Retinopathy

Bilberry extracts standardized to contain 25% anthocyanosides have been suggested as a treatment for people with early-stage diabetic or hypertensive retinopathy. In a small preliminary trial, people with various types of retinopathy, including diabetic retinopathy and macular degeneration, were given 600 mg of bilberry extract per day for one month.¹ While researchers found that the tendency to hemorrhage in the eye was reduced and that blood vessels were strengthened, there were no reports of improved vision. A small double-blind trial found that 160 mg of bilberry extract taken twice per day for one month led to similar improvements in blood-vessel health in the eye and slightly improved vision in people with diabetic and/or hypertensive retinopathy.² Larger and longer clinical trials are needed to establish the effectiveness of bilberry for treating retinopathies.

Proanthocyanidins (OPCs), a group of flavonoids found in pine bark, grape seed, and other plant sources have been reported in preliminary French trials to help limit the progression of retinopathy.^3,4 In one controlled trial, 60% of people with diabetes taking 150 mg per day of OPCs from grape seed extract had no progression of retinopathy compared to 47% of those taking a placebo.⁵

Quercetin (a flavonoid) has been shown to inhibit the enzyme, aldose reductase.⁶ This enzyme appears to contribute to worsening of diabetic retinopathy. However, because the absorption of quercetin is limited, it is questionable whether supplementing with quercetin can produce the tissue levels that are needed to inhibit aldose reductase. Although human studies have not been done using quercetin to treat retinopathy, some doctors prescribe 400 mg of quercetin three times per day. Another flavonoid, rutin, has been used with success to treat retinopathy in preliminary research.⁷

The use of 160 mg per day of a standardized extract of Ginkgo biloba for six months has been reported in a small double-blind trial⁸ to improve impaired visual function in people with mild diabetic retinopathy.

Low blood levels of magnesium have been found to be a risk factor for retinopathy in white people with diabetes,^9,10 but not in black people with diabetes.¹¹ So far, no studies have determined whether supplementing with magnesium would help prevent the development of retinopathy.

Preliminary studies have reported improved vision in people with various diseases of the retina who took 45 mg per day of vinpocetine.¹²

One study investigated the effect of adding 100 mcg per day of vitamin B12 to the insulin injections of 15 children with diabetic retinopathy.¹³ After one year, signs of retinopathy disappeared in 7 of 15 cases; after two years, 8 of 15 were free of retinopathy. Adults with diabetic retinopathy did not benefit from vitamin B12 injections. Consultation with a physician is necessary before adding injectable vitamin B12 to insulin.

Free radicals have been implicated in the development and progression of several forms of retinopathy.¹⁴ Retrolental fibroplasia, a retinopathy that occurs in some premature infants who have been exposed to high levels of oxygen, is an example of free radical-induced damage to the retina. In an analysis of the best published trials, large amounts of vitamin E were found to reduce the incidence of severe retinopathy in premature infants by over 50%.^15,16 Some of the evidence supporting the use of vitamin E in the prevention of retrolental fibroplasia comes from trials that have used 100 IU of vitamin E per 2.2 pounds of body weight in the form of oral supplementation.¹⁷ Use of large amounts of vitamin E in the prevention of retrolental fibroplasia requires the supervision of a pediatrician.

Vitamin E has also been found to prevent retinopathy in people with a rare genetic disease known as abetalipoproteinemia.¹⁸ People with this disorder lack a protein that transports fat-soluble nutrients, and can therefore develop deficiencies of vitamin E and other nutrients.

In one trial, vitamin E failed to improve vision in people with diabetic retinopathy,¹⁹ although in a double-blind trial, people with type 1 diabetes given very high amounts of vitamin E were reported to show a normalization of blood flow to the retina.²⁰ This finding has made researchers hopeful that vitamin E might help prevent diabetic retinopathy. However, no long-term trials have yet been conducted with vitamin E in the actual prevention of diabetic retinopathy.

Because oxidation damage is believed to play a role in the development of retinopathy, antioxidant nutrients might be protective. One doctor has administered a daily regimen of 500 mcg selenium, 800 IU vitamin E, 10,000 IU vitamin A, and 1,000 mg vitamin C for several years to 20 people with diabetic retinopathy. During that time, 19 of the 20 people showed either improvement or no progression of their retinopathy.²¹ People who wish to supplement with more than 250 mcg of selenium per day should consult a healthcare practitioner.