Oculomotor factors in the aetiology of occupational cervicobrachial diseases (OCD).

The traditional posture-ergonomic perspective on the aetiology of Occupational Cervicobrachial Disease (OCD) is discussed and criticized in the light of present knowledge of oculomotor strain during sustained visual work at short distances. Two experiments on ocularly induced neck muscular tension are reported. In both experiments EMG's were taken from six different muscles in the head, neck and shoulder region during a visual discrimination task. In Experiment 1, accommodation and fusion requirements were systematically varied by changing viewing distance in combination with the application of minus-lenses and base-out prisms. EMG was shown to increase as a function of accommodation and fusion load. In Experiment 2, a clinical population with severe and long lasting neck and shoulder problems and inappropriate optical corrections was studied with the same experimental design. EMG was shown to decrease when habitual corrections were replaced by more appropriate ones.