A photocoagulation apparatus of some embodiment examples is configured to apply both treatment light for subthreshold coagulation and an OCT scan to a retina via a probe inserted in an eye. Upon receiving a user's instruction, the apparatus applies the treatment light to the retina, and applies an OCT scan to the retina at least after the treatment light application. The apparatus compares the first OCT image constructed from OCT data of the retina acquired prior to the treatment light application and the second OCT image constructed from OCT data of the retina acquired after the treatment light application, thereby acquiring change information that represents a tissue change in the retina caused by the treatment light. The apparatus displays a change image based on the change information together with a retinal image.