What is the cornea?
The cornea is the clear outer layer at the front of the eyeball and acts as a window to the eye. It has two major responsibilities: allowing light rays to enter the eye and focusing them on the retina, and protecting theintraocular structures.
The cornea allows light to enter the eye and reach the retina, thus corneal transparency has a great impact on vision. As if we look at objects from behind a dirty glass they will seem blurry, if we look at things from behind an opaque cornea, the image willbe distorted. Such as a wavy or crooked glass, if the cornea is uneven, we’ll have crooked images. Having a healthy and transparent cornea with a smooth surface and normal curvature is essential for normal vision. In many cases, corneal transplantation is performed to remove the damaged, opaque portions of the cornea and replace it with a transparent cornea.
As mentioned before, one of the most important tasks of the cornea is protecting the intraocular structures. When, due to infection or burn, a hole is created in the corneal tissue, there is a risk of destruction and infection of eye’s inner tissues. In this case, it is necessary to repair the hole immediately so as to protect the inside structures of the eyeball. Corneal transplantation is an appropriate method for this purpose.
What is a corneal transplant?
Corneal transplantation is an operation that is carried out to replace the damaged cornea with a new transparent one.
A corneal transplant is performed for one of these reasons:
• Creating better visibility in cases of blurred vision caused by corneal opacity.
• Corneal perforation repair to protect the intraocular structures.
• Relieving pain in cases where, due to diseasesor swelling of the cornea, there is severe pain.
• Eradication of corneal infection in cases which cannot be treated with medication.
Which diseases are corneal transplants performed in?
The most common diseases that can be treated with corneal transplantation include:
Where is the corneal graft provided from?
Corneal graft will come fromgenerousdonors whohave recently died and were willing to donate their tissue to help others. Without their charitable attempt, corneal transplant surgery was not possible. Donated corneas are kept in the eye bank, where all of them are inspected carefully to make sure they are safe for use in surgeries. Moreover, all the cornea grafts are controlled in terms of diseases such as AIDS and hepatitis so that these diseases will not be transmitted to the graft recipient.
It is often necessary for the patient to be hospitalized before corneal transplant surgery so that the required examinations and tests would be done.Normally prior to admission to hospital, cornea reservation has been coordinated with the eye bank.However, suitable cornea may not be available on the day of transplant and consequently the surgery will be postponed to another day.
This is usually done under a full (general) anesthetic although if your general health is poor it may be possible to use local anesthetic.In local anesthetic, medication is used to numb the area and keep the patient sedatedso that he will feel no pain.During the operation the surgeon removes a circular piece of the patient’s cornea and replaces it with a similarly sized piece of the donor's cornea.Then he sews it into place using ultra-thin stitches. It takes between one and two hours.In some cases other procedures, such as cataract or glaucoma, may be done in combination with the corneal graft. At the end of the operation, the eye will be bandaged up.
After a corneal graft, your eye is at first very vulnerable to blows on it, so it is necessary to wear a plastic eye protector(shield) during the first post operation weeks.Meanwhile you should avoid bending down, pushing or liftingheavy objects. If you have to bend down, do so slowly from the knees, keeping your head up. While washing your hair, avoid soap and shampoo in the eye.During this period, you should not take any more exercise than a brisk walk.Also avoid rubbing or scratching your eyes.
If you do a desk job, you can usually go back to work after about two weeks, but if your job is more strenuous, you will be advised to stay off work for at least 6 weeks.
Considering the fact that the cornea tends to heal very slowly and it will never be as strong as a normal eye, it is recommended that:
How long will I need drops after the operation?
Initially an antibiotic drop for a few weeks, and also a steroid drop for some months are needed to control inflammation. Sometimes other drops such as artificial tears or hypotensive may be prescribed. You must take your medication exactly as prescribed and avoid any arbitrary cutoff. Taking themedication improperly candamage the graft and cause blindness.
How often will I need to be seen after the operation?
You will be seen daily after the operation. One or two weeks later, you will be seen every 3 or 4 days, then gradually the period between visits is increased, so that in the first 6 months after keratoplasty eye examination is repeated every few weeks. After 6 months the intervals is longer (every 3 to 6 months). Each time, the doctor checks the patient in terms of visual acuity, status of the sutures, risk of rejection and medicine side effects such as glaucoma and cataracts.
You should have in mind that, even years after surgery, in case of any abnormal condition, such as loss of vision, runny eye, pain, foreign body sensation, photophobia or red eye, seek medical attention within 24 hours.
At the end…
It is evident that all the details of corneal transplant surgery cannot be mentioned here, so in any unusual case, consult your physician. Meanwhile do not forget:
Cornea transplant results
The result of the surgery depends on the initial disorder which led to cornea transplant:
Success rate is very high, about 90%, in patients who suffered from Keratoconus, cornea scars, and mild corneal swelling. In case of severe corneal swelling or ocular herpes, the success rate is still high, above 80%.In emergencies, when the transplant is performed to control the corneal infection or repair a corneal hole, the cornea transparency is less probable, however, the transplant is performed to maintain the eye intraocular structure.
Cornea transplant complications
The most common major complication of corneal transplant is causing astigmatism (inappropriate corneal curvature) which is usually improved by adjusting and removing the sutures,and using glasses or contact lenses.
Another major complication is tissue rejection, which if not treated may cause cornea opacity.This rejection results whenthe immune system recognizes the graft as being “foreign “and tries to destroy it. Rejection can start as soon as two weeks after a graft, but is commonest several months afterwards. If rejection is diagnosed quickly, it is treated with very frequent, strong steroid drops, and occasionally with steroid tablets or drip feeds.But advanced cases of rejection may not be controlled with medication complication and it may be needed to re transplantation, in which the success rate is lower than the original graft.That is why it is recommended that in case of any of the following symptoms in the treated eye, consult your doctor within 24 hours:
Other complications of corneal transplant are not very common, but there may be complications such as intraocular hemorrhage, infection, cataract, glaucoma, relapse of previous disease of graft and retinal rupture.
When are the corneal stitches removed?
As mentioned before, the graft is stitched into place with very fine microscopic stitches. These stiches do not dissolve, and should be removed in time. Of course the sutures are ultra-thin and the patient doesn’t feel them.In some cases, the sutures cause sufficient distortion of the cornea and astigmatism. Normally after a few month, doctor adjusts or removes sutures to reduce the astigmatism. After 1 or 2 years, when the graft is completely healed, all sutures will be removed.
When is the best vision regained?
Immediately after transplant the vision is blurry and regaining the best vision may take some time (up to 2 years), until the graft is healed and all stitches are removed. Therefore during the first post-operative months, even wearing glasses may not help. After a few month wearing proper glasses or contact lenses may be helpful. Alternatively few patients may have to undergo further surgeries to decrease astigmatism and improve their vision.
What will it feel like after surgery?
Typically there is postoperative pain after consciousness, however this is normal and should not cause concern. The day after the surgery, bandage is removed and the eye is examined.On the first day after surgery, vision is completely blurred. Blurred vision is improved gradually and slowly, so patients have to be patient.Pain, sensitivity and tearing of the eye usually improve after 3-4 days.Usually one to two days after a corneal transplant patient is discharged from the hospital, however, until 3-4 weeks it is necessary to be examined by a doctor every few days.