An ophthalmic optical power measurement device (e.g., 320, 420, 720, 820, 920) can include a light source (e.g., 910) configured to direct an input beam of light into the eye of a patient. The ophthalmic optical power measurement device can also include an aperture (e.g., 330, 430, 730, 830, 930) configured to receive an output beam that consists of light from the input beam that scatters from a location on the retina of the eye and exits through the pupil of the eye. The ophthalmic optical power measurement device can also include a detector (e.g., 340, 440, 740, 840, 940) configured to receive the output beam after it has passed through the aperture. A processor (e.g., 370, 470, 770, 870, 970) can be configured to determine the size of a spot created by the output beam on the detector, and to determine the optical power of the eye based upon the size of the spot.
