The association between demodex infestation and ocular surface manifestations in meibomian gland dysfunction

To investigate the association between ocular demodex folliculorum infestation and ocular surface manifestations in meibomian gland dysfunction (MGD).

Eight-six patients with MGD were enrolled. All enrolled subjects were tested in the following sequence: ocular surface disease index (OSDI), slit-lamp biomicroscope examination, corneal surface regularity index (SRI) and surface asymmetry index (SAI), tear fluid collection, fluorescein tear film break-up time (F-BUT), corneal fluorescein staining (CFS), Schirmer I test (SIT) and demodex folliculorum counting. Tear matrix metalloproteinase (MMP)-9 activity was assessed using MMP-9 activity assay kit.

Among 86 MGD patients, 40 were positive for demodex. The ocular demodex-positive group showed significantly increased scores of OSDI (25.96±13.74 vs 18.07±11.55, P=0.01), lid margin abnormality (2.38±0.87 vs 1.98±0.91, P=0.04) and CFS (1.28±2.00 vs 0.94±1.36, P=0.01) compared to the ocular demodex-free group. The tear MMP-9 activity was higher in the ocular demodex-positive group (102.9±32.4 ng/mL) than the ocular demodex-free group (46.2±19.2 ng/mL, P=0.03). There was no significant difference in meibum quality and expressibility, SRI, SAI, F-BUT and SIT between the two groups (P>0.05 for each). No significant correlation was noted between the number of demodex and ocular surface parameters in demodex-positive MGD group (P>0.05 for each).

Ocular demodex folliculorum infestation may be associated with ocular discomfort and ocular surface damage in MGD.