Postural modifications of VDU operators wearing bifocal spectacles.

This paper describes the postural changes experienced by presbyopic operators of VDU workstations while wearing a pair of bifocal spectacles. All operators reported in this paper had suffered neck and back aches, in addition to generalised problems of asthenopia, while using the VDU workstation. The ages of the operators ranged between 47 and 58 years. The operators' head movements, in looking from the keyboard to the screen, were two to three times greater when bifocal spectacles were worn compared with specially prescribed single-vision occupational spectacles. There were also greater movements in the flexion of the wrist and elbow while using bifocal spectacles and looking from the keyboard to the screen. There was no relationship between the amount of head movement and the position of the bifocal reading segment with respect to the operators' pupil. It was concluded that the symptoms reported by these presbyopic operators were due to static loading of the muscles in the neck and back, induced by the use of bifocal spectacles.