Color vision abnormalities are a complex of pathologies of congenital or acquired genesis, including achromatopsia, color blindness and acquired color vision deficiency. Clinical symptoms are represented by impaired color perception, decreased visual acuity, and nystagmus. Electroretinography, anomaloscopy, Rabkin tables, Ishihara test and FALANT are used to diagnose color vision anomalies. The main principle of treatment is the correction of color vision using glasses or lenses with special filters. Etiotropic therapy of acquired forms is aimed at restoring the transparency of the optical media of the eye and eliminating pathologies of the macular part of the retina.
H53.5 Color vision abnormalities
Anomalies of color vision are a heterogeneous group of diseases in ophthalmology, accompanied by a violation of color perception. In 1798, the English physicist J. Dalton first described the clinical manifestations of color blindness, since he himself suffered from this pathology. The prevalence of color blindness among men is 0.8:1,000, among women – 0.05:1,000, achromatopsia – 1:35,000. Acquired color vision deficiency occurs among males and females with the same frequency. The risk group includes people taking toxic doses of chloroquine, patients with beriberi A and with degenerative-dystrophic changes in the retina. Congenital forms of color vision abnormalities are diagnosed at the age of 3-5 years.
Causes of color vision abnormalities
There are congenital and acquired anomalies of color vision. The reason for the development of achromatopsia with rod monochromatism is a mutation of the CNGA3, CNGB, GNAT2, PDE6C genes, which is inherited by an autosomal recessive type. The pathogenesis is based on a violation of the synthesis of protein molecules responsible for the transmission of information from rhodopsin inside the cell. With a conformational change in the visual pigment, the threshold of depolarization of the photoreceptor membrane decreases. This has a negative effect on the synthesis of glutamate, thereby increasing the excitability of bipolar cells, which, due to the mutation of transmitter proteins, do not respond to light exposure and changes in the structure of the visual pigment. With this form of color vision abnormalities, the rod receptors, unable to perceive colors, display the image in various shades of gray.
Congenital color blindness develops with mutations of the OPN1LW and OPN1MW genes, which are localized on the X chromosome, so the disease is inherited by an X-linked mechanism. Less often, color blindness is diagnosed in newborns with cone dystrophy, Leber’s amaurosis, retinitis pigmentosa. An acquired variant of this color vision anomaly is observed in patients with traumatic injuries, pathological neoplasms, hemorrhages or ischemia in the occipital lobe of the brain. Transient color blindness develops in people with acute poisoning or chronic intoxication. The disease occurs in isolation, but in rare cases it refers to manifestations of macular degeneration, idiopathic parkinsonism, retinopathy on the background of diabetes mellitus.
The etiology of acquired color vision deficiency is associated with a decrease in the transparency of the optical media of the eyeball. Common causes of this phenomenon are corneal opacity, cataracts, the presence of precipitates or inflammatory exudate in the anterior chamber of the eye, destruction of the vitreous body. Anomalies of color vision of acquired genesis occur during the course of pathological processes in the macular region of the inner shell of the eyeball (epiretinal membrane, age-related macular degeneration).
Symptoms of color vision abnormalities
Color vision abnormalities include achromatopsia, acquired color vision deficiency, and color blindness. The main clinical manifestation of achromatopsia is black-and-white vision. Concomitant symptoms of this anomaly of color vision are represented by nystagmus, hypermetropia. Hypersensitivity to light leads to photophobia and hemeralopia. As a rule, patients have a characteristic appearance with downcast eyes due to pronounced photophobia. Often patients use sunglasses. Sometimes this anomaly of color vision is complicated by the clinic of strabismus.
The clinical picture of color blindness is represented by the lack of the ability to differentiate one or more colors or its shades. With protanopia, the perception of red color is disturbed, tritanopia – blue-violet, deuteranopia – green. No color vision abnormalities are observed in persons with trichromasia. When the brightness or saturation of a certain part of the spectrum changes, this group of people is able to perceive all colors and their shades. Patients with dichromasia do not differentiate one of the primary colors, replacing it with those shades of the spectrum that are preserved. In the case of monochromasia, patients see everything around in only one chromatic shade. This variant of color blindness can be complicated by nystagmus, photophobia and decreased visual acuity.
