How good does your vision need to be to perform a specific task?
This is a fundamental question for many day to day tasks, particularly those where an error has implications for public safety, such as driving a motor vehicle. Many occupations set a minimum requirement for a particular level of vision at the point of entry. The Disability Discrimination Act has highlighted the importance of providing an evidence base for visual standards, in other words, there needs to be proof that those with vision that meets the standard or better, are capable of reaching an acceptable level of performance when undertaking the task, and those whose vision is poorer than a particular standard will demonstrate inadequate performance that may impact upon safety.
The work we undertake involves a detailed analysis of the visual tasks involved in particular occupations and activities, to define those that represent the greatest visual demand and those that have the greatest safety implications. An experimental protocol can then be designed to test the performance of individuals with respect to these critical visual tasks, and compare the findings with standard clinical and psychophysical tests of vision, spanning visual acuity, contrast sensitivity, colour discrimination, visual field sensitivity and extent and glare, and others.
Using these methods we, along with collaborators such as the Institute of Occupational Medicine, have advised or developed evidence based visual standards for bodies such as the Rail Standards Safety Board, Department for Transport, Public Carriage Office and Civil Aviation Authority.