This study evaluated the effect of Benzalkonium Chloride and Chlorhexidine on deposit formation with Paraperm EW and Ocusil RGP lenses. In a double blind study, seventeen first time RGP patients were fit with one Paraperm EW lens, which has a negative surface charge, and one Ocusil lens, which has a neutral surface charge. The lenses were measured for transmissibility prior to dispensing. Half of the patients used solutions preserved with BAK. The other half used solutions preserved with CHG. After two months the lenses were measured for transmissibility. The patients were then dispensed a new pair of lenses so that each lens material was worn on alternate eyes. They were also given the alternate lens care solutions. At the end of two months the lenses were measured for transmissibility. A comparison was made between the two lens care solutions and between the two lens materials. No significant difference was found in light transmissibility between the two lens care solutions or between the two lens materials. This implies that there was no difference in deposit formation between the two lens care solutions or between the two lens materials. Therefore, while the electrostatic binding theory of deposit formation may be correct, deposit formation does not reach a level which is clinically significant.
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