Supplements of iron and calcium may increase risk
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, with the majority of cases in the United States being the former.
Glaucoma initially causes peripheral vision loss and then works its way inward to the central vision. If untreated, it can lead to irreversible blindness (Lancet. 2004;363(9422):1711). Fortunately, there are treatments that revolve around reducing eye pressure, such as prostaglandins and beta blockers.
The occurrence of this disease is rising, with a current 2.8 million Americans affected and a predicted level of 3.4 million in the U.S. by 2020.
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 three-times higher risk than those of European ancestry. For African-Americans, it is the No. 1 cause of blindness. 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 (Arch Ophthalmol. 1994;112(1):69). Finally, the higher the IOP, the greater the risk for progression in open-angle glaucoma (Ophthalmology. 2007;114(10):1810).
The 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 (Arch Ophthalmol. 2011;129(12):1521-1527). 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 (Ann Fam Med. 2005;3(2):171). Whether it updates the results based on this study, only time will tell. The American Academy of Ophthalmology recommends screening every three to five years starting at age 40, with increased frequency — every one to two years — starting at age 60. More frequent screening is recommended for those younger than 60 who have more risk factors (AAO Pub 1996).
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 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 a analysis of two studies, diabetes increased the risk of open-angle glaucoma by greater than 200 percent (Br J Ophthalmol. 2012;96(6):872-876). In the same analysis, however, systemic hypertension (high blood pressure) increased the risk by a meager 7 percent. This yet another reason we need to control or prevent diabetes, aside from diabetic retinopathy (disease of the back of the eye).
Erectile dysfunction association
Those with erectile dysfunction (had an almost threefold increased risk of also having open-angle glaucoma, compared to those without the disorder (Ophthalmology 2012;119:289-293). 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. I wrote an article about the impact of ED on Aug. 11, 2011, that gives more detail on the disorder.
In an abstract presented at the American Glaucoma Society, supplementation with calcium and iron, looked at separately, increase risk of normal-tension glaucoma (NTG), glaucoma without increased pressure (AGS 2012 abstract 22). The calcium and iron came from a variety of sources, including antacids, multivitamins, prescription and nonprescription supplements.
The 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. The study did not look at dietary sources for iron and calcium.
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 (Eur J Ophthalmol. 2010;20(1):131-135). 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 irreversible affects.
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, go to the website www.medicalcompassmd.com and/or consult your personal physician.