Under normal circumstances, the pupil’s response to light is very sensitive, but in some cases the response to light may become extremely slow or even disappear, mainly in the following cases: 1, ocular diseases: such as pupillary atresia, pupillary membrane closure, post-pupillary adhesions, extremely severe ischemic optic neuropathy, ophthalmic artery obstruction, absolute glaucoma, and trauma-induced optic nerve fractures, which can cause optic nerve damage 2, systemic diseases: such as cranial tumor compression, cerebral hemorrhage, cerebral infarction causing optic nerve compression, or patients in a deep coma can cause the pupil to lose its response to light. Pupillary loss of light response should be seen by a regular medical institution in a timely manner to determine the cause and treat accordingly.