Caffeine May Worsen Glaucoma
Caffeine consumption may be harmful to people with glaucoma because it increases pressure within the eyeball (intraocular pressure, or IOP), according to a study in Annals of Pharmacotherapy (2002;36:992–5). Glaucoma is an eye condition usually associated with elevated IOP, which occurs because the fluid produced in the eye does not drain properly. The elevated pressure squeezes the optic nerve and chokes off its blood supply, eventually resulting in damage to the nerve cells that are necessary for vision. If left untreated, glaucoma can lead to blindness.
In the new study, 28 people with glaucoma consumed 200 ml (approximately 7 ounces) of regular coffee (containing 180 mg of caffeine) on one occasion and the same amount of decaffeinated coffee (containing 4 mg of caffeine) on another occasion. The two forms of coffee were consumed in random order, seven to ten days apart. IOP was measured before and 30, 60, and 90 minutes after the ingestion of each drink. Compared with decaffeinated coffee, regular coffee produced a statistically significant increase in IOP at both 60 and 90 minutes. The magnitude of the increase was approximately 2 to 3 mm Hg, an amount that, if sustained over the long term, could have an adverse effect on visual function. Additional research is needed to determine whether daily consumption of coffee or other caffeine-containing foods and beverages results in chronic elevation of IOP. The major sources of caffeine in the American diet are coffee, tea, chocolate, colas and certain other soft drinks, and some pain medications.
Conventional treatment of glaucoma includes medications that reduce IOP, either taken orally or instilled into the eye. These medications work by slowing the production of fluid within the eye or by helping excess fluid drain from the eye. If needed, surgical procedures (laser trabeculoplasty, trabeculectomy) can increase fluid drainage from the eye to relieve pressure.
Several studies have shown that supplementation with vitamin C can also reduce elevated IOP. However, large amounts (such as 10,000 mg per day) are needed to achieve a significant reduction, whereas smaller amounts (such as 1,000 mg per day) produce only a minor benefit. A few older reports suggested that allergy to foods or inhalants can increase IOP in susceptible individuals. In such cases, avoidance of the offending substances or desensitization therapy was frequently helpful.
Because glaucoma is a potentially serious disorder, all attempts to treat it should be done in conjunction with an ophthalmologist or other qualified healthcare practitioner.
Alan R. Gaby, MD, an expert in nutritional therapies, served as a member of the Ad-Hoc Advisory Panel of the National Institutes of Health Office of Alternative Medicine. He is the Medical Editor for Clinical Essentials Alert, is the author of Preventing and Reversing Osteoporosis (Prima, 1994), and co-author of The Natural Pharmacy, 2nd Edition (Healthnotes, Prima, 1999), the A–Z Guide to Drug-Herb-Vitamin Interactions (Healthnotes, Prima, 1999), Clinical Essentials Volume 1 and 2 (Healthnotes, 2000), and The Patient’s Book of Natural Healing (Prima, 1999). Currently he is the Endowed Professor of Nutrition at Bastyr University of Natural Health Sciences, Kenmore, WA.
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