Visually Guided Saccades in Amblyopia and Strabismus: The Roles of Sensory Deficits and Nystagmus

Purpose: To determine how amblyopia subtype, visual acuity, stereoacuity, and nystagmus influence visually guided saccades across viewing conditions in subjects with amblyopia and strabismus. Methods: Visually guided saccades were recorded using video‑oculography in controls, anisometropic amblyopia, strabismic amblyopia, and strabismus without amblyopia subjects under binocular and monocular viewing. Saccadic latency, gain, disconjugacy, movement strategies, and main sequence relationships were quantified. Linear mixed effects models assessed group and viewing condition effects, and χ2 tests compared saccadic strategies and diagnostic distributions by nystagmus status. Results: Saccadic latency varied with viewing condition and was most strongly associated with amblyopic eye visual acuity, with prolonged latencies during amblyopic eye viewing in anisometropic and strabismic amblyopia. Subjects with strabismic amblyopia also showed increased latencies during binocular viewing. Reduced saccadic gain and increased reliance on multiple‑step saccades were most pronounced in strabismic amblyopia and were strongly associated with nystagmus. Saccadic disconjugacy was greatest in subjects with reduced stereoacuity and was most evident during binocular viewing. Main sequence relationships were preserved across all cohorts, including those with nystagmus. Conclusions: Visually guided saccade abnormalities in amblyopia and strabismus reflect distinct contributions of sensory deficits and nystagmus. Although saccadic latency primarily indexes sensory access to the target, reduced gain and altered movement strategies are closely associated with nystagmus. Preservation of main sequence kinematics indicates intact saccadic motor execution. These findings identify nystagmus as an important modifier of saccadic accuracy and underscore the need to account for nystagmus when interpreting oculomotor behavior in amblyopia and strabismus, with relevance to visuomotor tasks such as reading and visual scanning.