Perception of depth and dimensionality disappears into a scotoma of darkness.
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For me, aura includes scintillating scotoma, which basically looks like an oscillating, shimmering fractal pattern disturbing my normal vision in one eye.
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Relúmĭno helps people with low vision in several ways: it can magnify or minimize images, adjust brightness and sharpness, highlight objects with an outline, invert colors when reading text, add a color filter to the screen, enhance a user's peripheral field if they have tunnel vision, and even assist people with scotoma by helping them see what is blocked by their blind spot in the surrounding area.
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Seidel's sign (also called Seidel's scotoma) is a sickle-shaped scotoma that is a superior or inferior extension of the blind spot. It occurs in some patients with glaucoma.
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A scotoma is an area of lost or depressed vision within the visual field, surrounded by an area of less depressed or of normal vision. Traquair described the scotoma which bears his name as follows:‘At the chiasmal termination of the nerve the crossed and uncrossed fibres separate, and a small lesion may occur at this point and effect the crossed fibres only, producing a unilateral temporal hemianopic or quadrantic central scotoma called ‘‘junction’’ scotoma, since it indicates the site of the lesion at the junction of the optic nerve and chiasma’.Traquair HM in Clinical perimetry, Scott, GI.(ed), London: Henry Kimpton, 1957 The 'Traquair scotoma' or 'Traquair junctional scotoma' is found in 1 – 10% of patients with pituitary adenomaElkington. SG. Pituitary adenoma, preoperative symptomatology in a series of 260 patients.
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Symptoms typically appear gradually over 5 to 20 minutes and generally last less than 60 minutes, leading to the headache in classic migraine with aura, or resolving without consequence in acephalgic migraine. Many migraine sufferers change from scintillating scotoma as a prodrome to migraine to scintillating scotoma without migraine. Typically the scotoma resolves spontaneously within the stated time frame, leaving no subsequent symptoms, though some report fatigue, nausea, and dizziness as sequelae.
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The size of the monocular scotoma is 5×7 degrees of visual angle. A scotoma can be a symptom of damage to any part of the visual system, such as retinal damage from exposure to high-powered lasers, macular degeneration and brain damage. The term scotoma is also used metaphorically in several fields. The common theme of all the figurative senses is of a gap not in visual function but in the mind's perception, cognition, or world view.
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Even a small scotoma that happens to affect central or macular vision will produce a severe visual disability, whereas a large scotoma in the more peripheral part of a visual field may go unnoticed by the bearer because of the normal reduced optical resolution in the peripheral visual field.
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Most cases of polyopia are accompanied by another neurological condition. Polyopia is often accompanied by visual field defects (such as the presence of a scotoma) or transient visual hallucinations. Polyopic images often form in the direction and position of such visual field defects. Current research shows that when stimuli are close to the patient’s scotoma, the latency of polyopic images is much shorter than if the stimuli was far from the scotoma, and there is a higher probability that polyopic images will result.
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Chart 2 is similar to chart 1, but it has diagonal cross lines, which assist correct fixation in case of central scotoma.
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Common problems of the visual field include scotoma (area of reduced vision), hemianopia (half of visual field lost), homonymous hemianopsia and bitemporal hemianopia.
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Chart 4 has no lines, only a random pattern of white dots in black background. It was intended to differentiate areas of scotoma and metamorphosia.
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The British physician John Fothergill described the condition in the 18th century and called it fortification spectrum. The British physician Hubert Airy coined the term scintillating scotoma for it by 1870; he derived it from the Latin scintilla "spark" and the Ancient Greek skotos "darkness". Other terms for the condition include flittering scotoma, fortification figure, fortification of Vauban, geometrical spectrum, herringbone, Norman arch, teichopsia, and telehopsia.
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Preferential hyperacuity perimetry (PHP) is a psychophysical test used to identify and quantify visual abnormalities such as metamorphopsia and scotoma. It is a type of perimetry.
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2018 Scotoma. Conduit Gallery. Dallas, TX 2017 The Long Goodbye. Museo de la Ciudad Queretaro. Queretaro, Mexico 2016 Styles of Radical Will (Italian Sculpture) Sector 2337.
