Generally undiagnosed in its early stages, glaucoma is a group of diseases that damage the eye’s optic nerve. Because symptoms usually only appear once some damage has already been done, it can result in vision loss and, in severe cases, blindness. Yet once it’s diagnosed it can be treated, preventing further damage.
“Glaucoma is classically caused by raised pressure in the eye that’s above the usual physiological level,” says Professor Grant McLaren, an ophthalmologist at The Wits University Donald Gordon Medical Centre. “This causes damage to the nerve fibre layer.” Regardless of the type of glaucoma you have once the nerve fibres are damaged, irreversible vision loss results. That’s why early detection is so important. Professor McLaren also emphasises the importance of seeing an eye specialist and of educating yourself about the disease so you’re able to ask the right questions.
Different kinds of glaucoma
There are two general types of glaucoma: (primary) open-angle glaucoma and angle-closure glaucoma. Yet there are also numerous variations.
Primary open-angle glaucoma (POAG) is the most common form of glaucoma and is caused by raised pressure in the eye. This pressure results when the eye’s drainage canals become blocked causing eye fluid pressure build-up that damages the optic nerve. “This can go undetected and accounts for half the people who have a problem initially,” says Professor McLaren. “It is diagnosable, however – patients won’t have raised pressure when you first measure their eyes but if you challenge them with a water test – where they drink a litre of water – their pressure will spike.” In POAG, patients lose peripheral vision. “So, they don’t know they’re getting tunnel vision – they’re not losing their central vision. By the time their central vision is affected, it’s too late.”
“We usually see high-pressure glaucoma in our African population, where they generally have high pressures on presentation,” he adds.
Normal tension glaucoma: Also known as paracentral glaucoma, this affects your central vision. “Here pressure is in the normal range and you can’t provoke a spike by doing a water test,” says Professor McLaren. “But it is typical in its presentation, so it can be diagnosed. The damage happens in the area around the point of fixation where your fovea is – a tiny pit in the macula of the retina which provides your clearest vision. In these cases, early damage to your central vision occurs.”
Angle-closure glaucoma: This occurs when the fluid at the front of the eye cannot drain through the angle and leave the eye because the peripheral iris is bunched up in the angle, according to the National Eye Institute. Liquid outflow is therefore blocked. People with this type of glaucoma may have a sudden increase in eye pressure which can cause blindness. If you have a red painful eye, blurred vision, nausea, vomiting, and headache see your doctor immediately.
Congenital or developmental glaucoma: This happens because of malformation of the drainage channels in the eye. It’s usually evident either at birth or during the first year of life.
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Symptoms to look out for
“There are no early symptoms of POAG,” says Professor McLaren. “Most people won’t pick up a visual field defect until they’ve lost half of their nerve fibres. The only time symptoms are noticed is when the patient has already lost some of their peripheral vision, which is what alerts you to danger. They realise they don’t see things coming from the side or they’re bumping into things. So, glaucoma affects their quality of life early on – even they don’t know it consciously, subconsciously they realise they don’t have the same level of confidence.”
Treatment options
Glaucoma is very much treatment-dependent, says Professor McLaren. “It’s a blinding condition so to preserve vision, pressure needs to be controlled and kept in the normal range. You can halt the progression, but you can’t reverse the damage.” Treatment therefore focuses on controlling the pressure in various ways. Options include:
Drops: Here eye drops need to be inserted regularly into the eyes and compliance is essential. If you forget to take your drops, pressure spikes causing nerve damage.
Laser: Selective laser trabeculoplasty is done in the doctor’s rooms and helps fluid drain out of the corner of the eye. “In glaucoma, laser is a very good first option, but it’s not always used as drops are seen as less invasive,” Professor McLaren says. “Yet compliance with taking drops is a major challenge, so laser is preferable.”
Operation: If the pressure is still not lowered from laser and medication, you need to have surgery. In this surgery, called a trabeculectomy, the doctor makes a new opening for the fluid to leave the eye. There are other surgical innovations and devices that can be employed to similarly lower pressure.
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