High Resolution Images of Human Meibum Spread on Saline

Area of Science:

• Ophthalmology
• Biophysics
• Materials Science

Background:

• The tear film lipid layer (TFLL) is crucial for understanding evaporative dry eye.
• Previous X-ray studies indicated distinct lamellar thicknesses in meibum at different temperatures.

Purpose of the Study:

• To investigate the structure of meibum spread on saline using high-resolution microscopy as a function of temperature.
• To compare microscopy findings with existing X-ray diffraction data.

Main Methods:

• Meibum from 10 subjects was analyzed using a purpose-built high-resolution color microscope.
• Meibum was spread on buffered saline at approximately 40°C and allowed to cool.
• Lamellar thickness was measured using analytical methods from previous studies.

Main Results:

• An initial irregular "island" structure was observed, with a background layer of 7.8 ± 0.3 nm.
• Dewetting led to lens-shaped droplets, which formed "tails" with multilamellar structures (4.82 ± 0.13 nm lamellae) below 30°C.
• The observed lamellar structures below 30°C matched X-ray diffraction results.

Conclusions:

• High-resolution microscopy can observe and measure tightly stacked lamellae in meibum below 30°C, consistent with X-ray studies.
• Above 30°C, the 11.1 nm lamellae seen in X-ray studies were not observed, suggesting they are not tightly stacked.
• These findings provide insights into the structural behavior of the TFLL and its potential role in evaporative dry eye.