Although a refractive surprise due to an error in the sphere is quiet uncommon using excimer technology, its clinical impact may be devastating for the patient and the surgeon. There are several sources of mistakes that may cause a refractive surprise: a human source, laser-related condition, laser suite conditions, and the patient’s response to surgery. Most of the causes that end in a refractive surprise are preventable and must be recognized, understood, and avoided by each refractive surgeon. A well-organized facility and an enthusiastic refractive team must be involved in the prevention of the occurrence of these mistakes, supporting the work of the refractive surgeon. Corneal wound-healing response is of particular relevance for refractive surgical procedures because it is a major determinant of their efficacy and safety. Unfortunately, these conditions cannot be screened preoperatively and therefore cannot be predicted.