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H.I. Lorentz, M. Senchyna, L. Jones; Optimized Procedure for the Extraction of Lipid Deposits from Silicone–Hydrogel Contact Lenses . Invest. Ophthalmol. Vis. Sci. 2004;45(13):1537.
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Purpose:The purpose of this study was to optimize an efficient method to extract lipid deposits found on both balafilcon (Purevision (PV), Bausch&Lomb) and lotrafilcon (Focus Night&Day (FND), CIBA) contact lens materials. Methods: 24 individual PV and FND lenses were doped with a lipid doping solution (LDS) containing triolein, cholesterol, oleic acid, oleic acid methyl ester and cholesteryl oleate. For each lens type, 12 lenses were doped for 48 hours and 12 for 96 hours, all at 37 oC with constant shaking. Following doping, three lenses of each type were treated with one of four extraction solutions for 3 hours at 37 oC: (a) 50% methanol; (b) 75% methanol; (c) 50% methanol with a 1:1 chloroform:methanol wash and (d) 2:1 chloroform:methanol. The fourth extraction method also contained a 24 hour incubation at room temperature, before being heated for three hours at 37 oC. All lenses under went a double extraction to ensure the complete removal of lipid deposits. Both extracts were condensed using lyophilization to dryness and then resuspended in 20µL of 2:1 chloroform:methanol, applied to high performance thin layer chromatography (TLC) plates (Whatman) and developed using four successive solvent systems. Following plate development, TLC plates were charred using 50% sulphuric acid and baked at 115oC for 1 hour. Resulting bands were imaged and quantified under white light on a Syngene Gene Genius Gel Documentation SystemTM and associated software. Results: Comparison of the four extraction procedures demonstrates that 2:1 chloroform:methanol is significantly more efficient in the extraction of lipids from both PV and FND lens materials compared to the other three methods (F(3,32)=3.202; p =0.036). In addition, we found that PV lenses deposited a significantly greater quantity of the five lipids we used in our doping procedure compared to FND lenses (F(1,32)=11.273; p=0.002). No significant difference was found in the amount of total lipid deposited between the two doping periods employed in this study. Conclusions: We have optimized a method based on a solution containing 2:1 chloroform:methanol that is capable of removing >90% of deposited lipid from both PV and FND contact lens materials. Using this method, we have demonstrated that PV lenses deposit significantly more lipid compared to FND lenses.
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