Yesterday was the annual AGM of the Association of Optometrists, and also a study day- all Optometrists have to undertake a certain amount of Continuous Education and Training. At the moment this is voluntary, but will probably become compulsory in due course.
One of the lectures at the study day was about driving and vision, a subject that has become very topical of late. Particularly interesting I thought were a couple of videos which tracked the eye movements of Glaucoma patients when tested in a Hazard Perception Test. It had always been assumed that people who have a visual field deficiency will scan around, and move their head more to compensate for their problem, but as is mentioned here, the issue is that they may not even realise that they have a problem, and even if they are aware of an issue, they do not see the problem. If you don’t see something, you don’t think “I didn’t see that” – you just don’t see it.
The Hazard Perception test used eye tracking to follow the “Point of Regard” of normals and Glaucoma patients, also measured were reaction times – when would they hit the brakes? The study found that people with Glaucoma do not scan around more than normals – indeed one of the videos below show that they remain fixed almost exclusively on the car ahead, failing to notice the hazard of a car pulling out ahead, until the car they are following reacts to the threat.
Video Number 2 shows the Glaucoma patient’s Point of Regard in Blue, the normals are shown in red, it is quite noticeable how little the Glaucoma patient looks at other aspects of the driving scene – they completley fail to look at the pedestrian with the buggy, something all the normals are obviously worried about.
Video number 3 has superimposed onto it a representation of the patients field of vision- the more dense the areas of field loss, the darker the overlay. (It moves around because its position is relative to the fixation point, the blue dot. Remember that a Glaucoma patient will not see this blackness, they will just have blank areas, their brain will fill in the details as best it can.
The Glaucoma losses featured in Video 2 and 3 are mild to moderate – according to UK standards (where this study was done), this patient would still be legal to drive.
This shows that even if you do not feel that you have a problem, you should have your eyes regularly checked!
The full articles are available to read at these two links;