<prompt> Gas used in retinal tamponade: D. REPEAT 2013SF6 sulfur hexafluorideEthylene oxideNitrous oxideCO2  <response>: Ref: Kan ski Clinical Ophthalmology, 6th edition. Pages 727-728; Modern Ophthalmology, 3rd edition. L.C. Dutta, Pages 1753-1755Explanation:INDICATION FOR TAMPONADES1 To achieve the retinal flattening by replacing the vitreous.2 To drain the subretina fluid.3 To provide the internal tamponade of retinal breaks during the postoperative period.TypesExpanding gases:GasesExpansion at 100Duration of actionConcentration used Sulphur HexachlorideSF62 times10-14 days20-30Perlluorethane C2F63 times32-35 days Perlluiropropane C3F84 times55 -65days12-16Indication: Superior retinal breaks Gas will be floating.Post operative: Patient must maintain a particular head position to prevent pupillary block glaucoma and to give the appropriately directed buoyancy effect.Silicone Oil: Low specific gravity.Acts as tamponade, prevents migration of proliferative cells and biochemical mediator like VEGF within the vitreous cavity and provides hemostasis during surgery.Complication:Emulsification - Inverse hypopyon the emulsified silicone oil is called hyperleon.Cataract.Glaucoma.Perfluorocarbon LiquidsHigh specific gravity - it sinks.Uses: Displaces the subretinal fluid, unfolds the Hup during surgeries. Hence it is also called as Third Hand.E.g. Perfluorobutylamine, perfluoron octane, perfluorodecalen. 