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Early visual deprivation is known to have profound consequences on the subsequent development of spatial visual processing. However, its impact on temporal processing is not well characterized. We have examined spatial and temporal contrast sensitivity functions following treatment for early and extended bilateral visual deprivation in fifteen children born with congenital cataracts in rural India. The results reveal a marked difference in post-treatment spatial and temporal sensitivities. Whereas spatial processing in newly sighted children is significantly impaired relative to age-matched controls, temporal processing exhibits remarkable resilience and is comparable to that in the control group. This difference in spatial and temporal outcomes is especially surprising given our computational analyses of video sequences which indicate a strong linkage between the spatial and temporal spectral content of natural visual inputs. We consider possible explanations for this discrepancy.

AIM: To investigate the effects of school-based comprehensive intervention on myopia development in elementary school children. METHODS: As a part of the Wenzhou Epidemiology of Refraction Error Study, there were 1524 participating elementary students (730 girls, 47.9%) in grades 1 to 3 from three campuses of one school, aged 7.3±0.9y, who were examined twice every year for a 2.5y follow up period. Comprehensive intervention and other reminders were given at school every semester for the intervention group. The control group did not receive comprehensive intervention and did not have reminders of it. RESULTS: There were 651 students in the intervention group [mean age 7.3±0.9y; 294 (45.2%) girls] and 737 students in the control group [mean age 7.2±0.9y; 346 (46.9%) girls]. Overall mean myopia progression during the 2.5y follow-up was -0.49±1.04 diopters (D) in the intervention group and -0.65±1.08 D in the control group (P=0.004). The majority that not get myopia at baseline spherical equivalent (SE≤-1.0 D). Their mean myopia progression during the 2.5y follow-up was -0.37±0.89 D in the intervention group and -0.51±0.93 D in the control group (27.5% reduction, P=0.009); Overall, mean axial length elongation was less in the intervention group (0.56±0.32 mm) than in the control group (0.61±0.38 mm, 10.5% reduction, P=0.009). The percentage of close reading distance (

Purpose The purposes of the study were to analyze patient use and satisfaction with low vision aids (LVAs) at the Wenzhou Medical University Low Vision and Rehabilitation Center and to assess the promotion of visual rehabilitation services as a new responsibility for nurses in China. Methods Records of 178 patients with low vision (LV) from the Low Vision and Rehabilitation Center examined between October 2015 and October 2016 included basic patient information (e.g., age, diagnosis, visual acuity, educational level) and use of LVAs (patients' own aids, daily duration of LVA use, or refusal to use aids). Results Sixty percent owned LVAs. Of these, 66% were obtained from a hospital, 26% were obtained from commercial stores, and others were obtained from government or gifts. Patients reported that use of LVAs was reduced because of visual fatigue (39%), inconvenience (22%), and lack of benefit (12%). Reasons for the 40% who had never used visual rehabilitation were nonreferral by doctors (76%), refusal because of inconvenience, discomfort and cosmetics (20%), or a preference for other treatments (4%). Conclusions Greater awareness of LV rehabilitation by nurses, ophthalmologists, patients, and the public is necessary. Additional government support for LV rehabilitation is also required.

The formation of focused and corresponding foveal images requires a close synergy between the accommodation and vergence systems. This linkage is usually decoupled in virtual reality systems and may be dysfunctional in people who are at risk of developing myopia. We study how refractive error affects vergence-accommodation interactions in stereoscopic displays. Vergence and accommodative responses were measured in 21 young healthy adults (n=9 myopes, 22 to 31 years) while subjects viewed naturalistic stimuli on a 3D display. In Step 1, vergence was driven behind the monitor using a blurred, non-accommodative, uncrossed disparity target. In Step 2, vergence and accommodation were driven back to the monitor plane using naturalistic images that contained structured depth and focus information from size, blur and/or disparity. In Step 1, both refractive groups converged towards the stereoscopic target depth plane, but the vergence-driven accommodative change was smaller in emmetropes than in myopes (F1,19=5.13, p=0.036). In Step 2, there was little effect of peripheral depth cues on accommodation or vergence in either refractive group. However, vergence responses were significantly slower (F1,19=4.55, p=0.046) and accommodation variability was higher (F1,19=12.9, p=0.0019) in myopes. Vergence and accommodation responses are disrupted in virtual reality displays in both refractive groups. Accommodation responses are less stable in myopes, perhaps due to a lower sensitivity to dioptric blur. Such inaccuracies of accommodation may cause long-term blur on the retina, which has been associated with a failure of emmetropization.