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Amblyopia caused by tobacco or alcohol had been recognised for many years but it was Traquair who gave the most accurate and detailed account of amblyopia caused by tobacco. He described it as follows: 'The scotoma is typically centrocecal in position, and is never central in true sense, that is to say, pericentral...The diffuse nature of the scotoma and its sloping ill- defined margins are valuable signs'.
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Progressive add reading portions for plus lenses are also ground onto the anterior surface of the lens. The blended curvature of aspheres reduces scotoma, a ringed blind spot.
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A scotoma often occurs when the visual disturbance moves to the periphery of the visual field. Additionally, a scotoma can sometimes occur in the center of the visual field which will appear as a more distinct blindspot, although this is less common. Individuals with persistent MA may also report a visual disturbance called 'visual snow'. Generally, they will describe their visual field as consisting of many small flickering spots which may resemble snow.
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Suppression of an eye is a subconscious adaptation by a person's brain to eliminate the symptoms of disorders of binocular vision such as strabismus, convergence insufficiency and aniseikonia. The brain can eliminate double vision by ignoring all or part of the image of one of the eyes. The area of a person's visual field that is suppressed is called the suppression scotoma (with a scotoma meaning, more generally, an area of partial alteration in the visual field). Suppression can lead to amblyopia.
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A scotoma is an area of partial alteration in the field of vision consisting of a partially diminished or entirely degenerated visual acuity that 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 termed its blind spot. This is a location with no photoreceptor cells, where the retinal ganglion cell axons that compose the optic nerve exit the retina. This location is called the optic disc.
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In cases where the patient has central suppression the following will occur. When the prism is placed in front of the non-deviating eye, both eye will produce a conjugate movement in the direction of the prism apex. However unlike a normal response, the fellow deviated eye will not make a corrective movement because diplopia has not been appreciated since the image will fall into the suppression scotoma. Whereas when the prism is placed in front of the deviated eye, the image instantly falls into the suppression scotoma, diplopia is not detected.
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Symptom-producing, or pathological, scotomata may be due to a wide range of disease processes, affecting any part of the visual system, including the retina (in particular its most sensitive portion, the macula), the optic nerve and even the visual cortex."Bilateral effects of unilateral visual cortex lesions in human", Matthew Rizzo and Donald A. Robin, Brain (1996), 119, pages 951-96. A pathological scotoma may involve any part of the visual field and may be of any shape or size. A scotoma may include and enlarge the normal blind spot.
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It may be difficult to read and dangerous to drive a vehicle while retinal migraine symptoms are present. Retinal migraine is a different disease than scintillating scotoma, which is a visual anomaly caused by spreading depression in the occipital cortex at the back of the brain, not in the eyes nor any component thereof. Unlike in retinal migraine, a scintillating scotoma involves repeated bouts of temporary diminished vision or blindness and affects vision from both eyes, upon which sufferers may see flashes of light, zigzagging patterns, blind spots, or shimmering spots or stars.
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An Amsler grid, as seen by a person with normal vision. Symptoms entail a loss of visual acuity in both eyes, including darkened vision, ring scotoma (ring of blindness close to the center of vision), color blindness, and difficulty with bright lights. The scotoma may cause text slightly away from the center of vision to disappear; the appearance would not be black (in early stages) but of the same color as the nearby background. Many lines of an Amsler grid would be faded or invisible to the patient.
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There were also a couple of active Thrash metal bands during that era giving great live shows such as Regicide (supporting Epidemic) and then Scotoma. Eventually, the 1990s were a very active period for the scene in general.
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Patients commonly present with acute unilateral painless decreased vision and photopsias. Presentations like central or paracentral scotoma, Floaters and dyschromatopsia are less common. An antecedent viral prodrome occurs in approximately one-third of cases. Myopia is commonly seen in patients.
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Commonly posterior colobomata affect the inferior retina, with resultant deficit in the superior visual field. Other conditions can be associated with a coloboma. Sometimes, the eye may be reduced in size, a condition called microphthalmia. Glaucoma, nystagmus, scotoma, or strabismus may also occur.
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The Framingham Heart Study, published in 1998, surveyed 5,070 people between ages 30-62 and found that scintillating scotomas without other symptoms occurred in 1.23% of the group. The study did not find a link between late-life onset scintillating scotoma and stroke.
