As dry eye disease is diagnosed based on the presence of both symptoms and clinical signs, it is therefore of interest to investigate the morphological and functional changes of meibomian glands in asymptomatic individuals and to determine the extent of these gland changes. Understanding these early gland changes in individuals without dry eye symptoms is crucial, as they could represent a preliminary stage in the progression toward dry eye disease. By recognizing and potentially managing these meibomian gland alterations early, there may be an opportunity to preserve long-term eye health, maintain optimal tear film stability, and prevent future dry eye symptoms. This evolving perspective on meibomian gland changes in non-dry eye individuals opens the door to new approaches in proactive ocular care and sheds light on the complexity of tear film and eyelid health.
This was a cross-sectional study aimed at examining the morphological and functional changes in meibomian glands among 60 non-dry-eye individuals. The study adhered to the principles of the Declaration of Helsinki and received approval from the Committee for the Protection of Human Participants in Research at the Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand (COA no. Si 367/2022). Informed consent was obtained from all subjects prior to enrollment.
This study recruited 60 volunteers, aged between 31 and 60 years from individuals who visited the Ophthalmology Department for an eye check-up, as well as from healthy volunteers who learned about the study through a flyer posted in the hospital's health check-up center. Participants were stratified into three age groups (31-40, 41-50, 51-60), with each group consisting of 20 individuals. The focus of our study centered on subjects without dry eye symptoms, identified through Dry Eye-Related Quality of Life scores (DEQS) registering at 14 or lower. To ensure the exclusion of other factors that could potentially influence meibomian gland function and dry eye symptoms, exclusion criteria include individuals with eye conditions e.g., dry eye, active ocular infections requiring antibiotic treatment, recent eye surgery performed within the past three months, previous refractive surgery, systemic diseases affecting the eyes, regular use of eye drop or artificial tears, contact lens wear, current treatment for MGD, or use of any anti-inflammatory medications within 30 days prior to the study.
The examination proceeded sequentially, starting with the measurement of lipid layer thickness (LLT) using LipiView™ II Ocular Surface Interferometer, reported in micrometers (µm). This was followed by slit-lamp observation of lid margin abnormalities, reported as the number (%) of participants, and corneal surface staining using the Modified Oxford Scale (0-5). Subsequently, three consecutive measurements of FTBUT, recorded in seconds, were conducted. Tear film production was evaluated using the Schirmer test (mm) without a topical anesthetic. The meibomian glands in the upper and lower eyelids were observed using noncontact meibography via the LipiView™ II Ocular Surface Interferometer and then converted to meiboscore. The meiboscore grades the extent of meibomian gland loss as follows: 0 indicates no loss; 1 represents loss of less than one-third of the eyelid length; 2 denotes loss between one-third and less than two-thirds; and 3 signifies loss exceeding two-thirds of the eyelid length. Lastly, a meibomian gland expressibility and meibum quality assessment was performed by pressing the eyelids with a meibomian gland evaluator, and each was graded on a 0-3 scale. All examinations were completed the same day by a single investigator. Detailed descriptions of the outcome measurements are provided in the Supplement.
Data were collected from both eyes and statistical analysis was conducted using SPSS version 29 (IBM). Descriptive statistics were reported as mean ± standard deviation (SD) for normally distributed data and median (IQR) for skewed data. Generalized Estimating Equations (GEE) were employed to compare outcomes among three age groups while adjusting for the correlation between the two eyes. The chi-square test was used to analyze categorical data. All statistical tests were two-tailed, and p-values were adjusted for multiple comparisons.