What Is Cornea?
Cornea is that clear front part of the eye orbit, which separates the inside of the eye from the outside environment like a window. Cornea plays two significant roles: the first is guiding light beams into the eye and concentrate them on the retina. Secondly, it protects the structures inside the eye orbit.
In order for the light to enter the eyes and reach the retina, first it should cross the cornea. Therefore, transparency of cornea is very important for vision. Just like seeing objects from behind a dirty window as blurry, if we see objects from behind an opaque cornea, we will see them blurry. In addition, again as with distortion of objects from behind a wavy or stained glass, if the corneal surface is uneven, the images are also observed as distorted. Therefore, existence of a healthy and transparent cornea with smooth surface and natural curves is essential for normal vision. In many cases, corneal transplantation is performed for removing the opaque parts of cornea and substituting it with transparent cornea.
As mentioned earlier, one of the important duties of cornea is protecting the structures inside the eye orbit. In cases when a puncture develops in the cornea due to infection or burning, there is possibility of damage and contamination of tissues inside the eye. In this state, to protect the structures inside the eye, the creative puncture should be repaired as soon as possible, for which corneal transplantation is a suitable method.
What is corneal transplantation?
Corneal transplantation is a surgical operation through which they damaged part of the patient's cornea is removed and is replaced with a new healthy cornea. Corneal transplantation is usually performed for the following reasons:
- developing better vision in cases when corneal turbidity has caused blurred vision
- preparing corneal puncture to protect the structures inside the eye orbit
- treating painful eyes in cases when severe pain exists due to disease or inflammation of cornea
- uprooting infection in cases when corneal infection does not respond to pharmacotherapy.
What are the diseases for which corneal transplantation is performed?
The most common diseases treated by corneal transplantation include:
corneal swelling following cataract surgery
turbidity or spots of cornea (often after frequent ocular herpes infection or microbial infections)
chemical burning of cornea
genetic diseases causing development of turbidity or swelling of cornea
Where is the place from which transplanted cornea is prepared?
Transplanted cornea is prepared following death of individuals who have been willing to help others by donating their cornea. Without philanthropy of these individuals, corneal transplantation surgery would have not been possible. The donated corneas are kept in an eye bank, in which these corneas are examined carefully in order to ensure their healthiness. In addition, all transplanted corneas are controlled in terms of diseases such as AIDS and hepatitis in order to prevent transmission of these diseases to the receiver person.
What is the procedure of corneal transplantation?
For performing the corneal transplantation surgery, typically it is required that the patient be hospitalized in hospital the day before the operation. They should also undergo the necessary examinations and tests. Usually, before hospitalization on the patient in hospital, coordinations are made for corneal reservation with the eye bank. Nevertheless, on the day of corneal operation, a suitable corneal may not be available in the eye bank for transplantation and therefore the surgery would be postponed to another day.
Corneal transplantation is usually performed with general anesthesia. Nevertheless, if due to other diseases such as cardiovascular or pulmonary disease, general anesthesia cannot be performed, the person becomes drowsy through drugs and the eye is operated with local anesthesia. In this state, the patient does not feel any pain. During the surgery, the surgeon removes a circular piece from the middle of the patient cornea using microscopic devices and replaces it with a proportional round piece from the healthy cornea of the donor, and stitch it with very fine sutures to the eye of the patient. The surgery usually lasts between one and two hours. Based on circumstances, sometimes in addition to corneal transplantation, glaucoma or cataract operations are also performed concurrently. After termination of operation, the eye is bandaged.
What is the state of eye after the surgery?
Typically, by the end of the operation, when the person recovers, they feel pain and discomfort which is absolutely natural and there is no worry. The day after the operation, the bandage is opened and the eye is examined. On the first day after the operation, their vision is absolutely blurry. This blurriness improves gradually over time. Therefore, during the first days and even weeks post operation, we should not expect a good vision. Pain, sensitivity, and tearing of the eye usually improve after 34 days. Typically, one or two days after the corneal transplantation operation, the patient is discharged from the hospital. However, up to 3 to 4 weeks the patient should refer to the ophthalmologist once every some days.
Immediately after the corneal transplantation, the eye is extremely sensitive to trauma, and even with very mild strikes, it may get damaged seriously. Therefore, in the early weeks following the transplantation, you should definitely use a plastic protector (shield), in order to prevent any trauma to the eyes. Further, during this period, you should avoid bending, exerting pressure, and picking heavy objects. Again, you should not bend your head forward. If you have to pick up something from the ground, never bend from the waist region, and bend the knees instead and keep your head straight. When washing the head, be absolutely careful to avoid entrance of water and shampoo into the eyes. The only allowable physical activity during this period is light jogging. Also, you must absolutely avoid rubbing and scratching the eyes.
If you have a sedentary job, after two weeks, you can return back to your workplace. However, if your job demands physical activity, you should wait for at least six weeks.
