Meth's effect on eyes
Methamphetamine (meth) is an addictive substance that can harm the central nervous system with chronic use. It can affect the body, brain, and overall health, including the eyes. Meth can impair eye function and affect their appearance. This appearance is sometimes referred to as “meth eyes.”
A person may experience vision changes directly after using meth. These can include distorted or blurred vision, dilated pupils and hallucinations. The increased stimulation from the drug may also lead the user to continuously touch or rub their eyes, which can damage the eye’s tissues.
Long-term meth use can lead to addiction, mood disturbances and psychosis, among other concerns. If you or a loved one is struggling with addiction, please seek treatment from a health care provider.
Vision changes caused by methamphetamine use
Meth usage can cause issues throughout the body. These include changes to the eyes and visual processing, such as:
Dilated pupils (mydriasis)
Pupil dilation occurs when the eye’s pupil enlarges to allow more light to enter the eye. Pupils are the black circles at the center of each eye. They expand or shrink automatically to help manage the amount of light entering the eye.
However, the pupils can dilate in response to other factors, including methamphetamine use. When the pupils enlarge due to something other than light, it is referred to as mydriasis.
Mydriasis can lead to blurred vision, light sensitivity (photophobia) and headaches.
SEE RELATED: What causes pupil constriction (miosis)?
Visual hallucinations
In simple terms, a visual hallucination is when a person sees something that is not there. In other words, their brain perceives a visual cue, even though that cue is not real. When a person takes meth, they may experience visual and other types of hallucinations. This is a characteristic of a condition called methamphetamine-associated psychosis (MAP).
For most individuals, the MAP state will subside shortly after its initial onset. However, some may experience ongoing issues with psychosis and hallucinations.
Amaurosis fugax
Amaurosis fugax is a type of vision loss often described as though a curtain has been drawn over the eye. This vision loss is temporary and painless.
Amaurosis fugax is caused by an interruption of blood flow to the retina. The retina is the light-sensitive membrane at the back of the eye. It is responsible for transforming the light that enters the eye into nerve signals. These signals are then sent through the optic nerve to the brain, where they are interpreted into what you see.
Meth causes the blood vessels to narrow (vasoconstriction). This can slow down or prevent blood from flowing properly. If the blood vessels that feed the retina constrict, it can cause amaurosis fugax. This condition typically resolves on its own without treatment but can indicate more serious underlying issues.
Scotoma
A scotoma is a blind spot in your visual field where you cannot see normally. Scotomas can appear as light or dark spots or have other visual features. They can affect various parts of your vision, causing partial or total vision loss in those areas.
In meth users, a scotoma could be a sign of an intraretinal hemorrhage. This means the retina has torn, causing bleeding within its layers.
READ MORE: Retinal hemorrhage and retinal bleeding
Cortical blindness
Cortical blindness is a type of vision loss caused by damage to a part of the brain rather than the eye. In meth users, transient cortical blindness could be caused by an ischemic stroke (blockage of blood) or hemorrhagic stroke (bleeding) in the brain. Both can be linked to meth’s vasoconstricting properties.
How meth affects the eyes' appearance
“Meth eyes” is a term sometimes used to describe the appearance of a person’s eyes while they are on meth. This appearance includes dilated pupils and eye redness.
Meth can decrease the eye’s natural blinking reflex, reducing the frequency of blinking. This can contribute to various eye-related issues. The drug can also cause the user’s eyes to move up to 10 times faster than normal due to long-term lack of sleep (typically three to 15 days).
Ocular consequences of long-term methamphetamine use
Using meth for a long period of time can also lead to ocular issues. Some of these are considered emergency situations, requiring immediate medical care. Eye conditions caused by long-term meth use can include:
Vasculitis
Meth’s vasoconstrictive properties can negatively impact blood flow to the eyes. This can create inflammation in the eyes’ blood vessels (vasculitis). This inflammation may arise in the conjunctiva, episclera or sclera.
Keratitis
Keratitis, also referred to as a corneal ulcer, is another potential side effect of chronic (long-term) meth use. Keratitis refers to inflammation in the clear layer at the front of the eye (the cornea). The link between meth and keratitis may be due to:
- Vasoconstriction
- A reduced ability to feel pain
- A reduced blinking reflex
- Eye irritation from smoking
- Contact between the hands and eyes
Some people may develop neurotrophic keratitis, which is characterized by decreased corneal sensations. In turn, this can impede the person’s instinct to blink, which can also slow the healing process. Keratitis can lead to permanent vision loss if not treated properly.
Endophthalmitis
Endophthalmitis occurs when the tissues or fluids (aqueous humor and vitreous humor) inside the eye become infected. It is caused by an infection, typically bacterial or fungal, that has entered from the bloodstream. Endophthalmitis can occur along with meth-induced keratitis.
Pain and decreased vision are two main symptoms of endophthalmitis, although pain is not always present. Other signs and symptoms include:
- Eyelid swelling
- Eye redness
- Light sensitivity (photophobia)
- Eye discharge
- Eye floaters
Endophthalmitis is considered an emergency. It can lead to vision loss and a condition called panophthalmitis.
Panophthalmitis
Panophthalmitis is a severe progression of endophthalmitis that can occur if it is not treated or not treated properly. It involves an infection that spreads throughout the eye and into the surrounding areas. Panopthalmitis is a serious medical emergency and can result in:
- Vision loss
- Loss of the eye
- Additional complications such as meningitis, encephalitis or sepsis
- Cavernous sinus thrombosis (a blood clot behind the eye)
- Stroke
- Death
Retinal vasculitis
Retinal vasculitis refers to inflammation in the retina’s blood vessels. It is typically painless but can cause:
- Vision loss
- Eye floaters
- Scotomas (blind spots)
- Metamorphopsia (visual distortions)
- Changes in color perception
Retinal vasculitis may also occur without symptoms.
Retinopathy
Retinopathy refers to any abnormal change in the retina. These changes can have a number of causes.
Methamphetamine, particularly when taken nasally, has been linked to some types of retinopathy, such as:
- Ischemic retinopathy – Involves reduced blood flow (ischemia) to the retina
- Crystalline retinopathy – Describes deposits of small crystals on or within the retina
Retinopathy can cause vision loss and other concerns.
Angle-closure glaucoma
Glaucoma is a condition that damages the optic nerve. It usually occurs when the pressure in the eye (intraocular pressure) becomes too high. This pressure builds because fluid inside the eye (the aqueous humor) is unable to drain properly. Angle-closure glaucoma occurs when the iris blocks the drainage angle, preventing the aqueous humor from draining as it should. This blockage can be caused by the bulging or swelling of the iris.
The use of crystal meth and inhalable meth has been linked to an increased risk of developing angle-closure glaucoma.
LEARN MORE: Glaucoma causes and risk factors
Keratolysis
Keratolysis, also known as corneal melting, refers to the dissolution of the thickest corneal layer called the stroma. This process can cause corneal ulcerations (sores) and vision loss.
Keratolysis has been linked to both the preparation and the smoking of meth.
Treatment and recovery
Methamphetamine is highly addictive, but help is available. Today, the main treatments are centered around behavioral therapy and contingency management interventions.
Although there are currently no medications to help counteract the addictive effects of meth, research is being conducted in this area. Researchers are also looking into further non-medication-based treatments to help with recovery.
If you or a loved one is struggling with an addiction, please seek help right away.
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