The cornea is essentially the “window to the eye”, and is extremely important to your vision. Though it is normally clear and healthy, there are conditions that can cause it to decompensate, such as Fuchs Dystrophy. This can cause vision loss and/or discomfort. Because the cornea has one of the highest amount of concentrated nerve endings in the human body, when it is affected it can be exquisitely painful. This can be seen in conditions such as corneal abrasions/ulcers and foreign bodies.
The cornea consists of multiple layers, like the layers of an onion. The superficial layer is the epithelium, followed by the Bowman’s layer, the meat of the cornea which is the stroma, a newly discovered layer called Dua’s layer, Descemet’s membrane, and the endothelium. They all serve different functions and disease processes that affect each layer affect the cornea in unique ways.
Superficial injuries to the cornea are like skinned knees–they heal eventually and you never know there was ever a problem since they don’t leave scars behind. Once the injury goes into Bowman’s layer and beyond, scarring forms similar to how a deep injury into the flesh leaves a scar.
Besides being clear and serving as a window, the cornea also help the eye focus images onto the retina. Conditions that cause irregularities and astigmatism like corneal degenerations/dystrophies, keratoconus and pterygia can change the prescription to a point where glasses may no longer be helpful. In cases of extensive corneal scarring, keratoconus or Fuchs Dystrophy, a corneal transplant may be necessary to regain sight.