Palinopsia
Encyclopedia
Palinopsia is a visual disturbance that causes images to persist to some extent even after their corresponding stimulus has left. These images are known as afterimage
s and occur in persons with normal vision. However, a person with palinopsia experiences them to a significantly greater degree, to the point where they become difficult or impossible to ignore. This often results in mild to severe anxiety
and/or depression
. Palinopsia sometimes appears on its own, but is more often accompanied by other visual disturbances such as visual snow
, and can be attributed to a number of conditions affecting the brain including, but not limited to, medications, seizure disorders, tumors, occiptal lobe or visual pathway lesions, subcortical hemorrhage, and dural arteriovenous malformations.
Both positive and negative afterimages are experienced by those with normal vision. For example, a very fast-moving object will often be perceived as having a trail, as might a point of light, such as a moving hand-held flashlight, in an otherwise unlit room. These are both examples of positive afterimages, or "trails." Lasting negative afterimages can occur after prolonged exposure to an unchanging visual stimulus, due to the "tiring" of cone cells. The canonical example of this uses the color-inverted American flag (see the article on afterimage
s).
For palinopsia sufferers, the effects are largely the same, however the intensity and length of stimulus required to produce a noticeable afterimage is much less. This can apply to both positive and negative afterimages; for example, virtually any moving object will often be accompanied by trails, and negative afterimages can be formed after viewing an object for seconds or less. Furthermore, the afterimages can accumulate if the time between stimuli is shorter than the time it takes for an afterimage to fade.
Palinopsia is thus a condition which mimics normal phenomena, but with far greater intensity. The degree to which the afterimages are amplified can vary over time, in different circumstances (e.g. different amounts of ambient light, levels of stress, amount of sleep, or influence of substances), and from person to person.
l phenomenon, palinopsia is thought to be a brain-related disorder, and not an eye-related disorder. This is likely because palinopsia is most commonly encountered in connection with diseases, drugs or injuries which affect the brain.
In their 2007 article in the Journal of Neuro-Ophthalmology, ME Ritsema and MA Murphy advise that "palinopsia, or perseveration of a previously viewed image, may be caused by drug use or by posterior visual pathway lesions. Most cases of palinopsia due to visual pathway lesions have an associated homonymous hemianopic visual field defect. We report two patients with palinopsia caused by structural lesions of the posterior visual pathway in the absence of visual field defects. Patients with palinopsia should undergo neuroimaging even in the presence of normal visual fields."
In 2002, Hayashi et al. wrote of a "patient who exhibited transient palinopsia and visual hallucinations. Disturbances initially included an auditory component and increasingly were localized to the left visual field. These events occurred during recovery from a right subcortical hematoma with left homonymous hemianopia. Single-photon emission computed tomography (SPECT) demonstrated extensive perilesional hyperperfusion involving parts of the right parietal, temporal, and occipital cortex. Perilesional hyperperfusion disappeared as the visual abnormalities diminished. We believe that excitatory neuronal activation in perilesional cortex during recovery contributed importantly to the transient abnormal perceptions."
In addition to subcortical hemorrhage and posterior pathway lesions being possible underlying conditions for this visual phenomenon, palinopsia also seems to occur in those with dural arterial defects which affect blood flow to the occipital regions of the brain. In their 1999 Neurology paper, Kupersmith et al. describe seven patients with visual disturbances, including palinopsia, which all have dural arteriovenous malformations (DAVMs). They describe that such malformations, if caught early, should be amenable to treatment before irreversible damage or visual field loss should occur through surgical intervention. In such patients, neurological and visual deficit can be correlated to venous hypertension, from incorrect occipital venous emptying.
Although palinopsia refers to a specific type of visual symptom, there are other conditions, such as visual snow
, which often accompany it. Many of these disorders can be loosely described as "overactive vision." As such, the predominate hypothesis states that these and certain other visual disorders may be the result of a lack of inhibitory neural signals in all or part of the visual center of the brain (in particular, the lateral geniculate nucleus
, which is the primary processor of information received from the retina). Due to lack of inhibition, the neurons continue to fire when they otherwise would be suppressed, which results in increased perception of visual activity.
