Glaucoma: The thief of sight

By Henrylito D. Tacio
* Names have been changed to protect privacy
George Javier didn’t think much was wrong when he woke up one Sunday morning in March 2003 with his right eye feeling, sore, heavy, and itchy.  It’ll get better once I wash my face, he thought while examining his reddish eye in the bathroom mirror.  “I took it lightly because the pain and itchiness were still tolerable,” admits Javier.
Since he was already scheduled for a party with his family and friends that day, he still went along.  While everyone where enjoying, it was a different story for Javier: his vision suddenly became blurred in his right eye, and everything he looked were foggy.  The following day, he consulted a doctor and was then hospitalised for further examination.  The diagnosis: glaucoma.
“I was totally shocked.  I never thought it would happen to me,” says the 63-year-old Filipino journalist.  “More shocking is the fact that glaucoma is so widespread in the country.”
There are 14 million people worldwide who have glaucoma, a debilitating eye disorder that can lead to blindness.  Glaucoma is a leading cause of blindness across Asia, topping the list in Hong Kong and coming a close second to cataracts in the Philippines. In Singapore, glaucoma accounts for 20 percent of blindness. 

Glaucoma is expected to become more prevalent, with the number of aging population in the region increasing.  “Glaucoma affects three percent of all adults above 40 years old,” says Dr Gerard Chuah, a consultant ophthalmologist at the Mt. Elizabeth Medical Centre in Singapore.
Unfortunately, half the people with glaucoma don’t know they have it because the condition usually destroys eyesight without warning and often without symptoms.  “It’s a slow, gradual disease that often goes undetected,” says Dr Manolette Roque, a consultant ophthalmologist at the Asian Hospital and Medical Center in Manila.
Glaucoma develops when the production of liquid in the eye (called aqueous humor) increases or the liquid is not drain adequately. The pressure rises in the eye to unhealthy levels. Nerve fibers and blood vessels in the optic nerve – which carries visual impulses from the eye to the brain – become compressed and can be damaged or destroyed.
At first, glaucoma damages peripheral vision.  Over time, glaucoma may also damage central vision and result in blindness.  Sight is lost slowly over many years.  “Should there be some hints, the patient may still doesn’t know since there is a lack of general knowledge about the symptoms of glaucoma,” says Dr Saw Seang Mei, associate professor of the department of community, occupational and family medicine at the National University of Singapore.
“Glaucoma is an important public health problem in Asia,” says Dr Chuah, the author of A Patient’s Guide to Glaucoma and Glaucoma Treatment. “Blindness due to glaucoma is irreversible, unlike other eye diseases such as cataract where some amount of vision can still be restored after a successful surgery.”
Although advancing age is the biggest risk factor, glaucoma can strike anyone. “Family history of glaucoma, especially first degree relatives, is one of the major risk factors for developing glaucoma later in life,” says Dr Liza Sharmini Ahmad Tajudin, a lecturer of the ophthalmology department at the Universiti Sains Malaysia in Penang.
Smoking, extended use of steroids, extreme nearsightedness (myopia), and previous eye surgery also increase the risk of glaucoma.  Ditto for diseases that affect blood flow to the optic nerve like diabetes, high blood pressure, and migraine. Sleep apnea, a sleep disorder that affects breathing and reduces oxygen thereby distressing the optic nerve, is another risk factor.

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 side vision, which glaucoma strikes first.

