Abstract: Silicone oil (SO) is a relatively safe intravitreal tamponade and widely used in vitreoretinal surgery. Severe, irreversible and unexplained visual loss of a few patients were noticed during SO tamponade or after SO removal. However, no remarkable signs were found in examinations. Some retinal structural changes have been noted in these patients recently, such as thinning of inner retina and microcystic macular edema in inner nuclear layer. Several hypotheses of pathogenesis had been put forward, such as failure of potassium siphoning by Müller cells, retinal light exposure, higher intraocular pressure during SO tamponade, longer SO tamponade duration and retinal ischemia during surgery. Even though, the pathogenesis of this issue remains elusive. Further study will help to understand the exact mechanisms.