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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, glutaraldehyde‐fixed 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 μm2 and nucleus area of 131 ± 31 μm2. A nucleo‐cytoplasmic ratio based on nucleus‐to‐cell length had a mean of 0.207 ± 0.022, while a cytoplasm‐to‐nucleus 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 nucleo‐cytoplasmic ratio. These morphological characteristics show a notable resemblance to data obtained from impression cytological studies on human conjunctival epithelial cells showing severe squamous metaplasia.