Effects of continuous positive air pressure on intraocular pressure in patients with obstructive sleep apnea during the split-night study: An open-label randomized controlled trial

Intraocular pressure (IOP) is known to increase at midnight, when continuous positive airway pressure (CPAP) is initiated in split-night CPAP titration (SN-CPAP titration), in patients with obstructive sleep apnea (OSA); therefore, possible excessive increase in the IOP should be investigated. However, related studies on this topic are scarce. OSA causes increases and decreases in the IOP; however, its fluctuation during sleep remains unclear. Therefore, we determined the timing of these fluctuations in the IOP during sleep at night. METHODS: This study included 25 patients with OSA. A 7-hour period of night sleep was divided into first (Sleep-1) and second halves (Sleep-2). Patients were randomly divided into the SN (natural breathing during Sleep-1, CPAP applied during Sleep-2) and C (without CPAP) groups. IOP was measured using the iCare Pro before Sleep-1 and after Sleep-1 and Sleep-2. The main hypothesis was that IOP would be significantly higher in the SN group than in the C group. The sub-hypothesis was that the effects of OSA on IOP are manifested at different times. The correlation is shown as Pearson’s r for normally distributed data or Spearman’s rho for non-normally distributed data. The difference between the SN and C groups in the time course of IOP during the night’s sleep was analyzed using repeated-measures analysis of variance. A P value of <.05 was considered significant. RESULTS: No significant difference was found in IOP between the groups, but the SN group showed a significantly increased IOP during Sleep-2 (post hoc Bonferroni test). The apnea–hypopnea index inversely correlated with IOP changes in Sleep-1 and positively correlated with those in Sleep-2. CONCLUSION: This study does not support our main hypothesis that SN-CPAP titration promotes the effect of CPAP in increasing IOP. However, an expected range of the effect of increased CPAP on IOP has also been suggested. IOP-lowering and IOP-raising effects were predominant in the first and second halves of sleep in OSA, thereby providing a new perspective on measured IOP and supporting the subhypothesis.