Progressive human cone-rod dysfunction (dystrophy).

The author has classified progressive human cone-rod dysfunction into primary and secondary types. The primary type, identified by early ERG cone and usually also rod abnormalities, was further subdivided into types 1 and 2 based on, amoung other distinguishing characteristics, the extent of associated retinal pigment epithelial defects. Secondary cone-rod dysfunction apparently results from disease initially affecting the retinal pigment epithelium. Initially normal ERG findings and the presence of flecks characterize this (type 3) progressive cone-rod dysfunction.