Monnett Eye & Optical Center

Normal Vision

Normal vision occurs when light is focused directly on the retina rather than in front or behind it.

Vision or visual acuity is tested by reading a Snellen eye chart at a distance of 20 feet. By comparing large numbers of people, medical professionals have determined what a "normal" human being should be able to see when standing 20 feet away from an eye chart. If you have 20/20 vision, it means that when you stand 20 feet away from the chart you can see what a "normal" human being can see. (In metric, the standard is 6 meters and it's called 6/6 vision). In other words, if you have 20/20 vision your vision is "normal" — a majority of people in the population can see what you can see at 20 feet.

Light focuses directly on the retina

A person with normal vision can see objects clearly both near and faraway because the visual image is focused directly on it the retina.

The eye is a complex optical system - that sends signals to the brain. It works very much like a camera. Vision begins when light enters the eye through the cornea, a very powerful focusing surface. From there, it travels through the pupil. As muscles in the iris relax or constrict, the pupil changes size to adjust the amount of light entering the eye. The light rays then pass through and are further focused by the lens.

When light rays finally land on the retina, the part of the eye similar to film in a camera, they form an upside-down image. The retina converts the image into an electrical impulse that travels along the optic nerve to the brain, where it is interpreted as an upright image through the brain's powerful interpretive process known as "NEUROADAPTATION"

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