The procedure for checking the visual acuity. Correctioo of defects.

Vision test at the ophthalmologist`s office. Now the majority of opticians offices have an ophthalmologist, equipped with modern diagnostic equipment. Verification of the study include the ability to distinguish details of the near and long distance, field of view (determination of its defects) and the possibility to distinguish colors.

Testing of visual acuity is to assess the ability to distinguish details. Visual acuity tesl as far away (distance vision), and separately at close range (near vision). To test visual acuity patients totally exhibit a set of letters or spccial characters of different sizes These signs arc either stored in special tables, which are hung on a wall, or arc projected on the screen hanging on the using a special device - projection signs Ihc patient is required to read the letter presented to him or to identify the displayed characters. Visual acuity test initially for each eye separately, and then for the two eyes (ie, when you look at the same time the two eyes), and with corrective lenses (if you wear glasses or contact lenses), and without them. To test the visual acuity is usually close to offering small to read passages written letters of various sizes.

If the assessment of visual acuity found that the vision is below normal (with normal visual acuity is taken equal to 1.0), then by the ophthalmologist continue to explore the reasons for this decline - it is conducting a study of refraction patient. Investigation of the patient's refractive error - the definition of the optical power of corrective spectacle lenses (refractive error), which requires the patient to improve his visual acuity. Refractive errors occur when light rays are collected are not exactly on the retina, and in front of or behind it (for details, see the article "Mistakes refractive errors"). Refraction must examine those who have already wear glasses or contact lenses.

On the field of view is carried out to test the peripheral vision. Field of view - is the entire area, which can be seen at a certain view direction. Located in the center of the field of view is most clearly visible objects, and on the periphery of the worse.

Tests for color vision test used to test the ability to distinguish colors. This study is conducted to identify color blindness (color blindness) in people with suspected disease of the retina or optic nerve (see article, "The structure of the eye"), or if there is a genetic predisposition to the disease (ie, someone in the family was color blindness), standard procedure of testing is to determine visual acuity and refractive errors.

Visual acuity should be checked regularly. If you do not have any problems with your vision, then, depending on the age of vision should be checked with the following intervals (see below for summary recommendations of various experts):

1. shortly after birth

2. about 6 months

3. 3 years

4. before school and at school each year

5. every two years between the ages of 19 to 64 years

6. every year after age 65.

These dates are advisory in nature and should be followed in cases where there is no vision problems. In the presence of visual impairment doctor can prescribe more frequent visits to the doctor's office, an ophthalmologist. Visual acuity test for several reasons:

1. In order to ensure that does not require a correction of vision (ie, no need to wear glasses or contact lenses)

2. to monitor the possible eye diseases (such as retinal detachment in diabetes)

3. if an eye injury

4. to obtain a driving license or access to certain professions

Testing of visual acuity

To test the visual acuity using various tests. Distance vision is usually checked by using a table-Sivtseva Golovin (named in honor of Ophthalmologists have developed - SS Golovin / 1866-1931 / and DA Sivtseva / 1875-1940 /.) The table shows 12 horizontal rows of letters of different sizes. At the top of the table are the largest letters. In each of the next row font size is reduced by a certain law. Hang on a wall chart, and the patient is located at a distance from her 6 meters.

Instead of a table with printed signs now increasingly use electronic projection signs. These devices are projected characters (letters or other characters) on the screen, which can be located at a close range (difference between the selected distance from the standard device is automatically taken into account).

Patient is instructed to read the letters in each row. If he is able to recognize all the letters in the 10th line from the top, he has visual acuity of 1.0, ie his eyes are normal. If the patient sees the letters in the 9-th row (and in the 10th did not see), then his vision 0.9, if only in the 8th - 0.8 and so on.

Determine the first visual acuity for each eye (the second special cover flap), and then when the patient sees with two eyes.

If the patient wears glasses or contact lenses, he can offer to test visual acuity in the means used by the vision correction.

Sometimes, instead of the letters use special characters - rotated in different direction letter H (or E), a ring with a small gap, which is looking in different directions, images and other animals. These signs are used for eye exams for children or those adults who can not read. The patient is required to identify the symbol is displayed (for example, to show where the ends of the letters sent to R). To test near vision use a small card on which are printed a few paragraphs of text. Each paragraph typed letters of different sizes. The text kept at a distance of 33-35 cm patient with normal vision should read the text near the size of which corresponds to the vision of 1.0.

If the patient is not able to read the largest letter in the table-Sivtseva Golovin, then the doctor will apply a different technique of visual acuity. The study is conducted to determine the refractive power of corrective lenses (refractive error). Testing consists in checking the quality of a diagnostic wearing lenses of different optical power (ie with different number of diopters). This is usuattyput on a special test frame, which contains various lenses. Instead, the test frame with a set of test spectacle lenses in a well-equipped salons for the determination of refractive optics can be used a special device (phoropter). The patient looks into the windows, which are automatically replaced by lenses of different focal power.

The specialist asks the patient to compare the different lenses in the eye and say in what lens you can see it better. So gradually matched lenses, in which the patient. sees the best of everything. The physician must strive to ensure that the patient's vision with the lenses was as close to 1.0.

The parameters of these lenses are written in the recipe for the manufacture of glasses or contact lenses to fit.