DEVELOPMENT OF VERNIER ACUITY IN CHILDHOOD

Purpose, To measure Vernier acuity and resolution development after 3 years of age. Methods. Observers were 39 children with normal vision ( aged 3 to 12 years), 10 adult observers with normal vision (aged 19 to 24 years), and 7 adults with amblyopia. Vernier acuity and resolution were measured using uncrowded static stimuli and a 3AFC psychophysica l paradigm. Curve fitting was used to estimate A,, the age at which th resholds are twice asymptotic levels. Results. Vernier acuity was hype racute (i.e., finer than predicted from foveal cone size or spacing) i n 3- to 4-year-old observers, but developed later (A(2) = 5.6 +/- 1.5 years) than resolution acuity (A(2) = 2.2 +/- 0.9 years). Conclusions. Children's Vernier thresholds are poorer than would be predicted sole ly from their decreased foveal photon capture. Therefore cortical imma turity may play a role in children's relative position acuity deficit, R/V ratios (resolution/Vernier thresholds) for the youngest age group are similar to those for adult nonstrabismic amblyopes, but better th an for strabismic amblyopes.