Micropsia
Encyclopedia
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 either optical distortion of images in the eye (as by glasses or certain ocular conditions) or by a neurological dysfunction. The condition of micropsia can be caused by more factors than any other visual distortion
. Factors known to cause micropsia include traumatic brain injury
, swelling of the cornea
, epilepsy, migraine
s, prescription and illicit drug use, retinal edema, macular degeneration
, central serous chorioretinopathy
, brain lesions
, and psychological factors. Dissociative phenomena
are linked with micropsia, which may be the result of brain lateralization
disturbance. Specific types of micropsia include hemimicropsia, a form of micropsia that is localized to one hemisphere of the brain and can be caused by brain lesion
s. Related visual distortion conditions include macropsia
, a less common condition with the reverse effect, and Alice in Wonderland Syndrome
, a condition that has symptoms that can include both micropsia and macropsia.
. It is categorized as an illusion
in the positive phenomena
grouping of abnormal visual distortions.
Convergence-accommodative micropsia
is a physiologic phenomenon in which an object appears smaller as it approaches the subject.
Psychogenic
micropsia can present itself in indiviuals with certain psychiatric disorders.
Retinal micropsia is characterized by an increase in the distance between retinal photoreceptors and is associated with decreased visual acuity
.
Cerebral micropsia is a rare form of micropsia that can arise in children with chronic migraines. Hemimicropsia is a type of cerebral micropsia that occurs within one half of the visual field
.
The majority of individuals with micropsia are aware that their perceptions do not mimic reality. Many can imagine the actual sizes of objects and distances between objects. It is common for patients suffering from micropsia to be able to indicate true size and distance despite their inability to perceive objects as they actually are. One specific patient was able to indicate the dimensions of specific objects with her hands. She was also able to estimate the distances between two objects and between an object and herself. She succeeded in indicating horizontal, vertical, and 45 degree positions and did not find it difficult to search for an object in a cluttered drawer, indicating that her figure-ground discrimination was intact despite suffering from micropsia.
Individuals experiencing hemimicropsia often complain that objects in their left or right visual field appear to be shrunken or compressed. They may also have difficulty appreciating the symmetry of pictures. When drawing, patients often have a tendency to compensate for their perceptual asymmetry by drawing the left or right half of objects slightly larger than the other. In a case of one person with hemimicropsia asked to draw six symmetrical objects, the size of the picture on the left half was on average 16% larger than the corresponding right half.
.
phase of a migraine attack, a phase that often precedes the onset of a headache and is commonly characterized by visual disturbances. Micropsia, along with hemianopsia
, quadrantopsia, scotoma
, phosphene
, teicopsia, metamorphopsia, macropsia, teleopsia, diplopia
, dischromatopsia, and hallucination
disturbances, is a type of aura that occurs immediately before or during the onset of a migraine headache. The symptom usually occurs less than thirty minutes before the migraine headache begins and lasts for five to twenty minutes. Only 10-20% of children with migraine headaches experience auras. Visual auras such as micropsia are most common in children with migraines.
seizures. These seizures affect the entire visual field of the patient. More rarely, micropsia can be part of purely visual seizures. This in turn only affects one half of the visual field and is accompanied by other cerebral visual disturbances. The most common cause of seizures which produce perceptual disturbances such as micropsia and macropsia is medial temporal lobe epilepsy
in which the seizures originate in the amygdala
-hippocampus
complex. Micropsia often occurs as an aura
signalling a seizure in patients with medial temporal lobe epilepsy. Most auras last for a very short period, ranging from a few seconds to a few minutes.
and other hallucinogenic drugs. Although drug-induced changes in perception usually subside as the chemical leaves the body, long-term cocaine
use can result in the chronic residual effect of micropsia. Micropsia can be a symptom of Hallucinogen Persisting Perception Disorder
, or HPPD, in which a person can experience hallucinogenic flashbacks long after ingesting a hallucinogen. A majority of these flashbacks are visual distortions which include micropsia, and 15-80% of hallucinogen users may experience these flashbacks. Micropsia can also be a rare side effect of zolpidem
, a prescription medication used to temporarily treat insomnia.
due to infection by the Epstein-Barr virus
(EBV) and can therefore present as an initial symptom of EBV mononucleosis
, a disease caused by Epstein-Barr virus infection.
