Fatigue of accommodation: changes in accommodation after visual work.

The present study was designed to determine whether classical accommodation theory or dual-innervation accommodation theory best explains the visual fatigue effects of prolonged visual work. The accommodation responses of 20 young male adults were measured, using a laser optometer, while they viewed a near target (30 cm), a far target (6 m), or in total darkness. Measurements were made before and after 1-h fatigue sessions, during which subjects either read monocularly presented slides of text at near or far distances, or remained in darkness. There were no significant changes in near or far target static accommodation as a result of any of the fatigue sessions. Dark focus accommodation shifted inward after the near target viewing task and after prolonged dark viewing. The results are discussed in terms of their implications for research in accommodative fatigue, and their relation to other current research.