Why do some people produce “pasty meibum?” PART 2

Part 2:

Fortunately, not all the tear oils come from the MGs – I quote from (and partially interpret) a scientific publication (below) regarding the composition (and sources) of tear oils.. For those not interested in all of the science, the take home is that much as we regard the Meibomian Glands as the sole provider of tear oil, the reality is that there are other likely sources that make significant contributions. The hopeful news (from my perspective) is that some of these alternative oil sources may be able to be amplified in some cases of reduced (or absent) MG function – to offset the deficiency of the MG dysfunction. I believe I’ve witnessed this in some cases where there do not appear to be any residual MGs left in any of the lids – yet the function of the tears, and general health of the corneas, appear clinically adequate (and may have little-to-no dry eye symptoms) …

"There is no doubt that the meibomian glands are a prominent source of lipids for the TF (Tear Film). However, it would have been a mistake to exclude from consideration other likely sources of lipids (oils), such as conjunctiva, cornea, and AT (Aqueous/watery Tear) produced by lacrimal glands. Earlier publications provided some clues about possible differences in lipid (oil) compositions of MGs and AT and similarities in the AT samples collected using the microcapillaries and Schirmer test strips.27 34 35 Our current HPLC-MS (fancy scientific analyzer) data showed that lipids of aqueous tears are more complex than meibomian gland secretions, necessitating a more cautious interpretation of the roles of the latter in tear film physiology. The observed presence of lower molecular weight compounds with m/zvalues between 500 and 600 and the detection of the large quantities of the compounds with higher polarities than typical meibum components suggest a more complex TFLL  (Tear Film Lipid Layer) composition than the one based only on MGs. Therefore, a detailed comparative lipidomic analysis of specimens obtained from different sources, determination of the structures of the newly detected lipid species, and evaluation of their possible physiological roles are in order." (http://www.iovs.org/content/49/9/3779.full) I remain surprised that there has not been further significant research and advancement of knowledge regarding these “alternative producers” of tear oils and look forward to results of such research.