Hemianopia is a polyethological disease that manifests itself by homonymous or heteronymous loss of visual fields. Characteristic symptoms: inability to see with certain halves of the eyes, visual hallucinations, phenomena of agnosia, prosopagnosia and “mental paralysis of vision” are possible. To make a diagnosis, it is necessary to conduct perimetry and computer campimetry. The etiology of hemianopsia can be established using Doppler ultrasound, computed tomography, magnetic resonance imaging and computed tomographic angiography (CT angiography). Etiotropic therapy is based on the elimination of the organic pathology that caused the hemianopsia clinic.
Hemianopia is a congenital or acquired pathology of vision that develops as a result of damage to brain structures. The congenital form often occurs against the background of other diseases of the central nervous system, isolated is extremely rare. After analyzing 100 cases of hemianopia, J. Smith in 39 cases revealed a deviation from the norm in the occipital lobe of the brain, in 33 – in the parietal lobe, in 24 – in the temporal lobe, in 4 – in the visual tract and lateral cranial body. Women are more likely to suffer from acquired hemianopia. The development of this pathology is possible at any age, but more often symptoms occur in people aged 30-50 years. Symptomatic treatment has not been developed, since most studies in this direction are available only retrospectively.
A key role in the development of hemianopia is played by damage to the visual tracts, the central parts of the visual pathways or the cortex of the occipital lobe. The defeat of these brain structures can be caused by a number of reasons, the most important of which are acquired pathologies. In meningitis with predominant localization in the basal parts of the brain, mechanical compression of anatomical areas responsible for the transmission of a nerve impulse to the cortex occurs. The compression mechanism of hemianopsia development occurs in intracranial localization of malignant and benign neoplasms, brain abscesses.
A violation of the blood circulation of the brain due to thromboembolism or cerebral vascular aneurysms leads not only to ischemia, but also increases the risk of an increase in intracranial hypertension and the development of bleeding, which is accompanied by an aggravation of the clinical picture of stroke. A large volume of blood, as well as increased pressure, negatively affect the performance of the visual pathways, up to their complete atrophy. Hemianopsia can be caused by serious injuries of the skull or have an iatrogenic origin due to incorrect tactics of neurosurgeons during surgical interventions on the brain.
The development of ischemic infarction in the posterior cerebral artery (PCA) affects the striator cortex, visual radiance and the lateral cranial body, which provokes the occurrence of homonymous hemianopia from the opposite side. If ischemic necrosis develops in the zone of the striator cortex below the spur furrow or in the lower parts of the visual radiance at the border of the temporal and occipital regions, upper-quadrant hemianopia is verified, if the brain is affected by the above structures on the border with the parietal zone – lower-quadrant. Individual features of the blood supply to the brain do not exclude the possibility that the middle cerebral artery (MCA) can provide regional blood flow of visual radiance. Therefore, a heart attack in the area of MCA is one of the etiological factors of the development of hemianopia. At the same time, damage to the spur furrow may be manifested by a clinical picture of loss of one side of the field of view from its side.
Congenital hemianopia is one of the manifestations of severe malformations (hydrocephalus, encephalocele, microcephaly, cystic cerebral dysplasia).
From a clinical point of view, there are homonymous (symmetrical) and heteronymous (binasal, bitemporal) hemianopsia. With homonymous form, patients complain of loss of the ability to see with the right or left halves of the eyes. When the left visual tract is affected, the clinical picture of right-sided hemianopia develops. The left halves fall out of sight with pathology of the right visual tract. The heteronymous form of the disease is characterized by the loss of either medial or lateral halves. Bitemporal hemianopia develops with localization of the pathological process in the pituitary gland or temporal lobes, binasal – with chiasmal arachnoiditis and “empty Turkish saddle” syndrome.
The clinical course of hemianopia may be accompanied by the development of visual hallucinations and agnosia (violations of the processes of recognizing familiar objects with partially preserved vision). Often patients are diagnosed with prosopagnosia, which is manifested by the inability to recognize familiar faces. Patients with hemianopia tend to deny their disease while maintaining orientation, which indicates a positive symptom of Anton-Babinsky. The ability to fix the gaze only on a specific object is noted, while not seeing others, which is the basis of “mental paralysis of the gaze”. Framed (familiar images) or unformed (fire, geometric images) visual hallucinations occur unexpectedly, after a stroke.
