What is a corneal transplant and how is it performed?

Corneal transplantation is a type of eye surgery in which a donor cornea is used to replace a patient's damaged cornea. There are two main types of this transplant; if the entire cornea needs to be replaced, it is called penetrating keratoplasty. If only part of the cornea is to be operated on, a lamellar keratoplasty is used. The donor corneal tissue is obtained from an eye bank. Failure to treat a damaged cornea can cause several vision problems, such as light scattering and being deflected from its original path as it passes through the cornea, causing blurred vision or glare.

In fact, corneal diseases are the fourth leading cause of total vision loss (after cataracts, glaucoma, and macular degeneration), affecting more than ten million people worldwide each year.

Since 1961, more than one million people have regained their vision each year with corneal transplants.

When is a corneal transplant needed?

A healthy cornea is essential for clear vision. If a person's cornea is damaged due to disease or trauma, symptoms of corneal deformity, pain, vision distortion, and inflammation gradually develop.

Note: Corneal transplantation may also be used in cases such as trichiasis, a condition that causes the eyelids to turn inward and the eyelashes to rub against the eyeball, which if left untreated can lead to scarring and ultimately blindness.

This type of surgery is also recommended when prescription medications, glasses, and contact lenses fail to improve vision or relieve painful eye inflammation.

The following cases have a significant impact on corneal transparency and, if they occur, the risk of corneal loss is very high:

• Sores caused by infection, such as herpes simplex or fungal keratitis
• Wound caused by trichiasis
• Inherited diseases such as Fuchs' dystrophy
• Eye diseases such as advanced and severe keratoconus
• Thinning of the cornea and its irregular shape (such as keratoconus)
• Rare cases after surgery LASIK
• Corneal chemical burns and injury from trauma to the eye
• Excessive swelling (edema) of the cornea
• Graft rejection after a previous corneal transplant
• Loss of cornea as a result of cataract surgery

Do you meet the medical requirements to receive a corneal transplant?

People who have suffered damage and pain in the cornea due to eye trauma or disease should undergo this procedure to improve vision and reduce vision loss.

Operation time: one to two hours
Results: Significant improvement in vision
Recovery time: a few weeks to a year

Before deciding to have surgery, it is best to consider the following four questions:

1. Does your vision have a hindering effect on your professional performance at work, your abilities, and your daily tasks?
2. Are other non-invasive methods, such as contact lenses, unable to correct your vision?
3. What adverse effects does the lack of insurance coverage for medical expenses, from the pre-operative examination stage to the follow-up after the procedure, have on your current financial situation?
4. Are you able to take a work or study leave for a period of six months to a year?

Answering these questions, along with an examination and consultation with your doctor, is necessary before taking any action to perform this procedure.

Important points for corneal transplant surgery

Before corneal transplant surgery

• After a final decision is made regarding corneal transplantation, the patient's name is registered in the eye bank as an applicant for transplantation.
• The average waiting time to receive a transplant is between a few days and a few weeks.
• Before using transplanted tissue, the presence of any possible diseases such as hepatitis and AIDS is checked based on...
• To maintain the safety and health of the transplant recipient, only those corneal tissues that comply with the instructions are included in the surgical process.

During the operation پیوند قرنیه

For local anesthesia, an injection is first made into the skin around the eye to gradually relax the muscles and stop eye movement and blinking for the duration of the procedure. Eye drops are also used to numb the eye. After anesthesia is administered, a speculum is used to hold the eyelids open. Then, the doctor measures the area of ​​damage to the patient's cornea to determine the amount of graft tissue needed.

Initially, the person is placed under general or local anesthesia, in which case factors such as the patient's age, health, eye disease or injury, and the patient's own preference (whether or not to be awake during the procedure) are taken into account.

Penetrating keratoplasty, or the common corneal transplant method

In this procedure, a button-shaped circular section of the full thickness of the corneal tissue is removed using a laser or surgical instrument. Then, tissue of the same size is separated from the donor cornea and placed in place to be sutured. The sutures will remain in place for a year or more. Finally, the eye is carefully bandaged. This is an outpatient procedure and usually takes between one and two hours. After that, the person is able to return home (of course, someone must drive them there).

Eye tissue donation

Who is considered a corneal tissue donor?
What age is suitable for corneal tissue donation?