. After surgery, patients may experience micropsia as a result of larger photoreceptor separation by edematous fluid.
, an oval-shaped yellow spot near the center of the retina in the human eye. The main factors leading to this disease are age, smoking, heredity, and obesity. Some studies show that consuming spinach or collard greens five times a week cuts the risk of macular degeneration by 43%.
is a disease in which a serous
detachment of the neurosensory retina
occurs over an area of leakage from the choriocapillaris through the retinal pigment epithelium (RPE). The most common symptoms that result from the disease are a deterioration of visual acuity and micropsia.
s. The damaged side of the brain conveys size information that contradicts the size information conveyed by the other side of the brain. This causes a contradiction to arise between the true perception of an object's size and the smaller perception of the object, and micropsic bias ultimately causes the individual to experience micropsia. Lesions affecting other parts of the extracerebral visual pathways can also cause micropsia.
testing can diagnose patients with medial temporal lobe epilepsy
. Epileptiform abnormalities including spikes and sharp waves in the medial temporal lobe
of the brain
can diagnose this condition, which can in turn be the cause of an epileptic
patient's micropsia.
The Amsler grid test
can be used to diagnose macular degeneration
. For this test, patients are asked to look at a grid, and distortions or blank spots in the patient's central field of vision can be detected. A positive diagnosis of macular degeneration may account for a patient's micropsia.
A controlled size comparison task can be employed to evaluate objectively whether a person is experiencing hemimicropsia. For each trial, a pair of horizontally aligned circles is presented on a computer screen, and the person being tested is asked to decide which circle is larger. After a set of trials, the overall pattern of responses should display a normal distance effect where the more similar the two circles, the higher the number of errors. This test is able to effectively diagnose micropsia and confirm which hemisphere is being distorted.
Due to the large range of causes that lead to micropsia, diagnosis varies among cases. Computed tomography
(CT) and magnetic resonance imaging
(MRI) may find lesions and hypodense areas in the temporal and occipital lobes. MRI and CT techniques are able to rule out lesions as the cause for micropsia, but are not sufficient to diagnose the most common causes.
Treatments involving the occlusion of one eye and the use of a prism fitted over an eyeglass lens have both been shown to provide relief from micropsia.
Micropsia that is induced by macular degeneration
can be treated in several ways. A study called AREDS
(age-related eye disease study) determined that taking dietary supplements containing high-dose antioxidants and zinc produced significant benefits with regard to disease progression. This study was the first ever to prove that dietary supplements can alter the natural progression and complications of a disease state. Laser treatments also look promising but are still in clinical stages.
10-35% of migraine sufferers experience auras, with 88% of these patients experiencing both visual auras (which include micropsia) and neurological auras.
Micropsia seems to be slightly more common in boys than in girls among children who experience migraines.
Approximately 80% of temporal lobe seizures produce auras that may lead to micropsia or macropsia. They are a common feature of simple partial seizures and usually precede complex partial seizures of temporal lobe origin.
Central Serous Chorioretinopathy (CSCR) which can produce micropsia predominantly affects persons between the ages of 20 and 50. Women appear to be affected more than men by a factor of almost 3 to 1.
, a neurological condition associated with both micropsia and macropsia, is named after Lewis Carroll's famous 19th century novel Alice's Adventures in Wonderland
. In the story, the title character, Alice, experiences numerous situations similar to those of micropsia and macropsia. Speculation has arisen that Carroll may have written the story using his own direct experience with episodes of micropsia resulting from the numerous migraines he was known to suffer from. It has also been suggested that Carroll may have suffered from temporal lobe epilepsy
.
Micropsia has also been related to Jonathan Swift's
novel Gulliver's Travels
. It has been referred to as "Lilliput sight" and "Lilliputian hallucination," a term coined by British physician Raoul Leroy in 1909, based on the small people that inhabited the island of Lilliput
in the novel.
