In the UK, every driver is legally responsible for ensuring their eyesight meets the minimum standard for driving. The law states that you must be able to read a standard number plate from a distance of 20 metres (approximately five car lengths). In clinical terms, this equates to a visual acuity of approximately 6/12 on the Snellen chart, measured with both eyes open and with glasses or contact lenses if you normally wear them. You must also have an adequate field of vision — at least 120 degrees horizontally — with no significant defects within the central 20 degrees.
Many drivers are unaware that their vision has deteriorated below the legal standard, because changes often occur gradually. The DVLA estimates that as many as one in six motorists on UK roads may have vision that falls below the legal requirement. This is a serious road safety issue: poor vision contributes to an estimated 2,900 casualties on UK roads each year. A simple check is to stand 20 metres from a parked car and try to read its number plate — if you cannot do this comfortably with your usual correction, you should not drive until you have had your eyes tested and, if necessary, updated your glasses.
If you hold a driving licence and develop an eye condition that could affect your ability to drive safely, you are legally required to notify the DVLA. Conditions that must be reported include glaucoma, diabetic retinopathy (if treated with laser or injections), macular degeneration, visual field loss from any cause, double vision, and cataracts that significantly affect your vision. Your optometrist can advise whether your condition is notifiable. Failure to notify the DVLA can invalidate your motor insurance and, in the event of an accident, could result in prosecution.
Professional drivers — including HGV, bus, coach, and taxi drivers — are required to meet higher visual standards than ordinary car drivers. Group 2 licence holders must have a visual acuity of at least 6/7.5 in their better eye and at least 6/60 in the other, along with a wider field of vision requirement. Regular eye testing is particularly important for professional drivers, and your optometrist can carry out a driving vision assessment and provide any required documentation for the DVLA or licensing authority.
Night driving presents additional visual challenges, even for people whose daytime vision meets the standard. Pupil dilation, increased glare from oncoming headlights, and reduced contrast sensitivity all make night driving more demanding. If you notice increased difficulty with night driving, haloes around lights, or glare that was not present before, book an eye test — these symptoms can be caused by early cataracts, uncorrected astigmatism, or dry eye, all of which are treatable. Anti-reflection coatings on your glasses can reduce glare significantly and are well worth considering if you drive regularly after dark.