Effect of fluid-air exchange on reducing residual silicone oil after silicone oil removal

Our purpose was to determine the effect of fluid-air exchange on the amount of silicone oil (SO) droplets remaining in the vitreous cavity after removal of the main body of the SO. This was a retrospective comparative study of 56 eyes of 56 patients that had undergone vitrectomy with SO tamponade. Fluid-air exchange was performed during surgery in 30 eyes [Air Ex(+) group] and was not done in 26 eyes [Air Ex(-) group]. All of the eyes were examined by ultrasonography, and the images were converted to binarized image. The amount of residual SO droplets/vitreal area in the images was expressed as the, "silicone oil index (SOI)". The correlations between SOI and clinical findings were determined. The SOI was significantly correlated with the axial length (AL, R = 0.444, P = 0.023). The SOI in the Air Ex(+) group was significantly higher (7.4 +/- 2.6%) than in the Air Ex(-) group (4.9 +/- 3.4%; P = 0.004). Multiple linear regression analyses showed that the SOI was independently and significantly correlated with the AL and the Air Ex(+) group (P = 0.003, P = 0.006, respectively). Fluid-air exchange during vitrectomy to remove residual SO is not effective. Our findings indicate that it may increase the amount of residual SO droplets.