Surface activity of tear fluid in patients with primary Sjögren's syndrome.

Rupture of the preocular tear film leads to formation of a dry spot on the cornea with ocular irritation and symptoms of dry eye. One of the factors determining the stability of the tear film is its surface activity. The purpose of this study was to examine the surface activity of tear fluid from patients with Sjögren's syndrome. Tear fluid was sampled from the eyes of 16 patients with primary Sjögren's syndrome. The surface activity of the sample was measured on a Wilhelmy balance. Maximum and minimum surface tension was 72·2 ± 1·7 and 52·9 ± 7·4 mN m-1, respectively. Corresponding values in a previously studied group of normal subjects were 71·5 ± 1·3 and 46·6 ± 3·8 mN m-1, respectively. The difference in minimal surface tension was statistically significant (P<0·001). Reduced surface activity may be caused by dysfunction of the Meibomian glands and suggests a mechanism for causing the symptoms of dry eyes.