Current research is being done on macular degeneration which could help prevent cases of micropsia. A variety of drugs that block vascular endothelial growth factor
s (VEGFs) are being evaluated as a treatment option. These treatments for the first time have produced actual improvements in vision, rather than simply delaying or arresting the continued loss of vision characteristic of macular degeneration. A number of surgical treatments are also being investigated for macular degeneration lesions that may not qualify for laser treatment, including macular translocation to a healthier area of the eye, displacement of submacular blood using gas, and removing membranes by surgery.
Visual perception
Visual perception is the ability to interpret information and surroundings from the effects of visible light reaching the eye. The resulting perception is also known as eyesight, sight, or vision...
in which objects are perceived to be smaller than they actually are. Micropsia can be caused by either optical distortion of images in the eye (as by glasses or certain ocular conditions) or by a neurological dysfunction. The condition of micropsia can be caused by more factors than any other visual distortion
Hallucination
A hallucination, in the broadest sense of the word, is a perception in the absence of a stimulus. In a stricter sense, hallucinations are defined as perceptions in a conscious and awake state in the absence of external stimuli which have qualities of real perception, in that they are vivid,...
. Factors known to cause micropsia include traumatic brain injury
Traumatic brain injury
Traumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features...
, swelling of the cornea
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...
, epilepsy, migraine
Migraine
Migraine is a chronic neurological disorder characterized by moderate to severe headaches, and nausea...
s, prescription and illicit drug use, retinal edema, macular degeneration
Macular degeneration
Age-related macular degeneration is a medical condition which usually affects older adults and results in a loss of vision in the center of the visual field because of damage to the retina. It occurs in “dry” and “wet” forms. It is a major cause of blindness and visual impairment in older adults...
, central serous chorioretinopathy
Central serous retinopathy
Central serous retinopathy , also known as central serous chorioretinopathy , is an eye disease which causes visual impairment, often temporary, usually in one eye, mostly affecting males in the age group 20 to 50 but which may also affect women...
, brain lesions
Lesion
A lesion is any abnormality in the tissue of an organism , usually caused by disease or trauma. Lesion is derived from the Latin word laesio which means injury.- Types :...
, and psychological factors. Dissociative phenomena
Dissociation
Dissociation is an altered state of consciousness characterized by partial or complete disruption of the normal integration of a person’s normal conscious or psychological functioning. Dissociation is most commonly experienced as a subjective perception of one's consciousness being detached from...
are linked with micropsia, which may be the result of brain lateralization
Lateralization of brain function
A longitudinal fissure separates the human brain into two distinct cerebral hemispheres, connected by the corpus callosum. The sides resemble each other and each hemisphere's structure is generally mirrored by the other side. Yet despite the strong anatomical similarities, the functions of each...
disturbance. Specific types of micropsia include hemimicropsia, a form of micropsia that is localized to one hemisphere of the brain and can be caused by brain lesion
Lesion
A lesion is any abnormality in the tissue of an organism , usually caused by disease or trauma. Lesion is derived from the Latin word laesio which means injury.- Types :...
s. Related visual distortion conditions include macropsia
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 subject to feel smaller. Macropsia, along with its opposite condition, micropsia, can be categorized under dysmetropsia...
, a less common condition with the reverse effect, and Alice in Wonderland Syndrome
Alice in Wonderland syndrome
Alice-in-Wonderland syndrome , also known as Todd's syndrome, is a disorienting neurological condition that affects human perception. Sufferers may experience micropsia, macropsia, or size distortion of other sensory modalities...
, a condition that has symptoms that can include both micropsia and macropsia.
Definition
Micropsia is the most common visual distortion, or dysmetropsiaDysmetropsia
Dysmetropsia is the group of visual illusions involving an alteration in the size or separation of visual objects. The four common dysmetropsias are: macropsia, micropsia, pelopsia and teleopsia....
