Glaucoma: can you see to drive?

Health correspondent ( 17 June 2015 )

Glaucoma can cause damage severe enough to put your licence at risk before you notice any problem, warns David J Wright, Chief Executive International Glaucoma Association

There is no doubt that the sense we most fear losing is our sight. And for the motorists among us, there is equally no doubt that the thing we most fear losing is our driving licence, yet tens of thousands of us are risking two of our most precious abilities – to see and to drive - without being at all aware of the risk.

Glaucoma is an eye disease that gives no warning symptoms in its early stage. Consequently, a person won’t realise that they have something wrong with their vision until it is too late. By the time someone notices the effects of glaucoma, they are already way below the level of vision needed for safe driving with glaucoma, and the criteria are getting tighter with the latest Government review and harmonisation of our driving standards with those in Europe.

Glaucoma and your driving licence

The first question we need to ask ourselves is how we can be considered unsafe to drive before we become aware of any visual loss. The answer is actually quite simple. Everyone has a blind spot in each eye but unless someone shows you how to find yours, it is almost impossible to identify even with one eye closed. This is because the brain 'puts back the missing part of the picture' so you believe that you are seeing everything that is to be seen. 

In early stage glaucoma, parts of the edge of the field of vision are damaged while the central detailed vision isn’t affected. You don’t notice this damage because one eye will normally 'fill in' for the other and it is only when there is overlapping damage that it’s possible to notice a problem. There is also the fact that the brain continues to replace the missing parts of the field of vision, until so much damage has been done that there isn’t enough information getting through to the brain for it to be able to guess what should be there.

Visual impairment 

This means a person can lose 40% or more of their field of vision without being aware of any problem at all. The trouble comes if it is only at this stage, when a problem is noticed, that the glaucoma is detected. By then there is relatively little of the optic nerve left to save and, while it is possible to control glaucoma effectively, it is impossible to get back any of the vision that has already been lost.

Eye tests

 The second important question is what we can do to protect ourselves (and our driving licence) and again, the answer is quite simple: you must have regular routine eye examinations at the high street optometrist who can do the necessary tests.

The three glaucoma tests

  • Ophthalmoscopy: a visual examination of the appearance of the optic nerve head (where the optic nerve leaves the eye to go to the brain and where the damage done by glaucoma can be seen)
  • Tonometry: often known as the air puff test, this test checks the pressure inside the eye, because glaucoma is associated with a raised pressure in about 85% of cases
  • Perimetry: you look at a dot (that may be moving or still depending on the instrument being used) and press a button when you see a light or see something move (also depending on the instrument being used)

Retain your sight

These three tests together have been shown to increase the rate of glaucoma detection by four times when compared with ophthalmoscopy (the one mandatory test) alone.

These simple tests performed once a year for people over the age of 40 will make sure that glaucoma is detected at the earliest possible stage when treatment is most effective and the likelihood of retaining both your sight and your driving licence are greatest.

Increased risk

Some people are at increased risk of glaucoma and it is even more important for them to make sure that they have regular tests:

  • Age: glaucoma becomes ever more common the older we get – about 2% of people over 40 have the condition, but 6-8% of those over 70 will have developed the condition.
  • Race: people of African Caribbean origin are at least four times more likely to develop glaucoma and it also tends to start earlier, so testing from about the age of 30 is advisable
  • Family history: having a close blood relative with glaucoma increases the risk by about four times, so tests are free to first degree relatives once they reach the age of 40
  • Diabetes and very short sight: these conditions also slightly increase the risk
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