Macropsia
Encyclopedia
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
. Macropsia is related to other conditions dealing with visual perception
, such as aniseikonia
and Alice in Wonderland Syndrome (AIWS, also known as Todd’s syndrome). Macropsia has a wide range of causes, from prescription and illicit drugs, to migraines and (rarely) complex partial epilepsy, and to different retinal conditions, such as epiretinal membrane
. Physiologically, retinal macropsia results from the compression of cones in the eye. It is the compression of receptor distribution that results in greater stimulation and thus a larger perceived image of an object.
of macropsia is the presence of exceptionally enlarged objects throughout the visual field. For example, a young girl might see her sister’s books as the same size as her sister. Stemming from this symptom
, someone with macropsia may feel undersized in relation to his or her surrounding environment. Patients with macropsia have also noted the cessation of auditory function prior to the onset of visual hallucination
, indicating possible seizure
either before or after the hallucination. A buzzing sound in the ears has also been reported immediately before macropsia development. Some patients claim that symptoms may be eased if an attempt is made to physically touch the object which appears enormous in size. It is important to note, however, that patients typically remain lucid and alert throughout episodes, being able to recount specific details. A person with macropsia may have no psychiatric conditions. Symptoms caused chemically by drugs such as cannabis
, magic mushrooms, or cocaine
tend to dissipate after the chemical compound has been excreted from the body. Those who acquire macropsia as a symptom of a virus
usually experience complete recovery and restoration of normal vision
.
Dysmetropsia
in one eye, a case of aniseikonia, can present with symptoms such as headaches, asthenopia
, reading difficulties, depth perception
problems, or double vision
. The visual distortion can cause uncorrelated images to stimulate corresponding retinal regions simultaneously impairing fusion of the images. Without suppression of one of the images symptoms from mild poor stereopsis
, binocular diplopia
and intolerable rivalry can occur.
state. There is evidence that those who experience Alice in Wonderland Syndrome
and associated macropsia are able to recount their experiences with thorough detail. There may be no evidence of psychiatric disturbance and, as a result, no psychiatric therapy may be required. Psychological conditions often arise from macropsia, but the general consensus is that they do not cause macropsia. Those afflicted may experience extreme anxiety
both during and after episodes as a result of the overwhelming nature of his or her distorted visual field. Due to the fear and anxiety associated with the condition, those who have previously suffered an episode hesitate to recount the episode, although retain the ability to do so. Psychologically, a person with macropsia may feel separation and dissociation from the outside world and even from immediate family. This feeling of dissociation has mostly been noted in child or adolescent patients. The patient may feel that he or she must unfairly contend with hostile and aggressive forces due to the gigantic nature of the surrounding environment. The defense against said forces is usually expressed verbally. The patient may falsely present an outgoing or flamboyant persona, while remaining fearful of people internally. He or she, in an attempt to balance the size distortion, may try to make others feel small in size through insult or hostile behavior. The psychological impact of macropsia on long time sufferers who have had the condition since childhood may be greater and lead to severe ego-deficiencies. An alternate interpretation of the condition is that macropsia is a response to biophysiological contraction and has no psychological roots. Thus, when a patient reaches for an enlarged object, he or she is overcoming that physiological contraction . However, this theory has been under much scrutiny.
differences between the eyes, retinal receptor distribution, or the cortical processing of the sampled image. The current hypothesis for the occurrence of dysmetropsia
is due to the stretching or compression of the retina
leading to the displacement of receptors. Macropsia arises from a compressed receptor distribution leading to a larger perceived image size and conversely, micropsia
results from stretching of the retina
leading to a more sparse receptor distribution that gives a smaller perceived image size. In the case of macropsia, the greater density of photoreceptor cells leads to greater stimulation making the object seem larger. In some cases, the effects of macropsia have been shown to be field dependent, in that the degree of visual distortion is related to the visual field angle. Non-uniform stretching or compression of the receptor distribution could explain the field dependency of the macrospia. If the compression forces were closer to the fovea the resulting compression would cause a greater amount of macropsia at lower field angles with little effect at higher field angles where the receptor distribution is not as compressed. Alterations in receptor distribution can be the result of epiretinal membrane
, neuroretina detachment and/or re-attachment, or retinoschisis
. Macropsia caused by surgical re-attachment of macula-off rhegmatogenous retinal detachment
is not symmetrical around the fovea
, resulting in differences size changes in the horizontal and vertical meridians. Asymmetry has also been observed with retinoschisis
, in which macropsia generally results in the vertical direction while micropsia presents in the horizontal direction.