. It is categorized as an illusion
Illusion
An illusion is a distortion of the senses, revealing how the brain normally organizes and interprets sensory stimulation. While illusions distort reality, they are generally shared by most people....
in the positive phenomena
Positive visual phenomena
- Definition :Lesions in the visual pathway affect vision most often by creating deficits or negative phenomena, such as blindness, visual field deficits or scotomas, decreased visual acuity and color blindness. On occasion, they may also create false visual images, called positive visual phenomena...
grouping of abnormal visual distortions.
Convergence-accommodative micropsia
Convergence micropsia
Convergence micropsia is a type of micropsia characterized by the reduction in apparent size of objects viewed when the eyes are more converged than they need to be for the distance of the object from the eyes....
is a physiologic phenomenon in which an object appears smaller as it approaches the subject.
Psychogenic
Psychogenic disease
A psychogenic disease is a set of symptoms or complaints whose origin likely lies within the complex interactions of the frontal lobes of the brain and the system in which the complaint manifests...
micropsia can present itself in indiviuals with certain psychiatric disorders.
Retinal micropsia is characterized by an increase in the distance between retinal photoreceptors and is associated with decreased visual acuity
Visual acuity
Visual acuity is acuteness or clearness of vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain....
.
Cerebral micropsia is a rare form of micropsia that can arise in children with chronic migraines. Hemimicropsia is a type of cerebral micropsia that occurs within one half of the visual field
Visual field
The term visual field is sometimes used as a synonym to field of view, though they do not designate the same thing. The visual field is the "spatial array of visual sensations available to observation in introspectionist psychological experiments", while 'field of view' "refers to the physical...
.
Signs and symptoms
Micropsia causes affected individuals to perceive objects as being smaller or more distant than they actually are.The majority of individuals with micropsia are aware that their perceptions do not mimic reality. Many can imagine the actual sizes of objects and distances between objects. It is common for patients suffering from micropsia to be able to indicate true size and distance despite their inability to perceive objects as they actually are. One specific patient was able to indicate the dimensions of specific objects with her hands. She was also able to estimate the distances between two objects and between an object and herself. She succeeded in indicating horizontal, vertical, and 45 degree positions and did not find it difficult to search for an object in a cluttered drawer, indicating that her figure-ground discrimination was intact despite suffering from micropsia.
Individuals experiencing hemimicropsia often complain that objects in their left or right visual field appear to be shrunken or compressed. They may also have difficulty appreciating the symmetry of pictures. When drawing, patients often have a tendency to compensate for their perceptual asymmetry by drawing the left or right half of objects slightly larger than the other. In a case of one person with hemimicropsia asked to draw six symmetrical objects, the size of the picture on the left half was on average 16% larger than the corresponding right half.
Differential diagnosis
Of all of the visual distortions, micropsia has the largest variety of etiologiesEtiology
Etiology is the study of causation, or origination. The word is derived from the Greek , aitiologia, "giving a reason for" ....
.
Migraines
Micropsia can occur during the auraAura (symptom)
An aura is a perceptual disturbance experienced by some migraine sufferers before a migraine headache, and the telltale sensation experienced by some people with epilepsy before a seizure. It often manifests as the perception of a strange light, an unpleasant smell or confusing thoughts or...
phase of a migraine attack, a phase that often precedes the onset of a headache and is commonly characterized by visual disturbances. Micropsia, along with hemianopsia
Hemianopsia
Hemianopia, or hemianopsia, is a type of anopsia where the decreased vision or blindness takes place in half the visual field of one or both eyes. In most cases, the visual field loss respects the vertical midline...
, quadrantopsia, scotoma
Scotoma
A scotoma is an area of partial alteration in one's field of vision consisting of a partially diminished or entirely degenerated visual acuity which is surrounded by a field of normal - or relatively well-preserved - vision.Every normal mammalian eye has a scotoma in its field of vision, usually...
, phosphene
Phosphene
A phosphene is a phenomenon characterized by the experience of seeing light without light actually entering the eye. The word phosphene comes from the Greek words phos and phainein...