Purpose To quantify retinal vascular density in amblyopic children and to investigate the relationship between superficial and deep retinal vessel density and retinal thickness. Method In this prospective cross-sectional study, 85 amblyopic children (5-12 years) and 66 age-matched control subjects participated at a pediatric ophthalmology clinic. Macular vessel densities of the superficial and deep capillary plexuses (SCP, DCP, respectively) and retinal thickness were measured by clinical optical coherence tomographic angiography (OCTA). Vessel density and retinal thickness were compared between amblyopic groups and the control group, and correlations among these two variables were analyzed. Results Of the 85 amblyopic children, 52 children had anisometropic amblyopia, 16 had strabismic amblyopia, and 17 had bilateral amblyopia. The foveal and parafoveal macular vessel density in the SCP was lower in amblyopic than control children (P ≤ 0.008). Compared to strabismic and bilateral amblyopias, anisometropic amblyopia SCP differed the most from controls (P ≤ 0.005). Macular vessel density in the DCP of amblyopic children was similar to controls. Multiple linear regression analyses showed SCP vessel density was positively correlated with inner retinal thickness in the fovea (P < 0.001) and in the temporal, nasal, and inferior quadrants of the parafovea (P ≤ 0.008). Conclusions Macular vessel density is decreased in anisometropic amblyopia, and to a lesser extent, the other amblyopias. Retinal small vessel density was correlated with the thickness of the macular inner retina. The causality of retinal change (i.e., whether it is primary or secondary to the onset of amblyopia) has not yet been determined.

Disruption of normal visual experience or changes in the normal interaction between central and peripheral retinal input may lead to the development of myopia. In order to examine the relationship between peripheral contrast sensitivity and myopia, we manipulated attentional load for foveal vision in emmetropes and myopes while observers detected targets with peripheral vision. Peripheral contrast detection thresholds were measured binocularly using vertical Gabor stimuli presented at three eccentricities (±8°, 17°, 30°) in a spatial 2 alternative forced choice task. Contrast thresholds were measured in young adult (mean age 24.5 ± 2.6 years) emmetropes (n = 17; group SE: +0.19 ± 0.32D) and myopes (n = 25; group SE: −3.74 ± 1.99D). Attention at central fixation was manipulated with: (1) a low attention task, requiring simple fixation; or (2) a high attention task, which required subjects to perform a mathematical task. We found that at 30° all subjects exhibited lower contrast sensitivity (higher thresholds). In addition, myopes (Wilcoxon, p < 0.01), but not emmetropes (Wilcoxon, p = 0.1), had a significant decrease in sensitivity at 30° during the high attention task. However, the attention dependent threshold increase for myopes was not significantly greater than for emmetropes (Wilcoxon, p = 0.27). Attentional load did not increase thresholds at 8° or 17° for either refractive group. These data indicate that myopes experience a greater decrease in contrast sensitivity in the far periphery than emmetropes when attention is deployed in central vision.

How we learn to interact with and understand our environment for the first time is an age-old philosophical question. Scientists have long sought to understand what is the origin of egocentric spatial localization and the perceptual integration of touch and visual information. It is difficult to study the beginnings of intermodal visual-motor and visual-tactile linkages in early infancy since infants' muscular strength and control cannot accurately guide visual-motor behavior and they do not concentrate well [1-6]. Alternatively, one can examine young children who have a restored congenital sensory modality loss. They are the best infant substitute if they are old enough for good muscle control and young enough to be within the classic critical period for neuroplasticity [7, 8]. Recovery studies after removal of dense congenital cataracts are examples of this, but most are performed on older subjects [9-14]. We report here the results of video-recorded experiments on a congenitally blind child, beginning immediately after surgical restoration of vision. Her remarkably rapid development of accurate reaching and grasping showed that egocentric spatial localization requires neural circuitry needing less than a half hour of spatially informative experience to be calibrated. 32 hr after first sight, she visually recognized an object that she had simultaneously looked at and held, even though she could not use single senses alone (vision to vision; touch to touch) to perform this recognition until the following day. Then she also performed intersensory transfer of tactile object experience to visual object recognition, demonstrating that the two senses are prearranged to immediately become calibrated to one another.

