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Based on best-corrected visual acuity survival probabilities, the intervention window for gene therapy for RPGR-associated retinal dystrophies is relatively broad in patients with RP. RPGR-ORF15 mutations were associated with COD/CORD and with a more severe phenotype in RP. High myopia is a risk factor for faster best-corrected visual acuity decline.

Purpose: To describe the phenotype, long-term clinical course, clinical variability, and genotype of patients with CRB1-associated retinal dystrophies.Design: Retrospective cohort study. Participants: Fifty-five patients with CRB1-associated retinal dystrophies from 16 families. Methods: A medical record review of 55 patients for age at onset, medical history, initial symptoms, bestcorrected visual acuity, ophthalmoscopy, fundus photography, full-field electroretinography (ffERG), Goldmann visual fields (VFs), and spectral-domain optical coherence tomography.Main Outcome Measures: Age at onset, visual acuity survival time, visual acuity decline rate, and electroretinography and imaging findings.Results: A retinitis pigmentosa (RP) phenotype was present in 50 patients, 34 of whom were from a Dutch genetic isolate (GI), and 5 patients had a Leber congenital amaurosis phenotype. The mean follow-up time was 15.4 years (range, 0e55.5 years). For the RP patients, the median age at symptom onset was 4.0 years. In the RP group, median ages for reaching low vision, severe visual impairment, and blindness were 18, 32, and 44 years, respectively, with a visual acuity decline rate of 0.03 logarithm of the minimum angle of resolution per year. The presence of a truncating mutation did not alter the annual decline rate significantly (P ¼ 0.75). Asymmetry in visual acuity was found in 31% of patients. The annual VF decline rate was 5% in patients from the genetic isolate, which was significantly faster than in non-GI patients (P < 0.05). Full-field electroretinography responses were extinguished in 50% of patients, were pathologically attenuated without a documented rod or cone predominance in 30% of patients, and showed a rodecone dysfunction pattern in 20% of RP patients. Cystoid fluid collections in the macula were found in 50% of RP patients.Conclusions: Mutations in the CRB1 gene are associated with a spectrum of progressive retinal degeneration. Visual acuity survival analyses indicate that the optimal intervention window for subretinal gene therapy is within the first 2 to 3 decades of life. Ophthalmology 2017;124:884-895 ª 2017 by the American Academy of Ophthalmology Supplemental material available at www.aaojournal.org.Mutations in the CRB1 gene are associated with a wide variety of severe retinal dystrophies with variable phenotypes, including panretinal dystrophies such as retinitis pigmentosa (RP), Leber congenital amaurosis (LCA), and coneerod dystrophy, as well as central phenotypes such as isolated macular dystrophy and foveal retinoschisis. Retinitis pigmentosa is a clinically and genetically heterogeneous disorder. Mutations in the CRB1 gene have been associated with RP12, a distinct form of RP characterized by preservation of para-arteriolar retinal pigment epithelium, progressive visual field (VF) loss starting from the first decade of life, and early macular involvement. 4 Other common features are hyperopia and optic disc drusen, previously described in a Dutch genetic isolate (GI). 5Classic forms of earl...

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