“Early detection of glaucoma is important because it is a blinding disease,” says Dr Maria Imelda Yap-Veloso, a Filipino ophthalmologist professor and a full-time consultant at the Asian Eye Institute in Makati City. “If glaucoma is diagnosed early, then the disease may be controlled and the visual complications from this disease may be prevented.”
Chronic glaucoma
Of the two major forms, acute and chronic, the latter affects about 90 per cent of sufferers.  Chronic glaucoma happens when the drainage canals in the eyes are blocked gradually slowly.  Symptoms include teary, aching eyes, blurred vision, occasional headaches, and progressive loss of sight.
Since chronic glaucoma attacks slowly, most people do not realise they have the problem until the disease has affected both eyes or they have an eye exam. That’s what happened to 45-year-old John Tan* from Singapore. Using an tonometer, his optometrist found high eye pressure and referred him to the Clearvision Eye Clinic. 
At the clinic, Dr Tony Ho dilated his eyes and examined the optic nerve with a hand-held ophthalmoscope. The ophthalmologist discovered Tan had moderately advanced glaucoma. The patient was surprised by the diagnosis but realized he had been bumping into things more often.  “It’s as if I’m looking at the world through a long, narrow tunnel,” Tan, a systems analyst, recalled.
“In clinical practice, there haven’t been many changes in the basic principles of the management of chronic glaucoma,” admits Dr Steve Seah, senior consultant and head of the glaucoma service at the Singapore National Eye Center.  “Our primary concern is to lower the high pressure in the eyes to prevent further visual field loss.”
Generally, medicines – in the form of eye drops – are the first line of treatment against chronic glaucoma. Oftentimes, doctors prescribe beta-blocker eye drops to lower liquid production in the eye.  “For many people, prescribed eye drops are enough to reduce eye pressure and prevent further loss of vision,” says Dr Roque of the Philippines.
“I recommended that he would undergo an eye drop therapy,” said Dr Ho of his patient, John Tan.  “I prescribed xalacom, which is a prostaglandin inhibitor and beta-blocker eye drops roll into one to control his eye pressures.  The root cause of glaucoma is an imbalance between the eye pressure and micro-blood supply to the optic nerve head.”
Topical drugs for glaucoma are serious medicine and they should not be confused with over-the-counter eye drops for easing common eye irritations.  Every year, new glaucoma eye drops are introduced into the market.  Among those currently available in Asia include alphagan, azopt, betagan, betoptic, cosopt, epifrin, isoptocarpine, lumigan, ocupress, pilogel, and propine.  “There is no single ‘best’ eye drop for glaucoma – all the latest eye drops have their advantages and side effects,” says Dr Chuah of Singapore.
In some instances, eye drops may not be enough.  In such case, the doctor may prescribe oral tablets or intravenous injection.  “Whether taken orally or injected, the drugs do not cure the disease but only reduce the ocular pressure and its fluctuations,” says Dr Liza Sharmini of Malaysia.
The two main oral medications prescribed by ophthalmologists are acetazolamide and glycerol. Likewise, there are two main intravenous medications recommended: intravenous acetazolamide and intravenous mannitol.  Patients must talk with their doctors and ask for possible side effects of these medications.
Prostaglandin analogues represent a new category of medications that have been commonly used for treating glaucoma since 1996.  Among those that are currently available in the market are latanoprost, bimatoprost, and travoprost.  These medications are administered once daily and do not have side effects.
“A person diagnosed to have chronic glaucoma should understand that this is a life-long disease,” reminds Dr Yap-Veloso of the Philippines. “It is not cured with any form of treatment but only controlled. Glaucoma patients should religiously use their anti-glaucoma drops as directed by their physician.”
That’s what John Tan is now doing.  “He has to take the recommended eye drops and medications throughout his life,” says Dr. Ho.
In cases where eye drops and drugs do not stop deterioration in the field of vision, surgical treatments become the treatment option of choice.  Trabeculectomy, the most commonly performed surgery for glaucoma, was developed in the 1950’s and the actual surgical technique has not changed much since that time. “However, there are ongoing modifications of surgical techniques to ensure greater safety and lower failure rates of surgery,” says Dr. Chuah of Singapore.
Surgical treatments are often performed with a local anesthetic and may require only a short hospital stay.  “The main purpose of surgery is to lower the eye pressure to acceptable levels, thereby preventing further optic nerve damage and arresting visual loss caused by the glaucoma,” explains Dr Chuah.
If surgery is not applicable, other options are available to destroy the cells that produce too much aqueous humor: ultrasound treatment (uses high-frequency sound waves), diathermy (heat), and cryosurgery (a freezing process).
Acute glaucoma
Although rare – about five per cent of all cases around the world – acute glaucoma causes far more rapid and permanent blindness if not treated immediately.  The most common form among Asians and people who are farsighted, this happens when the drainage canals in the eyes become blocked or covered.  Pressure in the eye rises rapidly, because fluid drainage is abruptly blocked while production continues.

