A display device and method of operating the display device is disclosed. The display device and method accurately compensate for the degradation of subpixels by monitoring the degradation in real time using an optical electronic device located under, or at a lower portion of, a display panel and partially overlapping an optical area in the display area. Such monitoring of the degradation can be performed in real time using such an optical element or device even in a situation where the display device is used, and the compensation of the degradation can be performed in real time in accordance with the result of the monitoring.