Glaucoma can be a devastating disease that damages the optic nerve to leave some of its victims blind — but it doesn’t have to be. If caught in time, it is highly treatable. If left too long, the loss of eyesight is irreversible.
Professor Jamie Craig, Chair and Academic Head of the Department of Ophthalmology at Flinders University as well as a Consultant Ophthalmologist, is on a mission to make this catastrophic outcome a rarity.
“The treatments that we have are very, very good at slowing down disease progression or preventing worsening,” he says. “But they can't bring back vision that’s already lost.”
Unfortunately, the nature of the disease means often patients seek treatment when it is too late. Usually associated with ageing, the condition sees progressive loss of peripheral vision but the process is slow.
“Often the early stages are asymptomatic as you’re losing this side vision. There’s no pain and the clarity of the central vision can remain normal,” says Professor Craig.
“It is frequently associated with high eye pressure, which is one of the common contributors to glaucoma, but that’s not always the case.” That means, even with regular checks when a patient visits the optometrist, the condition can be missed.
In the developing world, the situation is even worse. There it is common for people to present with one eye that is totally blind, and the other in a very bad state.
“It’s a very difficult disease to treat in the developing world because there’s no screening,” Professor Craig says.
He believes a solution may lie in one of the other characteristics of the disease — its heritability.
If those most genetically predisposed to contracting the disease can be identified, it may be possible to improve targeted screenings or be more alert for signs and symptoms in the at-risk populations.
“It’s one of the most heritable diseases in all of medicine. There’s a strong genetic component,” says Professor Craig.
Sometimes this genetic component can be due to a high-impact change in a single gene.
But single-gene inheritance is only part of the picture being uncovered by Professor Craig and his team, including inaugural Snow Fellow, Associate Professor Owen Siggs.
Their program has recruited thousands of patients with severe glaucoma to identify more common and subtle genetic changes that may contribute to the disease.
“By doing that, we’ve come up with around 2,500 small genetic contributions to glaucoma that additively can make a very solid prediction for an individual,” he says.
Associate Professor Siggs adds “In some circumstances, these predictions are as good as genetic tests we already use in the clinic today.”
That research was published last year in Nature Genetics and allows doctors to ascribe a “polygenic risk score” (or PRS) to patients.
“In doing so, we can make a really strong prediction. People in the highest 10% of risk are 15 times more likely to get glaucoma than people in the lowest 10% of risk,” he explains.
That means a blood or saliva test could give a good indication of whether an individual is in a very high or low risk group.
While that doesn’t address the middle groups, the research has thrown up some unexpected findings that may make it more universally adaptable, such as whether a high-risk patient will need surgery, and at what age they get the disease. It also predicts how many family members are likely to get glaucoma.
“So now we’re designing a test that can be performed as a routine screening, similar to the over-50s bowel cancer screening.
“If we could access a sample from everyone at the age of 50, we would identify those in the very high-risk groups, and advise they turn up for a regular eye check-up for glaucoma.”
The team is also running a longitudinal research project monitoring around 2,000 people every six months. That has been going on for more than five years and has revealed a lot about who loses vision and how rapidly.
“It turns out that our PRS test is also quite good at predicting the rate of progression in early disease and who ends up losing vision, requiring treatment.
“We think that it might have value amongst people who have a borderline eye pressure test, for example, as then an optometrist could get those people back for further observation.”
But Professor Craig warns that eye pressure tests are not always a completely reliable indicator – around 30% of people with glaucoma have normal pressure.
While regular imaging of the optic nerve as well
as laser scanning can get around that and is highly effective at picking up early-stage glaucoma, it also picks up people who don't have glaucoma and are unlikely to contract it.
If all those with some borderline features were referred to a specialist, it would threaten to swamp the system.
“It's what we call the false positive conundrum,” says Professor Craig. “By doing really sophisticated testing, you can end up with a massive number of patients to deal with.”
The answer may lie in precision medicine made possible by artificial intelligence.
“We are working on the use of AI to refine our predictions and to work out who actually has a problem. In what we call the PROGRESSA study, the data includes laser photographs, pressure ratings and a whole lot of other measures about the rigidity of the eyeball, performance on field tests and the genetics.
“We’re currently feeding all of that information into AI algorithms. That's quite exciting because it takes it towards precision medicine where we can apply treatments, screening and monitoring at the individual level rather than just one size fits all.”
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