Silicone oil-associated retinal light exposure under a surgical microscope

Purpose: Based on the hypothesis that silicone oil (SO) with a higher refractive index than water induces unexpected vignetting effects during surgeries, we aimed to investigate the relationship between the volume of SO and light intensity using a surgical microscope. Methods: Using a light-sensitive paper and model eye filled with varying volumes (0%, 50%, 62.5%, 75%, 87.5% and 100%) of SO, the light intensity of intraocular lens (IOL) with various refractive powers (0, 10 and 20 dioptres) illuminated by a surgical microscope was measured. Results: Light exposure density with 1.0% coaxial and oblique light was approximately 22-fold higher than that with 0.1% coaxial and oblique light. Further, it was approximately 34-fold higher in eyes with +20 D IOL than in those with no IOL. The density in eyes with 75% SO was the highest among all groups followed by that with 0% SO. Light exposure densities in the eyes with 75% and 0% SO were significantly higher than those with other volumes of SO. In SO-filled eyes, a microscope set with only an oblique light and a filter successfully reduced light exposure. Conclusion: Silicone oil-related vision loss (SORVL) during SO removal surgeries might be due to increased light exposure on the macular retina caused by the SO-associated vignetting effect. SORVL could be prevented by placing a filter in the microscope during SO removal surgeries.