Unlike the other type, acute glaucoma is usually accompanied by symptoms and affects one eye and rarely both eyes.  An abrupt onset of headache and pain around the eye and face, impaired vision, rainbow-colored halos around lights, and sudden loss of vision ensue.  There may also be nausea and vomiting.

“Acute glaucoma is an ocular emergency,” says Dr Zahari of Malaysia.  Adds Dr Ho of Singapore: “If not treated immediately, acute glaucoma results in complete and permanent blindness within two to five days.”

Fifty-four-year old Cherry Lee* is a high school teacher in Kuala Lumpur, Malaysia.  Last April, she felt a throbbing headache and severe pain in her right eye, which she thought was another migraine attack.  She went home early and took a long afternoon nap hoping it would disappear.  When she woke up, the problem got worse as she was already having trouble seeing. 

Lee never took it seriously and went back to school the following day.  Then, it recurred again.  While reading an essay written by one of her students, she could not read it thoroughly since the words were blurred.  This went on for more than a week and just took paracetamol to ease the pain.  But when her headache intensified and started to vomit after eating her favorite breakfast, she decided to see her doctor.  After hearing her woes, she was referred to an ophthalmologist, who diagnosed her of having acute glaucoma.

Oftentimes, doctors recommend the use the intravenous acetozolomide to decrease the liquid production. Although the drug can be taken orally and use as an eye drop, injecting it “is the fastest and most effective way to get a response, usually by half an hour,” says Dr Zahari.

That was what the doctor prescribed to Lee, along with topical eye drops timolol and pilocarpine.  Experts caution, however, that many of the drugs used for glaucoma interact with common medications.  Mannitol, for instance, is not advisable for patient with congestive cardiac failure or severe hypertension.

After the eye pressure came down, Lee went to a definitive treatment: surgery.  “The main objective in treating acute glaucoma is to prevent the recurrence of an attack,” reminds Dr. Zahari.  This can be achieved through iridotomy, where a small hole is placed in the iris to give way for the aqueous humor to drain thus relieving the pressure build up. This technique can be performed by laser surgery without making an incision in the eye.

There have been various studies on the ways to achieve an immediate reduction during an attack in acute glaucoma.  Doctors in Hong Kong, for instance, have tried poking a small hole in the cornea to let the liquid out slowly.  In Singapore, some doctors remove the lens as an early measure. “The difficulty in these methods is that the cornea is usually hazy due to the high pressure, so the view of the front eye is limited,” Dr Zahari reports. 

If acute glaucoma does not respond to any standard procedure, drainage implants may be used to drain the liquid. An implant, most commonly a half-inch silicone tub, is inserted into the eye’s anterior chamber.  Complications include cataract, implant failure, detached retina, breakdown of the cornea, bleeding complications, and double-vision. 
Another treatment is diode laser transscleral cyclophotocoagulation, which reduces fluid production by destroying the muscles that control the lens for near and far vision. There is a 20 per cent chance of vision loss with this procedure, so it is reserved for people with end-stage glaucoma or those who fail to benefit from any other therapies.
Again, the best defense against acute glaucoma is early detection.  “Medical treatment usually slows or stops it from worsening.  But whatever visual field a person has already lost can no longer be restored,” reminds Dr Chuah of Singapore.

On the Horizon 
Among the more promising treatments for glaucoma are gene therapies designed to relieve fluid pressure that leads to optic nerve damage in the eye or to protect the nerve from such damage. Another potential therapy involves newly discovered natural molecules that act to regenerate nerve cell growth in the optic nerve, thereby promoting vision recovery.
Many new glaucoma drugs – with higher potency and lesser side effects – have been introduced recently.  In Asia, the Singapore National Eye Center is involved in several clinical trials of these drugs.  “Drug-coated contact lenses that release drugs over a period of time is one possible development in the near future,” says Dr Seah.
In the laser front, newer laser that causes less destruction to the target tissue has already been launched.  “The results have been promising,” Dr Seah reports.
Still, early detection and treatment of glaucoma before it causes major vision loss is the best way to control the disease, points out Dr Roque of the Philippines. — ###


2 responses to “Glaucoma: The thief of sight

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