CONE-ROD DYSFUNCTION IN PATIENTS WITH UNEXPLAINED REDUCTION IN VISUAL-ACUITY

Electrophysiologic tests were performed in 233 patients who complained of reduced visual acuity with no satisfactory clinical explanation. T he functional integrity of the retina was assessed from the light- and dark-adapted electroretinogram. Macular function and conduction in th e optic nerves were estimated from the flash visual evoked potentials. Of the 233 patients 78 were grouped together on the basis of the elec trophysiologic and clinical findings. They were characterized by subno rmal electroretinogram responses with the cone system more affected th an the rod system. The flash visual evoked potential responses were of abnormal waveform and prolonged implicit times. Most of these patient s exhibited normal fundi. The reduction in visual acuity, the degree o f electroretinogram deficits and the pattern of the visual evoked pote ntial responses were similar in both eyes of each patient, indicating a symmetric disorder. Slight deterioration of visual acuity and electr ophysiologic variables were observed in 37 of the patients who were fo llowed up over a period of up to 8 years. The electrophysiologic findi ngs indicate that about 20% of patients complaining of unexplained red uction in visual acuity were suffering from a diffuse retinal disorder affecting the peripheral retina as well as the macular region. On the basis of electrophysiologic findings and clinical symptoms, we sugges t grouping these patients under a new entity: cone-rod dysfunction.