High Resolution Images of Human Meibum Spread on Saline

• Published in: Investigative ophthalmology & visual science Vol. 65; no. 8; p. 41
• Main Authors: King-Smith, P. Ewen, Begley, Carolyn G., Braun, Richard J.
• Format: Journal Article
• Language: English
• Published: United States The Association for Research in Vision and Ophthalmology 01.07.2024
• Subjects: Adult; Cornea; Dry Eye Syndromes - metabolism; Female; Humans; Male; Meibomian Glands - diagnostic imaging; Meibomian Glands - metabolism; Microscopy - methods; Middle Aged; Saline Solution; Tears - chemistry; Temperature
• ISSN: 1552-5783; 0146-0404; 1552-5783
• DOI: 10.1167/iovs.65.8.41

Understanding of the role of the tear film lipid layer (TFLL) in evaporative dry eye requires knowledge of its structure. X-ray studies show 11.1-nm thick lamellae in meibum at tear film temperature (approximately 35°C), whereas below 30°C, 4.88-nm thick lamellae predominate. Here, high resolution microscopy of meibum spread on saline is studied as a function of temperature, to compare with x-ray results. A purpose-built high resolution color microscope, previously used to study the TFLL, was used to study meibum from 10 subjects. It was spread on buffered saline at near 40°C, and allowed to cool to room temperature. Analytical methods from previous studies were applied to measure meibum and lamellar thickness. Initially, an irregular "island" was formed, surrounded by a "background layer" of 7.8 ± 0.3 nm thickness. Dewetting of the meibum layer always occurred, leading to the formation of lens-shaped droplets. Below 30°C, the lenses start to emit "tails" having a multilamellar structure containing up to about 49 lamellae superimposed on the background layer, each lamella being 4.82 ± 0.13 nm thick. Below 30°C, meibum spread on saline shows a multilamellar structure like the 4.88 nm thickness in x-ray studies, demonstrating the ability to observe and measure tightly stacked lamellae. In contrast, above 30°C, the 11.1 nm lamellae were not observed as in x-ray studies, indicating that these lamellae were not tightly stacked but may be separated by disordered lipid. The role of these findings in evaporative dry eye is discussed.