Cell size and nucleo-cytoplasmic ratios of meibocytes in the anterior acini of the upper eyelid Meibomian glands in rabbits

Objective
To assess the morphological details of the acini of the normal meibomian gland.

Animals Studied
Six young adult pigmented rabbits.

Methods
The upper eyelid was prepared in extended configuration by glutaraldehyde fixation. Tissue block sections approximately 0.5–1 mm from the eyelid margin were assessed by light microscopy in sagittal sections and transmission electron microscopy (TEM) in coronal sections. TEM images at between 1000× and 2000× magnification were enlarged onto A3-sized prints and cell size and nuclei measured by planimetry.

Results
Light microscopy sagittal sections revealed clusters of variable sized acini, sometimes appearing to be slightly overlapping and without any obvious spatial organization of the internal cells (meibocytes). The estimated areas of the acini were close to 6500 sq micron. Coronal sections, as examined by TEM, allowed for visualization of small to large acini (average diameter 82 ± 17 microns, with an estimated area of 5500 sq. microns) containing variable numbers of immature (partly differentiated) or mature (fully differentiated) meibocytes with a distinct spatial organization. The average area of the meibocytes was 158 ± 81 square microns, and they usually appeared to have a single nucleus (with an average sectional area of 29 ± 12 square microns). Within individual acini, peripherally located immature meibocytes tended to be smaller and have higher nucleo-cytoplasmic area ratios, while more centrally mature located meibocytes tended to be slightly larger and had lower or much lower nucleocytoplasmic ratios.

Conclusions
Comparative studies on meibomian glands can be undertaken with objective assessments to assess for normality or abnormality.