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Ho Sik Hwang, Yilu Xie, Elena Koudouna, Donald J. Brown, James Jester; Light Transmission Characteristics of the Meibomian Gland: What Does Meibography Detect?. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2238. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
While meibography has proven useful in diagnosing MGD, little is known regarding the specific spectral wavelengths that are transmitted or absorbed by the meibomian gland. The purpose of this study was to measure the spectral transmission/absorption characteristics of the meibomian gland compared to other eyelid tissues.
Human and rabbit eyelids were fixed in paraformaldehyde and serial 50 μm thick tissue sections cut using a cryotome. Sections were then mounted on glass slides and specific tissue regions (acini, muscle, tarsus and dermis) illuminated within a 100 μm spot using a broad spectrum light source (OSL2 and OSL2BIR, Thorlabs, Newton, NJ). Transmission/absorption spectra over a 550-950 nm range were then measured using a spectrometer (CCS200/M, Thorlabs, Newton, NJ). Measurements were obtained from 5-10 different tissue sections for each tissue region. Differences in absorption were compared by analyzing the area under the transmission curve using two-way analysis of variance (Student-Newman-Keuls, multiple comparison).
Bright field microscopy showed stronger light absorption in differentiated meibocytes within the acini compared to the disintegrating region of the acini, the central duct, muscle and dermis. Staining for neutral lipid showed light absorption to be related to the presence of small lipid droplets, 1-2 μm in diameter. In scattered light images, the acinus showed strong scattering compared to the muscle and dermis. In the rabbit, the acinus showed significantly less transmission of light compared to the dermis (80%, P<.001), and muscle (60%, P<.001) suggesting differences in transmittance due light scattering. For human, comparison of light transmittance through acinus showed a tenfold decrease compared to muscle (P<.01), and a one hundred fold decrease compared to tarsus (P<.001). No specific spectral region of light absorption in the infrared could be detected in rabbit and human meibomian glands compared to other tissues.
This is the first study to evaluate the spectral transmission characteristic of the meibomian gland. Overall, the data show that light transmission is dramatically reduced in the acini due to light scattering by small lipid droplets, suggesting that Meibography detects active lipid synthesis in differentiating meibocytes.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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