Abstract
Purpose: :
The effect of soft contact lens (SCL) wear on the eye’s optical quality is a significant issue because optical quality affects vision under challenging visual conditions such as in low contrast or in dim illumination. The purpose of this study was to compare the visual performance in wearers of daily wear hydrogel contact lenses and silicone hydrogel (SiHy) lenses.
Methods: :
Visual acuity (VA) was measured in conventional hydrogel lens wearers and silicone hydrogel lens wearers, after at least 4 hours of contact lens wear, at two luminance levels using back-illuminated LogMAR charts of 100%, 25% and 5% contrast. VA was first measured with contact lenses on the eye, using a 1.2 neutral density filter (12.62 cd/m2) and then without a filter (200 cd/m2). The same measurements were then repeated 20 minutes after contact lens removal, using the best subjective spectacle correction.
Results: :
With SCLs on the eye, the SiHy lenses provided worse acuity than the spectacle correction at the higher light level for the 5% and 100% contrast charts (p<0.05). Conventional hydrogel wearers also had lower acuity with SCLs in place compared to spectacles for the 100% contrast chart at the higher light level, but this effect was not significant. For all other conditions, both contact lens types provided nearly equivalent visual performance compared to spectacles. Comparing performance between the two groups of lens wearers, visual acuity was not significantly different with lenses on the eye or with spectacles.
Conclusions: :
Silicone-hydrogel SCLs provided equivalent visual performance to conventional hydrogel lenses while on the eye. However, at the higher light level, silicone-hydrogel SCLs provided lower visual performance compared to spectacle wear.
Keywords: visual acuity • contact lens • refraction