A clinical comparison of two gas permeable contact lenses (GPII and PolyconII) with respect to corneal edema

Corneal edema was assessed for two gas permeable lenses (GPII and Polyconii) on five locations across the horizontal meridian. Each of these lenses have received FDA approval and are made of PMMA-Silicone polymer and Cellulose acetate butyrate respectively. Sixteen subjects were randomly selected who showed no contra-indications to contact lens wear and were fitted using standard contact lens fitting criteria with slight apical clearance and no marked peripheral seal-off. These subjects were observed while wearing both Polyconii and GPII, using a contralateral eye study protocol, for a period of 28 days. Pachometry was used to monitor changes in corneal thickness. There was no significant difference in the amount of swelling from baseline for these two lenses across five horizontal corneal locations; as well as, no significant difference using a 98% confidence level when compared one lens to the other. Nonstatistically, a general trend was observed for most all horizontal meridian with both lenses; a decrease in corneal thickness from baseline at day 7, then a marked increase at day 14, some even larger than baseline, and finally, a corneal thinning at day 28 below baseline values