ASSESSMENT OF LOCAL RETINAL FUNCTION IN PATIENTS WITH RETINITIS-PIGMENTOSA USING THE MULTIFOCAL ERG TECHNIQUE

To assess local retinal function in patients with retinitis pigmentosa (RP), multi-focal ERGs and local thresholds (static visual fields) we re obtained on eight RP patients with visual acuities of 20/25 or bett er. All eight patients showed multi-focal responses with normal timing within the central 5 deg. However, there were few responses with norm al timing in the areas outside the central 7.5 deg, except in the case of the only patient with a 30 Hz full-field response with normal timi ng. Since full-field ERGs are dominated by responses from the peripher y, this finding supplies a foundation for the commonly observed delays in the full-field cone ERGs of patients with RP. With respect to ampl itude, only two patients showed multi-focal responses with near normal amplitudes anywhere in the field. The loss of amplitude at any point was not a good predictor of visual sensitivity in the Humphrey visual field. On the other hand, all areas with normal timing had near normal sensitivity. Timing changes appear to be an early indication of local retinal damage to the cone system. Nearly all areas with sensitivity losses greater than 0.5 log unit, and some areas with near normal sens itivity, showed significantly delayed multi-focal ERGs. Finally areas with extreme sensitivity loss show multi-focal responses with a wide r ange of amplitudes and implicit times across patients, suggesting diff erent mechanisms of disease action in different patients. (C) 1997 Els evier Science Ltd.