"Cone dystrophy with supernormal rod electroretinogram": a comprehensive genotype/phenotype study including fundus autofluorescence and extensive electrophysiology

Retina. 2010 Jan;30(1):51-62. doi: 10.1097/IAE.0b013e3181bfe24e.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

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


  • KCNV2 protein, human
  • Potassium Channels, Voltage-Gated