Illusory palinopsia is a subtype of palinopsia, a visual disturbance defined as the persistence or recurrence of a visual image after the

stimulus A stimulus is something that causes a physiological response. It may refer to: *Stimulation **Stimulus (physiology), something external that influences an activity **Stimulus (psychology), a concept in behaviorism and perception *Stimulus (economi ...

has been removed. Palinopsia is a broad term describing a heterogeneous group of symptoms, which is divided into hallucinatory palinopsia and illusory palinopsia. Illusory palinopsia is likely due to sustained awareness of a stimulus and is similar to a

visual illusion Within visual perception, an optical illusion (also called a visual illusion) is an illusion caused by the visual system and characterized by a visual percept that arguably appears to differ from reality. Illusions come in a wide variety; the ...

: the distorted perception of a real external

. Illusory palinopsia is caused by

migraines Migraine (, ) is a common neurological disorder characterized by recurrent headaches. Typically, the associated headache affects one side of the head, is pulsating in nature, may be moderate to severe in intensity, and could last from a few h ...

, hallucinogen persisting perception disorder (HPPD),

prescription drugs A prescription drug (also prescription medication or prescription medicine) is a pharmaceutical drug that legally requires a medical prescription to be dispensed. In contrast, over-the-counter drugs can be obtained without a prescription. The r ...

, and

head trauma A head injury is any injury that results in trauma to the skull or brain. The terms ''traumatic brain injury'' and ''head injury'' are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of inju ...

, but is also sometimes

idiopathic An idiopathic disease is any disease with an unknown cause or mechanism of apparent spontaneous origin. From Greek ἴδιος ''idios'' "one's own" and πάθος ''pathos'' "suffering", ''idiopathy'' means approximately "a disease of its own kin ...

. Illusory palinopsia consists of afterimages that are short-lived or unformed, occur at the same location in the

visual field The visual field is the "spatial array of visual sensations available to observation in introspectionist psychological experiments". Or simply, visual field can be defined as the entire area that can be seen when an eye is fixed straight at a poin ...

as the original stimulus, and are often exposed or exacerbated based on environmental parameters such as stimulus intensity, background contrast, fixation, and movement. Illusory palinopsia symptoms occur continuously or predictably, based on environmental conditions. The term is from Greek: ''palin'' for "again" and ''opsia'' for "seeing".

Signs and symptoms

Illusory palinopsia is often worse with high stimulus intensity and

contrast ratio The contrast ratio (CR) is a property of a display system, defined as the ratio of the luminance of the brightest shade (white) to that of the darkest shade (black) that the system is capable of producing. A high contrast ratio is a desired aspect ...

in a dark adapted state. Multiple types of illusory palinopsia often co-exist in a patient and occur with other diffuse, persistent illusory symptoms such as halos around objects, dysmetropsia (

micropsia Micropsia is a condition affecting human visual perception in which objects are perceived to be smaller than they actually are. Micropsia can be caused by optical factors (such as wearing glasses), by distortion of images in the eye (such as optica ...

macropsia Macropsia is a neurological condition affecting human visual perception, in which objects within an affected section of the visual field appear larger than normal, causing the person to feel smaller than they actually are. Macropsia, along with its ...

, pelopsia, or teleopsia), Alice in Wonderland Syndrome, visual snow, and oscillopsia. Illusory palinopsia consists of the following four symptom categories.

Prolonged indistinct afterimage

Prolonged indistinct afterimages are unformed and occur at the same location in the

as the original stimulus.

Stimulus A stimulus is something that causes a physiological response. It may refer to: *Stimulation **Stimulus (physiology), something external that influences an activity **Stimulus (psychology), a concept in behaviorism and perception *Stimulus (economi ...

intensity, contrast, and fixation length affects the generation and severity of these perseverated images. For example, after seeing a bright light such as a car headlight or a camera flash, a persistent afterimage remains in the visual field for several minutes. Patients often report

photophobia Photophobia is a medical symptom of abnormal intolerance to visual perception of light. As a medical symptom photophobia is not a morbid fear or phobia, but an experience of discomfort or pain to the eyes due to light exposure or by presence of ...

, which can restrict their ability to perform outdoor activity. The prolonged image or light is typically isochromatic ( positive afterimage) to the original stimulus, but can fade to different colors over time. Afterimages from lights tend to last longer than the indistinct afterimages from other brightly-colored objects. Palinoptic prolonged light afterimages of the complementary color are differentiated from physiological afterimages based on afterimage intensity and duration.

Light streaking

Light streaking describes a comet-like tail which is seen due to motion between a person or a light. The streaking usually persists for several seconds before fading and often occurs with bright lights on a dark background. Patients commonly report of difficulty with night driving since the headlights of oncoming cars cause multiple streaks which obscure vision.

