A clinical study on the correlation between demodex infestation and ocular surface changes in patients with meibomian gland dysfunction

Purpose: To observe the effect of demodex infection on the ocular surface changes of patients with meibomian gland dysfunction (MGD) and analyze the correlation between the number of demodex and the changes of the ocular surface. Methods: Hundred patients with MGD aged 18-70 years who visited the dry eye center of Shanghai Aier Eye Hospital were recruited. All patients were examined with in vivo confocal microscopy to quantify the demodex and divided them into two groups (demodex negative group and demodex positive group) according to the number of demodex mites. The subjects underwent questionnaires of ocular surface disease index (OSDI) and a series of examinations. Parameters including the OSDI score, fluorescein tear film break-up time (FBUT), meibum quality, meibum gland expressibility, meibomian gland dropout (MG dropout), and ocular redness were recorded and compared between the two groups. The correlation between the number of demodex and the ocular surface changes was further analyzed. Results: Among 100 patients, 51 were positive for demodex. The demodex-positive group showed significantly increased scores of OSDI (24.41 +/- 3.43 vs 20.98 +/- 2.31, P = 0.00), ocular redness score (1.38 +/- 0.46 vs 1.00 +/- 0.30, P = 0.00), and MG dropout (3.00 +/- 1.13 vs 2.18 +/- 0.64, P = 0.00) and decreased FBUT (6.40 +/- 1.63 vs 6.54 +/- 1.83, P = 0.00), compared to the demodex-negative group. A significant correlation was noted between the number of demodex and OSDI, ocular redness, and FBUT. Conclusion: Ocular demodex infestation might play a role in the ocular surface discomfort, inflammation, and meibomian gland dropout in MGD patients. It is necessary to pay attention to the examination and treatment of demodex mite in patients with MGD.