A scotoma is a break or interruption in the visual field.
The plural of the word is not scotomas, as one might think, but it is Ecotomata.
A scotoma may occur in one eye or both, in the center or at the outer edges of the visual field, and may occur alone or there may be several.
It is characterized by partial, permanent or temporary blindness.
The patients present degeneration, nebulosity or even absolute absence of vision surrounded by an area with normal vision. The view can be affected by an injury anywhere in the visual pathway.
It is a complex degeneration and requires a high degree of diagnostic ability, multiple lesions from the occipital lobe of the brain to the eyes may be responsible for the development of scotomas.
Causes of the scotoma
The causes of the scotoma should be determined first where the lesion is, if the scotoma is limited to one eye, doctors may assume that the lesion is just before the optic chiasm since the damage of the optic fiber is limited to that particular eye.
This is very useful to determine the progression of glaucoma and pseudotumor cerebri. The Scotomas are created in such a way that they coincide with the anatomical area and the affected projection area. If the patient has a supra-nasal retinal detachment, the scotoma is an infratemporal scotoma.
If the damage is to the macula, the scotoma is central. Glaucoma destroys the axons of the upper and lower temporal poles of the optic disc resulting in an arc-shaped scotoma resembling a Turkish scimitar.
The scotomas can also occur from optic neuritis , ischemic optic neuropathy , optic disc drusen and artery occlusion or branch vein of the retina.
Brain tumors, trauma, metabolic disorders or thromboembolic processes are on this inclusive list of the scotoma cause.
Approximately half of the optical fibers originate in the ganglion that serves the macula. The damage here causes a central scotoma. If it is prolonged, the ischemic nature causes the disc to turn pale and it is noticeable that it is irreversible. The presence of massive lesions in the sellar region causes a temporary hemianopsia in each eye.
If tumors are hemangiomas that are just in front of the optic chiasm, they will produce a combined scotoma that is characterized by optic neuropathy in one eye and superior temporal cut in the other eye.
Asymmetric compression of the optic chiasm by a pituitary adenoma, meningioma , craniopharyngioma or aneurysm results in a bitemporal hemianopsia. The insidious development of this condition causes it to be detected only when the doctor examines each eye separately.
It is difficult to locate a poschiasmal lesion since it could be anywhere along the optic tract, the geniculate body, the optic radiations and the occipital lobe.
A unilateral posquiasmal lesion will leave the visual acuity in the unaffected eye. The lesions in the optical radiation will give rise to ocular defects that are not localized and incongruent in both eyes.
The damage to the optical radiations in the temporal lobe will result in a quadrilateral homonymous hemianopsia superior. The lesions of the optical radiations in the parietal lobe will result in a lower homonymous quadrangular hemianopsia.
Lesions in the occipital lobe will result in mixed congruent eye defects and in both eyes. Ischemia is also implicated in the development of total homonymous hemianopsia, the occlusion of the posterior cerebral artery results in this defect.
The destruction of the occipital lobe produces total blindness, this is different from the pre-chiasmatic loss due to the presence of intact pupillary responses.
Treatment of the scotoma
Given the variety of injuries that occur in the pathway of the visual tract, it is the doctor’s job to determine the exact location of the injury or, in the absence of such physical injuries, the medical conditions that could be the cause of such disruption in the visual fields.
It is imperative that the patient seek immediate medical attention since the treatment in the first hours of detection of the visual field effect preserves vision.
If the patient is delayed or the condition is intrinsically irreversible, these scotomas may persist. That is why we must have excellent units of education to improve people’s awareness of the devastating effects of scotoma.
The underlying causes of scotoma should be determined as soon as possible. In cases of tumors that affect any part of the visual pathways, a good anamnesis and a physical examination of the eyes plus a good radiological examination in the form of CT or MRI can help to locate the lesions.
Once identified, the treatment will include a precise surgical excision of the tumor. The prompt extirpation of these tumors will help correct the scotomas by relieving the effects of the mass on the pathway of the sensitive visual tract.
If the scotoma is not treated early, the damage will persist indefinitely and, until now, there are no medical therapies to correct visual field defects.
Hatch of a scotoma
It refers to a localized region of reduced vision that is bordered by brightly colored lights.
It indicates the appearance of migraine in many patients.
In this type of scotoma, dark spots can move around the eye, creating arcs of light or zig-zag patterns.
The appearance of alterations in the visual field can serve as warning signs or a special marker for people suffering from headaches caused by a migraine over the impending headaches.
Diagnosis of a scotoma
The diagnosis of this disease usually begins with a physical examination in the initial stages.
Doctors examine the eyes of sufferers and also ask them questions about their symptoms.
They are also asked about any other condition or eye surgery that they have recently suffered.
Medical tests used to detect this disorder include:
- Amsler grid, normally used to assess the central vision of the retina.
- Computerized perimetry, this test evaluates the sensitivity of the retina to light stimuli.
- Campimetry is a test of the visual field test.
- Horizontal eccentricity, it measures the time of visual reaction, since the stimulus arrives at the eye and the moment when it perceives it.
The differential diagnosis of this disease involves ensuring that the symptoms experienced by patients are those of Scotoma and not similar eye conditions, which may include:
- Optic neuritis
- Vascular disorders
- Degeneration of the retina.
- Thrombosis of the carotid artery.
- Optic atrophy
- High pressure in the retina.
Types of scotoma
There are several main types of scotoma.
Most are permanent, but there is a type of scotoma that is associated with a migraine and is temporary, often, is part of the headache aura, or a subtle change in perception that occurs before the migraine begins.
- Scintillating scotoma : This is the type of scotoma that occurs before the onset of a migraine. This scotoma appears as a blinking light in the form of an arc that invades the central visual field.
- Central scotoma : This scotoma is perhaps the most problematic type. It is a dark spot in the center of the field of vision. The remaining visual field remains normal, which often causes the patient to focus on the periphery or the outer limits of the field. This makes daily activities, such as reading and driving, very difficult to perform.
- Peripheral scotoma : This type of scotoma is a dark spot along the edges of the field of vision. While it interferes with normal vision and all the activities that depend on it, it is not as difficult to treat as a central scotoma.
- Hemianopic scotoma: With this type of scotoma, half of the visual field is affected by the dark spot. This can occur on either side of the center and can affect one or both eyes, but usually affects both. This is also sometimes called homonymous hemianopsia.
- Paracentral scotoma : This scotoma is a dark spot that occurs nearby, but not in the central visual field.
- Bilateral scotoma : This type of scotoma appears in both eyes and is caused by some type of brain tumor or growth. It is relatively rare.
In fact, scotomas are devastating. They are the result of any injury that affects the pathway of the visual tract.
These lesions can be the result of direct trauma, benign or malignant neoplasms with mass effects and cardiovascular hypertension. People need to be informed about these devastating effects so that rapid treatment can be initiated to preserve sight.