FOCAL VISUAL-EVOKED POTENTIALS GENERATED BY SCANNING LASER OPHTHALMOSCOPE IN PATIENTS WITH AGE-RELATED MACULAR DEGENERATION TREATED BY PERIFOVEAL PHOTOCOAGULATION

Perifoveal laser photocoagulation has been proposed for the treatment of subfoveal neovascular membranes in age-related macular degeneration . We evaluated residual function in seven eyes of six treated patients by means of transient focal visual potentials evoked with a scanning laser ophthalmoscope. The site of the preferred retinal locus was dete rmined. The modulation of the helium-neon laser beam generated three t ests (a homogeneous 6 x 6 degrees square-offset and onset-and two alte rnating pattern checkerboards 6 x 6 degrees and 2.5 x 2.5 degrees 60', 2 Hz) projected onto the preferred retinal locus. The focal visual ev oked potentials were recorded. One eye had an unstable fixation with n o discernible focal visual evoked potentials. The other six eyes had a stable fixation located in the superior retina, temporally for the ri ght eyes and nasally for the left eyes. The homogeneous 6 x 6 degrees square evoked discernible responses in all six patients. The two check erboards evoked discernible responses in five of six patients. These r esults were compared with those recorded in four controls in whom the three tests were projected onto the same retinal areas as in the patie nts. Evoked responses were more often recorded in the preferred retina l locus of the treated patients with age-related macular degeneration than in the corresponding retinal areas of the controls. The scanning laser ophthalmoscope allowed us to control the site of stimulation in the patients' and controls' retinas. These preliminary results suggest that there may be a functional plasticity of the visual system after therapeutic laser-induced central scotoma.