The investigation of the role of visual and ocular characteristics of visual display unit (VDU) operators in the causation of subjective visual fatigue has not been reported previously. A retrospective study in which the visual and ocular characteristics of symptomatic and asymptomatic VDU operators was carried out in order to determine whether such a relation could be demonstrated. Three groups totaling 1013 VDU operators from two semigovernment organizations were assessed using either a full eye examination or a modified clinical screening technique. Before examination, the operators completed a short questionnaire on the symptoms they experienced when using VDU's. Significant differences between the symptomatic and asymptomatic operators in some groups were found for over-refraction (spherical equivalent and cylindrical) and near horizontal heterophoria. Despite the existence of this relation, no basis for valid visual standards could be established. In particular, no basis was found for the automatic prescribing of low plus corrections and, in the absence of clearly definable visual standards, the involvement of clinical judgment in the assessment of operators was found to be necessary.