International Standards:

Vision Requirements for Driving Safety

Section 1: Executive Summary

Section 2 – Preamble

In 2002 the International Council of Ophthalmology (ICO) issued a report, discussing Visual Standards, Aspects and Ranges of Vision Loss with Emphasis on Population Surveys ^[1].

The current report addresses individual assessment of visual functions and their relation to functional vision in the context of Vision Requirements for Driving Safety.

The purpose of this report is not to provide a set of uniform rules that can be implemented unchanged in any jurisdiction. Rather, it is aimed at providing a set of considerations for use by any group contemplating the development or redefinement of driving license requirements.

The 2002 ICO report distinguished several aspects of vision loss, notably Visual Functions, which describe how the eye functions and Functional Vision, which describes how the person functions in vision-related activities.

For each of these aspects, various ranges of functioning can be identified, ranging from normal functioning, over mild, moderate, severe and profound loss to total loss.  The traditional, simplistic, black-and-white distinction between those who are sighted and those who are blind is not tenable. A 2002 resolution by the International Federation of Ophthalmological Societies denounced the use of the word "blindness" for those who have useable residual vision ^[1].

The relationship between visual functions and functional vision is complex and can be influenced by many factors.  While population statistics may define average performance, individual functioning, as will be discussed in this report, can be considerably better or considerably worse than the statistical average.

Traditional clinical tests determine a performance threshold.  Real-life performance requires sustainable, supra-threshold performance.  Establishing driving license criteria therefore is an exercise in establishing a safety margin between performance on clinical tests and performance in actual traffic, rather than a cut-off value between competence and incompetence.

Ultimately, driving safety does not depend so much on what is seen, but rather on how quickly and how adequately drivers respond to what is seen.

Section 3 – Vision Loss and Driving Safety

In our society losing one’s driving license has major social consequences. Vision is the most important source of information during driving and many driving related injuries have been associated with visual problems. Visual assessment for driving is thus a major health issue.

This paper was developed to explore ways in which the ICO could contribute towards global harmonization in this important area. It lists many sensitive questions.

A literature review shows that there is a relationship between the safety margin established by vision-related driving license requirements and actual driving performance, but that this relationship is generally weak.

Section 4 – Which Visual Functions might be tested?

This section discusses various visual functions, among them:

• Visual acuity, which is commonly tested.
• Contrast sensitivity, which is significant, but rarely tested.
• Visual field, for which requirements vary and testing methods are rarely specified.

Other visual functions include: glare sensitivity, Useful Field of View (UFOV), diplopia, color vision and night vision.

A survey of current requirements can be found in Appendix 1 and 2.

Section 5 – Suggested Criteria and Rules

This section discusses suggested criteria and rules. It stresses the need for binocular (both eyes open) measurements and the need for a gray zone in which decisions will be based on individual consideration, rather than on the application of strict numerical criteria.  It also stresses the interaction of visual and non-visual parameters.

For visual acuity the commonly used threshold of 20/40 (0.5, 6/12) is accepted.

For visual fields a binocular field of at least 120° horizontal and 40° vertical is suggested.

Contrast sensitivity screening is listed as desirable.

The use of restricted licenses is advocated.

Periodic renewal is advocated, especially for older subjects.

Section 6 – Summary and Recommendations

This section summarizes the recommendations.

Appendix 1 – Survey of Driving License Requirements in various countries except the USA

Appendix 2 – Survey of Driving License Requirements in various states in the USA

Appendix 3 – Suggestions for Additional Tests

Traditional clinical tests were developed and refined to facilitate the diagnosis of underlying disorders.  They generally measure threshold performance for a single parameter in a static environment.

This section list some suggestions for non-traditional tests, aimed at estimating functional performance.  They may assess several parameters in one test and consider reaction speed in a timed environment

The report can be downloaded in PDF format from the Web site of the International Council of Ophthalmology at: www.icoph.org/pdf/visionfordriving.pdf.

Next: Vision Requirements for Driving Safety: Section 2 – Preamble

Also see: Table of Contents

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