resulting in differences in the way the two eyes perceive the size or shape of images, the condition is known as aniseikonia. Aniseikonia is known to be associated with certain retinal
conditions. Epiretinal membrane
has been found to cause metamorphopsia and aniseikonia. Vitreomacular traction caused by the excessive adhesion of vitreous fluid to the retina
is related to aniseikonia due to the separation and compression of photoreceptor cells. Macular edema
and surgical re-attachment for macula-of rhegmatogenous retinal detachment can also cause an increased separation of macular photoreceptor cells resulting in dysmetropsia
. Retinoschisis
is another eye disease that has been shown to cause aniseikonia.
There is evidence that a lesion appearing in the posterior area of the ventral occippitotemporal visual pathway can cause macropsia. This lesion can be due to an ischemic cell death after an acute posterior cerebral infarction.
and citalopram
. Zolpidem is a drug prescribed for insomnia, and although it has proven beneficial effects, there have been numerous reported cases of adverse perceptual reactions. One of these cases discusses an anorexic woman’s episode of macropsia, which occurred twenty minutes after taking 10 mg zolpidem. The same woman later had two more episodes of zolpidem-induced macropsia, after taking 5 mg and 2.5 mg zolpidem, respective to each episode. The intensity of the macropsia episodes decreased with the decreasing amount of zolpidem administered; it is implied in the article that the level of intensity was based on the patients accounts of her macropsia episodes, and that no external diagnosis was used. Hoyler points out notable similarities among the different reported cases of zolpidem-induced disorganization. The similarities were that all the cases were reported by women, the disorganization and agitation followed the first administration of zolpidem, and once zolpidem was discontinued, there were no lasting residual effects. It is believed that zolpidem-related macropsia is more prevalent in women because plasma zolpidem concentration is 40% higher in women, a concentration that further increases in anorexic women.
Citalopram-induced macropsia is similar to zolpidem-induced macropsia since both types have been observed in relatively few cases, and neither of the drugs’ side effects can be supported by experimental evidence. Citalopram is an antidepressant that inhibits serotonin reuptake. The first case of macropsia thought to be induced by citalopram involves a woman who experienced macropsia after her first administration of 10 mg citalopram. Just as with zolpidem, after the immediate discontinuation of citalopram, there were no further episodes of macropsia.
, psilocybin mushrooms (magic mushrooms), and marijuana can cause the user to hallucinate and experience macropsia. There are also suggestions that visual distortions, such as macropsia, can be associated with cocaine use. Episodes of temporary drug-induced macropsia subside as the chemicals leave the body.
. One of these studies was conducted on Japanese adolescents who reported visual episodic illusions with macropsia and showed that illusions are three times more likely to occur in association with migraine. The illusions were most prevalent among girls between the ages of 16 and 18. It is unlikely that macropsia in Japanese adolescents could be due to epileptic seizure since only .3% of Japanese adolescents have epilepsy. No evidence of drugs was found, which eliminates the possibility of the macropsia in the adolescents being drug-induced. It is also unlikely for macropsia in adolescent children to be associated with a serious disease. It is usually the macropsia or other visual disturbance which precedes the painful migrainous headaches. The episodes of macropsia can occur as part of the aura in a migraine
. These episodes are often brief, lasting only a few minutes. Adolescents who are deemed to have multiple distortions per episode, such as slow motion vision and macropsia, are even more likely to be sufferers of migraine. The macropsia episodes associated with migraine are typically equivalent to the duration of the aura, which can range from moments to 15 minutes. Non-migrainous headaches are not known to be associated with episodic illusions. Even in the absence of a migraine, a fever or a hypnagocic state can provoke visual illusions, which one might claim to be macropsia. A person with macropsia may fail to see the connection between the migraine
and the macropsia, since the conditions may not elicit symptoms at the same time. The pathophysiology
of the condition is not fully understood, but the timing of some episodic
occurrences with the headaches suggests that there is a connection between macropsia and the vasoconstrictive phase of a migraine
. The differences in visual phenomena, such as macropsia with slow motion versus macropsia without slow motion, may result from different areas of the brain being affected by migraine
.