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Ocular or retinal migraines happen in the eye, so only affect the vision in that eye, while visual migraines occur in the brain, so affect the vision in both eyes together. Visual migraines result from cortical spreading depression and are also commonly termed scintillating scotoma.
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Assessment of alleged retinal laser injuries. Arch Ophthalmol, 122, 1210–1217 provide one case, an 11-year-old child who temporarily damaged her eyesight by holding an approximately 5 mW red laser pointer close to the eye and staring into the beam for 10 seconds; she experienced scotoma (a blind spot) but fully recovered after three months. Luttrull & Hallisey (1999) describe a similar case, a 34-year-old male who stared into the beam of a class IIIa 5 mW red laser for 30 to 60 seconds, causing temporary central scotoma and visual field loss. His eyesight fully recovered within two days, at the time of his eye exam.
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Wilbrand's knee: Inferonasal fibres of the optic nerve which go into the contralateral optic nerve 4 mm before crossing over to the opposite optic tract. A lesion here produces a junctional scotoma in the superior temporal field of the optic nerve opposite the site of injury.
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The main features are seen on fundus examination, just before or subsequent to the onset of visual loss. A pupillary defect may be visible in the acute stage as well. Examination reveals decreased visual acuity, loss of color vision and a cecocentral scotoma on visual field examination.
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Scintillating scotoma is a common visual aura that was first described by 19th-century physician Hubert Airy (1838–1903). It may precede a migraine headache, but can also occur acephalgically (without headache). It is often confused with retinal migraine, which originates in the eyeball or socket.
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In a pregnant woman, scotomata can present as a symptom of severe preeclampsia, a form of pregnancy-induced hypertension. Similarly, scotomata may develop as a result of the increased intracranial pressure that occurs in malignant hypertension. The scotoma is also caused by the aminoglycoside antibiotics mainly by Streptomycin.
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Retinal migraines are a subclass of optical migraines. Sufferers will experience a scotoma--a patch of vision loss in one eye surrounded by normal vision--for less than one hour before vision returns to normal. Retinal migraines may be accompanied by a throbbing unilateral headache, nausea, or photophobia.
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Individuals who experience acephalgic migraines in childhood are highly likely to develop typical migraines as they grow older. Among women, incidents of acephalgic migraine increase during perimenopause. Scintillating scotoma is the most common symptom which usually happens concurrently with Expanding Fortification Spectra. Also frequently reported is monocular blindness.
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Hubert Airy (June 14, 1838 – June 1, 1903) was an English physician who was the pioneer in the study of migraine. He was the son of Sir George Airy, Astronomer Royal. He has two portraits in the National Portrait Gallery. He coined the term Scintillating scotoma for the common visual aura.
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In 1869, Jacob Hermann Knapp described scotoma and metamorphopsia in traumatic maculopathy with choroidal rupture using horizontal lines.Similarly in 1874, Richard Forster demonstrated metamorphopsia using a square grid. Swiss ophthalmologist Marc Amsler described the Amsler grid in the year 1945. It was the first functional test proposed to evaluate metamorphopsia.
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Onset : Early childhood Progression: Chronic progressive Clinical: Cerebellar ataxia plus syndrome / Optic Atrophy Plus Syndrome Ocular: Optic atrophy, nystagmus, scotoma, and bilateral retrobulbar neuritis. Other: Mental retardation, myoclonic epilepsy, spasticity, and posterior column sensory loss. Tremor in some cases. Musculoskeletal Contractures, lower limbs, Achilles tendon contractures, Hamstring contractures, Adductor longus contractures Systemic Hypogonadotrophic hypogonadism.
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Maggy tells a little about the hostile attitude of the father's doctor, one Doctor Scotoma. Yet Jim and X-- end up on a train back to Manhattan. They dine and barhop. Soon after three in the morning they encounter a policeman, and Jim offers up a photograph, apparently of his parents, an event that X-- obsesses over.
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1): 1-160. commonly referred to as persistent migraine aura (PMA). In other clinical sub-forms of migraine headache may be absent and the migraine aura may not take the typical form of the zigzagged fortification spectrum (scintillating scotoma), but manifests with a large variety of focal neurological symptoms. The role of hallucinogens in visual snow is not clear.
