Is the quality of vision with contact lenses adequate? Not only adequate but often superior

Two factors govern the quality of vision with contact lenses (CLs): the fit and movement of the lens and the adequacy of its optics. Studies have not demonstrated any inherent inadequacies in material or design parameters that might account for visual difficulties in lens wearers. To the contrary, thickness, water content, and fit can be varied within clinically acceptable ranges without compromising vision. A poorly fitted lens, however, can cause excessive corneal edema and consequent visual problems. Poor vision may also result from uncorrected refractive error, the development of an unstable optical surface, or the use of a lens material that is inherently inadequate for a given patient. Such causes of visual dysfunction can usually be avoided through better fitting, better lens care, more careful refraction, or better patient-lens matching. Specialized lens designs can sometimes be used to correct vision problems. Certain types of rigid front-surface aspheric lenses, for example, provide astigmats with even better visual correction than spherical rigid lenses or spectacles, but the improvement is small and highly patient dependent. Similarly, although soft toric lenses can provide good vision, it is often technically difficult to orient and stabilize the correcting cylinder.