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C Gerth, EE Sutter, JS Werner; The Impulse Response of the Aging Retina . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1772.
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Purpose: To determine age-related changes in amplitude and latency of the impulse response function (IRF) derived from multifocal electroretinogram (mfERG) at different retinal eccentricities. To compare these parameters with those of the psychophysically measured IRF using a two-pulse method (Shinomori & Werner 2001). Method: MfERG responses were recorded from one eye of 71 normal subjects (age 9-80 years) with the 7" stimulus-refractor unit (EDI) and VERIS ScienceTM 4.3 using the following protocol: bipolar contact lens, m-sequence =14, 103 hexagons, luminance 200 cd . m-2 (white) and < 1.0 cd . m-2 (black), pupils ≷ 6 mm, amplification 105, filter cut-offs at 10 and 300 Hz. Single flash IRFs were derived (VERIS ScienceTM 5.0) for (A) 3 retinal areas (central 5 deg, 5 to 15 deg and 15 to 25 deg in radius) and (B) the parafoveal area (5 to 10 deg in radius) for comparison with psychophysical data. Implicit times N1 and P1 and response densities N1+P1 (peak to trough) were analyzed for the response to a single focal flash synthesized from the binary kernels. Results: Age-related decreases in response density log N1+ P1 were found in all analyzed retinal areas (A and B). The age-related decrease in log N1 + P1 was significantly greater for the central 5 deg compared to 15-25 deg. A significant increase in implicit time with age was found for log N1 in all areas except in the central 5 deg, and for log P1 in the outermost area (15 to 25 deg) only. The rate of change with age in log N1 and log P1 was not significantly different for the 3 retinal areas. In the parafoveal area, (B), we found significant changes in latency (N1 only), although the fractional changes were greater for response density than latency. Conclusion: Age related changes of the retinal impulse response parallel those of the psychophysical IRF that demonstrate greater changes in response density or amplitude compared to the changes in latency. Age-related changes in latencies of the IRF synthesized from the kernel series are smaller than those observed in the first-order kernel alone. This suggests that fast adaptive mechanisms whose effects are predominantly reflected in the higher order kernels may be most sensitive to aging. Shinomori, K. & Werner, J.S. Proceedings of First Asian Conference on Vision, 2001.
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