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M. A. Sandberg, B. Rosner, C. Weigel-DiFranco, T. L. McGee, T. P. Dryja, E. L. Berson; Disease Course of Patients With Autosomal Recessive Retinitis Pigmentosa Due to USH2A Gene Mutations. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2175.
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To measure the rates of visual acuity, visual field, and ERG loss in patients with autosomal recessive retinitis pigmentosa due to USH2A mutations and to determine if these rates differ from those of patients with dominant retinitis pigmentosa due to RHO mutations and patients with X-linked retinitis pigmentosa due to RPGR mutations.
We recorded Snellen visual acuities, Goldmann visual field areas (V4e white test light), and 30 Hz (cone) full-field ERG amplitudes spanning an average of 11.2 years in 120 patients with USH2A mutations. After censoring data to eliminate ceiling and floor effects, we used longitudinal regression to estimate mean rates of change and to compare these rates to those of previously studied cohorts with RHO mutations or RPGR mutations. We used survival analysis to compare the age distribution of legal blindness in these three groups. We also performed optical coherence tomography on selected patients with the common USH2A Glu767fs mutation to visualize changes in macular retinal structure associated with visual acuity reductions.
Mean annual exponential rates of decline for the patients with USH2A mutations were 3.2% for visual acuity, 7.1% for visual field area, and 13.0% for ERG amplitude; each of these rates was significantly different from zero (p < 0.001). The rate of visual acuity loss fell between the corresponding rates for the RHO and RPGR patients (1.6% and 4.0%, respectively), while the rates for visual field and ERG amplitude loss were each faster than those for the RHO and RPGR patients (2.9% and 4.7%, respectively, for visual field and 7.7% and 7.1%, respectively, for ERG amplitude). The median age of legal blindness for the patients with USH2A mutations (58 years) fell between that for the RPGR patients (44 years) and that for the RHO patients (72 years). Reductions in visual acuity in patients with the USH2A Glu767fs mutation were associated with a thinning of the outer nuclear layer in the foveola and, in one patient, with cysts.
Patients with autosomal recessive retinitis pigmentosa due to USH2A mutations lose visual field and cone ERG amplitude more rapidly than patients with dominant retinitis pigmentosa due to RHO mutations and patients with X-linked retinitis pigmentosa due to RPGR mutations, and they tend to become legally blind at age 58. Visual acuity loss in patients with USH2A mutations appears to reflect the same morphological changes seen in patients with other forms of retinitis pigmentosa.
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