β = 14.75, P < 0.0001) and CMTMAX (β = 18.16, P < 0.0001) had a significant relationship with SPHEQ.

CONCLUSIONS

These data indicated that in children the posterior ciliary muscle fibers are thicker in myopia (CMT2 and CMT3), but paradoxically, the apical ciliary muscle fibers are thicker in hyperopia (CMTMAX and CMT1). This may be the first evidence that hyperopia is associated with a thicker apical ciliary muscle region.

Psychometric properties of the national eye institute refractive error correction quality-of-life questionnaire among Iranian patients

BACKGROUND AND AIM

To evaluate the psychometric properties of the national Eye Institute refractive error correction quality of life questionnaire (NEI-RQL-42) among Iranian patients with refractive errors.

MATERIALS AND METHODS

Two samples of patients (n1 = 296, n2 = 95) were consecutively selected from the eye clinic of the Boo-Ali Hospital, Qazvin. A forward-backward procedure was conducted to translate and cross-culturally adapt the Iranian version of the NEI-RQL-42. A homogeneity, stability, and reliability test was conducted for the first sample after a two-week interval. Convergent validity was computed using the correlation between the NEI-RQL-42 subscale scores, National Eye Institute-Visual Functioning Questionnaire (NEI-VFQ-25), and the Short Form-36 (SF-36). Furthermore, Known-group analysis was performed, to determine the discriminant validity between the subgroups of patients with hyperopia, emmetropia, and myopia. Responsiveness to clinical change was tested by administering NEI-RQL-42 on the second sample that was scheduled for surgery.

RESULTS

Homogeneity was satisfactory with the Cronbach's alpha coefficients ranging between 0.70 and 0.92. The 13 subscales of the NEI-RQL-42 showed a considerable stability in intra-class-correlation (ICC) ranging between 0.70 and 0.89. Positive correlation coefficients were found among all subscales of the NEI-RQL-42 and the other quality-of-life instruments (NEI-VFQ-25 and SF-36). The NEI-VFQ-25 displayed excellent discriminant validity to differentiate the subgroups of patients, and was found to be responsive to change after the surgical correction at three months.

CONCLUSIONS

The Iranian version of the NEI-RQL-42 is a valid and reliable instrument to assess refractive error correction quality-of-life in Iranian patients. Moreover this questionnaire can be used to evaluate the effectiveness of interventions in patients with refractive errors.

Genetic susceptibility and mechanisms for refractive error

Refractive errors, myopia and hyperopia, are the most common causes of visual impairment worldwide. Recent advances in genetics have been utilized to identify a wealth of genetic loci believed to contain susceptibility genes for refractive error (RE). The current genetic evidence confirms that RE is influenced by both common and rare variants with a significant environmental component. These studies argue that only by combining genetic and environmental knowledge with in vivo measurements of biological states will it be possible to understand the underlying biology of RE that will lead to novel therapeutic targets and accurate genetic predictions.

Choroidal thickness in childhood

PURPOSE

We examined choroidal thickness (ChT) and its spatial distribution across the posterior pole in pediatric subjects with normal ocular health and minimal refractive error.

METHODS

ChT was assessed using spectral domain optical coherence tomography (OCT) in 194 children aged 4 to 12 years, with spherical equivalent refractive errors between +1.25 and -0.50 diopters sphere (DS). A series of OCT scans were collected, imaging the choroid along 4 radial scan lines centered on the fovea (each separated by 45°). Frame averaging was used to reduce noise and enhance chorioscleral junction visibility. The transverse scale of each scan was corrected to account for magnification effects associated with axial length. Two independent masked observers segmented the OCT images manually to determine ChT at foveal center, and averaged across a series of perifoveal zones over the central 5 mm.

