Refractive Errors

Refractive Errors

What is normal vision?

In order to better understand how refractive errors affect our vision, it is important to understand how normal vision occurs. For persons with normal vision, the following sequence takes place:

Illustration demonstrating  normal vision
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  1. Light enters the eye through the cornea, the clear, dome-shaped surface that covers the front of the eye.
  2. From the cornea, the light passes through the pupil. The amount of light passing through is regulated by the iris, or the colored part of your eye.
  3. From there, the light then hits the lens, the transparent structure inside the eye that focuses light rays onto the retina.
  4. Next, it passes through the vitreous humor, the clear, jelly-like substance that fills the center of the eye and helps to keep the eye round in shape.
  5. Finally, it reaches the retina, the light-sensitive nerve layer that lines the back of the eye, where the image appears inverted.
  6. The optic nerve is then responsible for interpreting the impulses it receives into images.

What are refractive errors?

The following are the most common refractive errors, all of which affect vision and may require corrective lenses or surgery for correction or improvement:

Illustration demonstrating  astigmatism
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Illustration demonstrating  hyperopia
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Eyeglasses or contact lenses may help to correct or improve hyperopia by adjusting the focusing power to the retina. Corrective surgery may also help by changing the shape of the cornea to a more spherical, round shape instead of an oval shape.
Illustration demonstrating  hyperopia corrected
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Simulation photograph: normal vision Simulation photograph: myopia

Commonly known as nearsightedness, myopia is a condition in which, opposite of hyperopia, an image of a distant object becomes focused in front the retina, either because the eyeball axis is too long, or because the refractive power of the eye is too strong. This condition makes distant objects appear out of focus and may cause headaches and/or eye strain.

Illustration demonstrating  myopia
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Eyeglasses or contact lenses may help to correct or improve myopia by adjusting the focusing power to the retina. Corrective surgery may also help by changing the shape of the cornea to a more spherical, round shape instead of an oblong shape.
Illustration demonstrating  myopia corrected
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Illustration demonstrating  presbyopia
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