Binocular Afferent Synchrony During Development and in Amblyopia: Evidence From Dominance-Referenced Multichannel...

The purpose of this study was to test whether binocular afferent synchrony differs within the visual critical period (CP), beyond the CP, and in amblyopia using dominance-referenced multichannel visual evoked potentials (mcVEPs), and to assess the translational value of interocular timing asymmetries.

We enrolled 117 participants: 33 healthy children and 28 children with amblyopia (all within the CP) and 56 healthy adults (post-CP). Pattern-reversal (PR-VEP) and flash VEP (F-VEP) responses were recorded at O1/Oz/O2 referenced to Fz. Lateral channels were relabeled relative to each participant's dominant eye (dominance-referenced analysis). Primary outcomes were interocular P100 latency difference (indexing synchrony) and N75-P100 amplitude (indexing response balance).

In healthy children, PR-VEPs showed no significant interocular P100 latency differences at either lateral electrode and bilaterally symmetric amplitudes, consistent with preserved synchrony during the CP. Healthy adults exhibited a contralateral latency advantage (shorter P100 for the eye contralateral to the recording electrode) and a dominant-eye amplitude bias, indicating post-CP asynchrony and ocular-dominance asymmetry. In amblyopic children, both PR-VEPs and F-VEPs demonstrated prolonged P100/P2 latency (≈10-12 ms delay) and reduced N75-P100/N2-P2 amplitudes in the amblyopic (non-dominant) eye across hemispheres, reflecting marked disruption of binocular timing and response symmetry.

Interocular latency asynchrony derived from mcVEPs offers a noninvasive, objective readout of binocular afferent timing that may assist in amblyopia stratification and inform timing-targeted, individualized interventions. Longitudinal and interventional studies are warranted to establish causal links between synchrony and cortical plasticity.