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Amithavikram Hathibelagal, Moshe Eizenman, Elizabeth Irving, Susan Leat; Visual fixation as an objective measure of visual acuity in infants. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1305.
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© ARVO (1962-2015); The Authors (2016-present)
To compare visual acuity (VA) estimates derived from the analysis of infants’ visual scanning behavior using a Gaze-tracker (GT) method with visual acuity estimates obtained by Teller Acuity Cards (TACs).
Binocular visual acuities were measured in 14 typically-developing infants aged between 3 and 12 months. Visual scanning patterns were measured by a remote eye-tracking system that requires minimal subject cooperation. The visual stimuli were computer-generated gratings of spatial frequency ranging from 0.32 cycles per degree (cpd) to 42 cpd presented randomly in one of 4 positions on the screen. Gratings were judged as seen by the infants when the relative fixation time on the grating exceeded a pre-determined threshold. VA was measured with a staircase protocol. VA was measured on two visits with both the Gaze tracker and TACs. In both the tests, the tester was unaware of the position of the grating and the absolute spatial frequency.
Ninety-three percent of the visual acuity estimates of the GT and the TACs were within 1 octave for the first visit and 79% for the second visit. Both the TACs and the GT had repeatability of 86% within 1 octave between visits. Eighty-three percent of the GT acuity values were within the published 90% normal limits for age although on average the GT gave significantly better acuity than the TACs (paired t-test, p= 0.011). There was an increase in VA measured with the gaze tracker with increasing age (r=0.60, p=0.023 for the first visit and r=0.67, p=0.008 for the second visit). The mean test duration for the GT was similar to the TACs (5 minutes). The testability of both TACs and GT was 100% in both visits for all infants.
The agreement between the TACs and GT and the correlation with age validates the measurements of the gaze tracker. The repeatability of the gaze tracker is similar to that of the TACs and the results demonstrate the potential for an automated test of infant visual acuity. We have previously shown that the GT accurately measures grating acuity in adults (American Academy of Optometry, 2012), so the higher measures of VA with the GT in infants appear to be genuine.
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