TRAINING "BINOCULAR CORTICAL NEURONS" IN ADULTS WITH AMBLYOPIA

POSTER PRESENTATIONS

Objective. The purpose of this study is to assess the validity of a perceptual learning paradigm that uses stimulation of visual cortex at corresponding retinal locations for treatment of adult amblyopia. Background. Binocular stimuli with mixed interocular contrast can improve vision in amblyopes. In a new training paradigm we exploited the fact that the receptive field (RF) structure of the typical binocular V1 neuron shows similar tuning for stimuli presented to left eye or right eye, by presenting Gabor patches to corresponding retinal locations. Methods. Stimuli were binocular hexagonal arrays of Gabor patches, of varied orientation, with sizes spanning 3 octaves, also scaled for cortical magnification. The pattern was updated at 30 Hz and subtended 30 deg wide x 40 deg tall on the plasma display, viewed at 145 cm through a four-mirror stereoscope. Monocular and binocular test trials of variable duration (controlled by a staircase procedure) alternated with 1-5 sec training trials. Test trial stimuli contained one octant within which all orientations were the same, and subjects indicated this octant as quickly as possible using a numeric keypad. Subjects were anisometropic amblyopes, divided into a Mixed-contrast group (non-unity interocular contrast ratio, ICR) and a Fixed-contrast group (ICR=1). ICR in the Mixed group was set using procedures adapted from Mansouri et al (2008) and Ding et al (2011), respectively. Each subject ran ten sessions of 40 minutes. Results. Duration thresholds decreased by 2.3 sec and 1.8 sec in the Mixed and Fixed groups, respectively, with a 53 significant difference (p < 0.05). Stereoacuity thresholds decreased by 0.68 log10 arcmin for Mixed, which was more than for Fixed (0.35; different at p < 0.05). LogMAR acuity improved by 0.16 for Mixed and 0.9 for Mixed, significantly different (p < 0.05). Conclusion. Dichoptic gabor pattern stimulation yielded rapid improvement in stereoacuity and visual acuity. This form of perceptual learning has potential for significant functional improvement in amblyopes. Grants. K23 EY022669 (NEI/NIH) to Dr. Law