Computer software to spot signs of glaucoma earlier than conventional tests is being developed by UK experts.
Carol Bronze, a glaucoma patient, found the test easy to use
The team at London's Moorfields Eye Hospital say the test has the potential to prevent many patients going blind.
Diagnosing glaucoma can be difficult, as patients are often not aware of symptoms until a great deal of useful sight has been permanently destroyed.
It is estimated glaucoma affects 67m people worldwide, including 500,000 in the UK - but only half are diagnosed.
AT RISK OF GLAUCOMA
People with a positive family history of the disease
People over 40 years old, with risk continuing to rise with age
People of West African origin
This has led to glaucoma being dubbed the "silent blinding disease".
It is estimated that if just 10% of UK glaucoma cases were detected and treated earlier it could save up to £1bn a year.
If diagnosed in time, the condition can be easily treated with eye drops.
The condition causes damage to the optic nerve which carries visual information from the eye to the brain.
Over the internet
The Moorfields Motion Detection Test (MDT) is designed to assess the field of vision.
The software can be downloaded to a laptop computer, and eventually it is hoped to make it available directly from the internet.
A central white spot and several white lines are displayed on a grey screen.
The patient is asked to look steadily at the central spot and to press the computer mouse each time one of the lines is seen to move.
The lines move at the same speed but move different distances as the test proceeds, meaning experts can detect the degree of visual loss.
Moorfields say the test is affordable, portable, quick - and has the potential to spot glaucoma earlier than conventional tests, and with greater accuracy.
Professor Vis Viswanathan, a consultant surgeon in glaucoma at Moorfields who developed the system, said conventional tests - which concentrate on the ability to see light - fail to pick up a patient's ability to detect movement.
However, the ability to perceive motion is one of the first things to vanish in people suffering glaucoma.
He said: "A better test would be based on the ability to perceive motion and that is how this test came about.
"In general terms, if somebody is perceiving very small amounts of motion, they are in pretty good shape."
Steve Winyard, from the RNIB, said current tests often inaccurately diagnosed a problem in people who did not have glaucoma. He said the new test promised to be more accurate.
"This is a valuable step forward," he said.
From April, clinics in Toronto, Rome, Africa and Singapore will be testing the software with the aim of independently verifying how effective it is.
Next year, researchers hope to be able to secure funding to roll out the software across the UK.
The first World Glaucoma Day is being held on Thursday to raise awareness of the condition.
Professor Peng Tee Khaw, a consultant ophthalmologist at Moorfields, said: "By the time people come to us they have often lost a lot of their sight and the damage is permanent.
"If we could pick these people up at an earlier stage it would make a tremendous difference to their lives."