The aim of this study was to investigate the prevalence of myopia in key (university-oriented) and non-key elementary schools in China using a traditional and a new criterion for myopia diagnosis in an epidemiological study.This school-based, cross-sectional study examined students from four key schools and seven non-key schools. Non-cycloplegic autorefraction and visual acuity (VA) were performed on each student. Myopia was defined as a spherical equivalent (SE) refractive error not better than -1.00 D. A questionnaire was also administered.Of the 13,220 students examined, 6,546 (49.5 per cent) had myopia using the criterion of SE not better than -1.00 D. However, 2,246 (34.3 per cent) of these myopes had VA ≥ 0 logMAR in both eyes, indicating they were not functioning as myopes. Thus, a second myopia criterion was adopted: SE refractive error not better than -1.00 D + uncorrected VA ≥ 0 logMAR in at least one eye. By this definition, only 32.5 per cent of the overall sample had myopia. Students in key schools had a higher prevalence of myopia than those in non-key schools (53.8 per cent versus 44.7 per cent) by the initial criterion. By the new criterion, the prevalence of myopia was 41.2 per cent versus 22.7 per cent. Myopia was equal in grade 1 of both school types, but accelerated faster in key schools, where there was a much higher prevalence of myopia by fourth grade, and continued up to 79.2 per cent prevalence by sixth grade based on SE refractive error not better than -1.00 D.Students in more competitive university-oriented elementary schools developed myopia much faster than those in regular schools, although they started with the same level of myopia. Since one-third of the 'myopes' had VA ≥ 0 logMAR in both eyes, they would not be prescribed a correction, or be clinically treated as myopes. A new criterion of SE refractive error not better than -1.00 D + uncorrected VA ≥ 0 logMAR in at least one eye was tested. This criterion is more clinically appropriate and could be used in future epidemiological studies.

Background: There has been no standardized questionnaire and objective criterion for assessing and diagnosing asthenopia so far. This study aimed to design a valid and reliable questionnaire to determine the various causes of asthenopia for use by clinicians and researchers. Methods: We developed a 19-item asthenopia questionnaire (AQ-19) in two phases. In the Design phase, 17 experts, 98 patients with asthenopia and 20 controls participated to generate the item list. We generated a comprehensive 52-item list to create our 1st version. The list included selected items based on a literature review, patient interviews and the Delphi experts method. In the Validation phase, we conducted a pilot test (127 patients and 25 controls) and retest (154 patients and 24 controls) for item reduction and a questionnaire validity assessment. Results: Our initial questionnaire contained 52 symptoms and 2 self-evaluation questions. After item reduction and assessment, we generated a 19-item questionnaire. It included 19 symptom items that were classified into three domains through factor analysis. Cronbach's α for the three subscales of this version were between 0.79 and 0.85, while for the complete questionnaire Cronbach's α was 0.90, with a split-half reliability of 0.80. Factor analysis showed the three components have eigenvalues > 3 and these explained 54.3% of the variance. Conclusions: The AQ-19 has acceptable psychometric properties, making it a valid and reliable tool for ophthalmologists and optometrists to evaluate asthenopia as well as to provide clues to find its causes. It provides three levels of information: (1) Identifies the presence of asthenopia. (2) Differentiates three major causal classifications (ocular-surface, systemic, and vision symptoms). (3) Focuses in on a specific cause. The clinician must still use his or her skills to determine the exact cause. The AQ-19 questionnaire has the potential to be used in clinical trials and outcome research, and most importantly to help clinicians efficiently and effectively diagnose the cause of a patient’s asthenopia. Trial registration: KYK [2016]8. Registered at 25 February 2016. Retrospectively registered. Keywords: Asthenopia, Reliability, Validity, Questionnaire, Delphi Method

Worldwide, more than one billion people suffer from poor vision because they do not have the eyeglasses they need. Their uncorrected refractive errors are a major cause of global disability and drastically reduce productivity, educational opportunities, and overall quality of life. The problem persists most prevalently in low-resource settings, even though prescription eyeglasses serve as a simple, effective, and largely affordable solution. In this review, we discuss barriers to obtaining, and approaches for providing, refractive eye care. We also highlight emerging technologies that are being developed to increase the accessibility of eye care. Finally,we describe opportunities that exist for engineers to develop new solutions to positively impact the diagnosis and treatment of correctable refractive errors in low-resource settings. Copyright © 2014 by Annual Reviews. All rights reserved., Financial support from the Madrid-MIT M+Vision Consortium and the MIT MISTI-India Global Seed Fund.

