The prevalence of primary open-angle glaucoma (POAG) increases in obstructive sleep apnea syndrome (OSAS). OSAS could increase cerebrospinal fluid pressure (CSFP) and binocular papilledema. In this cross-sectional study, intraocular pressure (IOP), CSFP, mean deviation (MD), pattern standard deviation (PSD), optic disc indices, and retinal nerve fiber layer (RNFL) were compared among four groups with different extents of OSAS. Regression analysis was performed to correlate MD, PSD, and RNFL to polysomnography (PSG) index. For subgroups with severe OSAS, IOP and CSFP were compared. The prevalence of POAG was calculated. The severe OSAS had a significantly higher CSFP than the other three groups (p = 0.002, 0.036, and 0.017). Both moderate and severe groups showed significantly higher IOP than control group (p = 0.022 and 0.001). MD was correlated with average oxygen saturation (MSaO2) (p = 0.001). PSD was correlated with oxygen desaturation index (ODI) (p = 0.004). Significant differences were found in nasal RNFL and inferior RNFL among the four groups (p = 0.013, p = 0.004). Nasal RNFL correlated with the ODI (p = 0.048). For severe group, compared to normal RNFL group, CSFP was significantly lower in the thinned RNFL group (p = 0.039) and higher in the thickened RNFL group (p = 0.034). Totally, the prevalence of POAG was 5.49 %. OSAS had a high prevalence of POAG. Visual field was damaged and the RNFL was thinned. Due to diverse CSFP, RNFL changed differently in the patients with severe OSAS.