Several steps can be taken intraoperatively to prevent oil prolapse into the anterior chamber. Silicone oil poses additional challenges in the setting of an aphakic eye, as oil migration to the anterior chamber can result in glaucoma and corneal decompensation. Special attention to the oil meniscus, the infusion line, and the chimney will help prevent overfill. Inadvertent oil underfilling can be avoided by gradually decreasing air infusion until it is at zero and moving the chimney to different ports to drain off trapped pockets of air. On the other hand, oil overfill can lead to increased IOP, glaucoma, corneal decompensation, and pain. When there is oil underfill, the inferior retina is exposed and prone to the development of PVR and/or recurrent detachments due to insufficient tamponade. 6 Bimanual modes (simultaneous active infusion and extraction) are also available on some vitrectomy units, allowing a regular soft-tipped cannula to be used.Įnsuring adequate silicone oil fill intraoperatively is imperative to achieving sufficient intraocular tamponade. It may be achieved by performing active infusion of silicone oil via a viscous fluid cannula together with passive efflux of the PFO via a soft-tipped backflush needle held at the base of the PFO. This technique requires practice and patience, but is effective in minimizing retinal slippage. Direct PFO-oil exchange requires use of chandelier illumination unless an assistant is present. Direct PFO-oil exchange is useful when there is a risk of retinal slippage, especially in cases of giant retinal tears. Silicone oil may be instilled following a fluid-air exchange or by direct perfluorocarbon (PFO)–silicone oil exchange. Despite its higher rate of emulsification, some surgeons prefer using lower viscosity 1,000 cs silicone oil for its efficiency and ease of instillation and removal, and because it gives surgeons better ability to assess fill in real time by direct observation of silicone oil reflux into the infusion line or chimney.
With the use of small-gauge cannulas during vitrectomy surgery, injection and removal of the higher viscosity 5,000 cs silicone oil becomes more difficult. 4 However, higher viscosity silicone oils (5,000 cs) are more resistant to emulsification over time.
5 A similar review of 82 eyes found no significant differences between the two groups with respect to outcomes or complication rates at 1 year. In a review of 325 eyes with complex retinal detachment, no differences were observed in anatomic or visual outcomes between 1,000 cs and 5,000 cs oil. 4 Heavy silicone oil is denser than water, but these products, such as Densiron 68 and Densiron Xtra (Fluron) and Oxane HD (Bausch + Lomb), are not currently available in the United States.īoth 1,000 cs and 5,000 cs oil have similar surface tensions (21.2 mN/m and 21.3 mN/m, respectively) but differ in molecular weights (37 kDa and 65 kDa, respectively) and viscosities. Silicone oil is available in 1,000 cs and 5,000 cs forms. Features of silicone oil that make it a useful tamponade agent include surface tension and viscosity. Silicone oil is a manmade synthetic substance composed of repeating units of siloxane (Si-O). Optomap (Optos) widefield fundus photo and OCT images of silicone oil tamponade for an inferior retinal detachment with associated PVR, preoperatively (A) and postoperatively (B).
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