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Chuan Hou, William V Good, Anthony Norcia; Detection of Amblyopia using sweep VEP grating and vernier acuity. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2202.
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Grating and vernier displacement thresholds can be measured with swept-parameter visual evoked potentials (sVEP) and may therefore be useful in pre- or nonverbal subjects. Psychophysical studies indicate that while both grating and vernier acuity are correlated with letter acuity, grating acuity underestimates the full-line letter acuity loss in amblyopia. This study was conducted to determine whether sVEP vernier acuity is better estimate of letter acuity than is sVEP grating acuity in patients with amblyopia.<br />
18 adults with amblyopia (8 anisometroic and 10 strabismic) and 28 age-matched normal vision observers participated the study. In the patient group, letter acuity was between 20/32 and 20/250 in the amblyopic eye and 20/20 or better in the fellow eye when measured with a constant LogMar chart (Bailey-Lovie). In the normal vision group, letter acuity was 20/20 or better in each eye. sVEP vernier acuity was measured using square-wave gratings containing vernier displacements modulated at 3.76 Hz. sVEP grating acuity was measured using sine-wave gratings reversal at 7.5 Hz.<br />
As has previously been reported for psychophysical measurements of vernier and grating acuity, sVEP vernier acuity in both normal vision observers and amblyopic observers faithfully reflected the absolute magnitude of the Letter acuity, while sVEP grating acuity systematically over-estimated letter acuity in the amblyopic eye.<br />
Because sVEP venier acuity is a better estimate of the full letter acuity loss and can be measured without the need for instruction or behavioral responses, it may be useful in assessing visual function in pre- and nonverbal patients.<br />
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