ANATOMY AND PHYSIOLOGY

Cornea is transparent structure in front of eye. It consists of 5 layers: epithelium, bowman layer, stroma, descemets membrane and endothelium. It has refractive power of 43 diopters almost 2/3rd of eye power. It is most densely innervated tissue of body. The nutrients are supplied and waste products are removed by aqueous from inner surface and tears from outer surface.. It is non-vascularized.

The epithelium is non keratinized and stratified squamous. Basal cells are columnar, followed by two layers of wing cells and two layers of squamous cells. Epithelium has regenerative potential. 

The bowman layer is thickened layer of anterior stroma. It does not regenerate.

Stroma constitutes 90% thickness of cornea and scar in response to trauma. It does not regenerate

Descemet membrane is thick part of posterior stroma and has regenerative potential

The endothelium has pump mechanism which remove water from cornea and is important in its transparency. It does not regenerate and continuously loose cells. The adult cell density is 3000 cm2. 

Cornea is 12 mm diameter. It is 540 um thick in center and increases thickness peripherally.

Factors responsible for transparency of cornea