PURPOSE: To identify predisposed eyes, risk factors, and protective measures and to evaluate methods of treatment for fixed dilated pupil after penetrating keratoplasty (PKP) for macular corneal dystrophy (MCD) and keratoconus. DESIGN: Retrospective observational case series. METHODS: A retrospective review was conducted of the charts of 195 patients who had PKP for MCD and of 1800 patients who had PKP for keratoconus at the King Khaled Eye Specialist Hospital in Riyadh, Saudi Arabia. The review included an evaluation of the preoperative and intraoperative data and the postoperative course. In addition, clinical examinations at the last visit and photographs of the cornea, pupil, iris, and lens were analyzed. RESULTS: Twenty-one eyes of 18 patients had fixed dilated pupil after PKP; 15 eyes of 12 patients had MCD, and six eyes of six patients had keratoconus. A rise in intraocular pressure (IOP) during the procedure was seen in five patients (23.8% ). Fixed dilated pupil was documented on the first and second postoperative days and the second postoperative week in 17 (80.9% ), one (4.8% ), and three (14.3% ) eyes, respectively. Six eyes (28.6% ) of six patients had severe eye inflammation. Only one eye (4.8% ) regained partial reactivity of the pupil on followup visits. Seven eyes (33.3% ) experienced lens changes; nine eyes (42.8% ) had elevated IOP on the first postoperative day, and none of the eyes had chronic glaucoma. CONCLUSION: Inflammatory andmultifactorial pathologic condition can cause fixed pupil after PKP. Atropine use, keratoconus, and high IOP are not constant findings in this syndrome. Awareness of the risk factors of fixed dilated pupil will help prevent against its occurrence. PURPOSE: To identify predisposed eyes, risk factors, and protective measures and to evaluate methods of treatment for fixed dilated pupil after penetrating keratoplasty (PKP) for macular corneal dystrophy (MCD) and keratoconus. DESIGN: Retrospective observational case series. METHODS: A retrospective review was conducted of the charts of 195 patients who had PKP for MCD and of 1800 patients who had PKP for keratoconus at the King Khaled Eye Specialist Hospital in Riyadh, Saudi Arabia. The review included an evaluation of the preoperative and intraoperative data and the postoperative course: In addition, clinical examinations at the last visit and photographs of the cornea, pupil, iris, and lens were analyzed. RESULTS: Twenty-one eyes of 18 patients had fixed dilated pupil after PKP; 15 eyes of 12 patients had MCD, and six eyes of six patients had keratoconus. A rise in intraocular pressure (IOP) during the procedure was seen in five patients (23.8%). Fixed dilated pupil was documented on the first and second postoperative days and the second postoperative week in 17 (80.9%), one (4.8%), and three (14.3%) eyes, respectively. Six eyes (28.6%) of six patients had severe eye inflammation. Only Seven eyes (33.3%) experienced lens changes; nine eyes (42.8%) had elevated IOP on the first postoperative day, and none of the eyes had chronic glaucoma. one eye (4.8%) regained partial reactivity of the pupil on followup visits. CONCLUSION: Inflammatory and multifactorial pathologic conditions can cause fixed pupil after PKP. Atropine use, keratoconus, and high IOP are not constant findings in this syndrome. Awareness of the risk factors of fixed dilated pupil will help prevent its occurrence.