and temporal lobe epilepsy
, which may actually help in the diagnosis of those diseases. Children who experience nocturnal hallucinations accompanied by macropsia may seek medical care for panic attack disorders and instead are diagnosed with forms of epilepsy. Epilepsy patients may have no memory of the seizure, but can remember the hallucinations and aura which proceed the attack. Electroencephalography
, or EEG imaging, can then be utilized while the patient experiences the episode. It may be subsequently concluded that the EEG is congruent with temporal or frontal lobe seizure. Anxiety and headaches accompany the episodes of visual distortion associated with epilepsy. Valproic acid
is used to treat the epilepsy, and may be effective in ending the episodes of macropsia
. Macropsia has been observed in experimental hypoglycaemia and in patients receiving insulin therapy.
and infectious mononucleosis
have cited an increase in the sizes of perceived objects, coinciding with other symptoms of Alice in Wonderland Syndrome. Additionally, it has been observed that Epstein-Barr patients who cite hallucinations display abnormal MRI scans. The MRI may show swelling of the cerebral cortex, transient T2 prolongation, and transient lesions. Unlike in MRI's, no abnormalities have been reported in CT
scans. It is thus recommended that an Epstein-Barr patient who cites visual hallucinations have an MRI scan,.Macropsia may appear either before the onset, or after the resolution, of all clinical symptoms associated with the illness. The duration of the disturbances have been shown to range between two weeks and seven months. Almost all patients with macropsia due to infectious mononucleiosis have full recoveries. Patients with Coxsackievirus B1 have reported numerous symptoms of Alice in Wonderland Syndrome, the most common of which being macropsia and micropsia.
test can be used to diagnose macropsia, along with other visual maladies depending on the subjective disturbance reported by the patient after looking at the Amsler Grid
. Outward bulging of the lines on an Amsler Grid is consistent with patients experiencing macropsisa. The New Aniseikonia Test (NAT) can quantify the degree of macropsia or micropsia
independently in the vertical and horizontal meridians. The test consists of red and green semicircles on a black background with a white round fixation target. The size of the red semicircle is held constant while the green semicircle is varied in size in 1% increments. The patient wears a pair of red/green goggles so that one eye is tested at a time, and the patient attempts to determine when the semicircles are the same size. This is termed the reversal threshold and the size difference between the semicircles are reported as the degree of aniseikonia. A positive value indicates that the object was perceived bigger and thus corresponds to macropsia, and conversely a negative value indicates micropsia. The Aniseikonia Inspector contains an aniseikonia test based on the same principles as the NAT, but the test is run on a computer screen, it is based an a forced choice method, and it can measure the size difference as a function of the size of the objects. The functionality of being able to measure the size difference as function of the size (i.e. field depent testing) is especially important when the macropsia (or micropsia) has a retinal origin.
properties of the eyes
. This method includes changing the shape of spectacle lenses, changing the vertex distances with contact lenses, creating a weak telescope
system with contact lenses and spectacles, and changing the power of one of the spectacle lenses. Computer software, such as the Aniseikonia Inspector, has been developed to determine the prescription needed to correct for a certain degree of aniseikonia. The problem with correction through optical means is that the optics do not vary with field angle and thus cannot compensate for non-uniform macropsia. Patients have reported significantly improved visual comfort associated with a correction of 5-10% of the aniseikonia.
With regard to drug-induced or virus-induced macropsia, once the underlying problem, either drug abuse or viral infection, is treated, the induced macropsia ceases.
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 either optical distortion of images in the eye or by a neurological dysfunction. The condition of micropsia can be caused by more factors than...
, can be categorized under dysmetropsia
Dysmetropsia
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....
. Macropsia is related to other conditions dealing with visual perception
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...
