Purchase this article with an account.
J. C. Arciniega, E. J. Nadji, J. C. Wojtowicz, J. P. McCulley, E. M. Mohamed, I. A. Butovich; The Effects of Temperature on Stability of Human Meibomian Lipid Films in vitro. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4253.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The health of the ocular surface is affected by the stability and dynamics of the tear film (TF) and its outermost part called TF lipid layer (TFLL). However, the impact of environmental factors such as air temperature on the properties of TFLL is not well established. It is known that exposure of the cornea to low temperatures causes it to reach temperatures below physiological levels. The purpose of our study was to determine the effects of temperature on the TFLL by using Langmuir films of normal human meibum as a model of TFLL.
Meibum samples were collected from the Meibomian glands using hard-squeezing technique. Their dry weights were determined gravimetrically. A thermostated Langmuir film balance was used to study the surface pressure (π/A) isotherms of meibum. Two subphases were used: a Tris-buffered saline (TBS) and an artificial tear solution (ATS) with different salts and proteins. Four temperatures were tested: 3, 23, 34, and 43ºC. The amount of meibum used to form lipid layers was calculated using a proprietary algorithm based on lipidomic analyses of human meibum.
Temperature had a strong impact on the stability of Langmuir films of meibum on TBS subphase. Compared to the physiological temperature of 34ºC, the lipid layers equilibrated at 3ºC produced a dramatically different π/A isotherm with clear signs of formation of condensed lipid "rafts" surrounded by lipid-free zones. The effect was temperature-dependent and was completely gone at 44ºC, where meibum layers approached liquid state. When using the ATS subphase, the results indicated that the changes in the lipid layer dynamics and stability at different temperatures were much less obvious due to the proteins’ ability to accumulate at the air/water interface and fill out the lipid-free zones. The effects of proteins were visible at all tested temperatures. The effects of meibum and proteins appeared to be additive.
The TFLL in vivo could be affected by low temperatures, which may lead to a decrease in its stability due to solidification of its lipid components. Tear proteins may partly compensate for this effect by filling out the lipid-free zones.
This PDF is available to Subscribers Only