Elementary school comprehensive intervention and myopia development: the Wenzhou Epidemiology of Refraction Error Study.

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 (<30 cm) in the intervention group was less than in the control group (73.4% vs 76.2%, P<0.001), the percentage of everyday perform eye exercises in the intervention group was more than in the control group (27.8% vs 20.7%, P<0.001) 30mo later. CONCLUSION: The comprehensive intervention program at elementary school has a significant alleviating effect on myopia progression for children during the 2.5y follow-up, especially for those non-myopia at baseline.

Resilience of temporal processing to early and extended visual deprivation.

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.

A Nurse's Perspective on Visual Rehabilitation of Outpatients With Low Vision in China.

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.

Refractive status and prevalence of myopia among Chinese primary school students.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

The Needs for Visual Improvement of Patients Presented at Low-Vision Center in Wenzhou, China.

PURPOSE: To characterize the needs for visual improvement of new-visit patients with low vision. METHODS: This cross-sectional study collected detailed information of patients presented at low-vision center of the Eye Hospital of Wenzhou Medical University between January 2015 and January 2017. A questionnaire interview, including demographic information and needs for visual improvement, was conducted before ophthalmology examinations. RESULTS: The main need for visual improvement was engagement in hobbies (68.9%), followed by reading (20.9%), engaging in occupation (20.1%), and watching TV or movies (17.1%). Less than 10% of patients mentioned the demand of using public transportation (5.8%), doing housework (3.7%), writing (1.9%), walking on irregular surfaces (1.5%), driving (1.1%), and others (2.4%). Women were significantly associated with a concern for performing hobbies (OR 1.45, 95% CI 1.0-2.0) but associated with lower odds of reading (OR 0.46, 95% CI 0.3-0.7). Older subjects were more willing to choose hobbies (OR 1.35 (per 10-year increase), 95% CI 1.3-1.4), reading (OR 1.11 (per 10-year increase), 95% CI 1.0-1.2), watching TV or movies (OR 1.4 (per 10-year increase), 95% CI 1.3-1.6), and housework (OR 1.21 (per 10-year increase), 95% CI 1.0-1.5) than younger individuals. In comparison with younger participants, older individuals were less likely to choose occupation (OR 0.53 (per 10-year increase), 95% CI 0.5-0.6). No significant association was found between visual acuity and needs for visual improvement. CONCLUSION: Hobbies, reading, engaging in occupation, and watching TV were the most common needs for visual rehabilitation in patients with visual impairment. Gender and age showed a modest influence on the choice of different needs.

Retinal Microvasculature in Amblyopic Children and the Quantitative Relationship Between Retinal Perfusion and Thickness.

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.

Vergence driven accommodation with simulated disparity in myopia and emmetropia.

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, 22-31 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.

Short-Term Effects of Overnight Orthokeratology on Corneal Sensitivity in Chinese Children and Adolescents.

PURPOSE: To assess the effects of the 3-month period of orthokeratology (OK) treatment on corneal sensitivity in Chinese children and adolescents. METHODS: Thirty subjects wore overnight OK lenses in both eyes for 3 months and were assessed at baseline, 1 day, 1 week, 1 month, and 3 months after the treatment. Changes in corneal sensitivity were measured by the Cochet-Bonnet (COBO) esthesiometer at the corneal apex and approximately 2 mm from the temporal limbus. Changes in refraction and corneal topography were also measured. RESULTS: Central corneal sensitivity suffered a significant reduction within the first month of the OK treatment period but returned to the baseline level at three months (F = 3.009, P=0.039), while no statistically significant difference occurred in temporal sensitivity (F = 2.462, P=0.074). The baseline of central corneal sensitivity correlated with age (r = -0.369, P=0.045). A marked change in refraction (uncorrected visual acuity, P < 0.001; spherical equivalent, P < 0.001) and corneal topographical condition (mean keratometry reading, P < 0.001; eccentricity value, P < 0.001; Surface Regularity Index, P < 0.001) occurred, but none of these measurements were correlated with corneal sensitivity. CONCLUSIONS: A 3-month period OK treatment causes a reduction in central corneal sensitivity in Chinese children and adolescents but with a final recovery to the baseline level, which might be because neuronal adaptation occurred earlier in children and adolescents than in adults.

Peripheral contrast sensitivity and attention in myopia.

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±2.6years) 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.

Rapid Integration of Tactile and Visual Information by a Newly Sighted Child.

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.

Design and Clinical Evaluation of a Handheld Wavefront Autorefractor.

PURPOSE: To introduce a novel autorefractor design that is intended to be manufacturable at low cost and evaluate its performance in measuring refractive errors. METHODS: We developed a handheld, open-view autorefractor (the "QuickSee" [QS]) that uses a simplified approach to wavefront sensing that forgoes moving parts and expensive components. Adult subjects (n = 41) were recruited to undergo noncycloplegic refraction with three methods: (1) a QS prototype, (2) a Grand Seiko WR-5100K (GS) autorefractor, and (3) subjective refraction (SR). Agreements between the QS and GS were evaluated using a Bland-Altman analysis. The accuracy of both autorefractors was evaluated using SR as the clinical gold standard. RESULTS: The spherical equivalent powers measured from both autorefractors correlate well with SR, with identical correlation coefficients of r = 0.97. Both autorefractors also agree well with each other, with a spherical equivalent power 95% confidence interval of ±0.84 diopters (D). The difference between the accuracy of each objective device is not statistically significant for any component of the power vector (p = 0.55, 0.41, and 0.18, for M, J0, and J45, respectively). The spherical and cylindrical powers measured by the GS agree within 0.25 D of the SR in 49 and 82% of the eyes, respectively, whereas the spherical and cylindrical powers measured by the QS agree within 0.25 D of the SR in 74 and 87% of the eyes, respectively. CONCLUSIONS: The prototype autorefractor exhibits equivalent performance to the GS autorefractor in matching power vectors measured by SR.

