Patients

This study was approved by the Institutional Review Board of the Affiliated Second Hospital of Zhejiang University. The research followed the tenets of the Declaration of Helsinki. In this cross-sectional study, patients with DED were recruited at the eye clinic of the Affiliated Second Hospital of Zhejiang University (Hangzhou, China) and underwent standardized assessments from June 1, 2020 to May 30, 2021 (N = 172). DED was diagnosed in accordance with the following characteristics: 1) dry eye symptoms; 2) positive corneal fluorescein staining; and 3) a Schirmer I test result <5 mm or a tear breakup time (TBUT) <5 s.

Patients were excluded from the study if they presented with conditions or factors that could confound DED and meibomian gland dropout including eyelid or ocular surface disorders, allergic conjunctivitis, glaucoma, macular degeneration, contact lens-wear, any active external ocular processes, eye tattoo history, or a history of ocular surgery. Subjects with systemic conditions knowingly associated with ocular surface disease were also excluded from the study. These included anxiety, depression, diabetes mellitus, autoimmune disease, thyroid disease, vitamin B12 deficiency, oral isotretinoin therapy, patients taking oral hormone level drugs, and patients diagnosed with obstructive sleep apnea.

Tear meniscus height (TMH) and meibography were performed by capturing infrared images with the noncontact meibography system Oculus Keratograph 5 M (Oculus, Wetzlar, Germany). The meibomian gland dropout was defined as the percentage of gland dropout in relation to the total tarsal area of the upper and lower eyelids. The patients were classified into two groups in accordance with the severity of meibomian gland dropout: (1) Non-severe meibomian gland dropout group (NSMD group; where the affected area was <1/2 of the total area occupied by meibomian glands); (2) severe meibomian gland dropout group (SMD group; where the affected area was >2/3 of the total area occupied by meibomian glands). The demographic characteristics of the patients in each group are shown in Table 1. For each individual, demographic information (age, sex, residence, level of education, working status, financial status) were collected.

Demographic characteristics of study subjects: sleep characteristics and dry eye parameters.

NSMD, Non-severe meibomian gland dropout; SMD, severe meibomian gland dropout; MG, meibomian gland; TBUT, tear film break-up time; OSDI, ocular surface disease index; TMH, tear meniscus height.