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Jadwiga C Wojtowicz, Anne McMahon, Igor A Butovich; Human Tear Film Lipid Variability – A Year-long Assessment. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4382.
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The tear film has a complex structure and dynamics which have not yet been completely elucidated. Our aim was to evaluate over time changes in the lipid composition and tear volume of human tears.
The tears of two normal (non-dry eye, a male and a female volunteer) were collected weeklybetween 3:00 and 5:00 pm over a period of one year, using Schirmer test strips (without anesthetic). Tear samples were recovered from the strips using a chloroform-methanol (3:1) solvent mixture, and analyzed individually using chromatography and mass spectrometry. Intra- and inter-donor variability in their amount and composition were evaluated. The lipids were identified and quantitated using authentic lipid standards.
Over a 1-year period, tear production and the amount of total tear lipids, were found to be variable and changing from week to week. Tear production (as measured by Schimer I test) was variable within subjects and the lipid amounts were not proportional to the tear volumes. Intra-donor variability of tear lipid (for 2 eyes combined) was estimated to range from 10 to 80 ug for the male subject, and 3 to 4 times that – for the female. As regards to the tear lipid profile, it could be characterized as two groups – 1) a conservative one (making up to 90% of total tear lipids) whose lipid profile was fairly constant over time and resembled that of meibum (represented by cholesteryl esters, wax esters, OAHFA and cholesteryl esters of OAHFA), and 2) a dynamic one, which made 10% or so of tear lipids and was represented by free cholesterol, squalene, phospholipids, and acylglycerols. Its composition demonstrated high variations with no discernible pattern.
The tear volume, and the amount of lipid material that could be recovered from the ocular surface, varied widely in a random manner. Meibum contributed to the conservative group of tear film lipids, while the dynamic group (from sources other than meibum) was changing independently from the stable one.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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