Normal tension glaucoma linked to cognitive impairment

Australian researchers say they have established a link between the eye condition glaucoma and cognitive impairment, the state that often occurs before dementia.

Glaucoma damages the optic nerve, which transports visual information to the brain. Untreated, it can lead to blindness. Usually, glaucoma is the result of a build-up of pressure in the eye. In a study, published in the British Journal of Ophthalmology, higher rates of cognitive impairment were found with patients with a rarer type of glaucoma, called normal tension glaucoma.

Read more: Can your phone help prevent blindness?

“Cognitive impairment was found to be more than twice as prevalent in patients with normal-tension glaucoma than it was in those with high-tension glaucoma,” said study lead author Dr Sean Mullany, an ophthalmologist at Flinders University.

“Our finding of an association between this type of glaucoma and cognitive impairment supports a growing body of evidence suggesting an association between glaucoma and dementia.

“This association between normal-tension glaucoma and dementia has the potential to change our understanding about the glaucoma and provides insight into future treatment directions.”

Read more: Early warning signs for glaucoma

Thankfully, there has been good news on the possible way forward for treatment of glaucoma.

“Scientists at the University of Cambridge have shown in animal studies that gene therapy may help repair some of the damage caused in chronic neurodegenerative conditions such as glaucoma and dementia,” reports medicalxpress.com.

Gene therapy replaces a missing or defective gene with a healthy version. It is being used more commonly for neurological conditions.

Neurodegenerative diseases often disrupt axonal transport, a cellular process that moves key molecules and cellular ‘building blocks’ including mitochondria, lipids, and proteins to and from the body of a nerve cell.

Axons are long fibres that transmit electrical signals, allowing nerve cells to communicate with other nerve cells and muscles. Scientists speculate that stimulating axonal transport could repair damaged nerve cells.

The study’s lead author, Dr Tasneem Khatib, from the John van Geest Centre for Brain Repair at the University of Cambridge, said: “The axons of nerve cells function a bit like a railway system, where the cargo is essential components required for the cells to survive and function. In neurodegenerative diseases, this railway system can get damaged or blocked. We reckoned that replacing two molecules that we know work effectively together would help to repair this transport network more effectively than delivering either one alone, and that is exactly what we found.

“This combined approach also leads to a much more sustained therapeutic effect, which is very important for a treatment aimed at a chronic degenerative disease.”

Professor Keith Martin, from the Centre for Eye Research Australia and the University of Melbourne, who led the study while at Cambridge, added: “While this is currently early stage research, we believe it shows promise for helping to treat neurodegenerative diseases that have so far proved intractable. Gene therapy has already proved effective for some rare monogenic (involving or controlled by a single gene) conditions, and we hope it will be similarly useful for these more complex diseases which are much more common.”

Previously, researchers found showed that glaucoma patients were four times more likely to develop dementia.

Support site brightfocus.com says Alzheimer’s patients can have thinning of fibres and loss of cells in the retina and elements of the optic nerve, both “hallmarks of glaucoma”.

“One of the pathologic hallmarks of Alzheimer’s disease, an abnormaltau protein, has been found in the vitreous jelly(the clear jelly-like substance that fills the space from the lens to the back of the eye) of the eyes of glaucoma patients.”

Glaucoma is the world’s leading cause of irreversible blindness, expected to afflict 111 million people by 2040.

Glaucoma and Alzheimer’s disease affect older populations, involve selective loss of certain types of neurons, and are neurodegenerative, chronic, and progressive diseases that cause irreversible neuronal cell loss. 

Glaucoma can be detected before the onset of symptoms, through an eye test. It cannot be self-detected.

Glaucoma Australia recommends all Australians 50 years or older visit an optometrist every two years for a comprehensive eye exam. If you have a family history of glaucoma or are of Asian or African descent, they recommend you have your eyes checked every two years from the age of 40.

How often do you get your eyes tested? What diseases do you expect we will conquer next?

Read more: Drugs wildly over prescribed for dementia

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Written by Will Brodie



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