Aim To report novel spectral domain optical coherence tomography (SD-OCT) findings and new mutational data in patients with ‘cone dystrophy with supernormal rod electroretinogram’, a recessive childhood onset retinal dystrophy consequent upon mutation in the KCNV2 gene.
Design/methods This was a comparative case series study of 12 patients with clinical and/or electrophysiological findings in keeping with KCNV2 mutation. Clinical examination and electrophysiological testing results were reviewed. Fundus photography and autofluorescence imaging were performed. Retinal layer appearance and thickness were evaluated using SD-OCT. The coding region and intron–exon boundaries of KCNV2 were screened by direct sequencing.
Results Mutations in KCNV2 were detected in all families; five of these changes were novel. Pattern electroretinograms were undetectable and full-field electroretinograms showed findings specific for the disorder. SD-OCT demonstrated bilateral morphological changes, usually confined to the fovea. Four foveal SD-OCT phenotypes were observed: (i) discontinuous inner and outer segment (IS/OS) junction reflectivity (6 patients), (ii) loss of IS/OS line and an optical gap in the foveola (2 patients); (iii) IS/OS junction disruption and profound foveal depth reduction, without optical gap and with preserved retinal pigment epithelium (RPE) complex (2 patients); and (iv) outer retina and RPE complex abnormalities (2 patients). Thinning of the neurosensory retina was observed in all eyes.
Conclusion In KCNV2 retinopathy foveal morphological changes are evident on SD-OCT even in the early stages of disease. However, there appears to be a window of opportunity, before marked structural damage has occurred, during which novel therapeutic intervention, such as gene replacement therapy, may rescue retinal function.
- cone dystrophy with supernormal rod ERG
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Funding The British Retinitis Pigmentosa Society, Fight for Sight, Moorfields Eye Hospital Special Trustees and the National Institute for Health Research UK provided the Biomedical Research Centre for Ophthalmology based at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, and The Foundation Fighting Blindness (USA) with funding for this study.
Competing interests None.
Ethics approval This study was conducted with the approval of the Moorfields and Whittington Hospitals Research Ethics Committee.
Provenance and peer review Not commissioned; externally peer reviewed.
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