Blindness is a pathological condition in which visual acuity is sharply reduced or completely absent. Depending on the form of the disease, clinical symptoms are represented by a decrease in visual acuity, the appearance of cattle, impaired color perception, loss of nasal or temporal halves from the visual field. The diagnosis of blindness is based on the results of visometry, perimetry, ophthalmoscopy, fluorescence angiography, electroretinography, campimetry, Ishihara and FALANT tests, Rabkin tables. Etiotropic therapy of various forms of blindness differs significantly and is selected for each patient individually.
H54 Blindness and low vision
Blindness is a heterogeneous group of diseases in ophthalmology characterized by a decrease in visual acuity or color perception. This pathology is one of the most important medical and social problems, since it is the cause of disability of patients. At the same time, 3/4 of cases of blindness with timely diagnosis and treatment are reversible. According to the World Health Organization (WHO), there are about 100 million blind people in the world, and their number is increasing every year. 90% of the total number of blind patients live in developing countries and only 10% in developed countries. In addition to cataracts and glaucoma, background, infectious and parasitic diseases that can be treated play a leading role in the occurrence of this pathology among residents of developing regions. In developed countries, the number of cases of blindness against the background of age-related degenerative-dystrophic macular changes and diabetic retinopathy increases every year.
Causes of blindness
According to WHO statistics, the most common cause of blindness is cataract (47.9%). Congenital variants of the disease are caused by mutations. As a rule, the reasons for the decrease in visual acuity in such cases are the familial form of lens opacity, aplasia of the inner shell of the eyeball, tapetoretinal degeneration, albinism. A special type of this pathology is cortical blindness, in which clinical manifestations are caused by damage to the occipital lobe of the brain. Common teratogens in relation to the organ of vision are medicines, toxins and pathogens of infectious diseases.
There is a high risk of eye damage when teratogenic factors affect the fetus at the stage of embryonic development. In the prenatal period, the development of blindness is provoked by pathogens of rubella, toxoplasmosis, influenza, tuberculosis. In adulthood, chlamydial origin of visual disturbances against the background of trachoma is more often observed. Eye damage with frequent loss of vision is characteristic of helminthiasis such as onchocerciasis. Isolated cases of blindness are diagnosed with dirofilariasis.
The etiology of early blindness is associated with exposure to triggers in the birth or perinatal period. At the same time, newborns are diagnosed with retinopathy, hypoplasia of the visual pathways or hypoxic damage to the optic nerve, which later lead to visual dysfunction. In children (especially premature infants), a decrease in visual acuity potentiates vitamin A deficiency, congenital clouding of the lens or retinopathy. In young patients, most cases of monocular blindness are caused by traumatic injuries. In old age, vision loss is associated with both general diseases of the body and with the course of degenerative-dystrophic changes in the retina or optic nerve.
Damage to the inner shell of the eyeball or optic nerve with a progressive decrease in visual acuity is characteristic of such common diseases as hypertension, atherosclerotic vascular lesion, retinopathy on the background of diabetes mellitus. Blindness can occur a second time against the background of pathologies of the central nervous system – meningitis, encephalitis, toxic brain damage. According to statistics, with timely diagnosis, many cases of this pathology are potentially reversible. As a rule, the cause of irreversible blindness is glaucoma due to the development of optic nerve atrophy.
From a clinical point of view, blindness is classified into amaurosis, scotoma, hemianopia and color blindness. According to WHO, the diagnosis of blindness can be established with the ability to see less than 3/60 or a narrowing of the visual field to 10 degrees. If the visual acuity is 0, we are talking about absolute blindness. With light perception preserved and reacting to changes in its intensity, but the inability to distinguish the shape of surrounding objects, blindness is called objective. In the civil variant of visual dysfunction, the patient cannot determine the number of fingers on the hand at a distance of 3 meters. Professional blindness is also distinguished, in which visual impairments interfere with the performance of professional duties.
A specific symptom of transient amaurosis is a sharp loss of vision with a total duration of no more than 10 minutes. This phenomenon is associated with reversible ischemic changes in the carotid artery basin. Leber’s amaurosis is manifested by nystagmus and a marked decrease in visual acuity, detected even in early childhood. Often this form of blindness is combined with keratoconus, cataract, astigmatism, strabismus. Extra-ocular manifestations of pathology are represented by mental retardation, epileptic seizures, hearing loss, hormonal imbalance, malformations of the kidneys, bone system or central nervous system. Patients with this variant of blindness are rarely able to distinguish light from darkness or track the movement of nearby objects.
