Glaucoma is the second leading cause of blindness in the world, mainly affecting the middle-aged and elderly.  Most forms of glaucoma are painless, and vision is usually preserved until the disease is relatively advanced, thereby giving rise to its infamous nickname – the “Silent Thief of Sight”.

normal nerve

Normal optic/ vision nerve

glaucoma nerve

Optic / vision nerve damaged by glaucoma

Glaucoma usually occurs when an increase in fluid pressure within the eye (intraocular pressure/IOP) damages the vision/optic nerve, which transmits impulses for sight to the brain. The nerve fibres in the retina may also be affected. As these changes are permanent, loss of vision from glaucoma is irreversible.  


  • Primary Open-angle Glaucoma
  • Primary Angle-closure Glaucoma
  • Secondary glaucoma
  • Congenital glaucoma


The ‘angle’ refers to the structures within the eye (including the trabecular meshwork) that allow the drainage of fluid (aqueous) from the front of the eye (anterior chamber).

  • Primary Open-angle Glaucoma (POAG) This is the commonest form of glaucoma and results from an excess of aqueous or a blockage in the trabecular meshwork, causing an increase in the IOP. The onset is insidious and the increase in IOP is slow. Patients usually do not experience any symptoms until the disease has progressed to a late stage.Initially, peripheral (side) vision and night vision are affected first; central or reading vision is only affected very late.Risk factors for POAG include:
    • Age above 40 years
    • Heredity (a positive family history of glaucoma)
    • Associated conditions like diabetes, high myopia, migraine, hypertension and those requiring the use of long-term steroids
    • Abnormalities in the eye structures
  • Primary Angle-closure Glaucoma (PACG) This type of glaucoma usually affects middle-aged to elderly Chinese women with. It is caused by an anatomical apposition of the iris onto the angle tissue, thus blocking the drainage of aqueous and increasing the IOP.

The IOP can rise gradually (and is therefore painless) or it can be sudden and acute.  This acute variety of angle-closure glaucoma is a true eye emergency, as the increase in IOP occurs suddenly and progresses rapidly. The symptoms include :

    • eye pain
    • redness
    • blurred vision
    • seeing haloes around light
    • headache and nausea
  • Secondary glaucoma.
    This results from the raised IOP caused by other conditions like tumours or inflammatory diseases of the eye, use of certain medications and injuries or surgery to the eyeball.
  • Congenital glaucoma.
    This occurs in infancy, childhood and adolescence and results from a developmental abnormality that blocks the aqueous outflow.


Glaucoma cannot be prevented. However, the earlier it is detected and the sooner treatment is started to reduce the IOP, the better the chances of slowing down its progression towards nerve damage and visual loss. Hence, regular eye checks for high-risk groups is recommended. The eye tests for glaucoma include IOP measurement, optic nerve structure and angle examinations as well visual field assessment.  These tests are painless and can be done in the comfort of the clinic.


There is NO CURE for glaucoma but there are effective means to control it. All methods are aimed at reducing and controlling the eye pressure such that visual loss is minimized. Your ophthalmologist will be able to advise on which treatment options are most suitable.

  • Medications, either oral or eyedrops.
    These help to lower the pressure in the eye by slowing the production of fluid or improving its drainage.
  • Laser surgery
    When medications are not sufficient to control the pressure, laser surgery can be employed to help the outflow of fluid. The methods are:

    • Laser trabeculoplasty, often used to treat open-angle glaucoma, in which the laser is used to widen the opening in the trabecular meshwork.
    • Laser iridotomy, used to treat closed-angle glaucoma, in which the laser makes a hole in the iris to improve the outflow of aqueous.


  • Conventional surgery.
    If medications and laser treatment are not successful, trabeculectomy can be performed. In this procedure, a new opening is created for fluid to leave the eye.

All the above-mentioned procedures are done on an outpatient basis. Due to the silent and progressive nature of glaucoma, lifelong monitoring and/or treatment is necessary for effective control of this condition and to preserve sight as much as possible.  It is important that patients understand their condition and the need for compliance to medication.