Visual display height

We examined the influence of backrest inclination and vergence demand on th e posture and gaze angle that workers adopt to view visual targets placed i n different vertical locations. In the study, 12 participants viewed a smal l video monitor placed in 7 locations around a 0.65-m radius are (from 65 d egrees below to 30 degrees above horizontal eve height). Trunk posture was manipulated by changing the backrest inclination of an adjustable chair. Ve rgence demand was manipulated by using ophthalmic lenses and prisms to mimi c the visual consequences of varying target distance. Changes in vertical t arget location caused large changes in atlantooccipital posture and gaze an gle. Cervical posture was altered to a lesser extent by changes in vertical target location. Participants compensated for changes in backrest inclinat ion by changing cervical posture, though they did not significantly alter a tlanto-occipital pasture and gaze angle. The posture adapted to view any ta rget represents a compromise between visual and musculoskeletal demands. Th ese results provide support for the argument that the optimal location of v isual targets is at least 15 degrees below horizontal eye level. Actual or potential applications of this work include the layout of computer workstat ions and the viewing of displays from a seated posture.