Change in the geometry of positive- and negative-powered soft contact lenses during wear

Abstract

Contact lens wear causes mutual interactions between the ocular surface and the lens, which may affect comfort as well as vision. The aim of this study was to examine deformations in modern positive- and negative-powered silicone hydrogel soft contact lenses (SiH SCLs) after 7 days of continuous wear. This pre-post interventional study included 64 eyes: 42 eyes with myopia of -3.00 D and 22 eyes with hyperopia of +3.00 D. All patients underwent general ophthalmic examination, corneal topography/tomography, total corneal and epithelial thickness mapping, and specular microscopy before and after the wearing period. SiH SCLs made of senofilcon A were worn continuously for 7 days on all eligible eyes. The geometry of the new and used lenses was measured 3 to 6 minutes after removal in two perpendicular planes using a custom-made swept source optical coherence tomography (SS-OCT) system for in vitro measurements. The anterior and posterior radii of curvature decreased in -3.00 D lenses in two perpendicular planes. This effect correlated significantly with average keratometry of the cornea. Sagittal lens height was lower in +3.00 D lens after wear, which correlated moderately with the corneal sagittal height. A significant decrease in central corneal epithelial thickness was observed after wearing +3.0 D lenses. In conclusion, SiH SCLs made of senofilcon A undergo minor deformations after 7-day continuous wear. Geometry modifications are different for -3.00 D and +3.00 D lenses, and they imitate the shape of the anterior eye surface. These geometric changes are accompanied by a decrease in the central thickness of corneal epithelium after +3.00 D lens wear.

Shape of the anterior surface of the cornea after extended wear of silicone hydrogel soft contact lenses

“…This may result in variable fitting characteristics and cornea‐lens geometry, and may influence the changes in shape of the anterior surface. On the other hand, there is evidence that lenses made from senofilcon A undergo deformation during continuous wear to imitate the shape of the anterior eye surface 35 . Stopping SCL wear for seven days before the initial examination may not have been long enough for some eyes, but it was difficult to persuade patients to cease wearing contact lenses for any longer, which would have increased the risk of non‐compliance.…”

“…On the other hand, there is evidence that lenses made from senofilcon A undergo deformation during continuous wear to imitate the shape of the anterior eye surface. 35 Stopping SCL wear for seven days before the initial examination may not have been long enough for some eyes, but it was difficult to persuade patients to cease wearing contact lenses for any longer, which would have increased the risk of non-compliance. While we assessed corneal parameters before applying and immediately after removing the SCLs, we did not follow the subjects for a longer period to verify recovery of the cornea back to the initial state as this has previously been reported.…”

Advanced morphological analysis of siloxane‐hydrogel contact lenses

“…Recently, wide research has been made to examine the bacterial adhesion to unworn/worn silicone‐hydrogel CLs and the influence of cholesterol deposition on bacterial adhesion to CLs (Babaei et al, 2011; Lee, Lee, Park, & Yu, 2016; Santos et al, 2008; Silva, Fernandes, Nunes, Colaço, & Serro, 2015; Vijay et al, 2012). The functional and wear performances, as well as the hydrogen peroxide mechanosynthesis in siloxane‐hydrogel CLs, were reported in several studies (Bettuelli et al, 2013; Kaluzny et al, 2020; Tavazzi et al, 2014, 2015). Mechanical complications, the improvement of the surface wettability, and changes in ultraviolet transmittance in silicone‐hydrogel CLs were reported in a high number of studies (Lin, Cho, Yeh, & Yang, 2015; Lin & Yeh, 2013; Osuagwu, Ogbuehi, & Almubrad, 2014).…”