The Silicone Study (SS) is an NEI-funded, multi-center, randomized surgical trial designed to compare the effectiveness of intraocular silicone oil versus intraocular gas (SF-6 or C3F8) in the treatment of proliferative vitreoretinopathy (PVR) by vitrectomy and associated techniques in the non-vitrectomized eye (Group 1) and the previously vitrectomized eye (Group 2). The primary endpoints are post-operative visual acuity and the anatomical status of the macula at 6, 12, 18, 24, and 36 months post-randomization. During the recruitment period (September, 1985 to December, 1990), 404 patients were randomized to silicone oil or gas; 232 patients to Group 1 and 172 to Group 2. Follow- up observations on vision, macula status (both observational and photographic) and complications have been accumulated on these patients (approximately 10,000 person-months of observation). Only 6% of all patient-visits were missed visits. The primary aim of this competitive renewal is to complete two additional years of follow-up on the 257 eyes in which the macula is attached (regardless of treatment assignment) using the current SS protocol and forms, in order to answer the following questions: 1. Does long-term visual loss occur more or less frequently in eyes from which silicone oil has been removed than in those permanently filled with silicone oil or treated with long-acting gas? 2. Do defined long-term complications occur more or less frequently in eyes from which silicone oil has been removed than in those filled with silicone oil or treated with long-acting gas?
