Corneal Transplantation

What is the function of the cornea?

1.  Cornea is the transparent anterior portion of the eyeball, serving as the first refractive medium of the eye.
   
   
2. Cornea provides the main refractive power of the eye. Together with the lens, the cornea refracts light, accounting for approximately two-thirds of the eyes total optical power.
   
   
3. Cornea is the transparent tissue in front of the eye that covers the iris, pupil, and anterior chamber.

What is the reason for the cornea being transparent?

1. The surface of the cornea is composed of transparent non-keratinized stratified squamous epithelial cells.
   
   
2. Cornea is avascular and contains no blood vessels, thus there is no direct blood supply. The cornea gets its oxygen from the air.
   
   
3. Cell structure of the cornea is relatively homogenous and regular. The epithelium comprises 6 layers of fast growing easily regenerated cells, kept moist with tears.
   
   
4. Cornea takes in fluid from the aqueous humor and the small blood vessels in the limbus, but an endothelial pump ejects the fluid immediately upon entry which maintains the cornea’s transparency through careful fluid regulation and balance.
   
   

 Why is the cornea sometimes turbid and cloudy?

What disturbing factors cause changes in the clearness of the cornea?

1. Injury to the cornea

2. Infection of the cornea

3. Adverse Auto-Immune system reaction to the body’s defense mechanisms

4. Congenital birth defect of the cornea

5. Erosion of the endothelial cells of the cornea

6. Post operative complications from surgery

 Corneal transplantation, also known as corneal grafting, is a surgical procedure where a damaged or diseased cornea is replaced by donated corneal tissue (the graft) in its entirety (penetrating keratoplasty) or in part (lamellar keratoplasty). The graft has been removed from a recently deceased individual with no known diseases or other factors that may affect the viability of the donated tissue or the health of the recipient. The procedure is performed by ophthalmologists, and is often done on an outpatient basis.

The aims of corneal transplants are:

1. Optical. To improve visual acuity by replacing the opaque or distorted host tissue by clear healthy donor tissue.
   
   
2. Tectonic / Reconstuctive. To preserve corneal anatomy and integrity in patients with stromal thinning, or to reconstruct the anatomy of the eye, e.g. after corneal perforation.
   
   
3. Therapeutic. To remove inflamed corneal tissue unresponsive to treatments by antibiotics or anti-virals.
   
   
4. Cosmetic. To improve the appearance of patients with corneal scars that have given a whitish or opaque hue to the cornea.

What factors will influence the success of cornea transplantation?

1. Condition of the cornea of the donor
   
   
2. Condition of the eye of the recipient
   
   
3. Complications during the operation are generally related to the condition of the eye of the recipient pre-surgery.
   
   
4. Complications after the operation are generally related to the condition of the eye of the recipient pre-surgery and the execution of the surgery.
   
   
5. Reaction and rejection to the cornea of the donor.
   
   
6. Refractive status. The shape and curvature of the donor cornea may be irregular and consequently cause high astigmatism.

What is the prognosis for a corneal transplantation?

1. When the primary purpose of a corneal transplant is to improve visual acuity, the prognosis is dependent upon whether the rest of the eye is healthy. If it is, then it should be possible to recover normal vision.
   
   
2. If the corneal stroma develop visually significant opacity, irregularity, or edema, a cornea of a deceased donor can be transplanted. Because there are no blood vessels in the cornea, there are few problems with rejection of the new cornea.
   
   
3. Generally, the success rate of a cornea transplant without complication is around 80 to 90 percent.
   
   
4. There are also synthetic corneas (keratprostheses) in development. Most are merely plastic inserts, but there are also those composed of biocompatible synthetic materials that encourage tissue growth into the synthetic cornea, thereby promoting biointegration.

What are some ways to prevent the cornea from being damaged?

1. Eat food which provides good nutrition for your body. Especially good for the health of the eyes are antioxidants, Vitamin C, Vitamin E, and Vitamin A from beta carotene. Minerals such as selenium, zinc, and chromium all assist in keeping the eyes healthier. Eye herbs such as bilberry, eyebright, and lyceum can ease tired eyes and keep them healthier. Eat less sugar. Good nutrition promotes good vision and healthy eyes.
2. Look after and protect your eyes in harsh environments or the workplace. Always wear protective eyewear when using power tools, hammers, or other striking tools. Wear protective eye wear when riding on a motor bike. Always wear protective eyewear when working with toxic chemicals or welding. Wear international standard eyewear protection when working in dangerous areas with flying objects and debris. Wear international standard sunglasses to protect your eyes from harmful UV rays.
3. See an eye doctor immediately for treatment and proper medication if an eye has been injured or infected.

Eye emergencies include scratches, objects in the eye, burns, chemical exposure, and blunt injuries to the eye or eyelid. Since the eye is easily damaged, any of these conditions can lead to vision loss if left untreated.

Take prompt action if you or someone else has an eye related injury.

It is important to get medical treatment for all significant eye or eyelid injuries. An injury to the eyelid may be a sign of severe injury to the eye itself. Many eye problems, such as a painful red eye, that are not due to injury, still need urgent medical attention.

POINTS TO REMEMBER IF AN EYE HAS BEEN INJURED

* DO NOT press or rub an injured eye

* DO NOT remove contact lenses unless a rapid swelling is occurring, there is a chemical injury and the lenses did not come out with the water flush, or you cannot get prompt medical attention.

* DO NOT attempt to remove a foreign body that appears to be embedded in any part of the eye. Get medical help immediately.

* DO NOT use cotton swabs, tweezers, or anything else on the eye itself. Cotton swabs should only be used on the eyelid.

SEEK MEDICAL ATTENTION IF:

* There appears to be any visible scratch, cut or penetration of the eyeball.

* Any chemical gets into the eye

* The eye is painful and red.

* Nausea or headaches accompany the eye pain.

* There is any change in vision such as blurred or double vision.

* There is uncontrollable bleeding.

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