Cathy Williams

Prevalence and risk factors for common vision problems in children: data from the ALSPAC study

Objective: To estimate the distribution and predictors of some common visual problems (strabismus, amblyopia, hypermetropia) within a population-based cohort of children at the age of 7 years. Methods: Children participating in a birth cohort study were examined by orthoptists who carried out cover/uncover, alternate cover, visual acuity and non-cycloplegic refraction tests. Prospectively collected data on potential risk factors were available from the study. Results: Data were available for 7825 seven-year-old children. 2.3% (95% CI 2.0% to 2.7%) had manifest strabismus, 3.6% (95% CI 3.3% to 4.1%) had past/present amblyopia, and 4.8% (95% CI 4.4% to 5.3%) were hypermetropic. Children from the lowest occupational social class background were 1.82 (95% CI 1.03% to 3.23%) times more likely to be hypermetropic than children from the highest social class. Amblyopia (p = 0.089) and convergent strabismus (p = 0.066) also tended to increase as social class decreased. Conclusions: Although strabismus has decreased in the UK, it and amblyopia remain common problems. Children from less advantaged backgrounds were more at risk of hypermetropia and to a lesser extent of amblyopia and convergent strabismus. Children’s eye-care services may need to take account of this socio-economic gradient in prevalence to avoid inequity in access to care.

Amblyopia treatment outcomes after screening before or at age 3 years: follow up from randomised trial

Abstract Objective: To assess the effectiveness of early treatment for amblyopia in children. Design: Follow up of outcomes of treatment for amblyopia in a randomised controlled trial comparing intensive orthoptic screening at 8, 12, 18, 25, 31, and 37 months (intensive group) with orthoptic screening at 37 months only (control group). Setting: Avon, southwest England. Participants: 3490 children who were part of a birth cohort study. Main outcome measures: Prevalence of amblyopia and visual acuity of the worse seeing eye at 7.5 years of age. Results: Amblyopia at 7.5 years was less prevalent in the intensive group than in the control group (0.6% v 1.8%; P=0.02). Mean visual acuities in the worse seeing eye were better for children who had been treated for amblyopia in the intensive group than for similar children in the control group (0.15 v 0.26 LogMAR units; P<0.001). A higher proportion of the children who were treated for amblyopia had been seen in a hospital eye clinic before 3 years of age in the intensive group than in the control group (48% v 13%; P=0.0002). Conclusions: The intensive screening protocol was associated with better acuity in the amblyopic eye and a lower prevalence of amblyopia at 7.5 years of age, in comparison with screening at 37 months only. These data support the hypothesis that early treatment for amblyopia leads to a better outcome than later treatment and may act as a stimulus for research into feasible screening programmes. What is already known on this topic Observational studies have produced conflicting results about whether early treatment for amblyopia gives better results than later treatment A recent systematic review highlighted the lack of high quality data available and recommended the cessation of preschool vision screening programmes This has led to fierce debate and to confusion about the provision of vision screening services What this study adds Children treated for amblyopia are four times more likely to remain amblyopic if they were screened at 37 months only than if they were screened repeatedly between 8 and 37 months Children screened early can see an average of one line more with their amblyopic eye after treatment than children screened at 37 months Early treatment is more effective than later treatment for amblyopia, supporting the principle of preschool vision screening

Amblyopia treatment outcomes after preschool screening v school entry screening: observational data from a prospective cohort study

Background/aims: Preschool screening for amblyopia has controversially been abandoned in some localities within the United Kingdom, on the basis that there is no clear evidence of benefit to support its continuation. Data collected within a birth cohort study were used to examine visual outcomes at 7½ years in children who did or did not receive preschool vision screening. Methods: Monocular logMAR visual acuity with and without a pinhole was assessed by orthoptists. Contemporary records were used to identify children who had been offered and/or received preschool screening. Results: Of 6081 children, 24.9% had been offered preschool screening and 16.7% had attended. The prevalence of amblyopia was approximately 45% lower in the children who received preschool screening than in those who did not (1.1% v 2.0%, p = 0.05). The mean acuity in the worse seeing eyes after patching treatment was better for amblyopic children who received preschool screening than for those who did not; 0.14 v 0.20 logMAR (p <0.001). These effects did not persist in an intention to screen analysis. Conclusions: Preschool screening at 37 months was associated with an improved treatment outcome for individuals with amblyopia. However, the improvement was clinically small and disappeared when considering all children offered screening rather than only those who received it. Further research is needed into improving the effectiveness of vision screening for preschool children, while in the interim these data do not conflict with current recommendations for school entry screening by orthoptists.

