Purpose: Individuals with amblyopia are known to have functional vision deficits (e.g., reduced reading speed) in spite of good visual acuity in the nonamblyopic eye. We studied and compared eye movements in children with and without amblyopia to examine how a visual scene is explored during visual search.
Methods: Children (six to 16 years of age) in the control group (n = 14) and cases group with anisometropic amblyopia (n = 23) participated in a visual search study, in which they looked for targets in real-world images displayed on a computer monitor. Eyelink 1000 Plus was used to track the eye movements. Three viewing conditions were randomized: dominant/fellow eye, nondominant/amblyopic eye, and binocular viewing. Visual search performance was measured by combining search time and accuracy.
Results: As expected, poorer visual search performance was observed in the amblyopic eye when compared to the controls and fellow eye (P < 0.005). However, the reaction time was longer even in binocular and fellow eye viewing conditions than the controls (P < 0.028). Children with amblyopia made more saccades (17 vs. 12, P = 0.007), without the need to fixate longer (P = 0.312), but with more fixations in the target interest area (4.65 vs. 3.14, P = 0.002) when compared to controls. These eye movement patterns were observed in both the fellow eye and binocular viewing conditions.
Conclusions: In spite of good visual acuity in the fellow eye, children with amblyopia needed to sample the scene with more fixations. Even upon gazing at the target location, they made more fixations before confirming a hit. These search patterns suggest a possible narrower spatial visual span to process the visual information in children with amblyopia.