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

Purpose: To evaluate vascular changes on optical coherence tomography angiography (OCTA) in patients with diabetic macular ischemia (DMI) after systemic normobaric oxygen (NBO) therapy.

Methods: This before-after interventional studyincluded 26 eyes of 26 patients with DMI.Macular OCTA was performed before and after 1 hour of 100% NBO therapy at a flow of 10 L/min delivered by face mask. As primary outcomes, changes in OCTA metrics were evaluated using the paired t-test. Subgroup analyses were performed based on gender. The 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 $\pm$ 9.67 years. Overall, no significant change was observed in retinal thickness; however, there was a significant decrease in retinal thickness among females and a significant increase among males (P $<$ 0.001). The foveal avascular zone (FAZ) decreased significantly from 0.38 $\pm$ 0.14 to 0.34 $\pm$ 0.12 mm² (P = 0.035). Superficial capillary plexus vessel density (SCP-VD) and deep capillary plexus vessel density (DCP-VD) at fovea increased from 13.5 $\pm$ 6.37 to 14.98 $\pm$ 6.33% (P = 0.059) and from 24.61 $\pm$ 6.75 to 26.59 $\pm$ 6.16% (P = 0.022), respectively. In males, BCVA correlated significantly with baseline DCP parameters but corresponded with none of the SCP parameters. In females, BCVA significantly correlated with pre-O2 DCP-VD of the perifoveal inferior quadrant. Finally, regression analysis did not show any parameter that could predict a favorable response.

Conclusion: Using OCTA, we observed a decrease in FAZ and an increase in DCP-VD at fovea after short-term NBO therapy for patients with DMI.