eye infection


What is glaucoma?

Glaucoma is a condition of the eye in which the pressure of the eye is too high and is associated with damage to the optic nerve. It is a common eye condition and unfortunately in many people it is undiagnosed.


What is the ‘intraocular pressure’?

The intraocular pressure, or IOP, is often referred to as the ‘pressure of the eye’. The eye is just like any ball and has a pressure. Normally the pressure will be around 15mmHg, and the accepted upper end of normal is 21 mmHg. When the pressure is too high, unusually it causes no symptoms. It does not cause pain or sensation of pressure, and in fact is typically picked up on routine examination by an optometrist or ophthalmologist. Common misconceptions are that it is associated with blood pressure (it is not), that it is associated with a watery eye (it is not).


Why does the eye have a pressure?

The eye produces its own nourishing fluid inside known as ‘aqueous’. It is produced by the ciliary body, circulates in the eye and is drained out of the eye via a structure known as the ‘trabecular meshwork’. The pressure is thought to be high in most cases of glaucoma because the drainage channels are not working correctly. Because the aqueous continues to be produced, the pressure of the eye increases.


What does happen when the pressure is too high?

When the pressure is too high, slowly over time it will damage the optic nerve. The optic nerve is that nerve that transmits the visual information from your eye to your brain and is visible to an eye specialist during examination. When this starts happening, the patient starts missing patches of side vision without realising it.


How is glaucoma diagnosed?

The commonest type of glaucoma is known as ‘Primary Open Angle Glaucoma’.

In order to make the diagnosis of glaucoma, 3 factors must be present:


  1. A pressure that is considered too high, usually over 21 mmHg.
  2. A optic nerve that appears ‘cupped’
  3. An abnormal visual field test result


A common question asked is whether glaucoma is hereditary. The short answer is yes, but not in a way in which it is automatically passed through the family. The normal population has a risk of developing glaucoma of 3 to 5 %, and if you have a first-degree relative with glaucoma, it makes your risk slightly higher, probably around 10%. So the odds are still with you. It is usually recommended to have a check at least around the age of 40, as glaucoma is rare at an age younger than this.



How do you treat glaucoma?

Glaucoma cannot really be cured, it can be controlled in the majority of cases. The usual treatments to be considered are:

  1. eye drops / tablets
  2. laser (argon laser trabeculoplasty)
  3. surgery

Most eye specialists would recommend trying eye drops before considering other more invasive treatments.

In theory, without treatment, an eye with glaucoma can go blind, but thankfully this is not common with modern methods. Usually things happen slowly with glaucoma, and vision is not usually lost quickly.

The key to glaucoma treatment is to lower the eye pressure so that it does not cause any further damage to the optic nerve. Once damage has occurred, typically it cannot be regained, even if the pressure is lowered to a normal level. The emphasis on treatment is not to regain lost patches of vision, but to prevent any further loss or progression to blindness.


What do I do if I have any further questions?

If you have any further questions, please feel absolutely free to ask. No question is too silly. It is important that every patient understands their disease so that it can be treated optimally. It is best to write down any questions and make sure that they are answered at the next appointment, or earlier if you are very concerned.