Richard A Harrad

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.

Psychological causes of non-compliance with electronically monitored occlusion therapy for amblyopia

Aim: To analyse psychological causes for low compliance with occlusion therapy for amblyopia. Method: In a randomised trial, the effect of an educational programme on electronically measured compliance had been assessed. 149 families who participated in this trial completed a questionnaire based on the Protection Motivation Theory after 8 months of treatment. Families with compliance less than 20% of prescribed occlusion hours were interviewed to better understand their cause for non-compliance. Results: Poor compliance was most strongly associated with a high degree of distress (p<0.001), followed by low perception of vulnerability (p = 0.014), increased stigma (p = 0.017) and logistical problems with treatment (p = 0.044). Of 44 families with electronically measured compliance less than 20%, 28 could be interviewed. The interviews confirmed that lack of knowledge, distress and logistical problems resulted in non-compliance. Conclusion: Poor parental knowledge, distress and difficulties implementing treatment seemed to be associated with non-compliance. For the same domains, the scores were more favourable for families who had received the educational programme than for those who had not.

Superior rectus-levator synkinesis: a previously unrecognized cause of failure of ptosis surgery.

PURPOSE To describe a previously unreported type of ptosis associated with abnormal synkinesis between the superior rectus muscle and the levator palpebrae superioris. DESIGN Retrospective noncomparative case series. PARTICIPANTS Seven cases with congenital or longstanding unilateral ptosis presenting to a regional, tertiary referral, oculoplastic service. Six of these cases were seen within a period of 2 years. METHODS Detailed observations of eyelid, ocular, and pupil movements of both eyes were performed before the planning of ptosis surgery anterior levator resection. MAIN OUTCOME MEASURES Magnitude of ptosis and its variation with the position of gaze. RESULTS Ptosis present in the primary position disappeared or markedly reduced with upgaze so that measurements of levator function were apparently normal. Close examination of the relative movement of the eyelids revealed evidence of superior rectus to levator synkinesis occurring during upgaze. In three cases the synkinesis was recognized only after failed ptosis surgery. Once recognized, two of these cases underwent further surgery with an excellent result. Three other patients all had successful surgery. CONCLUSIONS Superior rectus to levator synkinesis may be easily overlooked if eyelid elevation in upgaze is ascribed to normal levator function rather than a synkinetic movement. We draw attention to the importance of identifying this relatively common condition to plan appropriate ptosis surgery. The lack of levator muscle tone in the primary position of gaze means that an augmented resection of the levator muscle should be performed.

Future of preschool vision screening. Conclusions for or against services are invalid without appropriate research evidence.

Editor—Rahi and Dezateux highlighted the current dilemma about preschool vision screening.1 A systematic review has detailed the lack of published evidence on whether the target conditions (amblyopia, non-obvious squint, and refractive error) are disabling and whether detection at preschool age results in better treatment outcomes than detection at school age.2 The review concludes that published hard evidence is lacking on preschool vision screening but then recommends that providers consider discontinuing current programmes. Without appropriate high quality research evidence, conclusions either in favour of or against these services are equally invalid. Ongoing research into this subject has occurred within a multidisciplinary birth cohort study of 14 000 children born in Avon between April 1991 and December 1992.3 A randomised controlled trial of screening methods for ocular defects in children under 3 years of age has collected data on whether any disability in social, physical, or cognitive function is associated with the target defects at the age of 4½ years.4,5 The birth cohort study aims to complete a detailed, multidisciplinary assessment of all 14 000 children at the age of 7 years, half of whom will have had preschool vision screening while the other half will have not. This will provide high quality data on whether the target defects are associated with suboptimal performance in other areas of life at this age and, if so, whether preschool screening resulted in a better outcome (visual, educational, or developmental) than screening at school age. As stated in the review,2 these data are necessary to decide whether to support preschool vision screening. The review’s recommendations lack objectivity and suggest that the authors believe that preschool vision screening is not worth while, despite the lack of adequate data on which to base such a conclusion. The removal of existing services on the basis of this review would be unfortunate if subsequent research showed beyond doubt that preschool vision screening was beneficial. Given the substantial indirect (animal) and retrospective (clinical) evidence already suggesting that the target conditions are both disabling and better treated as early as possible, policymakers might be better advised not to act on the review’s recommendations until the results of the birth cohort study and other relevant work become available. This would allow time to complete the collection and presentation of the much needed data and would avoid the possibility of a beneficial intervention being inappropriately withdrawn.

