Saving sight
TELL glaucoma patients that they have green eyes and they would
protest. That's because glaucoma is known as qing guang yen in
Mandarin, which literally translates to "green light eye," says
consultant ophthalmologist Dr Chuah Kay-Leong.
The Chinese term for glaucoma is a misnomer and confusing. When Dr
Chuah mentions the word for glaucoma in Chinese to his patients,
they always brush it off. One patient says: "No, I don't see any
green light in my eye."
Then, Dr Chuah, a specialist in cornea, external eye diseases,
cataract and refractive surgery, has to explain what glaucoma
means. He has not the faintest idea how the Chinese term for
glaucoma came about.
Glaucoma is a disease in which the optic nerve is damaged, leading
to progressive vision loss. It is often associated with increased
pressure (intraocular pressure) of the fluid in the eye. Some
people develop glaucoma as a result of raised eye pressure. But
those with normal eye pressure can also end up with it because of a
weak optic nerve.
Untreated glaucoma
leads to permanent damage of the optic nerve, resulting in visual
field loss, which can lead to blindness.
"A patient diagnosed with glaucoma basically has too high a
pressure for the health of the eye. In the past, medical textbooks
state that eye pressure above 21mm Hg (millimetres of mercury) is
considered not good but this no longer holds true," says Dr
Chuah.
Normal eye pressure ranges from 10 to 21mm Hg. Ocular
hypertension is an eye pressure that is higher than normal, that
is, more than 21mm Hg.
Dr Chuah explains that a person with a healthy optic nerve can
"potentially" have higher eye pressure without damage to this
nerve. And the person does not have glaucoma even though the eye
pressure is above 21mm Hg. However, in an elderly person with poor
general health and a weak optic nerve, an eye pressure of 15mm Hg
or 16mm Hg could be considered damaging enough.
Hence, if eye pressure is deemed to be inappopriately high (even
if it's below 21mg Hg), it has to be brought down so that the optic
nerve does not get damaged.
"You look at the eye as a whole system. You've to find out how
healthy the nerve is, the level of the pressure and how the eye is
functioning in terms of visual field, to see if the person has
glaucoma," Dr Chuah says.
It is incorrect to assume that mostly the elderly have glaucoma
for Dr Chuah has had glaucoma patients in their 20s and 30s.
He says generally, patients diagnosed with glaucoma fear going
blind. "They are also concerned about their vision when they get
old and whether the condition will be passed down to future
generations."
Glaucoma is hereditary. If parents have it, the children need to
get their eyes checked.
One eye check is not enough to rule out if one is at risk of
glaucoma. Dr Chuah says a person after 40 should go for regular eye
checks every one-and-a-half years to two years.
The commonest types of glaucoma are open-angle glaucoma and
angle-closure glaucoma. The less common type is congenital
glaucoma, which occurs at birth or at the age of four or five.
There is also the "miscellaneous" group or secondary glaucoma,
caused by injury or eye diseases such as inflammation or
uveitis.
Dr Chuah says open-angle glaucoma and (most cases of) secondary
glaucoma tend not to show symptoms. People with these types of
glaucoma are most at risk because they could lose their vision
undetected. This is because their eye pressure is not very high and
glaucoma is detected upon incidental eye examinations. In some
glaucoma cases, one eye is already blind when the patient comes in
for consultation.
"The elderly patient may complain of blurred vision and thinks
he has cataract, which he does have a bit, but the (optic) nerve is
already damaged," explains Dr Chuah.
In angle-closure glaucoma, the symptoms are "very dramatic". Dr
Chuah says the patient would have pain and redness in the eye,
blurred vision and even blindness, sudden headache and nausea.
The reason why the Chinese are likely to get this type of
glaucoma is because they tend to have smaller eyeballs, concedes Dr
Chuah.
"People who are short-sighted (have bigger eyeballs) don't have
angle-closure glaucoma but people who don't wear glasses are more
at risk. Short-sighted people, however, are at risk of open-angle
glaucoma, which is a silent disease."
He says incidences of open-angle glaucoma are more common in the
West. "In Asia, we get quite a lot of angle-closure glaucoma."
Dr Chuah warns that angle-closure glaucoma is one of the major
eye emergencies. "If your eye pressure tends to be very high, at 30
or 40mm Hg, you tend to have severe pain in the eye. If you don't
bring the pressure down within three or four hours, your chances of
salvaging the eye is gone (because the optic nerve is
damaged)."
If such symptoms occur, don't wait until the following day or
the weekend to see the eye doctor, he advises. "Seek emergency eye
care straightaway at the general hospitals (with 24 hour service)
because there won't be doctors in eye clinics at night. The pain
usually affects one eye but the pressure in both eyes is high. I've
seen bilateral attack (pain in both eyes) involving an elderly
Indian woman in the hospital, but that's extremely rare."
The earlier the condition is diagnosed, the greater the chances
of success in preventing further visual loss, he says.
"Although the damaged nerve fibres and their lost function cannot
be recovered, as long as the glaucoma is controlled, further damage
can be avoided. The type of treatment depends on the form of
glaucoma one has. It comprises medications (eye drops and tablets),
laser and surgery."
Treatment for glaucoma is to bring the eye pressure down quickly
to stop progressive damage to the eye.
"If the pressure is not too high, the patient is given eye
drops. If the pressure is high, tablets (Azetozolamide) and
injection (IV mannitol) are given. Most eye drops prescribed are
for use once, twice or thrice a day. They are to be used daily for
the rest of your life."
For angle-closure glaucoma, eye drops are given to keep the
pressure low once it has been brought down, Then, the patient can
go for YAG laser peripheral iridotomy (to create a hole in the iris
to make another channel for the eye fluid circulation) and
eventually, surgery to remove the eye lens (as in cataract surgery)
to create more space for the eye.
In angle-open and secondary glaucoma, the patient will be given
eye drops to reduce the eye pressure by reducing aqueous (fluid in
the eye) production or increasing outflow of the fluid from the eye
or a combination of both procedures.
After successful treatment, having normal eye pressure means the
glaucoma is controlled, and further visual deterioration has been
halted.
Dr Chuah says that, however, this does not imply that the
glaucoma has been cured. "The patient has to go for follow-up
checks on a regular basis to ensure the optimum eye pressure is
maintained to prevent progressive damage to the eye."
He advises glaucoma patients to practise compliance in taking
medication, attend follow-ups and have their eye pressure checked
on a routine basis.
"Compliance in taking medication is an important regime to
follow. If you don't use the eye drops for a few days, the pressure
goes up and your nerve may be damaged. You don't want that," he
says.