What is Vep eye test

Eye test

A Eye test is the test of a person's visual acuity. The eye test is an indispensable and informative examination for the ophthalmologist. In most cases, an eye test is done remotely.

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The patient has to read out symbols (usually numbers) on an ophthalmologist's board or on a projection. An eye test can be done without correction (with the naked eye) or with correction of ametropia. The vision test determines whether the patient can see as well as people with healthy eyes or whether there is a reduction in visual acuity.

This visual acuity is called visual acuity by the ophthalmologist. With a visual acuity of 1.0 (colloquially also: 100 percent) the patient sees normally. If the values ​​are lower, there is a impairment of vision.

When is an eye test done?

The eye test is done whenever a patient is examined by an ophthalmologist. The eye test can also be carried out at the optician's to determine the values ​​for a visual aid. The ophthalmologist will do the exam so they can see if your vision has deteriorated. This can be the case with a variety of different diseases.

A visual acuity reduction is z. B. for ametropia. The ametropia include nearsightedness, farsightedness and astigmatism (astigmatism, astigmatism). However, ametropia can be corrected using special glasses, among other things. Therefore, with appropriate correction and otherwise unharmed eyes, a patient will have normal visual acuity.

In the case of other eye diseases, however, the visual acuity cannot be compensated for by holding corrective glasses in front of them. Among other things, clouded media of the eye (e.g. clouding of the lens = cataract), damage to the retina (e.g. in age-related macular degeneration in which the central point of the retina perishes) or nerve diseases with visual impairments are possible. Another type of reduced visual acuity can result from certain circumstances in childhood (e.g. strabismus) without the doctor being able to recognize changes in the eye (amblyopia = weak vision).

The eye test is also carried out during expert opinions. In this way it can be determined whether and to what extent there is a reduction in earning capacity. The eye test can also serve as an aptitude test for, for example, a driver's license or for professions (e.g. police officer, pilot).

functionality

In an eye test, the patient must correctly name characters that are as small as possible and that are shown to him at a certain distance. The eye test is carried out on each eye separately. The symbols are either printed on a blackboard or projected onto a screen. Usually numbers or letters have to be recognized (Snellen test). Especially with children z. B. also symbols in the form of E's (Ploughman's hook) or C's (Landolt rings) in different orientations as well as children's pictures (Lea-Test) are used. The smaller the size of the characters that can still be properly seen, the better the visual acuity.

Usually an eye test is carried out in the distance (5 meters), but there is also a near vision test (30 centimeters). Any ametropia can be compensated for in an eye test with certain corrective lenses in order to determine the actual functionality of the eye.

The technical term for visual acuity is visual acuity. The visual acuity is given in numbers without a unit of measurement. With a visual acuity of 1.0, by definition, two points can still be distinguished with a distance of one angular minute. This is roughly the average value for people with healthy eyes.

If the visual acuity is reduced, the value of the visual acuity is also lower. If two points e.g. B. 5 angular minutes apart in order to be able to distinguish, the visual acuity is 0.2 (or: 1/5). Quite a few eyes also have a vision of more than 1.0 because of this definition. In adolescents, the visual acuity can e.g. B. often be 1.25. Sometimes the visual acuity is also given in percentages, but ophthalmologists always write it down in decimal numbers.

In the case of very poor vision, the symbols can no longer be recognized by the patient. Then the ophthalmologist tests the patient for finger counting, hand movement or light. If no light can be seen at all with one eye, "nulla lux" (Latin: no light) is noted.

procedure

Usually, visual acuity is checked at a distance (at a distance of 5 meters) during eye tests. The eye that has not been examined is covered with a flap, with the palm of the hand or with a piece of cardboard (behind the glasses) so that the patient can only look at the sample with one eye. Now the patient reads out the respective row of numbers or letters or describes the symbols that he recognizes.

The visual acuity can be read by the ophthalmologist on the board next to the optotypes that the patient can just barely recognize and is noted. If the patient cannot see anything in the distance on the vision test, he is offered a board 1 meter away. If he still does not recognize the signs, he has to count fingers, recognize a hand movement or perceive a light from a doctor's lamp.

In-depth eye tests initially consist of one part without the correction of ametropia, only then glasses are held in front of you or your own glasses are put on. In daily practice, it is usually sufficient for the patient to immediately take an eye test with self-correction.

Nearby visual acuity is checked using a similar eye test that involves holding a small eye test chart at a distance of 30 centimeters in front of the eye.

Alternative investigations

There are many methods that can be used to test the visual function of the eye. One way of examining the function of the retina when the lens or other media is clouded is to determine the retinometer vision. During the test, a strip of light is thrown onto the eye, the orientation of which the patient is supposed to recognize.

Very young children cannot yet correctly name test symbols. A test with a blackboard with stripes on one half and a single-colored field on the other half is well suited for them. The child usually looks at the side with the stripes (preferential looking).

There are several different tests to check various visual impairments, for example a color vision test, a visual field examination or an Amsler test, in which distortions and shadows in the field of vision can become noticeable.