What are visual hallucinations?
A visual hallucination is seeing something that is not physically there. It can be simple, where a person sees something like an obscure shape or a flashing light, or complex, where they see an identifiable person or animal.
Visual hallucinations can arise from a variety of factors. For example, they can be caused by psychiatric disorders or neurological conditions that affect the brain. They may also be associated with certain eye conditions and even some medications.
It’s important to visit a health care professional if you experience any type of visual hallucination. They can help determine the cause and provide strategies to prevent or manage this symptom.
Simple vs. complex hallucinations
There are two main types of visual hallucinations — simple and complex.
A simple visual hallucination is generally a momentary event lasting between five and 30 seconds. These types of hallucinations are normally flashes of light or undefined forms that may flicker in and out.
When a person has a complex visual hallucination, they see a lifelike and detailed image that is not really there. Complex hallucinations can sometimes appear "dream-like" and can last from a few seconds to several hours. They may appear to move and can also be accompanied by auditory (sound) or olfactory (smell) hallucinations.
Most common visual hallucinations
Visual hallucinations can take many forms. Examples of common simple visual hallucinations include:
- Flickering light
- Indistinguishable forms with color
- Geometric shapes
- Wavy lines
Complex visual hallucinations often involve seeing:
- People such as family members
- Religious and mythical figures
- Animals
- Flowers and other plants
- Objects
- Places or events
What causes visual hallucinations?
A wide range of conditions and factors can lead to this symptom. However, the primary causes include:
Mental health conditions
Visual hallucinations are strongly associated with certain mental health conditions. For instance, around 33% of people diagnosed with a psychotic disorder experience them.
Mental health conditions that may cause visual hallucinations include:
- Schizophrenia – A psychotic disorder that impacts a person’s thoughts, emotions and behaviors
- Bipolar disorder – A condition that can cause mood imbalances
- Major depressive disorder – A severe form of depression in which symptoms of a psychotic disorder, including visual hallucinations, can occur
- Delirium – A condition that causes a state of confusion or disorientation
Visual hallucinations in mental health conditions such as psychosis and delirium are believed to be caused by an increase in dopamine and other neurotransmitters, which are chemical messengers in the brain. This imbalance can disrupt areas of the brain essential for regulating functions such as emotions and perception.
READ MORE: Schizophrenia and your eyes
Neurological disorders
Neurological disorders are conditions that impact the body's central nervous system. The central nervous system includes the brain, nerves and spinal cord.
Visual hallucinations are common in the following neurological disorders:
- Parkinson's disease – A brain condition affecting muscle control and movement, among other systems in the body
- Alzheimer’s disease – A type of dementia that affects a person’s ability to think, reason and remember
- Dementia with Lewy bodies – A type of dementia caused by abnormal protein deposits in the brain, affecting thought, movement and other body functions
- Epilepsy – A brain disorder that causes seizures
- Migraine disorder – A condition commonly characterized by chronic, severe headaches
- Visual snow – A type of visual hallucination characterized by small flickering dots in the visual field (often compared to television “static”)
Visual hallucinations in neurological disorders are often caused by damage to the brain's occipital lobe. The occipital lobe houses the visual occipital cortex.
The occipital cortex processes visual signals that are collected by the retina (the light-sensing membrane at the back of the eye) and sent to the brain. Damage to the brain can cause neurons in the occipital lobe to think they’re processing vision signals from the eye. Instead, they’re actually doing it on their own, causing visual hallucinations.
READ MORE: The possible link between the eyes and Alzheimer’s disease
Eye and vision issues
Eye conditions that affect the visual pathway between the eyes and the brain can cause someone to experience visual hallucinations. These can include conditions such as:
Optic nerve damage
The optic nerve sends visual information from the retina to the brain to process what you see. Papilledema (swelling of the optic nerve head) and optic neuritis (inflammation of the optic nerve) are eye conditions that can damage the optic nerve. They can cause visual hallucinations by interfering with the stability of the eye’s retinal nerve fibers.
