New research suggests that Glaucoma, what we know to be an ‘eye disease’, should instead be characterised as a neurologic disorder that causes nerve cells in the brain to degenerate and die – similar to what occurs in Parkinson’s and Alzheimer’s diseases.
For many years, the prevailing theory was that vision damage in patients with glaucoma was caused by abnormally high IOP. The new research paradigm focuses on the damage that occurs in retinal ganglion cells (RGCs), which connect the eye to the brain through the optic nerve.
Professor Bryce Vissel, Head of Research into Regeneration and Neural Plasticity at Sydney’s Garvan Institute of Medical Research, told mivision this is optimistic news for people with vision problems.
“Clinically, our only method of slowing glaucomatous loss of vision is to reduce intraocular pressure, but lowering intraocular pressure is only partially effective and does not address the underlying susceptibility of the retina to degeneration,” he said.
This… offers practical insights and solutions to ultimately treat retinal degeneration
“The recent literature suggests in fact that the mechanisms that cause the retina to degenerate may be similar to the mechanisms that occur say in stroke or even in Alzheimer’s disease. This is not merely interesting science; rather this is an important understanding that offers practical insights and solutions to ultimately treat retinal degeneration. People with vision problems should be optimistic that research across a variety of fields is ultimately also contributing to cures for eye problems.”
Treatments in Development
A review in Ophthalmology led by Jeffrey L Goldberg, assistant professor of ophthalmology at the Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, University of Miami, FL, describes RGC-targeted glaucoma treatments that are either being tested in patients or are scheduled to begin clinical trials soon. These include medications injected into the eye that deliver survival and growth factors to RGCs, medications known to be useful for stroke and Alzheimer’s disease, and electrical stimulation of RGCs. Human trials of stem cell therapies are in the planning stages.
“As researchers turn their attention to the mechanisms that cause retinal ganglion cells to degenerate and die, they are discovering ways to protect, enhance, and even regenerate these vital cells,” said Prof. Goldberg. “Understanding how to prevent damage and improve healthy function in these neurons may ultimately lead to sight-saving treatments for glaucoma and other degenerative eye diseases.”
Stem Cells Repair Glaucoma
One treatment using adult human retinal stem cells to repair nerve cells damaged in glaucoma could be ready for human trials in three to five years, according to scientists at the UCL Institute of Ophthalmology. The scientists, who are funded by the UK Medical Research Council, have successfully used adult human retinal stem cells to partially restore vision in rats.
The researchers looked at whether injecting a type of adult human stem cell, known as the Müller glia stem cell, could stimulate repair of damaged RGCs in an animal model. Müller glia are found in the retina of humans and other vertebrates and are multi-potent, meaning they can grow into any of the different nerve cells found in the retina. The researchers used chemicals to induce Müller glia to grow into precursors of RGCs, before transplanting them onto the retinas of rats, which had damage to their own RGCs.
After four weeks, the injected cells appeared to have formed new connections (synapses) with existing nerve cells and the rats had significantly improved retinal function when their vision was tested under very
low light conditions.
Dr. Astrid Limb, who led the study at the UCL Institute of Ophthalmology, which was published in the journal Stem Cells Translational Medicine, said: “Although this research is still a long way from the clinic, it is a significant step towards our ultimate goal of finding a cure for glaucoma and other related conditions. We are optimistic that after further work on animal models to perfect our transplantation technique we will be in a good position to start early-stage clinical trials on humans in around three to five years.
“The human eye is actually very efficient. We can still have fairly good vision with very few functioning retinal nerve cells, which is why many glaucoma patients don’t show symptoms until it is too late to treat the underlying cause of their vision loss. If we can restore even a small number of RGCs through cell therapy, and achieve functioning vision, we could potentially delay or even reverse blindness caused by glaucoma.”
Professor Peng T. Khaw, director of the NIHR Biomedical Research Centre at Moorfields and the Institute of Ophthalmology and a co-author of the paper, said: “These results are very exciting. We see patients with glaucoma whose lives would be transformed with an improvement of only a small percentage of nerve cell function. The results of these experiments suggest that this may be possible in the future using cells we all have in our own eyes to achieve this.”