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Visual fields testing

U2.9.2 Visual fields testing (2016)

The query this month is an interesting one: a member asked about a situation she had encountered with a patient. The patient was a glaucoma sufferer and, as a driver, needed to pass the DVLA visual fields test. What prescription should they be wearing to maximise their field of view? An interesting one I thought.

In all honesty, it was a situation I had never thought about before; I simply followed the instrument manufacturer’s instruction book, but on reflection I shared our member’s concern.

Patients are recommended to wear ‘the spectacles you drive in’ for the test but such patients are naturally anxious to perform as best they can and it is a reasonable request to ask if a special prescription might help them achieve a higher standard in a visual field test.

There are several different instruments in use across the country; the instructions for use might vary slightly but they all stipulate using the distance correction, bifocal or multifocal lenses are not contraindicated.

The confusion arises because the targets being viewed are near, and small, so surely a close work lens would help?

Not so apparently; the instrument is designed to ‘trick’ the eyes into believing the object is in the distance – rather like the test chart reflected in the mirror.

There may be a problem with thick, heavy spectacle frames or high plus lenses but the manufacturer’s claim that repeated tests, accepting the best result, overcomes any potential loss of field. It might be a good idea to fit contact lenses for the field test as some institutions recommend; although that’s not always practical with some elderly patients.

So it appears our member’s concern, while understandable, was groundless. Patients who have been asked to attend for a DVLA field test must, of course, be anxious and have real worries. It is the job of the DO or optometrist to reassure such patients that their vision and field of vision is adequate for driving – wearing their most up-to-date spectacles. The formal field test should then hold no fears if correctly performed.

It is the borderline patients who may well need extra reassurance as to how the test works and be told that the best result of several attempts will be taken. A relaxed and confident patient is more likely to pass such a test.