Definition
The visual acuity of the eyes is tested with an eye test. This indicates the resolving power of the eye, i.e. the ability of the retina to recognize two points as separate. The visual acuity defined as normal is at a visual acuity of 1.0 (100 percent).
Adolescents often achieve even better visual acuity and with increasing age, visual acuity then decreases, which is caused by increasing stiffness of the eye lens, but can also have other causes. A distinction is made between near vision and distance vision. The near visual acuity indicates the visual acuity at a distance of about 0.3 m and is mostly used for
Reasons for an eye test
Visual acuity is checked at every examination at the ophthalmologist. In certain professions, such as pilots or police officers, a minimum visual acuity is prescribed and must be tested and documented by an officially recognized body. Good or sufficiently corrected vision is also required for driving a vehicle and must also be officially tested before applying for a driving license.
In addition to the ophthalmologist, opticians, doctors from the health department, doctors with the area title of occupational medicine and doctors with the additional title of occupational medicine are authorized to issue such a certificate of adequate vision. However, they must have the necessary equipment for the examination and be sufficiently qualified to perform it. Visual acuity is impaired in the following diseases:
- Myopia
- Long-sightedness
- Hemiplegia
- Weak eyesight (caused by one-sided strabismus at preschool age)
Eye test forms
There are various ways of performing an eye test, which are explained in more detail below This test involves standardized DIN vision symbols in ring form, which have an opening on one side whose direction is to be recognized by the person being examined for visual acuity. The line width is set so that it appears at an angle of 1 arc minute for a healthy eye with a visual acuity of 1 (i.e. 100%). If the tested person is not able to name the direction of the gap correctly, this is called ametropia.
Compared to traditionally used letters, Landolt rings have the advantage that they are more difficult to guess or hardly remember. Furthermore, this test is also suitable for measuring visual acuity in small children and illiterate people. This form of vision test is used in the visual acuity check when applying for a driver’s license.