Short-term corneal endothelial response to wear of silicone-hydrogel contact lenses in East Asian eyes

OBJECTIVE: To evaluate corneal endothelial bleb response to wear of silicone-hydrogel contact lenses in eyes of East Asian subjects. METHODS: A total of 24 subjects of East Asian origin, attended 3 separate sessions for a prospective, single-centre, trial. The following contact lenses were used: ACUVUE ADVANCE with HYDRACLEAR (ADVANCE, -3 dioptres), ACUVUE OASYS with HYDRACLEAR Plus (OASYS, -3 dioptres), Focus NIGHT & DAY (NIGHT & DAY, -3 dioptres) and SofLens 38 (+3 dioptres). A modified Balaam's crossover design was used to randomize presentation of sessions and contact lenses within sessions. Session 1 was a comparison between OASYS and SofLens 38 under closed eye conditions, session 2 was a comparison between ADVANCE and NIGHT & DAY under open eye conditions, and session 3 was a comparison between OASYS and NIGHT & DAY worn under closed eye conditions. Corneal endothelial images were captured with the Topcon SP-3000P noncontact Specular Microscope before lens wear, after 20 mins of wear with lenses on and 5 and 10 mins later after lens removal. Blebs were manually identified on these digital images by a masked observer. The area of blebs and total area under consideration were derived using ImageNet software and used to calculate percentage area of blebs. A boundary of equivalence of 1% was used as a clinically significant bleb area difference, and two-sided 95% confidence intervals were utilized to evaluate differences between lenses within each session. RESULTS: In session 1, SofLens 38 produced a mean percentage area of blebs of 8.0% under closed eye conditions, which was significantly different to that produced by OASYS (1.6%). In session 2, both Advance and Night & Day produced a mean percentage bleb area of 0.4% under open eye conditions. In session 3, OASYS and NIGHT & DAY produced statistically similar mean percentage bleb areas of 1.7% and 2.0%, respectively. CONCLUSIONS: The similarity of bleb responses induced by the silicone-hydrogel lenses under the tested wearing conditions is consistent with the proposition that increases in Dk/t above a certain level will produce minimal change in corneal physiologic conditions compared with that when no lens is worn.