Drivers will be stopped by officers and asked to read the number plate of a vehicle 20.5 metres away in four operations across South Wales.
That task is part of practical driving tests in line with the DVLA's legal standard.
Now police can use new handheld devices at the roadside to report offending drivers to the DVLA and a licence removal notice can potentially be emailed straight back within minutes, making it an offence for them to get back behind the wheel.
South Wales Police says this will eliminate a "window of risk" that has existed, as drivers were previously free to drive away and wait until their licence was revoked by post.
The force says that highlighting the issue in public is even more important.
The primary focus is about raising general public awareness about the dangers of driving with poor vision. It is about tackling the public complacency which exists around the issue.
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Geraint 'Busker' Jones, from Llandysul, has been entertaining the crowds since the 1960s.