What is a visual defect? You will learn the answer to this question from the submitted article. In addition, you will receive information about what eye problems people face most often, and how to get rid of them.
general information
In medical practice, a visual defect is often called a refractive error. Such abnormalities are the most common eye problems. The essence of this group of diseases is that the optical system of the eye is unable to focus light rays on the retina, which is our registrar of light stimuli. The main sign and consequence of this pathological condition is poor eyesight.
Visual impairment and its structure
This deviation can be of a different nature. Today, several common visual defects are highlighted, namely:
- astigmatism;
- myopia, or so-called myopia;
- farsightedness, or hyperopia;
- color blindness, or color blindness;
- color agnosia.
To understand why a particular visual impairment occurs, one should consider the features of the presented deviations in more detail.
Astigmatism
The reason for the development of such a pathological condition is an incorrectly formed cornea of the visual organ. It should also be noted that the development of astigmatism is directly affected by the displacement of the lens of the eye with respect to the axis of refraction. Both of these reasons entail differences in distances, which are extremely necessary for focusing the "picture".
Such a visual impairment in one eye can combine the effects of farsightedness, myopia, and normal vision.
Myopia, or so-called myopia
Myopia can develop for several reasons. The first is lengthening the eye while maintaining proper refraction. As for the second reason, this is an overly powerful optical refraction, which is more than 60 diopters, with the length of the visual organ within normal limits. Both of the deviations presented negatively affect the acquisition of a normal image. In other words, the picture is not able to focus on the retina, but is located inside the eyeball. Thus, only a focused image of any objects located at a small distance from a person penetrates the retina.
To correct such a visual impairment, patients are often prescribed special glasses to help build a clearer picture. In this case, a person can consider objects in the distance without much stress. In order for the nearsighted patient to see more clearly, minus lenses are used to approximate distant objects.
Farsightedness, or Hyperopia
Such a defect develops due to excessively weak optical refraction in the visual organs while maintaining the normal length of the eyeball. It should be specially noted that the cause of farsightedness is also the shortening of the eyeball, provided that the refractive power is preserved.
Due to the fact that the far-sighted eye is not able to create focus on the retina, muscle tension increases significantly. This phenomenon gradually changes the curvature of the lens, which in turn leads to the adaptation of the visual organ to the current conditions. However, this is not enough for normal focusing of the resulting image.
When examining objects located near the eyes, the muscle tissue of this organ tenses even harder. In other words, the closer the object is located, the further its image appears on the retina.
What are the ways to eliminate visual defects, or rather, hyperopia? To correct this deviation, glasses with plus lenses are used. They help quite well in the construction of the image.
As you know, at the birth of a baby, his eyes are slightly horizontally compressed. That is why all young children are somewhat farsighted. However, in the process of development, their vision is gradually normalizing.
If the degree of farsightedness in a person is small, then vision in the distance and near can be normal. But at the same time, people will complain of severe headaches and eye fatigue. If the degree of farsightedness is average, then this is manifested by poor vision near.
Color blindness, or color blindness
Such a defect is a congenital disease, which is most often observed in men. The essence of this deviation is that in patients the correct color perception is impaired , regulated by photoreceptor cells (cones) in the eye retina. If a person does not have any type of cone, then he has color blindness.
Color agnosia
Color agnosia is a type of deviation such as visual agnosia. With such a disease, a patient with preserved color vision may not correctly distinguish colors. There is also simultaneous and literal agnosia. Diagnosis of such deviations requires a thorough examination by a neurologist. The type of agnosia can be determined using special tests.
The treatment of such a disease consists in active treatment of the deviation that led to the defeat of individual portions of the brain. Very often, agnosia cannot be cured, causing great discomfort to the patient.
A typical visual migraine defect
Migraine with a typical aura is more common in males. In this case, patients may experience visual impairment. As a rule, they appear in the form of sparkling dots, lightning-like flashes, zigzags, balls, after which a rather severe headache attack develops. The intensity of such phenomena is observed for several minutes or seconds. Quite often, sparkling images are replaced by the loss of some parts of the visual fields. It should be especially noted that such violations are sometimes combined with numbness of the face, half of the body and tongue, as well as with weakness in the limbs and impaired normal speech.