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.