Glow in the dark eye drops to save your sight
SCIENTISTS are developing a new test that could detect glaucoma ten years before symptoms appear — and potentially save the sight of millions of people. The technology, which detects dying nerve cells in the eye, has the potential to identify other neurological conditions at an early stage, such as Alzheimer’s and Parkinson’s.
Glaucoma i s the l eading cause of preventable blindness in the world and affects around 1,000 people in Ireland, though experts warn many more could be undiagnosed.
The test, which is being trialled for the first time in humans at the Western Eye Hospital in London, uses a type of fluorescent compound that makes the back of the eye ‘glow’ if glaucoma is present.
Glaucoma is caused when drainage tubes in the eye become blocked and fluid starts to build up in the eyeball. This leads to high pressure, causing damage to the optic nerve (which carries signals from the eye to the brain) and irreversible blindness.
However, t he condition is l argely symptomless and can progress for more than ten years before patients become aware of sight problems, such as a loss in peripheral vision.
Furthermore, any initial vision problems can go undetected by patients, as the brain tricks them into believing they have normal sight by filling in the edges of vision with what it thinks should be there.
Most cases of glaucoma are diagnosed by opticians when routine eye examinations test pressure in the eyeball, by using a machine that shoots a puff of air at it. Patients are referred to a specialist to confirm the diagnosis.
EYE drops to reduce the amount of fluid in the eye are given to prevent it from worsening. However, once glaucoma is detected by conventional tests, nerve damage may have already occurred.
The new test may help diagnose the condition before any vision loss occurs. Recent research has identified changes that occur in the nerve cells at the back of eye up to ten years before vision loss occurs.
These retinal ganglion cells are a crucial part of the lightsensitive layer in the eye called the retina. For unknown reasons, these cells start to undergo a type of ‘ cell suicide’ called apoptosis in the very early stages of glaucoma. The London team i s using a dye containing a naturally occurring protein, called Annexin, that sticks to these dying cells and produces a fluorescent light. This light can be seen with conventional eye testing equipment used by opticians. If a patient
has a high number of dying cells, this suggests they’re at risk of glaucoma. The hope is that patients could then be given medication to stop the disease in its tracks, by preventing further nerve cells from dying, before sight loss occurs.
One possibility is a neuroprotective drug, similar to those used for Alzheimer’s and stroke sufferers.
Furthermore, because apoptosis occurs in brain cells in the very early stages of Parkinson’s and Alzheimer’s, the team believe the test could one day be used to detect these conditions early.
The research, which is a collaboration between University College London, the Wellcome Trust and Imperial College Healthcare NHS Trust, will involve 28 patients — two-thirds will have glaucoma or similar diseases and one-third will be healthy controls.
Patients will receive one dose of the fluorescent dye via a vein in their arm. Their vision will be monitored for eight weeks.
The team, led by consultant ophthalmologists Professor Philip Bloom and Francesca Cordeiro, are developing the dye as an eye drop, so the test can be done at a high street optician.