Scotoma

Hanna Rutkowski is a freelance writer for the medical team.

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The scotoma (visual field loss) describes visual disturbances occurring in an area of the visual field. Sudden changes in color, flashes of light, dark spots are the most common forms of scotoma. In the worst case, those affected only see the outlines of their surroundings. Visual field deficits represent an ophthalmological emergency when they first occur! Read here what can trigger a scotoma and what you should do about it.

Scotoma: description

A scotoma is a defect in the visual field.

The field of vision is that part of the environment that can be visually captured when the head is upright and the eyes are looking straight ahead. An area of almost 180 degrees to the right and left can be perceived with both eyes (binocular) at the same time. A range of around 70 degrees can still be seen downwards, and 60 degrees upwards. The area in the center where the fields of vision of both eyes intersect is shown most sharply. In the outer area of the field of vision, however, the perception becomes increasingly blurred, patterns and colors can no longer be recognized exactly.

A failure in this field of vision - a scotoma - can make itself felt very differently depending on the cause: Flashes of light, small, dancing spots (floaters = "flying flies"), color changes, dark spots and even total blindness can occur. Doctors differentiate between relative and absolute scotoma and between positive and negative scotoma:

relative scotoma: objects in the area of the scotoma are weakened.
absolute scotoma: objects are not recognized.
positive scotoma: the patient sees additional shapes and structures such as flashes of light or dark spots. The scotoma can therefore be perceived by the patient himself. Therefore one speaks of a subjective scotoma.
Negative scotoma: The scotoma can only be determined by ophthalmological examinations. This is why one speaks of an objective scotoma.

There are also some special forms such as central scotoma (when the optic nerve is inflamed) or heminanopia (partial visual field loss).

Natural limits of the field of vision

Some visual field boundaries are natural and anatomically given. For example, anatomical structures such as the nose, cheeks or eyebrows limit our field of vision. And the exit point of the optic nerve on the back wall of the eyeball forms a scotoma, which is known as the “blind spot”. Since there are no visual receptors in this small area, objects that are at a certain angle to the blind spot cannot be seen. However, this is compensated for by the other eye, so that we do not even perceive the blind spot.

Scotoma: causes and possible diseases

A scotoma can have different causes. Sometimes there is a migraine with an aura behind it (see below: "Scotoma in migraine"). However, if the visual field loss occurs for the first time and without migraines, it is very likely that serious illnesses are hidden behind it, which should be treated immediately by a doctor. Some examples:

Macular degeneration

Age-related macular degeneration (AMD) manifests itself as an increasing loss of visual acuity with increasing age. Tissue on the retina is destroyed, which in the advanced stages can even lead to blindness. The field of view is not narrowed, but sharp vision of centrally located objects is no longer possible. The environment is often perceived as if through a "gray veil".

Glaucoma (glaucoma)

In glaucoma - due to increased intraocular pressure - the retina and optic nerve are destroyed. One consequence is the scotoma, which is often discovered late because it first appears on the outside of the field of vision and is compensated for by the other eye.

Diseases of the optic nerve

Inflammations (e.g. inflammation of the optic nerve), tumors, increased intraocular pressure and circulatory disorders of various causes can press on the optic nerve and permanently damage it. Visual field losses up to complete blindness are the possible consequences.

Retinal detachment

If the light-sensitive layer of the retina becomes detached from the back wall of the eyeball, this represents an ophthalmological emergency. Typical signs of retinal detachment are twitching flashes of light, black or reddish points in front of the nose and increasingly larger visual field losses. In this case, an ophthalmologist or a hospital should be visited immediately, as permanent blindness is threatened!

Retinal detachment can be caused by an injury (e.g. blow to the eye) or by various diseases (such as diabetic retinopathy).

stroke

A stroke occurs either as a result of hemorrhage or a vascular occlusion in the brain. In both cases, brain tissue dies. Common first signs are double vision and visual field loss, hemiplegia of the body and speech disorders.

Brain tumors

Masses in the brain, especially if they are in the course of the optic nerve, can also cause scotomas. A visual field loss is often the first sign of disease in tumors in the back of the brain.

Scotoma in migraines

Migraines are a major nuisance for those who suffer (mostly women): attack-like, severe, usually one-sided headaches that can persist for between four and 72 hours. Doctors differentiate between migraines with and without aura:

The migraine without aura is by far the more common type. Increasingly strong, pulsating headaches develop, which usually only occur on one side of the head. The headache, which lasts up to 72 hours, is often accompanied by vomiting and nausea. An additional sensitivity to noise and light forces the patient to retreat to darkened, quiet rooms.

In migraines with aura, the headache is preceded by impaired vision and other sensory perceptions and is referred to as "aura":

Seeing colorful flashes of light
Seeing jagged lines (fortifications)
Balance disorders
Speech disorders
Changes in feeling such as tingling in the arms and legs

The aura is perceived and experienced differently from patient to patient. Usually these symptoms do not last more than 40 minutes.

The so-called ciliated scotomas occupy a special position, which can occur both completely without migraines and in the context of a migraine with aura. This leads to an increasing glare effect in the more external field of vision - almost as if one were looking into the light. The visual impairment increases, but does not affect the entire field of vision. Sharp viewing or reading is no longer possible. Here, too, the symptoms do not last longer than 30 minutes and can be accompanied by vomiting or nausea.

Scotoma: when do you need to see a doctor?

If you lose your visual field for the first time, you should consult a doctor immediately! It can - but does not have to - be due to a serious illness. An immediate doctor's visit is also advisable in the following cases:

if you have repeatedly had a migraine with aura, but the scotoma is different than usual this time or the headache does not occur
with increasingly larger scotoma
when you have the impression that a curtain is being pulled up from the bottom up in front of your eyes
when everything around you looks like it's covered in a gray veil
when you can only see outlines
with flashes of light or black areas in the field of view
if you also experience nausea, vomiting, confusion, speech disorders or other complaints

Scotoma: what does the doctor do?

If the visual field loss occurs for the first time and without further complaints, the first point of contact is the ophthalmologist. The first step is a detailed interview to collect the medical history (anamnesis). The doctor asks you to describe your symptoms in detail.He will also ask whether you have had these symptoms in the past and whether you are aware of any underlying diseases (e.g. high blood pressure, glaucoma, diabetes mellitus). It is also important for the ophthalmologist to know whether you are a (heavy) smoker.

This is followed by ophthalmological examinations such as:

Determination of visual acuity and, if necessary, comparison with visual aids that have already been used (such as glasses)
Slit lamp examination: With the help of a special microscope (with a slit lamp), the ophthalmologist can enlarge and assess all structures of the eye - starting from the front part with the cornea and lens to the retina and the fundus. Numerous eye diseases that can trigger a scotoma can be uncovered in this way.
Eye endoscopy (fundoscopy): Here the doctor can assess the fundus with the point of sharpest vision (macula). This will help diagnose macular degeneration.

Depending on the cause, further targeted examinations can follow. This includes, for example, optical coherence tomography (OCT). With the help of a laser, an exact image of the retina is created. This is helpful, for example, in the diagnosis and follow-up of glaucoma and macular degeneration. With perimetry, on the other hand, the outline of the field of view is precisely measured.

If signs of a stroke or other illness appear in addition to the scotoma, an interdisciplinary diagnosis in cooperation with other doctors is necessary, if not life-saving. If a stroke is suspected, this includes neurological examinations and computed tomography of the skull.

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