Influence of lens wear on equilibrium water content of daily disposable contact lenses

Abstract

Purpose: The aim of this study was to investigate the ability of six daily disposable contact lenses to retain its equilibrium water content after wear. Methods: In this contralateral open trial, 27 subjects (8 males) with mean age of 28.2±7.5 years were randomly fitted with 6 daily disposable contact lenses. The lenses materials used were: Stenfilcon A (Cooper Vision), delefilcon A (Alcon), nelfilcon A (Alcon), narafilcon A (Johnson & Johnson), nesofilcon A (Bausch & Lomb) and omafilcon A (Cooper Vision). Equilibrium water content of 54 contact lenses was measured using a digital refractometer (CLR 12-70, Index Instruments, Cambridge, UK). The assessment was made before and after 11.5±1.0 h of lenses wear. Four measurements per lens were performed and the mean value was considered for the analyses. Results: There was an evident decrease in equilibrium water content for omafilcon A (-6.7%, p=0.002), narafilcon A (-4.4%, p=0.008) and nesofilcon A (-1.7%, p=0.003) after lenses wear. No significant changes were found for stenfilcon A (-0.6%, p=0.950) and nelfilcon A (0%, p=0.860). Distinct results were found for delefilcon A that reported a slight increase in water content over the same period of time (+4.1%, p<0.001). Conclusion: Despite the highlighted differences, the equilibrium water content variation was not considered to be clinically relevant after 11.5±1.0 h of lenses wear. A larger sample is also needed to confirm the results."