Purpose:The aim of this study was to compare the frequency of occurrence of obesity and high risk of developing obstructive sleep apnea (OSA) in a keratoconus population with that of a control group.Methods:This prospective, case-controlled multicenter study was performed on patients with keratoconus and age- and gender-matched control subjects. One hundred forty-six patients were included in each group, and the Berlin Questionnaire was used for classifying patients as having a high risk or low risk of developing OSA. The patients' demographic and clinical characteristics were compared with the Mann-Whitney U test for continuous variables and with the (2) test for categorical variables.Results:The keratoconus (85 male/61 female) and control (79 male/67 female) groups' median ages were 25 (8-65) and 24 (9-60) years, respectively. Of the 146 patients in each group, 11 (7.5%) patients were determined to be at a high risk of developing OSA in the keratoconus group, and 8 (5.5%) patients were determined to be at a high risk of developing OSA in the control group. There was no significant difference between the groups (P = 0.477). The keratoconus and control groups' median body mass index values were found to be within normal ranges of 23.2 and 23.4, respectively.Conclusions:In this study, the mean body mass index value of the keratoconus group was determined to be within normal limits. In a Turkish population, the ratio of a high risk of developing OSA was not found to be significantly different between the keratoconus and control groups.