Микропсия: Көру қабілетінің бұзылысы және оның себептері

Micropsia is a condition affecting human visual perception in which objects are perceived to be smaller than they actually are. Micropsia can be caused by optical factors (such as wearing glasses), by distortion of images in the eye (such as optically, via swelling of the cornea or from changes in the shape of the retina such as from retinal edema, macular degeneration, or central serous retinopathy), by changes in the brain (such as from traumatic brain injury, epilepsy, migraines, prescription drugs, and illicit drugs), and from psychological factors. Dissociative phenomena are linked with micropsia, which may be the result of brain lateralization disturbance. Micropsia is also commonly reported when the eyes are fixating at (convergence), or focusing at (accommodation), a distance closer than that of the object in accord with Emmert's law. Specific types of micropsia include hemimicropsia, a form of micropsia that is localized to one half of the visual field and can be caused by brain lesions in one of the cerebral hemispheres. 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.

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 with 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 having micropsia.

EEG 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. 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 individuals with certain psychiatric disorders.

Of all of the visual distortions, micropsia has the largest variety of causes. 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.

The most frequent neurological origin of micropsia is a result of temporal lobe 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.

Micropsia can result from the action of mescaline and other hallucinogenic drugs. 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.

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.

Micropsia can be caused by swelling of the cornea 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.

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 detachment. After surgery, patients may experience micropsia as a result of larger photoreceptor separation by edematous fluid.

Macular degeneration typically produces micropsia due to the swelling or bulging of the macula, 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%.

CSCR 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.

Micropsia is sometimes seen in individuals with brain infarctions. 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. 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 those with migraines 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. based on the small people that inhabited the island of Lilliput in the novel.

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. 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.