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S. K. Holfort, G. R. Jackson, M. Larsen; Dark Adaptation in Individuals With Type 2 Diabetes During Transient Hyperglycemia. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3326.
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© ARVO (1962-2015); The Authors (2016-present)
To examine dark-adapted retinal function in subjects with type 2 diabetes during transient hyperglycemia.
Twenty-four patients with type 2 diabetes and minimal diabetic retinopathy were randomized to undergo an oral glucose tolerance test (OGTT) or to remain fasting. Dark adaptometry was made in one eye, chosen at random, using a computer-automated dark adaptometer (AdapDx). Dark adaptation and capillary blood glucose was measured at baseline and 80 minutes into the OGTT/fasting test. Dark adaptometry was compared to a normative database. Subjects with type 2 diabetes were chosen because their glycemia increases drastically during the OGTT.
Fasting blood glucose remained stable in the fasting group, whereas it rose from 8.6 ± 2.1 to 21.1 ± 3.6 mM after 80 min in the OGTT group. Fasting dark adaptation was delayed in 13 of 24 patients. Hyperglycemic dark adaptation was accelerated compared to fasting dark adaptation (time to rod-cone break -30%; time to rod intercept -15%, rate of rod adaptation +39%). In the OGTT group dark adaptation normalized in 5 out of 5 patients during hyperglycemia.
Rod dark adaptation in subjects with type 2 diabetes accelerates during acute hyperglycemia, suggesting that rod function is limited by the supply of glucose. Rod dark adaptation normalized during hyperglycemia, suggesting that this aspect of rod function is normal at near the habitual non-fasting glycemia level of the diabetic.
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