When it comes to substance abuse, the adage “the eyes are windows to the soul” rings especially true.

When a person is under the influence, several changes in the eyes can be observed: they appear bloodshot and dilated, with the pupils moving rapidly and involuntarily.

This article discusses what happens to eyes on shrooms as well as other substances to help you detect signs of addiction early on.

What Happens to Your Eyes on Shrooms?

When you take psilocybin mushrooms (shrooms), your eyes undergo noticeable changes due to the drug’s effects on the nervous system. These changes are primarily caused by psilocybin’s interaction with serotonin receptors (5-HT2A), which influence visual perception and pupil size.

1. Pupil Dilation (Mydriasis)

One of the most common effects of shrooms on the eyes is pupil dilation.

• Psilocybin triggers serotonin release, which overstimulates the nervous system, leading to enlarged pupils.
• This is part of the “fight or flight” response, increasing light intake and enhancing visual sensitivity.
• How long does it last? Pupils usually remain dilated for 4-6 hours but may persist for up to 24 hours in some cases.

2. Visual Distortions & Hallucinations

Shrooms significantly alter how your brain processes visual information. Common visual effects include:

• Increased brightness & color saturation – Everything may appear more vibrant or glowing.
• Patterns and tracers – Stationary objects may appear to move or breathe, and trailing lights may follow moving objects.
• Shape & depth distortions – Walls may appear to melt, and objects may seem larger or smaller than they are.
• Synesthesia (Crossed Senses) – Some people experience “seeing” sounds or “feeling” colors.

3. Blurry Vision & Difficulty Focusing

• Some users report temporary blurred vision or difficulty focusing on objects.
• This may be due to altered depth perception or eye muscle fatigue from prolonged dilation.
• In higher doses, visual distortions may become intense enough to cause disorientation.

4. Light Sensitivity (Photophobia)

• Since pupil dilation increases light intake, bright lights can feel overwhelming or painful.
• This effect peaks during the trip but can linger for several hours afterward.

5. Uncontrollable Eye Movements (Nystagmus)

• In rare cases, shrooms can cause involuntary rapid eye movements (nystagmus), making it hard to focus.
• This is more likely with high doses or in individuals prone to neurological sensitivity.

6. Dry or Watery Eyes

• Some users experience dry, itchy eyes due to reduced blinking while staring at visuals.
• Others may have excessive tearing, possibly due to sensory overload or emotional responses during the trip.

7. Long-Term Effects on Eyes

While most effects fade within 24 hours, some users report lingering pupil dilation or sensitivity to light for several days after a high-dose trip.

• Can shrooms cause permanent eye damage?
• There is no scientific evidence that psilocybin mushrooms permanently damage the eyes or vision.
• However, some case studies suggest chronic hallucinogen use may cause persistent visual disturbances, known as Hallucinogen Persisting Perception Disorder (HPPD).

Shrooms significantly impact vision and eye function due to their hallucinogenic and neurological effects. While pupil dilation, visual distortions, and light sensitivity are temporary, high doses or frequent use may lead to long-term perception changes in rare cases.

If you experience lasting visual disturbances after using shrooms, seeking medical advice or an eye exam may be beneficial.

What Are the Side Effects of Taking Shrooms?

Shrooms, also known as psilocybin mushrooms or magic mushrooms of the genus Psilocybe, are fungi with hallucinogenic properties. When ingested, they can cause short-term and long-term mental health problems and physical effects. They can alter a person’s thinking, senses, and emotions.

Common mental side effects of psilocybin include:

• Distorted sense of reality
• Altered sense of time
• Mixed senses, such as seeing music or hearing color
• Light-headedness
• Anxiety
• Panic attacks
• Changes in mood
• Fear or paranoia
• Confusion and disorientation
• Loss of boundaries
• Impaired judgment

On the other hand, common physical side effects include:

• Exaggerated reflexes
• Numbness, especially on the face
• Dry mouth
• Nausea
• Vomiting
• Excessive sweating
• High body temperature, followed by chills
• Increased heart rate
• Increase blood pressure

When taken in high doses, users may experience what’s called a “bad trip.” These experiences are often frightening and may include a distorted sense of self, loss of boundaries, paranoia, abrupt flashbacks, and impaired judgment. Bad trips can also lead to risk-taking behavior, which may result in traumatic injuries and, in some cases, death.

