Frequent loss of nyctohemeral rhythm of intraocular pressure restored by nCPAP treatment in patients with severe apnea.

OBJECTIVE To assess 24-hour intraocular pressure (IOP) and ocular perfusion pressure rhythms in newly diagnosed apneic patients before and after nasal continuous positive airway pressure (nCPAP) treatment. METHODS Intraocular pressure (using a Tonopen XL) and ambulatory blood pressure, measured hourly for 24 hours, were analyzed in 18 consecutive patients with obstructive sleep apnea for nyctohemeral rhythmicity (cosinor model). Twelve of 18 patients were reassessed after nCPAP use. RESULTS Before treatment, 28% of the patients with obstructive sleep apnea demonstrated a nocturnal acrophase, 22% a diurnal acrophase, and 50% absence of 24-hour rhythm of IOP. The ocular perfusion pressure rhythm was nocturnal in 78% of cases and absent in 22%. Using nCPAP, the mean (standard error of the mean) nocturnal IOP increased from 14.8 (0.8) to 18.3 (1.2) mm Hg (P < .03). Among patients with initial abnormal IOP rhythm (ie, rhythm with diurnal acrophase or absence of rhythm), 67% shifted to a normal 24-hour IOP profile after treatment. CONCLUSIONS Normal IOP nyctohemeral rhythm is lost in most patients with severe apnea. Nasal continuous positive airway pressure use restored a normal 24-hour IOP profile in most cases.