Cone dystrophies: clinical and electrophysiological findings

We analyzed the clinical and electrophysiological findings of 77 patients suffering from progressive cone or cone-rod dystrophies. The onset of symptoms was at the average age of 19.7 +/- 19.4 years. In some patients, the disease started within the 5th decade. The mean visual acuity was 0.19 +/- 0.2, while in 38%, the visual acuity was lower than 0.1. Color vision defects and visual field defects were found in most patients. The electrooculogram was recorded in 59 patients and was normal in only 19. On the electroretinogram (ERG), 60 patients had a reduction of the 30-Hz flicker amplitude and of the responses at maximum stimulus intensity when dark and light adapted. The ERG alterations showed a correlation to the visual field defects and to the reduction of the light rise on the electrooculogram. No correlation existed between the ERG amplitudes and visual acuity or color vision. Ophthalmoscopically, the posterior pole was normal in 25 patients. In the remaining patients, fundus changes ranged from mild pigment irregularities to severe pigment clumping. No correlation between fundus changes and functional findings existed.