Abstract:  Objective To investigate the prevalence of obstructive sleep apnea (OSA) in patients with keratoconus (KC) and analyze the correlation between OSA and KC severity. Design Prospective case-control study. Participants 93 patients with KC who attended the 901 Hospital of the Joint Service Support Force of the Chinese PLA between January 1, 2020, and December 31, 2023, in addition to 97 age- and sex-matched control group participants without ophthalmological comorbidities, recruited during the same period. Methods All participants underwent polysomnography and ophthalmological examinations, and the following data were collected: height, weight, and apnea-hypoventilation index (AHI). The prevalence of OSA was compared between the two groups using the χ² test. Univariate and multivariateo Logistic regression analyses were used to identify potential risk factors associated with OSA. The severity of KC was classified according to the Amsler-Krumeich classification, and the differences between grades were compared. Main Outcome Measures Prevalence of OSA, odd katios (OR). Results In the KC group, 20 patients (20/93, 21.5%) were diagnosed with OSA, whereas only 5 patients (5/97, 5.2%) were diagnosed with OSA in the cohort without this diagnosis（χ²=11.109，P=0.001）. Univariate logistic regression analysis revealed that a higher BMI (OR: 1.707, 95% CI: 1.340~2.173) and a family history of OSA (OR: 5.750, 95% CI: 1.378~23.990) were significant risk factors for OSA development in patients with KC（all P＜0.05）. Among KC patients with OSA, the proportion of those with grade 3 and grade 4 was significantly higher than that of patients without OSA（χ²=6.735, P=0.009）. Conclusion The prevalence of concomitant OSA was markedly higher among individuals with KC than in the general population. Additionally, there was a notable correlation between KC severity and OSA incidence. 

Key words: Keratoconus, Obstructive sleep apnea, Polysomnography