What Is The Cornea?
The cornea is the eyeâ€™s outermost layer. It serves as a window protecting the eye from dirt, germs, and other materials that could harm the eye. The cornea allows light to enter the eye, pass through the lens, and be received by the retina where it is transmitted to the brain through the optic nerve. The cornea provides approximately 65 to 75 percent of the eyeâ€™s focusing power. Most refractive errors such as nearsightedness, farsightedness and astigmatism are due to the abnormal shape of the cornea. If there are any abnormalities affecting the cornea (such as cloudiness), it can result in blurry vision due to the image not being clearly focused.
The cornea has five layers (front to back):
- Corneal Epithelium – The outer layer of the cornea which is five to seven cells thick. It makes up nearly 10 percent of the thickness of the cornea and continually replenishes itself.
- Bowmanâ€™s Layer – This is a very thin fibrous layer that connects the corneal epithelium and the underlying stroma.
- Corneal Stroma – This make up approximately 90 percent of the thickness of the cornea. The regular arrangement of collagen fibrils over the entire cornea enables the cornea to be perfectly clear.
- Descementâ€™s Membrane – This is a very thin layer separating the stroma from the endothelium. It gets gradually thicker as we age.
- Corneal Endothelium – The innermost layer of the cornea. This layer is very thin, only a single cell thick. The endothelium pumps fluid out of the cornea to keep it clear.
Symptoms of a Cornea Disorder Can Include:
- Redness or inflammation in the eye
- Headache, nausea, fatigue
- Pain in the eye
- Sensitivity to light
- Reduced or blurry vision
- Stinging or burning in the eye
- Tearing or watery discharge
Commonly Treated Corneal Conditions:
- Corneal Scars
- Corneal Infections
- Injuries or Scratches to the eye
- Fuchs Dystrophy
- Ocular Surface Diseases and Cancers
A corneal transplant is necessary when oneâ€™s vision is lost from the cornea becoming damaged by a disease or traumatic injury. During a corneal transplant (also commonly referred to as keratoplasty), the diseased or damaged cornea is surgically removed from the eye and replaced with the cornea from a donor. The donorâ€™s cornea is sewn into place to make sure it remains stationary throughout the recovery process. Anesthesia will be used during the procedure to ensure that the surgery is painless.
Recovering from a corneal transplant may take some time and most pain medicine should be able to help relieve any discomfort during the recovery process. The stitches will remain in the eye for six to twelve months after the surgery and eye drops must be used to assure proper healing. Low doses of steroid eye drops are often prescribed on a permanent basis to prevent rejection from the new cornea.
Keratoconus is a progress eye disease where the cornea becomes thin and begins to bulge into a cone-like shape. This change in the corneal shape alters light entering the eye and causes distorted vision. Keratoconus can make it difficult for a person to operate a vehicle, read, and watch television.
Traditionally, the treatment of keratoconus consisted of glasses, contact lenses, or corneal transplantation for severe disease. Now, corneal cross-linking may prevent progression and avoid the need for a transplant. If you have keratoconus it is very important not to rub your eyes.
Fuchs’ dystrophy may run in families, although the genetic basis of the eye disease is complex. In Fuchs’ Dystrophy, the innermost layer of cells in the cornea undergo degenerative changes. Normally this cell layer, called the endothelium, regulates the correct amount of fluid in the eye and prevents corneal swelling. As the cornea swells from extra fluid, ones vision worsens.
There is no known prevention for Fuchs’ dystrophy. Thankfully, most patients maintain good vision without treatment.
Once Fuchs’ dystrophy reaches a point where it significantly impairs a patient’s vision, a doctor can perform a cornea transplant to help restore vision. A transplant to only the inner endothelial layer of the eye can be an alternative to a full corneal transplant. The procedure options, DSAEK or DMEK, replace the affected cells in the inner endothelial layer while keeping the outer layer of the eye intact. This provides the patient a safer and faster visual recovery.