FIGURE 1.

Illustration of an anterior segment of an eyeball (sagittal plane) and detailed illustration of the cornea (bottom panel). The cornea is located at the very front of the eyeball (the arched light blue structure); the darker blue structure next to the cornea on the left is the anterior chamber filled with aqueous humor. The cornea has 5 layers (bottom panel), organized with the top being the outside surface and the button is the inside surface in the illustration. The epithelium is comprises of 5–7 layers of squamous cells at the outside and a monolayer of columnar cells at the inside; the Bowman's membrane is the basement membrane for epithelial cells; the stroma makes up most of the corneal thickness and is composed of highly organized collagen fibers and keratocytes; the Descemet's membrane is the basement membrane of endothelial cells; the endothelium is a monolayer of hexagonal‐shaped endothelial cells, which does not have the potential for proliferation or regeneration