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What is a cornea?
The cornea is the clear, dome shaped outermost layer that covers the frontal surface of the eyes. It helps shield the eyes from dust, germs, and other harmful matter that may enter it, and also functions as a lens that helps people focus on what they are looking at. It does this by reflecting light and sending it onto the lenses behind it.
It is made up of five basic layers that each has a function in maintaining the integrity of the eye.
- The epithelium is the outermost layer of the cornea and it is the layer that protects the eyes from foreign matter that may enter its internal parts, and it also provides a smooth surface on the eye through which oxygen and nutrients from tears can be absorbed. The epithelium is also the layer that contains the nerve endings that make it painful when something gets in the eye.
- The Bowman’s Layer lies directly underneath the epithelium and is composed of collagen fibers. When scarred, this layer can heal and regenerate with a scar, but this can cause vision impairment
- The stroma is the next layer, comprised of water and collagen, and is responsible for giving the cornea its shape, strength and elasticity.
- Descemet’s Membrane is s thin layer of collagen underneath that provide a protective barrier from injury and infection.
- Lastly is the endothelium that is a very thin layer in the innermost portion of the cornea. It pumps the fluid in and out of the stroma to maintain fluid balance in the cornea.
What are some corneal diseases that a patient can have?
- Conjunctivitis is a term that is used to describe a group of diseases that can cause significant redness in the conjunctiva that is often accompanied by burning, itching, and swelling of the membranes covering the eye and the eyelids. It is a contagious condition that can spread from one person to another, and caused by viral or bacterial infections.
- Corneal dystrophy is a condition where the normally clear cornea, or some of its parts, becomes hazy because of the buildup of a cloudy substance on its surface.
- Iridocorneal endothelial syndrome is a corneal disease that visibly changes iris and causes significant swelling in the cornea.
- Keratoconus is a progressive disorder described by the thinning of the cornea, affecting its refractive properties and decreasing the patient’s visual acuity. In severe cases, this corneal disease can cost the swelling of the cornea and produce sight-impairing scar tissues as well.
- Corneal infections occur after the cornea sustains damages from foreign material that entered the tissues causing bacterial or fungal contamination. These infections can cause painful inflammation and even keratitis that significantly reduces clear vision, produces corneal discharges, and erodes the cornea. Corneal infections often lead to corneal scarring that impairs the patient’s vision so much that corneal transplants are sometimes necessary.
What happens when the cornea is injured?
The cornea can withstand minor abrasions or injuries, and can heal itself before an infection occurs or before the patient’s vision becomes affected. Moderately deep injuries will require a longer healing time and often results to pain, tearing, redness, blurred vision, and extreme light sensitivity. However, if the cornea sustains deep injuries or deep scratches, it could result to corneal scarring that can greatly affect the patient’s vision. When this happens, a corneal transplant may become necessary.
What is a corneal transplant?
A corneal transplant is a procedure that involves the replacement of a scarred or diseased cornea with a new and healthier one. Corneal transplants become necessary when the cornea becomes cloudy or scarred so much so that light can no longer have a tracheotomy to reach the retina resulting in poor vision or even blindness.
What happens during corneal transplants?
During a corneal transplant surgery, doctors remove the cloudy central portion of the cornea and they replace it with a clear cornea that usually comes from an eye bank. To remove the defective cornea, a trephine, a surgical instrument resembling a cookie-cutter, will be used. Through the same opening, the surgeons will insert the new cornea into place. This incision will then be closed using sutures and allowed to heal for as long as necessary. After the surgery, doctors will proscribe medicated eye drops that are to be administered on the surgical site to help promote the healing for the duration of the patient’s healing process.