Visual trailing

Visual trailing describes an object in motion leaving frozen copies in its wake. These motion-induced afterimages may be discontinuous such as in a

film reel A reel is an object around which a length of another material (usually long and flexible) is wound for storage (usually hose are wound around a reel). Generally a reel has a cylindrical core (known as a '' spool'') with flanges around the ends ...

or may be blurred together such as in a long-exposure photograph. If discontinuous, the patient also usually reports

akinetopsia Akinetopsia (Greek: a for "without", kine for "to move" and opsia for "seeing"), also known as cerebral akinetopsia or motion blindness, is a term introduced by Semir Zeki to describe an extremely rare neuropsychological disorder, having only been ...

. The perseverated images last a few seconds and are usually identical in color and shape to the original stimulus. Most cases describe visual trails during movement of an object, although there are also reports from the movement of the observer's head or eyes.

Variant image perseveration

There are a few cases of palinopsia with many of the same features as hallucinatory palinopsia ( formed image perseveration) but with some important differences. The formed perseverated image may only last a couple seconds or may be black or translucent. These variants usually lack the realistic clarity of hallucinatory palinopsia, and the generation of the palinoptic images is affected by fixation time, motion, stimulus intensity, or contrast. These variants probably represent an overlap in hallucinatory and illusory palinopsia but are included in illusory palinopsia since they often co-exist with the other illusory symptoms.

Cause

Of the published cases of palinopsia that are idiopathic or attributed to

, HPPD,

, or

, 94% described illusory palinopsia.

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nefazodone Nefazodone, sold formerly under the brand names Serzone, Dutonin, and Nefadar among others, is an atypical antidepressant which was first marketed by Bristol-Myers Squibb (BMS) in 1994 but has since largely been discontinued. BMS withdrew it from ...

mirtazapine Mirtazapine, sold under the brand name Remeron amongst others, is an atypical antidepressant, and as such is used primarily to treat depression. Its effects may take up to four weeks, but can also manifest as early as one to two weeks. It is o ...

topiramate Topiramate, sold under the brand name Topamax among others, is a carbonic anhydrase inhibitor medication used to treat epilepsy and prevent migraines. It has also been used in alcohol dependence. For epilepsy this includes treatment for genera ...

clomiphene Clomifene, also known as clomiphene, is a medication used to treat infertility in women who do not ovulate, including those with polycystic ovary syndrome. Use results in a greater chance of twins. It is taken by mouth once a day, with a cours ...

oral contraceptives Oral contraceptives, abbreviated OCPs, also known as birth control pills, are medications taken by mouth for the purpose of birth control. Female Two types of female oral contraceptive pill, taken once per day, are widely available: * The combi ...

, and

risperidone Risperidone, sold under the brand name Risperdal among others, is an atypical antipsychotic used to treat schizophrenia and bipolar disorder. It is taken either by mouth or by injection (subcutaneous or intramuscular). The injectable versions ...

have been reported to cause illusory palinopsia.

Clomiphene Clomifene, also known as clomiphene, is a medication used to treat infertility in women who do not ovulate, including those with polycystic ovary syndrome. Use results in a greater chance of twins. It is taken by mouth once a day, with a cours ...

and

are the only prescription drugs reported to cause permanent symptoms. HPPD is most common after LSD ingestion, but can occur after any

hallucinogen Hallucinogens are a large, diverse class of psychoactive drugs that can produce altered states of consciousness characterized by major alterations in thought, mood, and perception as well as other changes. Most hallucinogens can be categorize ...

use. HPPD is commonly described in psychiatric literature and illusory palinopsia symptoms are sometimes not defined as palinopsia. It is not clear if there is a relationship between HPPD and the quantity and strength of

doses taken.

Pathophysiology

Illusory palinopsia is a dysfunction in

visual perception Visual perception is the ability to interpret the surrounding environment through photopic vision (daytime vision), color vision, scotopic vision (night vision), and mesopic vision (twilight vision), using light in the visible spectrum ref ...

, presumably related to diffuse neuronal excitability alterations in the

anterior Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek language, Greek roots, describe something in its standard anatomical position. Th ...

and posterior visual pathways. Because of the drugs that cause illusory palinopsia,

5-HT2a receptor The 5-HT2A receptor is a subtype of the 5-HT2 receptor that belongs to the serotonin receptor family and is a G protein-coupled receptor (GPCR). The 5-HT2A receptor is a cell surface receptor, but has several intracellular locations. 5-HT is s ...

excitotoxicity In excitotoxicity, nerve cells suffer damage or death when the levels of otherwise necessary and safe neurotransmitters such as glutamate become pathologically high, resulting in excessive stimulation of receptors. For example, when glutamate ...

