Glaucoma: The sneak thief of sight

HEALTH:

GLAUCOMA: THE SNEAK THIEF OF SIGHT

By Henrylito D. Tacio


IT may not be as popular as cataract but glaucoma is
also a blinding disease. “Glaucoma is not as common
as cataract but it is also not rare,” says Dr. Maria
Imelda Yap-Veloso, a full-time consultant at the Asian
Eye Institute in Makati City.

According to a recent survey by the Institute of
Ophthalmology of the University of the Philippines,
glaucoma is the second leading cause of blindness in
the country. Affecting 100,000 Filipinos, it is the
third most common cause of visual disability.

Glaucoma is considered “the sneak thief of sight.” As
Dr. Narciso F. Atienza, a diplomate of the Philippine
Board of Ophthalmology puts it: “Many people in the
early stages of the disease do not notice symptoms
until eye damage becomes so severe, it is impossible
to repair. Every year, many Filipinos needlessly go
blind because their glaucoma was detected too late.”

“Most blindness from glaucoma is needless and could
have been prevented if detected and treated in time,”
pointed out Dr. Robert Ritch, a professor of clinical
ophthalmology at the New York Medical College.

Because of this, Dr. Manuel B. Agulto, chair of the
ophthalmology and visual sciences department of the
University of the Philippines College of Medicine,
urged Filipinos to have regular eye checkups with an
ophthalmologist. “People aged 40 and above at risk
for glaucoma should have their eyes examined by an
ophthalmologist once or twice a year,” he advised.

Glaucoma occurs when an imbalance in production and
drainage of fluid in the eye (aqueous humor) increases
eye pressure to unhealthy levels. “Normally, the
aqueous fluid, which nourishes the eye, is produced by
the ciliary body behind the iris (in the posterior
chamber) and flows to the front of the eye (anterior
chamber), where it drains into drainage canals between
the iris and cornea,” states the second home edition
of ‘The Merck Manual of Medical Information.’

Explaining further, the Merck manual informs: “When
functioning properly, the system works like a faucet
(ciliary body) and sink (drainage canals). Balance
between fluid production and drainage – between an
open faucet and a properly draining sink – keeps the
fluid flowing freely and prevents pressure in the eye
from building up.”

In glaucoma, the canals through which the fluid drains
become clogged, blocked, or covered. Fluid cannot
leave the eye even though new fluid is being produced
in the posterior chamber. In other words, the sin
“backs up” while the faucet is still running. Since
there is nowhere in the eye for the fluid to go, the
pressure in the eye increases.

“When the pressure becomes higher than the optic nerve
can tolerate, glaucoma results,” the Merck manual
says. “Sometimes eye pressure increases (called
intraocular pressure or IOP) within the range of
normal but is nonetheless too high for the optic nerve
to tolerate.”

Aside from being old, others who are considered at
risk for glaucoma those with a family history of
glaucoma, diabetic patients; nearsighted patients;
those with a history of eye injury; and those using
steroids (as maintenance medication) for asthma,
lupus, allergies, and skin problems, including
athletes.

Smoking and high blood pressure are potential risk
factors. Having a sleeping problem like sleep apnea
is another one. Hours in front of a computer screen
may increase the risk of glaucoma in people who are
shortsighted, according to a recent study in Japan.

There are two major forms of glaucoma: acute and
chronic. Chronic glaucoma, the most common, develops
slowly and symptoms include teary, aching eyes,
blurred vision, occasional headaches, and progressive
loss of sight. “This type of glaucoma first affects
the side vision then slowly works it way to the center
of a person’s vision,” says Dr. Veloso.

While acute glaucoma is rare, it causes far more rapid
and permanent blindness. This occurs if the pupil in
an eye with a narrow angle between the iris and cornea
opens too wide and causes the folded iris to block the
flow of aqueous humor. As it happens suddenly, this
is an emergency condition. Early symptoms include
extreme eye pain, blurred vision, a red eye, and
headache (oftentimes misdiagnosed as migraine).
Nausea and vomiting may occur.

“If not treated immediately, acute glaucoma results in
complete and permanent blindness within two to five
days,” cautions Dr Tony Ho, an ophthalmologist and
director of Clearvision Eye Clinic in Singapore.

Going for regular eye examinations is the best way to
detect glaucoma early, “A glaucoma test usually
includes an optic nerve check with an ophthalmoscope,
eye pressure check or tonometry, and, if necessary, a
visual field assessment that tests the sensitivity of
peripheral or side vision, which glaucoma strikes
first,” said Dr. Agulto.

Although there is no cure for glaucoma, the good news
is that the disease can often be controlled. The most
common treatment for chronic glaucoma is a regimen of
drugs to lower the IOP by either promoting the outflow
of aqueous humor or decreasing its production. For
most patients, these drugs consist of topical agents
available as eye drops. The principal agents used
include beta-adrenergic blockers, carbonic anhydrase
inhibitors, prostaglandins, adrenergic agonists, or
cholinergics.

In the case of acute glaucoma, doctors will most often
prescribe drugs that suppress the symptoms of
glaucoma, and then follow this treatment with
corrective surgery. For example, a patient will both
receive drugs that reduce IOP and undergo laser
surgery to alter the iris and facilitate aqueous humor
outflow.

“A person diagnosed to have glaucoma should understand
that this is a life-long disease,” reminds Dr. Veloso
of the Philippines. “Glaucoma is not cured with any
form of treatment but only controlled. Glaucoma
patients should religiously used their anti-glaucoma
drops as directed by their physician. They should
regularly see their doctor for their follow-up visits
to ensure that the disease is well-controlled.” -- ***