Therapeutic uses of contact lenses.

Therapeutic use of contact lenses is an essential element in ophthalmic care. Materials currently in use include polymethyl methacrylate (PMMA), cellulose acetate butyrate, siloxane-containing polymethacrylates, silicones, and hydrogels. Suitability of a material for therapeutic contact lens use is determined by the physical, chemical, and mechanical properties (notably gas permeability and hydrophilicity, but also lipid absorption and lens movement, among others) and the condition to be treated; fabrication techniques are likewise important, affecting lens diameter and base curve. Selection and fitting of therapeutic contact lenses requires knowledge of how different contact lenses affect corneal physiology, as well as an understanding of the mechanisms whereby a contact lens can be therapeutic. In addition to these topics, general fitting guidelines are discussed, and results of therapeutic lens use in selected clinical situations (including recurrent erosion, metaherpetic ulcers and other epithelial defects, and keratitis sicca, and other dry eye states). Common therapeutic contact lens complications and their treatment are also discussed.