, such as aniseikonia
Aniseikonia
Aniseikonia is an ocular condition where there is a significant difference in the perceived size of images. It can occur as an overall difference between the two eyes, or as a difference in a particular meridian.-Causes:Retinal image size is determined by many factors...
and Alice in Wonderland Syndrome (AIWS, also known as Todd’s syndrome). Macropsia has a wide range of causes, from prescription and illicit drugs, to migraines and (rarely) complex partial epilepsy, and to different retinal conditions, such as epiretinal membrane
Epiretinal membrane
Epiretinal membrane is a disease of the eye in response to changes in the vitreous humor or more rarely, diabetes. It is also called macular pucker. Sometimes, as a result of immune system response to protect the retina, cells converge in the macular area as the vitreous ages and pulls away in...
. Physiologically, retinal macropsia results from the compression of cones in the eye. It is the compression of receptor distribution that results in greater stimulation and thus a larger perceived image of an object.
Symptomology
The most obvious symptomSymptom
A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...
of macropsia is the presence of exceptionally enlarged objects throughout the visual field. For example, a young girl might see her sister’s books as the same size as her sister. Stemming from this symptom
Symptom
A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...
, someone with macropsia may feel undersized in relation to his or her surrounding environment. Patients with macropsia have also noted the cessation of auditory function prior to the onset of visual 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,...
, indicating possible seizure
Seizure
An epileptic seizure, occasionally referred to as a fit, is defined as a transient symptom of "abnormal excessive or synchronous neuronal activity in the brain". The outward effect can be as dramatic as a wild thrashing movement or as mild as a brief loss of awareness...
either before or after the hallucination. A buzzing sound in the ears has also been reported immediately before macropsia development. Some patients claim that symptoms may be eased if an attempt is made to physically touch the object which appears enormous in size. It is important to note, however, that patients typically remain lucid and alert throughout episodes, being able to recount specific details. A person with macropsia may have no psychiatric conditions. Symptoms caused chemically by drugs such as cannabis
Cannabis
Cannabis is a genus of flowering plants that includes three putative species, Cannabis sativa, Cannabis indica, and Cannabis ruderalis. These three taxa are indigenous to Central Asia, and South Asia. Cannabis has long been used for fibre , for seed and seed oils, for medicinal purposes, and as a...
, magic mushrooms, or 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...
tend to dissipate after the chemical compound has been excreted from the body. Those who acquire macropsia as a symptom of a virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
usually experience complete recovery and restoration of normal vision
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...
.
Dysmetropsia
Dysmetropsia
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....
in one eye, a case of aniseikonia, can present with symptoms such as headaches, asthenopia
Asthenopia
Asthenopia or eye strain is an ophthalmological condition that manifests itself through nonspecific symptoms such as fatigue, pain in or around the eyes, blurred vision, headache and occasional double vision...
, reading difficulties, depth perception
Depth perception
Depth perception is the visual ability to perceive the world in three dimensions and the distance of an object. Depth sensation is the ability to move accurately, or to respond consistently, based on the distances of objects in an environment....
problems, or double vision
Double vision
Double vision refers to diplopia, the perception of two images from a single object.Double vision may also refer to:- Music :* Double Vision * Double Vision...
. The visual distortion can cause uncorrelated images to stimulate corresponding retinal regions simultaneously impairing fusion of the images. Without suppression of one of the images symptoms from mild poor stereopsis
Stereopsis
Stereopsis refers to impression of depth that is perceived when a scene is viewed with both eyes by someone with normal binocular vision. Binocular viewing of a scene creates two slightly different images of the scene in the two eyes due the the eyes' different positions on the head...
, binocular 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...
and intolerable rivalry can occur.
