Macropsia is a neurological condition affecting human visual perception, in which objects within an affected section of the visual field appear larger than normal, causing the person to feel smaller than they actually are. Macropsia, along with its 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.
Signs and symptoms The most obvious symptom 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 their 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. 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.
Psychological effects There are a broad range of psychological and emotional effects that a person with 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. They may be in an irritable or angry state, or in contrast, a euphoric 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 affected may experience extreme anxiety both during and after episodes as a result of the overwhelming nature of their distorted visual field. Due to the fear and anxiety associated with the condition, those who have previously had 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 they 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. They, 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-term sufferers or people who have had the condition since childhood may be greater and lead to severe ego-deficiencies. An alternative 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, they are overcoming that physiological contraction. However, this theory has been under much scrutiny.
Causes
Structural defects In cases where macropsia affects one eye 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-off 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 occipitotemporal visual pathway can cause macropsia. This lesion can be due to an ischemic cell death after an acute posterior cerebral infarction.
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