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New study examines impact of central vision loss

One of the requisites for operating a vehicle, whether it’s a passenger car, motorbike or freight truck, is adequate vision. Not only do we need our sight to ostensibly see where we are going, but our sight needs to have sufficient acuity to allow us to perceive and react to various hazards in time. Some people experience central vision loss.

While for many Australian drivers, the eye test part of the licence application is a simple formality, for others it can be a barrier to their ability to operate a vehicle.

Now a new study by Massachusetts Eye and Ear and Harvard Medical School has examined the ability of drivers with central vision loss to detect pedestrians on the road.

Central vision loss and driving

A scotoma, or central blind spot, is a common part of age-related macular degeneration (AMD). A condition estimated to affect 1 million Australians, according to the Macular Disease Foundation, with one in seven people over 50 thought to have AMD.

Researchers investigated how scotomas impacted reactions to pedestrian hazards through the use of a driving simulator. The findings indicated that central blind spots could potentially impede a driver’s ability to detect when pedestrians are approaching their field of vision from one side.

As pedestrians were obscured, either partially or fully, by scotomas in the driver’s vision, it resulted in a delayed reaction time to pedestrian hazards. The researchers believe that this occurred when the driver became aware of a pedestrian in their peripheral vision – upon looking across, the driver’s central blind spot would then cover the pedestrian in question.

“If you are a low-vision patient, you should understand how the condition affects and perhaps limits your ability to drive safely,” said Dr Matthew Bronstad. “These data should prove useful to clinicians in advising patients about whether they should continue driving, and may even become a consideration for state agencies responsible for licensing drivers.”

Vision impaired drivers in NSW

In New South Wales, people are obliged to undergo mandatory eyesight testing when applying for a car or motorcycle licence. Upon acquiring their licence, Roads and Maritime Services states that drivers under the age of 45 need to get their eyes tested once every 10 years. From those aged between 45 and 75, this test happens at five-year intervals, and then annually for drivers over the age of 75.

The test is in line with the regulations laid out in the Austroads’ ‘Assessing Fitness to Drive’ standards that came into effect in March, 2012. Under the current version, should a licence applicant’s visual fields fall just short of the standard, a qualified optometrist or ophthalmologist can endorse a conditional licence, given that the applicant’s reaction times and alertness are satisfactory.

This is usually necessary when a driver’s visual acuityis  worse than 6/24 in their better eye, they have a significant scotoma or their visual field is less than 110 degrees, including 10 degrees either above or below the horizontal midline.

Any driver requiring prescription lenses to drive must inform Roads and Maritime Services, who will add a condition to their licence.

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