Abstract
Purpose:
Posterior blepharitis, defined as inflammatory condition of the posterior lid margin, is a common disease encountered in ophthalmic clinics. The major cause of posterior blepharitis is meibomian gland dysfunction (MGD). We measured the meibum fatty acid (FA) composition in the patients with MGD and control subjects, and analyzed the correlation between meibum FA composition and clinical parameters.
Methods:
Thirty eight MGD subjects (13 men, 25 women; mean ± SD of age, 66.9 ± 15.0 years) and 20 control subjects (8 men, 12 women; 64.5 ± 6.7 years) were enrolled. Ocular symptoms score, corneal and conjunctival staining score, tear film breakup time and Schirmer value were evaluated. Lid margin abnormalities, meibomian gland morphology and meibum qualities were evaluated at six sites; three sites in upper lid (nasal, central and temporal) and three sites in lower lid (nasal, central and temporal). FA composition in collected meibum was analyzed by LC-FTMS system. Principal component analysis (PCA) and Volcano plot analysis were performed to determine relationships between FA composition and clinical parameters.
Results:
The MGD group had significantly higher mean of most lid margin findings score, most meibomian gland findings score and the degree of ease in expressing meibum than those of the control group. The distribution of meibum color and viscosity saw a significant difference between MGD and control group. Upper meibum color score was significantly correlated with epiphora and sticky sensation in MGD group (epiphora; r=0.49 p=0.020, sticky sensation; r=0.45 p=0.038). There were no significant differences in the grading, color and viscosity of meibum between upper and lower eyelid and among nasal, center and temporal sites. One hundred species of FA were detected in the meibum. Very long chain FAs with 36 and 37 carbon chains were detected in human meibum. Also, FAs with odd-numbered carbon chain such as 17, 19 and 21 carbons were detected. Clear and yellow meibum groups have a different characteristic to FA composition. Volcano plot analysis indicated that most unsaturated FAs had a tendency to increase from clear to colored meibum groups, especially FAs (30:4), (32:4) and (32:5) showed a tendency to increase clearly (p<0.00001).
Conclusions:
FA composition in human meibum was correlated with the color grading of meibum classified with a slit-lamp. This finding is helpful to elucidate the pathogenesis of MGD.