To compare the prevalence of pterygium and cataract in four indigenous populations of the Brazilian Amazonian rain forest (Arawak, Tukano, Maku, and Yanomami) with different ethnic and social behaviour backgrounds.A cross-sectional pterygium and cataract survey was performed in 624 adult Indians of the Brazilian rain forest belonging to four different ethnic groups. The Indians were classified according to their social behaviour in two groups: Arawak and Tukano (group 1) and Maku and Yanomami (group 2). Slit-lamp biomicroscopy was employed to examine the entire sample. All subjects were classified as 1 or 0 according to the presence or absence pterygium and cataract. Sex and age were also recorded.chi(2)-tests revealed that the prevalence of pterygium and cataract differed significantly between groups 1 and 2. For pterygia: 36.6% (97/265) and 5.0% (18/359), respectively (chi(2)=101.2, P0.0001), and for cataracts: 24.5% (65/265) and 13.7% (49/359) respectively (chi(2)=12.09, P=0.0005). Gender was not associated with pterygium (P=0.1326) and cataract (P=0.2263) in both groups. Elderly subjects showed a significantly higher prevalence of cataract (P0.0001). The prevalence of pterygia did not increase with age (P=0.8079) in both groups.Indians of group 1 have higher prevalence of pterygia and cataract than Indians of group 2. Social behaviour, especially the rate of sun exposure, appears to be the main factor for the different rates of pterygium and cataract displayed by these indigenous people of the Brazilian rain forest.

Purpose. The purpose of this study was to investigate accommodation, accommodative convergence, and AC/A ratios before and at the onset of myopia in children. Methods. Refractive error, accommodation, and phorias were measured annually over a period of 3 years in 80 6- to 18-year-old children (mean age at first visit = 11.1 years), including 26 who acquired myopia of at least -0.50 D and 54 who remained emmetropic (-0.25 to + 0.75 D). Refraction was measured by noncycloplegic distance retinoscopy. Concomitant measures of accommodation and phorias were taken for letter targets at 4.0 m and 0.33 m using the Canon R-1 open field-of-view autorefractor with an attached motorized Risley prism and Maddox rod. The accommodation and phoria measurements were used to calculate response AC/A ratios. Results. Compared with children who remained emmetropic, those who became myopic had elevated response AC/A ratios at 1 and 2 years before the onset of myopia, in addition to at onset and 1 year later (t's = -2.97 to -4.04, p < 0.01 at all times). The significantly higher AC/A ratios in the children who became myopic are a result of significantly reduced accommodation. Accommodative convergence was significantly greater in myopes only at onset. Conclusions. These findings suggest that the abnormal oculomotor factors found before the onset of myopia may contribute to myopigenesis by producing hyperopic retinal defocus when a child is engaged in near-viewing tasks.

Wavefront aberrations were measured using a psychophysical ray-tracing technique in both eyes of 316 emmetropic and moderately myopic school children and young adults. Myopic subjects were found to have greater mean root mean square (RMS) value of wavefront aberrations than emmetropic subjects. Emmetropic adults had the smallest mean RMS, which remained smaller than the values for myopic adults and children and for emmetropic children both when second order Zernike aberrations (astigmatism) and third order Zernike aberrations were removed. Twenty percent of myopic adults had RMS values greater than values for all of the emmetropic adults, with significantly greater values for Zernike aberrations from second to seventh orders. High amounts of wavefront aberrations, which degrade the retinal image, may play a role in the development of myopia.

The literature on myopigenesis suggests an active emmetropization mechanism regulated by optical defocus. The strongest evidence comes from compensatory ocular growth in response to lens-induced defocus in different species of animals. Based on these results, it has been suggested that, however useful, spectacle intervention for the optical correction of human myopia would lead to its exacerbation. The present study seeks to evaluate the progression of juvenile-onset myopia in children differentiated by their lens wear patterns. Data from 43 myopes from our longitudinal study of refraction were evaluated, with myopia defined as a spherical equivalent of at least -0.50 D. Refractions were obtained in the laboratory by noncycloplegic retinoscopy performed by one experienced optometrist at regular intervals. Information regarding the subjects' prescription lens-wearing history was obtained from the subjects and their eye care providers. Based on their wearing patterns, subjects were divided into four categories: (1) full-time wearers; (2) myopes who switched from distance to full-time wear; (3) distance wearers; and (4) nonwearers. Exponential functions were fit to the individual refraction data. The age of onset of myopia, the mean myopia at onset of spectacle wear, and the refractive shift over a period of at least 3 years were derived from these fits. Results show that the 3-year refractive shifts are not significantly different among the four groups. A comparison of the extreme conditions, i.e., full-time vs. nonwear categories, also revealed no significant difference when the data were corrected for age effects despite the fact that the nonwearers exhibited an age-adjusted 3-year progression approximately one-half that of the full-time wearers. In summary, the present study failed to demonstrate any overall effects of spectacle intervention on the progression of human myopia. Further investigation using a larger sample is warranted.

