Tear lipid layer structure and stability following expression of the meibomian glands.

In a masked investigation, tear lipid layer structure and non-invasive break-up time (NIBUT) of both eyes of 40 normal subjects were assessed with the Keeler Tearscope after unilateral manual expression of meibomian fluid from the lower lid. The HIRCAL grid (modified keratometer mire) provided the additional measure of tear thinning time (TTT). Twenty untreated normal subjects formed the control group. No difference in lipid layer structure or stability was observed between the right and left eyes of the controls. The NIBUT of the treated eyes was significantly higher than that of the untreated contralateral eyes which was, in turn, greater than that of the control eyes. Lipid layer thickness in the treated eyes was significantly higher than that in the untreated contralateral eyes and the controls but did not differ between the latter two groups. The TTT of the treated eyes was not significantly different from that of the untreated contralateral eyes but both were significantly higher than that of the controls. Unilateral meibomian gland expression results in increased lipid layer thickness and tear stability. A possible reason for the slight increase in tear stability in the untreated contralateral eyes is a complimentary reflex lacrimation induced by mechanical stimulation of the treated eye. Differences between the results of the Tearscope and HIRCAL grid are attributed to differences in the techniques of tear stability measurement.