Recovery Center Blog

How Do Different Drugs Affect the Pupils?

Written By Recovery Centers - March 21st, 2022
How Do Different Drugs Affect the Pupils?

When someone is abusing drugs it can be difficult to notice the signs, especially if they are working hard to hide their addiction. However, there is one foolproof way to spot drug abuse and it has to do with an individual’s eyes.

Individuals who abuse drugs will display abnormalities in their pupil size, the color of the white parts of their eyes, and the motion of their eyes depending on the substance they abuse. Oftentimes, law enforcement officers and medical professionals use pupil size and other eye-related symptoms to determine if an individual is under the influence.

Substances like alcohol and marijuana are known to cause bloodshot eyes, while stimulants and amphetamines cause the pupils to become enlarged. Knowing how different drugs affect the pupils can help individuals determine whether their loved ones are abusing substances.

How Common Addictive Drugs Affect the Pupils

Almost every single substance of abuse affects the eyes in one way or another. However, each drug may affect the eyes differently. For example, some drugs cause pupils to become enlarged (dilation), while others cause the pupils to become smaller (constriction).

Let’s take a look at common drugs of abuse and discuss how each one affects the pupils.


When someone is under the influence of alcohol, they often show symptoms of bloodshot eyes. Sometimes their eyes can appear glassy or watery as well. Alcohol may also cause blurry vision, rapid eye movements, and enlarged (dilated) pupils.[1]


While the pupils do not dilate or constrict, it is extremely easy to tell if someone has been smoking marijuana. Marijuana abuse is often associated with bloodshot and glossy eyes.[2,3] Also, people high on marijuana tend to squint their eyes or have difficulty keeping them open.


Amphetamines like ecstasy and methamphetamine cause blurry vision, dilated pupils, and rapid eye movement. The dilation associated with amphetamine abuse is extreme, often causing an individual’s eyes to look completely black.[3]

Extremely potent amphetamine drugs like crystal meth often cause nystagmus, which is involuntary and rapid quivering of the eyes.

Cocaine and Crack Cocaine

Cocaine and crack cocaine are stimulant drugs. They affect the brain by releasing endorphins and adrenaline, which causes the eyes to dilate substantially. While on crack or cocaine, people’s pupils may become very enlarged.[3]


When abused, benzodiazepines like Xanax and Klonopin can cause double vision and blurry vision.

If an individual’s pupils dilate while they are abusing benzodiazepines, they may be suffering from an overdose.[4] Emergency medical services should be contacted immediately in the case of a benzodiazepine overdose.


Hallucinogens are drugs that cause psychedelic effects. Examples of hallucinogens include LSD, mescaline, and psilocybin mushrooms. These drugs cause the pupils to dilate, often becoming so large that the eye appears completely black.


Both legal and illicit opioids cause the eyes to constrict. This means that the individual’s pupils will become pin-pointed (constricted) or extremely small. Additionally, opioids cause effects of sleepiness, which can lead to droopy eyelids.[3]


Ketamine can cause visual impairment similar to alcohol. However, this drug is also known to cause rapid involuntary eye movements and significant pupil dilation.[5]


GHB is a drug that is often used in date-rape situations. Often referred to as liquid ecstasy or liquid stranger, GHB causes pupils to appear pinpointed. This is because GHB is a depressant, causing the pupils to become smaller instead of larger.[5]

PCP (Phencyclidine)

People under the influence of PCP may have a blank stare as if nothing is going on in their heads. In other words, the eyes do not respond to visual stimuli when an individual is abusing PCP. However, they may experience rapid involuntary eye movements and bloodshot eyes.

Can Drug Addiction Cause Long-Term Eye Damage?

Long-term substance abuse is known to cause an array of health conditions like heart disease, diabetes, damage to the kidneys, and liver damage. However, drug addiction is also associated with several long-term vision problems.[3]

Substance abuse can lead to eye conditions because it causes significant damage to the eyes, ocular nerve, and brain over time. Some long-term eye conditions associated with drug and alcohol addiction include:

  • Age-related macular degeneration
  • Corneal damage
  • Dry eye syndrome
  • Endophthalmitis
  • Glaucoma
  • Hallucinogen persisting perception disorder (HPPD)
  • Lesions
  • Maculopathy
  • Ocular bone damage
  • Persistent changes in eye movement
  • Retinal vascular occlusive disease (RVOD)
  • Talc retinopathy
  • Toxic cataracts
  • Wernicke’s encephalopathy
  • Yellowed eyes

Drug abuse can lead to an array of medical conditions other than eye damage, including severe organ deterioration and even heart, liver, or kidney failure. With that being said, it is extremely important to attend a professional addiction treatment center to prevent drug addiction from causing long-term damage.

Preventing Eye Conditions by Getting Sober With the Help of a Professional Rehab Program

If you or a loved one suffer from substance abuse, professional addiction treatment can help you prevent irreversible damage to your eyes. Because drug addiction can lead to serious conditions like glaucoma and toxic cataracts, early intervention is key.

At Recovery Centers, our dedicated and experienced staff can help you or your loved one find the help you need. By providing in-depth assessments, we can find a drug and alcohol rehab program suited to your unique needs. To learn more about how to find an addiction treatment center near you, contact us today.