Stoned Eyes: What Pupil Size Can Tell You About Drug Use

Pupil dilation, your eyes becoming bloodshot, and motion can indicate drug use. However, there are other conditions that can trigger these symptoms.

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Alcohol and drug use causes many side effects, including nausea, mood changes, aggression, loss of coordination, and temporary changes to the eyes.

Temporary changes in pupil size, motion, and color of the whites can be used to determine if someone is intoxicated.

Bloodshot eyes are also a common symptom of intoxication from several drugs, including alcohol.

The Effect Of Drugs On Pupil Dilation And Constriction

Numerous illicit drugs cause unwanted physical changes in the body. Certain drugs cause pupil dilation, also known as mydriasis, while others cause pupil constriction or miosis.

Hallucinogens such as lysergic acid diethylamide (LSD), mescaline, MDMA, and psilocybin, as well as stimulants like amphetamines and dissociative anesthetics like ketamine, may cause pupil dilation.

Other signs of central nervous system involvement, such as an altered level of consciousness, visual impairment, and agitation, often accompany pupil dilation.

Opioids, including morphine, heroin, fentanyl, hydrocodone, and oxycodone, may cause pupil constriction, also known as pinpoint pupils.

How Do Drugs Affect Pupil Dilation And Constriction

Most commonly, the drugs that cause dilated pupils act through the iris parasympathetic neurotransmitter receptor blocking, which keeps the pupils open and prevents contraction.

Drugs create pupil constriction by activating the pupillary sphincter muscle to prevent dilation of the eye.

Constriction of the pupils may also be accompanied by slow breathing and slowed physical activity.

Pupil Size As A Diagnostic Tool

The Drug Evaluation and Classification (DEC) is a program that uses pupil size as a diagnostic tool for law enforcement officers.

The DEC was developed to detect, arrest, and convict drivers impaired by drugs other than alcohol.

Trained officers measure pupil sizes using standard protocols under three light levels, near-total darkness, direct light, and room light, to determine if a person is intoxicated.

Healthcare providers often use a pupillometer to measure pupil size. With pupillometer screening, the eye is scanned with a series of flashing lights and given a controlled amount of
light to measure its involuntary reflexes.

The instrument is able to identify the specific drug causing the observed effects, including cannabis, opiates, cocaine, amphetamines, depressants, inhalants, and methamphetamines.

Other Factors That Can Affect Pupil Size

There are a variety of other factors that affect pupil size. In bright light, pupils constrict to prevent light from entering, and in the dark, pupils dilate to allow more light in.

Other factors that can cause dilation are:

  • eye drops for dilation from an eye exam
  • glaucoma
  • a brain injury
  • increased production of oxytocin
  • adrenaline
  • eye injury
  • migraine or ocular migraine
  • Adie’s pupil
  • microvascular cranial nerve palsy
  • OTC and prescription drugs, such as antidepressants, antihistamines, and anti-seizure medications

If you or a loved one is experiencing pupil dilation, it is crucial to consult a doctor as it may be a sign of injury or a medical condition.

Pupil constriction is also caused by:

  • Horner’s syndrome
  • poisoning
  • uveitis
  • swelling of the iris
  • injury to the brain or eye, including stroke
  • neurosyphilis
  • inflammatory adhesions
  • cluster headaches

If you or a loved one is experiencing pupil constriction, it can be a sign of serious health effects. Seek medical help immediately.

Additional Warning Signs That Indicate Drug Use

There are a variety of other signs indicating drug use, including physical changes in the body and the presence of various types of paraphernalia.

Behavioral Changes

There are a variety of behavioral signs indicative of drug abuse. These warning signs may indicate that there is a problem happening that needs to be looked at.

Behavioral signs include:

  • secretive or suspicious behaviors
  • neglecting responsibilities at home, school, or work
  • mood swings
  • depression
  • confusion
  • poor judgment
  • nervousness
  • irritability
  • paranoia
  • taking a substance in large amounts
  • taking risks such as driving under the influence
  • anxiety
  • elevated mood

If someone you care about is showing any of these signs, it could be an indicator of addiction or another serious health condition that needs medical attention.

Physical Signs

The physical signs of drug use vary based on what substance is being abused, as well as other factors.

Physical signs of substance abuse may include:

  • weight loss or gain
  • lack of hygiene
  • high or low heart rate
  • high or low blood pressure
  • cravings
  • changes in sleep patterns
  • slurred speech
  • blurred vision
  • tremors
  • changes in appetite
  • dry mouth
  • red eyes
  • vomiting
  • nausea
  • chest pain
  • vision loss
  • other eye changes to the cornea or retina
  • involuntary eye movements
  • dizziness
  • increased alertness

If a loved one is exhibiting any of these physical signs, they may need to seek medical care for a serious medical condition or substance use disorder.


The paraphernalia a person may be using to abuse substances depends on the substance being abused, how advanced the addiction is, and other factors.

Examples of paraphernalia may include:

  • pipes of various types
  • spoons
  • plastic or small paper bags
  • markers of various types
  • needles
  • e-cigarettes
  • bongs
  • cigarette papers
  • gum or candy wrappers
  • lighters
  • plastic pen caps or cases
  • razor blades
  • belt buckles
  • cut up pieces of plastic
  • paper tubes
  • tin foil

Many common everyday items may be used to abuse drugs, which may make sources of paraphernalia difficult to identify.

If a family member or friend is exhibiting other signs of substance abuse along with having paraphernalia, they may be living with addiction.

Learn About Addiction Treatment At Bedrock Recovery Center

If you or a family member are looking to learn more about drug addiction treatment, we can help.

Contact us at Bedrock Recovery Center to learn more about our treatment center and treatment options.

  1. American Academy of Ophthalmology (AAO)
  2. Cleveland Clinic
  3. Cleveland Clinic
  4. Drug Enforcement Administration (DEA)
  5. Drug Enforcement Administration (DEA)
  6. Indian Health Service (IHS)
  7. Indiana Department of Health
  8. John Hopkins Medicine,to%20physical%20or%20psychological%20problems/
  9. National Library Of Medicine: PubMed
  10. National Library Of Medicine: PubMed
  11. National Library Of Medicine: PubMed
  12. National Library Of Medicine: PubMed
  13. National Library Of Medicine: PubMed
  14. United States Department of Justice (DOJ)
  15. United States Department of Veterans Affairs

Written by Bedrock Recovery Center Editorial Team

Published on: December 6, 2023

© 2024 Bedrock Recovery Center | All Rights Reserved

* This page does not provide medical advice.

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