Influence of Demodex Infection in the Occurrence and Prognosis of Keratitis in Patients With Meibomian Gland Dysfunction Related Dry Eye

Aims/Background: Meibomian gland dysfunction (MGD)-related dry eye results in reduced tears, unstable tear film, ocular surface damage, and even causes keratitis. Demodex infection causes inflammatory diseases of the ocular surface. This study aimed to explore the impact of Demodex infection on the occurrence and prognosis of keratitis in patients with MGD-related dry eye. Methods: A total of 122 MGD patients who visited the Department of Ophthalmology, The First People’s Hospital of Chun’an County from June 2022 to June 2023 were selected for retrospective study. Patients were divided into keratitis group (n = 65) and non-keratitis group (n = 57) according to the presence of keratitis. MGD patients with keratitis were followed up for one year, and divided into good prognosis group (n = 36) and poor prognosis group (n = 29) based on their prognosis. The Demodex infection status and ocular surface parameters were detected in these two groups of patients. Logistic regression was adopted to analyze the influencing factors of keratitis complicated with MGD. Results: The positive rate of Demodex infection in the keratitis group was 81.5%, which was significantly higher than that in the non-keratitis group (35.1%, p < 0.05). Compared with non-keratitis group, keratitis group had reduced tear film break-up time (BUT), and increased corneal fluorescein staining (CFS), meibomian gland (MG) dropout, and plugging of MG orifices (p < 0.05). Logistic multivariate regression analysis showed that Demodex infection (odds ratio [OR]: 6.209, 95% confidence interval [CI]: 2.101–18.348), CFS (OR: 2.627, 95% CI: 1.562–4.416) and plugging of MG orifices (OR: 3.174, 95% CI: 1.616–6.235) were independent risk factors for keratitis in patients with MGD-related dry eye (p < 0.05), and BUT (OR: 0.768, 95% CI: 0.606–0.972) was a protective factor (p < 0.05). The age and MG expression in the good prognosis group were lower than those in the poor prognosis group (p < 0.05). No significant difference was observed between the good prognosis and poor prognosis groups in patients with Demodex infection (p > 0.05). Conclusion: The positive rate of Demodex infection is higher in patients with MGD combined with keratitis. Demodex infection, CFS and plugging of MG orifices are independent risk factors for keratitis, while the tear film BUT is a protective factor in MGD-related dry eye patients. Demodex infection does not affect the prognosis of keratitis.