Visual loss in retinitis pigmentosa.

I investigated the visual histories of 91 consecutive patients with retinitis pigmentosa to determine when, and how fast, visual acuity was affected by the disease. The results from recessive cases showed that visual loss may occur at any age in retinitis pigmentosa, and typically progresses from 6/12 (20/40) to 6/60 (20/200) in about six years. At any given time, most of the patients had either good or poor visual acuity; intermediate levels of visual acuity appeared to be unstable. Before age 20 years, 60 to 90% of the patients had a visual acuity of 6/12 (20/40) or better, and few had a visual acuity of 6/60 (20/200) or worse. By age 50 years, 25% of the patients still retained good visual acuity, but more than 50% had visual acuity of 6/60 (20/200) or worse.