Purpose To report logarithm of the minimal angle of resolution (logMAR) visual outcomes of the Boston keratoprosthesis type 1. Design Prospective cohort study. Methods Preoperative, intraoperative, and postoperative parameters of 300 eyes of 300 patients who underwent implantation of a Boston keratoprosthesis type 1 device between January 2003 and July 2008 by 1 of 19 surgeons at 18 medical centers were collected. Results After an average of 17.1 ± 14.8 months, visual acuity improved significantly (P <.0001) to a mean final value of 0.89 ± 0.64 (20/150). There were also significantly fewer eyes with light perception (6.7%; n = 19; P <.0001), although 3.1% (n = 9) progressed to no light perception. There was no association between age (P =.08), sex (P =.959), operative side (P =.167), or failure (P =.494) and final visual acuity. The median time to achieve 20/200 visual acuity was 1 month (95% confidence interval 1.0-6.0) and it was retained for an average of 47.8 months. Multivariate analysis, controlling for preoperative visual acuity, demonstrated 2 factors associated with final visual outcome: chemical injury was associated with better final vision (P =.007), whereas age-related macular degeneration was associated with poorer vision (P <.0001). Conclusions The Boston keratoprosthesis type 1 is an effective device for rehabilitation in advanced ocular surface disease, resulting in a significant improvement in visual acuity. Eyes achieved a mean value of 20/150 (0.89 ± 0.64 logMAR units) after 6 months and this was relatively stable thereafter. The best visual prognosis is observed in chemical injury eyes, whereas the worst prognosis is in aniridia, although the latter has limited visual potential.
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