Cortical blindness is the older term from neurology that describes an acquired blindness that does not go back to a diseased eye, but to damage to the primary visual cortex in the brain. Commonly used synonyms are blind seeing and blindside. The latter term was coined by American physicians.
What is cortical blindness?
People who suffer from cortical blindness have fully functional eyes. Only the primary visual cortex in the brain cortex is damaged. The most common cause of this injury is a stroke. However, the description of this condition with the terms “blind vision” is not entirely correct. Cortical blindness prevents visual impressions from reaching the primary visual cortex in the brain, which enables conscious perception of the environment. For hyde syndrome guide, please visit deluxesurveillance.com.
The term “blind vision” is a popular term for people who are blind but act as if they can see. In cortical blindness, the various nerve pathways above the eye remain intact. They are responsible for forwarding the incoming optical stimuli to the brain. However, if the primary visual cortex is damaged, these optical stimuli are not transmitted and the human being is not able to consciously perceive his environment. The medical specialties are neurology and ophthalmology.
Causes
It is a cortical amaurosis, which is accompanied by the loss of visual perception with simultaneous extensive processes in the visual cortex. However, the pupillary reactions do not change. There is a bilateral loss of function of the primary visual cortex in the occipital lobe. Other causes are tumours, an ischemic cerebral infarction of the Arteriae cerebri posteriores (reduced blood flow in the cerebral artery) and all types of serious head injuries, for example a fracture of the base of the skull after an accident.
These patients no longer see their environment consciously, but show visual reflexes. At the back of the head is the visual cortex, the primary visual cortex responsible for assembling incoming visual signals into a consciously perceived image. This visual cortex is the computing center of the human sense of sight, so to speak. Patients with cortical blindness do in fact see something, they just don’t know it because the visual stimuli are not transmitted to consciousness via the primary visual cortex.
Symptoms, Ailments & Signs
Cortical blindness and the mental blindness closely related to it belong to the medical field of agnosia. This term comes from the Greek language and means “ignorance”. Soul blindness differs from cortical blindness in that objects are perceived but can no longer be assigned.
Sigmund Freud attributed both visual disorders to agnosia. With cortical blindness, there are no attention disorders, sensory defects, or cognitive disorders. The visual apparatus consists of the eye, the visual center and the optic nerves of the cerebral cortex. In cortical blindness, the functionality of the visual cortex fails completely. In legal terms, a person with this disease is considered blind, even though the eyes are not damaged.
Diagnosis & course of disease
The main symptoms are visual field defects in the temple area (temporal) or in the nasal area and the subsequent loss of visual perception. A crossed equilateral (homonymous) hemianopsia is typical of this type of disease. If there is a left-sided lesion of the visual cortex, the right halves of the face will fall out and vice versa. If the end of the tract or the geniculate body (medial knee hump in most of the diencephalon) is affected, the hemianopsia is complete in many cases, otherwise it is incongruent and incomplete.
The corresponding nerve fibers have not yet fully assembled. Some patients have more or less developed bilateral optic atrophy (degenerative disease of the optic nerve). The diagnosis is mainly made in experiments with flashes of light, which people who are blind to the cortex cannot consciously perceive, but can intuitively determine from which direction they are coming. However, they are unable to say why this is so.
Neurologists suspect that the people affected perceive the flashes of light in their subconscious. Since medicine has not yet been able to definitively determine how this process actually works, scientists have also undertaken experiments with healthy people. In this test series, the subject’s visual center was blocked using transcranial magnetic stimulation (TMS). These tested people did not consciously perceive the flashes of light either, but were also able to name the direction.
They could intuitively name colors presented to them correctly. The tests showed that they were unaware of the flashes and colors as they denied seeing anything at all. All people with cortical blindness have the same brain injuries or diseases. Further findings are based on the neurological and ophthalmological picture as well as on the evaluation of magnetic resonance imaging or computer tomography.
Complications
Cortical blindness can develop as a complication after surviving a stroke, bleeding in the visual cortex, brain tumors or traumatic brain injury. These diseases sometimes destroy the visual cortex, which can lead to blindness.
The pictures are taken through the normally functioning eyes. However, due to the damage to the bark, they can no longer be processed and made conscious. Serious complications that lead to life-threatening courses are not caused by cortical blindness. These are complications of the underlying disease.
