To determine the severity of visual acuity impairment in patients, age 45 years or older, with either isolated or identifiable genetic subtypes of retinitis pigmentosa (RP) and Usher syndrome. Multicenter, retrospective, cross-sectional analysis. Visual acuity data were obtained on 999 patients with different genetic subtypes of RP and Usher syndrome, age 45 years or older, from 4 major eye care centers in the United States. The best-corrected visual acuity obtained on these patients from the eye with better vision on their most recent visit was used for the analysis. Best-corrected visual acuity was the main parameter analyzed for the study, and it was obtained with Snellen or Feinbloom low vision charts or with a B-VAT II monitor (Mentor). The final analyses were done on 982 patients (17 patients with a sector form of RP were analyzed separately). Of the 982 patients, 506 (52%) had a visual acuity of 20/40 or better, and 678 (69%) had a visual acuity of 20/70 or better in at least one eye. There were 243 (25%) patients who had a visual acuity of 20/200 or worse in both eyes. Five (0.5%) patients had no light perception in both eyes. The odds ratio for any patient having a visual acuity of 20/200 or worse in this population was 1.4 for each difference of 10 years of age. Similarly, the odds ratio of a patient having a visual acuity of 20/40 or better in at least one eye was 0.95 for a 10-year age difference. In this large population of patients with RP and Usher syndrome from four centers, it was rare for such patients to lose all vision in both eyes. One fourth of the patients had a visual acuity of 20/200 or worse in both eyes, and more than half of the population had a visual acuity of 20/40 or better in at least one eye. These data can be used to counsel such patients on the extent of potential visual acuity impairment from their disease.