Some supplements may increase risk
By David Dunaief, M.D.
Glaucoma is the second-leading cause of blindness in the world, behind cataracts. It is neurodegenerative (deterioration of the optic nerve) with increased intraocular pressure (IOP) — pressure inside the eye — as an indicator that nerve damage is more likely. The most common types of glaucoma are open angle and angle closure. Open-angle glaucoma represents about 90 percent of U.S. cases and is caused by clogging of the eye’s drainage canals over time (1). Because it develops slowly and over time, its symptoms are not always obvious.
Glaucoma initially causes peripheral vision loss and then works its way inward to the central vision. If untreated, it can lead to irreversible blindness (2). The occurrence of this disease is rising, with an estimated three million Americans affected and a predicted level of roughly 3.4 million in the U.S. by 2020.
Fortunately, there are treatments. Some revolve around reducing fluid production in the eye, such as beta blockers and carbonic anhydrase inhibitors. Others work to increase fluid drainage, such as cholinergics and prostaglandin analogs. Still others do both (1). None of these treatments reverse lost vision or damage. They only slow or halt its progression to preserve your remaining sight. Therefore, prevention and early detection are crucial.
Glaucoma risk factors include age — starting at 40, although those over 65 have higher risk and those over 80 have the highest risk —and race, with African-Americans at a five-times higher risk than those of European ancestry. In the Baltimore Eye Survey, a family history of the disease dramatically increased risk, with siblings having greater probability than offspring of developing the disease (3). Other risk factors include steroid use, including asthma inhalers, eye injury, nearsightedness and hypertension. Finally, the higher the IOP, the greater the risk for progression in open-angle glaucoma (4).
Effect of increased visual field testing
In the Advanced Glaucoma Intervention Study, it was found that visual field testing by an ophthalmologist every six months for patients at higher risk was better at predicting disease progression than annual testing (5). The result was that, with more frequent testing, the researchers were 50 percent more likely to detect progression of the disease, if it were to occur.
Interestingly, the U.S. Preventive Services Task Force currently does not recommend screening for open-angle glaucoma, since it feels there is insufficient evidence (6). The American Academy of Ophthalmology recommends screening every two to four years starting at age 40, with increased frequency of every one to three years starting at age 55 and every one to two years for those 65 and older. More frequent screening is recommended for those who have more risk factors (7).
There are several steps that may be valuable, including reducing chronic diseases associated with glaucoma such as type 2 diabetes, Alzheimer’s and erectile dysfunction. If we reduce their incidence, there may also be a reciprocal decline in glaucoma. In addition, avoiding or reducing supplementation with iron and calcium, while potentially increasing magnesium, may decrease incidence of the disease.
Diabetes and high blood pressure
In an analysis of two studies, diabetes increased the risk of open-angle glaucoma by greater than 200 percent (8). In the same analysis, however, systemic hypertension (high blood pressure) increased the risk by a meager 7 percent. This is yet another reason we need to control or prevent diabetes to preserve eye health, aside from diabetic retinopathy (disease of the back of the eye).
Erectile dysfunction association
Those with erectile dysfunction (ED) had an almost threefold increased risk of also having open-angle glaucoma, compared to those without the disorder (9). There may be vascular symptoms associated with open-angle glaucoma as demonstrated by the increased association with ED. The study suggests that the mechanism of action that both disorders have in common is endothelial dysfunction (inner lining of the blood vessels), which involves a decreased level of nitric oxide, a potent vasodilator, which enables the vessels to expand and relax. ED was also associated with high cholesterol and blood pressure, heart disease and diabetes. It is not unusual to find that many diseases have a common underlying pathology.
A 2013 study found that supplementation with calcium and iron, looked at separately, increases risk of normal-tension glaucoma (NTG), glaucoma without increased pressure (10). The calcium and iron came from a variety of sources, including antacids, multivitamins and prescription and nonprescription supplements. Roughly one-third of glaucoma patients have NTG (11). Among Japanese patients, a study found that this number increases to two-thirds (12).
The supplementation study results showed that participants who took a composite of 800 mg daily of calcium were at an almost 2.5-times increased risk. Those who took 18 mg of iron on a daily basis were at an even higher risk, 3.8 times, of developing the disease. When taken together, iron and calcium increased risk by a resounding 7.2-fold. Interestingly, dietary sources of iron and calcium were associated with lower odds of glaucoma.
The good news is that a dose of 300 mg of magnesium citrate in patients with NTG showed a benefit in visual field over one month, compared to those who did not take magnesium (13). Although this was a randomized-controlled trial, it was also very small with only 30 patients.
While there are risk factors — such as family history, age and ethnicity — that can’t be changed, there are a number of modifiable factors as well. Glaucoma may be brought on by factors that are related to those causing systemic diseases. Therefore, it’s important to maintain good health overall to reduce the risk for glaucoma and its effects.
(1) glaucoma.org. (2) Lancet. 2004;363(9422):1711. (3) Arch Ophthalmol. 1994;112(1):69. (4) Ophthalmology. 2007;114(10):1810. (5) Arch Ophthalmol. 2011;129(12):1521-1527. (6) Ann Fam Med. 2005;3(2):171. (7) AAO.org. (8) Br J Ophthalmol. 2012;96(6):872-876. (9) Ophthalmology 2012;119:289-293. (10) Curr Eye Res. 2013 Oct;38(10):1049-1056. (11) Ophthalmology. 1992;99(10):1499–1504. (12) Jpn J Ophthalmol. 1991;35(2):133–155. (13) Eur J Ophthalmol. 2010;20(1):131-135.
Dr. Dunaief is a speaker, author and local lifestyle medicine physician focusing on the integration of medicine, nutrition, fitness and stress management. For further information, visit www.medicalcompassmd.com or consult your personal physician.