Snellen acuity is a poor indicator of vision for driving

Guidelines of the Driver and Vehicle Licensing Authority state that a binocular Snellen acuity between 6/9 and 6/12 is required to read a number plate at 20.5 m, the legal standard for driving. Currie et al (p 990) investigated what proportion of patients with 6/9 and 6/12 vision could meet this standard, and they assessed by postal questionnaire the advice given by healthcare professionals to patients with such vision. A major proportion of those with 6/9 vision could not read the number plate, and a larger proportion with 6/12 vision could. Snellen acuity seems to be a poor indicator of an individual's ability to pass a number plate test. The authors conclude that the guidelines need clarification.

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Relevant Article

Reliability of Snellen charts for testing visual acuity for driving: prospective study and postal questionnaire

Zanna Currie, Archana Bhan, and Irene Pepper
BMJ 2000 321: 990-992. [Abstract] [Full Text] [PDF]