In some patients, corneal transplantation is associated with an extremely guarded prognosis because of a history of multiple graft failures or associated ocular surface disease (eg, chronic bilateral inflammation from Stevens-Johnson syndrome or mucous membrane pemphigoid). These patients may be good candidates for a synthetic keratoprosthesis. Claes Dohlman, a pioneer in the development of the keratoprosthesis, divides these high-risk patients into 2 groups: those with a good blink reflex and adequate tear function and those with significant conjunctival scarring, dry eye, and exposure. In the first group of patients, the Boston keratoprosthesis type I (KPro; Massachusetts Eye and Ear Infirmary, Boston) works well (Fig 15-27). For patients with end-stage dry eye, the Boston KPro type II is an option. Other types of keratoprostheses for these high-risk patients are more popular in Europe and include the TKPro, which uses tibia bone tissue, and the osteo-odonto-keratoprosthesis, which uses dentine and alveolar bone tissue.
Some surgeons have expanded the indications to include the treatment of ocular trauma, advanced quiescent herpetic disease, aniridia, and congenital corneal opacification.
The prognosis for keratoprosthesis implantation has improved dramatically because of innovations in the design of keratoprostheses and improvements in postoperative management. The use of a soft contact lens and long-term prophylactic antibiotics has reduced the incidence of infection and necrosis around the keratoprosthesis. A review of the literature on the Boston keratoprosthesis, the results of which were published in a report by AAO, revealed that a BCSVA of 20/200 or better occurred in 45%–89% of eyes, and a BCSVA of 20/40 or better occurred in 11%–39% of eyes after implantation of the Boston KPro. In a large, multicenter study of 300 eyes followed for 17.1±14.8 months after implantation of the Boston KPro, there was significant improvement in vision, although only 6% of eyes had visual acuity of 20/60 or better. The retention rate with the Boston KPro type I ranged from 65% to 100%. Loss of vision resulted from corneal melts due to exposure keratopathy, endophthalmitis, infectious keratitis, or corneal ulceration. The most common complications following keratoprosthesis implantation were persistent epithelial defects, retroprosthetic membrane formation, stromal necrosis, and elevated IOP, often associated with glaucoma (Table 15-9).
Figure 15-27 Boston keratoprosthesis type I.
(Courtesy of James J. Reidy, MD.)
Table 15-9 Complications of Keratoprosthesis
Chang HY, Luo ZK, Chodosh J, Dohlman CH, Colby KA. Primary implantation of type I Boston keratoprosthesis in nonautoimmune corneal disease. Cornea. 2015;34(3):264–270.
Lee WB, Shtein RM, Kaufman SC, Deng SX, Rosenblatt MI. Boston keratoprosthesis: outcomes and complications: a report by the American Academy of Ophthalmology. Ophthalmology. 2015;122(7):1504–1511.
Part XII, Keratoprosthesis. In: Mannis MJ, Holland EJ, eds. Cornea. Vol 2. 4th ed. Philadelphia: Elsevier; 2017:1635–1667.
Rudnisky CJ, Belin MW, Guo R, Ciolino JB; Boston Type 1 Keratoprosthesis Study Group. Visual acuity outcomes of the Boston keratoprosthesis type 1: multicenter study results. Am J Ophthalmol. 2016;162:89–98.
Sayegh RR, Afshari NA, Chang HP, Lou ZK, Chodosh J. An overview of keratoprosthesis. Focal Points: Clinical Modules for Ophthalmologists. San Francisco: American Academy of Ophthalmology; 2014, module 6.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.