In corneal dystrophies, one or more parts of the cornea lose their normal clarity due to a buildup of cloudy material. There are over 20 corneal dystrophies that affect all parts of the cornea. These diseases share many traits:They are usually inherited. They affect the right and left eyes equally. They are not caused by outside factors, such as injury or diet. Most progress gradually. Most usually begin in one of the five corneal layers and may later spread to nearby layers. Most do not affect other parts of the body, nor are they related to diseases affecting other parts of the eye or body. Most can occur in otherwise totally healthy people, male or female.
Corneal dystrophies affect vision in widely differing ways. Some cause severe visual impairment while a few cause no vision problems and are discovered during routine eye examination. Other dystrophies may cause repeated episodes of pain without leading to permanent loss of vision.
Some of the most common corneal dystrophies include Fuchs' dystrophy, keratoconus, lattice dystrophy, and map-dot-fingerprint dystrophy.
This answer is based on source information from the National Institute of Diabetes and Digestive and Kidney Diseases.