Visual receptor
Visual receptors were retinal cells found in a humanoid eye that functioned as sensory receptors by converting light stimuli into nerve impulses.
Kelpiens possessed visual, auditory, and tactile receptors that were more acute than those of Humans. (DIS: "Si Vis Pacem, Para Bellum")
In 2368, after Geordi La Forge came into sickbay with symptoms of an ear infection, including dizziness, Dr. Beverly Crusher ran an optical diagnostic and found that La Forge's VISOR had caused 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. (TNG: "Cause And Effect")