First-order underlie second-order loss in temporal perception of anisometropic amblyope

Previous studies have suggested that the processing of first-order and second-order stimuli by the amblyopic eye (AE) is defective, and it is undressed whether its reduced temporal perception could be separated from its impaired first-order spatial perception. In this study, we measured the contrast/modulation sensitivity of first-order and second-order sinusoidal grating stimuli, over six temporal frequencies, for eight anisometropic amblyopes and ten normal subjects. The AE presented deficit on first-order temporal perception and carrier detection, comparing to their fellow eye (FE) and to the control eyes (CE) of normal subjects. On second-order temporal perception, measurements were performed in two conditions, with identical or balanced carriers. The AE showed defective perception with identical carriers, but no significant deficit with balanced carriers. The FE showed normal performance on all tasks compared to CE. Our results suggest that the reduced second-order temporal perception in amblyopia could be attributed to its impaired first-order spatial perception.