In the past year, as in recent years, most of the research on the development of refraction has focused on the following: 1) mechanisms whereby the eye can maintain coordinated growth to achieve emmetropia and 2) disruptions of emmetropization resulting in myopia or hyperopia. Preterm children and those with Down syndrome have higher refractive errors than other children, suggesting a failure of emmetropization. One of the most intriguing studies of the past year and one certain to lead to follow-up studies reported that ambient room illumination at night in a child's first two years is associated with a higher prevalence of myopia than sleeping in darkness. Reports on the development of hyperopia showed that it is axial in nature, similar to myopia. The effects of spectacle interventions to correct refractive errors are still being debated, with recent evidence from children suggesting that lenses do not exacerbate myopia. Analyses of risk factors and numerous new screening procedures detect patients with strabismus for referral at a variety of sensitivity and specificity levels. Hyperopia and high AC/A ratios are most clearly associated as causal agents for esotropia and intermittent exotropia. However, the action of even these simple mechanisms is confounded by abnormal binocular fusion mechanisms and the inability of optical correction to align the eyes of many patients. Asymmetric optokinetic nystagmus, latent nystagmus, and dissociated vertical deviation appear to be linked to infantile esotropia from before its onset. But the way the mechanisms underlying these oculomotor anomalies are causally related to the onset of infantile esotropia remains a mystery.

To use the Gompertz function to estimate the age and the amount of myopia at stabilization and to evaluate associated factors in the Correction of Myopia Evaluation Trial (COMET) cohort, a large ethnically diverse group of myopic children.The COMET enrolled 469 ethnically diverse children aged 6 to younger than 12 years with spherical equivalent refraction between -1.25 and -4.50 diopters (D). Noncycloplegic refraction was measured semiannually for 4 years and annually thereafter. Right eye data were fit to individual Gompertz functions in participants with at least 6 years of follow-up and at least seven refraction measurements over 11 years. Function parameters were estimated using a nonlinear least squares procedure. Associated factors were evaluated using linear regression.In total, 426 participants (91%) had valid Gompertz curve fits. The mean (SD) age at myopia stabilization was 15.61 (4.17) years, and the mean (SD) amount of myopia at stabilization was -4.87 (2.01) D. Ethnicity (P0.0001) but not sex or the number of myopic parents was associated with the age at stabilization. Ethnicity (P = 0.02) and the number of myopic parents (P = 0.01) but not sex were associated with myopia magnitude at stabilization. At stabilization, African Americans were youngest (mean age, 13.82 years) and had the least myopia (mean, -4.36 D). Participants with two versus no myopic parents had approximately 1.00 D more myopia at stabilization. The age and the amount of myopia at stabilization were correlated (r = -0.60, P0.0001).The Gompertz function provides estimates of the age and the amount of myopia at stabilization in an ethnically diverse cohort. These findings should provide guidance on the time course of myopia and on decisions regarding the type and timing of interventions.

Previously we reported that recently myopic children accommodated insufficiently to blur induced by negative lenses. The purpose of the present study was to relate changes in blur-driven accommodation to myopia development in children. Refractive errors and the accommodation response function (ARF) were measured in 23 myopic and 40 emmetropic children on two occasions separated by periods ranging from 6 to 12 months. Repeated measures of accommodation were made with a Canon R-1 autorefractor while negative lenses of increasing power were placed in front of the child's right eye viewing 20/100 letters at 4 m. Concomitant changes in refractive error and in accommodative function over periods of 6-12 months were found to be highly correlated in myopes (r = 0.77) but not in emmetropes (r = 0.09).

Knowing the actual behavior of readers will help us understand how near work influences a reader’s eyes, comfort, reading efficiency, pleasure, and the ability to learn to read. We designed a methodology for reading behavior research, and investigated the reading behavior of emmetropic schoolchildren in China and factors that influence their reading. Children from grades 2 through 5 read text in an armchair, at a desk, and when reading and writing at the desk with three different font sizes. Their preferred reading distance was very near to the eyes, averaging 28.5±6.4cm in the armchair, 25.4±6.6cm at the desk and 20.6±6.5cm in the reading/writing task, and was always slightly closer for the smallest font. Second grade children averaged just a 16.3±4.1cm reading distance in the reading/writing task. Head tilt and angle of gaze were altered by reading condition and font size. Reading speed was fastest at the desk and for those with longer reading distances and, surprisingly, for the smallest font size. Reading behavior is not a fixed entity but differs with grade level and reading condition. This suggests that reading behavior can be altered through better ergonomics and text design which may reduce myopia, aesthenopia, and binocular anomalies and help children read better.

