Graft survival and risk factors of penetrating keratoplasty for microbial keratitis

Purpose: To evaluate graft survival rates and prognostic factors in relation to penetrating keratoplasty for microbial keratitis. Methods: The records of 95 patients treated with penetrating keratoplasty for microbial keratitis during a twenty-year period were reviewed. Data were analysed by construction of survival curves using the Kaplan-Meier non parametric method. Results: The overall survival of a clear cornea was 72% after one year, 71% after two years and 52% after five years. A significantly lower survival rate (p<0.05) was found in the presence of preoperative local risk factors such as wear of contact lenses and trauma and in inflamed eyes. In contrast, systemic diseases like diabetes, cancer or rheumatoid arthritis did not affect survival and neither did recipient age nor the degree of vascularization of the eye. Male donor buttons showed superior survival compared to female ones (p<0.05), while females seemed to constitute the best recipients. Recurrence rates of microbial keratitis postoperatively were 11%, 16% and 24% after one, two and five years, respectively. Corresponding graft rejection rates were 9%, 15% and 27%. Conclusions: Patients suffering from microbial keratitis have a relatively high risk of graft failure. To improve the prognosis care should be taken to minimize local risk factors. Surgery should whenever possible be performed on quiet eyes. The unexpected finding of a better prognosis for male donor buttons might suggest the preferred use of male donors in patients suffering from microbial keratitis, but the observation needs further documentation.