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Charles W Scales, Shivkumar Mahadevan, Leilani Sonoda, Mark Lada, Patricia Martin, Donald Riederer, Zohra Fadli; Antioxidant Protection of a Model Tear-Film Component in Soft Contact Lenses. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1769. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The tear-film contains naturally occurring anti-oxidants essential to preserving beneficial components, i.e. lipids and proteins, and maintaining ocular homeostasis. Soft contact lens (CL) materials interact with the tear-film (TF) in different ways, with some taking up large amounts of protein/lipids with minimal to no negative clinical impact. This uptake may be beneficial, as long as the components do not oxidize and degrade during wear. Herein, the benefits of using an antioxidant, i.e. a UV-blocking, phenolic benzotriazole known as Norbloc (NB), in a CL to curtail degradation of a TF component, namely, cholesterol (CH), is demonstrated.
Two experimental silicone hydrogel lens formulations were prepared with and without NB, i.e. (L1) and (L2), respectively. Both were subjected to incubation with CH followed by exposure to oxidative conditions with prescribed doses of hydrogen peroxide (H2O2) (0, 3, and 10 % in PBS), UV exposure (24 hours, at 3 mW/cm2), and combinations thereof. The extent of lipid oxidation within L1 and L2 after each exposure condition was determined via high performance liquid chromatography with mass spectrometry (HPLC-MS) analysis of lens extracts. The appearance of two oxidative degradants of CH, namely, 5α,6α-Epoxycholestan-3β-ol (αCHEI) and 5β,6β-Epoxycholestan-3β-ol (βCHEI), was used to assess the extent of lipid oxidation.
Generally, higher levels of CH epoxides (i.e. α- and β-CHEI) were observed with L2 lenses after exposure to H2O2 and UV compared to L1 lenses. Following exposure to 10 % H2O2 and UV for 24 hrs. at 3 mW/cm2, L2 lenses showed statistically higher amounts of CH degradation to αCHEI (10.1 % ± 1.57) compared to L1 lenses (7.3 % ± 1.94, p=0.020). Under identical conditions, the L2 lenses also showed a statistically higher amount of CH degradation to βCHEI (7.3 % ± 1.15) compared to L1 lenses (3.8 % ± 0.99 p=0.001).
The use of an antioxidant in CLs imparts a protective effect onto adsorbed/absorbed TF components such as CH, i.e. lipid degradation is lower in a CL that contains NB, compared to one that does not. These data support the hypothesis that use of an antioxidant in a CL may help maintain TF components in their native state in vivo, which may positively impact clinical performance.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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