Glaucoma treatment: Electrical retinal stimulation

Electrical stimulation treatment for glaucoma is coming into focus

Glaucoma is a foreboding spectre for many ageing Australians. A group of eye diseases which cause vision-reducing damage to the optic nerve, this common condition affects approximately one in every 200 people over the age of 40 — rising to one in eight in those over 80.

It doesn’t exclusively affect older people though, and approximately one in 10,000 babies are born with the condition according to Glaucoma Australia.

Currently, the only widely accepted treatments for glaucoma aim to lower the patient’s intraocular pressure (IOP) and methods range from medicinal eye drops to surgery. However, there are limitations to these treatments, which only slow or prevent further vision loss rather than restore it.

Read also: A smart contact lens to treat glaucoma can measure eye pressure and deliver drug as needed

Further, while high IOP correlates with glaucoma, it does not necessarily cause it. Glaucoma can still impact 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 being explored that is showing increasing promise is the use of electrical retinal stimulation to restore glaucoma-induced vision loss.

Running electricity to your eyes might seem extreme, but this treatment may be much gentler and more effective than it sounds.

Eye-opening work

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

Schuman is the vice chair for ophthalmology research at NYU Langone Health, New York, and has been a principal researcher for the National Eye Institute in the US since 1995. Specialising in glaucoma, his team was the first to discover a molecular marker for the disease in humans more than 20 years ago.

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 on glaucoma patients.

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 the current moving along the nervous system’s visual pathways to also activate areas such as the optic nerve and brainstem.

“Photoreceptors [aka retinal cells] are responsible for perceiving the world,’ neurologist Dr. Anton Fedorov of the Fedorov Restore Vision Clinic told Cosmos Weekly. “Those cells create special signals, like small electric currents, and those currents go to the brain [which uses them to] create a picture about the world.”

This treatment doesn’t regenerate cells and is unable to resurrect dead nerves. Rather, the electrical stimulation aims to bolster 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 retinal cells. If the trunk is damaged, [the leaves are] going to die, because they have no nutrition. Any kind of optic nerve damage causes lack of retinal cells.”

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

Bernhard Sabel, Sabel Vision Restoration (SAVIR) Center

When retinal cells are damaged they don’t respond to stimuli as they should, and only send weak signals to the brain. This treatment is targeted at helping strengthen and multiply such signals.

Electrical stimulation also increases blood flow, though not by directly impacting the blood vessels themselves. Rather, stimulating nerves causes them to demand more blood in support of their increased function, prompting more to flow to the area. This is significant as reduced blood flow is a prominent issue in patients with glaucoma.

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

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

An impressive view

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

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

Despite the majority of international glaucoma specialists’ general uncertainty regarding electrical stimulation, several German clinics already offer it to patients. These include both the SAVIR Center and Fedorov Restore Vision Clinic, founded and run 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 around six, eight places where this treatment is available,” says Fedorov.

Treatment typically takes place over the course of 10 days and involves applying electrodes to the patient in order to stimulate their nerves. Exactly where the electrodes are placed varies, as this treatment is still being developed and trialled. However it is commonly administered transorbitally — via the eye socket.

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

Keeping an eye out

While it has been promising, electrical stimulation is by no means a magical cure-all. Sabel notes that though the majority of the approximately 1500 patients he has treated have had good results, different people have different responses to it. Some only see improvement after they have completed their treatment plan and a few don’t see any improvement at all.

“There are some patients, in all fairness, who don’t benefit,” says Sabel. “Before I used to say 50, then I went down to 30 per cent. Now I’m more around 10 per cent that don’t benefit — 10, 15 per cent.”

Further, though electrical stimulation may restore some vision to people whose visual field has been reduced, it does not technically treat glaucoma itself. Opinion also varies regarding how long this treatment’s effects might last, and Schuman stresses that this technology is still being studied.

“It is probably best to use rtACS before severe damage has occurred, but we really don’t have enough data to say at what point it might work best, or even to state that it is definitively effective,” says Schuman. “The effect seems to peak after a couple of months and fade over 6-12 months, but it is really too early to say with certainty.”

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

Anton Fedorov, Fedorov Restore Vision Clinic

Despite these caveats, this treatment could help glaucoma patients at least in the short term, particularly considering the currently known risks are primarily financial. Schuman says there is “little or no risk that we know of” surrounding this treatment, and studies on it have generally deemed it safe.

Fedorov says: “We use very friendly, not dangerous, not harmful currents to stimulate cells.”  He studied the electrical currents cells use to communicate with each other, then developed machines that produce the same currents. “We use currents which cells understand. We don’t damage cells, we’re just pushing them to work,” he says.

Sabel did note that in rare cases electrical stimulation has made patients’ foggy vision worse, and older and more frail patients were at higher risk. However, this is typically temporary and he has never had any serious adverse effects in any of his patients nor heard of any in reported literature.

Looking forward

Despite its apparent potential, using electrical stimulation on glaucoma patients isn’t common practice either within Australia or internationally.

Both the Centre for Eye Research Australia and Glaucoma Australia are unaware of any local ophthalmologists who offer this treatment, nor any researchers with expertise in the area. The latter did note that research and trials are currently under way in the US and UK, but practical application remains a rarity. Travelling to Germany thus seems to be Australian glaucoma patients’ best chance of accessing this treatment.

This may soon change though. Fedorov speculates that electrical stimulation could grow in popularity and spread to more countries in as little as five years, while Sabel is looking toward establishing franchisees in other countries.

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

Bernhard Sabel, Sabel Vision Restoration (SAVIR) Center

“We have patients from Australia, we have patients from New Zealand, and so forth,” says Sabel. “The question is: when do we come to Australia?”

The SAVIR Center is also developing a portable electro-stimulation machine about the size of a mobile phone, which would allow patients to administer the treatment themselves at home. Sabel told Cosmos Weekly the device itself has already been approved in Europe, and that the user experience is currently being tested. He hopes to have it available within the year. It won’t cure glaucoma, and there is still significant research that must be done. Even so, electrical retinal stimulation appears primed to open new possibilities for the treatment of glaucoma-induced vision loss — and for improving patients’ lives.

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