ŏp'/si-ŏm'e-ter, n.

n. [Fr. opsiomètre, from Gr. ὄψις, sight, from the root ὀπ-, future ὄψομαι, to see, and μέτρον, measure.] An instrument for measuring the extent of the limits of distinct vision in different individuals, and from that to determine the focal length of a lens necessary to correct imperfect sight. Brandé.