Among the most important of these are straining the clarity muscle of accommodation by looking too closely at very small objects and effects of strong local contrasts on the retina. These symptoms are brought about in particular by strenuous fine work, reading poorly printed texts or low-quality computer images, inadequate lighting, exposure to flickering light or optical aberrations of the viewer's eyes.
Elderly people are, of course, more prone to visual fatigue.
Obviously, all types of visual work can contribute to the general fatigue discussed earlier since every job that calls for more rapid and precise eye movements will make heavier demands on perception, concentration and motor control. Most of the examined operators suffered various complaints concerning not only the organ of vision but the central nervous system as well. A visual field test was performed on 100 volunteers to study learning or fatigue effects during one session. We noted no difference between trained and untrained subjects or between normal and pathological eyes. The results reveal considerable alterations in visual system within one working day.