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Marcus A. Bearse, Jr., Michal Laron, Kevin Bronson-Castain, Brian Wolff, Soffia Jonasdottir, Barbara King-Hooper, Shirin Barez, Anthony J. Adams; The Topographies of Local Neuroretinal Function and Retinopathy Are Not the Same in Adolescents with Diabetes. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2874.
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© ARVO (1962-2015); The Authors (2016-present)
To examine spatial relationships between neuroretinal function measured with the multifocal electroretinogram (mfERG) and nonproliferative diabetic retinopathy (NPDR) in adolescents with type 1 diabetes. We expected that neuroretinal function in areas with retinopathy would be worse than function in retinopathy-free areas.
50 deg fundus photographs from the right eyes of 126 adolescents with type 1 diabetes were screened for retinopathy. 17 eyes (13.5%) were determined to have NPDR. One eye was excluded due to widespread severe NPDR and macular edema, leaving 16 (age = 17.6 +/- 2.1 y; diabetes duration = 10.7 +/- 3.4 y; HbA1c = 9.2 +/- 1.4%). The implicit time (IT) and N1-P1 amplitude (Amp) of each of the 103 mfERGs from the central 45 deg were measured using the Hood & Li template scaling method, then converted to Z-scores based on 30 age-matched controls. Retinopathy (Ret) zones were constructed as the mfERG stimulus location containing a lesion and adjacent locations. Lesion-free (NoRet) zones were constructed from 3-7 contiguous stimulus locations. Neural function within each zone was quantified 6 ways by calculating the mean, maximum and minimum Z-scores for IT and Amp, and then computing an average for each of these within each eye. The average Ret and NoRet zone values were then compared across subjects using t-tests.
Differences between the Ret and NoRet zones were either not significant or, in one instance, marginally significant. The average IT Z-score differences between the Ret and NoRet zones were -0.02 (P>0.81), -0.12 (P>0.22), and 0.08 (P>0.22) for the mean, maximum and minimum measures, respectively. The average Amp Z-score differences between the Ret and NoRet zones were -0.12 (P>0.12), -0.23 (P=0.03), and 0.00 (P>0.95) for the mean, maximum and minimum measures, respectively.
The results suggest that the retinal topography of neural function in the adolescent type 1 diabetic retina is not similar to that of the clinical signs of NPDR. Only one of the six examined indices, the maximum (healthiest local) mfERG amplitude, was marginally worse in retinopathy versus retinopathy-free areas. These results appear to differ from those of adults with type 2 diabetes, and might be related to factors including the adolescents’ younger ages as well as the differences between type 1 and 2 diabetes.
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