New glaucoma test could save millions from blindness
"It might be possible to treat the main cause of permanent blindness before people notice any loss of vision," BBC News report.
A proof of concept study of early testing for glaucoma – the most common cause of sight loss – had promising results.
In glaucoma, the light-sensitive cells of the retinal nerve die, usually because of increased pressure in the eye. The damage to the nerve, which is irreversible, causes progressive loss of vision. Because people with glaucoma often don't have symptoms in the early stages of the disease, a lot of damage may be done before it is picked up. Diagnosing glaucoma early would allow earlier treatment to relieve pressure in the eye, and may prevent sight loss.
The new technique involves injecting people with a fluorescent dye (thankfully into the bloodstream, not the eye), and taking images of the eye. Dying retinal nerve cells show up as white spots on the image.
Researchers compared images from eight people with early glaucoma and eight healthy people, and showed that white spots were more than twice as common in people with glaucoma. They also seemed more common in people whose glaucoma got worse quickly over time.
However, the technique needs to be tested in large-scale studies to confirm the result as well as find out more about any safety issues.
The study reinforces the importance of having regular eye tests as these can often pick up glaucoma before it becomes a significant problem. You should have an eye test at least every two years.
Where did the story come from?
The study was carried out by researchers from Western Eye Hospital, Imperial College and University College London and was funded by the Wellcome Trust. The study was published in the peer-reviewed journal Brain on an open-access basis so it is free to read online.
BBC News, ITV News and The Daily Telegraph all covered the story. Their reports were mostly accurate and balanced, although none made clear the amount of research that still needs to be done before the new test can be put into use.
What kind of research was this?
This was an open label, phase one clinical trial designed to establish proof of concept. Trials of medicines and tests go through three phases to ensure they are safe and effective.
The study was the first done in humans, so researchers wanted to know if it worked, if it caused any adverse effects, and what effect different doses of the dye had. They will now need to do phase 2 and phase 3 trials on much bigger groups of patients to confirm their initial results.
What did the research involve?
Researchers recruited eight healthy adults without eye disease and eight adults being treated for early glaucoma at the hospital, with no other eye disease. People had an injection of the fluorescent dye (one of four different doses) then had their eye scanned by an infrared laser ophthalmoscope. The researchers assessed the images and compared those from healthy people and people with glaucoma.
Everyone was given a full eye examination when they were recruited, on the day of the test, and 30 days later. They were monitored for adverse events from the injection for six hours, with a phone call 24 hours later.
Researchers also looked to see what happened to the people with glaucoma during their future clinical follow-up visits, for up to 16 months. They then looked to see if the test results predicted how their glaucoma progressed.
What were the basic results?
Participants with glaucoma had on average more than twice as many white spots showing dying nerve cells as people with healthy eyes (2.37-fold increase, 95% confidence interval 1.4 to 4.03).
People with glaucoma whose disease got worse over the following months also had more white spots than those whose disease stayed the same. Among people without eye disease, older people had more white spots.
Glaucoma is more common among people aged over 75.
No-one had major side effects linked to the injection (one person found it painful and one person had a bruise afterwards).
How did the researchers interpret the results?
The researchers stress their results need to be confirmed by bigger trials, saying: "Like any new technology," it will "need robust testing if it is to be successfully validated."
However, they say, it might be possible to use the test "as a method of detection and monitoring of patients" with glaucoma. They say they have shown that the technique may be useful for identifying nerve degeneration.
They further theorise that it might one day be used for other diseases, including the eye disease macular degeneration, optic neuritis (inflammation of the optic nerve) and "Alzheimers-related disease."
Conclusion
Glaucoma is responsible for about 10 in 100 people registered blind in the UK. About 2 in 100 people over 40 in the UK have glaucoma, and around 10 in 100 of those aged over 75. Because there is no cure, but early treatment can often help slow or prevent damage, early diagnosis is important.
Regular eye tests may pick up glaucoma, but often there's no sign of the disease until people have already begun to lose vision. That's why this test is interesting. If it can be shown to work well and safely, it could be a quick and efficient way to diagnose glaucoma before people have started to lose their sight. However, there's more work to do before we get to that stage.
The initial trial results in 16 people need to be repeated among bigger groups, to be sure the results hold true. The researchers need to establish the best dose of the fluorescent dye. Importantly, they need to establish what number of white dots is normal, and what number suggests early glaucoma. This research only shows that people with glaucoma had more white dots, not what would be a good cut-off point for early diagnosis.
Everyone should have a routine eye test at least every two years. This may include a test for high pressure in the eye, as well as a sight test.
If a close relative has glaucoma, mention it to the optician to be sure they carry out appropriate checks. Some types of glaucoma can run in families, so if you do have a family history, more frequent tests may be recommended.
