What makes pupils large

This effect can last two hours or longer after drug ingestion. A number of illegal drugs, however, do directly cause dilated pupils.

This slows your eyes' ability to react to light. This is an unusual but harmless condition where a person experiences sporadic episodes of one pupil suddenly becoming dilated, often accompanied by blurry vision, headache and eye pain.

Young women who are prone to migraine appear to have the highest risk of benign episodic unilateral mydriasis. In one study, the median duration of the episodes was 12 hours some lasted much longer and the median frequency was two to three episodes per month. Also called Adie's tonic pupil or tonic pupil , this is a rare neurological disorder where one pupil is larger than normal and is slow to react to light.

Sometimes, the pupil does not constrict at all. This pupil abnormality may be accompanied by poor or absent tendon reflexes. When this occurs, the condition is called Adie's syndrome. Generally, the cause of Adie's tonic pupil is unknown; but in some cases, it may be associated with trauma, surgery, poor blood circulation or infection.

There's no cure for Adie's pupil or Adie's syndrome. This is a rare condition where a person is born with a partially or completely absent iris, resulting in a very large "pupil. Because there is little or no iris to regulate the amount of light entering the eye, people with aniridia are very sensitive to light.

It's true — researchers have found that pupil dilation appears to correspond to adult men and women's sexual interest in other adults. But there's a catch. One recent study showed that the pupils of male subjects dilated when they viewed images of women they found sexually attractive, whereas the pupils of female subjects typically dilated in response to images of attractive men and women alike.

The colored ring around the pupil is the iris. This contains muscle fibers that control pupil size. The pupils get smaller or larger depending on how much light is necessary to allow for good vision. For example, the pupils increase with dim lighting to allow more light in and improve vision. In bright settings, the pupils become smaller to prevent too much light from coming in. When the pupils become smaller, this is known as pupil constriction. When they get larger, this is known as pupil dilation.

Changes in pupil size are involuntary. The autonomic nervous system controls pupil size. This is the same system that controls other automatic actions, such as breathing. However, other factors can also cause pupils to increase in size, or dilate. Some examples of these factors include :. In some cases, the pupils will dilate permanently.

For example, someone with congenital aniridia will have larger pupils all the time, due to a deficiency of the surrounding iris. For example, emotions such as anxiety may also cause changes in pupil size. This can be a result of the fight-or-flight response, which is involuntary. Eye contact has long been central to human interactions.

Changes in emotion might cause pupil dilation. The autonomic nervous system triggers various involuntary responses during emotions, such as fear or arousal. Some research suggests that pupil dilation is one of these involuntary responses to arousal or attraction. For example, one study recruited men and women with varying sexual orientations.

To do this, they react to the amount of light around you — brighter light makes your pupils grow smaller, while low light makes your pupils grow larger. Pupil size is controlled by the brain , which receives signals from each retina and sends a message for your eyes to adjust to the light.

Muscles in the colored part of your eye, your iris, then work to constrict or dilate your pupils, letting in more or less light as needed. There are many different types of medications that can interfere with the nerves that make your pupils dilate, including:.

Recreational drugs also affect your nervous system and can cause your pupils to dilate or shrink regardless of the light you're in. Some common drugs that affect your pupils include:.

For a full list of drugs that can dilate your pupils, see here. The nerve fibers that control the size of your pupil are within a larger nerve that originates in your brainstem called the oculomotor nerve. When this nerve is injured, it can cause many different problems in your eyes. Damage to the oculomotor nerve can also make your eyelid droop or limit your eye movement on the side of the injury Mackay says. Brain injury can be caused by something hitting your head, but you can also have an internal injury from a stroke , a brain tumor, or bleeding in your brain.

This type of injury can cause your brain to swell and press on the oculomotor nerve, making one or both of your pupils dilate, Mackay says. Medication What they treat What they do anticholinergics chronic obstructive pulmonary disorder COPD , nausea, motion sickness, overactive bladder OAB , urinary incontinence UI Anticholinergics block the action of the acetylcholine, a neurotransmitter involved in muscle contractions.

They include barbiturates like phenobarbital. Benadryl is a common OTC antihistamine. Both Ritalin and Adderall cause pupils to dilate. Can drug use cause permanent pupil dilation? Managing dilated eyes. When to seek help. The takeaway. Read this next. About Normal Pupil Sizes. Pinpoint Pupils. Medically reviewed by Graham Rogers, M. Is It Love? Medically reviewed by Debra Rose Wilson, Ph. Mydriasis: Understanding Dilated Pupils. Medically reviewed by Judith Marcin, M.

Medically reviewed by Alan Carter, Pharm. A Dozen of the Best Prescription Discounts.