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Editors Selection IGR 18-4
Sleep apneu syndrome: Sleep apneu syndrome and circadian IOP
Comment by Tony Realini on:
20790 Continuous positive airway pressure therapy is associated with an increase in intraocular pressure in obstructive sleep apnea, Kiekens S; Veva De Groot ; Coeckelbergh T et al., Investigative Ophthalmology and Visual Science, 2008; 49: 934-940
Obstructive sleep apnea (OSA) is more prevalent in subjects with POAG than in the general public, and POAG is more prevalent in subjects with OSA than in the general public. OSA is often treated by nocturnal administration of continuous positive airway pressure (CPAP). CPAP is known to raise in-traocular pressure (IOP). Kiekens et al. (311) have undertaken a study to determine the impact of CPAP on circadian IOP in a group of 21 subjects. All subjects were newly diagnosed with OSA and underwent 24-hour IOP and blood pressure both before and one month after initiation of CPAP. All measurements were taken in the supine position, and all subjects used CPAP through the nocturnal period of data collection at the second visit. Mean IOP at the pre-CPAP baseline was significantly higher in the nocturnal period compared to the diurnal period (although still in the normal range), as has been demonstrated even in normal subjects by other investigators. One month after beginning CPAP, mean nocturnal IOP was substantially higher than baseline mean nocturnal IOP (although still below 21 mmHg). The mean circadian IOP amplitude was 6.7 mmHg pre-CPAP and increased to 9.0 mmHg while on CPAP. Ophthalmic perfusion pressure (OPP) also decreased significantly during CPAP therapy. IOP dropped significantly within 30 minutes of stopping CPAP in the morning. These results confirm prior studies documenting elevated IOP with CPAP use, and quantify the magnitude of IOP elevation in the supine position in the nocturnal period. By raising intra-thoracic pressure, thus venous pressure, thus episcleral venous pressure, CPAP likely raises IOP by reducing aqueous outflow. CPAP-induced IOP elevation may explain the increased prevalence of POAG in subjects with OPA, and these subjects may warrant ongoing glaucoma screening. When established glaucoma patients require CPAP therapy, the clinician should be aware that the resulting IOP changes may not be detectable during office hours, and that these patients may be at risk for disease progression despite apparently well-controlled IOP as measured in the diurnal period.
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