Expressibility of meibomian secretion. Relation to age, lipid precorneal film, scales, foam, hair and pigmentation.

The lower lids of 274 normal subjects have been examined in the slit-lamp for expressibility of secretion from the Meibomian glands. Secretion could be expressed from on an average 10 glands (median 11), dependent on age, decreasing with increasing age (from 14.5 glands at about the age of 20 to 7 glands above the age of 80). The expressibility was seen to be positively correlated to the thickness of the lipid layer of the precorneal film, estimated by the semiquantitative interference method. It was positively correlated to pigmentation and to ordinary greasy scales on the lid margin. The expressibility negatively correlated to retraction of the Meibomian orifices. The expressibility was found not to be correlated to elevated orifices, foam formation in the external part of the eye, cysts in the tarsus, nor with casts round the eyelashes. It is important to distinguish between cylindric casts (Demodex-induced) and ordinary greasy scales on eye lashes and lid margin.