[Stability and flexibility of the lipid layer of the tear film and their pathologic changes in a biophysical experiment].

In vitro experiments with meibomian gland secretion from healthy subjects, patients with keratoconjunctivitis sicca and meibomianitis were performed. In addition, patients of different age groups of both sexes were also tested. The biophysical experiments included continuous measurement of surface pressure and surface potential under compression and decompression conditions. Surface pressure was determined by a Wilhelmy type film balance; surface potential was determined using the vibrating plate method. In the age group up to 60 years, the surface potential of females, males and patients with keratoconjunctivitis sicca showed a characteristic peak of 200 mV under compression, which was fully reversible under decompression. Females, males and patients with keratoconjunctivitis sicca over 60 years of age showed changes in the surface potential under decompression which indicated that the secretion was unstable and inhomogeneons. Patients with meibomianitis presented characteristic changes of surface potential. Qualitative alteration of the secretion may be the corresponding interpretation. The above biophysical methods have been used for the first time under clinical aspects.