Description

This issue of CE Optometry aims to provide the optometrist with an up to date description of the current regulations regarding driving and vision, and an insight into the problems, both scientific and social, of setting visual standards for driving.

Jenkins, a Medical Adviser for the DVLA, has contributed an article in which the current regulations are detailed, along with information of how these have changed over time, see: www.dvla.gov.uk. The wording of the regulations, particularly those related to the visual field, has led to some confusion. For example, there should be no significant defect in the binocular field which encroaches within 20 of fixation above or below the meridian is subject to interpretation. Optometrists have, therefore, on occasions found it difficult to give advice to patients seeking their opinion as to whether or not they meet the current standards. They can find themselves in the difficult position of having the regulations and the test results and not knowing whether or not the patient meets the regulations. Insight into the way in which the DVLA interpret the visual field requirement is therefore welcome, and the article by Jones, which uses a series of examples to demonstrate how the DVLA interpret visual field results, gives the reader a better understanding of the problems facing the appeals panel and the way they interpret the standards.

The scientific literature relating accident rates to visual performance is well described in the articles by Wood and Taylor. While Wood cites ample evidence linking accident rate to visual performance, the nature of the relationship means that there is no clear cut-off level that reliably discriminates between safe and unsafe drivers. Thus, while vision standards are accepted as being an essential part of the fitness to drive standard, the level at which they are set is largely arbitrary.

Driving is a complex task that draws upon a variety of different sensory, processing and motor skills. Some of these skills are assessed by the drivers vision test while others are not. It is, therefore, quite feasible to have 2 persons, at the same risk of being involved in an accident, one of whom meets the vision standard and is permitted to drive, while the other does not. It is this patently unfair system that upsets those denied a licence on the basis of a marginal failure to meet the standard. While it is encouraging to hear that new research is being commissioned by the DVLA (see article by Jenkins) it seems unlikely that a simple solution to this problem is ever going to be found. The complexity of the driving situation is always going to mean that a simple visual standard will unfairly restrict some drivers whose risk of an accident is no greater than many of those who are permitted to drive.

The arbitrary level of the visual standards for driving is further highlighted in the article by Peli, who describes how the visual standard for driving varies across the USA. To many readers it must seem quite amazing that a patient who is unfit to drive in one USA State can be classified at fit to drive in a neighbouring State, especially, when you consider that a person who has a valid driving licence from any State in the USA can drive in all USA States.

The article by Taylor also highlights the social problems associated with the withdrawal of a driving licence and how these problems are going to increase with demographic changes in the population. The loss of mobility and independence that follows the removal of a licence can have a profound effect upon a persons quality of life and can put increased demands upon social services.

Taylors article also raises the issue of whether or not restricted driving licences should be made available within the UK (as they are in certain USA states and other European countries). This type of licence would permit a person to drive under certain conditions, e.g. during daylight. While the introduction of such measures will undoubtedly increase the complexity of the system, there are some very good reasons for adopting such an approach. It is well recognised that driving is more difficult at night and in certain weather conditions (e.g. snow, fog and heavy rain). In these conditions, the risk of an accident goes up to a level that could easily exceed that of a patient who is only marginally below the required vision standard but driving in good conditions. If the purpose of the standards is to reduce the risk of accidents, then a restricted licensing scheme seems perfectly appropriate.

Despite the importance of setting vision standards for driving, relatively little research is currently being undertaken in this subject. Readers interested in pursuing this topic further are encouraged to look at the Vision in Vehicles web sites,1 which gives details of their next meeting along with some useful references. It is hoped that this issue of CE Optometry will, in addition to meeting its two aims mentioned above, encourage more optometrists to take an active role in this important topic.

Reference
1. http://ibs.derby.ac.uk/viv/index.html