It is important for health care practitioners to be able to differentiate between the visual phenomenon of palinopsia and that described by those experiencing migraine aura. The aura described most often by migraineurs is a Scintillating scotoma
, in which a zig-zag begins from a center of a field and moves outwards to encompass the visual field. Troost and Newton describe features of differentiating migraine headache from AVM (arteriovenous malformations) in a 1975 Journal of Ophthalmology article, to which there follow ups that include how to distinguish migraine visual aura from occipital epilepsy and other brain disorders.
is largely restricted to those affected and their confidants. As such, funding is difficult to come by.
From a practical point of view, studying the causes and treatment of palinopsia presents many challenges to the researcher. Since the condition does not produce effects apparent to an outside observer, animal testing
, is impossible unless more is known about the pathology. If, as is likely, the problem stems from differences at the neuron
al level, cell culture
experiments or animal model
experiments could lead to an understanding of how to induce, and possibly correct, the malfunction. However, characterizing that pathology would be a difficult process, as the option of isolating known dysfunctional neurons from a sufferer would be very difficult, as palinopsia is not fatal (by way of contrast, much of our early knowledge of the pathology in Alzheimer's Disease
was learned by examining the brains of recently deceased Alzheimer's sufferers). Future research, such as advances in MRI technology, or immunofluorescence
experiments, might allow insight into the physiological differences between the visual systems of persons with normal vision and those with palinopsia, without requiring invasive procedures. In addition, advances in knowledge of the brain, particularly in how the brain recycles visual stimuli, might provide an explanation for palinopsia.
s, which are prescribed primarily for their anxiety-reducing
effects, although as they promote uptake of GABA
, an inhibitory neurotransmitter
, they might reduce the overstimulation which has been shown to occur in palinopsia sufferers. However, few if any patients treated with benzodiazapenes report any noticeable, let alone complete, reversal of visual symptoms, and thus treatments for the underlying condition remain unknown.
In some instances, cases resolve themselves after a period of time, though the length of time varies considerably and can be lifelong; in fact what little evidence there is suggests that the condition is lifelong more often than not. Most sufferers seek to adapt to their condition by accepting it as part of normal experience. However, this adaptation is not as easy as it might seem and can take many years.
Afterimage
An afterimage or ghost image or image burn-in is an optical illusion that refers to an image continuing to appear in one's vision after the exposure to the original image has ceased...
s and occur in persons with normal vision. However, a person with palinopsia experiences them to a significantly greater degree, to the point where they become difficult or impossible to ignore. This often results in mild to severe anxiety
Anxiety
Anxiety is a psychological and physiological state characterized by somatic, emotional, cognitive, and behavioral components. The root meaning of the word anxiety is 'to vex or trouble'; in either presence or absence of psychological stress, anxiety can create feelings of fear, worry, uneasiness,...
and/or depression
Depression (mood)
Depression is a state of low mood and aversion to activity that can affect a person's thoughts, behaviour, feelings and physical well-being. Depressed people may feel sad, anxious, empty, hopeless, helpless, worthless, guilty, irritable, or restless...
. Palinopsia sometimes appears on its own, but is more often accompanied by other visual disturbances such as visual snow
Visual snow
Visual snow is a transitory or persisting visual symptom where people see snow or television-like static in parts or the whole of their visual fields, especially against dark backgrounds...
, and can be attributed to a number of conditions affecting the brain including, but not limited to, medications, seizure disorders, tumors, occiptal lobe or visual pathway lesions, subcortical hemorrhage, and dural arteriovenous malformations.
Description
There are two kinds of afterimages. The first kind is of a relatively short duration and is positive, meaning that the color of the afterimage is the same as that of the original image. The other type is a negative afterimage, meaning that the colors of the original image are inverted, which tends to last comparatively longer. The duration of the positive afterimage generally does not depend upon the length of exposure to the original image, while the intensity and duration of the negative afterimage depend on that of the original image. In other words, viewing an image for a longer period of time, or being exposed to a brighter image, can lead to either a longer or more vivid afterimage, or both.Both positive and negative afterimages are experienced by those with normal vision. For example, a very fast-moving object will often be perceived as having a trail, as might a point of light, such as a moving hand-held flashlight, in an otherwise unlit room. These are both examples of positive afterimages, or "trails." Lasting negative afterimages can occur after prolonged exposure to an unchanging visual stimulus, due to the "tiring" of cone cells. The canonical example of this uses the color-inverted American flag (see the article on afterimage
Afterimage
An afterimage or ghost image or image burn-in is an optical illusion that refers to an image continuing to appear in one's vision after the exposure to the original image has ceased...
s).
