Do you remember reading out a number plate in the distance when you took your driving test? Would you be able to do the same now?
Many drivers cannot, and police in the Thames Valley, Hampshire and the West Midlands have vowed to take drivers with poor vision off the roads, testing drivers' vision "at every opportunity".
As campaigners call for motorists to take an eye test every 10 years - when licences are required to be renewed - we take a look at eyesight requirements and what other health conditions could see you lose your licence.
:: What are the UK's eyesight requirements?
Drivers must be able to read a car number plate made after 1 September 2001 from 20m (65.6ft) away, using glasses or contact lenses if necessary.
Motorists must also meet the minimum visual acuity - the clarity of vision - requirement of at least 0.5 (6/12) on the Snellen scale, often characterised by several rows of letters which get smaller as you read down a chart.
According to DVLA rules, drivers must also have an "adequate field of vision", which opticians can test.
Research has suggested 35% of optometrists have seen patients who should not drive
Lorry and bus drivers are required to have a larger visual acuity rating of 0.8 (6/7.5) in their "best eye" and at least 0.1 (6/60) in the other.
Glasses can be used to meet the requirements.
At the moment, new drivers are asked to read out a number plate on a parked vehicle before starting their practical driving test. They fail the test if they are unable to correctly read the plate and the practical is then stopped.
A 2012 study estimated poor vision caused 2,874 casualties in a year
Police are currently able to request an urgent licence revocation through the DVLA if they believe it is unsafe for a driver to remain on the road. Officers taking part in the trials in the Thames Valley, Hampshire and the West Midlands are hoping to use the power.
The power, known as Cassie's Law, was introduced in 2013 when a 16-year-old girl called Cassie McCord was killed after being struck by an 87-year-old driver in Colchester, Essex.
As part of the investigation into Cassie's death, it emerged that the driver had failed a police eyesight test days earlier but was able to continue driving due to a legal loophole.
:: How often do drivers have to have their eyes checked?
Eyesight is checked at the start of a driving test and drivers are reminded to get their eyes tested when they renew their driving licence photocard every 10 years.
However, there is no legal requirement to do so and campaigners are calling for a change in the law.
Campaigners are calling for mandatory eye tests for drivers
At the age of 70, drivers are required to renew their licences and must do so every three years from then on. They are also told to disclose any health issues and renew their licences only if they meet the minimum eyesight standards.
But again, there is no legal eye test requirement.
:: Other conditions you must disclose to the DVLA
Drivers can be fined up to £1,000 if the DVLA is not informed about certain medical conditions, which could affect driving. Those who choose not to could be prosecuted if involved in an accident as a result.
Some conditions can result in immediate revocation - these include eyesight problems or seizures. Other conditions mean your licence could be removed if a doctor deems it necessary but this is rarely the case.
Police are launching a crackdown on visually impaired drivers
Drivers must give up their licence if a doctor has told them to stop driving for at least three months.
Here are some of the conditions listed by the DVLA, which must be disclosed:
High blood pressure
Low blood sugar
Obsessive compulsive disorder
Click here for a full list.
If a driver is deemed unfit to drive for at least three months, they must give up their licence
:: How many drivers should not be on the road?
The Association of Optometrists published research last year which found more than a third (35%) of optometrists saw patients in the previous month who continued to drive despite being told their vision was below the legal standard.
A 2012 study by insurance firm RSA estimated that poor vision caused 2,874 casualties in a year.
According to a 2016 Direct Line study, 21% of drivers who need glasses or contact lenses always drive without them and those motorists increase their chances of having an accident by four times.
It said up to 13.3 million people could be putting themselves and others at risk by not wearing glasses or lenses while driving.
Almost 6,000 drivers and motorcyclists had their licences revoked in 2011 because they could not pass a standard eye test, according to the Road Safety Observatory.
Jonathan Lawson, Vision Express' chief executive, said official government statistics on the impact of poor sight were just the "tip of the iceberg".