According to an American research, drinking more than three cups of coffee a day may increase the risk of vision loss and blindness.
Even moderate amounts of the drink make developing the devastating eye condition glaucoma more likely.
The study, published in the journal Investigative Ophthalmology & Visual Science, suggests coffee lovers reduce their intake to reduce their chances of developing the condition.
Glaucoma occurs when the drainage tubes within the eye become slightly blocked.
This prevents eye fluid from draining properly, causing pressure to build up.
When the fluid cannot drain properly, pressure builds up.
This can damage the optic nerve, which connects the eye to the brain, and the nerve fibres from the retina (the light-sensitive nerve tissue that lines the back of the eye).
The researchers, from the Brigham and Women’s Hospital in Boston, suggest that compounds found in coffee may increase pressure within the eyeball, causing a vision-destroying condition known as exfoliation glaucoma.
This occurs when material is rubbed off both the eye’s iris and lens, which then clogs up the eyeball’s fluid-draining system, leading to increased pressure within the eye
However, no correlation was with other caffeine products such as tea, cola or chocolate.
Previous research has found that Scandinavian populations have the highest occurrence of exfoliation glaucoma.
They also have the highest consumption of caffeinated coffee in the world.
The new study assessed more than 120,000 people in the UK and U.S. who were over 40 and not suffering from glaucoma.
They completed questionnaires about how much coffee they drank and their medical records were checked for a history of glaucoma.
Those who drank more than three cups a day were had an increased risk of developing glaucoma compared with those who abstained.
Women with a family history of glaucoma also had an elevated risk.
Coffee may not be without its benefits, however. Research published earlier this year in the New England Journal of Medicine found drinking four to five cups a day possibly reduced the risk of heart disease, stroke and diabetes, among other conditions.
GLAUCOMA: THE DISEASE THAT DESTROYS VISION
Glaucoma affects 1% of people over 40 and around 5% of people over 65.
Those at increased risk include diabetics, people of African or black Caribbean origin and those with a family history of glaucoma.
The condition develops very slowly and, as a result, usually has no noticeable symptoms.
Sight loss also goes unnoticed because the first part of the eye to be affected is the outer field of vision (peripheral vision).
The damage then slowly works inward, towards the centre of the eye.
Two men from UK, who have been totally blind for many years, have had part of their vision restored after surgery to fit pioneering eye implants.
The men are able to perceive light and even some shapes from the devices which were fitted behind the retina.
The patients are part of a clinical trial carried out at the Oxford University Eye Hospital and King’s College Hospital in London.
Professor Robert MacLaren and Dr.Tim Jackson are leading the trial.
The two patients, Chris James and Robin Millar, lost their vision due to a condition known as retinitis pigmentosa, where the photoreceptor cells at the back of the eye gradually cease to function.
The wafer-thin, 3 mm square microelectronic chip has 1,500 light-sensitive pixels which take over the function of the photoreceptor rods and cones.
The surgery involves placing it behind the retina from where a fine cable runs to a control unit under the skin behind the ear.
When light enters the eye and reaches the chip it stimulates the pixels which sends electronic signals to the optic nerve and from there to the brain.
The chip can have its sensitivity altered via an external power unit which connects to the chip via a magnetic disc on the scalp.
The wafer-thin, 3 mm square microelectronic chip has 1,500 light-sensitive pixels which take over the function of the photoreceptor rods and cones
Chris James from Wroughton in Wiltshire said there was a “magic moment” when the implant was switched on for the first time and he saw flashing lights – showing that the device was functional.
“I am able to make out a curve or a straight line close-up but I find things at distance more difficult. It is still early days as I have to learn to interpret the signals being sent to my brain from the chip.”
Chris James, a motor-racing enthusiast, says his ambition is to be able to make out the silhouettes of different cars on the race-track.
Prof.Robert MacLaren, who fitted the first implant in the UK at the Oxford Eye Hospital, said:
“It’s the first time that British patients who were completely blind have been able to see something.
“In previous studies of restorative vision involving stem cells and other treatments, patients always had some residual sight.
“Here the patients had no light perception at all but the implant reactivated their retina after more than a decade.”
The chip results in the brain receiving flashes of light rather than conventional vision – and it is in black and white rather than color.
But in an unexpected development, the other British man to have the implant says he is now able to dream in color for the first time in 25 years. Robin Millar says he is also able to stand in a room and detect light coming through windows.
Prof. Robert MacLaren said the results might not seem extraordinary to the sighted, but for a totally blind person to be able to orientate themselves in a room, and perhaps know where the doors and windows are, would be “extremely useful” and of practical help.
In 2010 a Finnish man who received the experimental chip was able to identify letters, but his implant worked only in a laboratory setting, whereas the British men’s devices are portable. The implant was developed by a German company, Retina Implant AG.
Dr. Tim Jackson, eye surgeon at King’s College Hospital who has also fitted one of the devices, said:
“This pioneering treatment is at an early stage of development, but it is an important and exciting step forward, and may ultimately lead to a much improved quality of life for people who have lost their sight from retinitis pigmentosa.
“Most of the people who receive this treatment have lost their vision for many years, if not decades. The impact of them seeing again, even if it is not normal vision, can be profound, and at times quite moving.”
Both surgeons stress that the chip is not a treatment but part of a clinical trial. Up to a dozen British patients will be fitted with the implants.
Although it could ultimately benefit patients with the most common form of progressive blindness, age-related macular degeneration, they are not eligible for the study at present.
Nor are patients with glaucoma or optic nerve disease.
