Yangfa Zeng

Effect of Time Spent Outdoors at School on the Development of Myopia Among Children in China: A Randomized Clinical Trial

IMPORTANCE Myopia has reached epidemic levels in parts of East and Southeast Asia. However, there is no effective intervention to prevent the development of myopia. OBJECTIVE To assess the efficacy of increasing time spent outdoors at school in preventing incident myopia. DESIGN, SETTING, AND PARTICIPANTS Cluster randomized trial of children in grade 1 from 12 primary schools in Guangzhou, China, conducted between October 2010 and October 2013. INTERVENTIONS For 6 intervention schools (n = 952 students), 1 additional 40-minute class of outdoor activities was added to each school day, and parents were encouraged to engage their children in outdoor activities after school hours, especially during weekends and holidays. Children and parents in the 6 control schools (n = 951 students) continued their usual pattern of activity. MAIN OUTCOMES AND MEASURES The primary outcome measure was the 3-year cumulative incidence rate of myopia (defined using the Refractive Error Study in Children spherical equivalent refractive error standard of ≤-0.5 diopters [D]) among the students without established myopia at baseline. Secondary outcome measures were changes in spherical equivalent refraction and axial length among all students, analyzed using mixed linear models and intention-to-treat principles. Data from the right eyes were used for the analysis. RESULTS There were 952 children in the intervention group and 951 in the control group with a mean (SD) age of 6.6 (0.34) years. The cumulative incidence rate of myopia was 30.4% in the intervention group (259 incident cases among 853 eligible participants) and 39.5% (287 incident cases among 726 eligible participants) in the control group (difference of -9.1% [95% CI, -14.1% to -4.1%]; P < .001). There was also a significant difference in the 3-year change in spherical equivalent refraction for the intervention group (-1.42 D) compared with the control group (-1.59 D) (difference of 0.17 D [95% CI, 0.01 to 0.33 D]; P = .04). Elongation of axial length was not significantly different between the intervention group (0.95 mm) and the control group (0.98 mm) (difference of -0.03 mm [95% CI, -0.07 to 0.003 mm]; P = .07). CONCLUSIONS AND RELEVANCE Among 6-year-old children in Guangzhou, China, the addition of 40 minutes of outdoor activity at school compared with usual activity resulted in a reduced incidence rate of myopia over the next 3 years. Further studies are needed to assess long-term follow-up of these children and the generalizability of these findings. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00848900.

Early changes in clear cornea incision after phacoemulsification: an anterior segment optical coherence tomography study

Purpose:  We aimed to investigate the ultrastructures of clear corneal incisions 24 hours after phacoemulsification using anterior segment optical coherence tomography (AS‐OCT).

Increases in the prevalence of reduced visual acuity and myopia in Chinese children in Guangzhou over the past 20 years

Background/aimsTo estimate the prevalence of myopia based on reduced unaided visual acuity (VA) in Chinese school children over the past 20 years.MethodsGuangzhou school health authorities have measured VA on Grade 1–12 students from 1988 to 2007 annually, using a LogMAR tumbling E chart. VA is reported as Snellen categories: normal (VA≥6/6), mildly reduced (6/9<VA<6/6), moderately reduced (6/18<VA≤6/9), and severely reduced VA (VA≤6/18).ResultsIn 1988, over 80% of children in Grade 1 (age 6 years) and about 30% in Grade 12 (age 17 years) had normal unaided VA. By 2007, this dropped to only 60% in Grade 1 and about 10% in Grade 12. Conversely, the prevalence of moderately and severely reduced unaided VA increased from 6.2% in Grade 1 and 62.5% in Grade 12 in 1988 to 14.5% in Grade 1 and 84.11% in Grade 12 in 2007. This rate was unchanged from 2003 to 2007 at both the Grade 1 and Grade 12 levels.ConclusionsIn Guangzhou, the prevalence of reduced unaided VA has increased markedly in the past 20 years, but has stabilized in the past few years. This increase may result from environmental changes, such as increased schooling intensity and urbanization.