For palinopsia sufferers, the effects are largely the same, however the intensity and length of stimulus required to produce a noticeable afterimage is much less. This can apply to both positive and negative afterimages; for example, virtually any moving object will often be accompanied by trails, and negative afterimages can be formed after viewing an object for seconds or less. Furthermore, the afterimages can accumulate if the time between stimuli is shorter than the time it takes for an afterimage to fade.
Palinopsia is thus a condition which mimics normal phenomena, but with far greater intensity. The degree to which the afterimages are amplified can vary over time, in different circumstances (e.g. different amounts of ambient light, levels of stress, amount of sleep, or influence of substances), and from person to person.
Pathology
The pathology which leads to palinopsia can occur through several pathways, which makes teasing out the source of a patient's palinopsia difficult. Though normal negative afterimages are generally understood to be a retinaRetina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...
l phenomenon, palinopsia is thought to be a brain-related disorder, and not an eye-related disorder. This is likely because palinopsia is most commonly encountered in connection with diseases, drugs or injuries which affect the brain.
In their 2007 article in the Journal of Neuro-Ophthalmology, ME Ritsema and MA Murphy advise that "palinopsia, or perseveration of a previously viewed image, may be caused by drug use or by posterior visual pathway lesions. Most cases of palinopsia due to visual pathway lesions have an associated homonymous hemianopic visual field defect. We report two patients with palinopsia caused by structural lesions of the posterior visual pathway in the absence of visual field defects. Patients with palinopsia should undergo neuroimaging even in the presence of normal visual fields."
In 2002, Hayashi et al. wrote of a "patient who exhibited transient palinopsia and visual hallucinations. Disturbances initially included an auditory component and increasingly were localized to the left visual field. These events occurred during recovery from a right subcortical hematoma with left homonymous hemianopia. Single-photon emission computed tomography (SPECT) demonstrated extensive perilesional hyperperfusion involving parts of the right parietal, temporal, and occipital cortex. Perilesional hyperperfusion disappeared as the visual abnormalities diminished. We believe that excitatory neuronal activation in perilesional cortex during recovery contributed importantly to the transient abnormal perceptions."
In addition to subcortical hemorrhage and posterior pathway lesions being possible underlying conditions for this visual phenomenon, palinopsia also seems to occur in those with dural arterial defects which affect blood flow to the occipital regions of the brain. In their 1999 Neurology paper, Kupersmith et al. describe seven patients with visual disturbances, including palinopsia, which all have dural arteriovenous malformations (DAVMs). They describe that such malformations, if caught early, should be amenable to treatment before irreversible damage or visual field loss should occur through surgical intervention. In such patients, neurological and visual deficit can be correlated to venous hypertension, from incorrect occipital venous emptying.
Although palinopsia refers to a specific type of visual symptom, there are other conditions, such as visual snow
Visual snow
Visual snow is a transitory or persisting visual symptom where people see snow or television-like static in parts or the whole of their visual fields, especially against dark backgrounds...
, which often accompany it. Many of these disorders can be loosely described as "overactive vision." As such, the predominate hypothesis states that these and certain other visual disorders may be the result of a lack of inhibitory neural signals in all or part of the visual center of the brain (in particular, the lateral geniculate nucleus
Lateral geniculate nucleus
The lateral geniculate nucleus is the primary relay center for visual information received from the retina of the eye. The LGN is found inside the thalamus of the brain....
, which is the primary processor of information received from the retina). Due to lack of inhibition, the neurons continue to fire when they otherwise would be suppressed, which results in increased perception of visual activity.
It is important for health care practitioners to be able to differentiate between the visual phenomenon of palinopsia and that described by those experiencing migraine aura. The aura described most often by migraineurs is a Scintillating scotoma
Scintillating scotoma
Scintillating scotoma is the most common visual aura preceding migraine and was first described by 19th century physician Hubert Airy . It is often confused with ocular migraine which originates in the eyeball or socket.-Presentation:...
, in which a zig-zag begins from a center of a field and moves outwards to encompass the visual field. Troost and Newton describe features of differentiating migraine headache from AVM (arteriovenous malformations) in a 1975 Journal of Ophthalmology article, to which there follow ups that include how to distinguish migraine visual aura from occipital epilepsy and other brain disorders.
