Human vision is one of the largest and at the same time fragile abilities. You need to watch her all the time. Hike to the ophthalmologist should be a periodic exercise in the life of every person.
Vision test in modern ophthalmology
In the distant USSR, the scientist Sivtsev was inventedan indispensable tool for modern ophthalmology, which in honor of the author was called the “Sivtsev table”. This technique is used to determine visual acuity. For this, 12 rows of characters were identified: letters and rings with a gap, which, starting from the top row, towards the bottom row are gradually reduced. From a distance of 5 meters, visual acuity is determined on a scale of 0.1 to 2.0.
What is visual acuity and how is it checked using the Sivtsev table?
Visual acuity is the ability of the humaneyes distinguish between two points located at a certain distance from each other. Effective norms say that an eye that has 100% vision can distinguish between two points that are separated from each other by an angular distance of one minute. Thus, visual acuity can be described as the ability to clearly see and describe such vigilance with a digital indicator of 100% or 1.0. Sivtsev's table is designed in such a way that this digital indicator and determine.
There are situations when a person’s visionso well developed that its sharpness can be estimated at 1.2 or 1.5 and even 3.0. While in various diseases of the eye, such as myopia or hyperopia, astigmatism or glaucoma, deviations from the norm can be 0.5 or 0.05.
Often, visual acuity is described bypercentages. However, it is worth paying attention that only 100% sharpness indicator corresponds to 100% vision. For example, a sharpness index of 0.2 diopters cannot be converted to percentages as 20% vision. This indicator will correspond to 49% of the norm. It is not so easy to translate any indicators into percentages and back. This is what makes Sivtsev's table special: the dimensions in the columns on the left and on the right are the already calculated test results.
How to check visual acuity table Sivtseva?
Standard set of printed characters of varioussize lined up in 12 rows. All these are letters of the Russian alphabet - W, B, M, N, K, S. Each bottom row - letters smaller than the top. Testing must be done in a room with good lighting. It is provided with a special lamp, aimed at the table, and having diffused light. At a distance of 5 meters from the subject, the table of view of Sivtsev is located. The patient should be comfortable and, alternately closing the right and left eye, read the letters from the table. If the person being checked easily calls letters up to 10 rows, consider that he has 100% vision. If he stops at any of the upstream rows, his visual acuity is determined by the indicators in the right row of the table.
The patient may be located closer than 5 meters from the table, but in this case a special formula will be used to determine the acuity:
V = d / D
V in this formula is the value that we needdetermine, namely, visual acuity; d - the distance at which the patient is from the table; D - the distance at which the patient distinguishes the symbols of a certain series.
Now more about how it should be locatedSivtsev table. It is placed between two fluorescent lamps, so that the illumination reaches 700 lumens. The lower edge of the table should be at a height of 120 cm from the floor. The patient sits comfortably, his head kept straight, the eyelids of both eyes open in the usual position. A special white shield is attached to one eye. Within 3 seconds, the checked person is shown the letter, which he should name. At the same time, they start from the bottom row and gradually rise to larger signs. If all signs are named - have the test 100% or 1.0 view. If one or more signs are not recognized - incomplete visual acuity. To determine the visual acuity of less than 0.1, the patient gradually approaches the table every 0.5 m, until he can determine the signs of the table.
Designations in the table Sivtseva
In addition to the letters of the Russian alphabet, you can see thatthere are two more columns, which are indicated by the Latin letters D and V. The numbers in the D-column denote the distance from which a person from the table, whose visual acuity is 100%, can easily read the sign on the left. The numbers in the V-column is a numerical characteristic of visual acuity, if this series is readable at a distance of 5 meters.
What other tables are used in ophthalmology?
Since vision is a very important humanWith the ability to be maintained in good condition, there are a number of tests used in ophthalmology that allow you to show a real picture of the condition of the eyes.
- Visual acuity check - for this was createdtable Sivtseva (as it is called in some sources). Here the letters Ш,,, Н,,,,. Are used. They also use the Orlova table for children, where instead of letters they use pictures (asterisk, fungus, horse, teapot, airplane, duck, elephant, machine, herringbone).
- Checking the contrast of vision - for this the Golovin table was created. It uses 4 types of optotypes - rings with a gap in one of 4 sides.
- Check for myopia and hyperopia -use duohromny test, which represents the two halves of the background of a different color: red and green, on this background are the letters (K, N, W, M, I, B, Y). As a result of the test, it is determined whether the vision is normal (the eyes see the letters on both backgrounds the same). If on the red background the letters of one row are sharper than on the green, then myopia takes place, on the contrary - long-sightedness.
- Astigmatism test - the mostA common test is the star of Siemens. The essence of the test lies in the fact that a person with normal vision sees lines in the figure, which, not reaching the center, begin to blur or overlap with each other. In the very center of the line again become clearly visible.
