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Jerry R Paugh, Alba Alfonso-Garcia, Marjan Farid, Sumit Garg, Eric Potma, Donald J. Brown, James Jester; Characterization of Expressed Human Meibum Lipid Composition using Stimulated Raman Spectroscopy (SRS). . Invest. Ophthalmol. Vis. Sci. 2017;58(8):4395.
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© ARVO (1962-2015); The Authors (2016-present)
Previous studies have shown that differences in meibum composition can be measured using Stimulated Raman Spectroscopy (SRS) in normal and environmentally stressed mice. The purpose of this study was to determine if SRS can detect lipid differences in human meibum collected from normal and meibomian gland dysfunction (MGD) subjects.
All subjects were evaluated for tear breakup time (TBUT), ocular surface fluorescein staining (FS), meibomian gland dropout (DO) and meibum expression (ME). Meibum was collected using a Korb MG expressor and then transferred to a clean glass slide and evaluated using SRS vibrational signatures in the CH stretching region (2800 – 3050 cm-1). Vertex component analysis was used to reduce the data to 3 color coefficients and K-means clustering was then used to group the pixels according to spectral similarities similar to the central duct (G1), ductules (G2), disintegrating meibocytes (G3) and differentiating meibocytes (G4).
Meibum samples were obtained from 56 lower eyelids of 18 normal and 23 MGD subjects (41 total) averaging 50.1 years of age (range=22 to 85), and comprised of 17 males and 24 females from Caucasian (26), Asian (9), Hispanic (5) and other (1) ethnicities. Linear correlation analysis (Pearsons) identified significant correlations between TBUT and FS (r=-0.439, P<.001), ME (r=-0.337, P<.002) and Age (r=-0.370, P<.005). Regarding lipid composition, G1-G4 were identified in all individual meibum samples, but in general the appearance of G1 and G4 lipid was inversely associated with G2 and G3 lipids. The only significant correlations identified for different lipid compositions were between the level of G1 and TBUT (r=-0.321, P<0.02) and FS (r=0.443, P<.001) and between G3 and FS (r=-0.277, P<.05). Multiple linear regression analysis identified G1 lipid (P<.003) and ME (P<.002) as the best predictors of tear film instability (TBUT < 5s) with an R=0.601 (P<.001).
SRS allows compositional analysis of expressed meibum from humans that can be correlated to changes in both TBUT and fluorescein staining. These findings support the hypothesis that SRS may be useful in identifying lipid compositional changes associated with ocular surface disease and evaluating the effects of therapy.
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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