Research
Currently research into the causes and treatment of palinopsia is all but nonexistent. Research articles concerning palinopsia, which are relatively rare, most often only document its occurrence, typically as either a reversible or irreversible effect of a prescribed medication or injury. Due to the comparatively few sufferers of the disorder, awarenessAwareness
Awareness is the state or ability to perceive, to feel, or to be conscious of events, objects or sensory patterns. In this level of consciousness, sense data can be confirmed by an observer without necessarily implying understanding. More broadly, it is the state or quality of being aware of...
is largely restricted to those affected and their confidants. As such, funding is difficult to come by.
From a practical point of view, studying the causes and treatment of palinopsia presents many challenges to the researcher. Since the condition does not produce effects apparent to an outside observer, animal testing
Animal model
An animal model is a living, non-human animal used during the research and investigation of human disease, for the purpose of better understanding the disease without the added risk of causing harm to an actual human being during the process...
, is impossible unless more is known about the pathology. If, as is likely, the problem stems from differences at the neuron
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
al level, cell culture
Cell culture
Cell culture is the complex process by which cells are grown under controlled conditions. In practice, the term "cell culture" has come to refer to the culturing of cells derived from singlecellular eukaryotes, especially animal cells. However, there are also cultures of plants, fungi and microbes,...
experiments or animal model
Animal model
An animal model is a living, non-human animal used during the research and investigation of human disease, for the purpose of better understanding the disease without the added risk of causing harm to an actual human being during the process...
experiments could lead to an understanding of how to induce, and possibly correct, the malfunction. However, characterizing that pathology would be a difficult process, as the option of isolating known dysfunctional neurons from a sufferer would be very difficult, as palinopsia is not fatal (by way of contrast, much of our early knowledge of the pathology in Alzheimer's Disease
Alzheimer's disease
Alzheimer's disease also known in medical literature as Alzheimer disease is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death...
was learned by examining the brains of recently deceased Alzheimer's sufferers). Future research, such as advances in MRI technology, or immunofluorescence
Immunofluorescence
Immunofluorescence is a technique used for light microscopy with a fluorescence microscope and is used primarily on biological samples. This technique uses the specificity of antibodies to their antigen to target fluorescent dyes to specific biomolecule targets within a cell, and therefore allows...
experiments, might allow insight into the physiological differences between the visual systems of persons with normal vision and those with palinopsia, without requiring invasive procedures. In addition, advances in knowledge of the brain, particularly in how the brain recycles visual stimuli, might provide an explanation for palinopsia.
Treatment
The treatment for palinopsia largely depends on the root cause for the disorder. If the disorder's root cause is epileptic in nature, anti-epileptic drugs will likely be prescribed. If the root cause of the disorder is due to brain damage, further evaluation by a neurologist is necessary to make informed decisions about treatment path for the patient in question. For those with dural defects, surgery may be required. Some treatments involve benzodiazepineBenzodiazepine
A benzodiazepine is a psychoactive drug whose core chemical structure is the fusion of a benzene ring and a diazepine ring...
s, which are prescribed primarily for their anxiety-reducing
Anxiolytic
An anxiolytic is a drug used for the treatment of anxiety, and its related psychological and physical symptoms...
effects, although as they promote uptake of GABA
Gabâ
Gabâ or gabaa, for the people in many parts of the Philippines), is the concept of a non-human and non-divine, imminent retribution. A sort of negative karma, it is generally seen as an evil effect on a person because of their wrongdoings or transgressions...
, an inhibitory neurotransmitter
Neurotransmitter
Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...
, they might reduce the overstimulation which has been shown to occur in palinopsia sufferers. However, few if any patients treated with benzodiazapenes report any noticeable, let alone complete, reversal of visual symptoms, and thus treatments for the underlying condition remain unknown.
In some instances, cases resolve themselves after a period of time, though the length of time varies considerably and can be lifelong; in fact what little evidence there is suggests that the condition is lifelong more often than not. Most sufferers seek to adapt to their condition by accepting it as part of normal experience. However, this adaptation is not as easy as it might seem and can take many years.
External links
- Eye on Vision Foundation raises funds and awareness for people suffering with visual snow, floaters, and macular degeneration
- The Palinopsia Foundation is dedicated to increasing awareness of palinopsia, to funding research into the causes, prevention and treatments for palinopsia, and to advocating for the needs of individuals with palinopsia and their families.
- A demonstration of negative afterimages. If one stares at the cross, one will see the blank space moving around the circle eventually become a light green dot, due to the persisting negative afterimage of the purple dots.
