 |
Understanding Refractive Errors
|
|
Click on image to enlarge... |
Clear vision is the result of light entering the cornea (the clear
"outer window" of the eye), passing through the focusing
lens inside the eye, and coming to a single point of focus on the
retina. The most common types of visual distortions are nearsightedness,
farsightedness, and astigmatism. Doctors call these types of visual
distortions lower order aberrations. They are responsible for approximately
85% to 90% of the overall quality of your vision. |
|
Click on image to enlarge... |
Nearsightedness occurs when the cornea is too steep or the eye is
too long. This causes light rays entering the eye to focus at a point
in front of the retina. People who are nearsighted have difficulty
seeing distant objects. |
|
Click on image to enlarge... |
Farsightedness occurs when the cornea is too flat or the eye is
too short. This causes light rays entering the eye to focus at a point
behind the retina. People who are young and farsighted can often see
at a distance but have difficulty seeing close objects. As one ages,
both near and distance vision become difficult. |
|
Click on image to enlarge... |
Astigmatism occurs when the cornea is shaped like a football, steep
in one direction and flat in the other direction. This causes light
rays entering the eye to focus at multiple points within the eye,
causing double and/or blurred vision. People who are nearsighted or
farsighted also commonly have astigmatism. |
