Effects of Monocular Perceptual Learning on Eye-Specific Cortical Activity in Residual Anisometropic Amblyopia: Evidence From EEG Asymmetry

Purpose: The purpose of this study was to investigate whether a 30-day monocular perceptual learning (PL) program improves visual function and cortical activity in children with residual anisometropic amblyopia. Methods: In this prospective interventional study, 38 patients (8-15 years old) with monocular residual anisometropic amblyopia completed a 30-day home-based monocular PL program using the lateral masking paradigm. Visual function included best-corrected visual acuity (BCVA), area under the log contrast sensitivity function (AULCSF), and stereopsis. Five-minute resting-state electroencephalography (EEG) recordings were obtained at baseline and post-training. Alpha-band (8-13 hertz [Hz]) power spectral density (PSD) was computed for four cortical regions of interest (frontal, parietal, temporal, and occipital) in hemispheres ipsilateral to the amblyopic eye (AE) and the fellow eye (FE). Interocular differences (IODs) in visual function and interhemispheric differences (IHDs) in neural metrics were calculated, and correlations were assessed. Participants were stratified into responders (BCVA improvement > 1 line) and nonresponders to explore baseline characteristics associated with treatment response. Results: At baseline, AE visual function and alpha-band PSD in the ipsilateral parietal and temporal cortices were significantly lower than those of the FE. PL improved AE BCVA and AULCSF, accompanied by PSD reductions in the parietal, frontal, and occipital regions, and shifted parietal and temporal IHD-PSD toward interocular balance. Visual gains correlated with FE-ipsilateral parietal PSD changes, whereas interocular differences in BCVA and AULCSF correlated with parietal IHD-PSD. Baseline parietal IHD-PSD distinguished responders from nonresponders. Conclusions: Residual anisometropic amblyopia is characterized by both visual and cortical interocular asymmetry. Monocular PL enhances visual function and rebalances parietal PSD. Notably, baseline parietal IHD-PSD is associated with responder status at the group level, serving as a candidate neural correlate of training responsiveness. Electrophysiological measures may complement conventional visual tests and inform future work aimed at individualized rehabilitation.