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C.C. Grace, E.J. Higginbotham, S.D. Wadhwa; Hypoxia in Sleep Apnea Syndrome as a Risk Factor for Glaucoma . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4781.
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Previous investigators have linked normal tension glaucoma to sleep apnea and have considered the respiratory disturbance index (RDI) as the primary risk factor. We report 3 patients with advanced glaucoma who evidence not only severe RDI but also significant hypoxia, an important contributing factor to disease severity.
We reviewed the records of 3 normal tension glaucoma patients with sleep apnea syndrome (SAS) in the University of Maryland’s Glaucoma Service. The diagnosis of normal tension glaucoma was based on 1) average IOP of <21mmHg on diurnal testing, 2) visual field and optic nerve head changes characteristic of glaucomatous damage, 3) open angles, and 4) exclusion of secondary causes of optic neuropathy. Severity of glaucomatous optic neuropathy was documented based on Humphrey visual field results. Overnight polysomnography reports were obtained for each patient. Severity of sleep apnea based on respiratory disturbance index (RDI) was noted as well as degree and duration of oxygen desaturations below 90%.
Overnight polysomnogram showed RDI’s of 67.5 for patient 1, 44.1 for patient 2, and 38.0 for patient 3. A review of the detailed sleep study report showed an SaO2 nadir of 79% for patient 1, 61% for patient 2 and 63% for patient 3. The number of minutes spent below 90% in each patient was 81 minutes for patient 1, 50 minutes for patient 2, and 76 minutes for patient 3. All patients had severe and progressive glaucomatous damage on Humphrey 10–2 visual field testing prior to diagnosis and treatment of sleep apnea.
This review suggests that it is not only the presence of SAS that is a risk factor for glaucoma development but rather it may be the severity of desaturation and duration of hypoxia during sleep which may be the important factor. Our review suggests that the subgroup of sleep apnea patients who have very severe nocturnal hypoxia represent a high risk subset of SAS patients which may warrant routine ophthalmologic screening for glaucoma.
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