, teicopsia, metamorphopsia, macropsia, teleopsia, diplopia
Diplopia
Diplopia, commonly known as double vision, is the simultaneous perception of two images of a single object that may be displaced horizontally, vertically, or diagonally in relation to each other...
, dischromatopsia, and hallucination
Hallucination
A hallucination, in the broadest sense of the word, is a perception in the absence of a stimulus. In a stricter sense, hallucinations are defined as perceptions in a conscious and awake state in the absence of external stimuli which have qualities of real perception, in that they are vivid,...
disturbances, is a type of aura that occurs immediately before or during the onset of a migraine headache. The symptom usually occurs less than thirty minutes before the migraine headache begins and lasts for five to twenty minutes. Only 10-20% of children with migraine headaches experience auras. Visual auras such as micropsia are most common in children with migraines.
Seizures
The most frequent neurological origin of micropsia is a result of temporal lobeTemporal lobe
The temporal lobe is a region of the cerebral cortex that is located beneath the Sylvian fissure on both cerebral hemispheres of the mammalian brain....
seizures. These seizures affect the entire visual field of the patient. More rarely, micropsia can be part of purely visual seizures. This in turn only affects one half of the visual field and is accompanied by other cerebral visual disturbances. The most common cause of seizures which produce perceptual disturbances such as micropsia and macropsia is medial temporal lobe epilepsy
Temporal lobe epilepsy
Temporal lobe epilepsy a.k.a. Psychomotor epilepsy, is a form of focal epilepsy, a chronic neurological condition characterized by recurrent seizures. Over 40 types of epilepsies are known. They fall into two main categories: partial-onset epilepsies and generalized-onset epilepsies...
in which the seizures originate in the amygdala
Amygdala
The ' are almond-shaped groups of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans. Shown in research to perform a primary role in the processing and memory of emotional reactions, the amygdalae are considered part of the limbic system.-...
-hippocampus
Hippocampus
The hippocampus is a major component of the brains of humans and other vertebrates. It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation. Humans and other mammals have two hippocampi, one in...
complex. Micropsia often occurs as an aura
Aura (symptom)
An aura is a perceptual disturbance experienced by some migraine sufferers before a migraine headache, and the telltale sensation experienced by some people with epilepsy before a seizure. It often manifests as the perception of a strange light, an unpleasant smell or confusing thoughts or...
signalling a seizure in patients with medial temporal lobe epilepsy. Most auras last for a very short period, ranging from a few seconds to a few minutes.
Drug use
Micropsia can result from the action of mescalineMescaline
Mescaline or 3,4,5-trimethoxyphenethylamine is a naturally occurring psychedelic alkaloid of the phenethylamine class used mainly as an entheogen....
and other hallucinogenic drugs. Although drug-induced changes in perception usually subside as the chemical leaves the body, long-term cocaine
Cocaine
Cocaine is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. The name comes from "coca" in addition to the alkaloid suffix -ine, forming cocaine. It is a stimulant of the central nervous system, an appetite suppressant, and a topical anesthetic...
use can result in the chronic residual effect of micropsia. Micropsia can be a symptom of Hallucinogen Persisting Perception Disorder
Hallucinogen persisting perception disorder
Hallucinogen persisting perception disorder is a disorder characterized by a continual presence of visual disturbances that are reminiscent of those generated by the ingestion of hallucinogenic substances. Previous use of hallucinogens by the person is needed, though not sufficient, for...
, or HPPD, in which a person can experience hallucinogenic flashbacks long after ingesting a hallucinogen. A majority of these flashbacks are visual distortions which include micropsia, and 15-80% of hallucinogen users may experience these flashbacks. Micropsia can also be a rare side effect of zolpidem
Zolpidem
Zolpidem is a prescription medication used for the short-term treatment of insomnia, as well as some brain disorders. It is a short-acting nonbenzodiazepine hypnotic of the imidazopyridine class that potentiates gamma-aminobutyric acid , an inhibitory neurotransmitter, by binding to GABAA...
