Binocular imbalance measured by SSVEP predicts impaired stereoacuity in amblyopia

Purpose: The current study aims to implement steady-state visual evoked potentials (SSVEPs) in quantifying the binocular imbalance of amblyopia and to assess the predictive value of SSVEP-derived indices for amblyopic stereoacuity.

Methods: We measure frequency-tagged SSVEP responses elicited by each eye (F1 = 6 Hz through the fellow eye; F2 = 7.5 Hz through the amblyopic eye) within a binocular rivalry paradigm among a cohort of anisometropic amblyopic observers (n = 29, mean age: 12 years). Binocular suppression was quantified by assessing the disparity in SSVEP amplitudes between the eyes, while the strength of interocular interaction was evaluated through the intermodulation response at F1+F2 = 13.5 Hz. Subsequent analyses explored the associations between these neural indices and relevant behavioral metrics in amblyopia.

Results: Results reveal a significant difference in SSVEP amplitudes elicited from the fellow eye and the amblyopic eye, with the former exhibiting notably higher responses. Moreover, the fellow eye demonstrated prolonged dominance duration compared to its amblyopic counterpart. Furthermore, a negative correlation between binocular suppression and interocular interaction was observed, with stereoacuity showing a significant correlation with binocular suppression. Utilizing stepwise mulptiple linear regression analysis, we established that a predictive model combining binocular suppression and visual acuity of the amblyopic eye provided the best prediction of stereoacuity.

Conclusions: These results highlight the potential of binocular suppression, as assessed by SSVEPs within a binocular rivalry paradigm, as a promising neural predictor of stereopsis in amblyopia.