or a disruption of

GABAergic In molecular biology and physiology, something is GABAergic or GABAnergic if it pertains to or affects the neurotransmitter GABA. For example, a synapse is GABAergic if it uses GABA as its neurotransmitter, and a GABAergic neuron produces GABA. A ...

transmission have been proposed as possible mechanisms. However, the

neuropharmacology Neuropharmacology is the study of how drugs affect function in the nervous system, and the neural mechanisms through which they influence behavior. There are two main branches of neuropharmacology: behavioral and molecular. Behavioral neuropharmac ...

of the

visual system The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing photoreceptor cells, the optic nerve, the optic tract and the visual cortex) which gives organisms the sense of sight (th ...

is probably too complex to pinpoint the visual disturbances to a single

neurotransmitter A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, any main body part or target cell, may be another neuron, but could also be a gland or muscle cell. Neu ...

neurotransmitter receptor A neurotransmitter receptor (also known as a neuroreceptor) is a membrane receptor protein that is activated by a neurotransmitter. Chemicals on the outside of the cell, such as a neurotransmitter, can bump into the cell's membrane, in which ther ...

. The generation of illusory palinopsia is often dependent on ambient light or motion, and the symptoms could be a pathological exaggeration of normal light perception and

motion perception Motion perception is the process of inferring the speed and direction of elements in a scene based on visual, vestibular and proprioceptive inputs. Although this process appears straightforward to most observers, it has proven to be a difficult ...

mechanisms. Prolonged indistinct afterimages are symptomatically similar to physiological afterimages, and light streaking and visual trailing are symptomatically similar to

motion blur Motion blur is the apparent streaking of moving objects in a photograph or a sequence of frames, such as a film or animation. It results when the image being recorded changes during the recording of a single exposure, due to rapid movement or lo ...

when viewing fast-moving objects.

Light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 t ...

and

are dynamic operations involving processing and

feedback Feedback occurs when outputs of a system are routed back as inputs as part of a chain of cause-and-effect that forms a circuit or loop. The system can then be said to ''feed back'' into itself. The notion of cause-and-effect has to be handled ...

from structures throughout the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...

. A patient frequently has multiple types of diffuse, persistent illusory symptoms which represent dysfunctions in both light and motion perception. Light and motion are processed via different pathways, which suggests that there are diffuse or global excitability alterations in the visual pathway. Faulty

neural adaptation Neural adaptation or sensory adaptation is a gradual decrease over time in the responsiveness of the sensory system to a constant stimulus. It is usually experienced as a change in the stimulus. For example, if a hand is rested on a table, the ta ...

and

between the anterior and posterior visual pathways could cause persistent excitability changes. Movement-related palinopsia could be due to inappropriate or incomplete activation of the motion suppression mechanisms ( visual masking/ backward masking and

corollary discharge In physiology, an efference copy or efferent copy is an internal copy of an outflowing ('' efferent''), movement-producing signal generated by an organism's motor system.Jeannerod, Marc (2003): "Action Monitoring and Forward Control of Movements ...

s) related to visual stability during eye or body movements, which are present in saccadic suppression, blinking,

smooth pursuit In the scientific study of vision, smooth pursuit describes a type of eye movement in which the eyes remain fixated on a moving object. It is one of two ways that visual animals can voluntarily shift gaze, the other being saccadic eye movemen ...

, etc.

Palinopsia in migraineurs

Illusory palinopsia may occur during a migraine aura, as do other diffuse illusory symptoms such as halos around objects, visual snow, dysmetropsia, and oscillopsia. In a rare migraine subtype known as persistent visual aura without infarction, illusory palinopsia symptoms ( prolonged indistinct afterimages, light streaking, and visual trailing) persist after the migraine has abated. Alternatively, up to 10% of all migraineurs report of formed afterimages that only last a couple seconds and do not occur with other illusory symptoms. These momentary afterimages appear at a different location in the visual field than the original stimulus, occur a few times per month, and are affected by external light and motion. ( variant image perseveration). Migraineurs with these momentary afterimages report significantly fewer migraine headaches than migraineurs without these afterimages (4.3 vs. 14.4 attacks/year). These afterimages probably represent an overlap in hallucinatory and illusory palinopsia. Studying these momentary formed afterimages, in relation to alterations in cortical excitability, could advance our understanding of migraine pathogenesis and mechanisms associated with encoding

visual memory Visual memory describes the relationship between perceptual processing and the encoding, storage and retrieval of the resulting neural representations. Visual memory occurs over a broad time range spanning from eye movements to years in order ...