In the past decade, tissue donations from people over 65 were not accepted. However, relevant studies have shown that tissues received from people between the ages of 34-71 are completely healthy and maintain this condition for up to 10 years. The success rate in this situation is estimated to be 75%. Tissues received from young people under 34 are usually used for younger people.

Endothelial keratoplasty

In the past decade, a new procedure called endothelial keratoplasty was introduced that can be used for certain conditions.

In this surgical procedure, the inner endothelial layer is operated on while the healthy, outer corneal tissue remains intact. The epithelium is responsible for maintaining the normal fluid balance in the cornea. If this part is damaged, severe swelling will occur, leading to vision loss.

In this procedure, the surgeon makes a small incision to place the required tissue on the posterior surface of the cornea. This tissue is rich in healthy endothelial cells. An air bubble is used to ensure that the tissue is in the desired location. The incision also heals on its own and does not require stitches.

The newest type is Descemet's separation endokeratoplasty. In 2009, the American Academy of Ophthalmology declared this procedure superior to the more common penetrating keratoplasty because it provides better, more stable vision with fewer risks.

Endothelial keratoplasty has advantages over penetrating keratoplasty, including: faster vision improvement; shorter procedure time; removal of less corneal tissue; no complications from sutures; and lower risk of astigmatism.

Endothelial keratoplasty has become an acceptable treatment for many endothelial disorders and Fuchs' dystrophy. Penetrating keratoplasty is also usually necessary in cases where the entire corneal tissue is damaged.

Recovery process after corneal transplant

The maximum time required for a corneal transplant to heal is a year or more. In the first few months after surgery, the patient has blurred vision, and in some cases, even this level of vision is much lower than before surgery.

Once your vision improves, you can return to your normal activities. However, you should avoid lifting heavy objects or doing strenuous activities for the first few weeks. Depending on your job and how your vision improves, you may be able to return to work within a week.

Steroid eye drops are recommended for several months to allow the body to gradually accept the new tissue. Special medications may be needed to control infection, swelling, and other conditions. Wear plastic eye shields or goggles to prevent objects from getting into the eye or causing damage.

If stitches were used during the transplant, you can return for removal 3 to 17 months after the procedure. This depends on the health of the eye and the healing of the transplant.

Corneal transplant rejection

Corneal transplantation has become widespread and its success rate is high. It has become one of the most successful organ transplant surgeries. If transplant rejection is detected in time, most cases (9 out of 10) can be controlled and managed.

Like any other surgery, corneal transplantation is associated with potential risks. However, the improvement and restoration of a person's vision after the operation is not comparable to its adverse effects.

Side effects of corneal transplants include graft rejection, eye infections, and other issues related to the use of sutures. Graft rejection is the most important of these, occurring in 5 to 30 percent of surgeries. Graft rejection occurs when the body's immune system recognizes the new tissue as foreign and attempts to eliminate it. Research shows that glaucoma and corneal swelling, along with previous cataract surgery, increase the risk of graft rejection.

Warning signs of transplant rejection in its early stages include:

• Redness of the eyes
• Extreme sensitivity to light
• Reduced vision
• Pain

These symptoms may appear in the first month or up to several years after the transplant. These symptoms can be treated with appropriate medication prescribed by your doctor. According to the American Corneal Research Foundation, early recognition of these symptoms significantly increases the success of the transplant.

Vision after transplantation

The patient's vision begins to improve within the first few weeks after the transplant. However, it takes longer (two months to a year) for this vision to become stable. After the cornea has fully healed, the patient can undergo LASIK surgery to further improve their vision.

After recovery, the person will have some refractive errors such as myopia and astigmatism, because the curvature of the new cornea is not exactly the same as the curvature of the original cornea. Therefore, refractive errors, especially astigmatism, are inevitable. To overcome these problems, the use of glasses and contact lenses is also sufficient. Hybrid contact lenses and hard oxygen-permeable contact lenses are beneficial after transplantation. Of course, soft contact lenses can also be used.

Before you go to get glasses or contact lenses, first consult with your doctor to make sure your vision is stable.

If you wish to undergo laser surgery such as LASIK or PRK, the eye must first be completely repaired and the stitches removed from the tissue.