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Like any vital organ, the eye receives its daily nutrition from blood circulation by a physiological force called perfusion pressure. Ocular perfusion pressure is set by local arterial pressure minus the resistance to perfusion. The resistance to perfusion is closely related to local venous pressure and intraocular pressure. Previous studies employing 24-hour ambulatory blood pressure monitor have indicated that nocturnal hypotension in systemic blood pressure is a significant risk factor for glaucoma. In this cross-sectional study of 26 Hispanic individuals with glaucomatous optic neuropathy and 67 Hispanic individuals with healthy eyes, the authors evaluated major parameters of 24-hour ambulatory blood pressure associated with glaucomatous optic neuropathy, as these subjects no recorded elevated office-hour intraocular pressure (< 22 mmHg). The authors concluded that the link between optic neuropathy and the extreme dipping status (> 20%) of systemic blood pressure at night from individual daytime level is much stronger than the links with other blood pressure parameters such as the nocturnal systolic and diastolic blood pressure levels. This new discovery affirms the concept that pathogenesis of open-angle glaucoma in regard to pressure forces in the eye should be evaluated individually for each patient instead of using an arbitrarily chosen number of simple or average pressure level within the 24-hour time period. Results from the current study also suggest that useful information may be obtained by studying the links between glaucomatous optic neuropathy and the parameters of 24-hour intraocular pressure. There are reports that a significant number of glaucoma patients with normal office-hour intraocular pressure actually show an elevation of intraocular pressure at night more than the average magnitude of increase in healthy persons.
Pathogenesis of open-angle glaucoma in regard to pressure forces in the eye should be evaluated individually for each patient instead of using an arbitrarily chosen number of simple or average pressure level within the 24-hour time periodTechnological advances in recent years have made monitoring 24-hour intraocular pressure possible under the ambulatory condition. A combination of 24-hour ambulatory monitoring blood pressure and intraocular pressure will probably provide even more insights for patients with unexplainable glaucomatous optic neuropathy.