Metformin May Help Prevent Eye Disease in People With Type 2 Diabetes

October 31, 2018
Metformin, which helps stabilize blood sugar levels, helped people with diabetes lower their chances of developing age-related macular degeneration.

Metformin has established itself as the medication of choice when it comes to the first-line treatment of type 2 diabetes. In addition to lowering blood sugar, the medication may extend lives, lower heart risks, lower high blood pressure, and provide other health benefits.

Now researchers have also observed that metformin (which is sold under brand names such as Glucophage, Glumetza, and Fortamet) may also decrease the likelihood of age-related macular degeneraton (AMD) — a leading cause of vision loss among people age 50 and older. The condition, which people with diabetes are at a greater risk for, affects about 2.1 million people nationwide, according to the National Institutes of Health.

In a report presented October 28 at the Annual Meeting of the American Academy of Ophthalmology, researchers from Taiwan analyzed the health data of 45,524 people with diabetes who were taking metformin compared with 22,681 patients who were not taking the medication. All participants had newly onset type 2 diabetes. The retrospective study extended from January 2001 to December 2013.

The scientists found that metformin users had about a 50 percent lower risk of getting AMD compared with those not taking the medication.
“Our study is the first to reveal the protective effect of metformin on the development of AMD,” the lead investigator, Yu-Yen Chen, MD, from Taichung Veterans General Hospital in Taiwan, said in a statement. “While more study is required to determine just how metformin protects against the development of AMD, this is an exciting development for patients at risk.” Dr. Chen was not available for direct comment.

Mark Fromer, MD, an ophthalmologist at Lenox Hill Hospital in New York City, who was not involved in the study, says he has seen tens of thousands of patients with diabetes and thousands of macular degeneration patients. Because of the range of health issues that can result from high blood sugar, individuals who are prescribed metformin tend to have several preexisting health issues. However, Dr. Fromer says, “What you don’t often see in a lot of metformin patients is macular degeneration — so these researchers may be on to something.”
Dr. Fromer cautions that this is a retrospective study. While the investigation involved large numbers over a long period, he says a controlled study with current patients is needed so scientists can look at other factors, including smoking, obesity, diet, and the controlled use of the drug as well.

Why Might Metformin Help With AMD
Inflammation and oxidative stress have long been known to play a key role in the development of both diabetes and AMD, the researchers say. Oxidative stress is a disturbance in the balance between the production of damaging free radicals and the body’s ability to detoxify them. “Since metformin is found to have the properties of anti-inflammation and anti-oxidation, it is relevant to propose that metformin may reduce the occurrence of AMD,” the study authors write.

How Diabetes May Play a Role
When a person has diabetes, blood sugar can’t reach the cells for the glucose to be used as energy. The sugar that builds up in the blood is destructive to blood vessels that deliver blood to vital organs. This increases the risk of many health problems, including heart attack and stroke. Available as a tablet or liquid, metformin helps reduce the amount of sugar your liver releases into the blood, and it improves how your body handles insulin, which regulates the amount of glucose in the blood.

How Macular Degeneration Affects Sight
Macular degeneration damages a specific portion in the retina called the macula. The macula captures the images we see and transmits those visuals through the optic nerve to the brain. The National Eye Institute describes the macula as the part of the eye needed for sharp, central vision, which lets us see objects that are straight ahead. As the macula breaks down, vision becomes blurry or wavy, and may lead to total loss of vision. There is no known cure for macular degeneration.

“Every decade of life, your chances of developing macular degeneration increase,” says Fromer. “Each decade of your life your retinal function decreases.”

AMD is one of the two most common retinal degenerative diseases, according to a study in Clinical Ophthalmology. The other common eye-related problem for those with uncontrolled diabetes is diabetic retinopathy, which harms the blood vessels of the retina and results in patches of vision loss. The American Diabetes Association points out that more than 60 percent of people with type 2 diabetes have some degree of retinopathy.

Chen’s team notes that participants with hypertension, hyperlipidemia, coronary artery disease, obesity, and diabetic retinopathy also had a significantly higher risk of developing AMD.

While metformin may help reduce AMD risk, the American Macular Degeneration Foundation also recommends lifestyle changes such as dieting, exercise, avoiding smoking, and protecting your eyes from ultraviolet light.

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