A close up of a man's eye

The cornea is the eye’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 eye’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):

  1. Corneal Epithelium – The outer layer of the cornea is five to seven cells thick. It makes up nearly 10 percent of the thickness of the cornea and continually replenishes itself.
  2. Bowman’s Layer – This is a very thin fibrous layer that connects the corneal epithelium and the underlying stroma.
  3. Corneal Stroma – This makes 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.
  4. Descemet’s Membrane – This is a very thin layer separating the stroma from the endothelium. It gets gradually thicker as we age.
  5. 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.
Diagram of the Structure of the Cornea

Symptoms of
Cornea Disorder:

  • Redness or inflammation in the eye
  • Headache, nausea, fatigue
  • Pain in the eye
  • Sensitivity to light
  • Reduced or blurry vision

  • Scratchiness
  • 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
  • Inflammation
  • Pterygium
  • Ocular surface diseases

Corneal Transplant

A corneal transplant is necessary when one’s vision is lost from the cornea becoming damaged by 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 donor’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.

Corneal Diseases and Common Eye Disorders

The cornea is a clear rounded surface on the front of the eye through which light enters the eye and enables us to see. Some of the major types of corneal disease are keratoconus, Fuchs’ endothelial dystrophy, and bullous keratopathy.

Fuchs' Dystrophy


Corneal Ulcers

Corneal Abrasions