Purchase this article with an account.
AM Skoczenski, A Soffer, MA Otero, RA Leabman; Spatial Interactions In Vernier Acuity During Infancy And Childhood . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3991.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Developmental and clinical studies of vernier acuity often use stimuli comprised of multiple vernier offsets embedded in gratings. In these stimuli, factors such as grating visibility, spatial summation, or crowding may contribute to measured thresholds. We investigated age-related changes in the importance of these factors during normal development. Method: We measured steady-state visual evoked potentials in 10 3-month-old infants, 10 5-month-olds, 6 children (4.5-7 years), and 4 adults, all with normal vision. Vernier offsets appeared and disappeared at a rate of 5 Hz in vertical squarewave gratings (80% luminance contrast). During each 10-second trial, offset size was swept in log steps from 15 to 1 arc minutes for infants (7.5-0.5 min for children; 3.5-0.2 min for adults). We recorded the amplitude and phase of the 5 Hz vernier pattern response and estimated threshold by extrapolating the amplitude response function to zero microvolts, taking phase and error statistics into account. There were 7 carrier spatial frequency (SF) conditions: 0.5, 1, 2, 4, 8, 12, and 16 c/deg. Infants were tested at 0.5-2 c/deg, children at 0.5-4 c/deg, and adults on all 7 conditions. Results: Adults' thresholds were in the hyperacuity range and did not vary significantly for carrier SFs between 0.5 and 8 c/deg, but were degraded above 8 c/deg. All children and one half of the infants (5/10 in each infant age group) showed threshold improvement when the carrier SF was 1 c/deg compared to 0.5 c/deg, and some showed additional improvements at 2 c/deg. Children's thresholds worsened in the 4 c/deg condition. Conclusion: Improvements in infants' and children's vernier acuity with increasing spatial frequency of the carrier grating may be due to spatial summation across the greater number of offsets present in the 1 c/deg condition compared to the 0.5 c/deg condition. Spatial summation in this carrier SF range had no effect on adults' thresholds. 4.5- to 7-year-old children's thresholds worsened at lower carrier SFs than did adults' thresholds, even though children at this age have adult-like grating resolution. This suggests that grating visibility does not account for children's threshold degradation at 4 c/deg; crowding is a more likely candidate factor in this case.
This PDF is available to Subscribers Only