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.” — ***


3 responses to “Glaucoma: The sneak thief of sight

  1. Pingback: Glaucoma: The sneak thief of sight at Eye Care

  2. Pingback: Philippines » Blog Archives » Glaucoma: The sneak thief of sight

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