Psychological effects
There are a broad range of psychological and emotional effects that a person suffering macropsia may experience. One competing theory has radically stated that macropsia may be an entirely psychological pathological phenomenon without any structural defect or definite cause. He or she may be in an irritable or angry state, or in contrast, a euphoricEuphoria
Euphoria is an emotional and mental state defined as a sense of great elation and well being.Euphoria may also refer to:* Euphoria , a genus of scarab beetles* Euphoria, a genus name previously used for the longan and other trees...
state. There is evidence that those who experience 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...
and associated macropsia are able to recount their experiences with thorough detail. There may be no evidence of psychiatric disturbance and, as a result, no psychiatric therapy may be required. Psychological conditions often arise from macropsia, but the general consensus is that they do not cause macropsia. Those afflicted may experience extreme 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,...
both during and after episodes as a result of the overwhelming nature of his or her distorted visual field. Due to the fear and anxiety associated with the condition, those who have previously suffered an episode hesitate to recount the episode, although retain the ability to do so. Psychologically, a person with macropsia may feel separation and dissociation from the outside world and even from immediate family. This feeling of dissociation has mostly been noted in child or adolescent patients. The patient may feel that he or she must unfairly contend with hostile and aggressive forces due to the gigantic nature of the surrounding environment. The defense against said forces is usually expressed verbally. The patient may falsely present an outgoing or flamboyant persona, while remaining fearful of people internally. He or she, in an attempt to balance the size distortion, may try to make others feel small in size through insult or hostile behavior. The psychological impact of macropsia on long time sufferers who have had the condition since childhood may be greater and lead to severe ego-deficiencies. An alternate interpretation of the condition is that macropsia is a response to biophysiological contraction and has no psychological roots. Thus, when a patient reaches for an enlarged object, he or she is overcoming that physiological contraction . However, this theory has been under much scrutiny.
Physiology Behind The Disease
Macropsia may be a result of optical magnificationMagnification
Magnification is the process of enlarging something only in appearance, not in physical size. This enlargement is quantified by a calculated number also called "magnification"...
differences between the eyes, retinal receptor distribution, or the cortical processing of the sampled image. The current hypothesis for the occurrence of dysmetropsia
Dysmetropsia
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....
is due to the stretching or compression of the 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...
leading to the displacement of receptors. Macropsia arises from a compressed receptor distribution leading to a larger perceived image size and conversely, micropsia
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 either optical distortion of images in the eye or by a neurological dysfunction. The condition of micropsia can be caused by more factors than...
results from stretching of the 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...
leading to a more sparse receptor distribution that gives a smaller perceived image size. In the case of macropsia, the greater density of photoreceptor cells leads to greater stimulation making the object seem larger. In some cases, the effects of macropsia have been shown to be field dependent, in that the degree of visual distortion is related to the visual field angle. Non-uniform stretching or compression of the receptor distribution could explain the field dependency of the macrospia. If the compression forces were closer to the fovea the resulting compression would cause a greater amount of macropsia at lower field angles with little effect at higher field angles where the receptor distribution is not as compressed. Alterations in receptor distribution can be the result of epiretinal membrane
Epiretinal membrane
Epiretinal membrane is a disease of the eye in response to changes in the vitreous humor or more rarely, diabetes. It is also called macular pucker. Sometimes, as a result of immune system response to protect the retina, cells converge in the macular area as the vitreous ages and pulls away in...
, neuroretina detachment and/or re-attachment, or retinoschisis
Retinoschisis
Retinoschisis is an eye disease characterized by the abnormal splitting of the retina's neurosensory layers, usually in the outer plexiform layer, resulting in a loss of vision in the corresponding visual field in some rarer forms...
. Macropsia caused by surgical re-attachment of macula-off rhegmatogenous retinal detachment
Retinal 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...
is not symmetrical around the fovea
Fovea
The fovea centralis, also generally known as the fovea , is a part of the eye, located in the center of the macula region of the retina....
, resulting in differences size changes in the horizontal and vertical meridians. Asymmetry has also been observed with retinoschisis
Retinoschisis
Retinoschisis is an eye disease characterized by the abnormal splitting of the retina's neurosensory layers, usually in the outer plexiform layer, resulting in a loss of vision in the corresponding visual field in some rarer forms...
, in which macropsia generally results in the vertical direction while micropsia presents in the horizontal direction.
