AGING
May 17, 2017

Eye Saver

Caught early, glaucoma can usually be kept at bay. A new test gives doctors a much-needed edge.

The worst thing about glaucoma, aside from blindness it can cause, is that often by the time people are diagnosed, they have already lost a third or more of their vision to it. With early treatment, however, you can usually protect your eyes from serious vision loss. Now researchers have developed a test that they think can catch glaucoma as much as 10 years earlier.

Glaucoma is a group of diseases that can damage the eye’s optic nerve and result in vision loss and blindness. It is one of the main causes of blindness in the United States. Elevated pressure inside of the eye is most commonly the cause of this damage to cells in the eye's retina and the optic nerve, which connects the retina with the brain.

For now, the best protection against glaucoma is to get regular eye exams.

Like high blood pressure, glaucoma usually does its damage silently, without obvious symptoms. By the time current tests usually catch it, so many cells have died that vision loss has already begun.

The new test works by detecting cells that are still alive but have begun to die. The key is a protein produced by the human body called annexin A5.

Because of chemical changes that have occurred at the surface of dying cells, annexin A5 has a high affinity for them and, given the chance, will attach to these cells.

Researchers took annexin A5 and bound a fluorescent dye to it. When this bound annexin is injected into the bloodstream, some enters the eye and attaches to the dying cells in the retina, making them fluorescent. These cells light up and can be easily seen using an ophthalmoscope.

The method had been used to view dying nerve cells in animals but not in humans until researchers tested it on eight people who had been diagnosed with early stage glaucoma and eight people with normal vision.

Differences were obvious in as little as 15 minutes.

People with glaucoma had over twice as many fluorescent (dying) cells in their retinas. It has been estimated that between 77 and 90 retinal cells are lost daily in people with the disease.

The people in the study who had glaucoma were followed for up to 16 months after the test. Those whose test revealed the highest number of dying cells also tended to show greater progression of the disease, suggesting that the test is actually measuring glaucoma severity and progression.

This was a proof-of-concept study designed to show that the test can detect dying cells inside people's eyes and to test its safety and tolerability (no serious adverse effects were reported). It will take further studies to show if the test can reliably detect early stage glaucoma and whether it can also aid in early detection of other neurodegenerative diseases such as Parkinson's.

For now, the best protection against glaucoma is to get regular eye exams. Once it's diagnosed, there are treatments that can prevent further vision loss. And since glaucoma becomes likelier as you age, regular eye exams are especially important for older people.

The Glaucoma Research Foundation recommends that you get your eyes tested:

  • Every two to four years if you're under 40
  • Every one to three years if you're 40-54
  • Every one to two years if you're 55-64
  • Every six to 12 months, if you're 65 or older
  • The Foundation also recommends that anyone at high risk for glaucoma should be tested every year or two after age 35.

    The study appears in Brain and is freely available.

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