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F Eshraghi, DE Bourdeau, NL Lewis, G Dagnelie; Validated Electrophysiology Measures in Severe Vision Loss . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3812.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To establish vision measures allowing objective monitoring of visual function over time during Phase I experimental trials. Methods: Legally blind volunteers and normally sighted control subjects were enrolled in a repeated-measures study to determine the reproducibility of the single flash and flicker ERGs and VEPs using a dedicated protocol on a standard LKC UTAS 2000 system. VEP flicker rates were 10, 16, 20, and 31 Hz. ERG flicker rates were 20, 25, 31, and 38 Hz. Averaged data were analyzed through FFT. Visually impaired subjects were legally blind from RP (19), macular degeneration (7), other retinal degenerations (3), and optic nerve disease (2). Three subjects were normally-sighted. Several RP patients had light perception only in one eye. Two to four repeated measures of each test were performed. Results: At 20, 25, and 31 Hz, reproducible ERG responses, as judged by phase variability, could be recorded in one eye of one RP subject, and in both eyes of all other subjects. ERG amplitudes were reliable down to 100 nV. VEP responses could be recorded in all but 2 subjects, and were most reproducible for 10 Hz (1st and 2nd harmonic) and at the first harmonic of higher flicker rates. Amplitudes varied by up to 300%, especially in sub-microvolt ERG responses, but phases were generally reproducible within 45º. Conclusion: The reliability of phase information in most ERG and VEP flicker responses indicates the validity of these measures in research subjects with severe visual impairment. These tests can be used to monitor subjects during future safety and efficacy trials, particularly Phase I studies.
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