The importance of the precorneal tear film for the quality of optical imaging.

The optical function of the eye critically depends on the presence of an intact precorneal tear film. Abnormalities of the tear film such as those occurring in the dry eye syndrome or in otherwise irritated eyes may interfere with vision. In 30 patients with dry eyes artificial tears were found to produce statistically significant improvement of vision (p less than 0.001) while no significant changes were seen in the untreated partner eyes. Static perimetry in another 30 patients using the 'macular programme' of the automatic Humphrey 620 perimeter showed artificial tears to increase mean thresholds significantly (p less than 0.001) whereas no significant differences were seen in the untreated partner eyes.