Currently United Kingdom (UK) law requires potential drivers to be able to read a standard number plate in good daylight. The test has some merit as a square wave contrast sensivity test in the real outdoor environment. The law puts the burden of self testing on the driver during the validity of his licence. Drivers are also required to report relevant (actual) and prospective disabilities. The relevant disabilities discussed are: inability to meet the number plate test; an inadequate field of vision; double vision; night blindness; and recurrent obscurations of vision. Prospective disabilities are: cataract; glaucoma; macular disease; high myopia; uveitis; keratitis; diabetic retinopathy; and retinitis pigmentosa. The development of a standard for minimal field of vision consistent with safe driving is outlined and redefined on a scientific basis using the III4E settings of the Goldmann Perimeter. Equivalent perimetry programs for use with second and third generation auto perimeters have been developed so that the standard can be easily applied in a way that is not equipment specific. These standards are currently in use in the UK by the medical advisers at the Driver Vehicle Licensing Agency (DVLA).
Abstract