Intracellular Edema and Subnormal Retinal Oxygenation Response: in Experimental Diabetic Retinopathy

Abstract

Abstract: : Purpose: To test the hypothesis that subnormal retinal oxygenation response (DPO₂) found early in the time course of experimental diabetic retinopathy is a consequence of intracellular edema. Methods: In control and 3 mo diabetic rats, retinal / choroidal (R/C) thickness was measured using high resolution MRI (23.4 υm² in–plane). In separate experiments with control rats R/C thickness, retinal oxygenation response to a carbogen provocation (ΔPO₂, mm Hg), and blood retinal barrier permeability surface area product (BRB PS, cm³/min) following Gd–DTPA (MW 590 Da) injection i.v. were measured using MRI prior to and / or 2 hours post i.p. injection of 15% body weight of saline (S) or distilled water (DW). Results: R/C thickness was not significantly different (P > 0.05) between control and diabetic rats, or between pre– and post– S injection, but was statistically increased (P 0.05) was found after either S or DW injection. However, post DW injection, retinal ΔPO₂ was subnormal (P < 0.05) relative to S injected rats. Conclusions: The present data do not support the working hypothesis but do demonstrate for the first time a strong link between increased R/C thickness following intracellular edema and subnormal ΔPO₂ without BRB damage.

Keywords: diabetic retinopathy • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retina