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K. G. Locke, M. Klein, E. T. Filley, D. G. Birch; Interocular Comparisons of Progression Following Uniocular Fundus Photography and Full-Field ERG in Patients With Retinitis Pigmentosa (RP) Due to Rhodopsin Mutations. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3744.
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It is unknown whether the flash intensities used for fundus photographs and ERGs in the clinic are detrimental for patients with retinitis pigmentosa, especially those with rhodopsin mutations. There is heightened concern due to a recent report in a dog model with the rhodopsin Try4Arg mutation, where retinal damage was found after exposure to standard fundus photography (Cideciyan et al, PNAS 2005). Here we examine the long-term effect of light exposure in patients tested repeatedly in one eye only.
Affected family members from five dominant families with rhodopsin mutations [Asp190Asn (n=1), Pro23His (n=2), Cys185Arg (n=1), Leu46Arg (n=1)] were selected if they had been seen more than twice and exposed to high-intensity ERG flashes (up to 4.81 log scot td-s) and/or color fundus photography in one eye only. Visual fields, ERGs and fundus photos were obtained from both eyes to evaluate any asymmetry of visual function between the two eyes.
The standard combined response and light-adapted cone flicker of the eye followed over a period of 6-15 years in each patient showed a decline in amplitude consistent with the natural history of RP. At the final visit, the previously untested fellow eye demonstrated an amplitude loss equivalent to that of the previously tested eye and no difference was appreciated on the fundus photographs. A one-tailed Walsh test showed no interocular differences (p>0.062) in mean deviation of the visual field, combined ERG log amplitude or cone flicker log amplitude.
After evaluating patients with rhodopsin mutations, the functional measures of visual fields and ERGs provide no initial evidence that ERG testing and fundus photography exacerbate the retinal degeneration in these patients. However, caution is in order in extrapolating from these results since only a limited number of patients have been tested and none had the Try4Arg rhodopsin mutation found in the dog model.
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