| |
|
In addition
to nearsightedness or farsightedness, astigmatism occurs frequently.
Images of objects at a close as well as a far distance appear distorted.
Astigmatism occurs when the curvature of the cornea is asymmetric.
The normal cornea is shaped spherically, similar to the lens of a camera.
Therefore, horizontal as well as vertical lines are are refracted to
form a focused image. A dot-like source of light such as a street light
will produce a dot-like image. If the curvature of the cornea is not
spherical, but rather elliptic, the light rays are focused at different
points and the image will be distorted. A point, for example, will not
produce the image of a point but a small line. In our example the street
light will not produce the image of a bright dot but a small line.
|
|
|
|