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ABSTRACT: PURPOSE: To report phenotypic characteristics including macular cone photoreceptor morphology in KCNV2-related cone dystrophy with supernormal rod electroretinogram (CDSR). Methods: Seven affected cases 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 cases 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 6 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° × 2° zonal images obtained using adaptive optics scanning laser ophthalmoscopy (AOSLO) in 6 cases. RESULTS: Pathogenic mutations in KCNV2 were identified in all 7 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 2 cases. Color vision and contrast sensitivity was abnormal in all cases. Retinal exam revealed minimal pigment epithelial changes at the fovea in 4 cases. A peri- or para-foveal ring of hyper-fluorescence was the most common FAF abnormality noted (5 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 6 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.
Investigative ophthalmology & visual science 12/2012; · 3.43 Impact Factor