Glaucoma - The sneaky thief of sight
Eyesight of someone afflicted with an advanced stage of glaucoma.
Glaucoma is a condition afflicting the optic nerve, the "wires" that connect our eyes with the brain. When glaucoma sets in, it means that the optic nerves have been damaged, and as optic nerves do not have self-regenerating capabilities, the blindness caused by glaucoma is irreversible.While cataracts may be the leading cause of visual impairment, cataracts are treatable. On a global scale, glaucoma is the top cause of permanent blindness, and the bad thing is that it often afflicts the victim without much warning.
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The World Health Organization estimates that 4.5 million persons globally are blind due to glaucoma, and this number is expected to rise to 11.2 million by 2020.
It is believed that some 500,000 Malaysians have glaucoma, though accurate figures are hard to come by as not all choose to address the condition through mainstream healthcare providers.
In 2008, a total of 1,269 Malaysians sought treatment for glaucoma in Government hospitals, while 7,238 went to private doctors. "About 7 per cent of those who are visually impaired here have glaucoma," said Dr Mimiwati Zahari, an associate professor from University Malaya Medical Centre's Department of Opthalmology.
Low awareness
Some of the risk factors for glaucoma include ageing, existing shortsightedness (myopia) or longsightedness (hyperopia), history of steroid use (and not necessarily limited to those applied to the eye), diabetes, as well as being biologically related to those with glaucoma (hereditary factor).
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| Assoc Prof Mimiwati. |
Another survey found that the level of awareness among Malaysians compared with the rest of Southeast Asia was shockingly low, with 70 per cent of them not knowing what glaucoma was. As a result, a significant percentage of patients only see their eye doctors or specialists when their vision is already significantly impaired.
"Some patients come to see me after falling down staircases (cannot see the steps), or could not see the golf ball when teeing off. By then, it is really too late to save the sight that has been lost. The only course lies in managing the condition so that whatever sight that remains will be retained," said Assoc Prof Mimiwati, a glaucoma specialist who juggles teaching, research, and practising, in addition to volunteering her expertise at the Malaysia Glaucoma Society.
Different types
Glaucoma usually starts with the loss in the peripheral field of vision, and it need not necessarily affect both eyes at the same time. Even when the peripheral vision of one eye is gradually lost, a person might not notice it as the other eye is able to compensate for the slight loss, especially when it involves the most common form of glaucoma among Malaysians, primary open-angle glaucoma (POAG).
The next most common form of glaucoma is angle-closure glaucoma.
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| The most important risk factor for the development of glaucoma is the rise, whether gradual or otherwise, in the pressure within the eye, in what is known as intraocular pressure (IOP). |
Aqueous fluid is not to be confused with secretions from the tear ducts (tears).
IOP is measured in millimetres of mercury (mmHg), and the normal readings typically range from 10-21mmHg. A patient can have an elevated IOP but without evidence of optic nerve damage or visual field loss in a condition known as ocular hypertension.
In POAG, the aqueous fluid that normally circulates in the front portion of the eye is blocked from flowing out of the eye, causing the IOP to increase, and in turn, causing damage to the optic nerve. POAG can occur so gradually that it may take a few years before an individual notices any change to his field of vision.
In angle-closure glaucoma, the iris (the coloured part of the eye) may end up obstructing the drainage angle, when it is either pushed or pulled against the trabecular meshwork.
When the iris is pushed or pulled up against the trabecular meshwork, aqueous fluid cannot drain out, and this blockage can occur within a very short time frame. This is an emergency situation as optic nerve damage can occur hours after the blockage due to the rapid rise in IOP, which is normally accompanied by symptoms such as a splitting headache, nausea, vomiting, seeing halos or rings around lights, and intense pain in the affected eye.
In the case of angle-closure glaucoma, the IOP can shoot up as high as 50 to 60mmHg in a few hours. Even if treatment is provided, it is likely that lasting damage to the optic nerve would already have set in.
Angle-closure glaucoma is more common in women, and among Asians. Age can also be a factor: as people age, the lens of the eye enlarges and pushes the iris forward, thus increasing the risk for angle-closure glaucoma.
Sadly, people with normal IOP can still end up getting glaucoma in a condition known as normal tension glaucoma, where the optic nerve still ends up damaged even though there is nothing abnormal with the IOP readings.
This form of glaucoma is still not well understood, though evidence suggests that keeping the IOP on the lowering the IOP further has been shown to delay the progression of this form of glaucoma.
In rare cases, there are also forms of glaucoma that afflict the newly-born, such as congenital open-angle glaucoma, which often manifests itself in the first few years of life. There is a genetic basis for this as often there is already a strong family history of glaucoma. These children typically have enlarged eyeballs due to the high IOPs and do not respond well to long-term medical or laser treatment, and often require surgical intervention.
Regular checks
Assoc Prof Mimiwati also fingers the liberal ingestion or application of steroids as another risk factor in the development of glaucoma. "There are many people who use steroid eyedrops on a regular basis in their effort to self-medicate, usually for allergies. They go to the pharmacies, and get their supply, use them, and feel good getting a quick relief.
"But please remember to check your eye pressure, as many young people are going blind (from glaucoma) due to unsupervised steroid use. This is an important issue, and the Malaysian Society of Ophthalmology has raised the issue previously. Pharmacies should only sell steroids to those with prescriptions."
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| More focused screenings that target the at-risk groups such as the elderly, as well as those with the known risk factors should be carried out to curb the menace of glaucoma. |
When ocular hypertension is suspected or uncovered during screening, it does not necessarily mean that the individual is certain to develop glaucoma later on. However, he or she is advised to see an ophthalmologist so that the eye can be monitored to see whether there will be changes to the optic nerve as well as other parts of the eye.
The challenge does not end with picking up glaucoma, as the patient himself has a huge role to play in the successful management of his condition. Treatment is mainly managing the IOP so that it does not rise to critical levels. This is somewhat similar to hypertension or diabetes, where they need to be disciplined in their diet, exercise, and medication.
"Compliance is a huge issue, and the patient must be diligent in keeping to the treatment regime," said Assoc Prof Mimiwati, who revealed that some of her patients might have to apply up to four different kinds of eyedrops, some twice a day, and those on multiple drop need to instill them at least five minutes apart. "Furthermore, no immediate benefit is felt by those on treatment, and this worsens the compliance rate."
That said, there is no time to be lost in picking up those with high or borderline high IOPs, and this upcoming World Glaucoma Week is a good time to do so. Ophthalmologists recommend that those who are above 40, and have one of the risk factors mentioned above, undergo eye screening.
Other than picking up high IOP, eye screening for this group can also help in detecting other conditions such as cataract, age-related macular degeneration and diabetic retinopathy (among diabetics).