Artificial Cornea – The Boston Keratoprosthesis
When the cornea becomes severely diseased and vision is compromised, cornea transplantation may be necessary. Many people with corneal disease can benefit from corneal transplantation involving tissue from human donors. This is the most common treatment for severe corneal opacity. However, in many cases, this treatment rapidly fails. An alternate treatment for patients with severe corneal opacity is the Boston Keratoprosthesis, which is an “artificial cornea.” It was developed by one of our leading clinician scientists, Dr. Claes H. Dohlman.
The Boston Keratoprothesis can be used after standard corneal transplant has failed or when such a transplant would be unlikely to succeed. Thus 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 improved over time, leading to its FDA clearance in 1992. Since January 2000, more than 7,000 implantations have been performed. It is the most commonly used artificial cornea in the United States and throughout the world.
The keratoprosthesis is made of clear plastic with excellent tissue tolerance and optical properties. It consists of three parts, and when fully assembled, has the shape of a collar-button.
Generally, indications for the Boston Keratoprosthesis include:
- Failed corneal graft with poor prognosis for further grafting
- Vision less than 20/200 in the affected eye and compromised vision in the opposite eye
- No end-stage glaucoma or retinal detachment
Prior to surgery, a detailed history will be taken. This helps assess the corneal condition and determines if the patient is a good candidate for the surgery.
The device is inserted into a corneal graft, which is then sutured into the patient’s cornea as in standard transplantation. If the natural lens is in place, it is also removed. Finally, a soft contact lens is applied to the surface; it must be worn around the clock, every day. This does not cause any discomfort.
Our one-step surgery is simpler and faster than procedures used in other keratoprosthesis models; it generally requires about 1.5 hours to complete. While general anesthesia is recommended, surgery is often performed under local anesthesia with intravenous sedation. Improvements in vision are usually noted the following day or week(s). Although the prosthesis is clear, use of a colored contact lens can perfectly match the iris color of the opposite eye.
Because of possible complications that can result after many surgical procedures, patients with keratoprosthesis require relatively frequent ophthalmologic examinations in the beginning of postoperative care. The patient should be 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 time, examination by the surgeon every three to four months is also recommended.
For long-term postoperative safety, it is recommended that the patient continuously wear the soft contact lens (not felt by patient) and use prophylactic antibiotic drops once or twice daily. 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.
Stability and Safety
The Boston Keratoprosthesis is known for excellent long-term (many years) stability and safety. Its optical system can provide normal vision if the rest of the eye is undamaged.
The surgery is reversible at any time.
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Referring physicians and ophthalmologists trained in Boston Keratoprosthesis surgery may find more information on our Physician Resources webpages.