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It is used as a metaphor of physical and spiritual health.Constant Mews, "Religious Thinker," in Newman, 57-58. Some authors, such as Charles Singer, have suggested that the characteristics of the descriptions of the visions and the illustrations, such as bright lights and auras, imply they may have been caused by scintillating scotoma, a migraine condition.King-Lenzmeier, 48.
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They talk philosophy, they know Testic is dead, they suspect Jim is dead also, they encourage X-- to continue in his normal business. X-- travels on business for Colletti to a Florida island. He is accosted by Testic's father, who accuses X-- of the murder of his son. He is also accosted by Doctor Scotoma, who speaks very negatively about drugs.
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During an eye examination, the presence of suppression and the size and location of the suppression scotoma may be the Worth 4 dot test (a subjective test that is considered to be the most precise suppression test), or with other subjective tests such as the Bagolini striated lens test, or with objective tests such as the 4 prism base out test.
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Vision abnormalities such as metamorphopsia (distortions) and scotoma are symptoms of retinal diseases such as macular degeneration. In advanced stages of the disease, photoreceptor cells may be irreversibly damaged. Hence, if not treated, macular degeneration may lead to blindness. Awareness to early changes in vision, especially in high risk patients, leads to early treatment (such as intravitreal injection of anti-VEGF factors, e.g.
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He became known for his research on neuropsychology of visionPöppel E, Von Cramon D, Backmund H, Eccentricity-specific dissociation of visual functions in patients with lesions of the central visual pathways. Nature, 1975, 256(5517): 489-490.Pöppel E, Bridging a neuronal gap. Perceptual completion across a cortical scotoma is dependent on stimulus motion. Naturwissenschaften, 1985, 72(11): 599-600.
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Less common, but important because they are sometimes reversible or curable by surgery, are scotomata due to tumors such as those arising from the pituitary gland, which may compress the optic nerve or interfere with its blood supply. Rarely, scotomata are bilateral. One important variety of bilateral scotoma may occur when a pituitary tumour begins to compress the optic chiasm (as distinct from a single optic nerve) and produces a bitemporal paracentral scotoma, and later, when the tumor enlarges, the scotomas extend out to the periphery to cause the characteristic bitemporal hemianopsia. This type of visual-field defect tends to be obvious to the person experiencing it but often evades early objective diagnosis, as it is more difficult to detect by cursory clinical examination than the classical or textbook bitemporal peripheral hemianopia and may even elude sophisticated electronic modes of visual-field assessment.
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Papillitis may have the same appearance as papilledema. However, papillitis may be unilateral, whereas papilledema is almost always bilateral. Papillitis can be differentiated from papilledema by an afferent pupillary defect (Marcus Gunn pupil), by its greater effect in decreasing visual acuity and color vision, and by the presence of a central scotoma. Papilledema that is not yet chronic will not have as dramatic an effect on vision.
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Burning feet syndrome, also known as Grierson-Gopalan syndrome, is a medical condition that causes severe burning and aching of the feet, hyperesthesia, and vasomotor changes of the feet that lead to excessive sweating. It can even affect the eyes, causing scotoma and amblyopia. The condition occurs more frequently in women, and usually manifests itself when a person is between twenty and forty years old.
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In these subjects, some features filled in the scotoma faster than others, and in some circumstances filling-in took some seconds before it was completed (while filling-in across the blind spot is immediate). Together these data suggested that mechanisms for the filling-in of colours, motion and texture can be dissociated and may correspond to processes in higher-order areas that are specialized for these attributes.
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Her recognition time for visual objects and words was slightly higher than the control, but not statistically significant. There was no restriction in her visual field and no scotoma. ;Disturbance of movement vision LM's impression of movement depended on the direction of the movement (horizontal vs vertical), the velocity, and whether she fixated in the center of the motion path or tracked the object with her eyes.