Structural Defects
In cases where macropsia affects one eyeHuman eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
resulting in differences in the way the two eyes perceive the size or shape of images, the condition is known as aniseikonia. Aniseikonia is known to be associated with certain retinal
Retinal
Retinal, also called retinaldehyde or vitamin A aldehyde, is one of the many forms of vitamin A . Retinal is a polyene chromophore, and bound to proteins called opsins, is the chemical basis of animal vision...
conditions. Epiretinal membrane
Epiretinal membrane
Epiretinal membrane is a disease of the eye in response to changes in the vitreous humor or more rarely, diabetes. It is also called macular pucker. Sometimes, as a result of immune system response to protect the retina, cells converge in the macular area as the vitreous ages and pulls away in...
has been found to cause metamorphopsia and aniseikonia. Vitreomacular traction caused by the excessive adhesion of vitreous fluid to the 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...
is related to aniseikonia due to the separation and compression of photoreceptor cells. Macular edema
Macular edema
Macular edema occurs when fluid and protein deposits collect on or under the macula of the eye and causes it to thicken and swell. The swelling may distort a person's central vision, as the macula is near the center of the retina at the back of the eyeball...
and surgical re-attachment for macula-of rhegmatogenous retinal detachment can also cause an increased separation of macular photoreceptor cells resulting in dysmetropsia
Dysmetropsia
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....
. Retinoschisis
Retinoschisis
Retinoschisis is an eye disease characterized by the abnormal splitting of the retina's neurosensory layers, usually in the outer plexiform layer, resulting in a loss of vision in the corresponding visual field in some rarer forms...
is another eye disease that has been shown to cause aniseikonia.
There is evidence that a lesion appearing in the posterior area of the ventral occippitotemporal visual pathway can cause macropsia. This lesion can be due to an ischemic cell death after an acute posterior cerebral infarction.
Prescription Drugs
The most prevalent research on prescription drugs with side effects of macropsia deals with zolpidemZolpidem
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...
and citalopram
Citalopram
Citalopram brand names: Celexa, Cipramil) is an antidepressant drug of the selective serotonin reuptake inhibitor class. It has U.S...
. Zolpidem is a drug prescribed for insomnia, and although it has proven beneficial effects, there have been numerous reported cases of adverse perceptual reactions. One of these cases discusses an anorexic woman’s episode of macropsia, which occurred twenty minutes after taking 10 mg zolpidem. The same woman later had two more episodes of zolpidem-induced macropsia, after taking 5 mg and 2.5 mg zolpidem, respective to each episode. The intensity of the macropsia episodes decreased with the decreasing amount of zolpidem administered; it is implied in the article that the level of intensity was based on the patients accounts of her macropsia episodes, and that no external diagnosis was used. Hoyler points out notable similarities among the different reported cases of zolpidem-induced disorganization. The similarities were that all the cases were reported by women, the disorganization and agitation followed the first administration of zolpidem, and once zolpidem was discontinued, there were no lasting residual effects. It is believed that zolpidem-related macropsia is more prevalent in women because plasma zolpidem concentration is 40% higher in women, a concentration that further increases in anorexic women.
Citalopram-induced macropsia is similar to zolpidem-induced macropsia since both types have been observed in relatively few cases, and neither of the drugs’ side effects can be supported by experimental evidence. Citalopram is an antidepressant that inhibits serotonin reuptake. The first case of macropsia thought to be induced by citalopram involves a woman who experienced macropsia after her first administration of 10 mg citalopram. Just as with zolpidem, after the immediate discontinuation of citalopram, there were no further episodes of macropsia.
Illicit Drugs
Temporary macropsia can be induced by a number of other illicit drugs. Various psychoactive drugs, such as LSDLSD
Lysergic acid diethylamide, abbreviated LSD or LSD-25, also known as lysergide and colloquially as acid, is a semisynthetic psychedelic drug of the ergoline family, well known for its psychological effects which can include altered thinking processes, closed and open eye visuals, synaesthesia, an...
, psilocybin mushrooms (magic mushrooms), and marijuana can cause the user to hallucinate and experience macropsia. There are also suggestions that visual distortions, such as macropsia, can be associated with cocaine use. Episodes of temporary drug-induced macropsia subside as the chemicals leave the body.
Migraine
Past research has linked macropsia to migraineMigraine
Migraine is a chronic neurological disorder characterized by moderate to severe headaches, and nausea...
