Emulsification Complexity of Silicone Oil in Retinal Surgery: In Vitro Insights into Phase Behavior

Silicone oil (SO) is widely used as an intraocular tamponade in retinal detachment surgery, but its postoperative emulsification is associated with several acute complications. This study investigates the physicochemical and interfacial mechanisms behind SO emulsification in vitro with a focus on biomolecular interactions at the oil-water interface. Using model aqueous humor containing albumin and γ-globulins, we observed the formation of both oil-in-water and water-in-oil emulsions depending on water/oil ratios. At a 5:5 water/oil ratio, oil droplets in the aqueous phase ranged 2.6-28.1 μm and aqueous droplets in oil 2.8-118.3 μm. At 1:9, only water-in-oil emulsions were formed (5-231.8 μm), and at 9:1, only oil-in-water emulsions occurred (≤5 μm). Moreover, protein-rich conditions significantly increased the emulsion stability and altered the interfacial rheology. Interfacial viscoelasticity measurements with SO 971 mPa·s indicated that proteins enhanced elasticity and interfacial structuring. Interestingly, the interface between model aqueous humor and SO 4990 mPa·s showed more dissipative behavior, despite this interface being a little more rigid in terms of complex modulus than SO 971 mPa·s. Inorganic salts or elevated temperatures had minor or negligible influence, while mechanical agitation was essential for emulsion formation. The formation of stable, small oil-in-water droplets highlights a potential pathway for their migration into the anterior chamber and through the trabecular meshwork, possibly contributing to chronic inflammatory and pressure-related complications. These results offer new insights into the interfacial behavior of SO in contact with biologically relevant fluids and underline the importance of understanding protein-mediated emulsification in the context of intraocular biomaterials.