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Therefore, is indicated in cases of a suspected central suppression scotoma as it can be used to detect where the lights may not be appreciated from the eye with the scotoma though in some cases of minimal deviation in the eye as demonstrated in a microtropic deviation a normal response of 4 lights may be reported. Though it can be used in these patients to prove the presence of peripheral fusion and that they have bi-foveal fixation. Other indications for the test include establishing an individual's dominant eye dominant eye compared to the other and when evaluating reduced monocular visual acuity which shows no improve on pinhole testing. Whilst there are no contraindications of the W4LT there needs to be caution in interpreting the results of individuals with BSV in natural conditions as they may show a diplopic response under the dissociation of the test.
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Their stereoacuity is often in the range of 3000 to 70 arcsecond, and a small central suppression scotoma of 2 to 5 deg. A rare condition, MFS is estimated to affect only 1% of the general population. There are three distinguishable forms of this condition: primary constant, primary decompensating, and consecutive MFS. It is believed that primary MFS is a result of a primary sensorial defect, predisposing to anomalous retinal correspondence.
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Photocoagulation was recommended by Gass and remains to date the mainstay of treatment. It seems to be successful in causing resolution of exudation and VA improvement or stabilization in selected patients. Photocoagulation should be used sparingly to reduce the chance of producing a symptomatic paracentral scotoma and metamorphopsia. Small burns (100–200 μm) of moderate intensity in a grid- pattern and on multiple occasions, if necessary, are recommended.
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For instance, it can constitute the aura phase of migraine. Concomitant presence of a moving scintillating scotoma is suggestive of migraine,eMedicine > Posterior Cerebral Artery Stroke Authors: Christopher Luzzio and Consuelo T Lorenzo. Updated: Jul 15, 2009 but has been seen in cerebral cancer as well. Computed tomography (CT scan) or MRI can be used to investigate if stroke, tumor, structural lesion, or demyelination is the cause of homonymous hemianopsia.
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In addition to the retinal findings, temporal pallor of the optic disc is commonly observed. As expected, visual field testing in cone dystrophy usually reveals a central scotoma. In cases with the typical bull’s-eye appearance, there is often relative central sparing. Because of the wide spectrum of fundus changes and the difficulty in making the diagnosis in the early stages, electroretinography (ERG) remains the best test for making the diagnosis.
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Lens box diagrams used in dispensing should consider edge thickness, reduced by smaller eyesizes, and oval/circular shapes. The bridge should be fitted to increase surface contact using rigid nose support if possible. Weight problems associated with these lenses are often not anticipated by untrained dispensaries, and end products are disappointing after inclusion of special instructions to fabricating labs. In some cases, more aesthetic aspheric lens designs can be fitted, reducing Scotoma associated with lenticulars.
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Metamorphopsia may be a subjective complaint. Due to the development of paracentral scotoma (blind spots), reading ability is impaired early in the disease course. It might be even the first symptom of the disease. The condition may remain stable for extended periods, sometimes interspersed with sudden decreases in vision. Patients’ loss of visual function is disproportionately worse than the impairment of their visual acuity, which is only mildly affected in many cases.
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Acephalgic migraine is a neurological syndrome. It is a variant of migraine in which the patient may experience aura symptoms such as scintillating scotoma, nausea, photophobia, hemiparesis and other migraine symptoms but does not experience headache. Acephalgic migraine is also referred to as amigrainous migraine, ocular migraine, ophthalmic migraine or optical migraine, last three being misnomers. Sufferers of acephalgic migraine are more likely than the general population to develop classical migraine with headache.
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Glaucoma is a type of blindness that begins at the edge of the visual field and progresses inward. It may result in tunnel vision. This typically involves the outer layers of the optic nerve, sometimes as a result of buildup of fluid and excessive pressure in the eye. Scotoma is a type of blindness that produces a small blind spot in the visual field typically caused by injury in the primary visual cortex.
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Photic retinopathy is damage to the macular area of the eye's retina that results from prolonged exposure to sunlight, particularly with dilated pupils. This can happen, for example, while observing a solar eclipse without suitable eye protection. The Sun's radiation creates a photochemical reaction that can result in visual dazzling and a scotoma. The initial lesions and edema will disappear after several weeks, but may leave behind a permanent reduction in visual acuity.
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Young children with strabismus normally suppress the visual field of one eye (or part of it), whereas adults who develop strabismus normally do not suppress and therefore suffer from double vision (diplopia). This also means that adults (and older children) have a higher risk of post- operative diplopia after undergoing strabismus surgery than young children. Patients who have undergone strabismus surgery at a young age often have monofixation syndrome (with peripheral binocular fusion and a central suppression scotoma).
