No abstract

Porous polytetrafluoroethylene and polyurethane skirt materials, as well as copolymers of poly (2-hydroxyethyl methacrylate), have shown promise in approaching the goal of a "biointegratable" keratoprosthesis. A novel fixation method that uses scleral haptics also has been introduced to increase stability. An all silicone device that can be sewn into position has been used successfully, temporarily, during vitreoretinal procedures. The prognosis of keratoprosthesis (KPro) procedures depends on the preoperative diagnosis: graft failure-noncicatrizing disease>ocular cicatricial pemphigoid>chemical burns>Stevens-Johnson syndrome. The likelihood of endophthalmitis after KPro surgery follows this scheme. Causative organisms tend to be gram-positive. Modified vitreoretinal techniques also have been developed, allowing successful treatment of posterior segment complications. The science of keratoprosthesis is advancing more rapidly than in previous years. However, use of KPro to address complicated corneal blindness worldwide remains limited. The authors conducted an English language literature review from January 1, 2000 to April 1, 2001 and describe advances of note in the field of keratoprosthesis design, materials, and medical and surgical management.

The Boston KPro design with a back plate containing holes protects the overlying corneal tissue from necrosis and melts. This improved situation is likely due to increased aqueous access and better nutrition to the corneal graft cells. In addition, this study confirms earlier work regarding the particular corneal fragility of patients with autoimmune diseases.

The Boston keratoprosthesis (KPro) is one of several types of artificial cornea manufactured worldwide that are being implanted in increasing numbers in patients with severe corneal diseases and graft failures. The prognosis for long-term success varies greatly between diseases, with autoimmune conditions, such as ocular cicatricial pemphigoid and Stevens-Johnson syndrome, and severe chemical burns remaining difficult. In the potentially much larger cohort with little preoperative inflammation, retention is excellent, complications are manageable and outcome is usually very good. Early implantation in congenital corneal opacities to offset amblyopia shows promise. The Boston KPro uses a 'collar button' design of polymethyl methacrylate that is sturdy and easily machined and polished, giving excellent vision if the remainder of the eye is healthy. This is implanted into a carrier corneal graft or into the patient's own cornea. Holes in the back plate allow nutrition from the aqueous humor to reach the graft and long-term use of around-theclock soft contact lenses protects the ocular surface from excessive dehydration. In nonautoimmune diseases, these measures have virtually eliminated necrosis and melt of the corneal tissue holding the device. Postoperative prophylactic antibiotics can now fully protect eyes from infection.