Abstract
Abstract: :
Purpose: To compare letter and vernier acuity in amblyopic and visually normal children. Methods: Data were obtained from 21 visually normal children (mean age = 5.7 ± 0.6 years) and 48 children with amblyopia (mean age = 6.2 ± 1.6 years) (strabismic (n=19), anisometropic (n=18), mixed (n=11)). Monocular measurements of logMAR letter acuity and vernier acuity using the forced–choice vernier test (Miller et al., Invest Ophthalmol Vis Sci 2002;43:2665) were recorded for all subjects. Results:Letter and vernier acuities for amblyopic eyes were significantly reduced (p<0.01) (0.41 ± 0.28 and –0.22 ± 0.49 logMAR respectively) compared to fellow eyes (0.04 ± 0.1 and –0.68 ± 0.18 logMAR). Letter acuities of amblyopic children’s fellow eyes and visually normal subjects’ eyes were identical (0.04 ± 0.1 and 0.04 ±0.05). In contrast fellow eyes demonstrated significantly reduced (p<0.01) vernier acuity compared to the visually normal group (–0.68 ± 0.18 and –0.8 ± 0.12 respectively). A greater amblyopic deficit was demonstrated for the vernier acuity task (p<0.01). No significant difference between letter acuity and vernier acuity scores or letter acuity/vernier acuity ratios were observed for the different categories of amblyopia. Vernier deficits were highly correlated to letter acuity deficits for anisometropic (r=0.93) and mixed (r=0.75) amblyopes, however strabismic amblyopes demonstrated a vernier acuity deficit independent of their letter acuity deficit (r=0.23). Conclusions:The vernier acuity task detected a greater amblyopic deficit suggesting the test would be more sensitive for the detection of amblyopia. Amblyopes fellow eyes demonstrated abnormalities in vernier acuity providing further evidence that the fellow eye of amblyopic observers is not normal. The vernier acuity deficit in strabismic amblyopes appears independent of letter acuity.
Keywords: amblyopia • visual acuity • visual development