Dark-adapted Perimetry Research Articles

Abnormal Rod Dark Adaptation in Autosomal Dominant Retinitis Pigmentosa With Proline-23-Histidine Rhodopsin Mutation

We studied rod and cone function in 13 patients from four families with autosomal dominant retinitis pigmentosa and the proline-23-histidine rhodopsin mutation. In patients with early stages of this disease, rod sensitivity was mildly abnormal throughout the retina and cone sensitivity was normal. In more severely affected patients, sensitivity loss varied with retinal region, some regions showing mild rod loss only and other regions having pronounced rod and cone dysfunction. Rhodopsin levels were decreased below normal by amounts that indicated the rod sensitivity loss was determined by the reduced ability to absorb light. The most characteristic abnormality of this genotype was a slowed rod branch of dark adaptation, which was present regardless of the extent or severity of disease. The time required for recovery of rod sensitivity was more than twice the normal time. These findings with dark-adapted perimetry, fundus reflectometry, and dark adaptometry showed intrafamilial and interfamilial consistency.

Relatively Enhanced S Cone Function in the Goldmann-Favre Syndrome

Using electrophysiologic and psychophysical tests that measure rod, midspectral, and S (blue) cone function, we studied four patients with the Goldmann-Favre syndrome, an autosomal recessive vitreoretinal degeneration. With spectral electroretinography, the predominant signal was from the S cones. With dark-adapted perimetry, all patients had severely reduced rod sensitivities and subnormal midspectral cone sensitivities. With S cone perimetry, the patients had normal or subnormal S cone function. Sensitivity differences between S and midspectral cones were significantly different from normal; there was relatively higher sensitivity to S cones compared to midspectral cones throughout the visual field. This relationship of dysfunctional cone mechanisms in the Goldmann-Favre syndrome is similar to that in the enhanced S cone syndrome, a recently identified retinal degeneration with S cone hypersensitivity. The results suggest that the Goldmann-Favre and the enhanced S cone syndromes are linked by a common pattern of retinal dysfunction.