Alison Bruce

Bilateral Changes in Foveal Structure in Individuals with Amblyopia

PURPOSE To examine foveal structure in amblyopia using spectral-domain optical coherence tomography (SD-OCT). DESIGN Prospective, cross-sectional study. PARTICIPANTS AND CONTROLS Two subject groups were recruited to the study: 85 amblyopes (34 adults, 51 children) and 110 visually normal controls (44 adults, 66 children). METHODS A detailed eye examination, including an SD-OCT scan, was performed in all participants. A total of 390 eyes of 195 subjects were imaged using a 3-dimensional (3D) macula scan covering a nominal 6 × 6-mm area with a resolution of 256 × 256 (65,536 axial scans). Data from the B-scans bisecting the fovea both horizontally and vertically were fitted with a mathematical model of the fovea to determine a range of foveal parameters. MAIN OUTCOME MEASURES Foveal thickness, foveal pit depth, and foveal pit slope. RESULTS Bilateral differences between the eyes of amblyopes compared with visually normal controls were found. The difference between foveal structure in amblyopic participants relative to structure in subjects with normal vision persisted even when variables such as age, ethnicity, axial length, and sex were taken into account. Amblyopes showed increased foveal thickness (+8.31 μm; P = 0.006) and a reduction in pit depth in the horizontal meridian (-10.06 μm; P = 0.005) but not in the vertical meridian (P = 0.082) when compared with subjects with normal vision. Foveal pit slopes were found to be approximately 1 degree flatter in the nasal (P = 0.033) and temporal (P = 0.014) meridians in amblyopes, but differences between amblyopes and controls in the superior (P = 0.061) and inferior (P = 0.087) meridians did not reach statistical significance. No statistically significant interocular differences were found in the foveal structure between amblyopic and fellow eyes. CONCLUSIONS Differences were found in the foveal structure in both eyes of amblyopes compared with subjects with normal vision. These differences consisted of increased foveal thickness, reduced pit depth when measured along the horizontal meridian, and flattening of the nasal and temporal sides of the foveal pit.

Repeatability and reproducibility of macular thickness measurements using fourier domain optical coherence tomography.

Aim: To evaluate repeatability and reproducibility of macular thickness measurements in visually normal eyes using the Topcon 3D OCT-1000. Methods: Phase 1 investigated scan repeatability, the effect of age and pupil dilation. Two groups (6 younger and 6 older participants) had one eye scanned 5 times pre and post- dilation by 1 operator. Phase 2 investigated between-operator, within and between-visit reproducibility. 10 participants had 1 un-dilated eye scanned 3 times on 2 separate visits by 2 operators. Results: Phase 1: No significant difference existed between repeat scans (p=0.75) and no significant difference was found pre- and post-dilation (p=0.54). In the younger group variation was low (95% limits ± 3.62µm) and comparable across all retinal regions. The older group demonstrated greater variation (95% limits ± 7.6µm). Phase 2: For a given retinal location, 95% confidence limits for within-operator, within-visit reproducibility was 5.16µm. This value increased to 5.56µm for the same operator over two visits and to 6.18µm for two operators over two visits. Conclusion: A high level repeatability, close to 6µm, of macular thickness measurement is possible using the 3D OCT- 1000. Measured differences in macular thickness between successive visits that exceed 6µm in pre-presbyopic individuals are therefore likely to reflect actual structural change. OCT measures are more variable in older individuals and it is advisable to take a series of scans so that outliers can be more easily identified.

Prevalence and Risk Factors of Strabismus in a UK Multi-ethnic Birth Cohort

ABSTRACT Purpose: To determine the prevalence, types and early-life risk factors associated with strabismus in a multi-ethnic birth cohort of children aged 4-5 years in the first year of school. Methods: Data were collected prospectively over a 3-year period (2012-2015) from children participating in the vision screening program provided by orthoptists and carried out in schools located in the city of Bradford, UK. Prevalence of strabismus was determined for 17,018 children aged 4 to 5 years. Data linkage was undertaken for 4563 children participating in the Born in Bradford birth cohort study and the vision screening program. 4067 children had complete data and were included in the multivariable regression analyses to determine associated factors. Results: 401/17018 (2.4%) children were found to have either a constant or an intermittent strabismus; 179/401 (45%) had an esotropic deviation, 214 (53%) an exotropic deviation, and 8 (2%) had a vertical deviation. No significant difference in the overall prevalence of strabismus was found between the white British, Pakistani, or children of other ethnic origin (P=0.41). Multivariable analysis showed that children of white British ethnicity have twice the odds of having esotropia (OR 2.4, 95% CI: 1.1, 5.3). The odds of having esotropia were highest in children with a hyperopic mean spherical equivalent (OR 2.0, 95% CI: 1.7, 2.6). There was some evidence of an interaction between ethnicity and mean spherical equivalent in children with esotropia (P=0.058). Conclusions: Prevalence of strabismus is consistent with other population-based studies in this cohort of children aged 4-5 years. Prevalence of esotropia (constant or intermittent) is greater in the white British population, odds of esotropia increased with increasing hyperopic refractive error in both white British and Pakistani children. Exotropia (constant or intermittent) was not found to be associated with refractive error, ethnicity, or other early life factors.

