Integrating classical binocular vision testing with objective eye-tracking to characterise oculomotor dysfunction in strabismus.

CLINICAL RELEVANCE: Objective eye-tracking provides quantitative metrics of oculomotor control and reading performance that complement conventional binocular vision testing. Integration of eye-movement analysis into clinical practice may support more comprehensive functional assessment of patients with binocular vision disorders.

BACKGROUND

The aim of this work is to compare oculomotor parameters between patients with strabismus and healthy controls, integrating classical optometric/ophthalmological tests with objective video-oculography and eye-tracking measurements.

METHODS

This observational cross-sectional study included 56 participants (20 with manifest strabismus and 36 visually normal controls). All subjects underwent a standardised optometric and ophthalmological examination, including refraction, visual acuity, cover test, near point of convergence, stereopsis, and Worth 4-dot testing. Oculomotor function and reading performance were objectively assessed using a binocular eye-tracking system, which recorded Developmental Eye Movement (DEM) test performance, fixation stability, horizontal saccades, smooth pursuit, and reading-related eye-movement metrics. Between-group comparisons were performed, effect sizes were calculated, and penalised logistic regression and receiver operating characteristic (ROC) analyses were used to identify the most discriminative variable.

RESULTS

Participants with strabismus showed significantly longer DEM vertical and horizontal times (both p = 0.002), higher DEM error rates (p = 0.006), reduced reading speed (p < 0.001), and increased fixation and saccadic counts compared with controls. In penalised multivariable modelling, DEM times, DEM error measures, and reading speed emerged as the strongest independent predictors of strabismus. ROC analyses demonstrated good to excellent discriminatory accuracy for DEM horizontal time, DEM vertical time, total DEM errors, and reading speed (AUC > 0.80).

CONCLUSIONS

Strabismus is associated with marked impairments in oculomotor sequencing and reading-related eye-movement control. Objective eye-tracking-derived metrics, particularly DEM performance and reading efficiency, provide clinically relevant information beyond traditional binocular vision tests and may serve as sensitive functional biomarkers for the characterisation of strabismus.