Scotoma 849874 217062010 2008-06-04T13:09:21Z DavidMBarron 7244334 Added metaphorical use of the term. {{Infobox_Disease | Name = {{PAGENAME}} | Image = | Caption = | DiseasesDB = | ICD10 = {{ICD10|H|53|4|h|53}}, {{ICD10|H|53|1|h|53}} | ICD9 = {{ICD9|368.4}}, {{ICD9|368.12}} | ICDO = | OMIM = | MedlinePlus = | eMedicineSubj = | eMedicineTopic = | 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]]. [[Image:NormalField.jpg|thumb|Example image showing normal field of vision.]] [[Image:CentralScotoma.jpg|thumb|Example image showing small, deep central scotoma, as may be caused by [[age-related maculopathy]].]] [[Image:ConstrictedField.jpg|thumb|Example image showing a peripheral ring scotoma, as may be caused by [[retinitis pigmentosa]].]] [[Image:ScintillatingScotoma3.jpg|thumb|Example of a [[scintillating scotoma]], as may be caused by [[cortical spreading depression]].]] 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 photoreceptors, where the retinal ganglion cell axons that comprise the optic nerve exit the retina. This location is called the optic disc. The blindspot does not intrude into [[consciousness]] because the corresponding visual field locations of the optic discs in the two eyes differ: The visual signals that are absent in one eye are sent to the cortex by signals from the other eye. The term is also used metaphorically in the field of psychology, in reference to an individual's inability to perceive personality traits in themselves that are obvious to others. 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 (vision)|blind spot]] article). The size of the monocular scotoma is surprisingly large - 5x7 deg of visual angle. ==Presentation== 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 because of the normal reduced visual resolution in the peripheral visual field. ==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. 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. In a pregnant woman, scotomata can present as a symptom of severe pre[[eclampsia]], 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== ===Detection=== *[[Amsler grid]] *[[Perimetry]] *[[Visual field test]] ===Types=== *[[Binasal hemianopsia]] *[[Bitemporal hemianopsia]] *[[Blind spot (vision)|Blind spot]] *[[Scintillating scotoma]] *[[Cortical spreading depression]] ==References== <references/> {{Eye pathology}} [[Category:Ophthalmology]] [[Category:Neurological disorders]] [[de:Skotom]] [[es:Escotoma]] [[fr:Scotome]] [[it:Scotoma]] [[pt:Escotoma]] [[sr:Скотом]]