As World Glaucoma Week begins, find out how to battle the 'silent thief of sight' with new eye drop that will help you stick better to your treatment plans and prevent irreversible blindness
Glaucoma is an eye condition where the optic nerve is damaged – often but not always due to high pressure in the eye. It is the leading cause of irreversible blindness.
What makes it particularly devastating is that it has no symptoms until the condition has reached an advanced stage, when vision loss has already occurred, says Associate Professor Shamira Perera, Senior Consultant, Glaucoma Department, Singapore National Eye Centre. Hence, it is also called the silent thief of sight.
He estimates that about 4 per cent of those over 40 have glaucoma, with the rate doubling to around 8 per cent for people above 80.
Broadly speaking, glaucoma can be open-angle or closed-angle, and treatment differs depending on the type. Open-angle glaucoma is often associated with a gradual clogging of the drainage canals in the eyes. It is more common worldwide, but in Asia, it is about evenly split between the two types.
As genetics plays a big role in glaucoma, Assoc Prof Perera advises those with a family history of the illness to get it checked early – and not just once – as they face a risk that is six times the average. For the rest of the population, he considers it prudent to be tested after the age of 40.
Treatment aims to control pressure in the eye to arrest vision loss
Eye drops are traditionally prescribed to treat glaucoma, but side effects like redness in the eyes and a haggard look may cause some patients to stop using them, which puts them at greater risk of losing more of their vision.
"Once we have diagnosed glaucoma, the aim is to stop it getting worse. In the first instance, we usually use eye drops because it’s convenient, has few side effects, generally speaking, and is easier to administer," he says. He also noted a trend towards using laser as a potential first-line treatment. While laser has its advantages, it is costlier.
"Glaucoma is a lifelong disease which needs lifelong follow up. While they may start off with one type of eye drop, that may not control the pressure, or they might get side effects. We might have to change it to a different drop or even add another one," says Assoc Prof Perera.
The most common class of drugs used for the eye drops are prostaglandin analogues, and several types are available.
"Prostaglandin analogues are generally well-tolerated but they do have some specific ocular side effects," explains Assoc Prof Perera. They include redness in the eyes and growing thicker and longer eye lashes. While that might not be an issue for women, it can be irksome for men, who can opt to trim the lashes.
Other side effects include darker pigmentation on the skin around the eyes – leaving the person with "panda eyes". This can be avoided by ensuring that the eye drops do not get on the skin, or to wipe them off if they do.
There can also be a deepening of the upper eyelid sulcus, which imparts an unappealing haggard look. While most of the side effects go away when using the eye drops stop, there can be a permanent darkening of the iris, which is awkward for someone with light-coloured iris or if glaucoma is in just one eye.
Such changes to their appearance can cause some people to stop using the eye drops, a fact not lost on the drug companies, which have been actively looking into ways to improve patient compliance.
Boon for patients
A new drug, omidenepag, available here for about a year has been able to address most of the side effects, making it easier for patients to keep using it while also helping to improve the outcome for any future surgery that might be needed, says Assoc Prof Perera. "It reduces the side effects around the eye dramatically. That’s a big boon for the patient."
It especially benefits younger people who are worried about their appearance or those who have glaucoma in one eye.
And it’s not just the patient who potentially benefits from omidenepag.
"There are some advantages also to the doctor of these drugs," he says.
This is because other prostaglandin analogues can cause a tightening of the eyelids which can make it difficult for doctors to measure the intraocular pressure accurately with the usual instruments. They would need to use a different way that requires just a small amount of the cornea to be visible.
Assoc Prof Perera adds that a study has also found that tightening of the eyelids and a deepening of the upper eyelid sulcus that can result from other prostaglandin analogues also negatively affects the outcome of any future surgery.
He recommends surgery as a last resort when medical treatment in the form of eye drops and/or laser have failed to slow down the progression of the glaucoma. The surgery aims to lower the pressure inside the eye by creating a bypass so that fluid inside moves to a bubble outside the eye and dissipates away into the blood vessels.
While omidenepag has its advantages, it is not suitable for people who have had cataract surgery or who are already on another prostaglandin analogue as it could lead to inflammation inside the eye. However, if the patient is on a different type of eye drop that is a beta blocker – a drug that decreases production of fluid that may increase pressure in the eyes – then adding omidenepag to the treatment is an option.
Assoc Prof Perera notes that even though rates of glaucoma here have remained stable over the past 20 to 30 years, there may be more people suffering from the condition as they may not be aware they have the illness. "That’s because we’re only diagnosing a small number of the people who actually have glaucoma. For every one person we know who’s got glaucoma, there are probably two to three who have got it but don’t know about it."
Usually, glaucoma cases are uncovered only when patients show up at the clinic for other issues, such as cataracts, he adds.
With World Glaucoma Week this year kicking off on March 12, it is an opportune time to raise awareness about the illness and the need for early detection.
"Glaucoma is progressive. That’s the biggest problem with it and if left undetected, it will lead to blindness given enough time. We want to find the disease in its earliest forms where it’s less visually debilitating and if we catch it then, we can usually do a good job of keeping that patient’s vision," says Assoc Prof Perera.
To detect glaucoma early, go for regular eye screenings if you're 40 and above, or earlier, if there is a known family history of glaucoma.
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