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Kenneth B. Mitchell, Anthony Realini, Sarah Hadique, Brian McMillan; Corneal Hysteresis: The Link between Obstructive Sleep Apnea and Glaucoma?. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5113.
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In this study, we sought to determine if there was a difference in Corneal Hystereis in patients with Obstructive Sleep Apnea compared to controls.
This was a prospective clinical study. All patients referrred to a sleep clinic in a tertiary care center were invited to participate. Patients recruited provided informed consent and the study protocol was approved by the Institutional Review Board of West Virginia University.The patients were examined by the lead author. The exam included best corrected visual acuity, corneal pachymetry, Goldmann applanation tonometry, slit lamp exam and dilated fundus exam. Corneal Hysteresis (CH) was measured with the Ocular Response Analyzer (Reichert Technologies, DePew, New York).These patients then underwent a sleep study which included polysomnography (PSG) during which simultaneous electroencephalography (EEG), electromyography (EMG), electrocardiography (ECG), electro-oculography (EOG), pulse oximetry, oral and nasal airflow and thoracic and abdominal respiration by plethysmography. The Basal Metabolic Index (BMI) was calculated. The Apnea/Hypopnea Index (AHI) was used to assess severity of OSA using standard cut-off values. Based on the sleep study patients were classified into normal (control group) or Obstructive Sleep Apnea (study group).The results of the eye exam were not available to the sleep lab personnel and the results of the sleep studies were not available to the eye examiner.We estimated that a sample size of 22 subjects in each group was needed to provide 805 power to detect a 2 mm difference in CH between groups with alpha set at 0.05 and a standard deviation of 2.3 mm Hg for CH (based on our pilot data) in each group.
Over a 13 month period eye and sleep lab examinations were completed on 44 patients with 22 being placed in the OSA group and 22 in the control group. Patients in the study group had higher AHI (27.8+/-26.1 vs. 2.43+/-3.6) than the control group (p=0.0002). BMI was higher in the study group than in the control group (p= 0.004).Mean CH was 11.1+/-2,2 mm Hg in the study group and 11.6 +/-1.8 in the control group. This difference did not reach statistical significance. Mean CH was similar between gneders (p=0.38) in each group. CH did not correlate with age (r=0.21, p=0.16), BMI (r=0.05,p=0.33) or AHI (r=0.02,p=0.36).
1. There is no difference in CH in patients with OSA versus controls.2, Any bio-mechanical link between glaucoma and obstructive sleep apnea appears to be independent of CH.
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