Evaluation of macular retinal oximetry across different levels of diabetic retinopathy: a cross sectional study.

Abstract

Background: This study evaluates retinal oxygen saturation and vessel density within the macula and correlates these measures in controls and subjects with type 2 diabetes (DM) with (DMR) and without (DMnR) retinopathy. Changes in retinal oxygen saturation have not been evaluated regionally in diabetic patients.

Methods: Data from seventy subjects (28 controls, 26 DMnR, and 16 DMR were analyzed. For those with DMR,8 were mild/moderate diabetic retinopathy (NPDR) and 8 severe NPDR/proliferative (PDR). Subjects were categorized with glycosylated hemoglobin A1c and fundus photography. Retinal oximetry measurements were performed within a 300-400 μm region at four diagonal locations 3.1 degrees from the center of the fovea in the superior nasal, superior temporal, inferior nasal, and inferior temporal locations adjacent to the foveal avascular zone (FAZ). Optical coherence tomography angiography (OCTA) was performed and corrected for refractive error. Photoshop and ImageJ were utilized to calculate the superficial capillary plexus vascular density (SCP). Oximetry and OCTA vessel density were analyzed overall and by region.

Results: Average retinal oxygen saturation was highest in DMR (p = 0.008). Average OCTA density was less in DMR compared to controls (p = 0.01), but not compared to DMnR subjects (p = 0.07). A significant inverse correlation was observed between averaged oxygen saturation and SCP vascular density for all subjects (p = 0.02). Duration of DM was positively associated with oxygen saturation (p = 0.01) and negatively with OCTA SCP vascular density (p = 0.009). There were no differential effects of retinal location.

Conclusion: To our knowledge, this study is the first to evaluate the relationship between macular oxygen saturation and SCP vascular density at different levels of retinopathy. This may be useful to track patients with DM as they move through stages of retinopathy.