Abstract
Purpose :
The tear film lipid layer (TFLL) is formed by meibum. Changes in meibum composition and quantity in meibomian gland dysfunction (MGD) result in tear film instability and dry eye. O-acylated ω-hydroxy fatty acids (OAHFA), amphiphilic polar lipids that facilitate interactions between the superficial TFLL (composed of nonpolar lipids) and the aqueous layer, may play a critical role in tear film stability. Further, hydrocarbon chain (HC) unsaturation in meibum is important because less unsaturation results in more ordered (stiffer) lipids that may clump, block meibomian glands, and inhibit the spread of meibum on the ocular surface. The purpose of this exploratory study was to identify changes in OAHFA and HC unsaturation levels in meibum related to the presence and severity of MGD.
Methods :
Meibum samples were collected from 3 cohorts of adults with no MGD, mild-to-moderate MGD, and severe MGD in a noninterventional, prospective, clinical trial (ClinicalTrials.gov Identifier: NCT01979887). Meibum components were measured with 1H-NMR spectroscopy. Levels of OAHFA, cholesterol esters (CE), and HC saturation were normalized by hydrocarbon content; HC length was normalized by cholesterol ester + wax ester content.
Results :
Meibum samples from 69 subjects were analyzed: 24 non-MGD, 24 mild-to-moderate MGD, and 21 severe MGD. Meibum OAHFA and CE levels and HC unsaturation were reduced with increasing severity of MGD, following the order non-MGD > mild-to-moderate MGD > severe MGD. OAHFA levels were reduced 17% in mild-to-moderate MGD (P=0.002) and 22% in severe MGD (P<0.001) relative to non-MGD. HC length was not significantly different in mild-to-moderate or severe MGD relative to non-MGD (P=0.885 and P=0.055, respectively).
Conclusions :
Meibum OAHFA levels, CE levels, and HC unsaturation were reduced in MGD and were lowest in the severe MGD cohort, which may impact tear film homeostasis. The findings in this exploratory study may contribute to the understanding of the pathophysiology behind MGD.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.