Temporal reorganization may occur in optic neuritis fellow eyes

The results of this cross-sectional study suggest that delayed visual evoked potential (VEP) latencies in fellow eyes of patients with optic neuritis may reflect temporal reorganization that compensates for delayed transmission to the cortex.

This novel idea, if supported by other studies, may supplant conventional thinking that the VEP delay in fellow eyes of patients with optic neuritis is due to “subclinical” optic neuritis.

The authors studied 17 patients who had a first-ever optic neuritis attack and were followed for 12 to 26 months and 17 age-matched controls in an attempt to identify the source of delayed VEP latencies in the fellow eyes of these patients. To avoid confounding effects of axonal loss, only intact fellow eyes were included.

The authors observed delayed VEP peaks in both affected and fellow eyes. However, while these were derived from prolonged time-to-start in the affected eyes, supporting the existence of demyelination, time-to-start in the fellow eyes was intact and the delay could not be explained by demyelinative lesions along postchiasmal pathways using diffusion tensor imaging.

They conclude that delayed latencies in the fellow eyes may reflect adaptive mechanisms at the cortical level that improve binocular integration over time to adjust for the damage incurred. These data provide a unique demonstration of temporal reorganization that compensates for delayed transmittal of visual information to the cortex.