Heavy silicone oil versus standard silicone oil in as vitreous tamponade in inferior PVR (HSO Study): interim analysis.

The Heavy Silicone Oil versus Standard Silicone Oil Study (HSO study) is designed to answer the question whether a heavier-than-water tamponade improves the prognosis of eyes with proliferative vitreoretinopathy (PVR) of the lower retina. The HSO Study is a multicentre, randomized, prospective, controlled clinical trial stratified by surgeon comparing two endotamponades within a two-arm parallel-group design. Patients with inferiorly and posteriorly located PVR grade C-A6 were randomized to either HSO or standard silicone oil as a tamponading agent. The main end-point criteria are complete retinal attachment at 12 months and change in visual acuity (VA) 12 months postoperatively compared to the preoperative VA. Forty-six patients treated with HSO were compared to 47 patients treated with standard silicone oil. There was no difference among the groups regarding baseline data. Three patients in the HSO and five patients in the standard silicone oil group fulfilled intraoperative exclusion criteria. There was no significant difference between both groups regarding anatomical success. Neither noninferiority nor superiority was shown with regard to final acuity. The HSO Study is the first randomized prospective clinical trial to compare heavy and standard silicone oil in patients with PVR of the lower retina. The intermediate results failed to demonstrate superiority of a heavy tamponade.