Structural variations in a patient’s meibomian glands may impact their function and adversely impact the ocular surface and tear film, an international team of researchers report.

Their study enrolled 150 participants who underwent comprehensive exams that included tear osmolarity, tear meniscus height, bulbar conjunctival hyperemia, noninvasive tear film break-up time, lid margin thickness, foam secretion, meibomian gland expressibility, functioning gland count, corneal and conjunctival staining, fluorescein break-up time, lid wiper epitheliopathy, Schirmer test and the Ocular Surface Disease Index (OSDI) questionnaire. Researchers also examined meibography images for estimated dropout area, number of glands, gland length and width, and any gland irregularity.

The investigators defined gland irregularity as any shape dissimilarity from a standardized regular gland (determined by averaging that of 300 glands), represented as a percentage. They found gland irregularity had a high correlation with dropout area and showed significant partial correlations with fluorescein break-up time and OSDI scores.

Because longer glands were identified as irregular in this study, the researchers decided to divide the subjects with a dropout area of less than 32% into two groups—high and low irregularity—to compensate for the fact that longer glands tend to have less dropout area. They found gland expressibility was significantly different between the two groups. In the high irregularity group, gland irregularity correlated with the Schirmer test and corneal fluorescein staining, suggesting that compromised gland secretion triggers a tearing reflex, they noted in the study.

Although the researchers noted in their study that automated morphological analysis of gland structure provided important information, they noted that “isolated morphological characteristics of meibomian glands could not produce a complete assessment of gland function.”

Instead, a composite score that incorporates several different meibomian gland morphological features may prove far more useful when assessing the meibomian glands for signs of dysfunction, the researchers concluded.

Llorens-Quintana C, Rico-Del-Viejo L, Syga P, et al. Meibomian gland morphology: the influence of structural variations on gland function and ocular surface parameters. Cornea. September 6, 2019. [Epub ahead of print].