Charles Bonnett syndrome
Charles Bonnet syndrome is a vision-related condition that commonly causes visual hallucinations. It results from vision loss due to another eye condition, where the visual system is no longer able to process new images. Some of these conditions include:
- Age-related macular degeneration (AMD) – A condition affecting central vision
- Glaucoma – A group of eye conditions that damage the optic nerve
- Cataracts – Clouding of the eye’s natural crystalline lens
- Diabetic retinopathy – A condition that damages the blood vessels in the retina
The brain is used to receiving visual information from the eyes. When vision loss disrupts this process, it may create images or recall ones from memory instead, causing visual hallucinations.
Substances and medications
Some recreational substances and medications can cause visual hallucinations. This happens when they disrupt certain chemicals that facilitate communication processes in the brain.
Recreational substances
Recreational drugs known to cause visual hallucinations include:
- Psychedelic drugs (hallucinogens) – Such as lysergic acid diethylamide (LSD), peyote and psilocybin
- Stimulants – Including amphetamines, like methamphetamine and 3,4-methylenedioxymethamphetamine (MDMA), and cocaine
- Opioids – Such as heroin
- Disassociative anesthetics – Such as phencyclidine (PCP) and ketamine
- Cannabis – When consumed in high doses
People experiencing alcohol withdrawal symptoms (delirium tremens) may also have visual hallucinations. Delirium tremens should be treated as an emergency, as alcohol withdrawal syndrome can be fatal.
Other substances can also cause this symptom.
Medications
Although it’s usually rare, visual hallucinations may also be an unintended side effect of certain prescription medications. Some of these include:
- Dopaminergic medications – Used to treat conditions such as Parkinson's disease
- Antidepressant medications – Such as some selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs)
- Psychotropic medications – Used to treat psychiatric and mood disorders
- Anticholinergic medications – Used to treat conditions like Parkinson’s disease, asthma and bladder issues
- Vasocontrictors or vasodilators – Used to treat conditions like high blood pressure, heart conditions and erectile dysfunction
- Antiepileptic medications – Used to treat seizures
READ MORE: How meth affects your vision
Examples of visual hallucinations
When experiencing a visual hallucination, a person may be aware that what they’re seeing is not real. This is known as full insight. Others may believe their hallucination is real, which is referred to as lack of awareness or lack of insight.
For example, a person with a psychotic disorder may have a complex hallucination of an identifiable person. These hallucinations can be very lifelike. It’s not uncommon for people with conditions like schizophrenia to have a lack of insight and believe them to be real.
However, a person who has a migraine with a visual hallucination (typically called a visual aura) usually has insight and understands that what they're seeing is not real. This is because migraine-related hallucinations tend to be in the form of squiggly or flashing lines, shapes and colors instead of real-world objects.
While people with Charles Bonnet syndrome often have formed hallucinations, they almost always have full insight. Many people with the condition do not share that they have hallucinations out of fear of:
- How they will be perceived by others
- Needing to see a psychiatrist
- Facing other undesirable consequences
Diagnosis and treatment options
When a person experiences visual hallucinations, their doctor may first review their health history and conduct a medical exam. They may then perform tests to help determine the cause of the hallucinations. This may include a magnetic resonance imaging (MRI) scan of the brain or an electroencephalogram (EEG), a test used to measure the brain's electrical activity.
Visual hallucinations are often managed by addressing their underlying cause. If a medication is behind the hallucinations, a doctor may suggest stopping or changing it.
In some cases, medication may be prescribed to help control the hallucinations. Other strategies may be suggested to reduce the chance of experiencing this symptom, such as:
- Adjusting indoor lighting
- Eye exercises
- Getting enough rest
Living with visual hallucinations
No matter their primary cause, visual hallucinations can be distracting and troublesome. This can have a negative impact on a person's quality of life. Because of the stigma surrounding hallucinations, sometimes people do not seek help from their doctor.
If you experience visual hallucinations, it’s important to talk to your health care provider to determine what’s causing them. Your doctor can also help you identify coping strategies and find resources such as support groups.
Sharon Peralta also contributed to this article
