Assessment of size and nucleo‐cytoplasmic characteristics of the squamous cells of the corneal epithelium

Abstract

Purpose:The aim was to objectively assess size, nucleus and nucleo-cytoplasmic ratio features of squamous cells from the corneal epithelium Methods: The corneas of recent post-mortem sheep eyes were either glutaraldehyde-fixed for transmission electron microscopy or impression cytology samples taken, glutaraldehydefixed and stained with Giemsa. From the specimens for impression cytology, a representative region was photographed from 12 different samples taken from the central region and 16 different samples taken from mid-peripheral regions of the corneal epithelium. Images were subjected to morphometry after overlays were generated. Results: Electron microscopy revealed a very distinctive stratified corneal epithelium with several superficial layers, confirming the squamous phenotype. Impression cytology from such superficial layers revealed a cell size of 60.1 ± 4.8 μm, nucleus dimension of 12.3 ± 1.5 μm, cell area of 2,419 ± 416 μm 2 and nucleus area of 131 ± 31 μm 2 . A nucleo-cytoplasmic ratio based on nucleus-to-cell length had a mean of 0.207 ± 0.022, while a cytoplasm-tonucleus length ratio was 3.975 ± 0.474. Estimates of the nucleo-cytoplasmic ratio based on areas had a mean value of 0.059 ± 0.011. Very similar results were found for mid-peripheral corneal epithelium. Conclusions:The results strongly indicate that the squamous phenotype of the superficial corneal epithelial cells is characterised by a large size, large nucleus and low nucleocytoplasmic ratio. These morphological characteristics show a notable resemblance to data obtained from impression cytological studies on human conjunctival epithelial cells showing severe squamous metaplasia.

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

“…For this, a tissue block including the most anterior edge of the eyelid (and approx. 2 mm in length) was cut and processed and examined essentially as previously detailed . Overall, the goal was to obtain a few (5–10) acinar sections from each sample, cut at slightly different depths.…”

Corneal Surface and Superficial Cells as Viewed by Scanning Electron Microscopy and Impression Cytology Sampling

“…Sheep eyes, within an hour of slaughter, were obtained from a local slaughterhouse, 34,35 which were collected in closed plastic bags after being washed in cold tap water. Single eyes were selected from any particular batch based on quality (ie, no signs of corneal edema or mechanical damage) and age (based on a horizontal corneal diameter of at least 22 mm); for the 18 eyes studied, these diameters were between 22 and 23.5 mm.…”

“…Six eyeballs were processed many months apart for SEM essentially as previously detailed, 35 with the conjunctiva, limbus, and corneal surface being slightly stretched during fixation to prevent any wrinkling. The fixative was 2% glutaraldehyde in 80 mM sodium cacodylate buffer (pH 7.2-7.4, 320-340 mOsm/kg) with a few drops applied to the ocular surface every few minutes at room temperature over 90 minutes.…”

“…34,35 As with preparation for SEM, the surface was irrigated with 1% saline, and then left for 5 minutes to air dry at room temperature before IC. An IC specimen was taken using a 10-mm-diameter Biopore filter (Millicell-CM unit 0.4 PICM 012550; Millipore, Co, Cork, Ireland), fixed with the same glutaraldehyde solution used for SEM and stained with Giemsa.…”

A systematic assessment of goblet cell sampling of the bulbar conjunctiva by impression cytology

“…In brief, this involves gently stretching the bulbar conjunctiva back over the enucleated eyeball prior to the fixative application post-mortem. However, prior to the specific preparation for SEM, a narrow strip (approximately 1 mm wide) was cut from the temporal edge, and two small blocks of tissue (approximately 1 Â 2 mm) processed and examined by TEM as essentially as previously detailed (Doughty, 2012c(Doughty, , 2015. The net result is a piece of tissue (approximately 8 Â 10 mm) extending from the corneo-limbus edge, most of which was used for scanning electron microscopy (SEM) (Doughty, 2013(Doughty, , 2014.…”