Reading performance in patients with retinitis pigmentosa: a study using the MNREAD charts

To evaluate the relationship between reading performance and severity of disease in patients with retinitis pigmentosa (RP), assessed with routine clinical psychophysical visual tests.

Seventy-six consecutive patients with RP (145 eyes), with reading acuity of at least 1.6 logMAR (logarithm of the minimum angle of resolution) in at least one eye, were examined. Each patient underwent a complete ophthalmic evaluation, including visual acuity (Early Treatment Diabetic Retinopathy Study [ETDRS] charts), contrast sensitivity (Pelli-Robson charts), visual field perimetry (Humphrey central 30-2 full-threshold program; Carl Zeiss Meditec, Dublin, CA), and a test of reading acuity, critical print size, and maximum reading speed (Minnesota Reading charts [MNREAD]).

Reading acuity was 1.0 logMAR or more in the better eye of all but six (92%) patients. Maximum reading speed was better than 100 words per minute in the better eye of 59 (78%) subjects. Moderate to severe reading impairment, defined as reading acuity of 0.4 logMAR or worse, was observed in the better eye of 47 (62%) patients. EDTRS visual acuity of 0.3 logMAR (20/40) or worse was 89% sensitive and 66% specific when used as a criterion to define reading impairment. Contrast sensitivity and visual acuity correlated significantly with all three reading components, whereas mean light sensitivity in the central visual field (6 degrees ) demonstrated a higher correlation with maximum reading speed. The number of years elapsed since the diagnosis of RP was a strong negative predictor of reading performance when clinical visual tests were taken into account, whereas a better reading ability characterized the patients with RP who had a higher level of education. A reduced reading speed with larger print size was found in 30 eyes (21%). This correlated with central light sensitivity, as it was more common among eyes with a mean sensitivity of <10 dB.

The reading performance of most patients with RP is only moderately impaired. It correlates with contrast sensitivity, visual acuity, and visual field. It should be assessed in all cases, as disability can ensue, even when visual acuity is preserved. In patients with RP with poor reading performance, there is little potential for high-magnification devices because visual field constriction affects the reading rate.