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By: Dr Yeoh Phee Liang


Glaucoma is the silent thief because it can slowly steal your sight before you realize it. It leads to blindness. Before the silent thief creeps in, enrich yourself with the important information.

In the normal eye, there is a delicate balance between the inflow and outflow of aqueous (fluid in the eye). When the outflow is blocked, the intraocular pressure rises, leading to optic nerve damage. This condition is known as glaucoma. This will correspond to progressive visual field defect that ultimately lead to tunnel vision. Vision is never affected unless the intraocular pressure in the eye is elevated acutely. Susceptibility of individual to damage caused by eye pressure is variable. The diagnosis of glaucoma can only be made when there is definite visual field defect, cupping of the disc which can be visualized through the pupil and an eye pressure that is deemed to be harmful to the eye.

The diagnosis of glaucoma is complex when the disease is less advanced. The eye pressure in the eye is normally measured to be less than 20 mmHg, and is likely to fluctuate a little at different time of the day. Suspicion of glaucoma is raised when the pressure exceeds 20mmHg but some may be affected at lower pressure than that. Owing to this diverse variability, eye pressure alone can never confirm the diagnosis. To add on to this variability is the appearance of disc cupping. A cup/disc ratio of about 0.6 or greater may arouse suspicion of early glaucomatous damage. In eyes with small disc, glaucoma may be present with a much smaller cup/disc ratio.

No individual must be labeled as ‘you have a touch of glaucoma’. Diagnosis must only be made when the evidence is firm as therapy falls between medication which is the application of very expensive eye drops for life or invasive surgery. When therapy is implemented, it is to halt the diseases progression but not to reverse the lost visual field at whatever status it may be. When the diagnosis is vague, regular careful monitoring must be implemented.

Classification of glaucoma is very diverse. There are two main types of glaucoma:

  1. Open-angle glaucoma which develops insidiously and leads to visual field loss with few or no symptoms.
  2. Closed-angle glaucoma which develops suddenly is associated with acute pain, sudden visual loss and congestion of the eye. Because of the congestion, acute closed-angled frequently presents as a unilateral red eye.

Broadly speaking, ‘open-angle’ refers to normal out flowing of fluid and ‘closed-angle’ when the out flowing channel is blocked. Primary open-angle glaucoma (POAG) refers to the disease unrelated to any underlying causes and secondary to those with underlying problems such as trauma, steroid usage, inflammation of the eye and others. Primary closed-angle (PCAG) refers to the disease unrelated to any underlying causes and secondary to those with underlying problems such as new vessels formation caused by diabetes and central retinal vein occlusion in high blood pressure, inflammation blocking the out flowing drainage, tumour, thyroid eye disease, enlarged cataract and others.

A family history of POAG, particularly in first-degree relatives, is associated with an increased risk of developing the disease. POAG is more common than PCAG among Caucasians. Diabetes and short-sightedness appear to be associated with a greater risk of POAG. PCAG is more come in Asian descent. This risk is more prominent with age. Steroid eye drop is a common drug prescribed. Over usage without proper supervision will lead to glaucoma and cataract. This is a very common and severe with irreversible outcome when patient is self prescribing. Glaucoma causes ten percent of blindness in most countries.

When the pressure is elevated to a level such as 20-30mmHg, the disease is a silent killer as visual field slowly deteriorates without symptoms. Both primary and secondary open-angle glaucoma fall into this group. Patients normally present knocking into doors, falling, failing to acknowledge friends signaling from across the road or the disease is picked up during screening. Vision is never affected unless the intraocular pressure spikes to a considerable level to as high as 40-50mmHg or more. Close-angle glaucoma normally presents with creeping pressure initially without any symptoms to symptoms of pain, headache, visual loss, blurred or boggy vision, coloured haloes around lights, redness, or photophobia. PCAG is more likely to be prominent under dim room light when the pupil is dilated, narrowing the already compromised drainage angle. PCAG normally presents acutely with severe pain, red eye and visual loss.

Treatment of glaucoma is rather complex and ranges from

  1. Topical eye drops and oral therapy
  2. Laser therapies
  3. Surgery to create a bypass passage to facilitate the out flow.

First line of treatment for open-angle glaucoma is topical eye drops. If the condition is still not well controlled, then drainage surgery to bypass the out flow is called for.  PNAG is a medical emergency that require immediate topical and oral medications followed by laser application to clear the blockage at the iris level. Another form of laser usage is pan retinal photocoagulation which is used to apply on the retinal to increase oxygen supply and hence eliminate the new vessels formation blocking the drainage angle. There are also other more specific types of laser which can also be used in selected forms of glaucoma.

Whichever form of therapy is selected, the ultimate goal is to lower the eye pressure to a ‘target pressure’ in order to halt the damage of visual field loss and also to eliminate the underlying causes such as new vessels formation in diabetes, tumour, inflammation, hypertension and many others. Advance technology to detect the stage before definite irreversible damage to the visual field is showing promising result. This is likely to rise to the horizon and available widely in time to come. Regular screening for at risk patients is called for and diagnosis of glaucoma must only be made with strong evidence. Treatment is warranted with definite cases but full recovery result must never be misled to the patients.
For further information please contact:
Dr Yeoh Phee Liang, Advance Vision Eye Specialist Centre, Tel: +603 - 7724 1392
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