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M. A. Bearse, Jr., K. Dhamdhere, W. W. Harrison, K. Bronson-Castain, S. Barez, M. E. Schneck, A. J. Adams; Local Relationships Between Retinal Thickness and Functional Changes in Diabetes. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5070.
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© ARVO (1962-2015); The Authors (2016-present)
To study the local relationships between retinal thickness assessed by optical coherence tomography (OCT) and retinal function measured with multifocal electroretinography (mfERG) in adult patients with diabetes (DM) and no retinopathy.
We studied 36 patients with no retinopathy (9 with type 1 DM; 27 with type 2 DM; mean age = 50.0 +/- 11.8 yrs) and 29 healthy control subjects (47.0 +/- 12.8 yrs). The central 20 deg of one eye of each subject was examined. The amplitude (AMP) and P1 implicit time (IT) of each of the central 37 first order mfERGs were derived using a template scaling method (Hood & Li, 1997). These were compared to spatially corresponding retinal thickness measurements (Stratus OCT 3). To account for variation with eccentricity, retinal thickness was converted to percentile rank, and AMP and IT were converted to Z-scores based on control data. Local abnormalities were defined as P-values <= 0.023. Retinal thickness was compared to AMP and IT using Chi-square analyses to determine whether structure and function were locally associated.
IT was positively associated with retinal thickness in the type 1 group (P<0.001) and marginally in the type 2 group (P=0.025), but not in the control group (P>0.05). AMP was positively associated with retinal thickness in the type 1 group (P<0.001) and the control group (P<0.005) but not in the type 2 group (P>0.05). As expected, the type 1 and type 2 groups had more abnormal locations than the control group. IT abnormalities were not spatially associated with retinal thickness abnormalities in any subject group (P>0.05). Abnormally thin retinal locations were associated with abnormally small AMP (P=0.012) in the type 2 group but not in the other subject groups.
Relationships between local retinal thickness measured with OCT and function assessed with mfERG are complex. For example, although longer mfERG implicit times are associated with retinal thickening in diabetes, there is not a significant spatial agreement between the two measurements in their classification of abnormalities. In addition, the associations are not necessarily monotonic, especially in type 2 diabetes.
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