KEY POINTS:
Eye specialists are urging people to have their eyes checked for a disease that can "silently" steal their sight - but the tests can cost up to $450.
Glaucoma is the country's leading cause of preventable blindness. It is estimated to affect 2 per cent of the population
at the age of 40 and 10 per cent at 70, but half of those with the disease do not know they have it.
"Glaucoma is a silent disease that tends to creep up on people without them being aware of it," said Associate Professor Helen Danesh-Meyer, a University of Auckland expert on the condition and a trustee of the Glaucoma NZ support group.
Caused by increased pressure within the eyes, the condition irreversibly damages the optic nerves, the conduit of visual information from the back of the eyes to the brain.
Chronic glaucoma affects side vision first and slowly creeps in, creating tunnel vision. If picked up early, however, it can be treated, typically with eye drops. Glaucoma NZ recommends everyone have a glaucoma check by the age of 45 and five-yearly tests afterwards. It urges earlier and more frequent checks for those with a family history of the disease, which increases your risk of developing it.
The main screening tests for glaucoma involve checking the pressure of the eyes and a visual-field check. Some practitioners take photographs of the back of the eye and laser-based machines for measuring thinning of the optic nerve are becoming more common.
Five optometry clinics nationally have these machines, which cost $54,500, and specialist eye surgeons' clinics often have more sophisticated versions costing around $100,000.
The machines are for screening, not diagnosis, but can allow earlier detection.
Professor Danesh-Meyer, an eye surgeon, said her glaucoma testing always included the laser-based machines. This added to the prices charged by specialists - around $250 to $450, although eye checks could be covered by medical insurance.
One Auckland optometry clinic that uses a laser-based machine charges $89 for a suite of eye tests, including glaucoma screening.
Another, which does not have one of the machines, charges $88. Its owner, Frank Snell, said that when he referred patients to the public health system with suspected glaucoma they were commonly seen within two months.
Professor Danesh-Meyer said there was no state funding for glaucoma screening and $90 was a big barrier for those on low incomes.
She and colleagues were startled by their recent research that showed people in New Zealand with a family history of glaucoma were 10 times more likely to present in the advanced stages of the disease than those in Britain, where the Government offered a free eye check to first-degree relatives of people with the condition.