A vision test is an examination, in which the visual acuity is determined. The vision is a measure of the smallest details that a person can distinguish. The examination is carried out when someone has eye problems.
There are several reasons to have problems with vision. The result of a vision test is an advice for glasses. The test data can also be used as comparison material in case the patient will have eye problems in the future.
In the test, a score is acquired that indicates how well a person can see. An eye is called normal if the vision is 1.0 or higher. A vision of 0.0 is total blindness and everything in between is actually visual impairment. A value of 1.5 occurs in young healthy people.
In order to determine the vision, a letter chart can be used, the Snellen chart. With this chart can be determined whether the vision deviates from the average vision.
The Snellen chart is positioned at about 6 meters distance in a well-lit place. If the reference letters for 6 meters can be read at that distance, then the vision is equal to 1. If a person can read letters even smaller, then the vision is higher than 1.
If the largest letter cannot be distinguished, the visual acuity can be examined by having fingers counted of a raised hand. If the vision is so low that no fingers can be counted, the visual acuity can be determined by the observation of hand movements. If vision is so poor that even hand movements cannot be detected, then can be verified whether the patient may or may not see a light.
The visual acuity of each eye is usually measured separately. The examination takes up to 15 minutes.