Are you driving when your vision says you shouldn’t?
Do you know the minimum eyesight standards for all drivers? Yet you drive?
The law requires that all drivers meet certain eyesight requirements. You can wear your glasses or contact lenses to meet these requirements, but you have to meet them, or your licence will be revoked and your insurance invalid, especially if you have an accident. Let me take you through the essential requirements for the eyes and vision for DVLA minimum standards.
In good daylight, you should be able to read a registration mark at a distance of 20 metres where the numbers and letters of a standard number plate measure 79 mm high and 50 mm wide. I was interested to note that before 2001 number plates had a slightly different size and they were 79 mm high and 57 mm wide and they had different contrast, and so for those cars, the distance is 20.5 metres.
When you are tested at the optician your visual acuity using the chart of letters called the Snellen chart has to be at least the equivalent of the line called 6/12 with both eyes open. If you only have vision in one eye, it is the same with just that eye working. You can wear your glasses or your contact lenses to do this test.
If you find that you cannot read the number plate at 20 metres or you cannot read 6/12 at the opticians, then you are not meeting the standards. You should not drive until you have chatted to the DVLA or seen your ophthalmologist.
In addition to your vision for 20 metres and the Snellen chart you also have to have a minimum field of vision. Patients with glaucoma often have a reduction in their visual field. That has a significant impact because when they are driving around, they are not able to see well out into the periphery. Therefore they are at risk of an accident, and they are not safe to themselves nor other drivers. Other conditions which alter the size of the visual field include strokes, which can give you a visual field defect and surprisingly change the position of your upper eyelids. If your upper eyelids are drooping either on one side or both sides, they are likely to be interfering with your field of vision.
There are minimum standards set by the DVLA for the field of vision for all drivers. You have to have what is called the equivalent of 120 degrees horizontally of which 50 degrees should be on each side. There should be no significant defect in your binocular visual field, which is encroaching within your central 20 degrees of fixation either above or below the horizontal line. That means that patients that have neurological conditions such as strokes causing what is called her homonymous or bitemporal defects close to fixation usually cannot be accepted to have a driving licence.
Individual tests exist to detect whether you are eligible to drive based on your visual field. Here at Clinica London, we carry out the binocular Esterman visual field test and we will also carry out a Humphrey visual field test to find out more about the overall visual field. The Esterman test is a visual field test, which measures the 20 degrees radius of fixation, so it is looking for defects affecting your central vision.
All is not lost. If you do fail your minimum standards and then the defect is found to be
- stable for at least 12 months,
- with no other pathology
- with good vision
- without double vision
And, there is no other impairment of your visual function such as
- glare from cataract
- a defect of contrast sensitivity
- impairment of twilight vision
then the DVLA will reconsider your licence on an individual basis.
Of course, if you are a bus or lorry driver, there are much higher standards of the field of vision. You have to have a much broader field of vision up to 160 degrees horizontally of which at least 70 degrees should be to each side. For your vertical visual field you need to have at least 30 degrees above and 30 degrees below and no significant defect within 70 degrees horizontally or 30 degrees each of up and down (a total 60 degrees).
Of course, you can’t have any other impairment of visual function including such conditions as glare sensitivity, contrast sensitivity or impairment of your vision in the twilight. That can happen from conditions such as cataract, macular degeneration, inherited retinal problems.
If you require sophisticated vision testing for purposes of driving, we will assess you here at Clinica London and advise you. We will also provide you with copies of your tests and write a full report.
Usually, if the DVLA has a concern, they will write to you or us requesting that you have the tests, but if you are concerned, you may wish to have the tests to confirm to yourself and your family whether you need surgery and whether you can drive with a licence legally. If you have upper eyelids encroaching on your vision, we can correct that and enable you to drive again.