Detection of Mosaic Retinal Dysfunction in Choroideremia Carriers Electroretinographic and Psychophysical Testing

Purpose To test whether choroideremia carriers have a mosaic pattern of retinal dysfunction, as noted in carriers of X-linked recessive retinitis pigmentosa and X-linked retinoschisis. Design Prospective observational case series. Participants Seven obligate choroideremia carriers (age range, 18–72) with visual acuity (VA) of 20/25 or better were recruited into the study. Methods The carriers underwent VA testing (Snellen chart), ophthalmic examination, Humphrey visual field (VF), and multifocal electroretinographic testing. The amplitude and implicit time scales were measured by the algorithm of Hood and Li. The amplitude measures (a scales) and implicit time measures (t scales) were reported abnormal when they were >2 standard deviations above the mean of age-similar normally sighted control subjects. Main Outcome Measures Mapping of local 103 electroretinographic response amplitudes and implicit times. Results Only 1 of the 7 carriers showed abnormal Humphrey VF thresholds, whereas 6 of the 7 carriers showed a mosaic pattern of retinal dysfunction measured by multifocal electroretinographic testing. All 6 carriers showed statistically significant implicit time delays, whereas 4 carriers showed statistically significant amplitude reductions and implicit time delays ( P