Is your eyesight legal for driving? The dangers of cataracts and glaucoma

19 September 2019

Author: Kate Green

Legal eyesight for driving, cataracts and glaucoma

The effects of worsening vision


Deteriorating vision is a normal part of the ageing process, be that in the form of cataracts, age-related macular degeneration (AMD), glaucoma, or another sight-related condition. Ageing eyes also tend to suffer from presbyopia – age-related long-sightedness – which occurs as a result of the eye’s natural lens hardening with age. We rely on good sight for almost everything in day to day life, from checking our phones to reading cooking instructions. One of the tasks in our daily lives where sight is most crucial is driving. Each time you sit in the driver’s seat, you’re responsible for your life, those of your passengers, and also of every other road user that you pass. The importance of driving standard vision cannot be overstated, so it’s important that you’re monitoring your vision for any changes and keeping up with regular checks.


What are the requirements?


Simply put, you must be able to read a number plate from a distance of 20 metres. This is approximately the length of five cars, so it’s easy for you to check this for yourself next time you’re out and about – even as a pedestrian. Even if you’re using glasses or contact lenses in order to read the number plate, you’re still meeting legal requirements. You also need to have an “adequate field of vision” of 120 degrees to make sure your peripheral vision is in working order.

If you drive for a living – for example as a lorry or bus driver – your requirements will be slightly stricter:


“You must have a visual acuity at least 0.8 (6/7.5) measured on the Snellen scale in your best eye and at least 0.1 (6/60) on the Snellen scale in the other eye.

You can reach this standard using glasses with a corrective power not more than (+) 8 dioptres, or with contact lenses. There’s no specific limit for the corrective power of contact lenses.

You must have a horizontal visual field of at least 160 degrees, the extension should be at least 70 degrees left and right and 30 degrees up and down. No defects should be present within a radius of the central 30 degrees.” Source:


Lorry and bus drivers are also required to inform the DVLA of any issues with their vision in either eye, be that cataracts, glaucoma or other less common eye conditions. People who don’t drive for a living can check which eye issues they need to declare to the DVLA on the government’s website. Driving with eyesight below the legal parameters could invalidate your car insurance, so taking some time to guarantee you meet the requirements is vital.


Important of roadside eye tests


The police have the right to stop any motorist for a roadside eye test and, should the driver fail this test, the police can request for the DVLA to immediately revoke the driving license. This is done in the interest of the driver’s and other road-users’ safety, and is known as Cassie’s Law, named after a girl who was killed by a driver who had previously failed a roadside eye test. At the time, the police were attempting to revoke his license but, due to the lengthy process involved, he was still legal to drive at the time of the accident – despite having problems seeing pedestrians. It’s clear to see that on-the-spot eye tests have benefits for everyone involved and help to make our roads safer.


In-clinic eye tests conducted by your optician become free once you reach the age of 60, or if you have been diagnosed with diabetes or glaucoma. They will be able to advise you of any potential conditions which could threaten your sight, as well as monitor your prescription to ensure that your glasses and contact lenses are still doing their job properly. If you have been told that you need contacts or glasses by your optician, it’s actually an offence to not wear them whilst driving.


How can your vision be affected?


A number of eye conditions can affect your vision and make it unsafe for you to drive. The conditions listed below are the most common eye problems which affect people’s ability to drive safely. If you feel that you have any of the symptoms listed below, it’s crucial that you go and have your eyes checked by your optician.



Glaucoma is a condition which occurs as a result of high eye pressure. Over time, the pressure causes damage to the eye’s optic nerve and can lead to a total loss of vision. It usually begins with the loss of peripheral vision, a symptom which in itself is dangerous when it comes to driving. Your optician can test your peripheral vision by flashing lights at the edge of your vision and recording at which point you begin to see them.



Cataracts are usually an age-related eye condition, although they can occur in younger patients too. This is when the eye’s natural lens begins to fog and your vision looks cloudy. They gradually worsen over time and can result in total vision loss. However, they are treatable with a simple Refractive Lens Exchange procedure, which restores youthful vision. The blurriness caused by cataracts can mean that you’re unsafe to drive, and can also render your car insurance invalid, but you don’t need to tell the DVLA about cataracts if you still meet their visual acuity requirements.


Age-related macular degeneration

In terms of visual symptoms, AMD is actually the opposite of glaucoma: your vision begins to deteriorate from the centre outwards, while your peripheral vision is still fine. This is due to the macula in the eye beginning to break down, a common age-related eye condition. If caught early enough, however, it is treatable and won’t cause any lasting damage. Your central vision is imperative for driving safely so if you notice any changes in yours, have your eyes checked immediately.


Diabetic retinopathy

This is a condition involving high blood pressure and high blood sugar, which can lead to loss of vision. Symptoms include blurred vision, impaired colour vision, or blank spots in your vision. Again, each of these effects will heavily impact your driving, so diagnosis and treatment are very important if you want to continue to drive safely and legally. As with most of the other eye issues mentioned previously, diabetic retinopathy can be treated and cause no permanent damage if diagnosed early.


Can you drive with monocular vision?


Having vision in just one eye is called monocular vision, and is actually perfectly legal for driving. Providing you meet the DVLA’s other visual requirements, you don’t need to inform them if you lose your vision in one eye. However, this leniency only applies to non-commercial drivers; if you are a bus, coach or lorry driver, you must inform the DVLA of monocular vision. This is because having sight in only one eye can reduce your depth of field, potentially making night driving and overtaking other vehicles more dangerous. A normal visual field is usually around 170 degrees and, to drive safely, you must have a minimum visual field of 120 degrees. This is usually achieved with a single eye, even if the vast majority of that is made up by peripheral vision.


Visiting your opticians regularly is essential in ensuring that you are still legal to drive. Not only will regular eye tests pick up on any eye conditions you might have developed, but it will go a long way to ensuring that you and other road-users are being kept safe. If you’re tired of relying on glasses to make sure you’re driving safely and legally, consider the advantages of Laser Eye Surgery. You eliminate the problem of forgetting your glasses and benefit from sharper vision. 98% of Optimax patients achieve unaided driving standard vision following treatment with us, so get in touch to find out how we can help.

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