Purpose To examine Chinese neonatal infants with both cycloplegic and noncycloplegic retinoscopy and to compare the distribution of refractive errors for the two techniques. Methods Cycloplegic retinoscopy was performed by two experienced pediatric ophthalmologists on 81 neonatal infants randomly selected from a group of 185 neonates who had undergone noncycloplegic retinoscopy. All infants were between 1 day and 6 days of age and were born without incident at full term. Results The mean cycloplegic spherical equivalent (CSE) was highly hyperopic (+3.55 diopters [D] ± 2.39 D). The mean noncycloplegic spherical equivalent (nCSE) was +0.58 D ± 2.32 D. The high reliability of the refractive measurements was demonstrated by high correlations between examiners (CSE: OD, r = 0.96; OS, r = 0.97; nCSE: OD, r = 0.94; OS, r = 0.93 OS) and between eyes (CSE: examiner 1, r = 0.94; examiner 2, r = 0.95; nCSE: examiner 1, r = 0.95; examiner 2, r = 0.97). The correlation between CSE and nCSE was much lower (examiner 1: OD, r = 0.76; OS, r = 0.73; examiner 2: OD, r = 0.72; OS, r = 0.70). Prevalence of astigmatism was very low (1.6% ≥ 1.0 D). Conclusions The level of hyperopia was very high in these infants, and the offsetting tonic accommodation demonstrated by the difference between CSE and nCSE was much higher than in any previous report. Low amounts of infantile hyperopia and high astigmatism are associated with future myopia in the West. The Chinese neonates in this study had high amounts of hyperopia and little astigmatism, yet they are at high risk to become myopic.

Increased prevalence of myopia has been documented worldwide, especially in industrialized regions (for a review, see Morgan and Rose 20051). East Asia leads this trend, which is characterized by early onset of myopia and an increase in the prevalence of high myopia.1–3 High myopia may be associated with severe ocular complications such as glaucoma, retinal detachment or blindness and thus poses a severe public health burden.4 It is clear that the etiology of myopia is multi-factorial, with both genetic and environmental factors contributing to its development. Evidence for a genetic role includes a higher risk of developing juvenile myopia among children with myopic parents5–8 and a high positive correlation in refractive error between siblings and between parents and children.9,10 The environmental risk factor most often cited for myopia is near work, though direct evidence of an association between near work and myopia has been lacking. Much of the existing evidence is provided by epidemiological studies11–12 and by prospective studies of the onset and progression of myopia in near work-intensive academic or occupational groups.13–15 Faster myopic progression after three years of follow-up was found to be positively associated with more hours of reading.16 Assessment of near work typically has been by questionnaire, with some studies reporting a slight association between near work activities and myopia in children. Children in Singapore with more than 3 D of myopia were reported to read significantly more than the median of 2 books per week and to engage in significantly more hours of daily near work than lower myopes and non-myopes.8 A greater amount of near work had a small independent contribution to myopia in a U.S. sample of children.6 However, after six years of follow-up of the same cohort, no significant association between myopia development and near-work activities was observed.17 A longitudinal study of children in Singapore did not find a significant correlation between the annual change in refraction and the total near work hours in school.18 Regional differences have been reported, with a lower prevalence of myopia and significantly more hours of total near work activity found among Chinese children in Sydney compared to Singapore.19 A number of factors may contribute to the discrepancy in these conclusions including differences in study design, children’s ages and ethnicity, definitions of near work and myopia, and accuracy of the self-reported or parent-reported activity times. In addition, other factors such as viewing distance, lighting, and temporal factors (e.g., frequency of looking up from text and taking breaks) may be more sensitive indicators than the typically reported hours of near work. Unlike for near work, most publications agree on a protective role of outdoor activity in myopia development as reported in questionnaires.6–7,17,20–21 In a longitudinal study in the U.S., children with more hours of sports/outdoor activity had a lower incidence of myopia than those with fewer hours.17 The Sydney myopia study reported more outdoor activity time in children with more positive refractive errors.7 Recently, myopic teenagers in Singapore were found to have significantly fewer outdoor activity hours than non-myopes.21 Only one recent study from China failed to find an association between refractive error and outdoor activity.22 In this paper we investigate hours spent on various visual activities in myopes and non-myopes during the school year and the summer break (June, July and August) using survey data from subjects who participated in a longitudinal study of refraction and visual development. A preliminary report of this work has been presented previously.23, 24

