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M. A. Bearse, Jr., O. Davila, M. E. Schneck, A. J. Adams; Temporal Abnormalities of Retinal Processing in Diabetes. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5997.
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© ARVO (1962-2015); The Authors (2016-present)
To study temporal interactions in retinal regions of control and diabetic individuals by analyzing the first kernel and three second order kernel slices of the multifocal electroretinogram (mfERG).
We studied 25 healthy control subjects, 17 diabetic patients without retinopathy (NoRet group), and 15 patients with mild-to-moderate nonproliferative diabetic retinopathy (NPDR group). MfERGs were recorded in a 7.5 min session from 103 areas within the central 45 deg of one eye of each subject. The first order kernel (K1) and the first 3 slices of the second order kernel (K2.1, K2.2 and K2.3) were extracted. K1 represents the mean focal flash response. K2.1, K2.2 and K2.3 represent, respectively, temporal interactions induced by focal flashes over 13.3, 26.7 and 40 ms. To characterize the waveforms of the mfERG kernels, scalar product amplitudes (SPs) were computed within 5 retinal areas: the central ~15 deg and 4 surrounding quadrants. For each subject/location, log-SP-ratios were also calculated to normalize each second order kernel slice amplitude relative to K1. Abnormalities were defined as Z-scores <= -2.
Across the 5 retinal areas, SP abnormalities were most frequent for K2.1 in the NoRet group but were significantly more frequent and maximal at K2.2 for the NPDR group (P < 0.001), indicating the temporal profiles of abnormal interactions differed between the groups. Interestingly, in all 3 subject groups the temporal interactions decayed more rapidly in the peripheral retinal quadrants than in the central area. Analysis of the frequencies of abnormal log-SP-ratios confirmed that the decay of temporal interactions significantly differed among the three subject groups (P < 0.005). Similar results were obtained using RMS measures of kernel amplitudes, indicating that the findings are not restricted to SP measurements.
Temporal processing in the retina, as reflected in the time course of decay of mfERG temporal interactions, is abnormal in diabetes. The presence of mild-to-moderate nonproliferative diabetic retinopathy alters and exacerbates this. These abnormalities are likely to be related to the first order mfERG implicit time delays that are predictive of diabetic retinopathy development.
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