Band keratopathy is the result of precipitation of calcium salts on the corneal surface (directly under the epithelium). Serum and normal body fluids (eg, tears, aqueous humor) contain calcium and phosphate in concentrations that approach their solubility product. Evaporation of tears tends to concentrate solutes and to increase the tonicity of tears; it is especially true in the intrapalpebral area where the greatest exposure of the corneal surface to ambient air occurs. Elevated serum calcium or serum phosphate can tip the balance in favor of precipitation. Topical medications that contain phosphates also may contribute to this problem. Finally, elevation of the surface pH out of the physiologic range changes the solubility product and favors precipitation. This type of tissue pH change can be seen in chronically inflamed eyes and may explain, in part, why patients with uveitis are at risk for the development of band keratopathy.[1 ]