Cornea Transplantation

Cornea transplant is also known as eye transplant as it is widely used in the society, and its name in the medical literature is keratoplasty. Here, only the corneal region taken from a suitable donor is transplanted, not the entire eye or different parts of it.

Cornea is the outermost colored part of the eye, located in front of the iris. It is a transparent and dome-shaped layer. Additionally, it is the layer of the eye with the highest refractivity. Its main function is to protect the eye from external factors and to function in harmony with the eye lens from birth, refracting the light coming from the outside and transmitting it to the retina. Since the rays coming into the eye first pass through this region, the transparency and formal integrity of this region is very important.

Even the slightest deterioration in the transparent and domed structure of this region due to various reasons does not ensure healthy vision. Since the tissues in this area do not have the ability to renew themselves, the need for transplantation arises.

Cornea transplantation is a surgical procedure in which the corneal layer that has lost its transparency or shape is removed by surgical intervention and the healthy corneal tissue taken from the donor is transplanted to the damaged tissue place. . It is a procedure that requires special expertise. As a result of the transplantation, all or part of the cornea can be replaced. Vision can be greatly improved after the transplantation procedure.

Cornea transplantation is performed on more than 45,000 patients every year in the USA alone.

How is Cornea Transplant Done?

Cornea transplant surgery is usually performed with local anesthesia. It can also be performed under general anesthesia in children or in patients who are not suitable for surgery under local anesthesia, depending on the decision of the surgeon who will perform the operation. First, the eyelids and their surroundings are sterilized, and then, with the help of a retractor, the eyelids are kept open throughout the operation. The surgeon who will perform the surgery determines the corneal diameter required for transplantation.

All or part of the cornea is removed. The tissue to be transplanted is placed and stitched into the recipient area using microsurgical methods. After the surgery, the eyes are closed with a protective cover.

Femtosecond laser is used in practice. Thus, better scar compatibility of the transplanted tissue is ensured.

If the transplantation procedure is to be performed together with cataract surgery, cataract surgery is performed beforehand. Keratoplasty is performed after the placement of the intraocular artificial lens. The procedure performed under the microscope takes 40-50 minutes on average.

If cataract surgery or other surgical procedures will be performed beforehand, this time may be extended. Mentioned here are the general stages of the keratoplasty procedure. The procedures applied may vary depending on the type of transplantation.

Full Cornea Transplantation (Penetrating Keratoplasty)

Penetrating keratoplasty, that is, the procedure of full corneal transplantation, aims to replace all layers of the cornea. The way the operation is performed is as follows:

First of all, the eye and its surroundings are disinfected,

The surgeon who will perform the transplant makes the necessary markings,

Then local anesthesia is applied. The center of the cornea is removed by making a circular and complete incision in the center of the cornea to the size determined by the doctor with a small circular knife.

The healthy corneal tissue to be transplanted is placed on the corneal bed.

With the techniques used in the microsurgery method. The stitching process is performed

Antibiotic medication is applied to the eye and the procedure is completed by covering the eyes with a protective cover.

Upper Layer Transplantation (DALK)

It is the process of replacing only the upper outer layer of the cornea (epithelial and stroma layers). DALK stands for deep anterior lamellar keratoplasty. Most people with corneal problems experience this problem in the outer region. It is frequently applied in cases of keratoconus and cases that do not affect the inner parts.

Since the endothelial cells in the inner part are not removed, the endothelial cells in the donor tissue are not removed. As a result, the risk of tissue rejection decreases. For this reason, the duration of cortisone medication use and the duration of stitch removal are also short. In addition, the operation time is shorter compared to full cornea transplantation.

The way the surgery is performed is as follows:

First of all, the eye and its surroundings are disinfected,

After the anesthesia procedure is performed. The eye is kept open with the help of a retractor.

Air is injected into the cornea to remove the thin outer and thick middle layers, and then these layers are removed.

Only the upper layer of the donor cornea is removed and placed on the recipient bed. ,

After the application of antibiotic medication, the operation is terminated by covering the eye with a protective cover.

Substrate Transport (DMEK)

It is a procedure that involves replacing only the lower layer (endothelium and Descemet's membrane) of the cornea, not the entire cornea. Permanent edema (bullous keratopathy) occurs in the cornea after hereditary corneal diseases and sometimes after cataract surgery. It is frequently applied after tissue deterioration caused by such a situation.