From unseen to seen: tackling the global burden of uncorrected refractive errors.

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.

Reading behavior of emmetropic schoolchildren in China.

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.

Cycloplegic and noncycloplegic refractions of Chinese neonatal infants.

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.

Children's refractions and visual activities in the school year and summer.

PURPOSE: To investigate the association of children's refractive errors with their visual activities assessed by questionnaire in the school year and summer break (June, July, and August). METHODS: The parents of 147 children aged 6 to 18 years participating in a longitudinal study of refraction and visual function filled out a questionnaire in 1999 listing the number of weekly hours outside of school that the children read for pleasure, studied, watched TV, used the computer/played video games, and engaged in sports/outdoor activities. They also provided hours for these activities during the summer break. Refractions were measured annually by non-cycloplegic distance retinoscopy. Myopes refer to subjects who were myopic (spherical equivalent < -0.5 diopter) at the time of the survey and non-myopes (spherical equivalent refraction > or = -0.5 diopter) were emmetropic or in a few cases hyperopic at survey time. RESULTS: During the school year, myopes spent significantly fewer hours (8.25 +/- 6.24 h/week) than non-myopes (10.95 +/- 5.95 h/week) in sports/outdoor activity (p < 0.05). In addition, myopes (12.78 +/- 9.28 h/week) watched more television than non-myopes (8.91 +/- 5.95 h/week) (p = 0.02). No significant refractive group differences were found for other activities. During the summer break, no significant differences were found between refractive groups in any visual activity times. No significant correlations between sports/outdoor activity and TV time were found. Overall, the biggest differences between summer and school activity times were found in outdoor activity (21.76 +/- 13.80 vs.10.34 +/- 6.10 h/week; p < 0.001) and studying (1.69 +/- 3.71 vs. 9.51 +/- 6.96 h/week; p < 0.001). CONCLUSIONS: In agreement with other studies, the non-myopes had more hours of sports/outdoor activity during the school year, which may protect against myopia development. A new finding is the high number of sports/outdoor activity hours for both myopes and non-myopes during the summer break, which may contribute to slowed eye growth in all children during these 3 months.

Characteristics of accommodative behavior during sustained reading in emmetropes and myopes.

Accommodation has long been suspected to be involved in the development of myopia because near work, particularly reading, is known to be a risk factor. In this study, we measured several dynamic characteristics of accommodative behavior during extended periods of reading under close-to-natural conditions in 20 young emmetropic and stable myopic subjects. Accommodative responses, errors, and variability (including power spectrum analysis) were analyzed and related to accommodative demand and subject refractive error. All accommodative behaviors showed large inter-subject variability at all of the reading demands. Accommodative lags and variability significantly increased with closer demands for all subjects (ANOVA, p<0.05). Myopes had significantly greater variability in their accommodation responses compared to emmetropes (ANOVA, p<0.05) and had larger accommodative lags at further reading distances (unpaired t test p<0.05). Power spectrum analysis showed a significant increase in the power of accommodative microfluctuations with closer demands (ANOVA, p<0.05) and with increasing myopia at the closest reading demand (ANOVA, p<0.01). The difference in the stability of the accommodative behavior between individuals with different refractive states suggests a possible relationship between variability in accommodation and the development of myopia.

Myopia progression is specified by a double exponential growth function.

PURPOSE: The purpose of this study was to demonstrate how well a modified Gompertz double exponential growth function delineates the diverse courses of myopia progression found in individual eyes. The function is: R = Re + Rc(0.07295)(a(x - t0)) where the spherical equivalent refractive error at a given age R equals the initial refractive error (Re) plus the overall refractive change (Rc) times a double exponential function with the base (0.07295) representing the proportion of Rc that occurs when maximum acceleration is reached, a is a curvature coefficient, t0 is the age of onset and x is age. METHODS: This function was fit to longitudinal refractive data (spherical equivalents) for both eyes of 36 myopic children. The fits were required to meet a stringent set of criteria, including fitting transitions in and out of myopia progression and having no systematic errors or arbitrary constants. RESULTS: Correlation between values on the refractive function and corresponding data of individual eyes is high (mean r = 0.973 +/- 0.020), the sum of squares between the data and function is low, and all other criteria are met. The rates of refractive change and acceleration were derivable from this function. It has been shown that, if peak acceleration rate is used as a criterion for the onset of myopia progression, then myopization onset starts a year earlier (mean = 8.93 years) than when a -0.50-D onset criterion is used (mean = 9.93 years), and it usually starts before the spherical equivalent reaches zero (mean R = +0.09 D). Age of onset is highly correlated with the duration of myopia progression (r = 0.693), which in turn is correlated with the amount of myopia achieved (r = 0.443). CONCLUSIONS: We demonstrate that the double exponential function delineates the dynamics of myopia progression onset, offset, and the derivatives that describe the mechanisms underlying the growth process that causes myopia and have explained the advantages of this function. The function can be used to more accurately portray the course of individual subject's myopic progression.

Refractive status of indigenous people in the northwestern Amazon region of Brazil.

PURPOSE: 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. METHODS: 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. RESULTS: 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 or >1.00 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). CONCLUSION: 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.

Accommodation, accommodative convergence, and response AC/A ratios before and at the onset of myopia in children.

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.

The association of wavefront aberration and accommodative lag in myopes.

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, p < 0.02) 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.