With pathological scotomas, defects in the fields of vision are revealed, which the patient sees as dark spots in front of his eyes. These defects can partially cover the image in question. When cattle are detected, which the patient does not notice, we are talking about a “negative” version of the pathology caused by the lesion of optical nerve fibers. Hemianopia is binocular blindness with damage to one half of the visual fields. In the homonymous form of the disease, both right or left halves fall out, heteronymous binasal – lateral, heteronymous bitemporal – medial parts of the visual field. With color blindness, the ability to differentiate a certain color is impaired. Protanopia is manifested by the inability to perceive red, tritanopia – blue-violet, deuteranopia – green. Achromatopsia is blindness characterized by pathological color perception, in which patients are unable to distinguish all shades of the color spectrum.
Diagnosis of blindness is based on visometry, perimetry, ophthalmoscopy, fluorescent angiography, electroretinography, campimetry. Visometry allows you to diagnose the degree of visual impairment. Category I includes patients with visual acuity of 0.1-0.3 dpt, II – 0.05-0.1 dpt, III – 0.02-0.05 dpt. In patients of category IV, light perception is preserved – 0.02 dpt, with V there is no light perception. According to the results of the examination, patients belonging to group I and II are classified as visually impaired. The diagnosis of blindness can be established only for persons of groups III-V. Visual field 5-10° according to perimetry corresponds to category III, less than 5° – IV.
Also, during perimetry, it is possible to identify pathological scotomas that have the appearance of defects in the field of vision of an oval, rounded or arcuate shape. By the method of campimetry in temporal, nasal, frontal and chin points and in 4 oblique meridians, the size of the scotoma is measured with subsequent fixation of the indicators in a special patient card. The main method of hemianopsia diagnosis is perimetry. In the homonymous form of blindness, visual field defects are found in the temporal and nasal sections of different eyes. The binasal variant of the pathology is characterized by the loss of the medial, and the bitemporal – lateral halves of the visual field.
In case of transient amaurosis, fluorescence angiography is indicated to determine the exact localization of the ischemia zone. As a rule, the study reveals an embolism of the arteries of the inner shell of the eyeball. Leber’s amaurosis is characterized by a decrease in the amplitude of waves or their complete absence during electroretinography. During ophthalmoscopy in patients older than 8 years, calcifications and pigment corpuscles are determined along the periphery of the fundus. To diagnose color blindness, the Ishihara test, Rabkin’s polychromatic tables, and the FALANT test are used.
In case of transient amaurosis, vasodilators, direct-acting anticoagulants, thrombolytics, antiplatelet agents should be prescribed urgently. A specific tactic for the treatment of Leber’s blindness has not been developed. Symptomatic therapy includes taking multivitamin complexes and intraorbital injections of vasodilators, correction of visual acuity with glasses. When diagnosing cattle, etiotropic treatment is required. If the cause of the disease is retinal detachment, vitrectomy is indicated, followed by filling or balloning of the sclera. When visual field defects appear due to pathological neoplasms, they are removed. In case of blindness caused by spasm of the cerebral vessels, it is necessary to prescribe antispasmodics.
Etiotropic therapy of hemianopia is based on the relief of causal factors. Neurosurgical intervention in patients with this form of blindness is indicated for traumatic brain injury, benign or malignant neoplasms of the brain. If special treatment methods are not available, a rehabilitation course is recommended. Specific tactics of color blindness therapy have not been developed. Glasses with special filters or contact lenses are used to correct visual functions.
Prognosis and prevention
Specific prevention of blindness has not been developed. With timely diagnosis and treatment, visual functions can be preserved in most cases. All patients with this pathology should be registered with an ophthalmologist. The prognosis for blindness is often unfavorable. 95% of patients with Leber’s amaurosis irreversibly lose their eyesight at the age of 10 years or earlier. However, with color blindness, visual acuity often does not change. A decrease in visual functions may be the cause of temporary or permanent loss of performance. If it is impossible to restore the functions of the visual organ, patients are assigned a disability group. With a visual acuity of 0.05-0.2 dpt, it is recommended to study in a special school for visually impaired children, below 0.05 dpt – in educational institutions for the blind.