The child self-refraction study results from urban Chinese children in Guangzhou

OBJECTIVE To compare visual and refractive outcomes between self-refracting spectacles (Adaptive Eyecare, Ltd, Oxford, UK), noncycloplegic autorefraction, and cycloplegic subjective refraction. DESIGN Cross-sectional study. PARTICIPANTS Chinese school-children aged 12 to 17 years. METHODS Children with uncorrected visual acuity ≤ 6/12 in either eye underwent measurement of the logarithm of the minimum angle of resolution visual acuity, habitual correction, self-refraction without cycloplegia, autorefraction with and without cycloplegia, and subjective refraction with cycloplegia. MAIN OUTCOME MEASURES Proportion of children achieving corrected visual acuity ≥ 6/7.5 with each modality; difference in spherical equivalent refractive error between each of the modalities and cycloplegic subjective refractive error. RESULTS Among 556 eligible children of consenting parents, 554 (99.6%) completed self-refraction (mean age, 13.8 years; 59.7% girls; 54.0% currently wearing glasses). The proportion of children with visual acuity ≥ 6/7.5 in the better eye with habitual correction, self-refraction, noncycloplegic autorefraction, and cycloplegic subjective refraction were 34.8%, 92.4%, 99.5% and 99.8%, respectively (self-refraction versus cycloplegic subjective refraction, P<0.001). The mean difference between cycloplegic subjective refraction and noncycloplegic autorefraction (which was more myopic) was significant (-0.328 diopter [D]; Wilcoxon signed-rank test P<0.001), whereas cycloplegic subjective refraction and self-refraction did not differ significantly (-0.009 D; Wilcoxon signed-rank test P = 0.33). Spherical equivalent differed by ≥ 1.0 D in either direction from cycloplegic subjective refraction more frequently among right eyes for self-refraction (11.2%) than noncycloplegic autorefraction (6.0%; P = 0.002). Self-refraction power that differed by ≥ 1.0 D from cycloplegic subjective refractive error (11.2%) was significantly associated with presenting without spectacles (P = 0.011) and with greater absolute power of both spherical (P = 0.025) and cylindrical (P = 0.022) refractive error. CONCLUSIONS Self-refraction seems to be less prone to accommodative inaccuracy than noncycloplegic autorefraction, another modality appropriate for use in areas where access to eye care providers is limited. Visual results seem to be comparable. Greater cylindrical power is associated with less accurate results; the adjustable glasses used in this study cannot correct astigmatism. Further studies of the practical applications of this modality are warranted. FINANCIAL DISCLOSURE(S) Proprietary or commercial disclosure may be found after the references.

Predictors of Early Acceptance of Free Spectacles Provided to Junior High School Students in China

OBJECTIVE To examine factors influencing adherence to spectacle wear and perceived value within a prospective 1-month trial of ready-made and custom spectacles in school-aged children with uncorrected refractive error in urban China. METHODS A total of 428 students aged 12 to 15 years with at least 1 diopter of uncorrected refractive error were given free spectacles and evaluated 1 month later at an unannounced visit. Demographic factors, vision, optical effects, and perceptions were modeled as predictors of observed use and perceived value using logistic regression adjusted for spectacle allocation. RESULTS Of 415 students, 388 (93.5%) planned to use their spectacles, 227 (54.7%) valued their spectacles highly, 204 (49.2%) had their spectacles on hand, and 13 (3.0%) were lost to follow-up. Female students were 1.72 times (95% confidence interval [CI], 1.10-2.68), students from lower income households were 1.78 times (1.32-2.39), and those not concerned over appearance were 2.04 times (1.25-3.36) more likely to have spectacles on hand. Students with a pupil size of 4 mm or greater were 2.55 times (95% CI, 1.61-4.03) and students with spectacle vision worse than 20/20 were 2.06 times (1.20-3.49) more likely to have spectacles on hand. Self-report of high perceived value was 2.23 times (95% CI, 1.30-3.80) more likely with 20/20 spectacle vision, 1.63 times (1.06-2.52) more likely with base-in prismatic effects of 0.5 prism diopters or more, 3.52 times (2.03-6.13) more likely when students would not tolerate blur to avoid wearing spectacles, and 2.16 times (1.24-3.76) more likely with disbelief that spectacles would make vision worse. Spectacle type had no effect. CONCLUSIONS Although most students planned to use their spectacles, only half were observed using them. Day-to-day use might increase if students were less concerned over appearance. Optical factors and beliefs surrounding spectacles are also predictive of acceptance. These findings provide further understanding of spectacle acceptance in teenagers.

Comparison of lens thickness measurements using the anterior segment optical coherence tomography and A-scan ultrasonography.