Patients with acquired hemianopia complain of a low ability to perform daily work, because individual objects fall out of sight. First of all, they face problems at the household level: they do not notice the entire portion of food, they cannot find things in their usual places for a long time, they are disoriented in space, they read much slower and do not even always notice the approaching transport. The congenital form of the disease is often accompanied by organic pathologies of the thalamus, parietal lobes or brain stem, so visual symptoms are supplemented by paresthesia, pain and temperature sensitivity disorders.
The diagnosis of “hemianopsia” is established on the basis of topical diagnostic data. To do this, it is necessary to conduct perimetry and computer campimetry. To determine the etiology and extent of the lesion, Doppler ultrasound, computed tomography (CT), magnetic resonance imaging (MRI) and computed tomographic angiography (CT angiography) are used. Patients are recommended to consult an ophthalmologist and a neurologist.
The perimetry method allows you to identify pathological changes in the fields of vision. With a homonymous lesion, the temporal half of the visual field falls symmetrically on one eye, and the nasal half of the visual field falls on the opposite eye. In the bitemporal form of the disease, the perception of the temporal halves, both on the left and right eye, is impaired. Binasal blindness is characterized by loss of medial divisions. With total visual impairment, we are talking about complete hemianopia. The partial (quadrant) shape is established when visualizing the defect, starting from the point of fixation of the gaze. It is also possible to investigate the pathology of the visual field in an automated mode using computer campimetry. The method allows you to accurately determine violations of color perception and light perception in various areas of the retina and indicates at what level the lesion occurred.
CT and MRI of the brain are carried out to establish the etiology of the disease and to choose further treatment tactics. With the help of these techniques, it is possible to visualize volumetric formations (abscesses, cysts, tumors), zones of ischemic or hemorrhagic stroke, as well as the volume of traumatic injuries. CT angiography can be used to obtain an image of the blood vessels of the brain and assess the nature of blood flow. The damage is most often observed in the area of PCA, less often MCA. Ultrasound Dopplerography is a non-invasive method that allows you to detect the speed of blood flow in the cerebral and ocular arteries, as well as the place of occlusion.
Conducting visometry and ophthalmoscopy is advisable only as a screening. Hemianopsia does not affect visual acuity. Ophthalmoscopy can be used to verify the lesion of the optic nerve disc only in the later stages of the disease.
Etiological treatment of hemianopia is based on the elimination of those diseases that provoked the development of the clinical picture of this pathology. Acquired traumatic brain injuries often require urgent neurosurgical intervention. An effective way to eliminate the ischemic stroke clinic is to carry out thrombolysis in the first 6 hours with further conservative therapy aimed at reducing blood viscosity by taking nootropics. The tactics of treatment of oncological diseases of the brain depends on the stage of the tumor process and most often requires surgery, radiation or chemotherapy. Only a part of the acquired diseases that caused hemianopia can be treated. Specific measures to eliminate the congenital factors of the development of this disease have not been developed.
In the event that it is impossible to eliminate the clinical symptoms, the patient is recommended rehabilitation, the purpose of which is to facilitate his interaction with the external environment. First of all, the rehabilitologist should teach the patient to make a series of small eye movements towards the field of vision that has fallen out. Moving in space requires constant eye rotation in the affected direction, as well as multiple fixation of vision at different distances – this is achieved only with the help of training. The reading process can be facilitated if you hold the book at a 90-degree angle and read the lines vertically.
It is possible to partially compensate for hemianopia with the help of special prisms and mirrors in glasses. When the direction of view is shifted to the affected side, special devices allow you to see the drop-out areas. This technique requires active eye movement, but without constant head turns. Visual functions can be improved with the help of computer techniques. Special courses are aimed at facilitating orientation in space and performing household work.
Prognosis and prevention
The prognosis for life and work capacity in hemianopia depends on the etiology and form of the disease, as well as treatment tactics. With timely and effective therapy, complete restoration of lost vision functions is possible. The progression of the underlying pathology, the clinical symptom of which is hemianopia, can provoke complete loss of vision with subsequent disability of the patient. Modern methods of rehabilitation are not able to provide full compensation for the manifestations of the disease, but significantly facilitate the patient’s life.
No specific preventive measures have been developed in ophthalmology. Patients are recommended to undergo an annual routine examination by an ophthalmologist. The appearance of nonspecific complaints (weight loss, malaise, headaches) requires consultation with a neurologist or oncologist to exclude pathological brain tumors.