There are various types of corneal diseases. The three principal categories are Keratoconus, Fuchs’ Endothelial Dystrophy, and Bullous Keratopathy.
Keratoconus:
Keratoconus is the thinning and weakening of the central part of the cornea. In this, a cone-shaped deformity is developed in the cornea of eye. Progression of this corneal disease can be fast, progressive or periodic. Keratoconus is a corneal disease which usually affects both eyes together, but in some cases, it can also affect any single eye.
Fuchs’ Endothelial Dystrophy:
Fuchs’ Endothelial Dystrophy is kind of corneal disease which is usually a hereditary abnormality affecting the inner cell layer of the cornea called the 'Endothelium.' The primary purpose of this layer is to secrete fluids out from the cornea to keep it thin and crystal clear. When an unhealthy Endothelium does not pump out the fluids from the cornea, the cornea gets swelled resulting it to become cloudy and unclear vision.
Bullous Keratopathy:
Bullous Keratopathy is a corneal disease in which the cornea gets swollen permanently. This condition occurs due to the inner layer of cornea means the endothelium is damaged and has lost the ability to pump out the fluids out of the cornea.
Pterygium
A pterygium is a thickening of the conjunctiva or mucous membrane which overlays the white part of our eye above the cornea. This harmless or non-carcinogenic growth is usually shaped like a wedge. A pterygium normally does not create any problem or requires any special treatment. Although it should be removed if it meddles with your vision. The exact cause of pterygium is not known. It is also said that too much exposure to ultraviolet (UV) light can lead to these growth of pterygium. People whose eyes are more frequently exposed to pollen, sand, window smoke have higher possibility with having this eye problem.