Morphological evaluation of normal human corneal epithelium

Area of Science:

• Ophthalmology
• Histopathology
• Corneal Science

Background:

• The human corneal epithelium is typically characterized as a regular, stratified squamous, non-keratinized cell layer approximately 50 μm thick.
• This layer is generally understood to consist of 5-7 cells in thickness.

Purpose of the Study:

• To systematically re-evaluate the histopathological characteristics of 100 human corneas.
• To compare observed corneal thickness and morphology against established in vivo and ex vivo data.

Main Methods:

• Histopathological analysis of 100 paraffin-embedded corneas using hematoxylin-eosin and Periodic Acid-Schiff (PAS) staining.
• Evaluation of 5-μm-thick corneal sections via light microscopy.
• Corneas were sourced from eyes enucleated due to choroidal melanoma and considered 'normal' for the study.

Main Results:

• Evaluated 90 out of 100 corneas; measured central epithelial, stromal, and total corneal thickness at 36.0 μm, 618 μm, and 651 μm, respectively.
• Observed pathological alterations in 27% of corneas, including thickened basement membranes and changes in Bowman's membrane.
• No intraepithelial microcysts, characteristic of Meesmann corneal dystrophy, were identified.

Conclusions:

• The measured total corneal thickness exceeded previously reported in vivo values, with greater variability, potentially due to tissue preparation artifacts like swelling or dehydration.
• A significant proportion of 'normal' corneas exhibited pathological findings, suggesting that healthy eyes may harbor and accumulate substantial pathology.
• These findings necessitate a revised understanding of corneal normality and pathology in histopathological assessments.