New Zealanders with glaucoma are being shortchanged when it comes to treatments. The condition is the leading cause of preventable blindness and can be managed using daily eye drops. However, the drops that are funded here include a preservative called benzalkonium chloride (BAK), a very effective antiseptic that unfortunately causes eye irritation in some patients.
It is estimated that about half of all people on long-term eye-drop therapy for glaucoma suffer from ocular surface disease, which includes dry eye syndrome and can also result in redness, burning, foreign body sensation and light sensitivity.
“If treatment is started early, most people don’t need to go blind from glaucoma,” says Auckland ophthalmologist Helen Danesh-Meyer. “But some patients may need to be using drops four to six times a day, and that can have significant side effects. After a while, people with very painful, red eyes will say they feel worse off with the drops and stop using them.”
Glaucoma is a group of related eye conditions that over time cause irreversible damage to the optic nerve if left untreated. Usually, loss of eyesight is gradual and won’t be noticed for a while because it affects the peripheral vision.
“People will tell me they can see the smallest letters on the eye chart so they must be doing really well,” says Danesh-Meyer. “But that chart only measures the central vision.”
The optic nerve is a bundle of about a million nerve fibres that connect with the brain. We are born with more of these fibres than we need so may not notice any signs if we lose a little of the reserve. But after a certain point, every loss of nerve fibres becomes more obvious.
The condition usually affects older people but eye specialists are diagnosing glaucoma at a younger age.
“Ideally, we’d like to catch people when they have a lot of reserve and hold onto it,” says Danesh-Meyer. “If you catch glaucoma early, it will really help you in later life.”
People who wear prescription spectacles and regularly need to see an optometrist are likely to have a glaucoma check as part of their annual eye exam.
“Most optometrists these days are very well equipped. It’s the people who have no issues with their eyes and have been managing with over-the-counter reading glasses who tend to come along with quite profound glaucoma,” says Danesh-Meyer.
She advises that everyone should have a baseline glaucoma assessment at about age 45 or when they start noticing that they need reading glasses.
She aims to preserve vision for the rest of her patients’ lives. If someone is diagnosed at 50, it might mean eye-drop treatment needs to continue for another 40-50 years.
With glaucoma, damage to the optic nerve is caused by a build-up of the fluid that the eye produces to stay healthy. The drops work by either increasing drainage of fluid from the eye or reducing the amount that is made in the first place. To be effective, they have to be used continuously.
“The number one cause of treatment failure is failure to put in the drops,” says Danesh-Meyer.
Preservative-free drops are more expensive and Pharmac doesn’t fund them currently. Danesh-Meyer is hoping to change that. She is conducting a trial with New Zealand patients that she hopes will show the advantages of these drops, which are subsidised in other countries. A study on cells in the lab showed significantly less inflammation with the BAK-free medication and she is now progressing with a clinical trial. She hopes that if the results show a significant difference in inflammatory markers, that will make a compelling case for Pharmac funding.
In general, the future for glaucoma sufferers does look brighter as more minimally-invasive treatments emerge, including new ways of giving eye drops and decreasing the amount of drops that patients need.
“Glaucoma is very common but it’s manageable,” says Danesh-Meyer. “It’s just a matter of making more comfortable treatments available so they’re not impinging on people’s quality of life.”
