Scotoma

Description:

Scotoma (scotoma, Greek skotuma, from skotos darkness) — the defect of a field of vision which is not reaching its borders. Distinguish physiological and pathological scotomas.

Scotoma symptoms:

Physiological scotomas in the form of a blind spot (Marriott's spot) and angioscotomas are observed normal and are found at a research of a field of vision. A blind spot — the small site of a field of vision where completely there is no light perception; corresponds to a projection of an optic disk in which there are no visual receptors. The angioscotomas reminding in a tree branch form are always connected with a blind spot and caused by existence in a retina of the vessels located in front from its light-sensitive elements. Physiological scotomas at solid vision subjectively are not perceived since fields of vision of the right and left eye are partially blocked. It is promoted by also constant involuntary micromovements of eyeglobes. Thanks to these movements, and also an arrangement of a blind spot in paracentral departments of a field of vision physiological scotomas often are not felt also at monocular sight.

Pathological scotomas arise mainly at damages of a retina, an idiovascular cover of an eye, visual conduction paths and the centers. Carry the physiological scotomas which are also increased and changed in a form as a result of various pathological processes to pathological (for example, the increased blind spot at a congestive nipple, neuritis of an optic disk, a back staphyloma against the background of short-sightedness of high degree; the retinas increased at periphlebites, a diabetic retinopathy, glaucoma and other pathology of an angioscotoma).

Among pathological scotomas distinguish positive and negative. Positive (subjective) scotomas call such defects of a field of vision which are seen by the patient as the dark stain closing a part of the considered subject. Existence of positive scotoma is caused by shielding of light-sensitive elements of a retina the pathological centers located before it that can be observed at defeat of inside layers of a retina or a vitreous just before a retina. Does not notice negative scotomas of the patient; they are found only at a research of a field of vision. Usually such scotomas arise at damage of an optic nerve; at the same time is absent or visual perception is weakened.

On intensity (density) of scotoma divide on absolute and relative. Absolute scotoma call such defect of a field of vision in the field of which visual perception completely is absent, i.e. the test object shown at a research of a field of vision is not visible to investigated. Relative scotomas are characterized by weakening of visual perception in comparison with the neighboring sites of a field of vision: the white test object shown at a research of a field of vision is visible to less light, and color less saturated. In view of brightness and size of a test object it is possible to recognize scotoma absolute (at a research by means of less bright or the smaller size of a test object) or relative (when using brighter or the bigger size of a test object). Therefore at a research of scotoma it is important to note the size and brightness of a test object. Gradual decrease in intensity of scotoma towards not changed sites of a field of vision testifies to freshness of pathological process and its tendency to progressing. Sharp transition from area of scotoma to a zone of normal visual perception is characteristic for finished or стабилизировававшегося pathological process.

In a form pathological scotomas can be oval, round, wedge-shaped the arc-shaped, ring-shaped (annulyarnny), etc. For example, the arc-shaped  is characteristic mainly of glaucoma, ring-shaped — of a pigmental degeneration of a retina. On localization distinguish the central, paracentral, pericentral and peripheral pathological scotomas. Central  are located in the central part of a field of vision and include a fixing point. They are observed at damages of a retina in the field of a macula lutea (for example, makulodistrofiya) or at the pathological process which is localized in the field of a papillomakulyarny bunch of an optic nerve (for example, at axial neuritis). In the first case of scotoma call positive, in the second — negative. Paracentral was located in paracentral departments of a field of vision, adjoin from any party a fixing point. Pericentral surround a fixing point, without being closed with it. Typical pericentral scotoma is Byerrum's scotoma dugoobrazno surrounding a point of fixing and merging with a blind spot. Byerrum's scotoma is a precursory symptom of glaucoma and has a certain predictive value since it increases at increase in intraocular pressure and decreases or disappears at its decrease (functional scotoma). Two scotomas of Byerrum form the ring-shaped scotoma characteristic of late stages of glaucoma. The peripheral scotomas which are located in peripheral departments of a field of vision are characteristic of a chorioretinitis, a retinitis, dystrophic processes in peripheral departments of a retina.

The bilateral scotomas located in of the same name or heteronymic half of a field of vision are called gemianopichesky scotomas, or hemianopsias. At small focal defeats of visual pathways in the field of visual decussation geteronimny (heteronymic) bitemporal are observed, as a rule, binazalny gemianopichesky scotomas are more rare. At localization of the small pathological center above visual decussation (visual tracts, the central part of a visual way, the subcrustal and cortical visual centers) the gomonimny (unilateral) paracentral or central gemianopichesky scotomas arising on the party opposite to localization of the pathological center develop.

Scotoma reasons:

Scotomas develop at many diseases of an eye: neuritis of an optic disk, a diabetic retinopathy, glaucoma, at a pigmental degeneration of a retina, a chorioretinitis, a retinitis, dystrophic processes in peripheral departments of a retina.

Treatment of Scotoma:

Treatment of a basic disease is carried out.