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The degree of vision loss can extend to total blindness, but a loss beyond 20/400 is rare, except in the case of methanol ingestion. Peripheral vision is usually spared since the pattern of loss typically involves a central or cecocentral scotoma, a visual field defect at or surrounding the point of fixation. This pattern can be revealed via visual field testing. Upon examination, the pupils usually demonstrate a normal response to light and near stimulation.
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The fourth case of visual changes on orbit was significant for a past history of transsphenoidal hypophysectomy for macroadenoma where postoperative imaging showed no residual or recurrent disease. Approximately 2 months into the ISS mission, the astronaut noticed a progressive decrease in near-visual acuity in his right eye and a scotoma in his right temporal field of vision. Figure 5: On-orbit ultrasound of posterior orbit of the fourth case of visual changes from long-duration spaceflight.
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Retinal migraine is associated with transient monocular visual loss (scotoma) in one eye lasting less than one hour. During some episodes, the visual loss may occur with no headache and at other times throbbing headache on the same side of the head as the visual loss may occur, accompanied by severe light sensitivity and/or nausea. Visual loss tends to affect the entire monocular visual field of one eye, not both eyes. After each episode, normal vision returns.
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Visual processing in the brain goes through a series of stages. Destruction of the primary visual cortex leads to blindness in the part of the visual field that corresponds to the damaged cortical representation. The area of blindness – known as a scotoma – is in the visual field opposite the damaged hemisphere and can vary from a small area up to the entire hemifield. Visual processing occurs in the brain in a hierarchical series of stages (with much crosstalk and feedback between areas).
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There is no direct conscious awareness of visual scotomas. They are simply regions of reduced information within the visual field. Rather than recognizing an incomplete image, patients with scotomas report that things "disappear" on them. The presence of the blind spot scotoma can be demonstrated subjectively by covering one eye, carefully holding fixation with the open eye, and placing an object (such as one's thumb) in the lateral and horizontal visual field, about 15 degrees from fixation (see the blind spot article).
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Riddoch syndrome (also known as the Riddoch phenomenon) is a form of visual impairment often caused by lesions in the occipital lobe which limit the sufferer's ability to distinguish objects. Only moving objects in the scotoma are visible, static ones being invisible to the patient. The moving objects are not perceived to have color or detail. The subject may only have awareness of the movement without visual perception of it (gnosanopsia), or the general shape of a moving object may be perceivable as a shadow like outline.
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A myodisc or myopic disk is a corrective lens with a steep concave curvature that is fitted on the posterior surface of a carrier lens, or a high power single-vision lens specially ordered with slab-off the edge, creating a central prescription disc. These are used for correction of extremely high myopia often seen in low vision patients. Myodiscs are not a preferred lens type, but are the least expensive option among available lenses fitted for minus powers beyond -12 diopters. They are cheap to produce but cause scotoma, a ringed blind spot.
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The premise of the neuropsychological model is that there is a difference between cultural imagery and neurologically produced visual patterns known as entoptic phenomena. During ASCs, which can be induced in a number of ways, the first stage of hallucination experienced by a subject contains only entoptic phenomena, such as the scintillating scotoma experienced by migraine sufferers. The second stage begins when the hallucinations are construed by the subject into culturally familiar content. The implication of this is that entoptic phenomena will be understood differently in different cultures.
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Also, Gilbert covers the topic of 'filling in' or the frequent use of patterns, by the mind, to connect events which we do actually recall with other events we expect or anticipate fit into the expected experience. This 'filling in' is also used by our eyes and optic nerves to remove our blind spot or scotoma, and instead substitute what our mind expects to be present in the blind spot. The book is written for the layperson, generally avoiding abstruse terminology and explaining common quirks of reasoning through simple experiments that exploited them.
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A myopic crescent is a moon-shaped feature that can develop at the temporal (lateral) border of disc (it rarely occurs at the nasal border) of myopic eyes. It is primarily caused by atrophic changes that are genetically determined, with a minor contribution from stretching due to elongation of the eyeball. In myopia that is no longer progressing, the crescent may be asymptomatic except for its presence on ocular examination. However, in high- degree myopia, it may extend to the upper and lower borders, or form a complete ring around the optic disc and form a central scotoma.
