Change in Myopia Over Three Years Among Wearers of Continuous Wear Silicone Hydrogel Lenses and Daily Wear Hydrogel Contact Lenses

Abstract

Purpose: : Earlier studies with continuous wear (CW) of silicone hydrogel lenses showed that users had a lower rate of myopic progression compared to subjects who wore hydrogel lenses on a 6 night extended wear (EW) schedule. The purpose of this study was to compare the long term results for lotrafilcon A CW lens wear compared to hydrogel daily wear (DW).

Methods: : Subjects were enrolled in a 3–year non–randomized trial in which investigators could choose to place a subject in CW with lotrafilcon A lenses or 2 weekly replacement DW with hydrogel lenses. An age matched subset was randomly selected from among the CW and DW subjects who completed the study. Baseline and 3 year spectacle subjective refractive errors were compared to test whether there was a significant difference in the change in refractive error over time.

Results: : 36 CW subjects aged 27.9 + 12.4 years had baseline refractive error of –3.59 + 1.99 DS. The 36 DW subjects were aged 27.9 + 12.5 years and had baseline refractive error of –2.10 + 1.78 DS (p<0.01). CW subjects increased in myopia by 0.03 DS while DW subjects increased in myopia by 0.40 DS (p=0.007). There was no significant change in corneal curvature by keratometry for the CW subjects and there was slight but significant increase in the steepness of the steep K reading for the DW subjects (p<0.05). The proportion of CW subjects with presenting VA of 20/20 or better remained relatively stable, varying from 80 to 86% during the study, while the proportion for DW subjects ranged from 63% to 78% at follow–up visits through 36 months in the study.

Conclusions: : Subjects with higher refractive errors were placed in the CW group by investigators in this study. Notwithstanding, there was a larger amount of myopic progression among the age matched users of DW hydrogel lens wearers that caused a portion of them to present with under–correction during scheduled annual visits. CW silicone hydrogel lenses maintained a more stable refractive error over the 3 year observation period in this study.

Keywords: accessory optic system/pretectum