Saccadic eye movements in amblyopia: a systematic review and meta-analysis

A systematic review and meta-analysis were conducted to understand the extent to which saccadic latency is impacted by different types of aetiologies. Nine studies were included in the meta-analysis, from 232 amblyopes and 140 controls. Longer saccadic latencies occurred in amblyopes compared to controls. A large and significant effect size (ES) was found when viewing with the amblyopic eye (g = 1.17, I² = 43.69%, <i>p</i> < 0.0001), followed by binocular viewing (g = 0.70, I² = 25.87%, <i>p</i> < 0.0001). However, no significant ES was found with fellow eye viewing (g = 0.12, I² = 42.86%, <i>p</i> = 0.320). Largest ES was noted for mixed amblyopia in the amblyopic eye (g = 1.79, I² = 0%, Q = 0.05, 95% CI = 1.70 to 1.87), followed by strabismic and anisometropic amblyopia, indicating that deficits in saccadic latency are dependent on the amblyopia type (<i>p</i> < 0.001). A positive association was found between saccadic latency and increasing hyperopic refractive error for the amblyopic eye (<i>p</i> = 0.004). A significant increase in saccadic latency ES with age was found for the fellow eye (<i>p</i> = 0.048) and binocular viewing (<i>p</i> = 0.004) conditions, but not for the amblyopic eye viewing (<i>p</i> = 0.077). Saccadic latency is most delayed in the amblyopic eye, particularly in mixed amblyopia, with smaller delays under binocular viewing condition. An increase in saccadic latency is observed with higher levels of hyperopia and as age progresses. These findings highlight the utility of measures of saccadic latency as a way of distinguishing between different types and severities of amblyopia, which may be useful in its diagnosis and treatment.