From the Bench to the Bedside, the Determination of the Etiology of Dry Eye Using Spectroscopy

Abstract

PurposeMeibum lipids are believed to be important to tear film stability, but tear film lipid compositional, structural and functional relationships are not well established.MethodsNMR, Fourier transform infrared and Bruster angle spectroscopies were used to quantify meibum lipid composition, structure, and film lipid rheology, respectively.ResultsThe molar ratio of Cholesterylesters/Wax ester increased with age, in cohorts aged 1 to 19 years old, respectively. The same molar ratio decreased for cohorts aged 20 to 88 years old with and without meibomian gland dysfunction (MGD) that leads to dry eye, respectively. The molar ratio of =C‐CH2 /ester increased with age for cohorts aged 1 to 19 years old, respectively. The same molar ratio decreased for cohorts aged 20 to 88 years old, with and without MGD, respectively. Compared with meibum from donors without dry eye, meibum from donors with MGD contained less straight‐chains, more iso‐branched chains, and the same amount of anteisobranched hydrocarbon chains. Human meibum order increases with age between 0 and 25 years old, meibomian gland dysfunction and with donors who have had hematopoietic stem cell transplantation. Interestingly, tear film stability also increases in the same order. When symptoms of dry eye were ameliorated with treatment, lipid order was restored. Principal component analysis scores correlated with age and dry eye by 93 %.ConclusionsThe changes in meibum composition with age and MGD contribute to the increase in lipid order of the same samples from donors without compared with those with MGD. Higher lipid order is associated with a higher reciprocal compressibility modulus that results in a tear film lipid layer that is not as compressible and not as viscoelastic. Strong lipid‐lipid interactions could contribute to the aggregation of tear film lipids and contribute to a decrease in tear film spreading and dry eye.Support or Funding InformationMajor support was obtained from the National Institute of Health [grant number EYO RO126180] and an unrestricted grant from Research to Prevent Blindness Inc. New York, NY, USA [grant number GN151619B].Lipid order or stiffness correlates with tear film stability with age and dry eye symptoms.Figure 1