Since the damaged cerebral cortex cannot be regenerated, curative treatment of cortical blindness is not possible. As a direct result of cortical blindness, the risk of suffering an accident can increase for those affected. This danger is particularly pronounced in a special form of cortical blindness in which the patient has no insight into the disease. This is the very rare Anton syndrome.
Patients affected by Anton syndrome cannot realize that they cannot see. The challenge for the treating physician is first of all to convince those affected of their blindness in order to prevent them from exposing themselves to the risk of suffering an accident. The work of persuasion is often very difficult and can only be achieved with the help of a combination of physiotherapy, psychotherapy and ergotherapy.
When should you go to the doctor?
Cortical blindness is a serious condition that requires medical attention. If vision is impaired after a stroke or other medical emergency, the doctor must be informed. Further visits to the doctor are indicated if vision continues to deteriorate even though treatment has been taken. Then there may be other faults that are best clarified in a timely manner. If treated early, the chances of recovery are relatively good. If left untreated, the visual disturbances can worsen. In the worst case, it can lead to complete blindness in one or both eyes. Therefore, an early diagnosis is important in any case.
Cortical blindness is treated by a neurologist or ophthalmologist. The actual therapy takes place in a specialist center for vision disorders, in which NEC, VRT and other vision therapies are offered. Close medical supervision is required during treatment. The doctor should be informed of any unusual symptoms and any side effects of the treatment so that the therapy can be adjusted accordingly.
Treatment & Therapy
The results of the investigations show that consciousness is generated within the visual cortex and that information processing also takes place without conscious perception. For this reason, the examined patients are able to say intuitively from which direction the light flashes come or to correctly name the presented colors. Further investigations show that people with a lesion of the visual cortex that has led to hemianoposia (hemianoposia) perceive emotional content of faces.
These are presented in the field of vision that is no longer consciously perceived. This process occurs through the activation of visual centers in the superior colliculus (four ridges of the midbrain). The unconscious perception is projected onto the limbic system, specifically the amygdala (paired core area of the brain of the medial part of the respective temporal lobe), which is important for the perception and processing of emotions.
Since the prognosis is usually that the visual field defects do not recede, the therapy is causally oriented. Stroke patients receive extensive physiotherapy and speech therapy, while tumor patients primarily receive radiation therapy. In the case of craniocerebral injuries, various rehabilitation measures are carried out in addition to the surgical intervention.
Aftercare
Cortical blindness does not meet the usual criteria for being blind. It is not congenital, but is caused by damage to the responsible brain area. The eyes themselves remain functional. In addition, those affected by cortical blindness are not (always) completely unable to see, they can only recognize outlines or shades.
Blindness occurs when certain sensory impressions are not processed correctly by the brain. This new situation is unfamiliar and stressful for patients. Follow-up care is necessary to learn how to deal with cortical blindness appropriately. Follow-up care takes place both in the neurological and in the ophthalmological framework. The extent to which cortical blindness can be treated depends on the causative disease.
In some patients, the ability to see is completely restored after the treatment has been completed, in other cases the visual impairment persists. The aftercare includes exercises for the eyes and for sensory processing. At the same time, the affected person learns to cope with cortical blindness in everyday life.
Depending on the degree of blindness, aids such as white canes are useful. If the illness causes additional psychological stress, psychotherapy should be considered. Visiting self-help groups for support can also have a positive impact on the sufferer’s quality of life.
You can do that yourself
Cortical blindness needs to be treated depending on the cause. A congenital disease severely restricts affected children, who require ongoing support during the early years of life. The legal guardians should try to get the child placed in a special kindergarten and later in a special school at an early stage.
Depending on the severity of cortical blindness, the lack of vision can be compensated for by glasses or another visual aid. Which measures make sense must be decided by a doctor depending on the severity of the condition. Acquired cortical blindness, for example after a stroke, requires regular training. Physiotherapy and speech therapy are important components of therapy. Cancer patients who have developed cortical blindness should take it easy at first. The symptoms usually disappear during radiation therapy. If this is not the case, visual aids must be worn. In individual cases, an operation on the eyes is possible.
If the cortical blindness is due to an injury to the skull or brain, physiotherapeutic measures are indicated. The patient should consult a specialist doctor, in addition to which he should independently carry out exercises to restore neurological abilities.
