Multifocal electroretinography in retinitis pigmentosa

PURPOSE: To investigate the diagnostic potential of multifocal electroretinography for the evaluation of retinal affection by retinitis pigmentosa in a clinical setting. METHODS: For this prospective study, multifocal electroretinograms were obtained from 38 patients who matched the inclusion criteria of either a detectable photopic Ganzfeld response or visual fields of 10 degrees or more, and from 30 normal volunteers. Recordings were performed with the visual evoked response imaging system, using a resolution of 61 hexagonal elements within a 30-degree visual field, The results of the left eye of each patient and control subject were used for statistical evaluation by the Mann Whitney U test. RESULTS: The 38 eligible patients included those with Usher syndrome types I and II (one patient and six patients, respectively) and those with autosomal recessive (18), X-recessive (two), and autosomal dominant (11) forms of retinitis pigmentosa. In 27 (71%) of these 38 patients, at least a central response of the multifocal electroretinogram was detectable. Loss of multifocal electroretinogram response density in patients with retinitis pigmentosa was significant (P <.00001) in all five eccentricity groups (concentric rings), with a progression from center to periphery. Implicit time was significantly elevated in the third eccentricity group (P <.0038) and increased further toward the periphery (P <.00001). The results did not differ notably between retinitis pigmentosa subgroups. CONCLUSIONS: Because the multifocal electro retinogram differentiates between affected and nonaffected retinal areas, eccentricity dependent changes in both amplitude and implicit time were found. It can therefore add to the diagnostic information of many patients with retinitis pigmentosa.