Evaluation of hyperacute effects of positive airway pressure therapy on microvascular circulation in patients with obstructive sleep apnea syndrome using optical coherence tomography - angiography (OCT-A)

Aim: This study aimed to evaluate the hyperacute (overnight) and acute (30-day) effects of Positive Airway Pressure (PAP) therapy on retinal microvascular structures using Optical Coherence Tomography Angiography (OCT-A) in patients diagnosed with Obstructive Sleep Apnea Syndrome (OSAS). Material and Method: Thirty-six patients diagnosed with moderate-to-severe OSAS (AHI > 15) and seventeen healthy/mild OSAS controls (AHI < 15) were included. Baseline OCT-A measurements (Visit 1) were performed for all participants. For the case group, additional measurements were taken after overnight PAP titration (Visit 2) and following one month of treatment (Visit 3). Vascular densities in the superficial (SCP) and deep capillary plexus (DCP), foveal avascular zone (FAZ), and optic disc parameters were analyzed. Results: No significant differences in OCT-A parameters were found between the case and control groups at baseline. Following overnight PAP use (Visit 2), a significant decrease was observed in DCP parafoveal (55,63 ± 3,7753,94 ± 3,73; p=0,025) and perifoveal (54,21 ± 4,98 -> 51,29 ± 4,93: p=0,031) vessel densities, whereas intrapapillary vascular density increased [50,9 (%25-75 CI: 48,62 – 53,9) -> 52,23 (%25-75 CI: 47,05 – 52,23 : (p=0,004)]. These hyperacute changes showed a positive correlation with apnea-hypopnea and REM-hypopnea indices. At the end of the first month, a significant increase in macular thickness was noted, while no significant differences were found in the FAZ area across visits. Conclusion: Our study is the first in the literature to demonstrate that PAP therapy has potent and dynamic effects on microcirculation starting from the very first day. A dynamic response was observed in retinal microvascular structures with overnight treatment, which returned to baseline values after 30 days. OCT-A emerges as a reliable and non-invasive tool for monitoring the vascular impacts of OSAS treatment.