RESULTS

The average subfoveal ChT was 330 ± 65 μm (range, 189-538 μm), and was influenced significantly by age (P = 0.04). The ChT of the 4- to 6-year-old age group (312 ± 62 μm) was significantly thinner compared to the 7- to 9-year-olds (337 ± 65 μm, P < 0.05) and bordered on significance compared to the 10- to 12-year-olds (341 ± 61 μm, P = 0.08). ChT also exhibited significant variation across the posterior pole, being thicker in more central regions. The choroid was thinner nasally and inferiorly compared to temporally and superiorly. Multiple regression analysis revealed age, axial length, and anterior chamber depth were associated significantly with subfoveal ChT (P < 0.001).

CONCLUSIONS

ChT increases significantly from early childhood to adolescence. This appears to be a normal feature of childhood eye growth.

Ocular disorder in children with mental retardation

BACKGROUND

Ocular problems are common in mentally retarded children. Due to population growth these problems are increasing. Prevalence rate is variable from region to region. Data on ocular problems in mentally retarded school children is lacking in this region.

AIM

The aim of the present study was to identify the ocular disorders in children with mental retardation attending special schools in a district and to study their relationship with the degree of retardation.

MATERIALS AND METHODS

A total of 241 mentally retarded school children in the age group of 6-16 years attending special schools for the mentally retarded children in a district in central India were examined by a team of ophthalmologist, psychiatrist, and a resident in ophthalmology department of a medical college. Complete ocular examination was done. Ocular problems were identified and categorized according to the intelligent quotient.

RESULTS

One hundred and twenty four children (51.45%) had ocular problems. Strabismus (10.37%) and refractive error (20.75%) were the common ocular problems seen in this study. An association was found between the severity of mental retardation and ocular problems (P<0.005). However, no association was seen between the severity of mental retardation and strabismus and refractive error.

CONCLUSION

A high prevalence of ocular problems was seen in mentally retarded school children. Children with mental retardation should undergo annual ophthalmological check up. Early detection and correction of ocular problems will prevent visual impairment in future.

High prevalence of refractive errors in a rural population: 'Nooravaran Salamat' Mobile Eye Clinic experience

BACKGROUND

The prevalence of myopia and hyperopia and determinants were determined in a rural population of Iran.

DESIGN

Population-based cross-sectional study.

PARTICIPANTS

Using random cluster sampling, 13 of the 83 villages of Khaf County in the north east of Iran were selected. Data from 2001 people over the age of 15 years were analysed.

METHODS

Visual acuity measurement, non-cycloplegic refraction and eye examinations were done at the Mobile Eye Clinic.

MAIN OUTCOME MEASURES

The prevalence of myopia and hyperopia based on spherical equivalent worse than -0.5 dioptre and +0.5 dioptre, respectively.

RESULTS

The prevalence of myopia, hyperopia and anisometropia in the total study sample was 28% (95% confidence interval: 25.9-30.2), 19.2% (95% confidence interval: 17.3-21.1), and 11.5% (95% confidence interval: 10.0-13.1), respectively. In the over 40 population, the prevalence of myopia and hyperopia was 32.5% (95% confidence interval: 28.9-36.1) and 27.9% (95% confidence interval: 24.5-31.3), respectively. In the multiple regression model for this group, myopia strongly correlated with cataract (odds ratio = 1.98 and 95% confidence interval: 1.33-2.93), and hyperopia only correlated with age (P < 0.001). The prevalence of high myopia and high hyperopia was 1.5% and 4.6%. In the multiple regression model, anisometropia significantly correlated with age (odds ratio = 1.04) and cataract (odds ratio = 5.2) (P < 0.001).

CONCLUSION

The prevalence of myopia and anisometropia was higher than that in previous studies in urban population of Iran, especially in the elderly. Cataract was the only variable that correlated with myopia and anisometropia.

Peripheral optics with bifocal soft and corneal reshaping contact lenses

PURPOSE

To determine whether bifocal soft contact lenses with a distance center design provide myopic defocus to the peripheral retina similar to corneal reshaping contact lenses.

