PURPOSE: The prevalence of glaucoma in the US population above age 40 is estimated to be 1.9% The prevalence of glaucoma in patients with obstructive sleep apnea (OSA) is estimated at 27% and higher in Caucasians. OSA may be an important risk factor for glaucoma. Corneal hysteresis (CH) is a measure of viscous damping in the corneal tissue providing an estimate of the biomechanical properties of the cornea. Thinner central corneal thickness and CH is associated with glaucoma injury. We investigated CH in patients with OSA to assess if it was reduced. This may explain the association of OSA and glaucoma.
METHODS: Consecutive patients referred to sleep clinic were randomized in two groups with OSA (study) group and negative (control) group after their overnight polysomnogram. A comprehensive eye exam was conducted in all patients. Current enrollment is sixteen patients in control group and twenty in study group. Using the standard deviation of corneal hysteresis measurements of 1.85 mmHg (as determined by both pilot data and review of the literature) and two-sided alpha set at 0.05, a sample size of 25 subjects per group will provide 80% power to detect a difference in corneal hysteresis measurements of 1.5 mmHg between groups. A comparison of the corneal hysteresis between the control group and the study group were statistically analyzed using the two-sample t-test with double-sided alpha=0.05.
RESULTS: Mean age was 55.3 in study group and 47.5 in control (P= 0.049). Forty five percent were female in study group and 75% in control group (P=0.051). Mean BMI in study group was 39.8 and 30.8 in control group (P= 0.017). Corneal hysteresis (CH) was 11.0 in study and 11.4 in control group (P=0.57). There was no correlation of BMI or AHI with CH among all 36 subjects with Pearson correlation coefficient (r-squared) = 0.0001, p=0.94.
CONCLUSIONS: Preliminary analysis suggests lack of association of corneal hysteresis with obstructive sleep apnea.
CLINICAL IMPLICATIONS: Our study suggests that OSA does not impact biomechanical characteristics of cornea to explain glaucoma prevalence in OSA. Further research is required to elucidate the cause of glaucoma in OSA patients.
DISCLOSURE: Kenneth Mitchell: Grant monies (from sources other than industry): Unrestricted challenge grant funded by Research to Prevent Blindness to WVU
Anthony Realini: Grant monies (from sources other than industry): Unrestricted challenge grant funded by Research to Prevent Blindness to WVU
Hilda Curtis: Grant monies (from sources other than industry): Unrestricted challenge grant funded by Research to Prevent Blindness to WVU
The following authors have nothing to disclose: Sarah Hadique, Kim Yow, Shekhar Ghamande
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