Retinitis pigmentosa without pigment.

Sixty-eight consecutive patients with retinitis pigmentosa were studied to determine the frequency of the nonpigmented form of the disease. There was an overall incidence of 22%. Fifty percent of all cases had no characteristic pigmentation, if the duration of night vision difficulty was three years or less. The nonpigmented form of retinitis pigmentosa was frequently an early stage of the disease and not an unusual or atypical variant. Patients without the pigmentary changes characteristic of the disorder also showed less functional impairment: the electroretinographic b wave was more apt to be recordable, although impaired, and the rod threshold, as determined by dark adaptation measurement, was less elevated. The clinician should suspect retinitis pigmentosa, even in the absence of pigmentary changes, if there is a family history of the disorder, night blindness, peripheral field loss, and an impaired or nonrecordable electroretinographic response.