Scotoma

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Related to central scotoma: optic neuritis, centrocecal scotoma

scotoma

[skə′tō·mə]
(medicine)
A blind spot or area of depressed vision in the visual field.

Scotoma

 

a blind area within the visual field, not affecting the surrounding area of the eye. Physiologic scotoma is that area of a healthy eye’s visual field corresponding with the optic disk, which does not have photoreceptors. Pathologic scotoma is a diagnostic symptom of many diseases, including retinitis and atrophy of the optic nerve. It is perceived as a dark spot (positive scotoma) or as a blank spot (negative scotoma) that can be detected only through special testing. During teichopsia (scintillating scotoma), which lasts 20–30 minutes, flickering is perceived along the eye’s periphery; the condition is usually accompanied by persistent headaches, nausea, and vomiting. Treatment of scotoma is directed toward the underlying disease.

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However, despite resolution of ocular signs, all reported residual mild central scotoma that was reflected on HVF as an area of subtle decrease in sensitivity in the central vision (Figure 1).
A computer and video display-based system for training eccentric viewing in macular degeneration with an absolute central scotoma.
Limited portability and the lack of access to a microperimeter or a tangent screen have led to the development of more simplified methods of testing the boundaries of a central scotoma for training in eccentric viewing.
Nilsson reported that, since the 1970s, a low-vision service in Sweden has been instructing patients in the use of a trained retinal locus (TRL) in a retinal area that is "more advantageous to reading," defined as above or below an absolute central scotoma as opposed to the left or right of the scotoma [25].
Patients with AMD and large absolute central scotoma can be trained successfully to use eccentric viewing, as demonstrated in scanning laser ophthalmoscope.
Visual acuity is often about 6/18 with a relative central scotoma, moderate photophobia and low-grade nystagmus; the foveal mosaic is irregular and reduced in density.
Some persons with central scotomas are able to adopt a regular and reliable fixation pattern; they look to the side or above the object of interest in a consistent way and thereby move the central scotoma out of the way.
In advanced cases, patients can report an absolute central scotoma, which can be corroborated by performing the Amsler grid test.
The most frequent of these diseases is age-related macular degeneration (AMD), in which foveal vision is often impaired by a central scotoma that impairs vision of fine detail and causes problems with reading and recognizing faces.
A central visual field analysis using SLO demonstrated a large central scotoma in the right eye with no established preferred retinal locus.
The natural development of the use of nonfoveal loci to improve potential sight in the presence of a central scotoma has been well described in the literature, with the anomalous fixation point described as a preferred retinal locus (Crossland, Sims, Galbraith, & Rubin, 2004; Fletcher & Schuchard, 1997; Macedo, Nascimento, Gomes, & Puga, 2007; Reinhard et al.
For instance, Wolffe (1995) reported that a group of youngsters were capable of painting landscapes or still lifes as accurately as sighted people, despite a severe central field loss that was due to a dense central scotoma.

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