Vision is a truly amazing phenomenon. When you look at an object, light rays bouncing off the object enter the front of our eye through a transparent, domed window called the cornea. The cornea bends (refracts) the incoming light, causing it to focus on light-sensitive receptors in the retina at the back of the eye. The brain interprets this, and you perceive an image of the object.
Vision problems occur when the light rays passing through the cornea and lens do not focus on the retina. The most common vision problems are:
Myopia (nearsightedness) |
| Causes: |
The cornea is too steep, or the eyeball is too long, causing the image to be focused in front of the retina. |
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| Vision problems: |
Close up objects can be seen clearly, but distant objects appear blurred. |
Treatment:
|
Refractive surgery removes tissue from the center of the cornea to make it flatter. This spreads out the light rays to focus the image on the retina. |
Hyperopia (farsightedness) |
| Causes: |
The cornea is too flat, or the eyeball is too short, causing the image to be focused behind the retina. |
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| Vision problems: |
Distant objects are typically clearer than objects viewed up close. |
Treatment:
|
Refractive surgery flattens the mid-corneal periphery so that the central cornea is made steeper. The reshaped cornea bends the incoming light more to focus the image on the retina |
Astigmatism |
| Causes: |
The cornea is unevenly curved, causing light rays to be bent unequally. |
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| Vision problems: |
Objects appear distorted or blurred at all distances. |
Treatment:
|
Refractive surgery removes tissue where necessary to make the cornea more spherical. Refractive surgery can treat astigmatism alone, or when found in conjunction with myopia or hyperopia. |
Presbyopia (older age vision) |
| Causes: |
The crystalline lens inside the eye gradually loses its ability to change shape, resulting in the inability to shift from distance to near vision. This is a natural aging condition that effects everyone, usually beginning near the age of 50. |
| Vision problems: |
Gradual loss of the ability to focus on near objects. |
Treatment:
|
Presbyopia has traditionally been corrected with bifocals and bifocal contact lenses, but can now be partially treated using combinations of refractive surgery. |
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