Abstract
Purpose: :
To evaluate the role of silicone-hydrogel (Si-Hy) contact lens oxygen transmissibility (Dk/t) on the corneal endothelial bleb response in eyes of East Asian subjects.
Methods: :
A total of 24 subjects of East Asian origin, attended for three separate sessions for a prospective, single-centre, trial. The following Si-Hy contact lenses were used: ACUVUE ® ADVANCETM with HYDRACLEARTM (Advance, -3D), ACUVUE ® OASYSTM with HYDRACLEARTM Plus (Oasys, -3D) and Focus® NIGHT & DAYTM (Night & Day, -3D). SofLens® 38 (+3D) was used as a positive hydrogel control. A modified Balaam’s crossover design was used to randomize presentation of sessions and contact lenses within sessions. Session one was a comparison between Oasys and SofLens 38 under closed eye conditions, session two was a comparison between Advance and Night & Day with eyes open and session three was a comparison between Oasys and Night & Day worn during eye closure. Corneal endothelial images were captured with the Topcon SP-3000P non-contact Specular Microscope after 20 minutes of wear and 5 and 10 minutes 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 IMAGEnetTM 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% after 20 minutes, 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%. In session 3, Oasys and Night & Day produced mean percentage bleb areas of 1.7% and 2.0%, respectively. The differences between Si-Hy lenses in sessions 2 and 3 were not statistically significant. Recovery from the bleb response was essentially complete in all cases except Soflens 38 within 10 minutes of lens removal.
Conclusions: :
The similarity of bleb responses induced by the Si-Hy 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 physiological conditions.
Keywords: cornea: endothelium • contact lens