Vitreous Substitutes

Vitreous substitutes are important tools in vitreoretinal surgery. A proper understanding of their physical properties is paramount for achieving successful surgery. These substitutes replace the vitreous humor to provide tamponade to retinal breaks and reduce fluid turbulence in cases of retinal detachments. The main two types of vitreous substitutes are gases and liquids. Gases have high surface tension and buoyancy which make them ideal for sealing the retinal breaks and exerting an upward pressure to flatten the retina, respectively. These have a low solubility in water taking longer to dissolve and thus provide a longer-lasting tamponade effect. However, they temporarily affect vision and expand in cases of air travel. Liquid vitreous substitutes are less commonly used than gases. The two main liquid substitutes are silicone oil and perfluorocarbon liquid. The former provides longer-lasting retinal tamponade while maintaining reasonable vision in the eye which makes it suitable for complex retinal detachment with proliferative vitreoretinopathy. However, silicone oil is more inflammatory and has inferior tamponade properties compared to gases, thus not preferred for primary surgery. Perfluorocarbon liquid has a high specific gravity and is easy to inject which makes it useful to uncurl the retinal tear edge in giant retinal tears detachment and to stabilize the retina during proliferative vitreoretinopathy surgery. This chapter outlines the physical properties, indications, different techniques of exchange as well as the limitations of the different types of vitreous substitutes.