Lensometer is an ophthalmic optical instrument used to measure and verify the optical power of eyeglass lenses and other corrective lenses. It helps eye-care professionals determine sphere, cylinder, axis, prism, and lens power, as well as verify whether lenses match the prescribed specifications. Lensometers are widely used in optical stores, optometry clinics, and ophthalmic laboratories for accurate lens inspection, prescription verification, and quality control.