OBJECTIVE : To investigate the correlation between obstructive sleep apnea (OSA) severity and the structural and functional progression in patients with glaucoma. METHODS : This retrospective comparative cohort study included subjects from the polysomnography database in Chang Gung Memorial Hospital between June 1, 2009, and June 1, 2017, by identifying patients who had received diagnoses of primary open-angle glaucoma (POAG), normal-tension glaucoma (NTG), or glaucoma suspect. Patients with follow-up time of <3 years and/or <3 consecutive reliable optical coherence tomography (OCT) or visual field (VF) tests were excluded. Progression of overall peripapillary retinal nerve fiber layer (RNFL) thickness on OCT scans and VF mean deviation (MD) or VF index (VFI) were determined through linear regression trend analysis. RESULTS : Thirty-two patients were included. There was a trend to higher percentage of progression on RNFL thickness and VF in higher OSAS severity. After stratifying patients to no OSA/mild OSA (group 1) and moderate/severe OSA (group 2), group 2 exhibited a significantly higher percentage of RNFL thickness progression than did group 1 (64.7% vs 26.7%, P = 0.042). Multivariate Cox regression analysis showed that severe OSA had an 8.448-fold higher risk of RNFL thickness progression after age, sex, diabetes mellitus, hypertension, hyperlipidemia, and body mass index adjustment (95% confidence interval, 1.464-48.752, P = 0.017). CONCLUSIONS : Severe OSA is significantly correlated with a higher risk of structural deterioration in patients with glaucoma.