Assessing visual function in children with complex disabilities: the Bradford visual function box

Background Assessment of children with complex and severe learning disabilities is challenging and the children may not respond to the monochrome stimuli of traditional tests. The International Association of Scientific Studies on Intellectual Disability recommends that visual function assessment in poorly or non-cooperative children should be undertaken in an objective manner. We have developed a functional visual assessment tool to assess vision in children with complex and multiple disabilities. Methods The Bradford visual function box (BVFB) comprises a selection of items (small toys) of different size and colour, which are presented to the child and the response observed. The aim of this study is to establish its intertester validity in children with severe learning disability. The visual function of 22 children with severe learning disability was assessed using the BVFB. The children were assessed by experienced practitioners on two separate occasions. The assessors were unaware of each others findings. Results In 15/22 of the children, no difference was found in the results of the two assessors. The test was shown to have a good intertester agreement, weighted κ=0.768. Conclusions The results of this clinical study show that the BVFB is a reliable tool for assessing the visual function in children with severe learning disability in whom other tests fail to elicit a response. The need for a tool which is quick to administer and portable has previously been highlighted. The BVFB offers an option for children for whom other formal tests are unsuccessful in eliciting a response.

The effect of adherence to spectacle wear on early developing literacy: a longitudinal study based in a large multiethnic city, Bradford, UK

Objectives To determine the impact of adherence to spectacle wear on visual acuity (VA) and developing literacy following vision screening at age 4–5 years. Design Longitudinal study nested within the Born in Bradford birth cohort. Setting and participants Observation of 944 children: 432 had failed vision screening and were referred (treatment group) and 512 randomly selected (comparison group) who had passed (<0.20 logarithm of the minimum angle of resolution (logMAR) in both eyes). Spectacle wear was observed in school for 2 years following screening and classified as adherent (wearing spectacles at each assessment) or non-adherent. Main outcome measures Annual measures of VA using a crowded logMAR test. Literacy was measured by Woodcock Reading Mastery Tests-Revised subtest: letter identification. Results The VA of all children improved with increasing age, −0.009 log units per month (95% CI −0.011 to −0.007) (worse eye). The VA of the adherent group improved significantly more than the comparison group, by an additional −0.008 log units per month (95% CI −0.009 to −0.007) (worse eye) and −0.004 log units per month (95% CI −0.005 to −0.003) in the better eye. Literacy was associated with the VA, letter identification (ID) reduced by −0.9 (95% CI −1.15 to −0.64) for every one line (0.10 logMAR) fall in VA (better eye). This association remained after adjustment for socioeconomic and demographic factors (−0.33, 95% CI −0.54 to −0.12). The adherent group consistently demonstrated higher letter-ID scores compared with the non-adherent group, with the greatest effect size (0.11) in year 3. Conclusions Early literacy is associated with the level of VA; children who adhere to spectacle wear improve their VA and also have the potential to improve literacy. Our results suggest failure to adhere to spectacle wear has implications for the child’s vision and education.

Visual impairment and the risk of mortality: addressing complex associations.

The worldwide rise in the ageing population has led to increasing levels of visual impairment.1 Visual impairment impacts on the individual with the potential to lead to loss of independence, falls, depression and reduced functional ability, and at a population level, there is an impact on the delivery of public health resources.1–3 Not only does visual impairment impact on morbidity, its impact on the risk of mortality has also been reported; it is important therefore to understand its effect at an individual and population level. In this issue of Journal of Epidemiology and Community Health , Zhang et al 4 report the results of a meta-analysis investigating the association between visual impairment and mortality. Several population-based studies have investigated the association between visual impairment and mortality, however not all studies have demonstrated comparable findings. The Beaver Dam Eye Study reported increased mortality associated with visual impairment and dense cataract over a 5-year period even after controlling for age and gender.5 The Blue Mountains Eye Study also reported an …

Prevalence of, and risk factors for, presenting visual impairment: findings from a vision screening programme based on UK NSC guidance in a multi-ethnic population

