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R. W. Nelligan, C. Liang, W. T. Coleman, L. Srur; Nocturnal Variation of IOP Relative to Respiratory Disturbance Index in Patients With Suspected Sleep Apnea Syndrome. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4089.
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To determine whether nocturnal variation in IOP is related to respiratory disturbance index (RDI) in patients with suspected sleep apnea syndrome (SAS).
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.
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).
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.
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