Most people who have been told they might need a corneal transplant are understandably uncertain and concerned. They don't always know what to expect in terms of visual recovery, discomfort, rejection episodes and postoperative course. Most patients have mild discomfort for the first few days after surgery, and they usually return to work after about three to four days.
What is corneal transplantation?
Corneal transplantation is a surgery in which a donated tissue (cornea) is used to replace fully or part of a diseased cornea of a patient. It is by far the most commonly performed and most successful transplant procedure. Unlike other forms of transplantation, patients generally do not require any anti-rejection pills or intravenous medications, and in most cases it is uncommon for rejection to interfere with the eventual success of corneal transplants. The cornea – the “clear window” in front of the eye – usually has no blood vessels in it, so the body's immune system is unaware of the surgery. For most patients, even in a rare event of rejection, it rarely causes failure of the transplant.
What Conditions May Lead to Corneal Transplantation?
Many corneal diseases may require a corneal transplant. The usual cause is a decrease in transparency or deformation of the corneal shape that may blur vision with no improvement with glasses or contact lenses. Common corneal conditions that require transplantation surgery include keratoconus, corneal edema, and corneal dystrophies (Fuchs endothelial dystrophy).
Where do the corneas come from?
Loosing a loved one is undoubtedly devastating; a donated cornea from a healthy eye is a gift of sight that lives on. “Donor” refers to the person providing the cornea; “recipient” is the person receiving the cornea. There is no need to match the tissue, eye color or gender for corneal transplants. We usually do attempt to match the general age, especially when operating on a child or young adult, as these individuals have much longer life expectancy. It is a common misconception that, when donating the corneas, the body will be disfigured. This is not true. Only a portion of the cornea the size of a dime is donated.
Before the surgery
Your surgeon will meet with you in our office and examine you before deciding on surgery. Testing and measurements will be performed at the time of your appointment. Any questions will be answered and the informed consent (giving permission to your surgeon to perform the surgery) will be explained and signed. You will be registered in the general state line for the corneal graft. In our state, it usually takes around 3 to 6 months for the cornea to become available. You will be asked to use antibiotics and other eye drops prior to your surgery.
Leave the patch and shield on after surgery until your surgeon removes them on your first post-op visit. A “black eye” after surgery with a black and blue appearance to your lids is normal, and this will resolve over a few weeks. Mild lid swelling is also normal. A little bloody discoloration of your tears for a week or so is not cause for concern. The eye is often quite red after surgery for a few weeks. A clean, warm, wet washcloth can be used to gently clean crust from the lids. Most patients experience a foreign body sensation (as if something were in their eye) for several days after surgery. Often, the eye aches and itches and bright lights may be temporarily uncomfortable. This discomfort improves over the course of several days. At no point after the first day or two should you experience severe pain. If you experience pain that is not relieved by Tylenol, you should call your surgeon. Most patients can return to their usual routines within several days after surgery. You may even watch TV soon after your surgery. Visual recovery is gradual and depends on the surgical technique, number of stitches, the severity of the underlying disease and any associated pathology. Vision is usually discreetly better after surgery. However, final visual result can only be appreciated 6-12 months after the procedure.
The most important thing to remember is to not let anything strike your eye. You will need to wear the eye shield at night to avoid inadvertently rubbing your eye while you are sleeping. Your surgeon will tell you when to discontinue the use of this shield. Avoid lifting objects heavier than 30 pounds within the first few weeks after surgery. Also, do not bend over with your head below your waist until your doctor says you can do so. If necessary, you may take a laxative to avoid straining. Intense physical activities should be avoided for at least 1 month. Pools and saunas are also forbidden for 3 months. The most important precautions you can take to protect your eye involve wearing the shield at night and glasses (of any sort) during the day to avoid a blow to the eye, which could jeopardize the success of your surgery.
Main surgical techniques:
The cornea is composed by 5 different layers. From outside inwards, they are the epithelium, Bowman’s membrane, stroma, Descemet’s membrane and endothelium.
Each of these layers can be affected by specific diseases. Sometimes, replacing only a certain layer might be beneficial. We present the main surgical techniques used in corneal transplantation.
1. Penetrating keratoplasty (PK)
Penetrating keratoplasty is the oldest technique for corneal transplantation. All layers of the diseased cornea are replaced by the donated tissue. It usually takes around 16 stitches to secure the transplant in place. These stitches need to be removed around 12 months after surgery. In this technique, visual recovery is slow and may take up to 24 months. In 50% of the cases, rigid contact lenses might need to be used for correcting the residual refractive error. Although it is gradually being replaced by the other techniques, penetrating keratoplasty might still be used in certain diseases that affect all corneal layers.
2. Deep anterior lamellar keratoplasty (DALK)
In this technique, the outer corneal layers are the only ones to be replaced. Keratoconus and anterior dystrophies and scars that affect vision are the main indications for this technique. Its main advantage over penetrating keratoplasty is the fact that the inner most layers of the patient’s own cornea (endothelium) is preserved minimizing rejection and yielding a stronger eye. Stitches are also used to fixate the graft in place although they are usually removed earlier than in penetrating keratoplasty. Visual recovery is also gradual but it may be slightly faster than in PK. Rigid contact lenses may also be required for correcting residual refractive error after surgery.
3. Descemet stripping automated endothelial keratoplasty (DSAEK)
This technique is used when the disease is restricted to the inner layers of the cornea and only these layers are replaced. Its main indications are Fuchs endothelial dystrophy and bullous keratopathy. Both diseases cause the cornea to swell reducing vision. Fuchs endothelial dystrophy is a premature aging of the cornea in a genetically transmitted disease. Bullous keratopathy usually involves some previous intraocular surgery. DSAEK is done through small incisions (+/- 4mm) and usually requires stitches only to close this incision. They are removed 1-3 months after surgery. An air buble is used to secure the graft in place. It “pushes" the graft into the patient’s own cornea for it to be incorporated. After surgery, patients are required to posture lying down on their back for approximately 2 hours so that the air can hold the graft in the right place. The main advantage of this technique is the selective replacement of only the diseased layer of the cornea keeping the eye structural integrity and yielding a faster visual recovery, generally, 6 months after surgery.
4. Descemet membrane endothelial keratoplasty (DMEK)
This is the most advanced corneal transplant technique and it is characterized by the selective replacement of only the inner most cells of the cornea (endothelium). In DMEK, the donated tissue (an extremely thin piece of tissue of approximately 50 thousands of a millimeter) is folded and inserted into the patient’s eye through micro incisions (a little over 2mm). Once inside the eye, an air bubble is used to unfold it and to secure it in place until it is incorporated by the patient’s own cornea. No stitches are needed in most cases and visual recovery is usually much faster. Final visual outcome can be appreciated around 3 months after surgery and a significant improvement is usually present even before that. Because the transplanted tissue is extremely thin and fragile, it takes a lot of surgical skill to deal with the graft and it might be required to reinsert some air in the eye in the postoperative course. This technique is used in the initial presentation of Fuchs endothelial dystrophy and bullous keratopathy.