refractometer re·frac·tom·e·ter (rē'frāk-tŏm'ĭ-tər)
n.
Any of several instruments used to measure the refractive index of a substance.
refractometry re·frac·tom·e·try (rē'frāk-tŏm'ĭ-trē)
n.
Measurement of the refractive index of a substance with a refractometer.
Use of a refractometer in determining the refractive error of the eye.