Another look at visual standards and driving

Readers may have found the explanation of acuity notation confusing in this editorial by William Westlake (21 October, pp 972-3). It should have been made clear, midway through the opening paragraph, that a Snellen acuity of 6/15 is equivalent to 20/50 in the United States and 0.4 in decimal notation. The author also wants to clarify that the minimum visual field of 120° should also be tested by using specified target sizes and lighting conditions.