Some of the first roadside eye tests in the UK have been carried out on motorists in south Wales.
Drivers can go without an eye test from 17 until they are 70
Some 300 drivers were stopped for a two-minute check near Abergavenny. Officials said five would have failed the eyesight part of the driving test.
Drivers were asked to read four number plates at different distances to see if their eyesight was good enough.
New drivers' sight is checked when they sit their test, but it does not need to be examined again until they are 70.
There are concerns that many motorists are driving with poor sight which is leading to accidents, deaths and serious injuries.
Drivers taking part in the test on the A4041 were asked to read four number plates placed at 10m, 15m, 20m (the minimum required) and 25m.
Mike Wiltshire's sight was checked for the first time in 10 years
If the motorist was unable to read the closest number plate as part of the survey, police said they would not prosecute, but stopped them from driving home and ask them to sit an eye test.
Within an hour of the tests being carried out, one driver was found to be unable to read the closest number plate, but after putting on his glasses he could see the furthest.
One who took part, Mike Wiltshire of Cardiff, said: "I think this is a very good idea.
"I haven't had my eyes checked for about 10 years now but this has really made me think about it."
Richard Ross, of Cwmbran, said: "Taking part in this was no problem for me. There are a number of people around who have difficulty seeing but don't think about it when they are on the road."
The drivers were asked to read strategically placed number plates
Gwent Police, the National Public Health Service and Gwent Healthcare Trust arranged to carry out the survey.
Chris Potter, public health director of Newport Local Health Board, said: "What we want to do is find out how big a problem this is.
"At the moment we don't have any solid information about if this is a problem or not. "The government has a target to reduce deaths and serious injuries (on the roads) by 10% by 2010.
"The rate has been coming down and the emphasis has been about speed.
"But in Gwent last year there were 47 deaths and the police consider only three of those to be related to speed - the rest is driver error.
"And we don't know if some of these are because of poor sight. We just want to know if bad eyesight is a problem on the roads or not."
Richard Ross welcomed the test but worried about other drivers
Dr Anuradha, an ophthalmologist at Newport's Royal Gwent Hospital, said: "Although drivers have their vision tested as part of the driving test, it is not checked again until the driver is 70.
"We all know that normal eyesight changes with time, and there are some eye diseases that gradually affect our ability to see clearly.
"Although many people do have regular eye checks, we currently have no information on the numbers of drivers whose eyesight does not meet the required standard."
Inspector Glyn Fernquest of Gwent Police said: "Although driving without the required vision is an offence which can carry a fine of up to £1,000 and three penalty points, our aim in this survey is to gain a better understanding of the likely size of the problem, and to encourage regular vision checks."