Horner syndrome can be seen in people of all ages, with the actual onset being more common in men. The clinical symptoms are mainly ipsilateral sympathetic nerve damage, unilateral pupillary constriction (pupil narrowing), ptosis (narrowing of the eye fissure) and inversion of the eyeball are the three characteristic symptoms of the disease. The disease is a serious threat to the physical and mental health of patients, so it is important to check and treat the disease as soon as possible if the early symptoms of the disease appear. The examination methods for Horner syndrome are as follows: 1. Unilateral pupillary constriction (pupil narrowing), ptosis (narrowing of the eye fissure) and intraocular sunkenness are the three characteristic symptoms of this disease. 2. Transepithelial membrane may be seen to be loose and prominent. Sometimes it covers half of the eye in a fixed position. 3. The ability to close the eyelid and the pupil’s ability to reflect light are still maintained, but corneal dryness can occur if the closure is incomplete. 4. The upper eyelid of the sick cat is raised and it is difficult to open the eye. In the case of entropion due to ptosis, there is more tearing. Dilation of the conjunctival vessels is indeterminate. 5. The time occurs, often in the late afternoon or early morning. Drinking alcohol or nitroglycerin can provoke headache attacks. The headache is often confined to the same side.