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 psychophysical paradigm. Curve fitting was used to estimate A2, the age at which thresholds are twice asymptotic levels.
Results: Vernier acuity was hyperacute (i.e., finer than predicted from foveal cone size or spacing) in 3- to 4-year-old observers, but developed later (A2=5.6 +/- 1.5 years) than resolution acuity (A2=2.2 +/- 0.9 years).
Conclusions: Children's Vernier thresholds are poorer than would be predicted solely from their decreased foveal photon capture. Therefore cortical immaturity 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 than for strabismic amblyopes.
(C) 1997 American Academy of Optometry