Users who take shrooms alongside other substances like amphetamines, cannabis, and alcohol elevate the risks of serious side effects. The same is said for users with existing psychiatric conditions.

With users with existing heart disease, short-term effects like increased heart rate and blood pressure could potentially result in cardiac arrest.            

Can Shrooms Induce Permanent Pupillary Changes?

The long-term effects of shrooms have yet to be thoroughly investigated. However, some studies suggest that shrooms can induce pupillary changes in users.

In a study published in the Center for Neuropsychopharmacology, researchers found that psilocin and psilocybin, which are substances present in magic shrooms, are structurally related to the “feel good” neurotransmitter receptor serotonin. It’s concluded that shrooms can increase the levels of serotonin in the brain, which can result in the dilution of pupils. 

The permanence of such dilation is debated across all fields.

In a case report that reviewed the long-term effects of Novel Psychoactive Substances (NPS), a patient with a history of substance use and misuse developed permanently dilated pupils in both eyes.

It is said that the dilation correlates with the repeated and long-term use of hallucinogens, particularly LSD (acid) and psilocybin mushrooms. The condition started at age 11, shortly after she started using, so it wasn’t congenital but rather acquired.

“Certain pathophysiological changes can influence the pupillary aperture,” said medical doctor and researcher Dr. Ahmed Al-Imam. Some of these pathophysiological changes can be triggered by psychedelic drugs.

Neurological exams failed to detect any abnormalities outside the dilated pupils, so the dilution was unlikely to have been caused by existing neurological disorders.

Dr. Ahmed Al-Imam’s case is one of the few cases that documented the long-term effects of psychedelics, NPS, and other psychoactive chemicals. While permanent dilution is still non-conclusive, the study shows that it can’t be ruled out completely.

Other Substances That Cause Pupillary Changes

Shrooms aside, there are a number of drugs and substances that can trigger pupillary changes. These are as follows:

Marijuana

Marijuana, also known as cannabis, contains a psychoactive constituent called tetrahydrocannabinol (THC).

THC lowers blood pressure, triggering the increase of blood flow and the dilation of blood vessels. Lowered blood pressure causes the blood vessels in the eyes to expand, leading to redness or bloodshot eyes.

Marijuana also slows down the brain’s image-processing function. Under the influence of marijuana, hand-eye reflexes are reduced, and spatial perception is disrupted.

Pupil dilation provoked by cannabis can create imbalances and dazzlements between far vision and near vision. This effect is especially apparent among those who wear multifocal contact lenses and those who have had laser surgery such as Lasik, PRK, Lasik, Relex, or Smile.

Methamphetamine

Meth users often develop “meth eyes,” a term that describes a wide range of signs and symptoms associated with meth abuse. These symptoms include dilated pupils, bloodshot eyes due to increased visibility of blood vessels, and yellow eyes.

Meth can also cause Crystalline retinopathy, which refers to a group of disorders associated with crystal deposits in and/or around the retina.

Crystalline retinopathy is what causes the yellowing of the eyes of meth users, often a result of intranasal methamphetamine use (i.e., administered by way of the nasal structures). If left without treatment, Crystalline retinopathy can cause:

• Sensitivity to light
• Night blindness
• Deteriorating vision
• Uncontrollable twitching of the eyelids

Other effects of meth on the eyes include rapid eye movement, blurred vision, and retinal vein occlusion (RVO), one of the most common causes of vision loss worldwide.

Cocaine

Dilation is one of the more noticeable effects of cocaine use.

Cocaine is a stimulant, meaning that it can trigger the release of chemicals and endorphins in the brain. Among these chemicals is norepinephrine, a neurotransmitter that can cause pupil dilation due to it activating the body’s “fight-or-flight” response.

