What is an instrument devised by Helmholtz for measuring the size of a reflected image on the convex surface of the cornea and lens of the eye, by which their curvature can be ascertained called?

ophthalmometer — An instrument devised by Helmholtz for measuring the size of a reflected image on the convex surface of the cornea and lens of the eye, by which their curvature can be ascertained. (Webster's 1913.)

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