PURPOSE To assess lens thickness (LT) measurements with anterior segment optical coherence tomography (AS-OCT) in comparison with A-scan ultrasonography (A-scan US). METHODS Enrolled were 66 eyes of 48 phakic elderly volunteers aged > or = 50 years and 56 eyes of 56 young participants aged 18 to 40 years. LT was measured with the internal manual caliper tools in AS-OCT. The A-scan US measurements were based on an average of 10 consecutive automatic measurements. Reproducibility was assessed by three measurements each with AS-OCT and A-scan US independently obtained by two observers who were masked to one anothers results. RESULTS The failure rates of AS-OCT and A-scan US were 9.1% and 7.6%, respectively, in elderly subjects, but no failure was observed in young subjects. The LT values measured by AS-OCT were significantly greater than A-scan US; the paired difference was 0.135 mm in elderly and 0.101 mm in young subjects (P < 0.001). These differences did not correlate with the nuclear cataract grades (r = 0.078, P = 0.558). Intraobserver agreement on AS-OCT (95% limits of agreement [LoA]: -0.049 to +0.045 mm; ICC: 0.999) was better than A-scan US (95%LoA: -0.194 to +0.218 mm; ICC: 0.974). The 95% LoA of interobserver agreement using AS-OCT and A-scan were -0.084 to +0.073 and -0.278 to +0.239 mm, respectively, and the ICCs were 0.996 and 0.960, respectively. CONCLUSIONS AS-OCT can be used to measure lens thickness in most eyes with clear or opacified lenses. It appears to be an alternative means of measuring lens thickness, particularly when a noncontact method is needed.

Normative Distribution of Visual Acuity in 3- to 6-Year-Old Chinese Preschoolers: The Shenzhen Kindergarten Eye Study

PURPOSE To document the distribution of uncorrected visual acuity (UCVA) in a defined population of Chinese preschoolers and to discuss its implications for vision referral. METHODS Preschoolers aged 3 to 6 years old were recruited from kindergartens in Shenzen. Uncorrected visual acuity was estimated by using Early Treatment Diabetic Retinopathy Study Tumbling E charts, followed by cycloplegic refraction and ocular examination. The reference population was defined as children without clinically significant ocular abnormalities, with spherical equivalent refraction greater than -0.50 to less than +2.00 diopters (D), astigmatism less than 0.75 D, and anisometropia less than 2.00 D. The age-specific UCVA cutoffs were defined by the line where the single-sided 95th percentile of the reference population fell. RESULTS A total of 483 of the 1255 children enrolled were considered the reference population. The monocular UCVA cutoff fell on the line of 20/63 at age 3, 20/50 at age 4, and 20/40 at ages 5 and 6. Using no better than these lines as criteria generated referral rates of 9.4% to 27.8% in the general population at different ages, and detected 83.3% and more than 90.0% of those with myopia and amblyopia, respectively. Using uncorrected interocular difference of two or more lines referred 3.6% to 4.3% of the population but identified only approximately 20.0% of those with amblyopia. CONCLUSIONS Visual acuity is still developing in preschoolers even at age 6. Most children with myopia and amblyopia can be identified with age-specific, monocular UCVA cutoffs in vision screening using Tumbling E charts, with tolerable false-positive rates. Further studies are needed to define the age at which children without significant refractive errors reach 20/20 UCVA.

Determinants and two-year change in anterior chamber angle width in a Chinese population

OBJECTIVE To study the population distribution and longitudinal changes in anterior chamber angle width and its determinants among Chinese adults. DESIGN Prospective cohort, population-based study. PARTICIPANTS Persons aged 35 years or more residing in Guangzhou, China, who had not previously undergone incisional or laser eye surgery. METHODS In December 2008 and December 2010, all subjects underwent automated keratometry, and a random 50% sample had anterior segment optical coherence tomography with measurement of angle-opening distance at 500 μm (AOD500), angle recess area (ARA), iris thickness at 750 μm (IT750), iris curvature, pupil diameter, corneal thickness, anterior chamber width (ACW), lens vault (LV), and lens thickness (LT) and measurement of axial length (AL) and anterior chamber depth (ACD) by partial coherence laser interferometry. MAIN OUTCOME MEASURES Baseline and 2-year change in AOD500 and ARA in the right eye. RESULTS A total of 745 subjects were present for full biometric testing in both 2008 and 2010 (mean age at baseline, 52.2 years; standard deviation [SD], 11.5 years; 53.7% were female). Test completion rates in 2010 varied from 77.3% (AOD500: 576/745) to 100% (AL). Mean AOD500 decreased from 0.25 mm (SD, 0.13 mm) in 2008 to 0.21 mm (SD, 13 mm) in 2010 (difference, -0.04; 95% confidence interval [CI], -0.05 to -0.03). The ARA decreased from 21.5 ± 3.73 10(-2) mm(2) to 21.0 ± 3.64 10(-2) mm(2) (difference, -0.46; 95% CI, -0.52 to -0.41). The decrease in both was most pronounced among younger subjects and those with baseline AOD500 in the widest quartile at baseline. The following baseline variables were significantly associated with a greater 2-year decrease in both AOD500 and ARA: deeper ACD, steeper iris curvature, smaller LV, greater ARA, and greater AOD500. By using simple regression models, we could explain 52% to 58% and 93% of variation in baseline AOD500 and ARA, respectively, but only 27% and 16% of variation in 2-year change in AOD500 and ARA, respectively. CONCLUSIONS Younger persons and those with the least crowded anterior chambers at baseline have the largest 2-year decreases in AOD500 and ARA. The ability to predict change in angle width based on demographic and biometric factors is relatively poor, which may have implications for screening. FINANCIAL DISCLOSURE(S) The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Two-year changes in refractive error and related biometric factors in an adult Chinese population

