What is the cornea?
The cornea is a pristinely clear front surface of our eye. It acts as a protective surface as well as the window of the eye, allowing light to pass through to the lens. This light then goes onto the retina and then the brain to form an image. The normal surface of the cornea is smooth and covered by a thin tear film which allows the light rays to pass undistorted to the retina enabling the brain to perceive a clear image.What happens when the shape of your cornea changes- The clarity of the image is lost and it may appear distorted!
CORNEAL TRANSPLANTATION:
Corneal transplantation is the most successful organ transplantation.It is recommended for people who have:
- Vision problems caused by thinning of the cornea, usually due to keratoconus (when less invasive treatments are not an option)
- Scarring of the cornea from severe infections or injuries
- Vision loss caused by cloudiness or swelling of the cornea usually due to Fuchs’ dystrophy or after cataract surgery
The corneal tissue for your corneal transplant will come from a person (donor) who has recently died and donated their tissue. The donated cornea is processed and tested by a local eye bank to make sure it is safe for use in your surgery. The most common type of corneal transplant is called “penetrating keratoplasty.” During this procedure, your surgeon will remove a small round piece of your cornea. Then your surgeon will sew the donated cornea into the opening of your cornea. A newer technique called lamellar keratoplasty may be used for some patients. During this procedure, only the inner or outer layers of the cornea are replaced, rather than all the layers. This technique can lead to faster recovery and fewer complications. Visual rehabilitation after corneal transplantation typically requires 8 to 12 weeks. Glasses are most often required after surgery
Descemet stripping Endothelial Keratoplasty:
DSEK has revolutionized the corneal transplantation process and ushered in a new era of more precise and predictable results after corneal transplant. In this process only the inner layer of the cornea is transplanted and that too without any stitches. This makes the visual recovery faster and also the spectacle power is minimal.Deep Anterior Lamellar Keratoplasty (DALK)
This kind of keratoplasty is done in cases of keratoconus and corneal scars. In this highly skilled surgery, only the anterior portion of the cornea is replaced keeping a single innermost layer called the Descemet-endothelial complex intact. The biggest advantage of this procedure is that there is no risk of graft rejection after this procedure.ARTIFICIAL CORNEAL TRANSPLANTATION
For many patients, corneal transplants offer a way to restore vision following injury or other disease-related and congenital forms of blindness. The traditional method for this procedure is to suture natural human corneal tissue from a donor eye into a recipient eye. In some cases, however, traditional corneal transplants fail, or a patient may not be a good candidate for natural tissue transplant due to special circumstances. When natural cornea transplant is not an option, more and more physicians are recommending artificial corneas, or keratoprosthesis, to restore precious vision.The Boston Keratoprosthesis is an"artificial cornea" that can be used in severe corneal opacity. Many people with corneal disease can be helped by regular corneal transplantation involving tissue transplanted from human donors. This is the most common treatment for severe corneal opacity; however, in some cases such transplantation rapidly fails. Thus, the Boston Keratoprothesis can be used after standard corneal transplant has failed or when such a transplant would be unlikely to succeed. The keratoprosthesis implantation is a procedure designed to help patients whose conditions are the most difficult to treat.
The Boston Keratoprosthesis has been under development since the 1960s, and has been gradually improved. It received FDA clearance in 1992. Over 1200 implantations have been performed (Spring 2007). It is the most commonly used artificial cornea in the United States and in the world.
The keratoprosthesis is made of clear medical grade plastic with excellent tissue tolerance and optical properties. It consists of three parts but when fully assembled, it has the shape of a collar-button. The device is inserted into a corneal graft, which is then sutured into the patient's cornea like in standard transplantation. If the natural lens is in place, it is also removed. Finally, a soft contact lens is applied to the surface.
Generally, indicators of patients who require the Boston Keratoprothesis include:
- Failed corneal graft, with poor prognosis for further grafting
- Vision less than 20/400 in the affected EYE.
- No end-stage glaucoma or retinal detachment.
Prior to surgery, a detailed history will be taken by the performing surgeon. This helps to assess the corneal condition and determine if the patient is a good candidate for the surgery.
Surgery
The surgical procedure is performed on an ambulatory basis with the patient returning home - or to a hotel if the patient is coming from a distance - the same day. Most surgeries are performed with the use of local anesthesia, with the exception of infants and young children where general anesthesia may be indicated. Patients can expect to be in the operating room area for at least three hours for this procedure, including one hour and 20 minutes for surgery as well as pre-operative and recovery time.Follow-up Care
Because of possible complications that can result after many surgical procedures, patients with keratoprosthesis require relatively frequent ophthalmologic examination in the beginning. In all cases, patients return to the Boston Eye Group the day following surgery for reevaluation, necessary prescriptions, and post-operative care instructions. Additional follow-up exams are usually during the first and second weeks after surgery. It is customary to return bimonthly for a check-up during the first year. After this time, examination by the surgeon every three to four months is also recommended.With keratoprosthesis, best possible vision is restored quickly and patients often achieve optimum visual levels within a few weeks after the surgery. Because the prosthesis is made of synthetic materials that never totally become incorporated into the body, prophylactic antibiotic drops must be used indefinitely. Thus, a life-long regimen of daily drops of antibiotics is prescribed to prevent infection. In addition, medications to control inflammation and/or glaucoma are used when necessary. Also, during the early months following surgery, a protective shield is worn while patients sleep at night. For long-term postoperative safety it is recommended that the patient continuously wear a therapeutic soft contact lens (not felt by patient).