[Keratoprostheses: Last Hope for the Most Severe Corneal Diseases]

Corneal blindness affects over 8 million adults and 1.5 million children worldwide, making it one of the top 5 causes of blindness. Depending on the recipient's corneal condition corneal transplantation may not be a viable treatment option. In such seemingly no-alternative situations, keratoprosthesis implantation can be an option in some patients. In terms of numbers, two types of keratoprostheses are currently used: 1. Keratoprostheses with biological haptics made of tooth or tibia bone. 2. The Boston type I-keratoprosthesis. Both types have optics made of PMMA. The most common complication is the formation of an optically disturbing retroprosthetic membrane behind the optic, which can usually be removed with YAG laser. Causes of blindness after keratoprosthesis implantation are glaucoma, endophthalmitis and retinal detachment. The extrusion rate of the Boston type I-keratoprosthesis seems to be higher than after keratoprosthesis implantation with biological haptic. Autoimmunological corneal diseases have increased extrusion rates and higher rates of endophthalmitis when compared to non-autoimmunological diseases. Visual outcomes after keratoprosthesis implantation are potentially very good and usually limited by extracorneal concomitant diseases. Advances in glaucoma diagnostic (OCT, implantation of intraocular pressure sensors), standard glaucoma prophylaxis by medication or surgery, modern retinal surgery and better treatment options in case of extrusion improve the prognosis of keratoprosthesis surgery. Still, the ideal technique for permanent anchoring of artifical optics in biological tissue has yet to be developed.