Diagnosis of visual acuity

The world around us is full of different colors, smells and sounds. All this we feel with the help of our senses. Most of the information comes through the eye - eyes. Vision is a very complex biological process. But to perceive the image, in addition to the eye, the oculomotor nerves and muscles, the brain and optic nerves also participate. A person who has good eyesight should clearly see both afar and near. External, the very first violations of the act of sight, are associated with a change in visual acuity. Therefore, visual acuity diagnosis is necessary in all ophthalmological examinations.

Visual acuity testing methods

Explore visual acuity with the help of optotyping tables and the sign projector. Signs( optotypes) that are used to measure visual acuity are very diverse. The most common signs are: the Snellen sign( S-shaped), the Landolt sign( rings, different in size, with a break), letters of the alphabet, numbers, figures, stripes, etc. All the signs in the table are grouped in separate rows, each of which corresponds to a certain visual acuity. Measurement range of visual acuity is 0.1-2.The visual acuity of v = 1 is taken as the norm. When checking the visual acuity, it is necessary to ensure sufficient brightness of the background of the tables, as well as the corresponding contrast of signs( dark signs on a white background).To determine the vision in children, schemes with pictures are used, in which the size of the picture corresponds to the visual acuity.

To study the visually impaired, the Polyak set is used. It is a test in the form of Landolt's rings and three-line figures. The device is hung on the wall at a distance of 1.2 m from the floor and at a distance of 5 m from the subject.

How the

vision is checked During the examination, the medical room should be bright and well lit. Eyes are open, but that eye, which is not examined, is covered with an opaque shield. Sometimes a doctor can allow the eye to cover the palm, but you can not press on it, because it reduces visual acuity. Each eye is examined separately. The signs are indicated by a pointer, the stopping time on each optotype should not be more than 2-3 seconds. On the row, where all the signs are correctly named and the visual acuity is evaluated. According to Snellen's formula, visual acuity can be calculated. It is written as follows: VISUS = d / D, where d is the distance to the place where the patient sits, D is the distance indicated in all rows of the table to the left of the optotypes. In one series, one incorrect recognition of a sign may be allowed. This is recorded in the results of the study.

Checking the eyes at home

Take a white sheet of Whatman and write on it any letters 7 mm high and 7 mm wide. Remove the sheet 5 m from the person being examined and arrange it at the level of its eyes. If all letters are seen clearly and well, then your visual acuity is 1.0.If the letters are not clearly visible, then you need to find the distance from which you will distinguish them well. In this case, visual acuity is calculated as follows: this distance( in meters) must be multiplied by 0.2.For example, if you can see letters with 3 m, then you need 3 x 0.2.Let's get your visual acuity equal to 0.6.

Visual acuity deterioration occurs with injuries, eye traumas( this is the most common cause of blindness), with inflammatory, vascular, dystrophic eye diseases. And also with abnormalities of refraction( emmetropia, astigmatism, myopia, hyperopia).

How to maintain and improve your vision

First of all, you need to protect your eyes from injuries, ultraviolet and infrared radiation. It will help to maintain health and a clear organization of the workplace, good lighting, correct landing. It is useful to make short, but frequent periods of rest, learn to relax. It is necessary to monitor food, to be more in the street, in the forest, near the river, in the meadow, where a wide horizon is provided - a wonderful rest for the eyes. To check your eyes, visit periodically a specialist - this will help your vision last longer, and if you find any problems - do not allow their development.