Human beings have an ability to see things because of the functioning of their eyes and the computation of the images received in the brain. A vision test is a diagnostic procedure that is used to examine a person's ability to see things. For adults, a vision test is usually used for the purpose of prescribing glasses in order to correct any abnormality. Other conditions may be diagnosed easily in an adult because an adult is capable of expressing the effect that the condition is having by explaining the symptoms to a doctor. A child, particularly an infant, is unable to speak or may not have a vocabulary developed enough to properly describe the symptoms being experienced. Apart from refractive errors which require glasses, there are many other conditions that can affect a person's eyes. These conditions can be reversed during childhood or can be prevented from worsening. This is especially important for progressive conditions which may even render a person blind. Hence, an early diagnosis of any of these conditions is extremely important.
The development of a child's visual ability is a gradual process. At the early stages of infancy, the child has an underdeveloped sense of vision and usually fixates on a particular object that seems interesting. There is a gradual increase in visual skills as each month of infancy progresses. It is only by the age of 3 that the eyes are completely developed with mature tissue and a fully grown nervous system.
Because children are unable to speak or read properly, other tests must be used instead of the standard vision chart test. A basic vision test for children is to note their ability to focus on an object and follow the object as it is moved. This is the most basic form of vision test. Another vision test for children is the preferential looking test which uses two different images, one being blank and the other having various bars. As the bars appear closer and closer, the child's preference for each image becomes equal. This preference is followed by a trained doctor as the child is subjected to successive images.
There are other complicated tests that are used as vision tests for children. These may be used if the above mentioned procedures produce unclear results. Routine screening for vision problems is recommended in all children and especially recommended for children who have a family history of vision related problems.