Methodology for a randomised controlled trial of preschool vision screening. A new approach with the 'ALSPAC' project

We present the methodology of a population-based Randomised Controlled Trial, comparing an intensive programme of primary preschool vision screening by orthoptists with the usual non-specialist screening. The aims of the trial are to compare the effectiveness and costs of intensive orthoptic screening with non-specialist measures. The orthoptic screening programme will be evaluated both as a composite package and in terms of the screening value of the individual tests at specific ages. This trial is nested within a large population-based longitudinal study. Additional demographic and developmental data on the children in the trial are therefore available. The results of the trial will be used to help clarify which methods of preschool ophthalmic population screening are best in terms of disease detection and cost efficiency.

Amblyopia: Contemporary Clinical Issues

Research into the clinical management of amblyopia has, most recently, focussed on the effectiveness of amblyopia treatment. Given the mounting evidence that the condition is treatable, an important priority is the detection of individuals with the condition. Here, we review critically the means by which this can be achieved. We conclude that intensive early screening can produce improved outcomes but that the effectiveness of real-life screening programmes is very dependent on the coverage they obtain. An almost entirely neglected subfield of amblyopia treatment research is the identification of reasons why parents and children often fail to comply with occlusion therapy. Here, we examine a psychological approach to this problem and find it to be informative in predicting compliance. Lastly, we consider the disability arising from strabismus, again from a psychological perspective, and find that on a range of psychosocial well-being indicators, strabismus surgery results in significant gains.

The efficacy of occlusion for strabismic amblyopia. Can an optimal duration be identified

Patching carried out during the sensitive period is thought by clinicians to be an effective treatment for amblyopia.1 2Success rates of patching vary but one study has reported success rates of 90% of patients improving to 6/12 or better within 3 months.3 Parents not uncommonly report difficulty in persuading their children to wear a patch.4 Inpatient treatment by supporting the parents and encouraging the children frequently achieves success. A recent systematic review5 was unable to find any randomised controlled trials of treatment of amblyopia and concluded that there was no evidence …

