The way that glaucoma creeps up on you without you knowing is one of the reasons it’s called “the silent thief of sight”.
To understand how glaucoma develops and how it affects sight it’s useful to know something about the workings of the eye:
• An eye works like an old fashioned (non-digital) camera where light from an image – after going through the opening shutter – is focused using a lens onto a plate or film at the rear of the camera
• In the case of the eye the pupil and cornea form the “shutter” whilst a flexible lens focuses the image on to the retina, a light-sensitive layer at the back of the eye
• Unlike a camera which is basically empty, the eye is filled with a liquid called an “aqueous humour” which is under a slight pressure; the pressure is called intra-ocular pressure, or IOP for short.
• An optic nerve transmits the signal from the retina to the brain.
Now we’re ready to understand what glaucoma is.
If the intra ocular pressure becomes too much, and it’s easily measured, then it can affect the optic nerve to such an extent that it degenerates and sight is gradually lost since no image can be received by the brain.
In other cases the blood vessels that supply the optic nerve can be affected leading to the same outcome of vision loss.
Symptoms of glaucoma
One stand out symptom is of course an increase in intra ocular pressure, noting that it’s an INCREASE that’s relevant, as people have different values much in the same way as they have different blood pressure values.
It’s essential then to have regular eye examinations to pick up any increase, especially for those with a high risk:
• Anyone taking prescribed corticosteroids – quite a few people do these days for a wide variety of conditions related to auto-immune deficiencies
• Those with some sort of history of glaucoma in the family
• Cardiovascular disease
• Migraine suffers – especially females
• Anyone having both short or long sightedness
Types of Glaucoma
There are two basic types – “open angle” and closed angle” – depending on the degree of flow of aqueous humour that is allowed to drain through a very fine mesh. Open angle glaucoma allows more flow than its closed angle counterpart
Open angle glaucoma makes up 90% of all cases, and because there are few if any signs or symptoms, apart from maybe unnoticeable vision loss, the condition may go undiagnosed.
Closed angle glaucoma can happen quite quickly, and since it’s often accompanied by some pain referral to an optometrist or ophthalmologist is usually made, leading to action to prevent vision loss.
With closed angle glaucoma accounting for 10% of cases it seems that there is no room for any other types. However there are other types caused by congenital defects, diabetes and use of corticosteroids.
Asians on the other hand are more likely to have the “closed angle” variety due to genetic differences.
What can be done?
The main thing to de done once a diagnosis has been made is to manage the condition to prevent further deterioration and importantly vision loss.
Lowering the intra ocular pressure (IOC) still remains the most effective management technique. Lowering can be achieved through use of drugs or eye drops as well as surgery.
Gradual loss of vision, especially in the elderly, can lead to increased risk of falls which will in turn exacerbate things, so re-education in balance and movement – however basic that may seem – can prevent a catastrophe!
What is key to understand is that regular eye examination will pick up glaucoma. Studies have demonstrated that for a person to realise that there is something wrong with their vision and glaucoma ultimately is the reason – at this point of patient recognition, they have lost 60% of their vision. This of course is way too late, so make sure you have a comprehensive eye test at least every two years.
What is to follow?
Glaucoma is a very important eye condition so will discuss it in detail over the next few posts.