A new preclinical study published by Karolinska Institutet researchers found that vitamin supplementation may help to slow down damage to the optic nerve caused by glaucoma.

The findings, which were published in Cell Reports, have already led to recruitment for a clinical study on glaucoma patients, the researchers reported.

In glaucoma, the optic nerve is gradually damaged, leading to vision loss and, in the worst cases, blindness. High pressure in the eye drops the disease, and present treatments include eye drops, laser treatment, and surgery to reduce pressure in the eye, with variable effect.

Glaucoma researchers have long theorized that the substance homocysteine is relevant to understanding the disease. The new findings, which include cell and animal studies, call into question whether homocysteine has a causative effect on glaucoma, or whether some other mechanism of action is at play.

For instance, when rats with glaucoma were given elevated levels of homocysteine, their disease did not worsen. Further, high levels of homocysteine didn’t correlate with disease progression, and people with genetic susceptibility to forming high levels of homocysteine didn’t have higher glaucoma rates, according to a review they conducted.

The researchers wanted to investigate other pathways involving homocysteine in both rodents and humans with glaucoma, and identified several abnormalities, the most important of which were metabolic changes linked to the retina’s ability to use certain vitamins. This change implied that metabolism was slowed down locally in the retina in glaucoma cases, which may play 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”, said James Tribble, researcher and assistant professor at the Department of Clinical Neuroscience at Karolinska Institutet and co-lead author.

Animal Study

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

In these experiments, eye pressure was left untreated, suggesting that the mechanism of action of the vitamin supplementation was independent from treatments which lower eye pressure.

“The results are so promising that we have started a clinical trial, with patients already being recruited at St. Eriks Eye Hospital in Stockholm,” said Tribble. The clinical trial will enroll patients with both open-angle glaucoma, a slower-progressing disease, and pseudoexfoliation glaucoma, which progresses more quickly.