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K. R. Alexander, L. S. Kim, G. A. Fishman; Spontaneous Improvement in Rod System Function in Melanoma-Associated Retinopathy. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3673.
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Melanoma-associated retinopathy (MAR) is an infrequently occurring paraneoplastic retinopathy in which a malignant skin melanoma is accompanied by night blindness, as well as by characteristic ERG abnormalities of both the rod and cone systems. The purpose of this study was to document a spontaneous improvement in visual function within the rod system in a patient with the MAR syndrome.
Dark- and light-adapted ERG responses and dark-adapted psychophysical thresholds for 500-nm and 656-nm test stimuli were obtained in a male patient with the MAR syndrome during four evaluations spanning a period of 6.7 years. The patient's results were compared to those of visually normal control subjects.
By patient report, there was an improvement in night vision and a decrease in the severity of photopsias of the patient’s left eye between the initial and most recent testing sessions. Consistent with the subjective report, the b-wave amplitude of the dark-adapted, rod-isolated ERG of the patient’s left eye increased from 15.6 µV to 224 µV, and the dark-adapted maximal-flash b-wave amplitude increased from 128.9 µV to 460.9 µV between the initial and most recent testing sessions, with a corresponding increase in the amplitude of the oscillatory potentials. In addition, the dark-adapted thresholds of the patient’s left eye were rod-mediated and at the upper limit of normal at several peripheral retinal loci at the most recent testing session. In comparison, the cone ERG responses of the patient’s left eye showed a reduction in amplitude and the oscillatory potentials became delayed between the initial and most recent evaluations. The dark-adapted ERG responses of the patient’s right eye at the most recent testing session were similar to those of the left eye at the initial session, indicating that there was likely to have been little improvement in ERG rod system function in the right eye over this time period. Nevertheless, by psychophysical threshold testing, there was an overall improvement in rod sensitivity at peripheral retinal loci in the right eye between the initial and most recent testing sessions, although there was a marked asymmetry between the rod thresholds of the right and left eyes.
This is the first reported case of spontaneous improvement in electrophysiological and psychophysical rod function, as well as in subjective symptoms, in the MAR syndrome. The increase in rod system function suggests that other such patients have the potential to improve their rod visual function, even after a period of several years, if safe and effective treatments for the MAR syndrome were to become available.
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