Glaucoma Study Uncovers Brain Connection

Last month, CNIB Insight broke news about The Canadian Glaucoma Study, a CNIB-funded research project that is helping unlock the mysteries of glaucoma. Turns out it has been a busy few months in glaucoma research, as another study, also supported by CNIB, is pointing to exciting new treatment options for the disease that target the brain as well as the eye.

Neeru Gupta, glaucoma specialist, and Yeni Yucel, pathologist, both doctors at St. Michael’s Hospital and University of Toronto professors of Ophthalmology and Vision Sciences, are principal co-authors of the study, which in July received a prestigious award from the Association of International Glaucoma Societies in Singapore.

Glaucoma involves damage to the eye’s optic nerve. The disease often progresses over years, and many people do not realize they have it until their vision loss is irreversible.

One of the factors thought to affect the progression of the disease is pressure in the eye (called intraocular pressure, or IOP). As a result, treatment for glaucoma usually consists of prescription eye drops designed to reduce IOP, and surgery in severe cases. However, in spite of successful treatment, many patients still mysteriously progress in the disease.

The fact that some patients continue to lose vision even after treatment suggests that something other than pressure in the eye may also help explain disease progression.

Gupta and Yucel have spent the past decade exploring this possibility. Their previous work showed that nerve damage in the eye through glaucoma may spread to major visual centres of the brain (a process well known in other neurodegenerative diseases). When the damage spreads, nerve cells in the brain related to visual function begin to shrink and die.

But what if there was a way to prevent the degeneration of those nerve cells? In other words, what if there was a way to treat glaucoma inside the brain itself?

Gupta and Yucel’s study examined just that. Published in 2006 in the Archives of Ophthalmology, it is called “Memantine protects neurons from shrinkage in the lateral geniculate nucleus in experimental glaucoma.”

In an experimental model, they evaluated memantine (a drug used frequently in the treatment of Alzheimer’s disease that has no effect on eye pressure) to see if it would prevent damage to the major vision centres of the brain caused by glaucoma.

Amazingly, the drug had a significant effect, protecting the nerve cells from shrinking (the process is called neuroprotection). “It is the first evidence to show that we can reduce damage from glaucoma, not through medication that treats IOP, but through one that works in the brain,” says Gupta. However, “international efforts are already underway to analyze data from clinical trials to tell us whether patients might actually benefit,” she cautions.

“It’s very exciting because it opens the door for new treatment options that target both the eye and the brain.”

And that’s not all that’s exciting. Gupta and Yucel’s research has broader implications, since the neuroprotective process they demonstrated may also be applicable to other eye diseases.

The study is expected to guide the course of future glaucoma research worldwide. And Gupta and Yucel have nothing but praise for CNIB, which they say played a key role in bringing their project about.

While their research was funded by several agencies, CNIB was one of the first to back it. “The grant from CNIB came in the earliest stages, when we really needed it to continue with our work” says Gupta. “We are grateful for CNIB’s support. It was instrumental.”