title: Phenotypic characteristics including in vivo cone photoreceptor mosaic in KCNV2-related "cone dystrophy with supernormal rod electroretinogram".
abstract: OBJECTIVE
  To report phenotypic characteristics including macular cone photoreceptor morphology in KCNV2-related "cone dystrophy with supernormal rod electroretinogram" (CDSR).
  
  
  METHODS
  Seven patients, aged 9 to 18 years at last visit, with characteristic full-field electroretinographic (ERG) features of CDSR were screened for mutations in the KCNV2 gene. All patients underwent detailed ophthalmological evaluation, which included distance and color vision testing, contrast sensitivity measurement, fundus photography, fundus autofluorescence (FAF) imaging, and spectral domain-optical coherence tomography (SD-OCT). Follow-up visits were available in six cases. Rod photoreceptor function was assessed using a bright white flash ERG protocol (240 cd·s/m(2)). Macular cone photoreceptor morphology was assessed from 2° by 2° zonal images obtained using adaptive optics scanning laser ophthalmoscopy (AOSLO) in six cases.
  
  
  RESULTS
  Pathogenic mutations in KCNV2 were identified in all seven cases. Best corrected vision was 20/125 or worse in all cases at the latest visit (20/125-20/400). Vision loss was progressive in two cases. Color vision and contrast sensitivity was abnormal in all cases. Retinal exam revealed minimal pigment epithelial changes at the fovea in four cases. A peri- or parafoveal ring of hyperfluorescence was the most common FAF abnormality noted (five cases). The SD-OCT showed outer retinal abnormalities in all cases. The rod photoreceptor maximal response was reduced but rod sensitivity was normal. AOSLO showed markedly reduced cone density in all six patients tested.
  
  
  CONCLUSIONS
  Central vision parameters progressively worsen in CDSR. Structural retinal and lipofuscin accumulation abnormalities are commonly present. Macular cone photoreceptor mosaic is markedly disrupted early in the disease.
authors.affiliation: Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, Toronto, Canada.
authors.forename: Ajoy
authors.initials: A
authors.lastname: Vincent
authors.forename: Tom
authors.initials: T
authors.lastname: Wright
authors.forename: Yaiza
authors.initials: Y
authors.lastname: Garcia-Sanchez
authors.forename: Marsha
authors.initials: M
authors.lastname: Kisilak
authors.forename: Melanie
authors.initials: M
authors.lastname: Campbell
authors.forename: Carol
authors.initials: C
authors.lastname: Westall
authors.forename: Elise
authors.initials: E
authors.lastname: Héon
mesh_terms: D000293:Adolescent; D002648:Child; D018388:Codon, Terminator / Q000235:genetics; D055253:Color Vision / Q000235:genetics; D015350:Contrast Sensitivity / Q000235:genetics; D018450:Disease Progression; D004596:Electroretinography; D005260:Female; D016368:Frameshift Mutation / Q000235:genetics; D006801:Humans; D008062:Lipofuscin / Q000378:metabolism; D008297:Male; D009030:Mosaicism; D010641:Phenotype; D010775:Photic Stimulation / Q000379:methods; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics*; D017949:Retinal Cone Photoreceptor Cells / Q000473:pathology / Q000502:physiology*; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology*; D012174:Retinitis Pigmentosa / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D041623:Tomography, Optical Coherence
chemical_list: D018388:Codon, Terminator; C489610:KCNV2 protein, human; D008062:Lipofuscin; D024642:Potassium Channels, Voltage-Gated