Imaging of Meibomian Glands in Various Species

Date

2023-05-15

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Abstract

Purpose: Meibomian glands (MG) secrete meibum, the lipid component of the tear film essential for tear stability which is disrupted during dry eye disease. Blink rate varies across species suggesting differences in tear film stability, MG anatomy, and meibum quality. Meibography is performed on humans, but little is known about MG in other species. Using ex vivo meibography we imaged and analyzed MG from various species, comparing it to blink rates. This study also investigated the effect of vitamin D on MG structure in an experimental dry eye (EDE) mouse model.

Methods: Eyelids were excised from Macaca mulatta (monkey, n=6), Mus musculus (C57Bl/6 mice, n=13), Rattus norvegicus domestica (rat, n=8), and Oryctolagus cuniculus (rabbit, n=3) and imaged using the OCULUS Keratograph 5M and ZEISS Stemi 305 microscope. Images were optimized and analyzed for MG count, length, width, and area measurements using Image J software.

Results: Qualitative comparison of the images revealed that the Stemi microscope images had high contrast but reduced resolution at the eyelid margin, a limitation not seen with the Keratograph. Anatomical properties were consistent within a species but differed between species. MG count for upper lids in monkey, mouse, rat, and rabbit were 36.8±3.9, 11.3±1.8, 13.2±1.4, and 11.5±2.1, and lower lids were 37.6±4.1, 9.66±1.9, 12.2±1.6, and 13.0±1.6. MG length for upper lids in monkey, mouse, rat, and rabbit were 3.27±0.5, 0.85±0.2, 1.38±0.4, and 1.03±0.7 mm, and lower lids were 1.98±0.4, 0.62±0.2, 1.11±0.3, and 1.6±0.3 mm. MG area for upper lids in monkey, mouse, rat, and rabbit were 41.0±27.0, 2.4±0.8., 7.94±1.5, and 20±5.4 mm2, and lower lids were 28.6±17.1, 1.34±1.2, 4.22±1.4, and 12.89±1.6 mm2. Vitamin D did not have a significant effect on MG area, gland count and gland length in the EDE mouse model.

Conclusion: Images captured on the Stemi microscope show more pigmentation in the MG tissue compared to the OCULUS keratograph. Glands from various species are relatively similar in appearance. Additional studies are needed to determine the impact of vitamin D on MG morphology in a chronic EDE mouse model.

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Keywords

Meibomian, Meibomian glands, Meibomian gland dysfunction, Dry eye, Vitamin d, Imaging, Meibography, ImageJ, Keratograph, Stemi, Microscope, Experimental dry eye, Mouse, Mice, Rat, Rabbit, Monkey, Animal model

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