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Jerry R Paugh, Alba Alfonso Garcia, Eric Potma, James V Jester; Assessing Meibum Quality in MGD Subjects using Stimulated Raman Spectroscopy. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):328.
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© ARVO (1962-2015); The Authors (2016-present)
Studies using stimulated Raman spectroscopy (SRS) to probe mouse and human meibomian glands indicate that there is maturation of meibum lipid from the acinus to the central duct characterized by the removal of protein and a reduction in the protein to lipid (P/L) ratio. More recently, an altered P/L ratio was identified in mice subjected to dry eye environmental stress suggesting that altered meibum maturation may underlie changes in lipid quality in MGD. The purpose of this study was to access meibum excreta from normal and MGD subjects using SRS and measure the lipid and protein contributions.
Meibum was collected from human subjects demonstrating varying meibum quality (Grade 0.5 to grade 2.0 on a 0 - 3 scale where grade 3 is inspissated). Smears were spread on a microscope slide and later characterized using stimulated Raman spectroscopy (SRS). Vibrational signatures for the lipid CH2 stretching region (2800cm-1to 3000cm-1) and protein (2935cm-1) were then imaged over the sample.
Normal meibum showed a uniformly strong lipid signal with Raman shifts in the symmetric and asymmetric CH2 stretching regions (2846cm-1 and 2886cm-1) consistent with the presence of sterol and wax esters with a much lower contribution of protein with a characteristic Raman peak at 2935cm-1. Meibum from MGD subjects showed a greater contribution of protein mixed in with the lipid that increased with increasing severity of MGD quality. Interestingly, meibum that contained particles based on clinical evaluation, also contained regions with very high protein Raman peaks that were devoid of lipid and consistent with protein aggregates.
Raman spectroscopy allows compositional analysis of the final gland secretion. The findings of an altered protein content in meibum from MGD subjects suggests compositional changes in MGD consistent with loss of meibum maturation, and may offer an important, objective measure for diagnosis and treatment efficacy.
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