Abstract
Purpose :
Visual search difficulties and abnormal fixation eye movements are seen in amblyopia. The purpose of the study was to examine eye movements while viewing contrast balanced dichoptic images in amblyopic subjects and correlate the performance with visual and stereo-acuity deficits, and inter-ocular suppression.
Methods :
Eye movements were recorded using infrared video-oculography from 5 controls,10 amblyopic subjects (anisometropic=5, strabismic=2, mixed=3; 5=moderate,5=treated amblyopia with patching) during dichoptic gaze holding, visual search and spot the picture difference tasks (12 images for 20s each). Fixation locations, microsaccades, saccades and intersaccadic drifts were analyzed. The regions of interest were divided within fellow eye(FE) and amblyopic eye(AE) targets. The correctly identified targets and reaction times were recorded. An adaptive staircase method was used to measure visual acuities during FEV, AEV and BEV and inter-ocular suppression using Dichoptic Motion Coherence. The threshold of inter-ocular suppression at given FE contrast was determined by the number of dots required to correctly identify the motion coherence at a given FE contrast and area under the curve was computed. Stereopsis was measured using Titmus fly test.
Results :
Amblyopic and treated subjects were able to spot the FE targets but took longer than controls. The ability to spot the AE targets in dichoptic environment was highest in controls at 67%, 64% in treated and 42% in moderate amblyopia. Increased inter-ocular suppression was seen in amblyopia with high AUC of 1430.7, 704.2 in treated and 394.2 in controls. Stereopsis deficits including absent stereopsis was seen in treated amblyopia.
Conclusions :
Our findings suggest dichoptic visual search performance is impaired with increased inter-ocular suppression, fellow eye and stereopsis deficits observed in amblyopic subjects including those with prior treatment. Alternative therapeutic approaches that target inter-ocular suppression and restore stereopsis and fellow eye deficits are required.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.