Primary Open Angle Glaucoma

PRIMARY OPEN ANGLE GLAUCOMA

There are numerous types of glaucoma, but Primary Open Angle Glaucoma is the most common.  It is often referred to as “the silent thief of sight” because there are no symptoms until the vision is severely and irreversibly damaged.  Glaucoma is normally detected by an optometrist at a routine eye check and its incidence increases with age; 1 in 10 Australians over the age of 80 will develop glaucoma.  You are more likely to develop glaucoma if you have a family history, are myopic (short sighted) or have a history of eye trauma. 

 

Glaucoma damages the optic nerve (also called “the optic disc”) within the eye.  Over time this leads to loss of peripheral vision or tunnel vision and in severe cases can even lead to blindness.  The damage is permanent and irreversible.  This damage is due to raised pressure inside the eye (“intraocular pressure or IOP”).  Think of the eye as a car tyre – if the pressure of the tyre is too high over a long period of time then it will wear out.  The same applies to your eyes. 

 Tunnel vision in glaucoma

 

 

Loss of
peripheral vision
in glaucoma.

 

 

Normal optic nerve       Optic Nerve with Glaucoma       

A health optic nerve                   An optic nerve damaged by glaucoma

The front part of the eye contains fluid called aqueous that is produced by a number of pump cells inside the eye called the ciliary body.  This fluid passes through the pupil and across a membrane called the trabecular meshwork.  In glaucoma the trabecular meshwork is unable to drain all of the fluid that the pump cells produce.  This leads to an increase in the intraocular pressure.  The reason that glaucoma is sometimes called the silent thief of sight is that you don’t feel this increase in pressure.  Over many years, despite you not feeling anything, this elevate pressure will damage your optic nerve and vision. 

                   

The flow of aqueous fluid inside the eye
The effects if pressure inside the eye

At your appointment Doctor Cronin will analyse the results of numerous tests to assess your glaucoma.  These tests include –

  • Your intraocular pressure
  • Your central corneal thickness
  • Direct visualization of your optic nerve
  • Computerized perimetry of your visual fields
  • Baseline photography of your optic nerve for comparison at future appointments
  • Ocular Coherence Tomography “OCT” of your optic nerve fibre layer
  • Heidelberg Retinal Tomograpy of your optic nerve

If your ophthalmologist isn’t performing these tests then early glaucoma damage may be missed until it’s too late. 

 Diagrammatic summary of glaucoma

There are many treatments for glaucoma and Dr Cronin will discuss those that are best for you at your appointment.  Treatments include –

  • Eye drops to either reduce the aqueous fluid production or increase its outflow
  • A LASER treatment called selective LASER trabeculoplasty (“SLT”).  This is a painless LASER procedure that increases the drainage of fluid out of the eye.
  • If you are having or have had cataract surgery performed then you may be able to have an istent™ inserted to lower the IOP without drops.  This stent bypasses the trabecular meshwork to increase the flow of fluid out of the eye.
  • In severe cases of glaucoma other surgical procedures such as a trabeculectomy, Baerveldt tube or cyclodiode LASER may be required.  

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