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Megan Tillman, Athanasios Panorgias, Erich E Sutter, John S Werner; Age-related change in adaptation recovery of the full-field flash ERG. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5009.
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To quantify age-related change in adaptation recovery by extracting responses to multiple flashes from an m-sequence using full-field flash ERGs.
The flash ERG was recorded from and compared between normal younger (n=6, 22 ± 2 years, mean ± SD, range: 20-25 years) and older (n=5, 74 ± 10 years, range: 66-85 years) adults using an m-sequence flash stimulus. The flash intensities ranged from 0.0001 to 0.01 cd s/m2 under scotopic conditions and from 0.7 to 10 cd s/m2 under photopic conditions. The base intervals of the m-sequence for the scotopic and photopic stimulation were 65ms and 10ms, respectively. We obtained the complete binary kernel series from the responses to an m-sequence cycle. From the kernel series we derived the response to the adapting stimulus by itself and that of the adapting flash followed by a single flash response at different inter-stimulus intervals (ISIs). The adapting stimulus was a single flash under scotopic conditions and a double flash for the photopic conditions. Subtracting the response of the adapting flash from the responses to the following flashes, we isolated the contribution of the adapted flash and plotted its amplitude as a function of the ISI. We fitted a straight line through the linear portion of the recovery curve and used its slope as an estimate of the rate of recovery. We compared the rates of recovery between the younger and older groups.
The younger and older adults showed a linear response recovery as a function of inter-stimulus interval followed by saturation in both photopic and scotopic conditions. A statistically significant difference between the recovery slopes of the younger and older group was found with a two-way ANOVA for the scotopic condition (p<0.001, α=0.05), but no significant difference was found for the photopic condition (p=0.426, α=0.05).
The results of this study suggest significant reductions in the rate of recovery of fast adaptation mechanisms to a full-field flash under dark-adapted conditions but not under light-adapted conditions, consistent with reports that show the rod-dominated system to be more vulnerable in aging. M-sequence stimulation of the full-field flash ERG provides a rapid assessment of the retinal response dynamics. The use of rate of adaptation recovery as a means to distinguish normal, healthy eyes from those with retinal pathologies must still be explored.
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