CONE AND ROD FUNCTION IN CONE DEGENERATIONS

Progressive cone dystrophy (CD) is usually marked in the initial stage s by reduced visual acuity, color vision deficiency and alterations in the photopic electroretinogram, while morphological alterations can b e very mild; in some forms rods are affected in a later stage as well. We examined 40 patients with progressive cone dystrophy to determine the extent of functional losses in the cone system with psychophysical tests, A great variety of visual acuity and fundus alterations was fo und, Myopia was present in 74% of the patients, An autosomal dominant pattern of inheritance predominated (32%), No prevalence of gender was found, The age of onset ranged between 10 and 30 yr, All patients had progression of their symptoms, The total error score in color arrange ment tests, the saturated Farnsworth Panel D-15 and the Farnsworth-Mun sell 100-hue test, was pathologic with a predominance of confusions al ong the tritan and scotopic axis, Especially if visual acuity was belo w 0.5, color vision defects increased, but color vision defects were a lso found in patients with normal visual acuity, A general decrease of sensitivity in all three cone mechanisms was observed in measurements of spectral sensitivity, Moreover, cone-cone interaction as tested by transient tritanopia measurements was usually disturbed, In the dark adaptation function the threshold of the cone branch was usually eleva ted, These tests provide a good means to ascertain the correct diagnos is in early stages of the disease and to monitor progression in patien ts suffering from cone dystrophy. (C) 1997 Elsevier Science Ltd.