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PURPOSE: The purpose of this study was to characterize the clinical, electrophysiologic, and genetic features in "cone dystrophy with supernormal rod electroretinogram (ERG)." METHODS: Twenty-four cases between 5 and 59 years of age were ascertained. Full-field ERGs, incorporating the international standards, were used to derive intensity-ERG response functions. ON-OFF ERGs were performed. Fundus autofluorescence imaging was performed on 15 subjects. Deoxyribonucleic acid was available in 18 cases and was screened for a mutation in KCNV2. RESULTS: Photophobia and nyctalopia were common. Autofluorescence was variable but often showed a ring-like area of high density that in middle-aged individuals, usually surrounded by an area of macular retinal pigment epithelial atrophy. Scotopic ERG amplitudes overlapped with the normal range but had characteristic a- and b-wave intensity-response functions; all had a broadened a-wave to the brightest flash. Photopic ERGs were abnormal; there was a delay in some ON and most OFF responses. Mutations in KCNV2 were detected in 18 cases, including 4 with novel mutations. CONCLUSION: Individuals with mutations in KCNV2 manifest a wide range of macular and autofluorescence abnormalities. A ring-like area of parafoveal high density autofluorescence is common. ERG amplitudes are variable, but the intensity-ERG response functions and bright flash ERG waveforms are pathognomonic.

Original publication




Journal article



Publication Date





51 - 62


Adolescent, Adult, Child, Child, Preschool, Dark Adaptation, Electrophysiology, Electroretinography, Fluorescein Angiography, Genotype, Humans, Middle Aged, Mutation, Phenotype, Photic Stimulation, Potassium Channels, Voltage-Gated, Retinal Cone Photoreceptor Cells, Retinal Degeneration, Retinal Rod Photoreceptor Cells, Visual Acuity, Young Adult