Cone-rod dystrophy. Phenotypic diversity by retinal function testing.

Three patterns of visual dysfunction were identified in patients with autosomal recessive or simplex cone-rod dystrophy using rod and cone electroretinography and light- and dark-adapted static threshold perimetry. In the first pattern, there was a central rod and cone scotoma with eccentric fixation, mild peripheral retinal dysfunction equally affecting rod and cone systems, and slow progression. The second pattern, which was relatively more severe, also showed a central rod and cone scotoma and eccentric fixation; however, there was more cone than rod dysfunction detected by electroretinography, and function was lost in the peripheral visual field before it was lost in the midperipheral field. A third pattern, which was rapidly progressive, showed central unsteady fixation and no measurable cone function. Patches of rod function were retained in the central and inferotemporal regions of the visual field. Most of the patients studied fit within the three patterns and the patterns were consistent within families.