Glaucoma is a disease that damages your eye’s optic nerve, the neural “signal cable” that allows the visual information from the eye to be transmitted to the brain so that you can see. Glaucoma results in progressive loss in your peripheral or side vision, and can eventually cause blindness. With early detection and treatment, the eye sight can often be protected.
Image from American Academy of Ophthalmology: Glaucoma
Glaucoma is usually caused by higher pressure inside the eye (intraocular pressure or IOP), which causes stress on the optic nerve and thus progressive loss of the nerve fibres. The eye is like a balloon, filled up with fluid called the aqueous humor, which is in a constant state of secretion inside the eye and balanced drainage out from the eye. If this balanced state is disturbed because the drainage pathway is not working properly (like clogged up kitchen sink drain), the fluid inside the eye and eye pressure builds up. Similar to high blood pressure being not good for your cardiovascular health, having high eye pressure is unhealthy for your eye.
Some people have a higher than normal risk of glaucoma. The known risk factors include:
There are two major types of glaucoma:
1. Chronic open-angle glaucoma
This is the most common type of glaucoma. It happens gradually and so in most cases, there is no symptoms. This type of glaucoma is painless and causes no noticeable vision changes until it is much more advanced. Some people can also have a type of glaucoma called “normal tension glaucoma”, where the eye pressure is not high but their optic nerves are susceptible to even what we consider to be “normal” eye pressure. Often, such patients with glaucoma also have a wider fluctuations in their eye pressure from different times of the day or from day to day.
2. Angle-closure glaucoma (also called, “acute narrow-angle glaucoma”)
This type of glaucoma is less common and happens when someone’s iris (the coloured part of the eye) is very close to the drainage angle in their eye. The iris can end up blocking the drainage angle (“angle closure”) and the eye pressure rises very quickly. In this type of “acute glaucoma”, there is very high eye pressure that causes symptoms such as eye pain and blurred vision. This is an eye emergency that can lead to blindess and so you need to seek urgent eye specialist treatment.
In chronic angle-closure glaucoma, a similar problem with narrow angles results in a very slow and gradual closure of the drainage angle. This results in gradual rise in the eye pressure and there is no symptoms at first.
Glaucoma can only be diagnosed after a complete eye exam by your optometrist or your eye doctor. It is vital to have such examination regularly in persons with risk factor(s) for developing glaucoma, because there is no symptoms or warning indications at all for most forms of glaucoma. Early diagnosis is important because appropriate treatment can prevent vision loss from glaucoma but in contrast, there is no way to recover lost vision from advanced glaucoma damage that has been detected too late.
Some of the tests performed in a glaucoma examination by your eye specialist include:
The main way of treating glaucoma is to lower the intraocular (eye) pressure (IOP). There is no magic number for an acceptable IOP but the aim is to lower the eye pressure to a safe level for your eye so that further damage to the optic nerve is stopped. Your ophthalmologist may use one or more of the following treatments to treat your glaucoma.
Glaucoma eye drop medicine
This is the most common form of treatment for glaucoma. There are various eye drop medicines available. They work in slightly different ways but their shared goal is to lower the eye pressure, by either reducing the amount of fluid secreted into the eye or helping fluid flow out better from the eye. Glaucoma eye drops need to be used every day as there is currently no cure for glaucoma. Depending on the severity of your glaucoma, a combination of the eye drops may be used to achieve even lower eye pressure. All medications can have side effects, even eye drops, and your doctor will explain these potential side effects to look out for and monitor your response to treatment. Some of the side effects from glaucoma eye drops include red or itchy eyes, but be aware that some are remote from the eye such as shortness of breath.
There are two main types of laser treatment for glaucoma. These treatments are very safe, painless and can be done in the clinic by your eye doctor (does not need hospital admission).
1. Trabeculoplasty or SLT laser
This treatment is for people who have open-angle glaucoma. The laser helps to make the drainage angle work better and hence lower the eye pressure. This is particularly useful for persons who have multiple allergies to glaucoma eye drops or those who are not good at remembering to use the eye drops every day.
2. Laser iridotomy
This is for people who have angle-closure or narrow angle glaucoma. The laser treatment creates a tiny hole in the iris to help fluid flow to the drainage angle. Laser iridotomy can also be performed as a preventative treatment for particularly predisposed persons so that they are protected from developing glaucoma later.
Minimally Invasive Glaucoma Surgery (MIGS)
(such as microtrabecular glaucoma stent implants)
This is a relatively new form of glaucoma treatment, which has been shown to be safer than the more traditional glaucoma surgery and are particularly useful for patients with mild to moderate severity glaucoma. Micro-trabecular glaucoma stents (such as Glaukos iStent inject) are implanted into the drainage angle, allowing improved outflow of the fluid from inside the eye with resultant lowering of the eye pressure. One of the added advantage of such MIGS surgery is that they can be safely performed at the same time as your cataract surgery, without the need for a separate procedure. Dr John Chang can assess and explain whether you would be suitable for this type of combined cataract and glaucoma micro-stent implant operation.
(such as trabeculectomy or glaucoma drainage tube devices)
Traditional glaucoma surgery involves creating a new drainage channel for the aqueous humor to leave the eye. This type of surgery is often the most effective way of achieving a very low eye pressure, which is needed for more severe or advanced glaucoma. As effective as they are, such surgery however also has relatively higher chances of problems arising from the procedure and so these are generally reserved as the last option after the above medical and laser treatment options have been tried first.