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M. J. Moseley, C. E. Stewart, A. R. Fielder, D. A. Stephens, ROTAS Cooperative; Changes in Vernier Acuity and Visual Acuity During Treatment for Amblyopia. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4884.
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© ARVO (1962-2015); The Authors (2016-present)
To compare the response of amblyopic children to occlusion therapy recorded with letter and vernier acuity.
Data were obtained from 46 children with amblyopia (4 strabismic, 30 anisometropic, 12 mixed) of mean (sd) age 5.5±1.6 years. All were participants in the Randomized Occlusion Treatment for Amblyopia study (ROTAS) in which they were prescribed either 6 or 12 hours of occlusion per day. Monocular logMAR letter acuity (ETDRS) and vernier acuity using the forced-choice vernier test (Miller et al., Invest. Ophthalmol Vis Sci 2002;43:2665) were recorded at the start, end, and where possible, at weekly intervals. Patch wear was objectively recorded using an occlusion dose monitor. Outcomes were quantified as change in the amblyopic eye acuity and difference between amblyopic and fellow eye acuities expressed in logMAR (residual amblyopia).
Letter and vernier acuities for amblyopic eyes were significantly reduced (0.46±0.28 and -0.18±0.49) respectively at the beginning of therapy. Changes in visual acuity (0.23±0.17 logMAR) were not significantly different (p=0.11) from changes observed in vernier acuity (0.32±0.35 logMAR) as a result of therapy. Residual amblyopia as measured with visual acuity was 0.42±0.28 at the start and 0.24±0.22 at the end of occlusion. Residual amblyopia as measured with vernier acuity was 0.44±0.39 at the start and 0.23±0.26 at the end of occlusion.
Vernier acuity appears to detect a similar magnitude of spatial deficit as that measured with visual acuity. Thus vernier acuity does not provide additional information of an amblyopic child's visual deficit. However, in circumstances where it is only possible to record a child's acuity using single letter optotypes (e.g. between 3-4 years) a measure of vernier acuity would be predictive of the greater loss of visual acuity that would be present had it been possible to record with linear optotypes.
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