Abstract
Abstract: :
Purpose: Silicone oil is a useful tamponading material used in complex vitroretinal surgery. However, the use of silicone oil is a assoicated with emulsification which can lead to vision threatening complications such as silicone keratopathy and secondary glaucoma. We developed an experimental model using an artificial eye chamber and mechanical shaker to assess whether the use of an encircling band and increased level of silicone oil fill would reduce silicone oil emulsification. Methods: Two identical artificial eye chambers were constructed using clear perspex. One model had a circumferential band placed at the sphere's equator that mimicked an encircling band indentation of 1.5mm. One chamber was filled with 90% Silicone Oil 1000 centistrokes (Adato, Bausch and Lomb, UK) and 10% balanced salt solution. The other chamber was filled with 75% of the same Silicone Oil and 25% balanced salt solution. The two eye chambers were then placed on a horizontal rotating shaker, mimicking physiological saccadic eye movements, which spun the chambers at 100Hz for 5 days at 37°C. The experiment was repeated in the banded model with 75% silicone oil–filled and the results compared to that of the banded 90% silicone oil–filled study. All experiments were repeated 5 times. Emulsification was then quantified by dark field microscopy, digital photography and manual counting by a masked observer. The average number of emulsification bubbles was calculated for individual eye chamber. The Mann Whitney non–parametric test was used to detect any statistically significant difference between banded 90% silicone oil fill and the other groups. Results: The mean ±standard deviation (SD) values of silicone emulsification bubbles were as follow: In the 90% silicone oil experiments Banded was 10.9 ±22.2 and Unbanded was 139.1±313.4 (p<0.0001). In the 75% silicone oil experiments Banded was 18.5 ±32, compared to 90% Banded (p=0.039). Conclusions: The emulsification of silicone oil results from surface tension between the silicone oil and aqueous liquids. The results from this study suggested two important factors in the process of emulsification of silicone oil and how this may be reduced: (1)The more complete the silicone oil fill in the eye chamber, the lower the level of silicone oil emulsification. (2)The indentation from the encircling band exerted a stabilizing effect on the silicone oil globule during eye movement resulting in reduced emulsification. We hypothesize that both the increased fill of silicone oil and an encircling band indent lead to reduced emulsification by reducing silicone oil/ aqueous movement and resulting surface tension.
Keywords: retinal detachment • vitreoretinal surgery • vitreous substitutes