Alterations in the composition of meibomian gland secretions in patients with meibomian gland dysfunction based on Raman spectroscopy

Purpose: To investigate biochemical alterations in meibum from patients with obstructive meibomian gland dysfunction (MGD) using Raman spectroscopy, with a focus on lipid saturation, molecular conformation, and lipid-protein composition. Methods: Meibum samples from healthy individuals and MGD patients with obstructive MGD were collected by eyelid expression, smeared onto gold-coated silicon slides, stored at low temperature, and analyzed within 2 h. Raman band-intensity ratios were used to quantify lipid unsaturation (I1659/I1438, I3013/I2860), lipid molecular conformation (I2888/I2860), and lipid-to-protein balance (I1659/I1161, I3013/I1161). Raman mapping was used to assess spatial distribution of biochemical components. Results: Meibum was lipid-rich in both groups. Ratios associated with lipid unsaturation (I1659/I1438 and I3013/I2860) were significantly lower in MGD samples than in healthy controls, indicating reduced unsaturated lipids. Ratios reflecting lipid-to-protein balance (I1659/I1161 and I3013/I1161) were significantly higher in MGD, suggesting a relative reduction in protein content. The symmetric-to-asymmetric lipid ratio (I2888/I2860) also differed significantly between groups, though with a small absolute effect size. Raman mapping further revealed a heterogeneous spatial distribution of lipids and proteins in MGD meibum. Conclusion: Compared with healthy meibum, MGD meibum exhibits reduced unsaturated lipid content, altered lipid-protein balance, and increased biochemical heterogeneity, accompanied by subtle conformational lipid changes. These findings indicate that both lipid composition and microstructural organization are disrupted in MGD. This study supports the potential of Raman spectroscopy serve as a valuable tool for analyzing meibum composition and detecting pathological changes in MGD.