METHODS

Myopic subjects underwent five cycloplegic autorefraction readings centrally and at 10, 20, and 30 degrees temporally, nasally, superiorly, and inferiorly while wearing Proclear Multifocal "D" contact lenses with a +2.00-diopter add power (CooperVision, Fairport, NY) and after wearing Corneal Refractive Therapy (Paragon Vision Sciences, Mesa, AZ) contact lenses for 2 weeks.

RESULTS

Fourteen subjects completed the study. Nine (64%) were female, and 12 (86%) were white. The average (± SD) spherical equivalent noncycloplegic manifest refraction for the right eye was -2.84 ± 1.29 diopters. The average logMAR best-corrected, binocular, high-contrast visual acuity was -0.17 ± 0.15 while wearing the bifocal soft contact lenses and -0.09 ± 0.16 after corneal reshaping contact lens wear (analysis of variance, p = 0.27). The orthokeratology contact lens yielded a more myopic peripheral optical profile than the soft bifocal contact lens at 20 and 30 degrees eccentricity (except inferior at 20 degrees); the two modalities were similar at 10 degrees eccentricity.

CONCLUSIONS

Our data suggest that the two modalities are dissimilar despite the statistical similarities. The corneal reshaping contact lens shows an increase in relative peripheral myopic refraction, a pattern achieved by other studies, but the bifocal lens does not exhibit such a pattern. The low statistical power of the study could be a reason for lack of providing statistical difference in other positions of gaze, but the graphical representation of the data shows a marked difference in the peripheral optical profile between the two modalities. More sophisticated methods of measuring the peripheral optical profile may be necessary to accurately compare the two modalities and to determine the true optical effect of the bifocal soft contact lens on the peripheral retina.

LASIK as an alternative line to treat noncompliant esotropic children

PURPOSE

To assess the safety and efficacy of laser-assisted in situ keratomileusis (LASIK) in facilitating strabismus management in noncompliant children with fully accommodative esotropia.

SETTING

Ebsar Eye Center, Benha University (Benha, Egypt).

METHODS

The study comprised 20 eyes of ten consecutive patients with accommodative esotropia. All patients were noncompliant with glasses and had refractive stability. They received brief general anesthesia and had bilateral LASIK using Wavelight® Algretto Wave® Eye-Q Excimer Laser (Alcon, Inc, Hunenberg, Switzerland) to fully correct their hyperopic refractive errors aiming to achieve orthophoria. Preoperative and postoperative best corrected visual acuity, cycloplegic refraction, angle of squint, and any LASIK complications were recorded. Follow-up period was 9 months.

RESULTS

The age of patients ranged 5.1-9.2 years and the hyperopic error range was +3.5 D to +6.75 D, with anisometropia 2 D or less. No patient had decreased best corrected visual acuity or loss of fusion ability. The postoperative refractive error ranged from -0.75 D to +1.5 D at the end of the study period. All patients achieved orthophoria. No significant intraoperative or postoperative complications were recorded.

CONCLUSION

LASIK appears to be effective and relatively safe to treat accommodative esotropic children by reducing their hyperopic refractive error, however, patient selection is critical. Larger studies with longer follow-up are necessary to determine its long-term effects.

Epidemiology, genetics and treatments for myopia

Myopia is a significant public health problem and its prevalence is increasing over time and genetic factors in disease development are important. The prevalence and incidence of myopia within sampled population often varies with age, country, sex, race, ethnicity, occupation, environment, and other factors. Myopia growth is under a combination of genes and their products in time and space to complete the coordination role of the guidance. Myopia-related genes include about 70 genetic loci to which primary myopias have been mapped, although the number is constantly increasing and depends to some extent on definition. Of these, several are associated with additional abnormalities, mostly as part of developmental syndromes. These tend to result from mutations in genes encoding transcriptional activators, and most of these have been identified by sequencing candidate genes in patients with developmental anomalies. Currently, COL1A1 (collagen alpha-1 chain of type I), COL2A1 (collagen alpha-1 chain of type II), ACTC1 (actin, alpha, cardiac muscle 1), PAX6 (paired box gene 6) and NIPBL (nipped-B homolog), and so on have been mapped. Myopia is most commonly treated with spectacles or glasses. The most common surgical procedure performed to correct myopia is laser in situ keratomileusis (LASIK). This review of the recent advances on epidemiology, genetic locations and treatments of myopia are summarized.

