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{{BioPsy}}
 
{{BioPsy}}
{{DiseaseDisorder infobox |
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{{Infobox Disease |
Name = Scotoma |
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Name = Scotoma |
ICD10 = H53.4, H53.1 |
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Image = |
ICD9 = {{ICD9|368.4}}, {{ICD9|368.12}} |
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Caption = |
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DiseasesDB = |
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ICD10 = {{ICD10|H|53|4|h|53}}, {{ICD10|H|53|1|h|53}} |
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ICD9 = {{ICD9|368.4}}, {{ICD9|368.12}} |
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ICDO = |
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OMIM = |
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MedlinePlus = |
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eMedicineSubj = |
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eMedicineTopic = |
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MeshID = D012607 |
 
}}
 
}}
A '''scotoma''' ([[Greek language|Greek]]: ''darkness''; plural: "scotomas" or "'''scotomata'''") is an area or island of loss or impairment of [[visual acuity]] surrounded by a field of normal or relatively well-preserved [[Visual perception|vision]].
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A '''scotoma''' ([[Greek language|Greek]] for ''darkness''; plural: "scotomas" or "'''scotomata'''") is an area or island of loss or impairment of [[visual acuity]] surrounded by a field of normal or relatively well-preserved [[Visual perception|vision]].
   
Every normal [[mammal]]ian eye has a scotoma in its field of vision, usually termed its [[blind spot (vision)|blind spot]]. The presence of this normal scotoma does not intrude into [[consciousness]] because it is very small, but it can be demonstrated to oneself by the simplest of clinical methods.
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[[Image:NormalField.jpg|thumb|Example image showing normal field of vision.]]
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[[Image:CentralScotoma.jpg|thumb|Example image showing small, deep central scotoma, as may be caused by [[age-related maculopathy]].]]
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[[Image:ConstrictedField.jpg|thumb|Example image showing a peripheral ring scotoma, as may be caused by [[retinitis pigmentosa]].]]
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[[Image:ScintillatingScotoma3.jpg|thumb|Example of a [[scintillating scotoma]], as may be caused by [[cortical spreading depression]].]]
   
Symptom-producing or [[pathology|pathological]] scotomata may be due to a wide range of disease processes, affecting either the [[retina]] (in particular its most sensitive portion, the [[macula]]) or the [[optic nerve]] itself. 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. Even a small scotoma that happens to affect central or [[macula]]r vision will produce a severe visual [[Disability|handicap]], whereas a large scotoma in the more peripheral part of a visual field may go unnoticed by the bearer.
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Every normal [[mammal]]ian eye has a scotoma in its field of vision, usually termed its [[blind spot (vision)|blind spot]]. This is a location with no [[photoreceptor]]s, where the [[retina]]l [[ganglion cell]] [[axons]] that comprise the [[optic nerve]] exit the retina. This location is called the [[optic disc]]. When both eyes are open, visual signals that are absent in the blind spot of one eye are provided from the opposite visual cortex for the other eye, even when the other eye is closed. The absence of visual imagery from the blindspot does not intrude into [[consciousness]] with one eye closed, because the corresponding [[visual field]] locations of the optic discs in the two eyes differ.
   
Common causes of scotomata include demyelinating disease such as [[multiple sclerosis]] (retrobulbar neuritis), toxic substances such as [[methyl alcohol]], [[ethambutol]] and [[quinine]], nutritional deficiencies, and [[blood vessel|vascular]] blockages either in the retina or in the optic nerve. [[Scintillating scotoma]] is a common visual [[Aura (symptom)|aura]] in [[migraine]]. Less common, but important because sometimes reversible or curable by [[surgery]], are scotomata due to [[tumor]]s such as those arising from the [[pituitary gland]], which may compress the optic nerve or interfere with its blood supply.
+
The presence of the scotoma can be demonstrated subjectively by covering one eye, carefully holding [[fixation]] with the open eye, and placing an object (such as your thumb) in the [[Human anatomical terms#Anatomical directions|lateral]] and [[horizontal]] visual field, about 15 degrees from fixation (see the [[blind spot (vision)|blind spot]] article). The size of the [[monocular]] scotoma is surprisingly large - 5x7 degrees of [[visual angle]].
   
