Abstract
Purpose:
There has been recent renewed interest in the prevalence of Demodex (DEM) parasites in meibomian gland dysfunction (MGD). This study examined the frequency of Demodex infestation in a cohort of patients with blepharitis unresponsive to conventional treatment compared to healthy controls.
Methods:
Patients attending a tertiary outpatient eye service in the UK who were unresponsive to conventional blepharitis treatment (topical and systemic treatment, combined with hot compresses and lid hygiene) were examined, along with a group of healthy controls. The presence/absence of cylindrical dandruff (CD) and MGD were recorded, together with comfort rating (visual analogue scale). Two lashes with CD were removed from each eyelid and examined microscopically for DEM parasites.
Results:
Thirty-five subjects (23F, 12M; mean age 58.5+/-16.6yrs) with MGD were compared to healthy controls (5F, 6M; 36.2+/-7.9yrs): the frequency of DEM was 77% and 64% respectively. Significantly more patients presented with CD coincident with DEM in the MGD group compared to controls (p<0.005): CD and DEM were observed together in 24 patients with MGD (69%), whereas in controls, CD and DEM were coincident in only 2 subjects (18%). The number of Demodex parasites found ranged from 1-33 in the MGD cohort (median 7 parasites) and from 1-4 (median 1 parasite) in the control group. There was no correlation between Demodex count and VAS for discomfort amongst blepharitis patients (r2=0.057; p>0.05).
Conclusions:
Demodex occurs in both asymptomatic subjects as well as those with recalcitrant blepharitis, and is more likely to occur in the presence of CD in MGD patients. Until effective treatment for the eradication of Demodex is available its role in MGD remains uncertain.