Glaucoma treatment: electrical stimulation of the retina

Glaucoma is a foreboding specter for many elderly Australians. A group of eye diseases that cause damage to the optic nerve that reduces vision, this common condition affects approximately one in 200 people over the age of 40 – rising to one in eight people over the age of 80.

However, it does not exclusively affect older people, and approximately one in 10,000 babies are born with the condition according to Glaucoma Australia.

Currently, the only widely accepted treatments for glaucoma are aimed at lowering the patient’s intraocular pressure (IOP) and methods range from medicated eye drops to surgery. However, there are limitations to these treatments, which only delay or prevent vision loss rather than restoring it.


Also Read: A Smart Contact Lens to Treat Glaucoma Can Measure Eye Pressure and Deliver Medication as Needed


Also, while high IOP is correlated with glaucoma, it is not necessarily the cause. Glaucoma can still affect patients whose IOP is within the normal range — a condition called normal-tension glaucoma.

As such, there is still significant room for discovery and innovation regarding our approach to glaucoma. One area that is being explored and that is showing increasing promise is the use of electrical stimulation of the retina to restore glaucoma-induced vision loss.

Putting electricity in your eyes might seem extreme, but this treatment can be much gentler and more effective than it sounds.

eye opening work

“Repetitive Transorbital Alternating Current (rtACS) Stimulation induces sublethal stress on the retina, optic nerve, and visual brain,” says Dr. Joel S. Schuman Weekly Cosmos. “This results in improved visual function for certain individuals.”

Schuman is vice president of ophthalmology research at NYU Langone Health in New York and a principal investigator at the National Eye Institute in the US since 1995. Specializing in glaucoma, his team was the first to discover a molecular marker for the disease in humans in recent years. more than 20 years.

Glaucoma
Image of an eye with glaucoma. Credit: Science Photo Library / Sue Ford

He is currently conducting a clinical trial on the use of electrical stimulation in patients with glaucoma.

Modern research into electrical stimulation to treat vision loss originated in Russia in the 1980s and began as an invasive procedure involving small, surgically placed electrodes. It has since evolved into a non-invasive procedure designed to stimulate retinal cells, with current moving along the visual pathways of the nervous system to also activate areas such as the optic nerve and brain stem.

“Photoreceptors [aka retinal cells] are responsible for perceiving the world,” said neurologist Dr. Anton Fedorov, from Fedorov Restore Vision Clinic, Weekly Cosmos. “These cells create special signals, like tiny electrical currents, and those currents go to the brain. [which uses them to] create an image about the world.”

This treatment does not regenerate cells and is unable to resurrect dead nerves. Instead, electrical stimulation aims to reinforce the function of the structures that remain. Stimulating the visual system helps it to better interpret information, thus improving the patient’s visual field.

“Imagine a tree,” says Fedorov. “A tree has a trunk and leaves. Let’s say the optic nerve is the trunk of the tree and the leaves are the cells of the retina. If the trunk is damaged, [the leaves are] they will die, because they have no nourishment. Any kind of damage to the optic nerve causes a lack of retinal cells.”

“In glaucoma, we believe the main problem is that the blood supply is not working properly,”

Bernhard Sabel, Sabel Sight Restoration Center (SAVIR)

When retinal cells are damaged, they do not respond to stimuli as they should and only send weak signals to the brain. This treatment aims to help strengthen and multiply these signs.

Electrical stimulation also increases blood flow, although not directly impacting the blood vessels themselves. Instead, stimulating the nerves makes them demand more blood to support their increased function, bringing more flow to the area. This is significant as reduced blood flow is a prominent problem in patients with glaucoma.

“In glaucoma, we believe the main problem is that the blood supply is not working properly,” says Professor Bernhard Sabel of the Sabel Vision Restoration Center (SAVIR). A psychologist and researcher, Sabel’s focus was originally on brain plasticity before being restricted specifically to the visual system.

“I like to use the analogy of a car that runs on gasoline… You can’t just use the spark, you can’t just use the gasoline, you need both. And this is a similar process with nerve cells and the blood supply,” he says.

an impressive view

While electrical retinal stimulation is an exciting prospect that has had results, its use in glaucoma patients is still in its relative infancy.