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 bi-temporal hemicentral scotomatous hemianopia. This type of visual field defect tends to be very eloquent symptom-wise but often evades early objective diagnosis, as it is more difficult to detect by cursory clinical examination than the classical or text-book bi-temporal peripheral hemianopia and may even elude sophisticated electronic modes of visual field assessment.
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The term scotoma is also used [[metaphor]]ically in [[psychology]] to refer to an individual's inability to perceive [[personality trait]]s in themselves that are obvious to others.
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==Presentation of pathological scotoma==
  +
Symptom-producing or [[pathology|pathological]] scotomata may be due to a wide range of disease processes, affecting either the [[retina]] (in particular its most sensitive portion, the [[macula]]) or the [[optic nerve]] itself. 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. Even a small scotoma that happens to affect central or [[macula]]r vision will produce a severe visual [[Disability|handicap]], whereas a large scotoma in the more [[Peripheral vision|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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==Causes==
  +
Common causes of scotomata include [[demyelinating]] disease such as [[multiple sclerosis]] ([[retrobulbar neuritis]]), toxic substances such as [[methyl alcohol]], [[ethambutol]] and [[quinine]], [[nutritional deficiencies]], and [[blood vessel|vascular]] blockages either in the retina or in the optic nerve. [[Scintillating scotoma]] is a common visual [[Aura (symptom)|aura]] in [[migraine]].<ref>"Possible Roles of Vertebrate Neuroglia in Potassium Dynamics, Spreading depression, and migraine", Gardner-Medwin, ''J. Exp. Biology'' (1981), 95, pages 111-127 (Figure 4).</ref> Less common, but important because sometimes reversible or curable by [[surgery]], are scotomata due to [[tumor]]s such as those arising from the [[pituitary gland]], which may compress the optic nerve or interfere with its blood supply.
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  +
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 hemianopsia|bi-temporal hemicentral scotomatous hemianopia]]''. This type of visual field defect tends to be obvious to the person experiencing it, but often evades early objective [[medical diagnosis|diagnosis]], as it is more difficult to detect by cursory clinical examination than the classical or text-book bi-temporal peripheral hemianopia and may even elude sophisticated electronic modes of visual field assessment.
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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]].
   
 
==See also==
 
==See also==
 
===Detection===
 
===Detection===
 
*[[Amsler grid]]
 
*[[Amsler grid]]
  +
*[[Horizontal eccentricity]]
 
*[[Perimetry]]
 
*[[Perimetry]]
 
*[[Visual field test]]
 
*[[Visual field test]]
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===Types===
 
===Types===
 
*[[Binasal hemianopsia]]
 
*[[Binasal hemianopsia]]
 
*[[Bitemporal hemianopsia]]
 
*[[Bitemporal hemianopsia]]
 
*[[Blind spot (vision)|Blind spot]]
 
*[[Blind spot (vision)|Blind spot]]
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*[[Scintillating scotoma]]
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*[[Cortical spreading depression]]
   
[[Category:Ophthalmology]]
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==References==
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{{reflist}}
   
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{{Eye pathology}}
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[[Category:Visual disturbances and blindness]]
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[[Category:Neurological disorders]]
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{{enWP|Scotoma}}

Latest revision as of 18:58, November 11, 2009

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Scotoma
ICD-10 H534, H531
ICD-9 368.4, 368.12
OMIM [1]
DiseasesDB [2]
MedlinePlus [3]
eMedicine /
MeSH {{{MeshNumber}}}

A scotoma (Greek for darkness; plural: "scotomas" or "scotomata") is an area or island of loss or impairment of visual acuity surrounded by a field of normal or relatively well-preserved vision.

File:NormalField.jpg
Example image showing normal field of vision.
File:CentralScotoma.jpg
Example image showing small, deep central scotoma, as may be caused by age-related maculopathy.
File:ConstrictedField.jpg
Example image showing a peripheral ring scotoma, as may be caused by retinitis pigmentosa.
File:ScintillatingScotoma3.jpg
Example of a scintillating scotoma, as may be caused by cortical spreading depression.

Every normal mammalian eye has a scotoma in its field of vision, usually termed its blind spot. This is a location with no photoreceptors, where the retinal ganglion cell axons that comprise the optic nerve exit the retina. This location is called the optic disc. When both eyes are open, visual signals that are absent in the blind spot of one eye are provided from the opposite visual cortex for the other eye, even when the other eye is closed. The absence of visual imagery from the blindspot does not intrude into consciousness with one eye closed, because the corresponding visual field locations of the optic discs in the two eyes differ.

The presence of the scotoma can be demonstrated subjectively by covering one eye, carefully holding fixation with the open eye, and placing an object (such as your thumb) in the lateral and horizontal visual field, about 15 degrees from fixation (see the blind spot article). The size of the monocular scotoma is surprisingly large - 5x7 degrees of visual angle.

The term scotoma is also used metaphorically in psychology to refer to an individual's inability to perceive personality traits in themselves that are obvious to others.

Presentation of pathological scotomaEdit

Symptom-producing or pathological scotomata may be due to a wide range of disease processes, affecting either the retina (in particular its most sensitive portion, the macula) or the optic nerve itself. 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. Even a small scotoma that happens to affect central or macular vision will produce a severe visual handicap, 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.

CausesEdit

Common causes of scotomata include demyelinating disease such as multiple sclerosis (retrobulbar neuritis), toxic substances such as methyl alcohol, ethambutol and quinine, nutritional deficiencies, and vascular blockages either in the retina or in the optic nerve. Scintillating scotoma is a common visual aura in migraine.[1] Less common, but important because 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 bi-temporal hemicentral scotomatous hemianopia. 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 text-book bi-temporal peripheral hemianopia and may even elude sophisticated electronic modes of visual field assessment.

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.

See alsoEdit

DetectionEdit

TypesEdit

ReferencesEdit

  1. "Possible Roles of Vertebrate Neuroglia in Potassium Dynamics, Spreading depression, and migraine", Gardner-Medwin, J. Exp. Biology (1981), 95, pages 111-127 (Figure 4).



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