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American Family Children's Hospital
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How the Eye Works

To understand how refractive surgery at UW Health corrects your vision, it helps to understand how the eye works. The eye functions like a camera. Light comes in through the cornea, which focuses the light rays as they pass through the pupil and the lens. The iris, which surrounds the pupil, works like a camera shutter and controls the amount of light that enters the eye.
 
In normal eyes, the cornea and lens bend light so that it focuses directly on the retina, the light sensitive tissue in the back of the eye. The retina changes light into electrical impulses that travel via the optic nerve to the brain.
 
Poor vision results when the cornea and the lens focus light too far in front of or behind the retina. Corrective lenses work by allowing the light to focus directly on the retina.
 
What is nearsightedness (myopia)?
 
When someone is nearsighted, light entering the eye is focused in front of the retina, instead of directly on it. People with myopia see near objects more clearly, while far objects appear blurry and out of focus.
 
Myopia is an inherited condition, which usually starts in childhood and stabilizes in the late teens or early twenties.
 
What is farsightedness (hyperopia)?
 
Farsightedness or hyperopia is a condition that occurs when light entering the eye is focused behind the retina.  People with mild farsightedness have difficulty seeing objects up close but distant objects may be seen clearly.  Higher amounts of hyperopia may result in the inability to see objects well at any distance.
 
What is astigmatism?
 
Astigmatism is the eye condition that occurs when the curvature of the cornea is not uniform, causing light to fall unevenly on the retina. This irregularity makes objects appear blurry or "ghosted."