Retention of central visual field in retinitis pigmentosa

According to Kanski, roughly one in four patients with retinitis pigmentosa retains visual acuity adequate for reading, although the electroretinogram may be extinguished and the visual field constricted to 2 to 3 degrees (whether diameter or radius is not stated). Under the age of 20 years, an acuity as poor as 6/60 is relatively uncommon, whereas over the age of 50 years such an acuity becomes common. Heckenlively comments that by the end of the 4th decade of life, most males with X-linked retinitis pigmentosa have vision reduced to hand motion or light perception. Women tend to be less severely affected than men: in a study by Bird, only 3 of 48 female heterozygotes had an acuity of less than 6/9, whereas only 8 of 28 hemizygous males had an acuity of 6/9 or better. I thought it would be instructive to analyze the visual field data for a female patient who, although she had suffered considerable loss of peripheral vision, is continuing to function visually quite well.