On- and off-responses of the photopic electroretinograms in x-linked juvenile retinoschisis

PURPOSE: To examine the physiologic condition of the middle retinal layer of patients with X-linked juvenile retinoschisis (xlRS) by studying the on- and off-responses of the photopic electroretinograms (ERGs). METHODS: Eleven unrelated Japanese men (mean age; 24.9 ± 7.6 years) who were clinically diagnosed with xlRS and molecularly confirmed as having XLRS1 mutations were investigated. For the photopic ERGs, the a-, b- and d-wave amplitudes elicited by long duration stimuli were recorded, and the responses from the xlRS patients were compared to those recorded from normal subjects ( n = 14, mean age, 27.5 ± 4.5 years). We also examined the relationship between the photopic ERG responses and the genotype. RESULTS: No significant difference was found between the a- and d-wave amplitudes in the xlRS patients (34.2 ± 8.7 μV, 52.5 ± 10.4 μV, respectively), and those in normal subjects (40.4 ± 10.3 μV, 44.7 ± 6.3 μV, respectively). The mean b-wave amplitude in the xlRS patients was significantly smaller (10.5 ± 7.7 μV) than the mean of normal subjects (46.4 ± 10.2 μV) ( P < 0.0001). No significant correlation was found between the ERG responses and the locus of the mutation. CONCLUSION: The photopic ERG demonstrated considerable impairment of the on-pathway arising from an abnormality of the on-bipolar cells or possibly secondary to Müller cell abnormality in xlRS.