Screening for amblyopia in preschool children: results of a population-based, randomised controlled trial. ALSPAC Study Team. Avon Longitudinal Study of Pregnancy and Childhood

Abstract INTRODUCTION The rationale for preschool vision screening programmes has recently been questioned. Evidence about the effects of early treatment is needed, but it is not known how early the target conditions can reliably be detected. In this study, an intensive programme comprising several different screening methods, used at different ages up to 37 months, was compared with the usual practice of visual surveillance and ad hoc referrals. METHODS Two groups were randomly selected from children in a population birth cohort study. The control group (n = 1461) received visual surveillance only. The intervention group (n = 2029) was offered in addition a programme of regular visual assessments by orthoptists testing visual acuity, ocular alignment, stereopsis and non-cycloplegic photorefraction. RESULTS The intervention group programme yielded more children with amblyopia (1.6% vs. 0.5%, p < 0.01), and was more specific (95% vs. 92%, p < 0.01), than the control programme. The individual components of the intervention programme were compared. The cover test and visual acuity tests were poorly sensitive until the children were 37 months, but were always >99% specific. Photorefraction was more sensitive than acuity testing at all ages below 37 months, with specificity >95% at 31 and 37 months. CONCLUSIONS Photorefraction would have detected more children less than 37 months of age with straight-eyed amblyopia than did visual acuity testing, but with more false positives. At 37 months, photore-fraction plus a cover test would have been comparable in effectiveness to visual acuity testing plus a cover test.

Random dot stereoacuity of preschool children

Purpose: Commercially available book-format random dot stereopsis tests for children are quick and simple to use, but provide accurate measurement of stereoacuity only in children age 5 years or older. Alternative methods for preschool children provide only pass/fail information or require lengthy laboratory-based protocols. To address the need for a quick and accurate measure of random dot stereoacuity in the preschool age range, we developed a new book-format random dot stereoacuity test. Methods and results: A total of 25 potential shapes for the new test were evaluated in a group of 43 healthy full-term children aged 3 years±2 months. Eleven shapes that were identified successfully by more than 95% of the 3-year-olds were selected to be incorporated into the preschool stereotest. The preschool random dot stereotest books were administered to more than 1000 normal children and pediatric patients in multiple settings: a research laboratory (Retina Foundation SW), a population screening project (University of Bristol, UK), eye clinics (Childrens Medical Center, Dallas, Tex), and a day care center (Federal University, Sao Paulo, Brazil). Randot, Lang 1, Frisby, or Titmus stereoacuity tests also were administered. Orthoptic or ophthalmic examinations were obtained for all children as a gold standard. Outcome measures were success rate and concordance with the clinical examination. Sensitivity, specificity, and accuracy exceeded 0.90 both in clinical and screening settings. Conclusions: The preschool random dot books had a higher success rate than other tests in the preschool age range and provided accurate measurement of stereoacuity in the 3- to 5-year-old age range.

Impact of Size at Birth on the Microvasculature: The Avon Longitudinal Study of Parents and Children

BACKGROUND. The impact of early life factors on the microvasculature is relatively unknown. OBJECTIVES. We hypothesized that small birth size may be associated with structural variations in the retinal vasculature in children. METHODS. The Avon Longitudinal Study of Parents and Children followed a cohort of children born in 1991–1992 from birth. The current study included the first 263 children who were systematically screened in the year-12 follow-up. Complete data were available for 166 children with a gestation of ≥37 weeks. Retinal circulatory measures were evaluated, including retinal microvascular tortuosity and bifurcation optimality deviance, an indicator of abnormal endothelial function. RESULTS. Optimality deviance and retinal tortuosity were higher among those with lower birth weight. Linear regression modeling was used to assess the association of retinal microvascular measures with birth weight. The standardized β coefficient between optimality deviance and birth weight was −.182 adjusted for gender and age in weeks; additional adjustment for systolic blood pressure and heart rate had little impact on the β coefficient. A similar association was observed for retinal tortuosity. CONCLUSION. The findings of this study suggest that early life factors may have an important impact on retinal vascular structure, possibly through an adverse effect on endothelial function.

A comparison of measures of reading and intelligence as risk factors for the development of myopia in a UK cohort of children

Aim: Evidence suggests that reading may be an important risk factor for myopia, but recent reports find that performance in non-verbal intelligence tests may be more important or that near-work is not associated with myopia. Methods: Non-cycloplegic autorefraction data were available at the ages of 7 and 10 years from a birth cohort study. Children whose right eye spherical equivalent autorefraction was ⩽−1.50 D were categorised as “likely to be myopic.” The authors tested associations between school-based Standardised Assesment Tests (SATS) for reading and mathematics, maternal report of child liking reading, the Wescher Objective Reading Dimension (WORD) test results, verbal and non-verbal IQ, and the child being in the “likely to be myopic” group. Results: 6871 children (59.7% of remaining cohort) had refractive and risk factor data at 7, of whom 1.5% were in the “likely to be myopic” group. Predictors (odds ratios, OR: 95% CI) of concurrent (at 7) risk for myopia were good performance in the SATS reading (2.60:1.61, 4.19; p<0.001), SATS maths (1.90: 1.19, 3.05; p = 0.008), the WORD (2.72:1.60, 4.64; p = 0.001) and verbal IQ tests (1.99, 1.13, 3.52; p = 0.055) after adjustment for the number of myopic parents (p = 0.014) and ethnicity (p = 0.129). However, the strongest predictor of incident myopia developing between 7 and 10 years was the parental report of whether the child liked reading: (4.05:1.27, 12.89; p = 0.031), adjusted for parental myopia (p = 0.033) and ethnicity (p = 0.008). Conclusions: Factors associated with reading may play a part in myopia development. Further comparisons of different measures of reading-related activity or verbal ability may help clarify which of the related behavioural characteristics are causally related to myopia prevalence.