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Papilledema as a result of dural sinus thrombosis and atrophy resulting from retinal disease, have been characterized as secondary causes of optic nerve atrophy in Behçet's disease. Signs and symptoms of acute optic neuropathy include painless loss of vision which may affect either one or both eyes, reduced visual acuity, reduced color vision, relative afferent pupillary defect, central scotoma, swollen optic disc, macular edema, or retrobulbar pain. When these symptoms occur with concurrent mucocutaneous ulcerations, they raise suspicion of acute optic neuropathy in Behçet's Disease. Progressive optic atrophy may result in decreased visual acuity or color vision.
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The presence of the pigment in the radially arranged axons of the Henle fiber layer causes it to be dichroic and birefringent to blue light. This effect is visible through the Haidinger's brush when the fovea is pointed to a polarized light source. The combined effects of the macular pigment and the distribution of short wavelength cones results in the fovea having a lower sensitivity to blue light (blue light scotoma). Though this is not visible under normal circumstances due to "filling in" of information by the brain, under certain patterns of blue light illumination, a dark spot is visible at the point of focus.
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The loss of peripheral vision while retaining central vision is known as tunnel vision, and the loss of central vision while retaining peripheral vision is known as central scotoma. Peripheral vision is weak in humans, especially at distinguishing detail, color, and shape. This is because the density of receptor and ganglion cells in the retina is greater at the center and lowest at the edges, and, moreover, the representation in the visual cortex is much smaller than that of the fovea (see visual system for an explanation of these concepts). The distribution of receptor cells across the retina is different between the two main types, rod cells and cone cells.
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Retinal damage is a serious but very rare complication (<1%) that can occur during the use of lasers. If the fiber breaks or if the laser is activated when the laser is outside of the body, reflected laser light may cause a focal permanent retinal deficit or "blind spot" or scotoma. The nominal hazard zone (NHZ) or space within which the level of direct, scattered, or reflected laser radiation exceeds the maximum permissible exposure (MPE), varies by the wavelength of the laser and is shorter (17 inches) with the newer 1470 nm laser. Use of appropriate protective eyeware specific to the wavelength laser being used prevents accidental injury.
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O.W. Sacks, "Scotoma: Forgetting and Neglect in Science," in Hidden Histories of Science, Ed. R.B. Silver (New York: New York Review of Books, 1996), 141-187. Goldberg's work on frontal lobe functions includes the discovery of the "reticulo-frontal disconnection" syndrome, functional lateralization and gender differences in the prefrontal cortex. His work on memory includes the description of relatively pure retrograde amnesia without anterograde amnesia, which in turn has led to the elucidation of the role of brain stem arousal mechanisms in memory. In clinical practice, Goldberg was among the early proponents of "cognitive fitness," purporting to harness the effects of lifelong neuroplasticity to delay and even reverse the effects of cognitive aging.
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This suggests that aspects of schema in the mind (body schema, world schema) have neurologic bases that cannot be revised by mere intellectual understanding—at least not quickly. Sacks does explore the topic of how people adapt to phantoms over the years and how positive phantom limbs often gradually foreshorten and sometimes disappear; but some remain for the rest of life. At a higher level of abstraction are what have been called ', in which a person's self-perception of his or her own personality is judged by others to have a gap in perceptive ability. Thus, in psychology, scotoma can refer to a person's inability to perceive personality traits in themselves that are obvious to others.
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The information leads to a qualitative assessment that included "scotoma stimulation, with the LGN intact had fMRI activation of ~20% of that under normal conditions". This finding agrees with the information obtained from, and fMRI images of, patients with blindsight. The same study also supported the conclusion that the LGN plays a substantial role in blindsight. Specifically, while injury to V1 does create a loss of vision, the LGN is less affected and may result in the residual vision that remains, causing the "sight" in blindsight. Functional magnetic resonance imaging was has also been employed to conduct brain scans in normal, healthy human volunteers to attempt to demonstrate that visual motion can bypass V1, through a connection from the LGN to the human middle temporal complex.
