Physiologie de la cornée

The optical properties of the cornea include the transmission of light, which increases with wavelength in the spectrum of visible light (400-750 nm), the light refraction (the cornea represents 2/3 of the eye total optical power), and the light reflection. The mechanisms of corneal hydration regulation involved in the maintenance of corneal transparency are complex; they involve principally the endothelial pump function which permits to maintain the corneal stroma in a relatively dehydrated state. Stromal hydration depends on the intraocular pressure, of the stromal swelling pressure, and both the barrier and pump functions of the corneal endothelium and epithelium. The mechanisms that inhibit inflammation and angiogenesis participate to corneal transparency maintenance. The maintenance of the epithelial barrier function implies the presence of limbal epithelial stem cells which continuously renew the corneal epithelium. The corneal endothelium is a very stable tissue with almost no mitosis after birth. Corneal wound healing is a complex process that involves epithelial wound healing mechanisms, stromal wound healing mechanisms, endothelial wound healing mechanisms, and stromal remodeling mechanisms. Corneal sensitive nerves are involved in the cornea-lid reflex, corneal neurogenic inflammation, and they improve the epithelial wound healing. Oxygen is taken from the ocular surface and nutriments from the aqueous humor. Drug intraocular diffusion occurs through the cornea.