Wellbeing / 25 May, 2020

Glaucoma, the ‘silent thief of sight’

Dr Lau Pik Onn

What is glaucoma?

Glaucoma is an eye condition which is characterised by loss of vision, caused by damage to the optic nerve. We have one optic nerve in each eye that transmits information (that we see) from our eyes to our brain. In glaucoma, damage to the nerve is caused by raised pressure within the eyeball. This damage to vision usually happens so slowly that you do not notice the gradual loss until it is in the advanced state, and hence it is also called the ‘silent thief of sight’.

Glaucoma is the leading cause of irreversible blindness. About 60% of glaucoma patients live in Asia.1

In Singapore, glaucoma affects about 3% of those aged above 50 and the risk increases with age, with almost 10% of those over the age of 70 developing glaucoma (based on a 2009 study by the Singapore Eye Research Institute).

Glaucoma accounts for around 40% of blindness in Singapore.2

As visual loss due to glaucoma cannot be recovered, it is important to have regular eye exams that include measurement of eye pressure (tonometry) to ensure you are diagnosed early. This can be done as part of your health screening at Icon Health Screening.

Causes of glaucoma

The eye is like a ball filled with fluid which provides oxygen and nourishment to the rest of the eye. It has an inflow tap and outflow drain. For normal eye pressure, the inflow must balance the outflow.

In glaucoma, the fluid pressure in the eyeball becomes too high for the optic nerve to tolerate, due to an imbalance between the production and drainage of fluid within eyeball.

Types of glaucoma

There are many different forms of glaucoma.

Open angle glaucoma

  • This is the most common form of glaucoma and symptoms are often gradual. You may not notice vision loss until glaucoma is advanced
  • It mainly affects the middle aged and elderly and progresses slowly and painlessly
  • Peripheral and night vison tend to be affected before central reading vision

Closed-angle glaucoma

Closed-angle glaucoma can either be acute or chronic:

  • Acute angle-closure glaucoma presents with a sudden increase in eyeball pressure in one or both eyes, resulting in a sudden onset of pain, redness, blurred vision, and halos around the lights. It may also be accompanied by headaches, nausea, and vomiting. Urgent treatment to lower the eye pressure is essential to save your vision.
  • Chronic angle-closure glaucoma may be asymptomatic and progresses gradually, often unnoticed for a long time. This is due to a progressive blockage of drainage channels in the eyeball, resulting in a slow and prolonged rise in pressure

Secondary glaucoma

  • This occurs when other eye diseases cause an increase in eye pressure, leading to optic nerve damage (e.g. tumours, injuries, advanced cataract)
  • It can also be related to other medical conditions (e.g. poorly controlled diabetes)

Congenital glaucoma

  • This is a rare form of glaucoma and occurs at birth
  • In the case of congenital glaucoma, the infant’s eyes will be enlarged with symptoms including a hazy appearance of the cornea, tearing up and sensitivity to light
  • Urgent eye examination and treatment is needed to prevent blindness

What puts you at higher risk of glaucoma?

  • Family history of glaucoma
  • Age (risk increases above age 50)
  • Coexisting medical conditions (particularly if you have diabetes or hypertension) and eye conditions including high short sightedness and previous eye injuries
  • Ethnicity (Asians are more susceptible to angle-closure glaucoma than Caucasians)
  • Use of corticosteroids

How is glaucoma diagnosed?

Diagnosis of glaucoma will be made by an eye specialist following a comprehensive eye examination and investigation.

Tonometry (commonly known as ‘eye puff’) is a diagnostic test that measures the pressure inside your eye, also known as the intraocular pressure (IOP). This can help determine whether you may be at risk of glaucoma.

Normal eye pressure ranges from 10 to 25mmHg, and this can vary throughout the day. If your eye pressure is above 21mmHg during the tonometry test, you will be referred to an eye specialist for further evaluation and additional specialist tests may be performed like Gonioscopy, visual fields and optic nerve assessment.

Why is early detection important?

Worldwide, over 90% of people suffering from glaucoma are unaware of it at the time of diagnosis as the condition is largely asymptomatic.2 Glaucoma is not curable, but blindness is preventable if diagnosed and treated at an early stage. Once the optic nerve is damaged, loss of vision is permanent.

The aim of early detection and treatment is to lower the intraocular pressure to an acceptable level and prevent further damage to the nerve. If glaucoma is detected early, vision loss can be slowed or prevented.

What is the treatment for glaucoma?

Treatment will depend on the type of glaucoma and can be classified into:

  • Medical (including anti-glaucoma eye drops and oral medication)
  • Surgical (if medical treatment with anti-glaucoma eye drops fail, e.g. trabeculectomy)
  • Laser (usually for patients with angle-closure glaucoma)

References

For a full list of references, click here.
  1. Chan EW, Li X, Tham Y, et al. Glaucoma in Asia: regional prevalence variations and future projections. British Journal of Ophthalmology 2016:100:78-75.
  2. SingHealth. (2018). Glaucoma. Retrieved on 5 May 2020 from https://www.singhealth.com.sg/patient-care/patient-education/glaucoma
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