Autosomal dominant retinitis pigmentosa: a log quotient analysis of the photopic and scotopic b-wave amplitude

Low-noise electroretinogram recording techniques in retinitis pigmentosa

The achievement of a sharp retinal signal depends on many factors, particularly the stability of the electrodes on the corneal surface, the maximal reduction of electrical and electromagnetic disturbances and the avoidance of the noise caused by events that are synchronous with the stimulation. The availability of a low-noise recording system becomes critical in the detection of the electroretinogram in patients with retinitis pigmentosa. We studied an electroretinographic recording technique specifically designed to enhance the signal-to-noise ratio in patients with retinitis pigmentosa. The main features of the method are a membrane suction pump connected to the corneal electrodes to improve contact lens stability on the corneal surface, and a differential derivation system to record the signal. One corneal electrode is used as the recording electrode, while the other, acting as the reference electrode, is covered during full-field ganzfeld stimulation. In addition, computerized averaging and signal postrecording analyses were performed on 100 iterations. The methods described here resulted in a sharp reduction in the number of undetectable electroretinograms in our case material (28.8%). This investigation demonstrates that some of the undetectable signals reported in the literature may be due to noisy recording methods rather than to actually extinguished retinal responses.

Electroretinographic studies of families with dominant retinitis pigmentosa

Full-field electroretinograms were recorded from four different families with dominant retinitis pigmentosa. Two different types of the disease were recognizable and consistent within each pedigree, one with normal cone b-wave implicit times (one pedigree) and the other with prolonged cone b-wave implicit times (three pedigrees). The cone b-wave amplitude was found to decrease with age, but the implicit time did not, suggesting that the amplitude is useful for monitoring the progression of the disease whereas the implicit time seems more suitable for distinguishing different types of the disease. The progression rate was analyzed in a large pedigree, spanning six generations, three of which were examined in detail. The recently described Pro23His gene was not detected in the families.