Bloodshot eyes are another common effect of cocaine use. Like marijuana, cocaine causes blood vessels to constrict, which then increases blood pressure. This results in bloodshot eyes that can last anywhere from a few hours to several days after use.

Over time, cocaine abuse can lead to an array of eye conditions, including:

• Exophthalmos: Bulging or protruding eyeballs
• Cycloplegia: Paralysis of the ciliary eye muscle
• Upper eyelid retraction: Increased resting position of the upper lid
• Corneal ulcers/injuries: Open sore on the cornea

Alcohol

Short-term exposure to alcohol can lead to dilated pupils, blurry vision, and night blindness.

Alcohol can likewise alter a person’s ability to perceive contrast. Consuming alcohol above the legal limit of 0.05% affects a person’s ability to visually adjust to the brightness, making distinctions between bright objects like stoplights more difficult.

Regular consumption of alcohol can result in dry eyes and eyelid twitching (myokymia). Myokymia can trigger short-term double vision and inflammation, which can cause itchy eyes, light sensitivity, and migraines. It can also cause the blood vessels of the eyes to expand, making them appear red and bloodshot.

Long-term consumption of alcohol can trigger the development of premature cataract formation, permanent blurriness caused by the weakening of eye muscles, retinal bleeding from vascular occlusions, and, in severe cases, optic neuropathy.

Left untreated, optic neuropathy can lead to reduced color vision, decreased peripheral vision, and, eventually, complete loss of vision.

Opioids

Opioids are a class of drugs that contain active ingredients derived from the naturally-occurring poppy plant Papaver somniferum. These drugs include heroin, codeine, meperidine, methadone, and morphine, as well as prescription opioids such as fentanyl, hydrocodone, pentazocine, and oxycodone.

Opioids stimulate the parasympathetic nervous system, which can result in the decreased velocity of pupil dilation when eyes come in contact with light. In other words, opioids can impair the pupil’s response to light.

These drugs may also trigger several eye abnormalities, such as droopiness, temporary blurred vision, and double vision.

If used long-term, opioids can cause several retinal issues, such as eye infections, which can lead to photophobia and vision loss.

MDMA

MDMA (methylenedioxymethamphetamine), otherwise known as Molly or Ecstasy, is reported to cause severe eye problems and complications like retinal hemorrhage and intravascular thrombosis.

Retinal hemorrhage occurs when blood vessels in the retina begin to bleed, while intravascular thrombosis occurs when the body is affected by inflammation from an infection, injury, or illness.

These complications are associated with the long-term use of MDMA. MDMA elevates noradrenaline levels, thereby provoking hypertension and tachycardia

The short-term effects of MDMA, though less severe, shouldn’t be understated. Much like the substances on this list, MDMA can cause pupil dilation, blurriness, and distorted perception. It can also cause redness and rapid quivering of the pupils (nystagmus).

Benzodiazepines

Known for their calming effects, benzodiazepines, also known as benzos or BZDs, are used to offset the side effects of withdrawal, reduce seizures, and produce sedation and hypnosis. In this way, they’re often classified as a type of tranquilizer.

Common names of benzos include Valium, Xanax, Ativan, Halcion, and Klonopin.

Because of their potency and availability, benzos are easily abused. At recreational doses, they can cause blurry, altered, or double vision and dilated pupils, with the latter being a sign of an overdose. Other symptoms of overdose include ataxia, slurred speech, and altered mental status.

When taken with alcohol or other drugs, respiratory depression resulting in a coma can occur.

Wrap Up

Whether it’s shrooms, meth, benzos, or alcohol, pupil dilation and bloodshot eyes/redness are the biggest tell-tale signs of substance abuse.If someone you know appears to have enlarged pupils and bloodshot or glassy eyes, checkout clinicalTrials.gov  and watch out for accompanying symptoms of addiction. This is important because as the symptoms progress, they’ll become harder to treat.