We aim to recruit 15 participants with OSA and POAG (Glaucoma group) and 15 participants with OSA and no Glaucoma (Control group). Patients with OSA and POAG will be recruited first and control participants matched for OSA severity subsequently. Matching will be performed according to 3 OSA categories: mild (AHI:5-15), moderate (AHI:15-30), severe (AHI>30)).