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A. Chandna, S.I. Chen, A.M. Norcia, M.W. Pettet; VEP Vernier and Grating Acuity in Children With Untreated Amblyopia: A Controlled Prospective Treatment Study . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2461.
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© ARVO (1962-2015); The Authors (2016-present)
In adults with amblyopia, vernier and Snellen acuity measures are well correlated whereas grating acuity underestimates amblyopia. We compared the relative sensitivity of VEP vernier and grating acuity measures to the amblyopic deficit in previously untreated children to ask whether a similar relationship exists before and during treatment.
Normal children (n =16) and untreated amblyopes (n =34) under eight years old were studied longitudinally during clinical treatment. The swept parameter VEP was used to estimate acuity thresholds by extrapolating the response functions to zero amplitude. Vernier displacement and spatial frequency thresholds were averaged across observers at key treatment milestones in amblyopes. Normals underwent the same assessment (every 4 months) for 12 months. Grating stimuli were swept between 32 and 2 c/deg using pattern–reversal and on–off modulation. Vernier offset was swept from 0.5 to 8 arcmin using two temporal frequency modulations.
There was no significant difference in optotype interocular acuity differences (IAD) between anisometropic (0.38 LogMAR) and strabismic (0.46) amblyopes before treatment. Untreated anisometropes demonstrated significant (p = 0.02) IAD for VEP vernier acuity but strabismics did not. VEP grating IADs were also greater for untreated anisometropic than strabismic observers. Optotype IADs were significantly (p = 0.003) greater than for vernier or grating acuity for all untreated amblyopes. On optotype measures the greater treatment effect occurred for strabismics rather than anisometropes while the opposite was true for grating acuity. The anisometropic dominant eye developed super–normal vernier thresholds despite occlusion treatment and contributed to further increases in vernier IADs after stopping treatment.
VEP vernier acuity is less sensitive than optotype measures of amblyopia in untreated children especially in strabismus. The two types of amblyopia, strabimic and anisometropia show distinctive patterns of loss and response to treatment.
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