Sorry Sandy63. That is just too broad of a question. If this concerns you or a friend or family member you need to discuss that with the Eye MD retina surgeon treating the condition.
JCH III MD Eye physician and Surgeon
Silicon oil can remain in an eye indefinitely. However, in most cases it is left in an eye for several months before it is removed. Problems related to longer term use of silicon oil include oil emulsion, cornea decompensation, development of cataract, and problems with elevated intraocular pressure.
Silicon oil has many benefits over other vitreous substitutes though. If you have questions, don't hesitate to ask your surgeon.