Preservation of macular oscillatory potentials in eyes of patients with retinitis pigmentosa and normal visual acuity.

PURPOSE To study the functional changes in the macula of the retina in the early stage of retinitis pigmentosa (RP), by analyzing each component of the focal macular electroretinogram (fmERG). METHODS fmERGs were recorded from 39 patients with RP with normal visual acuity (>1.0) under direct fundus observation using a modified infrared fundus camera and 5 degrees , 10 degrees , and 15 degrees stimulus spots. The amplitudes and implicit times of the a-wave, b-wave, and oscillatory potentials (OPs) in the patients with RP were compared to those from 30 age-similar normal control subjects. RESULTS The amplitudes of the different components of the fmERGs in patients with RP ranged from severely reduced to normal. The degree of amplitude reduction increased as the size of the stimulus spot increased in the patients with RP. The relative amplitudes of the OPs (67% of the mean in normal subjects) were better preserved than that of the b-wave (46%) and the a-wave (39%) in a 10 degrees spot in the patients with RP. CONCLUSIONS The relative preservation of the OPs in the patients with RP could be due to either the buffering effect of the large receptive fields of the OP generators or to the retinal remodeling after the progressive loss of photoreceptors. Recordings of each component of fmERG can provide important information on the different layers of the central retina in RP eyes and can add to the understanding of the pathophysiology of RP.