How Drugs Affect Your Eyesight: Weed, Alcohol, Tobacco, LSD and Cocaine

Yes, drugs can affect your vision, from short-term changes like red eyes, dilated pupils or blurry sight to lasting damage such as cataracts, optic nerve injury or retinal bleeding. Psychoactive substances, legal and illegal, can mess with visual perception in all kinds of ways, and the risk depends on the drug and how often you use it.

The effects range from temporary vision changes to permanent eye damage, and they vary a lot depending on the substance and the frequency of use. Knowing how drugs affect your eyesight is key to understanding the risks and making informed choices about your eye health.

How cannabis affects your eyesight

Cannabis doesn't just turn your eyes red; it has other effects on vision too. A study in humans found that regular weed use can slow down how the retina processes visual information.

It's not all bad news, though. Another study identified a cellular mechanism through which cannabis may improve night vision. That research grew out of reports about Jamaican fishermen who smoke weed regularly and are said to have excellent night vision.

In the study, researchers added cannabinoids to retinal cells from tadpoles and found the cells became more sensitive to light.

Why does weed make your eyes red?

THC, the psychoactive compound in cannabis, is what makes your eyes red. It lowers blood pressure and widens blood vessels (vasodilation), which increases blood flow and turns the eyes red.

That same property is why cannabis has been used to ease glaucoma, a condition where pressure inside the eye climbs to dangerous levels. Research suggests weed can temporarily lower that pressure and may help prevent further damage.

It's important to have the dose managed by a doctor, since cannabis side effects can also be harmful to your health.

How LSD affects your vision

LSD is a synthetic drug whose effects play out in three phases:

1. Central nervous system (CNS) stimulation: It raises your heart rate and body temperature and dilates your pupils.
2. Psychedelic phase: Users experience a mix of synesthetic sensations, even "seeing sounds."
3. CNS depressant phase: In this phase, the risk to your vision is at the level of the retina, caused by the high blood pressure the drug can trigger.

It's essential to understand the risks of these substances and how they can affect your vision in the short and long term.

How alcohol affects your eyes

Alcohol is one of the most widely used drugs in the world, and it's regulated in many parts of daily life. In Spain, for example, the legal blood alcohol limit for driving is 0.5 g/l. Going over that can have noticeable effects on the body, and especially on vision.

Vision problems caused by alcohol

Alcohol is no exception when it comes to drugs affecting eyesight. It can cause a whole list of vision problems, even at relatively low blood alcohol levels:

1. Weaker night vision: Known as night blindness (nyctalopia), it makes it harder to see in low light.
2. Slower reflexes: The brain can't process information as quickly, which slows your reaction time.
3. Narrower field of vision: Your peripheral vision takes a hit, making it harder to notice objects or people off to the sides.
4. Sluggish pupils: Your pupils take longer to adjust to changes in brightness.
5. Trouble telling colors apart: Your ability to distinguish certain colors drops.
6. Blurry vision with farsightedness: The lens doesn't focus properly, which can blur your vision.
7. Damaged tear film: Researchers at the University of Granada in Spain found that heavy drinking degrades the quality of the tear film.
8. Loss of essential vitamins: Drinking depletes vitamins like B1, B6, riboflavin and niacin, which can lead to gradual vision loss.

Wernicke syndrome

People who drink heavily every day can develop Wernicke syndrome (Wernicke's encephalopathy), whose main symptoms include:

• Damage to the nerves that move the eyes, causing involuntary eye movements (nystagmus).
• Drooping of the upper eyelid (ptosis).

How tobacco affects your vision

Nicotine is the main addictive substance in tobacco, and its effects hurt not just your lungs but your eyesight too.

Vision problems caused by tobacco

1. Reduced contrast sensitivity: Trouble picking out details between similar visual cues.
2. Optic nerve damage: Using nicotine and alcohol together can damage the fibers of the optic nerve and affect color vision.
3. Macular degeneration: In extreme cases, it can damage the macula, the part of the retina responsible for sharp central vision, causing irreversible blindness.
4. Cataracts: Smoking speeds up the onset and development of cataracts.
5. Damage to the tear film and cornea: Tobacco smoke degrades the tear film and can damage the cornea.

Can medications affect your vision?

Some medications, even though they're not considered drugs in the traditional sense, can have significant side effects on your vision.

Vision problems caused by medications

1. Antihistamines: Dry eyes, blurry vision and more tearing.
2. Antibiotics: Changes in color perception, burning eyes and more sensitivity to light.
3. Birth control pills: Dry eyes.
4. Antiarrhythmics: Seeing halos around objects or lights.
5. Corticosteroids: Higher eye pressure (glaucoma) and cataracts.

How cocaine affects your eyesight

Cocaine is a highly dangerous drug that hits the central nervous system fast and can have serious consequences for your vision.

Vision problems caused by cocaine

1. Higher blood pressure: It can burst blood vessels in the eye, leading to bleeding and even total vision loss.
2. Inflamed tear ducts: Snorting cocaine can cause swelling in the tear sac, which is painful.
3. Retinal detachment: It can cause a significant drop in visual sharpness.

Understanding how these substances affect your vision is crucial for making informed decisions about using them. Prevention and moderation are key to keeping your eyes healthy.