Polydimethylsiloxanes (PDMS), (CH3)3SiO-[Si(CH3)2O]n-Si(CH3)3, known as silicone oil is a tamponade liquid which is very important in vitreoretinal surgery, especially in the treatment of complicated retinal detachment. Here, we investigated the optical properties and structure of silicone oil with high viscosity silicone oil of 5500 cSt and low viscosity silicone oil of 1300 cSt in order to understand the changing of physical properties of silicone oil before and after using in vitreoretinal surgery as a tamponade liquid and analyze the relationship between the tamponade duration and changed in silicone oil properties. From UV-Vis spectroscopy and refractometer measurement, it is found some changes in transmittance and refractive index values in both silicone oil after using as a tamponade liquid. From fourier transform infrared (FT-IR) spectroscopy, some additional of functional groups of N-H and O-H bond are observed at 1634.5 cm-1 and 3435.7 – 3764.5 cm-1, respectively. The changes of optical and structure properties of silicone oil after using as a tamponade liquid are assumed to be responsible in emulsification of silicone oil and affect the transmittance quality at visible light spectrum. However, in this study, there is no linear corelation between tamponade duration and changed in silicone oil properties.