, a prescription medication used to temporarily treat insomnia.
Psychological factors
Psychiatric patients may experience micropsia in an attempt to distance themselves from situations involving conflict. Micropsia may also be a symptom of psychological conditions in which patients visualize people as small objects as a way to control others in response to their insecurities and feelings of weakness. In some adults who experienced loneliness as children, micropsia may arise as a mirror of prior feelings of separation from people and objects.Epstein-Barr virus infection
Micropsia can be caused by swelling of the corneaCornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...
due to infection by the Epstein-Barr virus
Epstein-Barr virus
The Epstein–Barr virus , also called human herpesvirus 4 , is a virus of the herpes family and is one of the most common viruses in humans. It is best known as the cause of infectious mononucleosis...
(EBV) and can therefore present as an initial symptom of EBV mononucleosis
Infectious mononucleosis
Infectious mononucleosis is an infectious, widespread viral...
, a disease caused by Epstein-Barr virus infection.
Retinal edema
Micropsia can result from retinal edema causing a dislocation of the receptor cells. Photoreceptor misalignment seems to occur following the surgical re-attachment for macula-off rhegmatogenous retinal detachmentRetinal detachment
Retinal detachment is a disorder of the eye in which the retina peels away from its underlying layer of support tissue. Initial detachment may be localized, but without rapid treatment the entire retina may detach, leading to vision loss and blindness. It is a medical emergency.The retina is a...
. After surgery, patients may experience micropsia as a result of larger photoreceptor separation by edematous fluid.
Macular degeneration
Macular degeneration typically produces micropsia due to the swelling or bulging of the maculaMacula
The macula or macula lutea is an oval-shaped highly pigmented yellow spot near the center of the retina of the human eye. It has a diameter of around 5 mm and is often histologically defined as having two or more layers of ganglion cells...
, an oval-shaped yellow spot near the center of the retina in the human eye. The main factors leading to this disease are age, smoking, heredity, and obesity. Some studies show that consuming spinach or collard greens five times a week cuts the risk of macular degeneration by 43%.
Central serous chorioretinopathy
CSCRCentral serous retinopathy
Central serous retinopathy , also known as central serous chorioretinopathy , is an eye disease which causes visual impairment, often temporary, usually in one eye, mostly affecting males in the age group 20 to 50 but which may also affect women...
is a disease in which a serous
Serous fluid
In physiology, the term serous fluid is used for various bodily fluids that are typically pale yellow and transparent, and of a benign nature, that fill the inside of body cavities. Serous fluid originates from serous glands, with secretions enriched with proteins and water. Serous fluid may also...
detachment of the neurosensory retina
Retina
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...
occurs over an area of leakage from the choriocapillaris through the retinal pigment epithelium (RPE). The most common symptoms that result from the disease are a deterioration of visual acuity and micropsia.
Brain lesions
Micropsia is sometimes seen in individuals with brain infarctionInfarction
In medicine, infarction refers to tissue death that is caused by a local lack of oxygen due to obstruction of the tissue's blood supply. The resulting lesion is referred to as an infarct.-Causes:...
s. The damaged side of the brain conveys size information that contradicts the size information conveyed by the other side of the brain. This causes a contradiction to arise between the true perception of an object's size and the smaller perception of the object, and micropsic bias ultimately causes the individual to experience micropsia. Lesions affecting other parts of the extracerebral visual pathways can also cause micropsia.
Diagnosis approach
EEGElectroencephalography
Electroencephalography is the recording of electrical activity along the scalp. EEG measures voltage fluctuations resulting from ionic current flows within the neurons of the brain...
testing can diagnose patients with medial temporal lobe epilepsy
Temporal lobe epilepsy
Temporal lobe epilepsy a.k.a. Psychomotor epilepsy, is a form of focal epilepsy, a chronic neurological condition characterized by recurrent seizures. Over 40 types of epilepsies are known. They fall into two main categories: partial-onset epilepsies and generalized-onset epilepsies...