PurposeTo determine presenting visual acuity levels and explore the factors associated with failing vision screening in a multi-ethnic population of UK children aged 4–5 years.MethodsVisual acuity (VA) using the logMAR Crowded Test was measured in 16,541 children in a population-based vision screening programme. Referral for cycloplegic examination was based on national recommendations (>0.20logMAR in one or both eyes). Presenting visual impairment (PVI) was defined as VA >0.3logMAR in the better eye. Multivariable logistic regression was used to assess the association of ethnicity, maternal, and early-life factors with failing vision screening and PVI in participants of the Born in Bradford birth cohort.ResultsIn total, 2467/16,541 (15%) failed vision screening, 732 (4.4%) had PVI. Children of Pakistani (OR: 2.49; 95% CI: 1.74–3.60) and other ethnicities (OR: 2.00; 95% CI: 1.28–3.12) showed increased odds of PVI compared to white children. Children born to older mothers (OR: 1.63; 95% CI: 1.19–2.24) and of low birth weight (OR: 1.52; 95% CI: 1.00–2.34) also showed increased odds. Follow-up results were available for 1068 (43.3%) children, 993 (93%) were true positives; 932 (94%) of these had significant refractive error. Astigmatism (>1DC) (44%) was more common in children of Pakistani ethnicity and hypermetropia (>3.0DS) (27%) in white children (Fisher’s exact, p < 0.001).ConclusionsA high prevalence of PVI is reported. Failing vision screening and PVI were highly associated with ethnicity. The positive predictive value of the vision screening programme was good, with only 7% of children followed up confirmed as false positives.

Qualitative study investigating the perceptions of parents of children who failed vision screening at the age of 4-5 years

Objective To explore in depth parents’ experiences and understanding of their children’s eye care in order to better comprehend why there is relatively low uptake of services and variable adherence to treatment. Design Semistructured interviews, informed by the Health Belief framework, were conducted with parents of children who had failed vision screening at age 4–5 years. Four were parents of children who never attended follow-up, 11 had children who attended but did not adhere to spectacle wear and 5 parents of children who had attended and adhered. Interviews were recorded and transcribed verbatim; thematic analysis based on the constant comparative method was undertaken. Results Parents’ beliefs led to uncertainty about the benefit of treatment, with parents testing their children to confirm the presence of a vision deficit and seeking advice from other family and community members. The stigma of spectacle wear explained the resistance of some to their child’s treatment with the maintenance of ‘normality’ often more important than clinical advice. The combination of parents’ own health beliefs, stigma and the practicalities of attending appointments together influenced parental decisions. Attendance following vision screening and the decision to adhere to spectacle wear were primarily based on the perceived severity of the visual reduction with the perceived benefit of spectacle wear outweighing any negative consequences. Conclusions Healthcare professionals require a greater understanding of parents’ decision-making processes in order to provide personalised information. Knowledge of the cues to attendance and adherence provides policy makers a framework with which to review the barriers, develop strategies and redesign children’s eye care pathways.

OP90 The impact of vision on early developing literacy

Background The United Kingdom National Screening Committee recommends that vision screening should be provided to all children at age 4–5 years, the evidence supporting this recommendation is weak and the effect of reduced vision on educational attainment in children has not yet been established. At a time of change and uncertainty in the commissioning of vision screening services it is important to understand both the level of vision in the population and the impact this is likely to have on future health and social outcomes. The aim of this study is to determine the prevalence of poor vision in a multi-ethnic population and explore the impact of reduced vision on developing literacy skills in young children as they commence primary school. Methods The study was nested within Born in Bradford (BiB) a multi-ethnic birth cohort of children (50% of South Asian origin). Measures from the universal school vision screening programme were prospectively recorded and linked to the epidemiological data and literacy measures collected from the BiB children over two consecutive school years (2012–2014). A standardised literacy measure; the Woodcock Reading Mastery Tests-Revised: Letter Identification (Letter ID) was used to measure the child’s ability to identify single letters, an essential precursor to reading. The effect of presenting visual acuity (PVA) (best acuity right or left eye, with glasses if worn) on literacy (letter ID) was assessed using multi-level regression models with individuals nested within schools and adjusting for demographic and socioeconomic factors. Results Prevalence of poor vision (worse than 0.3 logMAR) was high compared to other published studies. Unadjusted analysis (n = 2025) showed letter ID score was associated with the level of vision, with the score reducing by 2.42 points for every 1 line (0.10 logMAR) reduction in vision (95% CI: −2.98 to −1.87). When adjusted to account for demographic and socioeconomic factors the impact of vision remains significant after all factors are accounted for with letter ID score reducing by 1.65 (95% CI: −2.17 to −1.13) for every 1 line reduction in vision. Discussion Data linkage has enabled this study to reliably demonstrate that poor vision in young children is associated with reduced early developing literacy; even after other relevant factors are taken into account. This study strengthens the argument for a national vision screening programme. Further research is required to determine the extent to which children with poor vision access treatment and the impact of such treatment not only on levels of vision but also on their educational attainment.