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Although not truly an active prosthesis, an implantable miniature telescope is one type of visual implant that has met with some success in the treatment of end-stage age-related macular degeneration. This type of device is implanted in the eye's posterior chamber and works by increasing (by about three times) the size of the image projected onto the retina in order to overcome a centrally located scotoma or blind spot. Created by VisionCare Ophthalmic Technologies in conjunction with the CentraSight Treatment Program, the telescope is about the size of a pea and is implanted behind the iris of one eye. Images are projected onto healthy areas of the central retina, outside the degenerated macula, and is enlarged to reduce the effect the blind spot has on central vision.
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Common causes of scotomata include demyelinating disease such as multiple sclerosis (retrobulbar neuritis), damage to nerve fiber layer in the retina (seen as cotton wool spots"The role of axoplasmic transport in the pathogenesis of retinal cotton-wool spots", D. McLeod, J. Marshall, E. M. Kohner, and A. C. Bird, Br J Ophthalmol (1977), 61(3), pages 177–191.) due to hypertension, toxic substances such as methyl alcohol, ethambutol and quinine, nutritional deficiencies, vascular blockages either in the retina or in the optic nerve, stroke or other brain injury, and macular degeneration, often associated with aging. Scintillating scotoma is a common visual aura in migraine."Possible Roles of Vertebrate Neuroglia in Potassium Dynamics, Spreading depression, and migraine", Gardner-Medwin, J. Exp. Biol. (1981), 95, pages 111-127 (Figure 4).
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This theory is supported by findings that parafoveal retinal lesions deprive a region of striate cortex of visual input, and as a result, the receptive fields of neurons near the boundary of the deprived cortical region enlarge and expand into nearby regions of the visual field. Thus, polyopia results from altered coding of contour information by neurons near the lesioned area. This mechanism offers that after a focal lesion of neurons in striate cortex, or following a retinal lesion depriving these neurons of visual input, the receptive fields of nearby healthy neurons converge to code information about contours of objects normally coded by the damaged neurons while still coding the same information about retinal location prior to the injury. This mechanism may explain why polyopia extending into a patient’s scotoma occurs following damage to primary visual cortex.
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Beyond its literal sense concerning the visual system, the term scotoma is also used metaphorically in several fields, including neurology, neuropsychology, psychology, philosophy, and politics. The common theme of all the figurative senses is of a gap not in visual function but in the mind's perception, cognition, or world view. Their concrete connection to the literal sense, however, is by the connection between the nervous system and the mind, via the chain of links from sensory input, to nerve conduction, to the brain, to perception (the processing and interpreting of that input) via the brain-mind correlation, to psychological function. Thus there is not only (or not necessarily) a visual inability to see an aspect of reality but also (or instead) a mental inability to conceive even the possibility of seeing that aspect, due to a cognitive schema that lacks any provision for it.
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At the most concrete level, there is neuropsychological scotoma. One example is the hemispatial neglect that is sometimes experienced by people who have had strokes. Another type is the phenomenon of reverse or negative phantom limb, in which nerve injuries to the limbs, such as trauma in which a limb's nerves are severed but the limb is spared from amputation, can affect the mind's body schema in such a way that an existing limb seems to its owner like it should not exist, and its presence thus seems uncanny. Neurologist Oliver Sacks, who experienced a reverse phantom leg that later resolved, considered it a form of spatial neglect in the body schema analogous to hemispatial neglect in that the mind could not conceive of the leg as self because it could not conceive that there was any space for the leg to exist in.
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Sacks and others agreed that the leg thus seemed like someone else's leg, including sometimes a cadaverous one, which was part of the reason for the dysphoria but not the sole explanation. Even for people who intellectually understood that the leg or hand was supposed to be theirs simply could not believe it emotionally and could not completely reconcile reality with schema, prompting great unease. Given how hard this is to comprehend for a person who has not experienced it, people recently experiencing it for the first time consider it both uncanny and ineffable (as Sacks self-reported and found in others). Sacks also explored the regular type of phantom limb (a positive phantom), which does not produce a neuropsychological scotoma but shares with reverse phantoms the trait that the body schema resists revision despite a person's perfect intellectual awareness and acceptance of the current physical reality (that is, that the amputated limb is gone or that the spared limb is still present).
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