Is the corneal contour influenced by a tension in the superficial epithelial cells? A new hypothesis.

BACKGROUND

The corneal epithelium has a limited capacity to smooth stromal irregularities by compensatory variations in epithelial thickness.

METHODS

Cuts were made in fixed and nonfixed human and rabbit corneal epithelium with an excimer laser, and undulations were produced in the anterior stromal lining of rabbit corneas by inducing hypotony of the eye balls.

RESULTS

A retraction of the nonfixed epithelium at the edges of the cuts, and immediate small variations in epithelial thickness partly compensating for the induced irregularities in the stroma were observed.

CONCLUSIONS

A tension between the superficial epithelial cells could explain these phenomena. The balance between the pressure exerted by the superficial cell layer under tension and the epithelial growth pressure might be the factor determining the thickness of the epithelium an any point of the cornea in steady state conditions. A preliminary mathematical model and consequences for refractive surgery are presented.