Classification of visual impairment, which is used by ophthalmologists, may be based on the degree of visual acuity, the time of appearance or the cause of facial pathology. All these factors are taken into account when diagnosing.
The degree of visual impairment is determined by the ability of the eye to see two dots that glow at a minimum distance between them. Normal visual acuity, equal to one - 1,0, corresponds to the ability of a person to distinguish on a special table, the tenth step of numbers and letters from a distance of 5 meters. In medicine, there are several classifications of visual impairment in humans.
Classification of the violation depending on the visual acuity
As the main in medicine, the classification of visual impairment is used, depending on the person's ability to see.
- Blindness. Incomplete absence of visual sensations or residual vision. When wearing glasses, the maximum visual acuity is indicated - 0.04 or only the ability to sense light.
- Absolute or total blindness. Characteristic is the complete lack of visual sensations or the presence of a light sensation, form vision with a sharpness from 0.005 to 0.04.
- Blindness of blindness. Visual acuity from 0.05 to 0.2. With such a star, eyes perform their informative function.
Classification of visual impairment, depending on the time when the defect appeared
Depending on the time the defect appeared in ophthalmology, the following classification of visual impairment is distinguished:
- Blinded These include all those born with absolute blindness or blinded to the age of 3 years;
- Blinded These are people who have lost the ability to see at the age of 3 years.
At the heart of this classification of visual impairment is the presence of a partial or completely absent representation of the surrounding world.
Visual impairment for various diseases of the visual system
There is a classification of types of disturbance of the visual function depending on the causes of the defect:
- Refractive error. In this case, the image of the subject does not focus clearly before the retina;
- Accommodation disorder This is the inability to clearly examine all objects that are on a different distance;
- Peripheral vision disorder. There is no clear image of the objects that are in motion or on the sides of the eyes;
- Disorder of adaptive ability of the eye. Deterioration of vision when changing the illumination.
This specification of visual impairment is based on changing the ability of a person to see, but not in full absence.
Each of these classification of violations of the ability to see is used by an ophthalmologist to accurately diagnose and is an important criterion for assessing the general state of human health. Therefore, the degree of visual impairment is determined depending on the severity and cause of opacification of visual sensitivity.