We compared the effects of dioptric blur on Snellen acuity and grating acuity. Dioptric blur had a strong negative effect on Snellen acuity, consistent with previous studies, but had little effect on grating acuity. Between 1 and 12 D both types of acuity were reduced as a linear function of blur. However, 12 D of blur reduced grating acuity to only 6/24 (20/80), whereas letter acuity was worse than 6/300 (20/1000). We suggest that these differences are due to the presence of "spurious resolution" in which phase-reversed gratings are readily detectable. But the phase reversals so distort the relative positions of linear segments within the letters that the letters become unrecognizable. These results indicate that Snellen letters are more sensitive than gratings to a patient's refractive errors, emphasize the differences between Snellen and grating acuity, and indicate that the minimum angle of resolution (MAR) concept is not applicable to letters.

We studied the effect of dioptric blur on contrast sensitivity using the Vistech Vision Contrast System Chart. One diopter of blur affected the Vistech gratings by an amount consistent with expectations; sensitivity loss was greatest with higher spatial frequencies. However, a second diopter of blur induced an equal sensitivity loss for all spatial frequencies. A third diopter induced the greatest loss at the lowest frequency and an actual increase in sensitivity at the highest frequencies. This surprising finding is due to an interaction between "spuriously resolved" gratings and the border of the grating disc which resulted in the finest grating discs appearing to contain low frequency borders aligned with the fine gratings. Actually the fine gratings in the disc were invisible. When performing scanning photometry on the Vistech chart, we found that the contrasts of the unblurred gratings with higher contrast levels are 2.7 to 5.4 times higher than those stated by the manufacturer. The presence of this aliasing artifact indicates that the Vistech Vision Contrast System may produce erroneous results when used under conditions of high dioptric blur.

The purpose of this study was to investigate the refractive status of the illiterate indigenous people of the upper Rio Negro region of the Amazon rain forest in northwestern Brazil.From an overall sample of 486 people, 259 indigenous people and 78 Brazilians between 12 and 59 years of age with no compromising optical opacities were refracted with cycloplegic retinoscopy. Subjects were categorized as indigenous if they had at least three generations of indigenous ancestry with no folklore suggesting other ancestors.Myopia was rare among the indigenous population. Only 2.7% of eyes showed myopia of -1.00 D or more and 1.6% (four people) had bilateral myopia of -1.00 D or more. Half of this small group were the only educated indigenous people examined. The prevalence of astigmatism and anisometropia equal to or1.00 D was 15.5% and 8.2%, respectively. Most of the astigmatism in the indigenous people had an against-the-rule axis. Age was not associated with the refractive errors of the indigenous people. Brazilians from the small city in which the study was performed had higher rates of myopia (6.4% of eyes and 5.1% of subjects bilaterally). Older preeducation adults also had a very low prevalence of myopia (3.2% of eyes and 2.0% of subjects), whereas the younger, slightly educated Brazilians had a higher prevalence of myopia (11.3% of eyes and 9.7% of subjects).The low prevalence of myopia in the illiterate indigenous people is consistent with other studies and suggests that myopia is related to literacy. The generational change among the local mixed race Brazilians further supports this conclusion. The relatively high rates of astigmatism and anisometropia in the indigenous people were unusual for a predominantly emmetropic sample.