Unlike other color vision abnormalities, acquired defects are characterized by a monocular onset of the disease. However, in case of poisoning or chronic intoxication, simultaneous damage to both eyeballs occurs. Clinical symptoms occur a second time, against the background of specific manifestations of the underlying pathology. Symptoms are a decrease in visual acuity, narrowing of the visual field, the appearance of “flies” or “shrouds” in front of the eyes.
Diagnosis of color vision abnormalities
Diagnosis of color vision abnormalities is based on anamnestic data, results of external examination, electroretinography, visometry, perimetry, genetic screening, examination using an anomaloscope, Rabkin tables, Ishihara test and FALANT test. An external examination of a patient with achromatopsia can detect nystagmus. Examination with Rabkin tables allows you to diagnose a violation of color perception. Electroretinography determines the absence of cone peaks or their pronounced decrease. In the course of visometry, with this anomaly of color vision, there is a decrease in visual functions. Genetic sequencing is aimed at identifying mutations and establishing the type of inheritance.
The Ishihara test and Rabkin tables are used to diagnose the form of color blindness. The techniques are based on the formation of certain figures, pictures or numbers from different colors. If the perception of one of the shades is impaired, it is impossible to determine what is depicted in the test or on the table. In modern ophthalmology, anomaloscopy can be used to examine all the characteristics of the functioning of receptors (the degree of color perception impairment, color adaptation, the influence of physical factors and medications on visual functions). The FALANT test allows you to more accurately diagnose color perception disorders, i.e. K. colors and shades are formed by merging the diffused glow of the lighthouse using a special filter. With this anomaly of color vision, a genetic study is also carried out. The acquired form of the disease is an indication for additional research methods – ophthalmoscopy, biomicroscopy, tonometry and perimetry.
Polychromatic tables and the method of spectral anomaloscopy are also used to diagnose acquired color vision insufficiency. However, with this pathology, it is necessary to establish the etiology of the disease. Biomicroscopy with a slit lamp is used to study the transparency of the optical media of the eye. Pathological processes in the macular region can be detected using ophthalmoscopy, optical coherence tomography (OCT) and ultrasound examination (ultrasound of the eye) in B-mode.
Treatment of color vision abnormalities
The tactics of treating color vision abnormalities depends on the form of the disease. Etiotropic therapy of achromatopsia has not been developed. Symptomatic treatment is aimed at correcting visual acuity with glasses or contact lenses. In places with bright lighting, it is recommended to wear sunglasses. The complex of therapeutic measures includes taking multivitamin complexes containing vitamins A and E, vasodilators. At the present stage of the development of ophthalmology, the restoration of color perception is possible only experimentally in animal experiments.
For such an anomaly of color vision as color blindness, etiotropic therapy has also not been developed, regardless of whether the disease occurs due to a gene mutation, against the background of Leber’s amaurosis or congenital cone dystrophy. Tinted filters for glasses or special contact lenses can be used to correct color perception. The tactics of treatment of the acquired form of the disease is reduced to the elimination of etiological factors (surgical intervention in case of damage to brain structures, phacoemulsification of cataracts).
When diagnosing acquired color vision deficiency, it is necessary to determine the cause of its development. If the violation of the transparency of the optical media of the eyeball is caused by an inflammatory process of bacterial origin, it is recommended to prescribe antibacterial and hormonal agents for local administration. In case of viral origin, antiviral ointments should be used. Often, with macular localization of the pathological process, a surgical operation aimed at removing the epiretinal membrane is indicated. In the dry form of age-related degeneration, there are no special treatment methods. The wet form of this color vision anomaly is an indication for laser coagulation of newly formed vessels of the inner shell of the eyeball.
Prognosis and prevention
Prevention of the development of color vision abnormalities has not been developed. All patients with color blindness, achromatopsia and acquired color vision deficiency should be registered with an ophthalmologist. It is recommended to undergo an examination 2 times a year with additional ophthalmoscopy, visometry and perimetry. It is necessary to take multivitamin complexes containing vitamins A and E, to correct the diet with the mandatory inclusion of foods rich in vitamins and trace elements. The prognosis for life and work capacity in color vision abnormalities is favorable. At the same time, patients often experience a decrease in visual acuity, it is impossible to restore normal color perception.