After approval by the institutional review boards of Mayo Clinic and Olmsted Medical Center, the resources of the REP were used to identify all potential incident cases of HSV eye disease in Olmsted County, Minnesota, between January 1, 1976, and December 31, 2007. Medical records were retrieved for all patients with diagnostic codes related to HSV eye disease. Assigned diagnostic codes were based on Mayo Clinic modifications of the International Classification of Diseases, Ninth Revision, Clinical Modification, and included codes 054.40 (herpes simplex, ophthalmic), 054.41 (blepharitis, herpes simplex), 054.42 (dendritic keratitis, herpes simplex), 054.43 (herpes keratitis, simplex), 054.44 (herpes iritis, simplex), and 054.79 (ophthalmic herpes simplex, not elsewhere classified). Cases coded as having nonophthalmic herpes simplex and herpes zoster were not retrieved. Residency status was confirmed using methods developed by the REP. The coauthors reviewed all medical records to identify all cases of HSV eye disease during the study period. Incident cases included only patients whose initial episode occurred during the study period. Patients who reported initial episodes prior to establishing residency in Olmsted County were excluded from the study. The complete medical records for all incident cases were then abstracted to include information on demographics, diagnoses, medications, therapeutic interventions, recurrences, and adverse outcomes. Data were collected for every clinic visit during the study period for all incident cases. If not specifically recorded in the medical record for a given visit, the date on which medication was started or stopped was estimated to be at the midpoint between 2 visits. Cases in which the clinical findings and/or laboratory evidence were inadequate for or inconsistent with a diagnosis of ocular HSV were excluded after review by the senior clinician-investigator (Dr Baratz). Events related to HSV were defined as ocular disease, such as blepharitis, conjunctivitis, keratitis, uveitis, and/or posterior segment disease, deemed by the examining clinician to be due to HSV greater than 1 month after quiescence, as described in Table 1. Adverse outcomes were defined as irreversible loss of vision to 20/200 or worse, corneal perforation, or any surgical intervention necessitated by HSV-related complications (ie, trabeculectomy, keratoplasty, conjunctival flap, and permanent tarsorrhaphy). Cataract, cataract surgery, or glaucoma surgery in a patient diagnosed with glaucoma prior to the diagnosis of HSV was not considered an adverse outcome.