Recurrent Epithelial Apoptosis is a condition affecting the outermost layer of corneal cells called the epithelium. The problem is caused when the bottom layer of epithelial cells adhere poorly to the cornea, causing them to slough off easily. The pain and discomfort is often quite intense, and similar to a corneal abrasion.
Keratoconus is a degenerative disease of the cornea that causes it to gradually thin and bulge into a cone-like shape. This shape prevents light from focusing precisely on the macula. As the disease progresses, the cone becomes more pronounced, causing vision to become blurred and distorted.
A corneal ulcer forms when the surface of the cornea is damaged or compromised. Ulcers may be sterile (no infecting organisms) or infectious. The term infiltrate is also commonly used along with ulcer. Infiltrate refers to an immune response causing an accumulation of cells or fluid in an area of the body where they don't normally belong.