Dilated Pupil

Which Drugs Cause Pupil Dilation?

Your pupils are the black dots in the middle of your eyes which allow light to enter. Around the pupil is the iris, which controls the opening of the pupil. Pupil dilation happens when any one of the two muscle groups – iris sphincter or iris dilator becomes activated. Pupils change in size to focus on distance. They also change in size as a response to light. Emotions can also cause dilation or chemical changes in the body.

Mydriasis is the name for Dilated Pupils

Dilated pupils (Mydriasis) can also be a sign of drug abuse. This is often referred to as ‘blown pupils’ where the pupils stay excessively large even in a bright light environment.

Pupil dilation may be an indicator of stimulant drug usage. These drugs can cause pupil dilation:

Dilation of this kind is temporary as the pupil returns to normal as soon as the effect of the drugs wear off.

How cannabis effects the pupil is controversial. For some there might be increase in the pupil size, whereas the reported enlargement in certain other cases may be so less that it might not be visible to the naked eye. Also, infection in the conjunctivitis is a common side effect of smoking cannabis. Cocaine intake can also cause short term dilation of the pupils. In fact, even moderate doses can lead to pupil dilation.

Miosis is the name for Constricted Pupils

Opiates have a totally different effect on the pupil and cause pupil constriction or miosis (often called “pin-point pupils”). However, withdrawal from opiates may resulted in dilated pupils.

The role of parents plays a significant part in preventing drug use in adolescents. As early as the problem is addressed, more is the chance of avoiding potential damage. These are the aspects that can even cause teenagers to get dilated pupils due to drug intake. Tackling the issue with research and understanding is crucial to combat overly permissive or overly aggressive attitude towards the addict.

Photo Credit: “Eye” (CC BY 2.0) by Sam Bald

This post has been updated since its original publication in 2015.