“RTACS has been successfully used in the rehabilitation of visual impairments in people with optic neuropathies,” says Schuman in his study description. “[H]however, we do not know the clinical value of rtACS specifically for people with glaucoma, including the effect of rtACS on functional capacity and [quality of life].”

Despite the general uncertainty of most international glaucoma specialists regarding electrical stimulation, several German clinics already offer it to patients. These include the SAVIR Center and the Fedorov Restore Vision Clinic, founded and managed by Sabel and Fedorov, respectively. Both previously worked together to research the use of electrical stimulation to treat vision loss, before establishing their own separate practices in 2014 and 2015.

“In Germany, at least, there are about six, eight places where this treatment is available,” says Fedorov.

Treatment usually takes place over the course of 10 days and involves applying electrodes to the patient to stimulate their nerves. Exactly where the electrodes are placed varies, as this treatment is still being developed and tested. However, it is commonly administered transorbitally – through the eye socket.

“What we can’t recommend is transcorneal stimulation, because you actually put a wire over the eye,” Sabel says, although he acknowledges that some other practitioners do this. “I don’t think it’s a good idea in the long run.”

keeping an eye out

While it has been promising, electrical stimulation is by no means a magic cure. Sabel notes that while most of the roughly 1,500 patients he’s treated have had good results, different people have different responses to it. Some only see improvement after completing their treatment plan and some see no improvement at all.

“There are some patients, in all fairness, who don’t benefit,” says Sabel. “Before I used to say 50, then I dropped to 30%. Now I’m more like the 10% that doesn’t benefit – 10, 15%.”

Also, while electrical stimulation can restore some vision to people whose visual field has been reduced, it does not technically treat glaucoma itself. Opinion also varies regarding the duration of the effects of this treatment, and Schuman points out that this technology is still being studied.

“It’s probably best to use rtACS before serious damage occurs, but we really don’t have enough data to say at what point it might work better, or even claim that it’s definitely effective,” Schuman says. “The effect seems to peak after a few months and disappear in 6 to 12 months, but it’s too early to say for sure.”

“We use currents that cells understand. We don’t damage the cells, we’re just pushing them to work.”

Anton Fedorov, Fedorov Restore Vision Clinic

Despite these caveats, this treatment may help glaucoma patients at least in the short term, especially considering that the currently known risks are primarily financial. Schuman says there is “little to no known risk” surrounding this treatment, and studies of it generally consider it safe.

Fedorov says, “We use very friendly, non-dangerous, non-harmful currents to stimulate the cells.” He studied the electrical currents that cells use to communicate with each other, then developed machines that produce the same currents. “We use currents that cells understand. We’re not damaging the cells, we’re just forcing them to work,” he says.

Sabel noted that, in rare cases, electrical stimulation worsened patients’ blurred vision, and older, frail patients were at greater risk. However, this is typically temporary and he has never had any serious adverse effects on any of his patients nor has he heard of any in the reported literature.

Anxious

Despite its apparent potential, the use of electrical stimulation in patients with glaucoma is not common practice in Australia or internationally.

Both the Center for Eye Research Australia and Glaucoma Australia are unaware of any local ophthalmologist offering this treatment, nor are they aware of any researchers with experience in the field. The latter noted that research and testing is ongoing in the US and UK, but practical application remains a rarity. Traveling to Germany therefore appears to be the best chance for Australian glaucoma patients to access this treatment.

That might change soon though. Fedorov speculates that electrical stimulation could grow in popularity and spread to more countries in less than five years, as Sabel seeks to establish franchisees in other countries.

“We have patients from Australia, we have patients from New Zealand and so on… the question is, when did we come to Australia?”

Bernhard Sabel, Sabel Vision Restoration Center (SAVIR)

“We have patients from Australia, we have patients from New Zealand and so on,” Sabel says. “The question is, when are we going to Australia?”

The SAVIR Center is also developing a portable electrostimulation machine the size of a cell phone that would allow patients to administer treatment at home. Sabel said Weekly Cosmos the device itself has already been approved in Europe and the user experience is being tested. He hopes to have it available within the year. It does not cure glaucoma, and there is still significant research to be done. Even so, electrical stimulation of the retina appears to be poised to open up new possibilities for treating glaucoma-induced vision loss—and improving patients’ lives.



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