Untreated, it can lead to progressive and irreversible loss of vision and is one of the four most common causes of blindness worldwide, along with diabetes, cataracts and age-related macular degeneration. The good news, however, is that it is eminently treatable so long as it is diagnosed early.
“There is more than one type of glaucoma, but the most common type seen in South Africa is called chronic open-angle glaucoma,” says Dr Nicky Welsh, senior ophthalmologist at Charlotte Maxeke Johannesburg (CMJ) Academic Hospital and clinical head, Wits Donald Gordon Medical Centre.
“It affects black and whites and males and females equally, although it often manifests in blacks at younger ages than it does in Caucasians. We're still not sure of what causes it, although we do know that the likelihood of developing glaucoma is higher in diabetics, those who are short-sighted and where there is a family history of the condition. There was a time 30 years ago when we thought entirely in terms of pressure within the eye - and glaucoma is commonly associated with raised intra-ocular pressure - but we also encounter optic nerve damage in the presence of normal pressure and sometimes an absence of damage when the pressure is raised. We now know that glaucoma is a spectrum, that ‘normal' is not absolute and that pressure is just one risk factor, albeit an important one.”
Dr Welsh underscores that this raised pressure within the eye is not blood pressure. Rather it's the result of a build-up of a fluid in the eyeball called aqueous humour. In the normal eye, a balance is maintained between what is produced and what is excreted. When this balance is disturbed, fluid builds up in the eye, raising the pressure and making the eye ‘hard'. This pressure is transmitted to the optic nerve, damaging it and causing changes to the field of vision. Because these changes are slow and insidious, those with glaucoma are often unaware they have it until it's fairly advanced.
“This is one of the biggest problems. Glaucoma is usually painless and progresses slowly. Patients may only become aware of their worsening vision once there is already considerable damage to the optic nerve. The peripheral vision is lost first, leading to ‘tunnel vision' as the visual field becomes restricted. Because the central vision is not affected at first, those with glaucoma often fail to perceive a problem. However, if left untreated, it too will eventually be lost, leading to total blindness,” says Dr Welsh.
Dr Neelay Ranchhod, product physician at Pfizer SA says, “Because it is initially without symptoms, glaucoma is often diagnosed coincidentally, by someone like an optometrist or ophthalmologist, given that measurement of eye pressure is usually part of routine examinations.”
Dr Welsh underscores the importance of routine screening. It is particularly important in people over 40 - the incidence of glaucoma rises with age - and in those where there is a family history. “We advise the general public to be screened once a year from the age of 40, but where there is a possible genetic predisposition, this annual screening should start between the ages of 25 and 30.”
The pressure in the eye varies in the course of the day - it's usually highest in the early morning and lowest in the late afternoon. “To make a definitive diagnosis, it may be necessary to measure the pressure at different times of the day to assess the changes and fluctuations,” says Dr Ranchhod.
Glaucoma is not preventable. “There's nothing you can eat, take or do to ensure that you never develop it,” observes Dr Welsh. “It can happen to anyone, so awareness is crucial. Early diagnosis is imperative. Once the optic nerve is damaged, that damage cannot be reversed. However, glaucoma is treatable and so long as patients comply with that treatment, the process of decline can be arrested.”
Medical treatment with eye drops is the most common. The severity of the condition determines what is prescribed. “The drops lower pressure, whether by increasing the outflow or cutting the production of aqueous humour. The target pressure differs from patient to patient and there is no hard and fast rule. However, we generally take the view that the lower the pressure, the better.”
In extreme cases, where the drops don't work or patients are allergic to them, glaucoma sufferers can undergo so-called ‘filtration surgery'. Dr Welsh emphasises that medical treatment is always the first choice, however, and surgery is usually a last resort. That's because it's unpredictable. Sometimes it works well; sometimes it doesn't work at all. Sometimes it works at first, but then stops. There are even times when it works too well, and the patient ends up with dangerously low pressure. “It's also very important to make the patient understand that filtration surgery is not like cataract surgery, which is done to improve the vision. Assuming it works, it will only maintain the vision as it is and prevent it from worsening.”
In summary, glaucoma is a potentially serious condition, but it can be managed and treated, allowing the patient to live a normal life, provided it is diagnosed early. “Regular check-ups are therefore essential, even if nothing is seemingly wrong,” concludes Dr Welsh.
Pfizer South Africa
Solly Mabotha
Pfizer Public Relations Manager
www.pfizer.com