Predicting the necessity of LASIK enhancement after cataract surgery in patients with multifocal IOL implantation

Purpose

To investigate if the parameters measured routinely prior to cataract surgery with multifocal intraocular lens (IOL) implantation can predict the necessity of additional laser in situ keratomileusis (LASIK) to improve visual outcome.

Methods

Records of patients undergoing cataract surgery between January 2008 and December 2009 were reviewed. Individuals satisfied with visual outcome of cataract surgery and not satisfied were grouped (group 1 and 2, respectively). Preoperative data of refractive error, axial length, corneal astigmatism, intraocular pressure, and postoperative uncorrected visual acuity were recorded. Data was available for 62 patients (104 eyes), of which LASIK enhancement was deemed necessary in 21 eyes (20%; group 2). The receiver operator characteristic curves were used to discriminate between the groups and linear regression analysis was performed to predict the postoperative visual outcome.

Results

The astigmatism measured preoperatively using manifest refraction had an accuracy of 64% in discriminating between the groups. Age, spherical component of refraction, axial length, corneal astigmatism, and intraocular pressure were very close to chance prediction 59%, 57%, 56%, 51%, and 51%, respectively. The postoperative uncorrected visual acuity had an accuracy of 79% in discriminating the groups. Individuals with uncorrected visual acuity worse than 20/40 after cataract surgery were most likely to undergo LASIK enhancement; however, approximately 20% of group 2 underwent LASIK enhancement despite having visual acuity of 20/30 or better. When combined, preoperative visual acuity accounted for just 7% of variance in postoperative uncorrected visual acuity.

Conclusion

Requirement of LASIK enhancement after cataract surgery with multifocal IOL implant is complex in nature, and parameters routinely measured before surgery cannot successfully identify the group requiring LASIK enhancement or predict postoperative uncorrected visual acuity.

Comparison of the Retinomax and Palm-AR Auto-Refractors: a pilot study

PURPOSE

To compare the performance of two handheld auto-refractors, the Retinomax and the Palm-Automatic Refractometer (Palm-AR), for detecting significant vision disorders in pre-school children.

METHODS

Children attending Philadelphia PreKindergarten Head Start were screened with the Retinomax and Palm-AR and underwent a gold standard eye examination. The results of cycloplegic retinoscopy, cover testing, and visual acuity were used to classify children as having normal vision or one of four conditions: amblyopia, strabismus, significant refractive error, and reduced visual acuity. Pass/fail criteria for each instrument were selected to maximize overall sensitivity (with specificity set at 90% and at 94%) for detecting targeted disorders. Comparisons of sensitivities between the auto-refractors were performed using the exact McNemar test.

RESULTS

Testability was >99% for both instruments. Test time was similar for the two instruments (median 2 min; p=0.10). At 90% specificity, the sensitivity for detection of one or more targeted conditions was 74% for the Palm-AR and 78% for the Retinomax. At 94% specificity, the sensitivity for detection of one or more targeted conditions was 66% for both the Palm-AR and the Retinomax. At 90% specificity, the sensitivity for detecting significant refractive error was 84% for both auto-refractors, and at 94% specificity, the sensitivity was 76% for the Palm AR and 75% for the Retinomax. There were high correlations between the instruments for sphere (r=0.85) and cylinder (r=0.88) power. The mean difference between instruments was -0.13 diopters (D) (95% limit of agreement: -2.28 to 2.02) for sphere, and -0.15 D (95% limit of agreement: -0.89 to 0.59) for cylinder.

CONCLUSIONS

In this pilot study, the Retinomax and Palm-AR appear comparable with respect to testability, sensitivity, and specificity. There was strong agreement in readings of sphere and cylinder indicating that they may perform similarly in a screening setting.