Abstract
Purpose: :
To measure the photopic negative response (PhNR) in eyes of multiple sclerosis (MS) patients with and without a history of optic neuritis (ON).
Methods: :
Photopic ganzfeld flash ERGs were recorded from 41 MS patients and 33 age-matched controls. 31 eyes of MS patients had an episode of ON more than six months before (ON>6), 17 eyes, less than six months before (ON<6), and 27 eyes had no history of ON (No-ON). Recordings were made in response to brief red flashes (max=660 nm, ESPION ColorDome) presented on a rod-saturating blue background (max=460 nm). PhNR amplitude was measured from baseline at 65ms after flash in response to a 1.42 cd.s/m2 flash. Standard automatic perimetry (Humphrey field analyzer 750, 30-2 protocol) was performed and peripapillary retinal nerve fiber layer (RNFL) thickness was measured using Stratus OCT and GDx VCC.
Results: :
Average PhNR amplitudes in ON>6, ON<6 and No-ON eyes (-20.1±1.94, -16.78±1.26, -20.7±1.4 µV) were significantly reduced, compared to age-matched controls (-29.8±1.13 µV, p<0.01). In ON>6 eyes, PhNR amplitudes (µV) were significantly correlated (p<0.01) with Mean Deviation (MD) of visual sensitivity (r=0.59) and RNFL thickness, OCT (r=0.72) and GDx (r=0.68). In ON<6 eyes, although PhNR amplitudes were similarly reduced, other measures were less altered, and PhNR was not significantly correlated with MD or either measure of RNFL thickness. In No-ON eyes, PhNR amplitudes were significantly correlated only with RNFL thickness measured by OCT (r=0.55, p<0.05).
Conclusions: :
The PhNR of the photopic ERG is significantly reduced in eyes of MS patients with and without a history of optic neuritis, and the reduction occurs before sensitivity and RNFL losses are observed.
Keywords: electroretinography: clinical • ganglion cells • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)