Abstract: A microscope lens system is provided which facilitates rapid, convenient, and accurate substitution of one eyepiece lens for another. The microscope tube is provided with an opening and an internal receptacle communicating with that opening at the location where an eyepiece is to be supported. Each eyepiece lens unit comprises an actual eyepiece lens mounted in a clip member that encircles the lens and that meets with the receptacle to securely and precisely retain the eyepiece lens at the appropriate position along the optical axis of the microscope. A light shield, preferably integral with the remainder of the eyepiece lens unit, masks the opening in the tube when the eyepiece lens is in place within the tube.