The DVLA reqirement is to read a standard number plate at 20.5 meters. lettrs must be 79mm high 57 wide (pre September 2001 plate, and 79mm high 50 mm wide post Sept 01 plate) You have to state your eye condition, and you have to have a visual field which is 120 degrees horizontally and 40 derees vertically (20 degrees above and below fixation)
If you are uncertain, then find an Optometrist/hospital which has a Humphrey VFA with an " Estermann" program. That's the officially recognised VF program (there are others).
Unsuprisingly all the driving info may be found on the DVLA website!
http://www.dvla.gov.uk, readable in Welsh and English. Navigate to thedriver information - medical rules and hey presto! The link:
http://www.assoc-optometrists.org/uploa ... _may04.pdf
is also useful.
Best
David