Abstract: An optical system for the reflecting microscopic examination of objects. An illuminating beam path and an observation beam path are provided along with an optical lens such that the beam paths pass through the optical lens and make an angle with each other. The lens is made up of two portions interfacing in a plane which bisects the angle of the beam paths and is perpendicular to a plane containing the beam paths. The interface between the lens portions is at least partially opaque and serves to absorb or reflect light reflected from the lens/object interface and thereby prevents such light from obscuring light reflected from surfaces interior to the object. The optical system is particularly advantageous for the examination of biological tissue such as the endothelium layer of the cornea of the eye.