IMPORTANCE This article provides, to our knowledge, the first longitudinal population-based data on refractive error (RE) in Chinese persons. OBJECTIVE To study cohort effects and changes associated with aging in REs among Chinese adults. DESIGN, SETTING, AND PARTICIPANTS A 2-year, longitudinal population-based cohort study was conducted in southern China. Participants, identified using cluster random sampling, included residents of Yuexiu District, Guangzhou, China, aged 35 years or older who had undergone no previous eye surgery. METHODS Participants underwent noncycloplegic automated refraction and keratometry in December 2008 and December 2010; in a random 50% sample of the participants, anterior segment ocular coherence tomography measurement of lens thickness, as well as measurement of axial length and anterior chamber depth by partial coherence laser interferometry, were performed. MAIN OUTCOMES AND MEASURES Two-year change in spherical equivalent refraction (RE), lens thickness, axial length, and anterior chamber depth in the right eye. RESULTS A total of 745 individuals underwent biometric testing in both 2008 and 2010 (2008 mean [SD] age, 52.2 [11.5] years; 53.7% women). Mean RE showed a 2-year hyperopic shift from -0.44 (2.21) to -0.31 (2.26) diopters (D) (difference, +0.13; 95% CI, 0.11 to 0.16). A consistent 2-year hyperopic shift of 0.09 to 0.22 D was observed among participants aged 35 to 64 years when stratifying by decade, suggesting that a substantial change in RE with aging may occur during this 30-year period. Cross-sectionally, RE increased only in the cohort younger than 50 years (0.11 D/y; 95% CI, 0.06 to 0.16). In the cross-sectional data, axial length decreased at -0.06 mm/y (95% CI, -0.09 to -0.04), although the 2-year change in axial length was positive and thus could not explain the cross-sectional difference. These latter results suggest a cohort effect, with greater myopia developing among younger persons. CONCLUSIONS AND RELEVANCE This first Chinese population-based longitudinal study of RE provides evidence for both important longitudinal aging changes and cohort effects, most notably greater myopia prevalence among younger persons.

Significant Axial Elongation with Minimal Change in Refraction in 3- to 6-Year-Old Chinese Preschoolers: The Shenzhen Kindergarten Eye Study

PURPOSE To document the distribution of ocular biometry and to evaluate its associations with refraction in a group of Chinese preschoolers. DESIGN Population-based cross-sectional study. PARTICIPANTS A total of 1133 preschoolers 3 to 6 years of age from 8 representative kindergartens. METHODS Biometric measurements including axial length (AL), anterior chamber depth (ACD), and corneal radius of curvature (CR) were obtained from partial-coherence laser interferometry (IOL Master; Carl Zeiss Meditec, Oberkochen, Germany) before cycloplegia. Lens power (LP) and AL-to-CR ratio were calculated. Cycloplegic refraction (3 drops of 1% cyclopentolate) was measured using an autorefractor (KR8800; Topcon Corp., Tokyo, Japan), and spherical equivalent refraction (SER) was calculated. Biometric and refractive parameters were assessed as a function of age and gender. Multiple regression analysis was performed to explore the associations between refraction and ocular biometry. MAIN OUTCOME MEASURES Ocular biometric distributions and their relationships to refraction. RESULTS Among the 1127 children (99.5%) with successful cycloplegic refraction, mean SER was 1.37±0.63 diopters (D). Prevalence of myopia increased from 0% at 3 years of age to 3.7% (95% confidence interval, 1.0%-6.5%) at 6 years of age. Biometric parameters followed Gaussian distributions with means of 22.39±0.68 mm for AL, 7.79±0.25 mm for CR, and 24.61±1.42 D for calculated LP; and non-Gaussian distributions with means of 3.34±0.24 mm for ACD and 2.88±0.06 for AL-to-CR ratio. Axial length, ACD, and AL-to-CR ratio increased from 3 to 6 years of age, CR remained stable, whereas LP declined. Overall, SER declined slightly. For the SER variance, AL explained 18.6% and AL-to-CR ratio explained 39.8%, whereas AL, CR, and LP accounted for 80.0% after adjusting for age and gender. CONCLUSIONS Young Chinese children are predominantly mildly hyperopic, with a low prevalence of myopia by the age of 6 years. An increase of 1 mm in AL was associated with only 0.45 D of myopic change. Decreases in LP reduce the myopic shifts that normally would be associated with increases in AL, and thus play a key role in refractive development in this age group.