The most common visual hallucinations fall into two broad categories: simple ones like flashes of light, geometric patterns, and streaks of color, and complex ones like seeing people, animals, or detailed scenes that aren’t there. Which type you experience depends largely on what’s causing it. Visual hallucinations affect far more people than most realize. Roughly 6 to 15% of the general population reports experiencing them at some point, and in one large survey, about 21.5% of respondents recalled a visual hallucination within the past month alone.
Simple vs. Complex Hallucinations
Simple (or “unformed”) visual hallucinations are the more basic variety: flashes of light, blurs of color, sheets of brightness, or tessellated geometric patterns. They originate in the primary visual processing area at the back of the brain or in sensory structures like the retina itself. Because they arise early in the visual pipeline, they tend to look abstract rather than lifelike.
Complex (or “formed”) hallucinations are far more vivid. People report seeing recognizable figures, small children, animals, faces, or entire scenes playing out in front of them. These come from higher-order visual processing areas in the brain, the regions that normally stitch raw visual data into meaningful images. The distinction matters because it can point a clinician toward where the problem is occurring, whether in the eye, the basic visual cortex, or higher brain areas responsible for recognition and interpretation.
Hallucinations While Falling Asleep
The single most widespread type of visual hallucination is the kind that happens as you’re drifting off to sleep, called a hypnagogic hallucination. Up to 70% of people experience one at least once in their lives. About 86% of these hallucinations are visual, typically brief images of shifting geometric patterns, shapes, light flashes, or what looks like a kaleidoscope. Some people see faces, animals, or human figures instead. They usually last only seconds, have no storyline the way dreams do, and are considered completely normal. A similar phenomenon can happen as you’re waking up. Neither type signals a medical problem on its own.
Vision Loss and Charles Bonnet Syndrome
When the eyes stop sending complete information to the brain, the brain sometimes fills in the gaps on its own. This is Charles Bonnet syndrome, and it produces vivid, complex visual hallucinations in people with significant vision loss. The hallmark feature is that the person knows what they’re seeing isn’t real. They might see detailed faces, miniature people, animals, or intricate patterns, all generated by a brain that’s compensating for missing visual input.
Charles Bonnet syndrome most often develops alongside age-related macular degeneration, but it also occurs with glaucoma, diabetic retinopathy, retinal detachment, and optic nerve damage. The risk rises sharply as vision worsens. Prevalence ranges from under 1% in general eye clinics to nearly 30% in patients with advanced macular degeneration. It typically appears once visual acuity drops below roughly 20/80 or when significant visual field loss occurs. Many people with Charles Bonnet syndrome never mention it to their doctor because they worry it signals dementia or mental illness. It doesn’t.
Parkinson’s Disease and Lewy Body Dementia
Visual hallucinations are one of the defining features of Lewy body dementia, appearing in an estimated 55 to 78% of people with the condition. They’re often detailed and recurrent: people, children, or animals that appear lifelike and may seem to move around the room. These hallucinations are a major clue that helps distinguish Lewy body dementia from Alzheimer’s disease, where visual hallucinations are far less common.
In Parkinson’s disease, visual hallucinations tend to emerge gradually over the course of the illness. Early on, they may be minor, like briefly seeing something move in peripheral vision or misidentifying a shadow as a person (sometimes called “passage” or “presence” hallucinations). Over time, they become more elaborate. The cumulative prevalence exceeds 80%, meaning the vast majority of people with Parkinson’s will experience some form of visual hallucination if they live with the disease long enough. Both the disease itself and the dopamine-boosting medications used to treat it contribute to the risk.
Migraine Aura
About 25 to 30% of people with migraines experience aura, and over 94% of those auras are visual. The classic version is a shimmering, zigzag pattern that looks like the outline of a medieval fortification wall, often called a fortification spectrum. It may start as a small bright spot and gradually spread across the visual field over 5 to 60 minutes. Other people see flickering lights, blind spots edged with sparkle, or wavy distortions.
Interestingly, about 70% of people with visual aura report it starting in their peripheral vision rather than the center, which contradicts the textbook description of aura beginning centrally and spreading outward. Migraine aura is caused by a slow wave of altered electrical activity sweeping across the visual cortex. It’s temporary, reversible, and not a hallucination in the psychiatric sense, but it qualifies as a false visual perception and is one of the most commonly experienced ones.
Schizophrenia and Psychotic Disorders
Auditory hallucinations (hearing voices) dominate the picture in schizophrenia, but visual hallucinations are more common than many people assume. Roughly 25 to 50% of people with schizophrenia experience them, and visual distortions of some kind affect about 60% of cases. The content varies widely: some people see shadowy figures, distorted faces, or objects that change shape. Unlike in Charles Bonnet syndrome, the person often cannot tell the hallucination isn’t real, and the images may carry emotional weight or feel threatening.
This pattern is actually the reverse of what happens in neurological conditions. In disorders like Lewy body dementia and Charles Bonnet syndrome, visual hallucinations dominate and auditory ones are rare. In psychotic disorders, hearing things is far more common than seeing them.
Medications and Substances
A wide range of medications can trigger visual hallucinations as a side effect. The most commonly implicated categories include:
- Dopamine-boosting drugs used for Parkinson’s disease
- Blood pressure medications, particularly beta-blockers and drugs that dilate blood vessels
- Anti-seizure medications and drugs for psychiatric conditions
- Certain antibiotics, especially cephalosporins and sulfa drugs
- Erectile dysfunction medications, which can cause a bluish tinge to vision
Recreational substances like hallucinogens produce visual hallucinations by design, but alcohol withdrawal (delirium tremens) and anticholinergic toxicity are the substance-related causes most likely to bring someone to an emergency room. In delirium tremens, people classically report seeing insects or small animals. Anticholinergic poisoning, whether from medication overdose or certain plants, often produces visual hallucinations alongside confusion, dry skin, and a rapid heartbeat.
What the Brain Is Actually Doing
Visual hallucinations aren’t random glitches. They follow a few predictable patterns in the brain. The first is direct irritation of the visual cortex, as happens during a seizure or migraine. When the basic visual cortex is stimulated, you see simple shapes and lights. When higher visual areas are stimulated, you see faces, objects, or scenes.
The second pattern is a “release” phenomenon. When the brain stops receiving normal visual input, whether from eye disease, optic nerve damage, or even sensory deprivation, the visual cortex becomes spontaneously active and generates images on its own. This is the mechanism behind Charles Bonnet syndrome and likely plays a role in the hallucinations people experience in dark isolation or after prolonged blindfolding.
The third pathway involves the brain’s arousal system. Damage to the brainstem, which regulates wakefulness, can produce vivid visual hallucinations even when the eyes and visual cortex are intact. This explains why hallucinations are common in delirium, sleep deprivation, and certain brainstem strokes. It also explains why the transition between sleep and waking is such a fertile window for false images: the brain’s arousal circuits are in flux, and dream-like visual activity can briefly leak into conscious perception.