How do soft contact lenses affect spherical aberration?
The curvature of the front surface of any soft contact lens, when placed on the eye, will vary with its power, thickness and lens flexure. A minus lens used to correct myopia will reduce the dioptric curvature of the combined soft lens/corneal surface, and as a result, will reduce the spherical aberration at the eye’s front surface. However, this soft lens/corneal spherical aberration is often over-reduced, so much so that minus lens powers cause the compensating power of the crystalline lens to be unopposed. This can cause an overall increase in spherical aberration for these eyes. In the case of a plus lens used to correct hyperopia, the increased dioptric curvature of the soft contact lens/corneal surface will also increase spherical aberration. The resulting vision is less than ideal, including reduced visual acuity, contrast sensitivity and low depth of field.
