Keratoprosthesis
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Overview
Keratoprosthesis is a surgical procedure where a severely damaged or diseased cornea is replaced with an artificial cornea. While conventional cornea transplant uses donor tissue for transplant, an artificial cornea is used in the Keratoprosthesis procedure. The surgery is performed to restore vision in patients suffering from severely damaged cornea due to congenital birth defects, infections, injuries and burns.
Keratoprotheses are made of clear plastic with excellent tissue tolerance and optical properties. They vary in design, size and even the implantation techniques may differ across different treatment centers. The procedure is done by ophthalmologists, often on an outpatient basis.
Indications
Indications of keratoprotheses include the following:
Treatment of patients whose vision is less than 20/400 in the affected eye.
Patients with failed corneal transplant using donor cornea and have little or no vision left.
Patients with non-autoimmune diseases, congenital birth defects and other ocular problems.
Pre-operative examination
In most cases, the patient meets the ophthalmologist for eye examination and other tests weeks or months preceding surgery. During the meeting, the ophthalmologist will examine the eye and diagnose its condition. The doctor will also record the history of the patient’s health and other previous eye treatments, if any. The doctor will discuss the risks and benefits of the surgery. If the patient elects for the surgery, the doctor will have the patient sign an informed consent form. The doctor may also perform physical and lab examinations, such as an X-ray, an EKG, a slit lamp test, an ultrasound B-scan, or an A-scan.
The surgery date and time is also set, and the patient will also be told where the surgery will take place. The patient can also make any other queries regarding the procedure.
Patient selection
Vision should not be better than 20/400.
Blink and tear mechanisms should be reasonably intact.
Retina should be in place and there should not be extreme optic nerve cupping.
Opposite eye has reduced vision.
Intact nasal light projection.
Consider shunt if patient is suffering from advanced stage of glaucoma.
Procedure
On the day of the procedure, the patient will arrive to the hospital where the surgery is to be performed. After a brief physical examination, he/she will be taken to the operating room. General anesthesia or local anesthesia is given before the surgery begins.
An eyelid speculum is used to keep the eye open throughout the surgery. Some lubrication may be used to prevent the eye from drying. An incision is made at the junction of the cornea and sclera. An intralamellar pocket is created within the cornea. The artificial cornea is then inserted into the intralamellar pocket. The flap is then repositioned and the incision is closed.
Typically, there is a follow up session few days after surgery, when patients’ complaints are addressed and modifications are made, if needed.
Since Keratoprosthesis is a fairly rare surgical procedure, constant attempts are being made to improve the outcome of the surgery. Also, the material and design used in the artificial cornea may vary and as a result of this, there can be minor variations in surgical procedure as well.
The surgery is done on an outpatient basis with the patient returning home the same day.
Risks
Though the rate of success with Keratoprosthesis is high, in rare cases, certain serious complications could occur.
Glaucoma and extrusion of the implant are serious complications that could occur.
Sudden vitritis can cause a drastic reduction in vision. However, it is possible to treat this condition through antibiotics or by a minor laser surgery.
Inflammation of the eye tissue could occur. This condition is also treatable.
Prognosis
The primary purpose of Keratoprosthesis is to improve vision in patients with complex ocular diseases who are at high risk for donor graft failure. After an impressive success record with Keratoprosthesis in adults, the procedure is used to treat young patients with severe ocular deformities.
Economics of the surgery
Keratoprosthesis is continuously evolving with newer generation materials that seek to improve treatment outcomes. However, the cost of surgery is on the expensive side and can typically run up to $35,000 in the US. In order to obtain surgical treatment at a lower cost, many patients choose to get the treatment done form popular medical tourism destinations like India and Singapore where the cost of treatment may be as little as one fourth the cost as in the US or UK.
References
Sources:
http://www.stronghealth.com/services/ophthalmology/aboutus/keratoprosthesis.cfm
http://webeye.ophth.uiowa.edu/eyeforum/cases/60-AlphaCor-Surgical-Approaches-Artificial-Cornea-Implant.htm
http://www.masseyeandear.org/for-professionals/physician-resources/keratoprosthesis/care/
http://www.nice.org.uk/guidance/index.jsp?action=article&o=31194
http://www.uic.edu/com/eye/Department/News/KeratoprosthesisInformation%20.pdf
http://www.masseyeandear.org/specialties/ophthalmology/cornea-and-refractive-surgery/keratoprosthesis/
http://www.dukeeye.org/specialties/cornea/artificial_cornea-faq.html