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Macular Oxygen Saturation and OCTA Metrics in Patients with and without Diabetes at Different Levels of Retinopathy
Published 2023 by Jennyffer Smith
Co-Author(s): Kelly Bisignano, Wendy Harrison
Program Number: 230088
Article Type: Scientific Program
PURPOSE:
Diabetic retinopathy (DR) results in neural and vascular dysregulation leading to vision loss. Changes in retinal oxygen saturation (O2S) are part of this pathway yet have not been evaluated regionally in the tissue around the macula. The purpose of this study is to evaluate measures of retinal O2S and vessel density (VD) within the macula and correlate these measures with foveal avascular zone (FAZ) size and diabetes (DM) health metrics. These results will be compared in controls and subjects with DM, both without retinopathy.
METHODS:
Sixty-five subjects (age 52.9 ± 10.2) were analyzed (26 controls, 25 DM without retinopathy (DMnR), and 14 DM with retinopathy (DMR). DMR was categorized as 3 mild, 7 moderate, and 3 severe nonproliferative DR, with 1 proliferative retinopathy (PDR). Medical health demographic data, HbA1c (Siemens Analyzer), and fundus photography were taken for all subjects to ensure accuracy of grouping. Retinal oximetry (Zilia) was performed within four quadrants adjacent to the FAZ within a 300um target. Optical coherence tomography angiography (OCTA) and FAZ analyses were completed (Zeiss) and corrected for refractive error. OCTA VD was obtained with Photoshop and ImageJ. O2S and OCTA were analyzed overall and by region with regression analyses. Differences in groups were found with corrected t-tests.
RESULTS:
O2S measures were significantly higher in DMR (57.4% ± 10.2) compared to the other groups (control 49.4% ± 8.1 and DMnR 48.7% ± 8.9), (P = 0.02). When evaluating the levels of retinopathy, the mild to moderate DMR subjects drove this effect with higher O2S values (62.32% ± 8.4), while lower O2S values were observed in the severe and PDR group (46.4 % ± 11.6). In addition, average OCTA density was significantly less in DMR compared to controls (p = 0.042), but not when compared to DMnR subjects (p = 0.07). FAZ size was not correlated with O2S or OCTA VD (p = 0.13 and p = 0.76, respectively). A significant inverse correlation was observed between averaged retinal O2S and OCTA measures after controlling for FAZ zone size (p = 0.041) for all subjects. Duration of DM was significantly associated with O2S (p = 0.01) and OCTA VD (p = 0.04). No relationship was found between OCTA and O2S within the local quadrants.
CONCLUSION:
This study was the first to evaluate macular O2S at different levels of retinopathy. It appears that when retinopathy develops O2S initially increases, however, in the late stages O2S drops in the tissue. In addition, this study found a relationship between O2S and OCTA VD after controlling for FAZ showing structure and function relationships are present. This technique may be useful to track patients with diabetes as they move through stages of retinopathy closer to treatment. Longitudinal studies are needed to see if reduced vessel density activates an increase in retinal O2S over time.
Diabetic retinopathy (DR) results in neural and vascular dysregulation leading to vision loss. Changes in retinal oxygen saturation (O2S) are part of this pathway yet have not been evaluated regionally in the tissue around the macula. The purpose of this study is to evaluate measures of retinal O2S and vessel density (VD) within the macula and correlate these measures with foveal avascular zone (FAZ) size and diabetes (DM) health metrics. These results will be compared in controls and subjects with DM, both without retinopathy.
METHODS:
Sixty-five subjects (age 52.9 ± 10.2) were analyzed (26 controls, 25 DM without retinopathy (DMnR), and 14 DM with retinopathy (DMR). DMR was categorized as 3 mild, 7 moderate, and 3 severe nonproliferative DR, with 1 proliferative retinopathy (PDR). Medical health demographic data, HbA1c (Siemens Analyzer), and fundus photography were taken for all subjects to ensure accuracy of grouping. Retinal oximetry (Zilia) was performed within four quadrants adjacent to the FAZ within a 300um target. Optical coherence tomography angiography (OCTA) and FAZ analyses were completed (Zeiss) and corrected for refractive error. OCTA VD was obtained with Photoshop and ImageJ. O2S and OCTA were analyzed overall and by region with regression analyses. Differences in groups were found with corrected t-tests.
RESULTS:
O2S measures were significantly higher in DMR (57.4% ± 10.2) compared to the other groups (control 49.4% ± 8.1 and DMnR 48.7% ± 8.9), (P = 0.02). When evaluating the levels of retinopathy, the mild to moderate DMR subjects drove this effect with higher O2S values (62.32% ± 8.4), while lower O2S values were observed in the severe and PDR group (46.4 % ± 11.6). In addition, average OCTA density was significantly less in DMR compared to controls (p = 0.042), but not when compared to DMnR subjects (p = 0.07). FAZ size was not correlated with O2S or OCTA VD (p = 0.13 and p = 0.76, respectively). A significant inverse correlation was observed between averaged retinal O2S and OCTA measures after controlling for FAZ zone size (p = 0.041) for all subjects. Duration of DM was significantly associated with O2S (p = 0.01) and OCTA VD (p = 0.04). No relationship was found between OCTA and O2S within the local quadrants.
CONCLUSION:
This study was the first to evaluate macular O2S at different levels of retinopathy. It appears that when retinopathy develops O2S initially increases, however, in the late stages O2S drops in the tissue. In addition, this study found a relationship between O2S and OCTA VD after controlling for FAZ showing structure and function relationships are present. This technique may be useful to track patients with diabetes as they move through stages of retinopathy closer to treatment. Longitudinal studies are needed to see if reduced vessel density activates an increase in retinal O2S over time.
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