Less stitches are applied compared to other types of transplantation. The way the operation is performed is as follows:

First of all, the eye and its surroundings are disinfected, as in other operations,

After local anesthesia is applied via drops,

The bottom of the cornea is removed. The endothelial layer, which is the part of the donor, is peeled off and removed.

The endothelium previously taken from the donor cornea is placed in the donor and the stitching process is performed.

Air is injected into the eye to ensure that the tissue adheres. This air is removed in certain amounts for 1 week.

After the application of antibiotic medication, the procedure is completed by covering the eye with a lid for protection.

What are the Stages Before Transplantation?

Before the cornea transplant, the medical history of the patient who will undergo the transplant is questioned by the relevant doctor. After this stage, the patient will be asked to perform various tests to question the patient's general health status and eye health status. After this stage, it is decided whether the patient is suitable for the operation, that is, whether the transplantation process will be beneficial for the patient.

If the patient has been using blood-thinning medications for a while before the procedure, the patient may be asked to stop using these medications.

What are the risks after transplantation?

Although corneal transplantation is a very safe operation with a high success rate, it carries some risks afterwards. These are:

• Astigmatism,
• Cataract,
• Infections,
• Dry eye
• Bleeding at the seams,
• Cloudiness on new tissue,
• Blood vessels growing on the cornea,
• Eye Increase in intraocular pressure (glaucoma),
• Corneal swelling,
• Retinal detachment,
• Tissue rejection,
• Stitches after injecting air into the eye castration

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Who Can Get Cornea Transplantation?

Corneal structure is deteriorated in two basic ways. By losing its transparency and deteriorating its dome shape. In both cases, vision is significantly affected and a transplant may be needed.

In a person with an unhealthy corneal structure, these symptoms may occur in the form of light reflection, blurred vision and various light flashes.

The conditions that damage the cornea are as follows:

• Keratoconus disease progresses as a result of situations where it is not intervened or cannot be treated and disrupts the shape and transparency of the cornea,
• Loss of transparency of this area as a result of corneal edema that does not heal after cataract surgery,
• Infections that cause permanent damage as a result of keratitis, fungi, viruses and bacteria,
• As a result of traumatic and chemical injuries. In people with permanent damage to the cornea,
• As a result of Fuchs dystrophy, the cells in the inner part of the cornea die, resulting in vision loss due to swelling and thickening of the cornea,
• Some hereditary eye diseases may require transplantation,
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• Swelling of the cornea after bullous keratopathy,
• Rejection of the transplanted tissue by the body as a result of previous transplantation,

The need for transplantation may occur.

Recovery Process After Cornea Transplantation

The increase in vision level after corneal transplantation is related to the condition of the eye before the transplantation. Improvement in vision may occur between a few weeks and a few months, depending on this situation and some different conditions.

Patients are asked to come for regular check-ups on the 1st day, 1st week and 1st month thereafter, and once a month. Drops or ointments containing cortisone and antibiotics can be used for a period determined by the doctor.

It is normal to experience stinging in the eye for a few weeks after the operation.

It is important for patients to protect their eyes against various impacts during the healing process. It may take up to a year for vision to reach its maximum level.

In the future, the eye patch should continue to be worn while showering and sleeping. After endothelial transplantation, you need to lie on your back for a few days.

It may take a few months for the stitches to be removed after the operation. Your doctor may ask you to wear protective glasses during this process.

After full-thickness corneal transplantation, the corneal surface will not be perfectly round and will have an irregular structure. As a result, the problem of astigmatism arises. For this reason, glasses or contact lenses are usually used.

After the operation, driving should not be done on the day of surgery or in the following days. After regular medical check-ups, the ophthalmologist's advice on this matter should be followed. In addition, it may take a few weeks for the patient to return to work, depending on the recovery time of the quality of vision.

There is a slight possibility of tissue rejection after transplantation. Tissue rejection can be considered as the metabolism's recognition of a tissue as foreign and its attempt to get rid of it. Symptoms of tissue rejection include redness of the eyes, bloodshot eyes, sensitivity to light and blurred vision. Tissue rejection can be resolved with steroid drops and various drugs that suppress the immune system in most patients who have undergone corneal transplantation.

Where to Get Donor Tissue for Transplantation?

In cornea transplants, donor tissue is taken from deceased but healthy people and stored in eye banks. The basic function of eye banks is to store the healthy tissue taken in a suitable environment, determine its suitability for transplantation and deliver it to the center where the transplant will be made.