Does Vitamin D Mediate the Protective Effects of Time Outdoors On Myopia? Findings From a Prospective Birth Cohort

PURPOSE More time outdoors is associated with a lesser risk of myopia, but the underlying mechanism is unclear. We tested the hypothesis that 25-hydroxyvitamin D (vitamin D) mediates the protective effects of time outdoors against myopia. METHODS We analyzed data for children participating in the Avon Longitudinal Study of Parents and Children (ALSPAC) population-based birth cohort: noncycloplegic autorefraction at age 7 to 15 years; maternal report of time outdoors at age 8 years and serum vitamin D2 and D3 at age 10 years. A survival analysis hazard ratio (HR) for incident myopia was calculated for children spending a high- versus low-time outdoors, before and after controlling for vitamin D level (N = 3677). RESULTS Total vitamin D and D3, but not D2, levels were higher in children who spent more time outdoors (mean [95% confidence interval (CI)] vitamin D in nmol/L: Total, 60.0 [59.4-60.6] vs. 56.9 [55.0-58.8], P = 0.001; D3, 55.4 [54.9-56.0] vs. 53.0 [51.3-54.9], P = 0.014; D2, 5.7 [5.5-5.8] vs. 5.4 [5.1-5.8], P = 0.23). In models including both time outdoors and sunlight-exposure-related vitamin D, there was no independent association between vitamin D and incident myopia (Total, HR = 0.83 [0.66-1.04], P = 0.11; D3, HR = 0.89 [0.72-1.10], P = 0.30), while time outdoors retained the same strong negative association with incident myopia as in unadjusted models (HR = 0.69 [0.55-0.86], P = 0.001). CONCLUSIONS Total vitamin D and D3 were biomarkers for time spent outdoors, however there was no evidence they were independently associated with future myopia.

Are there inequities in the utilisation of childhood eye-care services in relation to socio-economic status? Evidence from the ALSPAC cohort.

Background: Equity of access to eye care in childhood remains poorly researched, and most studies report data on utilisation without any objective measure of clinical need. Participants/method: 8271 participants from the Avon Longitudinal Study of Parents and Children (ALSPAC), a longitudinal birth cohort, were seen at age 7, when they underwent a comprehensive eye examination and details of family history of eye conditions, vision problems and contact with eye-care services were obtained. Results: 2931 (35.4%) children had been in contact with an eye-care specialist, and 1452 (17.6%) had received vision screening. Compared with social class I, the prevalence of eye conditions was higher in the lower groups (social class IIIM, IV, V) (OR 1.69, 95% CI 1.15 to 2.46). However, children from lower socio-economic status groups were less likely to see an eye-care specialist (OR 0.83, 95% CI 0.70 to 1.00) or to use screening services (OR 0.65, 95% CI 0.43 to 0.98). Discussion/conclusion: The differences in the trends between socio-economic groups in eye conditions and utilisation of services suggest inequitable access to services. These data highlight the limitations of community-based preschool vision screening, which fails to abolish this inequity. It is important that future research explores the reasons behind these patterns. Compulsory school-entry vision screening, as recommended by the National Screening Committee and the Hall Report may redress this differential uptake of services.

Screening and surveillance for ophthalmic disorders and visual deficits in children in the United Kingdom

Children are a priority in “Vision 2020”, the World Health Organizations recently launched global initiative for the prevention of avoidable visual impairment by the year 2020.1Successful implementation in the United Kingdom will depend to a greater extent on improvements in secondary and tertiary preventive strategies, to treat and rehabilitate affected children, than on the currently limited primary preventive approaches to the major paediatric eye diseases. Early detection is important to the successful management of children with ophthalmic disorders. In recognition of this, over the past few decades in the UK diverse activities have been implemented to promote early detection of specific ophthalmic conditions in children as well as to monitor their visual development. These comprise physical examinations by various health professionals and effectively form a continuum of screening and surveillance whose purpose and value is best considered in terms of sequential gain. Although now well established, these practices have arisen haphazardly and few have been subject to rigorous evaluation of their benefits. Indeed the scientific basis of some has been seriously questioned.2 In the UK they are undertaken within the broader context of a national programme of child health surveillance.3 Changes in this, such as the increased emphasis on health promotion,3 increasing responsibilities of general practitioners,4 and reconsideration of the roles of health visitors and school nurses,5 consequently have implications for ophthalmological screening and surveillance. The Childrens Sub-Group of the National Screening Committee (NSC) of the UK has recently reviewed screening for ophthalmic disorders and visual deficits in children for the first time. The NSC categorised existing activities into five separate screening programmes for retinopathy of prematurity (ROP) in preterm/low birthweight infants; congenital cataract and other ocular anomalies in newborn and young infants; amblyopia and impaired vision in preschool age children; impaired vision, …