Effects of Strabismus Surgery on Fixational Eye Movements
Fatema Ghasia; Charles Gallagher
Cole Eye Institute, Cleveland Clinic
Introduction: Microsaccades are miniature eye movements that constantly change the gaze during attempted visual fixation. Saccades and microsaccades represent an oculomotor continuum and are produced by common neural sensory and motor machinery. Strabismic patients have impaired binocular horizontal saccades and fixational eye movements. We examined the fixational eye movements in strabismic patients with and without latent nystagmus (LN) before and after surgery.
Methods: Eye movements were recorded with infrared video-oculography in 13 strabismic patients (stereopsis present=3; stereopsis absent=10) with LN (n=8) and without LN (n=5) and 13 controls while they performed a visual fixation task before and after strabismus surgery.
Results: Strabismic patients with and without LN had greater fixation scatter in both the viewing and non-viewing eyes. (Bivariate contour ellipse area (BCEA) viewing eye: controls=-0.49, without LN = -0.28, with LN=0.06, p<0.05 one way ANOVA; non-viewing eye: controls = -0.48, without LN = -0.04, with LN = 0.55, p<0.05 one way ANOVA). The fixational saccades in strabismic patients without LN were disconjugate. The disconjugacy of fixational saccade decreased after strabismus repair (preop =0.19 ± 0.33; postop =0.14 ± 0.23, p=0.01 unpaired t-test). A similar decrease in the disconjugacy of amplitude of quick phases of LN was noted after surgery (preop =0.43 ± 0.70; postop =0.26 ± 0.58; p<0.001 unpaired t-test).
Discussion: Fixational saccades and quick phases of LN are disconjugate in strabismic patients.
Conclusion: This exceed the capabilities of the sensory system to achieve fusion. Strabismus repair reduces the disconjugacy thereby facilitating fusion in strabismus patients.
References: 1)Kapoula Z, Bucci MP, Eggert T, Garraud L. Impairment of the binocular coordination of saccades in strabismus. Vision research 1997;37(19):2757-66
2) Ghasia FF, Otero-Millan Jorge, Shaikh AG. Abnormal fixational eye movements in strabismus. BJO 2017