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Ann M. Skoczenski, Anthony M. Norcia; Development of VEP Vernier Acuity and Grating Acuity in Human Infants. Invest. Ophthalmol. Vis. Sci. 1999;40(10):2411-2417. doi: https://doi.org/.
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purpose. To compare the developmental sequences of two basic measures of
pattern vision, Vernier acuity and grating acuity, using steady state
visual-evoked potentials (VEPs) and an analysis designed to isolate
pattern-specific responses from those due to motion in the Vernier
methods. The authors recorded VEPs from 57 healthy full-term infants and 4
adults. The grating acuity stimulus was a sinusoidal grating,
temporally modulated (appearance-disappearance) at a rate of 3 Hz, with
spatial frequency decreasing in linear steps during each 10-second
trial. The Vernier acuity stimulus was a vertical square-wave grating
with portions of each bar temporally modulated to make offsets appear
and disappear at a rate of 3 Hz. Vernier offset size changed in log
steps from small to large offsets. The authors recorded each
observer’s electroencephalogram (EEG) during multiple presentations of
each stimulus type, and the EEG was digitized and filtered to obtain
the amplitude and phase of the response at the first two harmonics of
the stimulus temporal frequency. Thresholds were estimated with an
extrapolation technique that took into account the signal-to-noise
ratio and phase of the response.
results. VEP Vernier acuity and grating acuity develop at different rates, with
grating acuity approaching adult levels earlier than Vernier acuity.
The within-subject relationship between VEP Vernier acuity and grating
acuity follows the same developmental trajectory established by
previous psychophysical studies of humans and monkeys.
conclusions. This VEP technique provides a rapid estimate of Vernier acuity in
infants. VEP Vernier acuity remains strikingly immature throughout the
first year of life, similar to behavioral Vernier acuity. Because
Vernier acuity is a sensitive measure of amblyopia, this VEP test may
be useful in the future to identify amblyopia and to follow its
treatment progress in pediatric patients.
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