Optical Coherence Tomography Angiography Changes in Diabetic Macular Ischemia after Systemic Normobaric Oxygen Therapy

Purpose: To evaluate vascular changes in patients with diabetic macular ischemia (DMI) after systemic oxygen therapy using Optical coherence tomography angiography (OCTA). Methods: This interventional before-after study included 26 eyes of 26 patients with DMI. Macular OCTA was performed before and after 1 hour of 100% oxygen therapy at a flow of 10 L/min by face mask. Changes in OCTA metrics were evaluated by paired t-test. Subgroup analyses were performed based on gender. Secondary outcomes included identifying parameters correlated with best-corrected visual acuity (BCVA) and factors associated with improvement in OCTA parameters. Results: The patients included 15 males and 11 females aged 59.48 ± 9.67 years. Overall, no significant change was observed in retinal thickness, however, there was a significant decrease in females and a significant increase in males. (Both P<0.001) Foveal avascular zone (FAZ) decreased significantly from 0.38 ± 0.14 to 0.34 ± 0.12 mm ² . (P=0.035) Superficial capillary plexus vessel density (SCP VD) at fovea increased from 13.5 ± 6.37 to 14.98 ± 6.33 %. (P=0.059) Deep capillary plexus vessel density (DCP VD) at fovea increased from 24.61 ± 6.75 to 26.59 ± 6.16 %. (P=0.022) In males, BCVA correlated significantly with DCP parameters but none of SCP parameters. In females, BCVA showed significant correlation only with pre-O2 perifoveal inferior quadrant. Regression analysis failed to show any parameter predicting a favorable response. Conclusion: This study showed beneficial effects of oxygen therapy for DMI by decreasing FAZ area and increasing DCP VD at fovea using OCTA.