Purpose Patients with socially significant strabismus may be at risk for certain psychosocial consequences. However, the magnitude at which strabismus becomes socially significant is ill defined. Suggested criteria for socially significant strabismus can be found in the literature, but they are rarely, if ever, referenced. The purpose of this study is to further define the magnitude at which strabismus becomes socially significant according to lay observers. Methods Strabismus was simulated using photo manipulation and off-center fixation. Horizontal deviations were created in 3Delta steps up to 24Delta. One model was used for all photos. The photos were presented in random order to non-health care professionals (N = 58). Participants were instructed to view each picture and determine: "yes, this person has an eye turn" or "no, this person does not have an eye turn." A chi test was used for analysis. RESULTS.: There was an increase in the likelihood of strabismus detection as the size of the angle increased for exotropia and esotropia. Overall, exotropia was easier to identify than esotropia. For esotropia, a dramatic increase in detectability occurred between 9Delta (47.41% detection; p = 0.001) and 12Delta (67.24% detection; p = 0.001), with 70% detection being achieved at 14.5Delta. A significant increase in detection of exotropia occurred between 6Delta (60.34% detection; p = 0.001) and 9Delta (77.59% detection; p = 0.001), with 70% detection achieved at 8Delta. Conclusions Our results suggest that exotropia is easier for lay observers to detect than esotropia, with the critical magnitude (70% detection) being 14.5Delta for esotropia and 8Delta for exotropia. This refutes generally accepted beliefs that esotropia is easier to detect than exotropia. Additional studies are needed to look at the effect of ethnicity, sex, and age. Multiple models should be used to reduce the possible influence of distinct facial characteristics and increase the generalizability of the results.

Accommodative lags, induced by a target at 33 cm (distance-induced condition) and by a -3.0 D lens (lens-induced condition), and wavefront aberrations were measured in 27 young myopic eyes. The accommodative lags and Strehl ratios derived from the wavefront aberrations in myopes were compared with those from 57 emmetropes. Accommodation was measured using a Canon R-1 autorefractor, while aberrations were measured using a psychophysical ray-tracing technique. In accord with previous results, larger accommodative lags were found for the myopes than the emmetropes in both the lens-induced and distance-induced conditions. The mean Strehl ratio was smaller in the myopes (0.079) than the emmetropes (0.091); this difference approached significance (p = 0.055). In addition, for myopes the accommodative lag was significantly correlated with the Strehl ratio in the lens-induced condition (r = -0.45, p0.02) and approached significance in the distance-induced condition (r = -0.35, p = 0.07). No significant correlations were found for emmetropes. Possible reasons to account for these results are discussed.

Infants have been found to have a high prevalence of astigmatism, which is greatly reduced or eliminated during the first 2 years of life. However, little is known about the functional significance, if any, of the early astigmatism. In this study we investigated the possible role of early astigmatism in emmetropization and the later development of refractive errors. Subjects included 245 children with an initial refraction in the first yew and from 6 to 23 years of regular follow-up in our laboratory. Almost half of the 0 to 6 month-old infants showed significant astigmatism (1D or more), but the prevalence declined sharply thereafter. Against-the-rule astigmatism was associated with more myopia or less hyperopia in the first year and again at school age after an intervening period of emmetropization. Reduction of cylinder power between the ages of 6 months and 6 years was only slightly correlated with the rate of change in spherical equivalent over the same age range, while the rate of change in the two measures between 6 and 12 years was more highly correlated. Between 6 and 12 years spherical equivalent became more negative for most children, while cylinder power increased slightly. These results suggest independence of processes underlying corneal change and axial growth during the emmetropization period from infancy to 6 years, but they suggest that the changes occurring during the period between 6 and 12 years may be interdependent.

Both inheritance and visual experience contribute to the de of myopia. The blur hypothesis, which asserts that myopia may be iuduced by ahnormal levels of or sensitivity to retinal image blur, can be used to describe how nature may work together to induce myopia. Each physiological mechanism that in uceu blurred vision may be inherited and most of these can act as parallel causal links connecting near work with the mechanisms that translate a blurred image into axial myopia.

In children little is known about the relationship between the AC/A ratio and the development of myopia, although they have been linked in adults. The purpose of this study was to investigate the interaction between accommodation and convergence and its relationship to refractive errors in children. Accommodation was measured for the right eye using the Canon R-1 autorefractor, and concomitant changes in vergence were assessed using a Maddox rod and a Risley prism before the left eye. Thirty-three myopic and 68 emmetropic children were tested wearing best subjective correction while looking at a distant (4.0 m) letter array and a near (0.33 m) one through additional plus and minus lenses. Lens-induced and distance-induced response AC/A ratios were calculated from the data. Both types of AC/A ratios are elevated in myopic children, who show reduced accommodation and enhanced accommodative convergence. Myopic children with esophoria underaccommodate at near. This suggests that a child who is esophoric must relax accommodation to reduce accommodative convergence and maintain single binocular vision. The reduction in accommodation could produce blur during near work, which could induce myopia as in animal models.

Our laboratory has shown that myopic children accommodate less than emmetropic children of the same age to lens-induced blur (Gwiazda et al, 1993).

The prevalence of astigmatism in infants and young children is substantially higher than in the adult population, but the functional significance of this early astigmatism remains obscure.