Varikuti PhD thesis final.pdf - Anglia Ruskin Research Online

Further, both the amblyopic subjects showed increased resolutionthresholds with the flanked C condition (I target) and complex interaction Schart (S target) when compared to the isolated C thresholds. The increase inthe flanked and the complex interaction thresholds was minimal in the nonamblyopiceyes but was exaggerated in the amblyopic eyes. This could bebecause of the gradual decrease in resolution across a wider range of visualacuity scores in the amblyopic eyes thus leading to a flatter slope. Further,having a larger magnitude of gaze fixations in amblyopic eyes (0.5° to 8°)than normal eyes (5-10 min arc) (Schor, 1975) could lead to overshooting ofsaccadic fixation resulting in errors and could be the reason for exaggeratedcrowding in amblyopic eyes. Moreover, though the inter-optotype separationin the complex interaction chart (1.0 optotype width) was wider than theflanked Landolt C (nearly 0.7 optotype width), the increase in resolutionthresholds was more for the complex interaction S chart than the flankedLandolt C in both the subjects. This increase in threshold was attributed tothe additional requirement of gaze fixation from one optotype to another inthe complex interaction S chart while the same is absent when using aflanked C. As Flom, Weymouth and Kahneman (1963) showed that whenLandolt C is surrounded by flanking bars the extent of contour interactionwas at 0.95 optotype width in normal eyes but at 1.4 optotype width inamblyopic eyes, the complex interaction S chart (1.0 optotype separation)controls for contour interaction in normal eyes but not in amblyopic eyes.Therefore, the complex interaction thresholds may be influenced by gazefixations and contour interaction in amblyopic eyes but only by gaze30