Retinal Dysfunction in Carriers of Bardet-Biedl Syndrome

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Abstract
Purpose: To determine whether retinal dysfunction in obligate carriers of the Bardet-Biedl syndrome (BBS) could be observed in local electroretinographic responses obtained with the multifocal electroretinogram (mfERG). Methods: Six obligate carriers of the BBS were examined for the study. Examination of each carrier included an ocular examination and mfERG testing of one eye. For the mfERG, we used a 103-scaled hexagonal stimulus array that subtended a retinal area of approximately 40° in diameter. The amplitudes and implicit times in each location for the mfERG were compared with the corresponding values determined for a group of 34 normally sighted, age-similar control subjects. Results: Mapping of 103 local electroretinographic response amplitudes within a central 40° area with the mfERG showed regions of reduced mfERG amplitudes in three of six carriers. Implicit time measurements in the 6 carriers were all normal except for those locations associated with abnormal amplitude reductions in 3 of the carriers. When present, retinal dysfunction was evident in the presence of a normal-appearing fundus. Conclusions: Multifocal ERG testing can demonstrate areas of retinal dysfunction in carriers of the BBS. This test may therefore be useful for identifying some heterozygous carriers of this disease.