In fact, average vision is probably better now than before because of the greater use of eyeglasses. The eye, as a whole, does not react very quickly to changes in light levels. For example, the eye does not react nearly as fast to sudden large changes in light as does the ear to sudden large changes in sound. Although the eye is useful over a wide range of illumination, it takes time to adjust to a particular level. Common artificial lighting does not impose any extra demands on a person's vision and, in many cases, it may be superior to natural lighting.
Artificial light is easy to control and to direct into a specific area.
A properly lighted environment may be maintained artificially for long periods of time, regardless of outside, or natural, conditions. Artificial light, however, may produce lighting imbalances that exceed those commonly found in the natural environment. In night driving, for example, the natural lighting imbalances are exceeded when the driver tries to see the road but has oncoming headlights in the field of view. The percentage of light reflected by a surface is essentially a constant. As the natural light level changes, the amount of light reflected from the various surfaces in the environment changes proportionately.