When the cornea becomes diseased and vision is significantly compromised, corneal transplantation may be necessary. Standard corneal transplantation with donor tissue is the most common treatment for corneal opacity. However, in certain severe corneal opacities, there is a high failure rate. An alternate treatment is the Boston Keratoprosthesis (Kpro) which acts as an artificial cornea.
The Boston Keratoprothesis can be used after standard corneal transplants have failed or when such transplants would be unlikely to succeed. Keratoprosthesis implantation is a procedure specifically designed to help patients whose conditions are the most difficult to treat.
The Boston Keratoprosthesis is made of plastic (PMMA) or titanium with excellent tissue tolerance and optical properties. It consists of three parts, which when fully assembled have the shape of a collar-button.
Indications for the Boston Keratoprosthesis include
- Failed corneal transplants with a poor prognosis for further transplants
- Vision less than 20/200 in the affected eye and compromised vision in the other eye
- No end-stage glaucoma or retinal detachment
The device is inserted into corneal donor tissue, which is then sutured into the patient’s cornea similarly as in a standard transplantation. If the natural lens is in place, it is also removed. Finally, a soft contact lens is applied to the surface.
The surgery generally requires less than 1.5 hours to complete and is often performed under local anesthesia with intravenous sedation. After surgery, a soft contact lens which does not cause discomfort must be worn around the clock, every day. Use of a coloured contact lens to match the iris color of the opposite eye is an option. Improvements in vision are usually noted the following day or week(s).
Because of possible complications that can result after corneal surgery, patients with keratoprosthesis require frequent ophthalmologic examinations in the beginning of postoperative care. Patients are normally seen the day following surgery, as well as during the first and second weeks after surgery. Bimonthly check-ups are recommended during the first year. After this, examination by the surgeon every three to four months is normally performed.
For long-term postoperative safety, patients will continuously wear the soft contact lens and use antibiotic drops daily to prevent infection. In addition, medications to control inflammation and/or glaucoma are used, as necessary.
Stability and Safety
The Boston Keratoprosthesis is known for excellent long-term stability and safety, and it can provide normal vision for as long as the rest of the eye remains undamaged.
The surgery is reversible at any time.