Visual Standards For VDU Operators

It has been suggested that companies should screen the vision of VDU operators prior to employment
and at frequent intervals thereafter. This screening should be carried out to ensure that any refractive error and/or any oculomotor imbalance can be corrected to give maximum visual efficiency and comfort.

The recommended standards for VDU operators are as follows:

1. The ability to read N6 at a distance of 0.66m down to 0.33m.
2. Monocular vision or good binocular vision. Near phorias greater than 0.5 prism diopter vertically, or 2 prism dioptres esophoria and 8 prism dioptres esophoria at working distances are contraindicated and should be corrected unless they are well compensated or deep suppression is present.
3. No central (20 degress) field defect in the dominant eye.
4. Near point of convergence should be normal.
5. Clear ocular media examined by ophthalmoscopy and slit lamp biomicroscopy.

Most of the recommendations do not include a measurement of the fusional reserves or fixation disparity. As asthenopia or blurred vision is often due to the inability to compensate for a heterophoria due to poor fusion, it would be of significant value to measure the fusional reserves and the fixation disparity. The latter can indicate the stress in the binocular system and it has been reported to show an exo-shift after a day of close work. Whilst the various standards for VDU operators require the heterophoria to be within certain logical limits, they have not been based on clinical studies. Another point to note is that some of the recommendations do not include ophthalmoscopy which is necessary for the early detection of ocular pathology.

Ideally, the vision screening should be carried out by a qualified person and should include ophthalmoscopy and retinoscopy either as part of a full examination or as a modified clinical technique. Although it is more expensive to employ a professional person, the number of false referrals will be reduced and the reliability of the results assured. Vision re-checks should be carried out at regular intervals; a two-yearly period has been suggested. By the Australian Optometric Association.