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M. Gualtieri, F. M. Damico, A. L. Moura, R. D. Hamer, D. F. Ventura; Fast Adaptive Mechanisms in the Diabetic Retina Assessed From Mferg Recordings. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3258.
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© ARVO (1962-2015); The Authors (2016-present)
To assess interactions reflecting fast adaptive mechanisms, we analyzed synthesized 2-flash interactions extracted from mfERG responses and compared them with results from standard 1st and 2nd order kernel analyses in control subjects and in diabetic patients.
Monocular 103-element mfERG recordings (200 cd/m2, 60 Hz) were made in 70 subjects. A control group (n=14) was compared to a group of diabetics without (n=32) and a group with retinopathy (n=24). Single flash responses used for the 2-flash analysis were extracted from mfERG binary kernels series (up to 3rd order) using the VERIS software (EDI Inc.). The 2-flash interactions were measured via forward and backward effects (Gerth et al, IOVS, 2003). The forward effect is observed when the response to the 2nd flash of a 2-flash sequence is subtracted from the total response. The remaining waveform reflects the response to the 1st flash of the series plus its effect upon the 2nd flash. The backward effect is observed by subtracting the response to the 1st flash of the sequence. For each group of subjects, average N1, P1 and N2 latencies and amplitudes were calculated for each of 6 eccentricity rings, for all 4 analysis protocols (1st and 2nd order kernels, backward and forward effects). The overall slope of latency and amplitude data between fovea and 25o were measured for each group and each analysis protocol.
Latency and amplitude slopes from both patient groups were shallower than controls' for most components in all 4 protocols. Table 1 shows control/patient slope ratios for all conditions. The ratios for the 2-flash analysis were up to 7 times higher than those observed with the 1st and 2nd order kernels.
The use of 2-flash interactions was more effective in revealing differences between mfERG recordings from normal and diabetic retinas. Moreover, these results show that 2-flash sequences might be a useful approach to reveal effects that various diseases have upon fast adaptive retinal mechanism.
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