A scotoma It is an alteration that is characterized by the experimentation of a zone of blindness in the visual field of the person. The condition causes partial blindness, as it does not limit vision completely, and can be both temporary and permanent.
On the other hand, it is necessary to take into account that the scotoma can be a normal situation in people, or a pathological condition. When it comes to this second case, the alteration is usually caused by a lesion in the retina of the optic nerve.
In this sense, today two main types of scotoma have been described: the negative scotoma that is not perceived by the subject and the positive scotoma that is perceived by the person.
Likewise, these alterations can also be divided according to the affected visual field, and according to the causes that originate the visual disorder. This article reviews the main characteristics of scotomas, and explains the types and pathologies that can cause them..
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The scotoma is an alteration of the sight that generates blind spots or "dark holes" in the visual field of the person.
This alteration is characterized by affecting only specific regions of the visual field. In this way, although they cause complete blindness in certain points of the visual field, they do not cause a total loss of vision..
The most common is that a person with a scotoma can see with relative normality, but visualizes black dots in their field of vision, a fact that limits their ability to visualize the environment.
This alteration can be both temporary and permanent. That is, it can appear during certain periods of time or extend chronically. However, the most common is that it constitutes a temporary condition.
On the other hand, scotomas are characterized by being both a normal condition and a pathological condition. That is, a person can experience them without any type of pathological process and a subject can suffer them due to a certain disease.
In most cases, scotomas are caused by injury to the retina of the optic nerve. This lesion prevents the reception of visual stimuli in specific regions of the retina, so that the visual information that is transmitted to the brain presents black dots in some areas of the visual field.
However, the scotoma can also be caused by a lesion in the visual areas of the brain. In this case, the retina works properly but when the brain processes the information captured, it generates black dots in certain parts of the visual field..
Finally, this condition can also be due to a vascular disorder. The most typical case of scotoma due to vascular alteration is usually witnessed during migraine attacks.
In general, scotomas can be classified into two large groups. Negative scotomas and positive scotomas.
The negative scotoma is characterized by not being perceived by the subject. That is, the person who suffers from this alteration does not detect any blindness condition or visualize black dots in his field of vision..
On the other hand, the positive scotoma constitutes a totally opposite alteration. In this case, the person does perceive alterations in the visual field and is able to detect the elements referring to the scotoma that have been previously commented..
Despite the fact that these are the two main classifications of scotoma, several types of this condition have currently been described that allow a greater delimitation of its properties..
In this sense, the types of scotoma are elaborated based on several criteria such as the location of the blindness in the visual field, the injured anatomical regions or the pathologies that directly cause the suffering of the visual disorder. The main types of scotoma that have been described today are:
The blind spot is a physiological and absolute scotoma, so it is usually included within the negative scotomas that are not perceived by the person.
This alteration corresponds to the projection of the papilla (region of the retina that does not contain photoreceptors) in the visual field.
The blind spot usually measures about seven degrees vertically and about five degrees horizontally and is usually located about fifteen degrees temporally and one degree below the horizontal mean raphe.
This alteration constitutes a visual deformation of the blind spot. It is usually caused by a slightly curved early arcuate defect.
These conditions include a small group of isolated scotomas that occur in the circular area, between ten and twenty degrees that surround the point of attachment of the retina. It is common for these scotomas to appear in the upper sector and as the pathology progresses, a superior arched scotoma is formed.
These visual disturbances affect fixation and the surrounding field. They are one of the types of papillomacular notches and are characterized by being the most common and those that produce a greater decrease in vision.
They correspond to a type of caecal scotoma that affects the area of the normal blind spot. In this case, the alteration extends towards the fixation area and appears to affect the papillomacular bundle..
The Bjerrum scotoma occurs in the arcuate area, due to the union of paracentral scotomas. They usually start in the upper pole and affect the central area of the visual field.
The nasal step occurs due to injury to the arcuate nerve fiber bundle of the retina. This alteration can generate asymmetries in the upper and lower poles, as well as along the raphe.
Visual disorders can be caused by a wide variety of pathologies and situations, which is why scotomas have a very varied etiology.
The most normal thing is that these alterations occur as a direct or indirect effect of a certain pathology. For this reason, it is considered that scotomas are a group of symptoms belonging to a great variety of both visual pathologies and conditions not related to vision..
Specifically, the main diseases that are related to these visual disturbances are:
Presbyopia is a condition that causes a marked reduction in the ability to focus on objects. It is a highly age-related disorder that usually occurs among people over 40 years of age. It constitutes a degenerative pathology and, in some cases, it can cause the appearance of scotomas.
Cataract is a pathology that generates partial or total opacity of the lens, a fact that causes light to scatter inside the eye and cannot focus on the retina, thus producing diffuse visual images.
This condition has several causes although it is usually strongly attributed to age and can be treated by surgery.
Glaucoma is one of the main eye diseases. It is characterized by generating pressure inside the eye that causes poor vision at night. Likewise, it causes the experimentation of blind spots and loss of vision on either side of the visual field..
Diabetic retinopathy is a complication of diabetes and one of the leading causes of blindness worldwide. This condition appears due to damage to the small blood vessels in the retina. It can cause bleeding in this region of the visual system and usually causes both scotomas and total blindness..
Macular degeneration is an eye disorder in which the central and acute vision is slowly and progressively destroyed, a fact that hinders the specific vision of people.
It is the most common visual pathology among people over 60 years of age and can cause blurred vision, distorted vision, faded perception of colors and scotomas.
Another important cause of scotomas lies in the infectious or inflammatory processes of the retina, as well as eye damage..
In these cases, the condition may be temporary and disappears when the infectious process that causes the visual disturbance stops..
Floaters are small particles that float through the eye. They are usually short-lived and harmless, but in some cases they can be a sign of retinal detachment..
Retinal detachment is an alteration produced by a separation of the light-sensitive membrane (the retina) from its supporting layers located at the back of the eye..
This condition usually causes blurred vision, flashes of bright light, floaters in the eye, and blindness in part of the visual field of one eye..
Optic neuritis is an inflammation of the optic nerve due to infection or the direct effect of multiple sclerosis. It usually causes pain in the eye and blindness in certain regions of the visual field.
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