All types of visual impairment can be divided into two groups – organic and functional types of visual impairment.

Organic types of visual impairment include ophthalmic pathologies that develop accompanied by structural changes – these are atrophic lesions of the vision nerve, blepharitis and conjunctivitis, as well as some others. These visual impairments can affect the incorrect path of light rays in the organ of vision, but defects in the anatomical structure are the cause of such disorders.

Functional types of visual impairment can also develop accompanied by structural changes. But the deterioration of visual function in this case is due to a completely different reason – changes in the path of light rays, which, penetrating the organ of vision, form an image of the object. These types of visual impairments have a relationship with refractive errors.

Among the reasons for the development of types of visual impairment are not only anomalies of accommodation and refraction. The reasons also include all ophthalmic pathologies, the result of which is visual impairment.

According to the results of many studies, more than three and a half billion people of the almost six billion population of the world suffer from some type of visual impairment. At the same time, vision correction is carried out only a little over a billion.

Deterioration of the visual function, among other things, also has great social significance, since through the organs of vision a person receives more than ninety percent of information about the surrounding reality. Accordingly, the deterioration in the functioning of such an important organ of perception as the eyes leads to an inability to adapt in society, to a certain loss of working capacity and other unpleasant consequences.

You can create a separate topic about the limitation of performance. Disruption of the work of the visual analyzer leads to the formation of barriers to a large number of types of employment. People with poor eyesight are not allowed to participate in many sports, cannot go to serve in the elite troops, such as the landing force or the special forces. In addition, poor eyesight does not allow piloting aerial vehicles and much more.  

Of course, all this negatively affects the psychological and emotional state of a person.

Due to poor eyesight, dangers immediately arise for a person in the world around them – these are collisions and falls on the sidewalk, dangers on highways, etc.

Classification of types of visual impairment:

– refractive disorder, which involves the suppression of the ability of the eye to clearly see objects located at a certain distance from the organs of vision;

– accommodation disorder, implying, for example, presbyopia, or, in simple terms, farsightedness, when a person cannot clearly see objects at different distances;

– a disorder of peripheral or lateral vision, when a person is not able to clearly see objects located on the sides of the organs of vision or cannot see moving objects; 

– disorder of the adaptive ability of the eyes, when, for example, vision deteriorates when trying to adapt to the conditions of rapidly changing light intensity. For example, eyes suffering from this type of visual impairment cannot get used to the dark for a long time or do not get used to it at all.

– disorder of the ability of the eye to navigate in the twilight or in a darkened room. Such a violation is popularly called night blindness.