. One of these studies was conducted on Japanese adolescents who reported visual episodic illusions with macropsia and showed that illusions are three times more likely to occur in association with migraine. The illusions were most prevalent among girls between the ages of 16 and 18. It is unlikely that macropsia in Japanese adolescents could be due to epileptic seizure since only .3% of Japanese adolescents have epilepsy. No evidence of drugs was found, which eliminates the possibility of the macropsia in the adolescents being drug-induced. It is also unlikely for macropsia in adolescent children to be associated with a serious disease. It is usually the macropsia or other visual disturbance which precedes the painful migrainous headaches. The episodes of macropsia can occur as part of the aura in a migraine
Migraine
Migraine is a chronic neurological disorder characterized by moderate to severe headaches, and nausea...
. These episodes are often brief, lasting only a few minutes. Adolescents who are deemed to have multiple distortions per episode, such as slow motion vision and macropsia, are even more likely to be sufferers of migraine. The macropsia episodes associated with migraine are typically equivalent to the duration of the aura, which can range from moments to 15 minutes. Non-migrainous headaches are not known to be associated with episodic illusions. Even in the absence of a migraine, a fever or a hypnagocic state can provoke visual illusions, which one might claim to be macropsia. A person with macropsia may fail to see the connection between the migraine
Migraine
Migraine is a chronic neurological disorder characterized by moderate to severe headaches, and nausea...
and the macropsia, since the conditions may not elicit symptoms at the same time. The pathophysiology
Pathophysiology
Pathophysiology is the study of the changes of normal mechanical, physical, and biochemical functions, either caused by a disease, or resulting from an abnormal syndrome...
of the condition is not fully understood, but the timing of some episodic
Episodic memory
Episodic memory is the memory of autobiographical events that can be explicitly stated. Semantic and episodic memory together make up the category of declarative memory, which is one of the two major divisions in memory...
occurrences with the headaches suggests that there is a connection between macropsia and the vasoconstrictive phase of a migraine
Migraine
Migraine is a chronic neurological disorder characterized by moderate to severe headaches, and nausea...
. The differences in visual phenomena, such as macropsia with slow motion versus macropsia without slow motion, may result from different areas of the brain being affected by migraine
Migraine
Migraine is a chronic neurological disorder characterized by moderate to severe headaches, and nausea...
.
Epilepsy
Macropsia may present itself as a symptom of both frontal lobe epilepsyFrontal lobe epilepsy
Frontal lobe epilepsy, or FLE, is a neurological disorder that is characterized by brief, recurring seizures that arise in the frontal lobes of the brain, often while the patient is sleeping...
and 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...
, which may actually help in the diagnosis of those diseases. Children who experience nocturnal hallucinations accompanied by macropsia may seek medical care for panic attack disorders and instead are diagnosed with forms of epilepsy. Epilepsy patients may have no memory of the seizure, but can remember the hallucinations and aura which proceed the attack. Electroencephalography
Electroencephalography
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...
, or EEG imaging, can then be utilized while the patient experiences the episode. It may be subsequently concluded that the EEG is congruent with temporal or frontal lobe seizure. Anxiety and headaches accompany the episodes of visual distortion associated with epilepsy. Valproic acid
Valproic acid
Valproic acid is a chemical compound that has found clinical use as an anticonvulsant and mood-stabilizing drug, primarily in the treatment of epilepsy, bipolar disorder, and, less commonly, major depression. It is also used to treat migraine headaches and schizophrenia...
is used to treat the epilepsy, and may be effective in ending the episodes of macropsia
Hypoglycaemia
Endogenous hypoglycaemia can result in number of visual disturbances and sometimes macropsia. This kind of hypoglycaemia is defined as having an abnormally low blood-sugar level due to anything other than the exogenous administration of insulinInsulin
Insulin is a hormone central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle....
. Macropsia has been observed in experimental hypoglycaemia and in patients receiving insulin therapy.