. Epileptiform abnormalities including spikes and sharp waves in the medial temporal lobe
Temporal lobe
The temporal lobe is a region of the cerebral cortex that is located beneath the Sylvian fissure on both cerebral hemispheres of the mammalian brain....
of the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
can diagnose this condition, which can in turn be the cause of an epileptic
Epilepsy
Epilepsy is a common chronic neurological disorder characterized by seizures. These seizures are transient signs and/or symptoms of abnormal, excessive or hypersynchronous neuronal activity in the brain.About 50 million people worldwide have epilepsy, and nearly two out of every three new cases...
patient's micropsia.
The Amsler grid test
Amsler grid
The Amsler grid, used since 1945, is a grid of horizontal and vertical lines used to monitor a person's central visual field. The grid was developed by Marc Amsler, a Swiss ophthalmologist. It is a diagnostic tool that aids in the detection of visual disturbances caused by changes in the retina,...
can be used to diagnose macular degeneration
Macular degeneration
Age-related macular degeneration is a medical condition which usually affects older adults and results in a loss of vision in the center of the visual field because of damage to the retina. It occurs in “dry” and “wet” forms. It is a major cause of blindness and visual impairment in older adults...
. For this test, patients are asked to look at a grid, and distortions or blank spots in the patient's central field of vision can be detected. A positive diagnosis of macular degeneration may account for a patient's micropsia.
A controlled size comparison task can be employed to evaluate objectively whether a person is experiencing hemimicropsia. For each trial, a pair of horizontally aligned circles is presented on a computer screen, and the person being tested is asked to decide which circle is larger. After a set of trials, the overall pattern of responses should display a normal distance effect where the more similar the two circles, the higher the number of errors. This test is able to effectively diagnose micropsia and confirm which hemisphere is being distorted.
Due to the large range of causes that lead to micropsia, diagnosis varies among cases. Computed tomography
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
(CT) and magnetic resonance imaging
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
(MRI) may find lesions and hypodense areas in the temporal and occipital lobes. MRI and CT techniques are able to rule out lesions as the cause for micropsia, but are not sufficient to diagnose the most common causes.
Treatment
Treatment varies for micropsia due to the large number of different causes for the condition.Treatments involving the occlusion of one eye and the use of a prism fitted over an eyeglass lens have both been shown to provide relief from micropsia.
Micropsia that is induced by macular degeneration
Macular degeneration
Age-related macular degeneration is a medical condition which usually affects older adults and results in a loss of vision in the center of the visual field because of damage to the retina. It occurs in “dry” and “wet” forms. It is a major cause of blindness and visual impairment in older adults...
can be treated in several ways. A study called AREDS
Age-Related Eye Disease Study
The Age-Related Eye Disease Study was a clinical trial sponsored by the National Eye Institute, one of the National Institutes of Health in the United States...
(age-related eye disease study) determined that taking dietary supplements containing high-dose antioxidants and zinc produced significant benefits with regard to disease progression. This study was the first ever to prove that dietary supplements can alter the natural progression and complications of a disease state. Laser treatments also look promising but are still in clinical stages.
Epidemiology
Episodes of micropsia or macropsia occur in 9% of adolescents.10-35% of migraine sufferers experience auras, with 88% of these patients experiencing both visual auras (which include micropsia) and neurological auras.
Micropsia seems to be slightly more common in boys than in girls among children who experience migraines.
Approximately 80% of temporal lobe seizures produce auras that may lead to micropsia or macropsia. They are a common feature of simple partial seizures and usually precede complex partial seizures of temporal lobe origin.
Central Serous Chorioretinopathy (CSCR) which can produce micropsia predominantly affects persons between the ages of 20 and 50. Women appear to be affected more than men by a factor of almost 3 to 1.
Society and culture
Alice in Wonderland SyndromeAlice in Wonderland syndrome
Alice-in-Wonderland syndrome , also known as Todd's syndrome, is a disorienting neurological condition that affects human perception. Sufferers may experience micropsia, macropsia, or size distortion of other sensory modalities...
