Silicone Oil Emulsion Grading Consensus A Step Closer to Objective Assessments

A silicone oil emulsion grading system “has the potential to improve our understanding of the role and clinical relevance of [silicone oil] emulsion allowing comparisons between different studies,” according to a report published in Retina. The grading protocol is the first rubric to objectively grade emulsified silicone oil (SiO) droplets.

Silicone oil emulsion is a common but significant complication of SiO tamponade, ofter used in conjunction with surgical treatment of vitreoretinal disease, such as advanced retinal detachment. The InTraocular EMulsion of Silicone oil (ITEMS) silicone oil emulsion grading rubric was developed by a group led by 7 experts who conducted a literature review and created a 9-point questionnaire about their grading proposals, which was circulated among fellow physicians. The team then evaluated and discussed survey results for clinical applicability.

The group identified a multi-tiered silicone oil emulsion grading approach to detecting SiO microbubbles and large SiO bubbles. These include:

• Slit lamp biomicroscopy of the anterior chamber (AC) to count emulsified microbubbles smaller than 200 µm, and quantification of bubbles larger than 200 µm.
• Gonioscopy to grade the number of bubbles in the iridocorneal angle.
• A dilated fundus exam or ultrawide-field fundus photography to detect factors such as microbubbles on the retinal surface, bubbles larger than 125 µm, subretinal bubbles, and floating microbubbles after removal of SiO.
• Macular optical coherence tomography (OCT) to check for SiO-related hyperreflective (HR) dots and intraretinal or epiretinal location, and to count HR dots in or near the optic disc.

Prior silicone oil emulsion studies have found emulsified droplets in tissues including ciliary body and trabecular meshwork. Further, analyses show that microbubbles can be phagocytosed by cells such as macrophages, possibly leading to inflammation — which could prompt further emulsification. Toxic effects of particular SiO viscosities have been shown in cultivated corneal endothelial cells.

“The availability of an easy and consistent method for quantifying SiO emulsion would provide an objective method of comparing SiO of differing purities, viscosities and compositions,” according to the researchers.

A limitation of the proposed silicone oil emulsion grading rubric is that it needs to be validated via a prospective design to assess relationships between emulsion grade and clinical signs, confirming effectiveness in a real-world setting.