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J. S. Ng, M. A. Bearse, Jr., M. E. Schneck, A. J. Adams; Longitudinal Evaluation of Multifocal Electroretinogram Measures in Diabetic Patients Without Retinopathy. Invest. Ophthalmol. Vis. Sci. 2008;49(13):6098.
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© ARVO (1962-2015); The Authors (2016-present)
Increases in multifocal electroretinogram (mfERG) implicit time (delays), but not mfERG amplitude measures, are predictive of local retinopathy development over 1-3 years. Here we examine longitudinally these measures in diabetic patients without retinopathy.
One eye each of 6 diabetic patients was examined at 5 annual visits. The mean+/-SD age, duration of diabetes, and blood glucose level at baseline were 50.2+/-7.4 yrs, 5.3+/-3.8 yrs, and 161+/-93 mg/dL, respectively. Ophthalmic examinations, including 50 degree fundus photographs and mfERG testing, were performed at each visit. MfERGs were recorded using VERIS 4 (103 elements covering the central 45 deg, dilated pupils, and 10-100 Hz filtering). First-order mfERG P1 implicit time (IT) and N1-P1 amplitude (AMP) were derived. For each subject, IT and AMP measures were averaged across all retinal locations. Z-scores for IT and AMP were calculated based on data from 30 age-similar control subjects. One-way repeated measures ANOVA (incorporating the Huynh-Feldt correction) was used to investigate significant changes in IT and AMP over the 5 visits. T-tests, corrected for multiple comparisons, were used to compare diabetics to controls.
All subjects remained retinopathy free during the study. The mean+/-SD IT Z-scores were -0.01+/-0.24, 0.38+/-0.22, 0.23+/-0.21, 0.30+/-0.20, and -0.12+/-0.20 at the 1, 2, 3, 4, and 5 year time points, respectively. The mean+/-SD AMP Z-scores were -0.15+/-0.12, -0.68+/-0.15, -1.26+/-0.20, -1.09+/-0.16, -1.23+/-0.18 at the 1, 2, 3, 4, and 5 year time points, respectively. ANOVA analysis showed no differences in IT Z-scores over the 5 visits (p = 0.25), whereas a marginal difference was found for AMP Z-scores (p=0.04). The overall mfERG ITs were never different from controls (p > 0.01) during the study, while the mfERG AMPs were lower compared to controls at the third, fourth, and fifth visits (p < 0.01).
A small group of diabetic patients that maintained normal, stable multifocal electroretinogram implicit times over 5 years did not develop retinopathy. This result is consistent with our predictive models (Bearse et. al., 2006). In contrast, decreases in amplitude were observed in these eyes, supporting our earlier findings that decreased amplitudes are not predictive of retinopathy development.
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