What is cornea and why do it have importance?‎

The cornea is the clear front surface of the eye and like a complete clear ‎window, allows light to enter the eye. The color of the eye is not correlate to it. ‎The cornea is able to refract the light because of its special refractive index and ‎curvature, which focuses the images of distant and near objects on the retina ‎through the lens of the eye and person can see objects.‎

Corneal transplantation‎

Corneal transplantation is a surgery in which all or part of a damaged or ‎diseased cornea is replaced by donated corneal tissue. The donated cornea has ‎been examined and tested by the Eye Bank and its health has been fully ‎ascertained. Corneal transplantation is usually performed with complete ‎anesthesia.‎

  • Corneal transplantation and common methods
  • Types of Partial Thickness Corneal Transplant
  • Causes of corneal transplantation‎
  • Patients eligible for corneal transplant surgery
  • Procedure for transplanted cornea
  • The corneal transplantation process
  • Essential postoperative care
  • Important recommendations after corneal transplantation‎
  • Clinical and pharmaceutical care
  • Result of corneal transplantation
  • Corneal transplant problems and complications
  • Duration of surgery

‎1- Full-thickness corneal transplantation: In this case, the full-thickness cornea ‎is removed in the affected area and replaced with a healthy cornea.‎

‎2- Partial Thickness Corneal Transplant: In this method, only the damaged and ‎damaged layer of the cornea is removed and the healthy layer is transplanted ‎instead.‎

‎1- ALTK Anterior Layer Transplant: Only the superficial layer of the damaged ‎cornea is removed and replaced with the same portion of the transplanted ‎cornea.‎

‎2- DALK Anterior and Middle Layer Transplantation: Used in cases where the ‎patient has extensive disorder in the superficial and upper layers.‎

‎3- Posterior Layer Transplantation DSAEK: Used in cases who has a disorder ‎of the deep layer (endothelium) and the superficial and middle layers remain ‎intact. The thickness of donated layer is about 1 to 2 microns.‎

‎4- Posterior DMEK Layer Transplantation: it is another method of ‎endothelium transplantation, in which a very thin membrane is grafted with a 1 ‎to 2 microns thickness of corneal layer. ‎

‎1- To increase visual acuity in keratoconus patients, because failure to perform ‎this procedure may lead to progressive decrease of vision, thinning of the ‎cornea and even can cause corneal rupture.‎

‎2- To Improve vision in patients with corneal opacity

‎3- For Maintain of ocular integrity after severe corneal rupture by accident‎

‎4- In cases of severe infections

‎5- To improve the unpleasant appearance of the cornea due to corneal staining, ‎corneal transplantation would be the only solution in patients who has ‎cosmetic contact lens intolerance and lack of stabilization in color of contact ‎lens.‎

‎1- Keratoconus disease (keratoconus)‎

‎2- Having corneal edema after cataract surgery or other intraocular operations

‎3- Hereditary diseases that cause corneal opacity or edema.‎

‎4- Opacity or staining of the cornea, usually caused by recurrent ocular herpes ‎infection or microbial infections.‎

‎5- Chemical burns of the cornea

Transplanted cornea is made by those who are willing to donate corneas to ‎help others Post-mortem. So corneal transplantation may not do without the ‎benevolent action and consent of these patients.‎

All donated corneas in the eye bank are carefully examined to ensure they are ‎healthy. Also, all transplanted cornea will be controlled for diseases such as ‎AIDS and hepatitis… until these diseases won´t spread to the recipient.‎‎

Note: The cost paid to the eye bank is for corneal examinations, tests and ‎preservatives.‎

For transplant surgery, it is usually necessary for the patient to undergo the ‎tests and examinations. Eye surgery is usually performed before the patient ‎arrives at the hospital for corneal reserve, but however, on the day of surgery, ‎the cornea may not be available for transplantation and may be postponed to ‎another day.‎

During surgery, surgeon removes a circular fragment from the middle cornea ‎and replaces that with a round similar piece of the donor cornea, by using a ‎microscope. After that she/he blows it into the patient's eye with very fine ‎sutures. It should be noted that surgery takes between one and two hours. ‎Depending on the circumstances, sometimes corneal transplantation is ‎performed with cataract or glaucoma surgery concurrently. After the operation ‎the eye is dressed.‎

Note: Patient´s cornea and donor cornea can also be provided with a ‎femtosecond laser, which lead to increases the cost of operation due to use of ‎this device.‎