Since in a corneal transplantation, the tissue healing is very late, and even after healing it never has the strength of a normal cornea, it is recommended that:
Always use a large pair of glasses or sunglasses with resistant glass in order to prevent any possible strikes.
Avoid doing sports such as judo, wrestling, and soccer in which there is probably of hits.
Avoid activities in which there is probability of hits and never quarrel with anyone.
When swimming or doing typical exercises, always use special protective glasses.
Remember that if you do not follow these points, you may lose your vision.
Up to when should we use eyedrops?
Typically, after corneal transplantation, up to several weeks you should use antibiotic drops and up to several months you should consume steroid drops which can control inflammation. Sometimes other drops such as artificial tears or drops that lower intraocular pressure are also prescribed. After the operation, you must consume the drops according to physician prescription carefully and avoid stopping their usage on your will. Improper drug consumption can cause loss of the transplanted cornea and blindness.
What is the frequency of eye examinations?
On the first days following transplantation, typically examinations are performed on a daily basis. After one or two weeks, usually the interval between examinations reaches once three or four days. Gradually, this interval becomes longer, such that during the first six months, after performing the corneal transplantation, the eye examinations become repeated once every several weeks. At each visit, the ophthalmologist examines the patient in terms of magnitude of vision, status of sutures, the probability of rejection, and complications of drugs such as glaucoma and cataracts.
Note that at any time after corneal transplantation, even if years have passed the surgery, in case of incidence of any abnormal situation such as diminished vision, tearing, pain, since of physical body in the eyes, for the sensitivity, or redness of the eyes, you should refer to ophthalmologist within 24 hours at most.
When are sutures removed?
As mentioned earlier, the transplanted cornea is stitched to the eyes through a number of fine microscopic sutures. These sutures are not absorbable and should be removed at the proper time by the ophthalmologist. Nevertheless, these sutures are very delicate and the patient does not feel them. The sutures cause deformity and stretching of that transplanted cornea across different directions and develops astigmatism. Typically, after several months, to correct this astigmatism, the ophthalmologist manipulates a number of sutures or removes them. After one or two years, i.e. when the transplanted cornea was completely healed, all sutures are removed.
When does the vision become complete after transplantation?
Immediately after the transplantation, the vision is blurry and gaining complete vision may last until full healing of cornea and removal of all sutures (i.e. up to two years). During the first months after transplantation, the vision is variable and waxes and wanes. For this reason, in the early months, even use of medical eyeglasses may not help in vision. After several months, usage of proper medical glasses or hard contact lens can improve vision. Eventually, in a few number of patients, a second time surgery should be performed on the transplanted cornea in order to mitigate astigmatism and improve the vision.
The problems and complications of corneal transplantation
The most common major complications following corneal transplantation is development of astigmatism (improper curvature of cornea), which usually improves by adjusting and removing sutures and using glasses or contact lenses.
Another important complication is rejection of transplantation, which if not treated early, it causes turbidity of the transplanted cornea. Rejection occurs when the immune system of the patient identifies the transplanted cornea as a foreign tissue and tries to destroy it. This state can initiate two weeks after the transplantation, but it usually occurs several months later. If rejection is diagnosed early, it can be controlled with the repetitive use of steroidal drops and sometimes use of oral medications or drug injection around the eyes. However, in advanced cases of rejection, this complication may not be controlled with medications and re-transplantation may be required, whose success rate is lower than that of the primary transplantation. For this reason, it is recommended that in case of incidence of each of the following symptoms in a transplanted cornea, you should refer to ophthalmologist within 24 hours:
severe redness of the eye or around the cornea
Sense a foreign body which can be due to detachment or rupture of sutures.
Other major complications of corneal transplantation are not very common. Nevertheless, complications such as intraocular hemorrhage, infection, cataract, glaucoma, relapse of previous disease in the transplanted cornea, and rupture of retina may occur.
The outcome of corneal transplantation
The outcome of this operation is largely dependent on the initial disease for which the corneal transplantation has been performed.
In individuals who have undergone surgery due to keratoconus, non-infective spots of cornea, and mild swelling of cornea, the success rate is very good and around 90%. In cases when the corneal transplantation has been performed due to spots caused by herpes or severe swelling of cornea, again the success rate is above 80%. On the other hand, in emergency cases when the corneal transplantation is done for controlling infections or repairing perforation of cornea, the probability of transplanted cornea remaining transparent is lower. Nonetheless, corneal transplantation is performed for preserving the structure of eyes.
Evidently, mentioning all details about corneal transplantation surgery is not possible in this summary. Therefore, in any suspicious cases, do consult with your ophthalmologist. Remember the following points:
Protect the eyes carefully against impacts.
Consume the medications according to the ophthalmologist order and avoid stopping eyedrops arbitrarily.
In case of incidence of pain, blurred vision, tearing, or redness of the eyes, refer to the ophthalmologist at most within 24 hours.