The relationship between demodex and ocular discomfort.

PURPOSE To determine the correlative relationship between the prevalence of Demodex in eyelashes and the severity of ocular discomfort, by investigating the demographic epidemiology associated with Demodex. METHODS One hundred seventy patients underwent epilation of four eyelashes of each eye, and the number of Demodex was counted. The patients answered questionnaires about ocular surface discomfort and underwent ophthalmic examinations, including slit lamp, tear film breakup time (BUT), Schirmer test, and microbial culturing. The correlative relationship between the number of Demodex and these variable data was analyzed. RESULTS Demodex was found in 120 (70%) of the 170 tested patients. Of 1360 eyelashes, 740 (54%) had Demodex. There was no significant difference in the prevalence of Demodex between males and females (P = 0.35). The number of Demodex showed significant positive correlations with increased age, ocular discomfort, and 1/BUT (P < 0.001), but not with the Schirmer scores. The number of Demodex was significantly higher in patients with conjunctival papillary hypertrophy than in those without (P = 0.003). The presence or distribution of bacteria on eyelashes was similar between eyelids with and without Demodex. However, methicillin-resistant Staphylococcus aureus (MRSA) was detected more often on eyelids with Demodex, but this difference was not statistically significant. CONCLUSIONS There is a strong correlation between the number of Demodex and the severity of ocular discomfort, suggesting that Demodex plays a pathogenic role in the ocular discomfort linked with aging.