Abstract
Strabismic amblyopes experience constant interocular suppression during habitual binocular viewing to avoid diplopia and confusion. We measured depth and extent of suppression across the visual field of strabismic and micro-strabismic observers using luminance-modulated (LM) and contrast-modulated (CM) noise stimuli. LM and CM noise ring stimuli extended across 24 deg of the visual field. Nine strabismic observers made forced-choice judgements about the strength of a dichoptically presented sector that was positioned systematically around the rings within the stimulus field. Suppression for both LM and CM stimuli was assessed as CM stimuli have revealed greater depths of suppression in normal eyes with inter-ocular blur differences and may be more sensitive to true binocular disruption, such as in strabismus. Both strabismics and micro-strabismics showed deeper suppression for CM than LM stimuli (p< 0.05). Suppression was central or combined with a broader horizontal hemispheric asymmetry, depending on the stimulus used. A significant positive correlation was found between amblyopia (inter-ocular visual acuity difference) and suppression depth (r~+0.70); stereo-acuity level and suppression depth were negatively correlated (r~-0.85). Unlike inter-ocular blur suppression, the mapping procedure in strabismic observers revealed more localised regions of suppression, indicating selective suppression mechanisms. CM stimuli revealed greater levels of suppression than did LM stimuli in observers with degraded binocularity. Suppression can therefore be more sensitively measured and monitored by combining stimulus types during diagnosis and treatment of amblyopia.
Meeting abstract presented at VSS 2015