Abstract
Purpose:
Contamination reduces the longevity of contact lenses. Although lipids contaminate contact lenses, it is not known if this is preferentially by oxidised lipids. Such knowledge can be useful in developing cleaning solutions.
Methods:
A Fenton reaction was optimized and used to prepare oxidized oleic acid and linolenic acid. The degree of oxidation was quantified by measuring peroxides, malonyldialdehyde reactive species and build-up of polymerized aldehydes. Based on these measurements, 14C fatty acids were oxidised to different degrees. PureVision and Acuvue contact lenses were loaded with these at 35°C and lipid binding was determined by measuring the ratio of bound to unbound radioactivity.
Results:
The degree of oxidation using the Fenton reaction depended on the amount of desaturation. With time, only peroxides were formed from oleic acid whereas linolenic acid was eventually broken down completely. It was determined that 20h incubation with 50µg/mL of lipids gave optimal binding. Acuvue lenses bound ~50% more non-oxidised lipids than PureVision lenses. There was no increase in binding of oxidised lipids compared with non-oxidised lipids in Acuvue lenses. There was an increase of ~50% in binding of mildly oxidised lipids in PureVision lenses. If the lipids were strongly oxidised then they bound less than non-oxidised lipids in both contact lens types.
Conclusions:
There are differences in the ability of different contact lenses to bind oxidised lipids. It appears that mildly oxidised lipids, such as might occur in vivo can bind more strongly to some types of contact lenses than others. This experimental procedure provides a platform for testing the ability of multi-purpose cleaning solutions to remove oxidised lipids.
Keywords: 583 lipids •
477 contact lens •
634 oxidation/oxidative or free radical damage