According to this article many of the ergonomic problems we face are visually-based, particularly with employees who use computer screens. Vision can be adversely affected by the office environment itself (lighting, equipment placement, etc.), by work habits (tilting the head to look at the PC monitor, etc.), and poor eyesight (near-sighted, far-sighted, over 40). The article includes a list of practical suggestions that can improve the visual ergonomics in the office.
Source: Sandy Smith, Occupational Hazards (Cleveland); Aug, 2007