Oculomotor Dysfunctions in Nonreading Tasks in Children With Dyslexia: Saccadic and Optokinetic Findings.

BACKGROUND

Dyslexia has been associated with atypical eye-movement control, but whether such differences arise only during reading or reflect broader oculomotor control remains debated.

METHODS

We compared 40 children with dyslexia and 40 age/sex matched controls (8-12 years). Binocular eye movements were recorded with infrared video-oculography (VOG) using a clinical VNG platform's oculomotor module. Participants performed a random-step horizontal saccade task (targets at ±15° and ±20° from midline (step amplitudes 5°-40°); pseudo-random 3-4 s intervals). Saccades were detected with manufacturer thresholds (40°/s, 800°/s2). Primary outcomes were peak velocity (°/s), accuracy (%) and latency (ms); optokinetic responses (OKR) were analysed for each eye, and we report the interocular OKR difference (%). Trials with blinks/track-loss were excluded a priori.

RESULTS

Compared with controls, children with dyslexia showed slower saccades (307.5°/s vs. 453.5°/s), lower accuracy (71.5% vs. 98.5%) and longer latency (260.0 vs. 131.5 ms), all p < 0.001. Right-eye OKR was reduced, whereas left-eye OKR did not differ significantly, and the interocular OKR difference was significantly larger in dyslexia. These group differences remained significant after adjustment for relevant socio-demographic covariates.

CONCLUSIONS

Children with dyslexia exhibited robust oculomotor differences during a nonreading task, consistent with altered visually guided saccade control. These results are associative rather than causal and suggest that oculomotor measures may provide complementary insight into dyslexia.