A vitamin supplement that improves metabolism in the eye appears to slow down damage to the optic nerve in glaucoma. The promising results have been published in the journal Cell Reports Medicine. The researchers behind the study have now started a clinical trial on patients.

In glaucoma, the optic nerve is gradually damaged, leading to vision loss and, in the worst cases, blindness. High pressure in the eye drives the disease, and eye drops, laser treatment or surgery are therefore used to lower the pressure in the eye and thus slow down the disease. Unfortunately, however, the effect varies.

Glaucoma researchers have long theorized that the substance homocysteine is somehow relevant to understanding the disease. Now, researchers at Karolinska Institutet have investigated the role of homocysteine in several ways.

In the current study, the researchers discovered that when rats with glaucoma were given elevated levels of homocysteine, their disease did not worsen.

The researchers also found that high levels of homocysteine in the blood of people with glaucoma did not correlate with how quickly the disease progressed, and that glaucoma was not more common in people with a genetic susceptibility to forming high levels of homocysteine. Based on these findings, the researchers concluded that homocysteine does not drive the disease but is a consequence of it.

Since homocysteine is a natural part of the body’s metabolism, the researchers wanted to investigate metabolic pathways involving homocysteine in both rodents and humans with glaucoma.

They then saw several abnormalities, the most important of which were metabolic changes linked to the retina’s ability to use certain vitamins. This change meant that metabolism was slowed down locally in the retina—and this played a role in the development of the disease.

“Our conclusion is that homocysteine is a bystander in the disease process, not a player. Altered homocysteine levels may reveal that the retina has lost its ability to use certain vitamins that are necessary to maintain healthy metabolism. That’s why we wanted to investigate whether supplements of these vitamins could protect the retina,” says co-lead on the paper James Tribble, researcher and assistant professor at the Department of Clinical Neuroscience at Karolinska Institutet.

In experiments on mice and rats with glaucoma, the researchers gave supplements of the B vitamins B6, B9 and B12, as well as choline. This had a positive effect. In mice that had slower-developing glaucoma, the damage to the optic nerve was completely halted. In rats, which had a more aggressive form of the disease with faster progression, the disease was slowed down.

In these experiments, eye pressure was left untreated, which the researchers highlight as particularly interesting—it suggests that the vitamin mix affects the disease in a different way than lowering eye pressure does.

“The results are so promising that we have started a clinical trial, with patients already being recruited at St. Erik Eye Hospital in Stockholm,” says James Tribble.

Both patients with primary open-angle glaucoma (slower progression) and pseudoexfoliation glaucoma (faster progression) are included.