Diagnosis

Palinopsia necessitates a full ophthalmologic and neurologic history and physical exam. There are no clear guidelines on the work-up for illusory palinopsia, but it is not unreasonable to order automated visual field testing and

neuroimaging Neuroimaging is the use of quantitative (computational) techniques to study the structure and function of the central nervous system, developed as an objective way of scientifically studying the healthy human brain in a non-invasive manner. Incr ...

since migraine aura can sometimes mimic seizures or cortical lesions. However, in a young patient without risk factors or other worrisome symptoms or signs (vasculopathy, history of cancer, etc.),

for illusory palinopsia is low-yield but may grant the patient peace of mind. The physical exam and work-up are usually non-contributory in illusory palinopsia. Diagnosing the etiology of illusory palinopsia is often based on the

clinical history The medical history, case history, or anamnesis (from Greek: ἀνά, ''aná'', "open", and μνήσις, ''mnesis'', "memory") of a patient is information gained by a physician by asking specific questions, either to the patient or to other pe ...

. Palinopsia is attributed to a

prescription drug A prescription drug (also prescription medication or prescription medicine) is a pharmaceutical drug that legally requires a medical prescription to be dispensed. In contrast, over-the-counter drugs can be obtained without a prescription. The r ...

if symptoms begin after drug initiation or dose increase. Palinopsia is attributed to

if symptoms begin shortly after the incident. Continuous illusory palinopsia in a migraineur is usually from persistent visual aura. HPPD can occur any time after hallucinogen ingestion and is a

diagnosis of exclusion A diagnosis of exclusion or by exclusion (''per exclusionem'') is a diagnosis of a medical condition reached by a process of elimination, which may be necessary if presence cannot be established with complete confidence from history, examination o ...

in patients with previous hallucinogen use.

Migraines Migraine (, ) is a common neurological disorder characterized by recurrent headaches. Typically, the associated headache affects one side of the head, is pulsating in nature, may be moderate to severe in intensity, and could last from a few h ...

and HPPD are probably the most common causes of palinopsia.

Idiopathic An idiopathic disease is any disease with an unknown cause or mechanism of apparent spontaneous origin. From Greek ἴδιος ''idios'' "one's own" and πάθος ''pathos'' "suffering", ''idiopathy'' means approximately "a disease of its own kin ...

palinopsia may be analogous to the cerebral state in persistent visual aura with non-migraine headache or persistent visual aura without headache. Due to the subjective nature of the symptoms and the lack of organic findings, clinicians may be dismissive of illusory palinopsia, sometimes causing the patient distress. There is considerable evidence in the literature confirming the symptom legitimacy, so validating the patient’s symptoms can help ease anxiety. Unidirectional visual trails or illusory symptoms confined to part of a visual field suggest cortical pathology and necessitate further work-up.

Treatment

There is limited data on treating the visual disturbances associated with HPPD, persistent visual aura, or post-head trauma visual disturbances, and pharmaceutical treatment is empirically-based. It is not clear if the etiology or type of illusory symptom influences treatment efficacy. Since the symptoms are usually benign, treatment is based on the patient’s zeal and willingness to try many different drugs. There are cases which report successful treatment with

clonidine Clonidine, sold under the brand name Catapres among others, is an α2-adrenergic agonist medication used to treat high blood pressure, ADHD, drug withdrawal ( alcohol, opioids, or nicotine), menopausal flushing, diarrhea, spasticity, and c ...

clonazepam Clonazepam, sold under the brand names Klonopin and Rivotril, is a medication used to prevent and treat seizures, panic disorder, anxiety disorders, and the movement disorder known as akathisia. It is a tranquilizer of the benzodiazepine class ...

lamotrigine Lamotrigine, sold under the brand name Lamictal among others, is a medication used to treat epilepsy and stabilize mood in bipolar disorder. For epilepsy, this includes focal seizures, tonic-clonic seizures, and seizures in Lennox-Gastaut sy ...

, nimodipine,

, verapamil, divalproex sodium,

gabapentin Gabapentin, sold under the brand name Neurontin among others, is an anticonvulsant medication primarily used to treat partial seizures and neuropathic pain. It is a first-line medication for the treatment of neuropathic pain caused by diabeti ...

furosemide Furosemide is a loop diuretic medication used to treat fluid build-up due to heart failure, liver scarring, or kidney disease. It may also be used for the treatment of high blood pressure. It can be taken by injection into a vein or by mo ...

, and

acetazolamide Acetazolamide, sold under the trade name Diamox among others, is a medication used to treat glaucoma, epilepsy, altitude sickness, periodic paralysis, idiopathic intracranial hypertension (raised brain pressure of unclear cause), urine alkal ...

, as these drugs have mechanisms that decrease neuronal excitability. However, other patients report treatment failure from the same drugs. Based on the available evidence and side-effect profile, clonidine might be an attractive treatment option. Many patients report improvement from sunglasses. FL-41 tinted lenses may provide additional relief, as they have shown some efficacy in providing relief to visually-sensitive migraineurs.

References

{{Optical illusions Disorders of optic nerve and visual pathways Visual disturbances and blindness Visual perception