, a neurological condition associated with both micropsia and macropsia, is named after Lewis Carroll's famous 19th century novel Alice's Adventures in Wonderland
Alice's Adventures in Wonderland
Alice's Adventures in Wonderland is an 1865 novel written by English author Charles Lutwidge Dodgson under the pseudonym Lewis Carroll. It tells of a girl named Alice who falls down a rabbit hole into a fantasy world populated by peculiar, anthropomorphic creatures...
. In the story, the title character, Alice, experiences numerous situations similar to those of micropsia and macropsia. Speculation has arisen that Carroll may have written the story using his own direct experience with episodes of micropsia resulting from the numerous migraines he was known to suffer from. It has also been suggested that Carroll may have suffered from temporal lobe epilepsy
Temporal lobe epilepsy
Temporal lobe epilepsy a.k.a. Psychomotor epilepsy, is a form of focal epilepsy, a chronic neurological condition characterized by recurrent seizures. Over 40 types of epilepsies are known. They fall into two main categories: partial-onset epilepsies and generalized-onset epilepsies...
.
Micropsia has also been related to Jonathan Swift's
Jonathan Swift
Jonathan Swift was an Irish satirist, essayist, political pamphleteer , poet and cleric who became Dean of St...
novel Gulliver's Travels
Gulliver's Travels
Travels into Several Remote Nations of the World, in Four Parts. By Lemuel Gulliver, First a Surgeon, and then a Captain of Several Ships, better known simply as Gulliver's Travels , is a novel by Anglo-Irish writer and clergyman Jonathan Swift that is both a satire on human nature and a parody of...
. It has been referred to as "Lilliput sight" and "Lilliputian hallucination," a term coined by British physician Raoul Leroy in 1909, based on the small people that inhabited the island of Lilliput
Lilliput and Blefuscu
Lilliput and Blefuscu are two fictional island nations that appear in the first part of the 1726 novel Gulliver's Travels by Jonathan Swift. The two islands are neighbors in the South Indian Ocean, separated by a channel eight hundred yards wide. Both are inhabited by tiny people who are about...
in the novel.
Research
Current experimental evidence focuses on the involvement of the occipitotemporal pathway in both the perceptual equivalence of objects across translations of retinal position and also across size modifications. Recent evidence points to this pathway as a mediator for an individual's perception of size. Even further, numerous cases suggest that size perception may be dissociated from other aspects of visual perception such as color and movement. However, more research is called for to correctly relate the condition to defined physiological conditions.Current research is being done on macular degeneration which could help prevent cases of micropsia. A variety of drugs that block vascular endothelial growth factor
Vascular endothelial growth factor
Vascular endothelial growth factor is a signal protein produced by cells that stimulates vasculogenesis and angiogenesis. It is part of the system that restores the oxygen supply to tissues when blood circulation is inadequate....
s (VEGFs) are being evaluated as a treatment option. These treatments for the first time have produced actual improvements in vision, rather than simply delaying or arresting the continued loss of vision characteristic of macular degeneration. A number of surgical treatments are also being investigated for macular degeneration lesions that may not qualify for laser treatment, including macular translocation to a healthier area of the eye, displacement of submacular blood using gas, and removing membranes by surgery.
See also
- Alice in Wonderland syndromeAlice in Wonderland syndromeAlice-in-Wonderland syndrome , also known as Todd's syndrome, is a disorienting neurological condition that affects human perception. Sufferers may experience micropsia, macropsia, or size distortion of other sensory modalities...
- Convergence micropsiaConvergence micropsiaConvergence micropsia is a type of micropsia characterized by the reduction in apparent size of objects viewed when the eyes are more converged than they need to be for the distance of the object from the eyes....
- DysmetropsiaDysmetropsiaDysmetropsia is the group of visual illusions involving an alteration in the size or separation of visual objects. The four common dysmetropsias are: macropsia, micropsia, pelopsia and teleopsia....
- MacropsiaMacropsiaMacropsia 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 subject to feel smaller. Macropsia, along with its opposite condition, micropsia, can be categorized under dysmetropsia...