To help you better understand the diseases that impact the cornea, we would like to provide you with some basic information about the cornea, including a description of the layers typically impacted by Corneal Diseases. The Cornea is the clear, outer covering of the eye. The cornea is responsible for approximately two thirds of the focusing power in the eye, which is why conditions that impact the cornea can threaten your vision.
The corneal epithelium is the outermost layer of the cornea and is responsible for providing protection against injury and infection. The surface of the epithelium is very smooth and provides support for the tear film, which is the first refractive component of the eye. A corneal abrasion is a minor but very painful eye injury. When an abrasion occurs, the corneal epithelium is disrupted exposing underlying corneal nerves. However, the epithelial layer can heal in only a few hours making it one of the fastest healing parts of the body.
Under the epithelium is Bowman's Layer, which is the biological glue that holds and supports the epithelium. This layer is composed of strong collagen fibers and helps to provide structural support for the shape of the cornea. Any injury that penetrates deeper than Bowman's layer will typically produce a scar or opacity in the cornea.
The corneal stroma makes up about 90% of the thickness of the cornea. The stroma is made up of collagen fibers and contains keratocytes, cells than can aid in healing after injury or infection. Corneal collagen fibers are precisely aligned to maintain corneal clarity. Interestingly, the sclera is made of exactly the same collagen fibers that make up the cornea. However, in the sclera the collagen fibers are arranged haphazardly and thus the opaque and white appearance. The crystal clear cornea is certainly one of the “miracles” of the human body.
Descemet's membrane is a thin acellular layer that supports the underlying endothelium. The endothelium is a very important layer of cells that is responsible for pulling fluid out of the cornea and maintaining corneal clarity. Fuchs Dystrophy is a disease characterized by an unhealthy endothelium and thus a swollen, cloudy cornea. DSEK (Descemet's Stripping Endothelial Keratoplasty) and DMEK (Descemet’s Membrane Endothelial Keratoplasty) are relatively new surgical techniques which involves replacing only the back layers of the cornea, instead of full-thickness corneal transplant surgery.