Purpose: To determine the prevalence of obstructive sleep apnea (OSA) in patients with keratoconus (KCN) and to evaluate the association between the severity of KCN and OSA.

Methods: OSA was diagnosed with an overnight home sleep apnea test. As estimated by home monitoring, an apnea–hypopnea index threshold of ≥5 sleep-related obstructive breathing events per hour was considered suggestive of OSA. For grading KCN severity (Amsler–Krumeich classification), slit-lamp biomicroscopy, corneal topography, and pachymetry measurements were performed. Preoperative measurements were included in the analysis for patients who had undergone surgery for KCN.

Results: The study sample consisted of 50 consecutively enrolled patients: 33 men; mean age ± SD 43.6 ± 11.8 years; body mass index 29.7 ± 7.3 kg/m²; and neck circumference 40.0 ± 3.4 cm. The overall prevalence of OSA was 38% (6 women and 13 men). Patients with OSA were older (49.8 ± 9.3 vs. 37.5 ± 10.8 years; P < 0.01) and had a higher body mass index (34.7 ± 8.1 vs. 26.2 ± 4.8 kg/m²; P <0.01), neck circumference (41.2 ± 2.6 vs. 38.7 ± 3.6 cm; P < 0.01), and cylinder diopter (5.98 ± 1.94 vs. 4.05 ± 3.55 D; P = 0.045) compared with those without OSA. No significant association was found between OSA severity and ocular parameters and KCN grade.

Conclusions: As measured by overnight home sleep apnea testing, OSA was 10 to 20 times more prevalent among patients with KCN than the rate reported for the general population. The rate lies between the prevalence estimated from sleep study data of self-reported diagnosis of OSA and the risk of developing OSA as determined by the Berlin Questionnaire.