Morphological evaluation of normal human corneal epithelium.
OBJECTIVE
The human corneal epithelium is usually described as a 50-μm-thick layer of regular stratified squamous non-keratinized cells with a thickness of 5-7 cells. The purpose of this study is systemically to revisit the histopathological appearance of 100 corneas.


METHODS
5-μm-thick sections of corneas from 100 consecutively selected paraffin-embedded eyes were stained with hematoxylin-eosin and Periodic Acid-Schiff (PAS). All specimens were evaluated by light microscopy. The eyes were enucleated from patients with choroidal melanoma. Corneas were considered to be normal.


RESULTS
Ninety of 100 eyes were evaluated. The central epithelial, stromal and total corneal thickness was measured as 36.0 μm, 618 μm and 651μm, respectively, with a variation coefficient from 0.21 to 0.22. Pathological appearances were found in 27% of corneas, including thickened basement membrane and alterations in Bowman's membrane. No intraepithelial microcysts, as found in Meesmann corneal dystrophy, were observed.


CONCLUSIONS
The total corneal thickness was higher than reported in in vivo studies and with a wider variation. This may be an effect of uncontrolled swelling and dehydration during preparation. The high number of pathological observations suggests that 'normal' eyes harbour and potentially accumulate considerable pathology.
Department of Ophthalmology, University of Copenhagen, Denmark.
Niels
N
Ehlers
Steffen
S
Heegaard
Jesper
J
Hjortdal
Anders
A
Ivarsen
Kim
K
Nielsen
Jan Ulrik
JU
Prause
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D050541:Bowman Membrane / Q000033:anatomy & histology; D003315:Cornea / Q000033:anatomy & histology; D003319:Corneal Stroma / Q000033:anatomy & histology; D019573:Epithelium, Corneal / Q000033:anatomy & histology* / Q000166:cytology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values