This paper shows how a public eye and research hospital in Turkey initiated Six Sigma principles to reduce the number of complications occurring after penetrating keratoplasty surgeries. Data were collected for nine years. To analyse the complications among 55 patients (59 eyes) underwent penetrative keratoplasty, main tools of Six Sigma's Define-Measure-Analyze-Improve-Control (DMAIC) improvement cycle such as SIPOC table and Failure, Mode and Effect Analysis (FMEA) were implemented. Sources and root causes of eleven types of complications were identified and reported. For a successful penetrating keratoplasty surgery patient's anatomy, suitability of donor cornea, experience of ophthalmic surgeon, sterilization and hygiene, and performance of the equipment were determined to be the "critical-to-quality" factors. The complication with the highest hazard score was found to be the glaucoma. The process sigma level of the process was measured to be 3.1418. The surgical team concluded that all types of post-operative complications should be significantly reduced by taking the necessary preventive measures.