Aims: To determine the prevalence of ophthalmic impairments in very preterm compared with term infants, the relation between impairments and cerebral ultrasound appearances and retinopathy, and the correlation with visual perception and motor and cognitive measures. Subjects: 279 children at 7 years of age born before 32 weeks gestation within Liverpool during 1991-92 and attending mainstream schools, and 210 term controls. Methods: Visual acuity was assessed by Snellen chart, and strabismus by the cover test. Stereopsis was determined using the TNO random dot test, and contrast sensitivity using the Cambridge low contrast gratings. Visual and motor abilities were assessed using the Developmental test of motor integration (VMI) and the Movement ABC. Intelligence was measured with the Wechsler intelligence scale for children UK. Perinatal cranial ultrasound and retinopathy data were extracted from clinical records. Results: Children born preterm were significantly more likely to wear glasses, to have poor visual acuity, reduced stereopsis, and strabismus than term controls, but they showed no significant decrease in contrast sensitivity. Ophthalmic impairments were significantly related to poorer scores on the VMI, Movement ABC, and Wechsler IQ tests, but were not significantly related to neonatal cranial ultrasound appearances. Stage 3 retinopathy was related to poorer subsequent acuity. Conclusions: Children born very preterm and without major neurodevelopmental sequelae have an increased prevalence of ophthalmic impairments at primary school age which are associated with visual perceptional, motor, and cognitive defects. The cause may be a generalised abnormality of cortical development rather than perinatally acquired focal lesions of the brain.

Background/aims: It is well documented that non-concordance with occlusion therapy is both substantial and a major factor leading to treatment failure. Parental understanding in previous work has been found to be poor in key areas such as the critical period and effect of age on prognosis. Research in other areas of medicine has shown that the level of understanding can have a direct effect on the level of concordance. The aims of this study were to assess the ability of educational material in the form of a leaflet, to improve parental understanding of amblyopia and occlusion, and subsequently increase concordance. Methods: Parents of children aged between 1 and 7 years receiving a minimum of 1 hour of occlusion for amblyopia were recruited. A randomised controlled trial was undertaken where, on inclusion, the patients were randomised into a leaflet group, whose parents were issued with written educational material, and a control group whose parents did not receive the written information. Patients were paired and matched for age (<2 years difference) and amount of prescribed occlusion (no more than 1 hour difference). Concordance was monitored by a parental diary and knowledge and parental reasons for non-concordance were assessed by a questionnaire. Concordance was analysed by means of a concordance index and by calculating the proportion of non-concordant parents by setting a threshold of concordance at 80%. Results: Parental knowledge was significantly greater in the leaflet group (88% had complete knowledge) compared to the control group (49% had complete knowledge) (p <0.001). There were also differences between the groups in the area of the treatment regimen, with errors only occurring in the control group (three patients occluded the incorrect eye), but this did not reach statistical significance. Concordance was significantly greater in the leaflet group (mean concordance index 0.85) compared to the non-leaflet group (mean concordance index (0.71) (p <0.001). Comparison of the proportion of non-concordant parents was also statistically different (p <0.005) at 0.23 (95% CI 0.13 to 0.35) for the leaflet group compared to 0.54 (95% CI 0.41 to 0.67) for the control group. Conclusion: A large proportion of patients would benefit by increasing parental knowledge in key areas such as the critical period, importance of occlusion, and potential negative consequences of not treating amblyopia. Written information is a simple, inexpensive, easy to implement, yet effective method of improving parental understanding and subsequent concordance.

Background/aims-Non-concordance has often been reported as a major contributor to the failure of occlusion therapy for amblyopia. In other fields of medicine the extent of a patient's understanding in areas of the disease and treatment has been shown to have both a direct and indirect eVect on subsequent concordance. The aims of this study were to determine the extent of parental non-concordance, to assess their level of understanding in key areas of amblyopia, occlusion therapy, critical period and prognosis, and to discover the parent's own reasons for failing to concord. Methods-Parents of children aged 2-7 years receiving a minimum of 1 hour of occlusion for unilateral amblyopia were recruited. Parental concordance was monitored using a diary and their understanding and reasons for nonconcordance were assessed by a questionnaire. Concordance was analysed by calculating a concordance index, determining the proportion of nonconcordance, and also by classifying the non-concordance on the basis of whether the behaviour was intentional or unintentional and whether the parents were adequately or inadequately informed. Results-Parental non-concordance was defined as failing to occlude less than 80% of the total prescribed time. The median concordance index was 0.75 and the proportion of non-concordant parents was 0.54 (95% CI 0.41 to 0.67) (n = 57). Parental knowledge was poor in areas of the critical period with 23% of parents unaware of an age limit to the treatment. Reasons for non-concordance given by 68% of parents demonstrated poor knowledge. Conclusion-A substantial proportion of the non-concordant parents had poor understanding in areas such as the critical period and errors also occurred in implementing the treatment regimen. Increased parental awareness of the rationale and urgency of the treatment, with reinforcement of details of the regimen, would help to reduce nonconcordance with occlusion therapy. (Br J Ophthalmol 2000;84:957-962) Non-concordance aVects many areas of medicine and the use of occlusion therapy for amblyopia is no exception. Several studies have reported that concordance is an important factor that determines whether or not occlusion is successful.

Test-retest reliability issues may be present for the two filter bars currently still under manufacture. Changes in testing conditions do not significantly affect test results, provided the same filter bar is used consistently for testing. Further studies in children with strabismus having active amblyopia treatment would be of benefit. Despite extensive use of these tests in the UK, this is to our knowledge the first study evaluating filter bar equivalence/reliability.

PurposeTo determine the effect of changing illuminance on visual and stereo acuity.MethodsTwenty-eight subjects aged 21 to 60 years were assessed. Monocular visual acuity (ETDRS) of emmetropic subjects was assessed under 15 different illuminance levels (50–8000 lux), provided by a computer controlled halogen lighting rig. Three levels of myopia (−0.50DS, −1.00DS & 1.50DS) were induced in each subject using lenses and visual acuity (VA) was retested under the same illuminance conditions. Stereoacuity (TNO) was assessed under the same levels of illuminance.ResultsA one log unit change in illuminance level (lx) results in a significant change of 0.060 LogMAR (p < 0.001), an effect that is exacerbated in the presence of induced myopic refractive error (p < 0.001). Stereoacuity scores demonstrate statistically significant overall differences between illuminance levels (p < 0.001).ConclusionsThe findings of this study demonstrate that changes in illuminance have a statistically significant effect on VA that may contribute to test/retest variability. Increases in illuminance from 50 to 500 lx resulted in an improved VA score of 0.12 LogMAR. Differences like these have significant clinical implications, such as false negatives during vision screening and non-detection of VA deterioration, as the full magnitude of any change may be hidden. In research where VA is a primary outcome measure, differences of 0.12 LogMAR or even less could affect the statistical significance and conclusions of a study. It is recommended that VA assessment always be performed between 400 lx and 600 lx, as this limits any effect of illuminance change to 0.012 LogMAR.