Viruses
Patients with both Epstein-Barr virusEpstein-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...
and infectious mononucleosis
Infectious mononucleosis
Infectious mononucleosis is an infectious, widespread viral...
have cited an increase in the sizes of perceived objects, coinciding with other symptoms of Alice in Wonderland Syndrome. Additionally, it has been observed that Epstein-Barr patients who cite hallucinations display abnormal MRI scans. The MRI may show swelling of the cerebral cortex, transient T2 prolongation, and transient lesions. Unlike in MRI's, no abnormalities have been reported in CT
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
scans. It is thus recommended that an Epstein-Barr patient who cites visual hallucinations have an MRI scan,.Macropsia may appear either before the onset, or after the resolution, of all clinical symptoms associated with the illness. The duration of the disturbances have been shown to range between two weeks and seven months. Almost all patients with macropsia due to infectious mononucleiosis have full recoveries. Patients with Coxsackievirus B1 have reported numerous symptoms of Alice in Wonderland Syndrome, the most common of which being macropsia and micropsia.
Diagnosis
Macropsia is generally diagnosed once a patient complains of the characteristic symptoms, such as disproportionally large objects in their visual field. The Amsler GridAmsler 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,...
test can be used to diagnose macropsia, along with other visual maladies depending on the subjective disturbance reported by the patient after looking at the Amsler Grid
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,...
. Outward bulging of the lines on an Amsler Grid is consistent with patients experiencing macropsisa. The New Aniseikonia Test (NAT) can quantify the degree of macropsia or micropsia
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 either optical distortion of images in the eye or by a neurological dysfunction. The condition of micropsia can be caused by more factors than...
independently in the vertical and horizontal meridians. The test consists of red and green semicircles on a black background with a white round fixation target. The size of the red semicircle is held constant while the green semicircle is varied in size in 1% increments. The patient wears a pair of red/green goggles so that one eye is tested at a time, and the patient attempts to determine when the semicircles are the same size. This is termed the reversal threshold and the size difference between the semicircles are reported as the degree of aniseikonia. A positive value indicates that the object was perceived bigger and thus corresponds to macropsia, and conversely a negative value indicates micropsia. The Aniseikonia Inspector contains an aniseikonia test based on the same principles as the NAT, but the test is run on a computer screen, it is based an a forced choice method, and it can measure the size difference as a function of the size of the objects. The functionality of being able to measure the size difference as function of the size (i.e. field depent testing) is especially important when the macropsia (or micropsia) has a retinal origin.
Treatment
The most common way to treat forms of aniseikonia, including macropsia, is through the use of auxiliary optics to correct for the magnificationMagnification
Magnification is the process of enlarging something only in appearance, not in physical size. This enlargement is quantified by a calculated number also called "magnification"...
properties of the eyes
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
. This method includes changing the shape of spectacle lenses, changing the vertex distances with contact lenses, creating a weak telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
system with contact lenses and spectacles, and changing the power of one of the spectacle lenses. Computer software, such as the Aniseikonia Inspector, has been developed to determine the prescription needed to correct for a certain degree of aniseikonia. The problem with correction through optical means is that the optics do not vary with field angle and thus cannot compensate for non-uniform macropsia. Patients have reported significantly improved visual comfort associated with a correction of 5-10% of the aniseikonia.
With regard to drug-induced or virus-induced macropsia, once the underlying problem, either drug abuse or viral infection, is treated, the induced macropsia ceases.
Future Research
Future research may focus on ways to limit the occurrence of retinally-induced macropsia due to surgery. In terms of treatment, the most effective optical correction is still being researched with respect to visual field angles and direction to a target. The susceptibility of certain age demographics to macropsia is a subject that requires further validation. Overall, there have not been very many reports of macropsia induced by certain drugs, specifically zolpidem and citalopram. Once a larger effort is made to compile such reports, there will inevitably be more research on the subject of macropsia.Famous Sufferers of Macropsia
- Edgar Allan PoeEdgar Allan PoeEdgar Allan Poe was an American author, poet, editor and literary critic, considered part of the American Romantic Movement. Best known for his tales of mystery and the macabre, Poe was one of the earliest American practitioners of the short story and is considered the inventor of the detective...
- Lewis CarrollLewis CarrollCharles Lutwidge Dodgson , better known by the pseudonym Lewis Carroll , was an English author, mathematician, logician, Anglican deacon and photographer. His most famous writings are Alice's Adventures in Wonderland and its sequel Through the Looking-Glass, as well as the poems "The Hunting of the...
- Käthe Schmidt Kollwitz