Optical diagnostic
An optical diagnostic was a type of medical diagnostic that focused on the eye. 

In 2368, after Geordi La Forge came into sickbay with symptoms of an ear infection, including dizziness, Dr. Beverly Crusher, on a hunch, ran an optical diagnostic which traced the problem to his VISOR, which was causing a phase shift in his visual receptors. The condition made him see images, or as he described them, "blurry after-images", that weren't really there. Crusher then ran a scan to detect what he was seeing, and was able to pick up minuscule distortions in the surrounding dekyon field, distortions which the VISOR translated into visual impulses. ()

Medical scans