Clinical pupillary constriction is rare. The more relevant neurological disorder is called Horner syndrome. The most common factor is cervical spondylosis, especially after surgery or a tumor in the neck that compresses the cervical sympathetic chain, resulting in ipsilateral pupillary constriction, smaller eye fissures, and no sweating on the ipsilateral side. However, it is not an isolated disease, but a symptom that accompanies other diseases, which are more common in neurology with a narrow pupil. There is also organophosphorus poisoning, that is, pesticide poisoning can lead to pupil narrowing, organophosphorus poisoning will be countered with a large amount of atropine, one of the signs of effective treatment is pupil dilation, indicating that the amount of anti-toxicant medication has been sufficient. It is still easier to pay clinical attention to pupil dilation, for example, damage to the intracranial oculomotor nerve or the oculomotor nerve at the eye can lead to pupil dilation, and pupil dilation in cases of vision loss, destruction of photoreceptor cells in the eye, and blindness.