A system for performing quasi-elastic light scattering and fluorescent ligand scanning on a subject's eye includes a light source configured to transmit light toward the subject's eye, a lens configured to focus light sent from the source and scattered by the subject's eye, a measurement reflector disposed to receive at least a portion of the focused light and configured to reflect a first portion of the received light, a camera configured and disposed to receive the first portion of the received light and configured to provide indicia of an image corresponding to the first portion of the received light, and a processor coupled to the camera and configured to analyze intensities of light in the image to determine a location of a reference point corresponding to an interface of a portion of the eye.