title: "Cone dystrophy with supernormal rod electroretinogram": a comprehensive genotype/phenotype study including fundus autofluorescence and extensive electrophysiology.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors: Department of Electrophysiology, Moorfields Eye Hospital, London, UK. anthony.robson@moorfields.nhs.uk
authors: Anthony G
authors: AG
authors: Robson
authors: Andrew R
authors: AR
authors: Webster
authors: Michel
authors: M
authors: Michaelides
authors: Susan M
authors: SM
authors: Downes
authors: Jill A
authors: JA
authors: Cowing
authors: David M
authors: DM
authors: Hunt
authors: Anthony T
authors: AT
authors: Moore
authors: Graham E
authors: GE
authors: Holder
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003623:Dark Adaptation; D004594:Electrophysiology; D004596:Electroretinography; D005451:Fluorescein Angiography; D005838:Genotype; D006801:Humans; D008875:Middle Aged; D009154:Mutation; D010641:Phenotype; D010775:Photic Stimulation; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics*; D017949:Retinal Cone Photoreceptor Cells / Q000473:pathology*; D012162:Retinal Degeneration / Q000175:diagnosis / Q000235:genetics / Q000503:physiopathology; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology*; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult
chemical_list: C489610:KCNV2 protein, human; D024642:Potassium Channels, Voltage-Gated