Abstract
Purpose: :
To determine whether nocturnal variation in IOP is related to respiratory disturbance index (RDI) in patients with suspected sleep apnea syndrome (SAS).
Methods: :
Patients undergoing polysomnographic evaluation for SAS (n=26) at LSUHSC-Shreveport had multiple IOP measurements over a 12 hour nighttime period with a Medtronic Tono-penXL applanation tonometer. All measurements were taken at a sleep lab in the supine position. IOP was measured at least 5 times per patient throughout the night, with 2-3 readings per measurement. 5 patients were excluded for inadequate number of measurements, and 1 patient was excluded for having a divided study (1/2 night on room air, 1/2 night on CPAP). RDI was defined as the number of apneas, hypopneas, and arousal events divided by the total hours of sleep. Statistical analysis was performed using a T-test to rule out differences between the right and left eyes. The Pearson Correlation Coefficient was then calculated for median IOP and RDI.
Results: :
No statistical difference was found for IOP measurements between right and left eye (average OD 7.1± 2.9mmHg, average OS 7.1± 4.4mmHg). There was a negative correlation between range of IOP and RDI that was not statistically significant (r=-0.29, p>0.05). There was a negative correlation between range of IOP and number of apneic events that was not statistically significant (r=-0.26, p>0.05). There was a no correlation between range of IOP and number of hyponeic events (r=0.001). There was a no correlation between maximum IOP and RDI (r=0.012).
Conclusions: :
Preliminary data appears to show a trend towards negative correlation between risk factors of glaucoma and SAS, but is not statistically significant. This disagrees with some earlier studies that had suggested SAS as a risk factor for glaucoma. The design of the study allowed only correlation to be studied, and there may be other factors outside of IOP fluctuation that lead to SAS being a risk factor for glaucoma. Statistical significance may be reached with continuation of the study with an increase in the number of subjects.
Keywords: intraocular pressure • clinical (human) or epidemiologic studies: risk factor assessment