Ocular Surface Squamous Neoplasia

The ocular surface is composed of the conjunctiva and the cornea. The conjunctiva is a mucous membrane which covers the globe and inner part of the eyelids. The morphology of conjunctival epithelial cells are nonkeratinized stratified epithelia which vary from cuboidal over the tarsus, to columnar in the fornices, to squamous epithelia on the globe. Goblet cells account for up to 10% of the basal cells of the conjunctival epithelia. The substantia propia of the conjunctiva consists of loose connective tissue. The cornea is a transparent, avascular tissue which acts as both the anterior eye wall and an optical media for light to enter the eye. The corneal epithelium layer is composed of stratified squamous epithelial cells and makeup about 5 % (0.05 mm) of the total corneal thickness. The corneal epithelial stem cells located at the basal layer of the limbal epithelia proliferate continuously and give rise to the superficial layer that subsequently differentiate into superficial cells. Regulation of cell growth and metabolism are critical to maintain an intact ocular surface and transparent cornea.