What is glaucoma of the eye?

From the etymological root word Glaukos (Ancient Greek) meaning grey, blue or green, glaucoma is a common eye condition. It impacts an estimated 2% of people over the age of 40 in the UK, rising to 10% of people over 75 years old, and it is one of the leading causes of blindness in the UK and globally.

Due to the asymptomatic nature of glaucoma in often showing little to no symptoms, it is commonly referred to as the ‘silent thief of sight’.

In this blog, we look at what glaucoma is exactly, the different types of glaucoma and how it takes effect.

What does glaucoma affect?

Glaucoma is a category of conditions which causes progressive damage to the optic nerve at the back of the eye. It is sensitive to eye pressure, causes characteristic visual field defects and is capable of permanently blinding the person suffering from it.

A degenerative process that can span over several years, glaucoma can cause irreversible damage to the optic nerve, leading to peripheral vision loss initially before affecting central vision.

What are the different types of glaucoma?

Glaucoma can come in many different forms, but the most common types are:

  • primary glaucoma
  • secondary glaucoma
  • open angle glaucoma
  • narrow angle glaucoma (angle closure glaucoma)
  • high pressure glaucoma
  • normal pressure glaucoma

In many cases, glaucoma can affect both eyes but it can also be asymmetrical, affecting one eye more than the other. However, every type of glaucoma is likely to develop in the same set of steps. These are:

  1. Starting with damage to the optic nerve, it will worsen over time.
  2. As time goes on, you will notice a gradual loss of peripheral vision.
  3. Eventually, the loss of peripheral vision will prompt a feeling of tunnel vision. At this point, central vision remains in good condition.
  4. After peripheral vision has completely faded, central vision will start to be affected.
  5. The final step is for permanent blindness in both eyes.

What are the signs of glaucoma?

One of the many worrying factors about glaucoma is that, in the vast majority of cases, it has no symptoms. In the event of an acute angle closure attack, an onset of symptoms may arise, caused by the closure of the drainage channel, leading to extremely high pressure in the eye.

If this were to happen, you would require immediate treatment by a professional at an eye hospital or specialist eyecare centre. In this situation, symptoms may include severe eye pain, blurred vision, halos around lights, red eyes, nausea and vomiting.

The signs of glaucoma can be picked up by your optometrist when they examine the health of your eyes. Many cases of glaucoma are spotted early in a routine eye examination, where the optometrist has been able to identify signs in the asymptomatic patient. If you’re likely to be diagnosed with glaucoma in the future – for example, if your family has a history of the condition – it would be advisable to have regular eye examinations.

Before a clinician is able to diagnose glaucoma, they will need to carry out a number of tests. These include:

  • indirect ophthalmoscopy: Stereoscopic evaluation of the optic nerve head
  • contact tonometry: Measurement of eye pressure
  • perimetry: Assessment of visual field
  • gonioscopy: Assessment of internal drainage angle
  • pachymetry: Assessment of the thickness of the cornea (front part of the eye)
  • nerve fibre analysis: Assesses thickness of nerve fibre layer around optic nerve head.
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