Eye diseases: what is scotoma?

By Cristiano Antonino On May 24, 2023

A scotoma occurs when a certain area of the visual field can no longer perform its normal function, partially or totally obstructing vision

These are black or coloured spots that appear in the visual field impairing vision.

What is scotoma

This lacunar defect in the visual field can be relative, when it is linked to a reduction in retinal sensitivity, or absolute, when the disappearance of retinal sensitivity is total.

The scotoma is a visual disorder directly linked to even serious pathologies of the optic nerve that should not be underestimated.

It is important, therefore, to undergo regular eye examinations, as only a specialist can verify the health of the eyes.

In the case of scotoma, for example, it is practically impossible to notice until it reaches the terminal stage, when vision is almost completely impaired.

Different types of scotoma

Scotoma can have different characteristics and only a careful analysis by the eye doctor can reveal what type of impairment one is dealing with.

The types of scotoma vary according to their classification:

physiological scotoma, also called Mariotte’s blind spot, in which the area where vision is impaired corresponds to the point where the optic nerve emerges from the retina
central scotoma, which compromises the central part of the eye, the part used to fixate objects
paracentral scotoma, in which the area of reduced light sensitivity involves the area around the macula
centrocentral scotoma, when a central scotoma gradually enlarges, involving the macula and blind spot
annular scotoma, with a circular shape, usually detectable between 20° and 40° from the fixation point
arciform scotoma, also called Bjerrum scotoma, which has an arcuate, crescent shape
scintillating scotoma, when there is a small dark spot in front of the eyes from which light trails emanate, is often accompanied by migraine
peripheral scotoma, generally linked to retinopathies and chorioretinopathies

The scotoma can also be differentiated according to its nature

positive scotoma, represents a variable coloured spot superimposed on the observed image
negative scotoma, is perceived as a vision defect, a dark spot that does not allow the visualisation of fixed objects.

Symptoms of scotoma

In most cases it is asymptomatic, at least at first.

When the patient begins to perceive a loss of vision, we are already facing a terminal phase of the disorder and thus of the disease associated with it.

We therefore speak of symptomatic scotoma when peripheral vision is impaired and, even more so, central vision is impaired, so that the sufferer can no longer see well.

How scotoma is diagnosed

Scotoma is diagnosed by an eye examination and only in rare cases is the patient aware of the problem, when it is at a very advanced stage and significantly impairs vision.

The test used to detect the presence of a scotoma is that of the visual field, peripheral and central, in which the doctor can measure the vision of the space surrounding the eye thanks to special instruments that send light stimuli to the eye.

After this test, the ophthalmologist can arrange for more specific tests to confirm the diagnosis.

How the visual field test is carried out

During the ophthalmic examination, the doctor subjects the patient to a visual field test, a non-invasive check useful for detecting glaucoma in particular – of which scotoma represents the damage – but also other diseases of the retina, central nervous system and optic nerve.

The patient places his or her chin on the instrument, the unexamined eye is covered, then the instrument sends out light stimuli to be recognised by pressing a button, trying never to shift the gaze but always looking straight ahead.

Causes of scotoma

There can be several abnormalities of the eye that lead to this visual lacunar defect.

The most common is certainly glaucoma, which, due to increased eye pressure, impairs vision.

Other causes are:

retinal detachment
diabetic retinopathy
cataract
migraine with aura
optic nerve disorders (opticopathies, neuritis)
retinoblastoma
macular pathologies

In other cases it is caused by factors that do not directly affect the eye, such as cardiac or vascular problems, brain tumours or even food poisoning or medication intake.

Infections such as toxoplasmosis can also impair vision and trigger central scotoma in particular.

Glaucoma and scotoma

As we said, scotoma manifests itself as damage due many times to glaucomatous disease.

Glaucoma is due to an increase in intraocular pressure, which exceeds the range and goes beyond 21-22 mmHg, and can be congenital, i.e. already present at birth, or occur over the years due to an increase in pressure caused by various factors, not only related to the eyes but also external.

Moreover, after the age of 40, eye pressure increases by 1 mmHG every 10 years, which naturally impairs the quality of vision.

How scotoma is treated

There is no specific treatment for scotoma, but more importantly, as there are different types of scotoma and different underlying causes, the medical and scientific approach varies from case to case.

When scotoma is caused by glaucoma, opticopathies or in the presence of nerve cell damage, there is not much to be done except to recover part of the lost visual function with rehabilitation.

In the case of glaucoma, for example, eye pressure can be controlled with hypotonic eye drops.

If the scotoma is caused by a problem with the crystalline lens, as in the case of cataracts, the best solution is surgery that removes the lens itself and replaces it with an intraocular artificial lens.

In some cases, particularly those due to retinal vascular disease, scotoma can be treated with drug therapy, e.g. using anti-coagulants, anti-aggregants and thrombolytics.

When scotoma is due to diseases that occur with age, such as macular degeneration (AMD), drugs or supplements can be used depending on the type of maculopathy.

Finally, if the cause of the scotoma is retinal detachment, surgery is performed to reposition the retinal tissue in its place.

Scotomas are black or coloured spots that appear in the visual field impairing vision.

They are caused by certain eye diseases that affect the retina, macula or optic nerve, such as cataracts, retinal detachment or glaucoma, and can be treated by acting on the origin that triggered them.

They are usually asymptomatic, unless vision is now completely impaired, and only an eye examination with a visual field test can diagnose them with certainty.

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