Optometer is a term used to refer to a device that is used to measure refractive errors in the eyes, especially for the purpose of prescribing corrective lenses for clearer vision. There are several synonyms for the word optometer, including refractometer, autorefractor, and wavefront analyzer. Refractometer is a device that measures the refractive index of a substance or material, while an autorefractor is a non-invasive instrument used to measure the refractive error of the eyes. Wavefront analyzer is a device used to measure the way light travels through the eyes, especially the cornea and lens. The use of any of these synonyms in place of optometer would still convey the same meaning.