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To our knowledge, this is the first time a study looking at the association between corneal hysteresis (CH) and obstructive sleep apnea syndrome (OSAS) severity has been reported. We provide evidence that CH is lower in OSAS and speculate on the possible causes.The present study aims to look at the association between CH and severity of OSAS, and whether CH could be another link between OSAS and the development of glaucoma.This was a cross-sectional, observational study at the University Malaya Medical Centre, Kuala Lumpur. Patients undergoing polysomnography for assessment of OSAS were recruited. We measured central corneal thickness (CCT) using optical biometry, and CH using ocular response analysis. Intraocular pressure (IOP) and Humphrey visual field (HVF) indices were also measured. The Apnea Hypopnea Index (AHI) divided patients into normal, mild, moderate, and severe OSAS categories. The normal and mild categories (47.9%) were then collectively called group 1, and the moderate and severe categories (52.1%) were called group 2. T tests, Pearson correlation tests, and general linear model analysis were performed, with P <.05 considered statistically significant.One eye each from 117 patients (75 men, 42 women) was included. Patients in group 2 had lower CH (9.8 ± 1.4 vs. 10.3 ± 1.1 mm Hg, P = .029), with unchanged estimated marginal means after correcting for age, sex, CCT, and IOP (P = .026). There were no statistically significant differences in IOP, CCT, or HVF indices between the two groups (all P > .05). CH correlated negatively with AHI (r = −0.229, P = .013) and positively with lowest oxygen saturation (r = 0.213, P = .022).CH is lower in moderate/severe OSAS than in normal/mild cases. This may be another link between OSAS and the development of glaucoma; further studies are indicated to determine the significance of this connection.