Surface features and morphology of bulbar conjunctival cells of bovine eyes obtained from a slaughterhouse: a scanning electron microscope and impression cytology study.

Purpose: To qualitatively and quantitatively assess the surface cells of the bulbar conjunctiva of slaughterhouse-obtained bovine eyes by impression cytology (IC) and scanning electron microscopy (SEM).
Methods: After quality-control measures and careful surface washing of recently enucleated bovine eyes over 20 min, impression cytology samples were taken from the nasal bulbar conjunctiva with a MILLCELL filter, or the ocular surface fixed in a moist chamber by a dropwise application of buffered isotonic glutaraldehyde solution. Impression cytology samples were stained with Geimsa or haematoxylin-periodate-Schiff. Fixed samples, that included the nasal bulbar conjunctiva, were prepared for SEM. From overlays of light microscope images of IC material or SEM images, cell areas, nucleus areas and cell and nucleus dimensions were measured with a digitiser pad.
Results: Impression cytology routinely showed large cells with an average area of 1035 +/- 368 microm(2), and a low nucleus-to-cytoplasmic (N/C) ratio of 0.112 +/- 0.048. The cells had dimensions averaging 46 microm (long) and 29 microm (short). Similar areas and dimensions were also found using SEM, which also showed the surface cells to have a range of lighter and darker electron reflexes and to be decorated with microplicae or microvilli. Goblet cells were not evident with either method of viewing.
Conclusions: The superficial cells of the bovine bulbar conjunctiva appear to routinely be of a squamous cell phenotype.