BACKGROUND: In optical systems, it is usual to compensate for longitudinal spherical aberration. In order to increase image quality, lens surfaces can be made aspheric to bring all object light rays into focus at the image plane. Theoretically, soft contact lenses with high power and spherical surfaces show significant amounts of spherical aberration. The use of spherical aberration-free soft contact lenses could therefore improve retinal image quality in the case of high ametropia. However, because of ocular aberration, accommodation effects, pupil dynamics, contact lens flexure, and positioning, the computation of the spherical aberration induced when a contact lens is placed on the eye is complicated. METHODS: In this study, the spatial contrast sensitivity (CS) of 61 high ametropes wearing soft contact lenses with, and without, in-air spherical aberration compensation is measured. RESULTS: A slightly better overall performance was found with the standard lenses. There was no significant influence by the type of ametropia, age, and gender. If individual results are considered, clinically significant differences between the two lens groups are observed in approximately 30% of the cases. CONCLUSIONS: It seems that correcting in-air soft contact lens spherical aberration systematically is of no clinical interest. However, selective manipulation of spherical aberration could, in high power soft contact lenses, significantly improve CS in individuals.
RCT Entities:
BACKGROUND: In optical systems, it is usual to compensate for longitudinal spherical aberration. In order to increase image quality, lens surfaces can be made aspheric to bring all object light rays into focus at the image plane. Theoretically, soft contact lenses with high power and spherical surfaces show significant amounts of spherical aberration. The use of spherical aberration-free soft contact lenses could therefore improve retinal image quality in the case of high ametropia. However, because of ocular aberration, accommodation effects, pupil dynamics, contact lens flexure, and positioning, the computation of the spherical aberration induced when a contact lens is placed on the eye is complicated. METHODS: In this study, the spatial contrast sensitivity (CS) of 61 high ametropes wearing soft contact lenses with, and without, in-air spherical aberration compensation is measured. RESULTS: A slightly better overall performance was found with the standard lenses. There was no significant influence by the type of ametropia, age, and gender. If individual results are considered, clinically significant differences between the two lens groups are observed in approximately 30% of the cases. CONCLUSIONS: It seems that correcting in-air soft contact lens spherical aberration systematically is of no clinical interest. However, selective manipulation of spherical aberration could, in high power soft contact lenses, significantly improve CS in individuals.
Authors: Colm McAlinden; Jonathan E Moore; Victoria E McGilligan; Tara C B Moore Journal: Graefes Arch Clin Exp Ophthalmol Date: 2010-08-06 Impact factor: 3.117