Immediately after corneal transplantation, the eye is highly susceptible to ‎trauma and may be seriously injured even with mild trauma. Therefore, one ‎month after the transplantation, be sure to use a plastic shield (shield) to avoid ‎impact. Also during this time you should avoid bending, pushing and lifting ‎heavy objects. In this time you should not bend your head forward. If you have ‎to lift something off the ground, do not bend the head, you have to bend your ‎knees and keep your head straight. When washing your head thoroughly, make ‎sure that water and shampoo do not enter the eye. The only exercise allowed ‎during this period is light walking. After surgery, scratching the eyes should be ‎avoided.‎

Note: If your job is a sit-down job, you can return to work after two weeks, ‎but if your job requires physical activity, you should rest for at least 6 weeks.‎

Since corneal tissue transplants very slowly, and never has normal corneal ‎strength after welding, the following should be done:‎

‎1- Always wear a sunglasses or a large medical eyeglasses with durable lenses ‎to prevent accidental traumas.‎

‎2- Avoid doing sports such as judo, wrestling and soccer where there is a risk ‎of being hit.‎

‎3- Avoid doing activities that are likely to hit you and do not fighting with ‎anyone.‎

‎4- During swimming or doing other daily exercises, must wear protective ‎goggles.‎

Note: Failure to observe these tips can result in loss of vision.‎

In the first few days after transplantation, examinations are usually performed ‎on a daily or daily basis. Often after one to two weeks, the intervals of ‎examinations are often weekly and gradually longer, such that the ophthalmic ‎exam is repeated every one month after the corneal transplant.‎

After 6 months, the examinations are prolonged and reach every 2 to 3 ‎months. The doctor examines the patient at any time for visual acuity, suture ‎status, possible rejection, and complications of medication such as glaucoma ‎and cataract surgery, and is re-examined every 6 months after one year.‎

Note that even after years of surgery, corneal transplantation should be ‎referred to the ophthalmologist for a maximum of 24 hours if any ‎abnormalities such as vision loss, tears, pain, foreign body sensation, phobia, ‎or redness of the eye occur.‎

You also usually need antibiotic drops for a few weeks after the corneal ‎transplant, and steroid drops that control inflammation for several months. ‎Ophthalmologists may prescribe other drops, such as artificial tears or eye ‎drops. After surgery, be sure to take the drops as directed by your doctor and ‎avoid any arbitrary discontinuation. Misuse of the drug can cause blindness ‎and loss of transplanted cornea.‎

The outcome of corneal transplantation largely depends on the primary disease ‎for which the corneal transplant has been performed.‎

In people who have undergone surgery due to keratoconus, non-infectious ‎corneal ulcers or mild corneal edema, the success rate is very good, at about ‎‎90%. In cases where corneal transplantation is due to herpes or severe corneal ‎edema, the success rate of surgery is over 80%. In emergency cases where ‎corneal transplantation is performed to control infection or repair of the ‎corneal hole, the corneal transplantation is less likely to remain clear, but ‎corneal transplantation will be done to maintain ocular structure.‎

The most common complication of corneal transplantation is the development ‎of astigmatism, which is usually improved by adjusting and removing sutures ‎and by wearing eyeglasses or contact lenses.‎

Another major complication is graft rejection which, if left untreated, will cause ‎opacification of the cornea. Graft ejection occurs when the patient's immune ‎system recognizes the transplanted cornea as a stranger's tissue and attempts ‎to destroy it. This condition can start as early as two weeks after ‎transplantation, but it will happen usually a few months later. If early ‎transplant rejection is diagnosed, or injections around the eye may be ‎controlled by repeated using of steroid drops and sometimes taking oral pills. ‎However, in advanced cases, rejection can not be controlled by the drug and ‎may require re-transplantation that its success rate is lower than the initial ‎transplantation. For this reason it is advisable to see an ophthalmologist ‎within 24 hours if any of the following symptoms occur in the eye with a ‎cornea that is transplanted:‎

‎1- Pain

‎2- Severe redness of the eye or around the cornea

‎3- Sensitivity to light

‎4- Abnormal tears‎

‎5- Blurred vision

‎6- Foreign body sensation that can be caused by loosening or tearing of ‎sutures.‎

Other major complications of corneal transplantation are less common, but ‎there are the possibility of other complications such as intraocular hemorrhage, ‎infection, cataracts, glaucoma, recurrent corneal disease, and retinal ‎detachment.‎

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