Effects of continuous positive air pressure on intraocular pressure in patients with obstructive sleep apnea during...

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.

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.

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.

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.