Relating Visual Ability to Job Competence

Different tasks require different visual capabilities. For example, train drivers must be able to recognize certain colours whilst crane drivers need good
depth perception. The standards listed can also be applied to occupations that are considered to have comparable visual requirements.

While it is quite simple to establish an employee's visual ability, relating this to their job competence is more complicated. There is no satisfactory method of grading job competence due to non-visual factors influencing the assessment. For example, it may be influenced by age, intelligence, attitude, motivation, manual deterity and motor reaction times.
There are five-step programme for establishing the vision standard:

1. Choose a method for grading job competence.
2. Analyze the visual factors required for the task.
3. Decide on criteria for visual competence, e.g. VA 6/9 or better and stereopsis.
4. Screen the vision of two groups of employees who are judged  to be:

• Job competent;
• Job incompetence . These two groups should be age and sex matched if possible.

5. Compare the grading of visual competence to job competence. If the appropriate vision standard has been chosen then the majority of the visually incompetent should fall into the job incompetent group.

Grading job competence can be done in a number of ways and a good suggestion is to assess the following:

1. Supervisor rating;
2. Quality and quantity of production;
3. Accident frequency;
4. Absenteeism;
5. Employee turnover;
6. Wages (if on piece-rate)

Visual task analysis

Before the vision screening can be carried out there must be an analysis of the visual tasks involved in the occupation concerned. Analyzing the visual factors required for the task is of crucial importance and ideally any analysis should be carried out at the place of work, e.g. factory or office. Factors such as distance and size of the critical detail of the task should be assessed, along with need for colour discrimination, depth perception, body, head and eye posture, field of vision, eye movements required and the contrast and illumination of the task. From the subsequent analysis the important visual factors can be identified.

There are occasions when on-site analysis is not possible. A logical method for determining the visual factors required for a particular task has been propose and is designed to act as a simple reference guide for use by optometrists in a consulting room.

From the knowledge of the distance and size of the critical detail of the task, visual acuity necessary to discriminate the smallest detail can be determined.

After analysis of the visual task allowing the important visual factors to be determined a standard can be set by either:

1. Choosing a standard believed to be necessary to work efficiently and safely, e.g. VA 6/12, distinguish principal colours. This can be tested by relating visual competence to job competence as described previously; or
2. Insisting on the normal level of visual capabilities for each factor chosen, e.g. VA 6/6, normal colour vision. This approach would exclude some who were capable of performing the task comfortably.

You may also like:

Vision Screening Of Employees

Methods of Vision Screening of Employees