Visual acuity is one of the main functions of the eye, researched by an ophthalmologist at the reception. It can go down due to refractive errors, eye diseases and injuries, neurological diseases.
There are many factors that lead to poor eyesight. These ones include aging, unhealthy lifestyle, increased visual load, various injuries, as well as many different diseases. If you see a decrease in visual acuity, you should immediately seek help from an ophthalmologist.
Indications for the procedure
The procedure for visometric testing is performed with the following indications:
- loss of vision as a result of the development of any ophthalmic disease.
What can be investigated with the help of visometry?
Visometry allows you to set a look-up ratio, and this information is necessary for eyeglasses and contact lenses specialists.
Pay attention: Usually, after using visometry, it is possible to determine the very fact of a violation of the visual acuity, the patient is given spectacles with the corresponding dioptric power, wearing which the person in theory should gain visual acuity equal to unity.
At a certain stage, such spectacles can be selected, which means the possibility of ordering lenses or spectacles with the same dioptric indexes. Visometry today refers to the basic, but not the ultimate methods of ophthalmological examination, since the procedure makes it possible to establish the presence of disturbances.
The first step to identify problems that prevent a person from seeing normally is the visometry. This method is based on the use of special tables with letters or symbols printed on them by symbols. The latter are used mainly when examining children.
An important point is precisely the size of the symbols, which taking into account an accurately measured distance indicates problems with visual acuity. The tables themselves can be presented in the form of a diagram printed on a piece of paper, or they can be displayed on the canvas using a projector or on a special monitor of specified sizes.
They show 12 rows of letters, which are placed on a sheet from the largest on top to the smallest in the last line. In the normal state of the eye, a person should clearly see the 10th line from a distance of 5 meters. It is generally assumed that the vision corresponds to 1 unit of evaluation or 100%.
If the 10th line is not visible, but only 9 lines can be distinguished normally, then the person has an acuity score of 0.9 or 90%. By a similar analogy, you can calculate other factors of vision. Another goal of this study is to identify a person’s nearsightedness or farsightedness.
Such a diagnosis can be supplemented by the selection of glasses or contact lenses in which the vision of a person will be 100%. For these purposes special frames are used, in which the doctor alternately inserts lenses with varying degrees of curvature. They are selected taking into account the results obtained in this procedure.
As a rule, this diagnostics is the first stage of ophthalmological research and, if necessary, is supplemented by an examination with a slit lamp or other more technically serious methods. Sometimes magnetic resonance or optical coherence tomography can be used with the introduction of a contrast medium or special medications to dilate the pupil.