Who’s at risk? Reviewing factors for glaucoma onset

San Francisco-As ophthalmologists, it is imperative to review the potential risk factors for glaucoma and what the medical community knows about them, noted Shan C. Lin, MD, a member of the ophthalmology department at the University of California San Francisco School of Medicine.

During the Glaucoma 360 CME Symposium, Dr. Lin’s review of the list of risk factors for the disease included cerebrospinal fluid (CSF) pressure, myopia, sleep apnea, low blood pressure, pro-oxidants intake of calcium and iron, and birth control pill use.  

Dr. Lin cited the prospective Beijing study of patients (average age: 40 to 49 years), all of whom underwent lumbar puncture for the CSF sample.  The researchers found a heightened transluminal pressure was related to high CSF pressure. While no treatment exists for high CSF pressure, the ophthalmologist should note this fact in a glaucoma patient. 

Myopia can occur in many individuals who are unaware they have this condition.  One 1999 Taiwan study found 16% of students in a school system had undetected myopia. In the Australian Blue Mountain Eye Study, myopia was a two-fold risk factor for glaucoma, while the Beijing Eye Study found myopia subjects to be five to six times more likely to develop glaucoma.

Various studies in the United States have shown individuals with myopia and visual field defects to have two to fourteen times the risk of glaucoma.

Dr. Lin said he asks his patients with glaucoma if they have sleep apnea, because it is a treatable risk factor, although the data on sleep apnea’s relationship to glaucoma is not clear-cut.

Some studies have found a possible link, whereas others have not. He suggested that sleep apnea could be related to fluctuations in perfusion pressure and low blood pressure, as supported by the Early Manifest Glaucoma Trial. He recommended ophthalmologists measure blood pressure in normotensive glaucoma patients and coordinate medical management with patients’ internists. He advised patients to take their blood pressure medication in the morning, not at night when IOP increases. 

In studies in which patients self-report intake of excessive amounts of calcium and/or iron supplements, these individuals have two to seven times the relative risk for glaucoma. Calcium and iron are oxidants and high doses can be detrimental to the optic nerve.  

Women who have taken birth control pills for 5 or more years have been shown to have a 29% increase in the risk of developing glaucoma, Dr. Lin noted. He recommended that physicians ask female patients if they take this type of medication. 

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