A refractive measurement tool measures refractive aberrations of the human eye. The tool includes a variable lens system. One or more refractive attributes of the variable lens system—such as spherical power, cylindrical power, cylindrical axis, prism or base—are adjustable. The user holds the tool up to his or her eyes, and looks through the tool at a near or far scene. Iterative vision tests are performed, in which refractive properties of the variable lens system are changed from iteration to iteration.