Interocular asymmetries in axial length and refractive error in 4 cohorts

Retinal detachment occurs more commonly in right eyes (even after traumatic detachments are excluded). Suggested explanations have included differing blood supply routes or asymmetric effects of reading saccades. Myopia is the most important risk factor for retinal detachment. This study explored the hypothesis that right eyes are more myopic than left eyes using 4 large cohorts (34 060 eyes in total). We also explored whether asymmetry may relate to eye dominance. For subsets of 2 cohorts, eye dominance data were available. Previous studies exploring interocular refractive asymmetry have shown conflicting or nonsignificant results. However, such studies were frequently in refractive surgery cohorts with possible ascertainment bias for high ametropia. Our cohorts, in contrast, were broadly representative of the UK population. Our first cohort comprised 8195 consecutive cataract patients undergoing surgery in a single department over a 6.5-year period. Axial lengths were routinely measured preoperatively by partial coherence interferometry (IOLMaster, Carl Zeiss Meditec AG, Jena, Germany), and entered into an electronic medical record. Second, we analyzed data from the Avon Longitudinal Study of Parents and Children (ALSPAC), which recruited pregnant women resident in Avon, UK, with expected delivery dates between April 1, 1991, and December 31, 1992. Noncycloplegic autorefractions (Canon R50, Canon Europa, Amstelveen, the Netherlands) were obtained from the children at 15 years, together with axial lengths (IOLMaster), with data available for 2625 subjects. Most subjects also had eye preference tested, recording the preferred eye used to look through a small keyhole-like aperture. (Study details are available at http:// www.bris.ac.uk/alspac/researchers/data-access/data-dictionary/; accessed October 27, 2014.) Our third cohort comprised healthy twin volunteers (TwinsUK Cohort). Data were collected from 5755 twins who participated in an eye study in which refraction was measured using an autorefractor (Humphrey-670, Humphrey Instruments, San Leandro, CA, or ARM-10, Takagi Seiko, Japan). Spherical equivalent refractions were compared between right and left eyes (paired t test). In addition, relatedness of twins was taken into account by repeatedly performing the test, randomly selecting 1 member from each twin pair in each permutation (10 000 permutations; P values in parentheses in Table 1). For an unselected subset (1185 twins), eye dominance was recorded. Subjects looked through a hole in a card using 1 eye while closing the other eye (the former taken as the dominant eye). Our fourth cohort was the 1958 British Birth Cohort, which initially comprised 17 000 individuals born during a single week in March 1958. During 2002 and 2003, approximately 25% of the 9377 individuals still in the study were selected randomly and underwent noncycloplegic autorefraction (Retinomax 2, Nikon, Tokyo, Japan). The study adhered to the tenets of the Declaration of Helsinki, and relevant local ethical committee approval was obtained. 1 summarizes the results of the righteleft comparison. teral cataract patients, right eyes were on average longer than left eyes (P 1⁄4 4.7 10 ). In unilateral patients, right eyes were also longer (P 1⁄4 0.040). The ALSPAC participants similarly showed greater mean length in right eyes (P < 0.001). Table 1 also shows refractive data from the ALSPAC, TwinsUK, and 1958 British birth cohorts: Right eyes were found to be on average more myopic in all 3 cohorts (P < 0.001, 0.006, and 0.057, respectively). Despite differing ages and absolute refractions, the mean interocular difference was 0.04 diopters (D) in each case. Comparisons between right and left, and between dominant and nondominant, eyes are summarized in Table 2 (available at www.aaojournal.org). For TwinsUK participants, dominant eyes were 0.06 D on average more myopic than nondominant eyes (this also held in both right and left eye dominant subgroups). Interestingly, for the smaller subset of left eye dominant individuals, the righteleft laterality was reversed, with left (dominant) eyes seeming on average to be more myopic by 0.06 D, although the difference was not significant. The ALSPAC cohort showed similar findings: Dominant eyes were more myopic by 0.07 D (P < 0.001). In right eye dominant subjects, the right eye was more myopic by 0.09 D (P < 0.001); in left eye dominant subjects, the left eye was more myopic by 0.05 D (P 1⁄4 0.083). Dominant eyes were longer by 0.04 mm on average (P < 0.001). In right eye dominant subjects, the difference remained significant and in the same direction (right eyes 0.05 mm longer; P < 0.001). However, for left eye dominant subjects, the difference was smaller (0.01 mm) and not significant (P 1⁄4 0.507), although it was in the direction of left eyes being longer. Taken together, our results indicate that, on average, measurements in right eyes are slightly longer and more myopic, which could contribute to asymmetry in retinal detachments. It also seems that the asymmetry may be related more to eye dominance than righteleft laterality. Where eye dominance data were available, dominant eyes did seem to be longer and more myopic. In left eye dominant individuals, the righteleft asymmetry seemed to be reversed, with a trend for left eyes to be more myopic, and possibly longer, although the difference was not significant. The lack of significance could be due to smaller sample size, or because righteleft asymmetry is less consistent in left dominant subjects. Measurements are usually made on right eyes first (as in our cohorts), raising the possibility of systematic measurement error. However, agreements between axial length and refractive measurements (obtained with different types of equipment), together with the apparent reversal or loss of asymmetry in left eye dominant subjects (it would be difficult to explain why a systematic measurement error should reverse in left eye dominant subjects), suggest the difference is not simply measurement error. Another potential explanation could be interocular differences in accommodation in autorefraction measurements (noncycloplegic in our study): it is possible that dominant eyes might show more accommodation. Axial length measurements, however, should be less affected, and for the elderly cataract cohort little accommodative facility is expected. Future studies could explore what might underlie this small asymmetry. Eye growth is tightly regulated, driven largely by