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Have you ever wondered; how do contact lenses work?
By Steve Cogger
Have you ever wondered; how do contact lenses work?
If you wear lenses, or even if you don't, chances are you have asked
yourself, "how do contact lenses work?ˇ± After all, it's just a little piece of
plastic. It's amazing that without them, your vision can seem awful. And
with a little thin lens, everything is clear. So let's take a closer look; how
do contact lenses work?
In their simplest form, contact lenses are nothing more than an optical
lens; similar to that in a pair of eyeglasses, only much smaller and of a
different material.
For the nearsighted eye, the lens is a minus power. On eyeglasses, this
makes for a thin center and thick edge. The same goes for contact
lenses, a very thin center and a thicker edge. The variation of the thin to
thick makes up the power of the lens. For example, a -14.00 lens has
thicker edges than a -2.00.
The inside curve of the lens, also called the base curve, is designed for
optimum fitting on the cornea. Base curves are measured in mm of
radius. For example, a base curve of 8.6 means that the lens has the
same inside curves of a circle with a radius of 8.6mm.
Another major factor in answering how do contact lenses work?, the
diameter. Diameter is measured edge to edge, also in millimeters. The
diameter is altered for physical fit and comfort. Any time the diameter is
changed, the base curve needs to be revised. For example, a lens with a
base curve of 8.6 and a diameter of 13.8 will be overall flatter than a lens
with a base curve of 8.6 and a diameter of 15.0.
To picture this in your mind, picture a circle and imagine the top quarter
of the circle is a lens. Now imagine the top half of a similar circle is a
lens. Can you begin to see how different those two lenses would be?
Contact lenses only work properly when they have the proper
prescription and they are fit correctly. A contact lens that is too steep will
not only be uncomfortable, it will also create a blurry image because of
the distance between the front of your cornea and the back of the lens. A
lens that is too flat will not center properly and the edges will buckle or lift
off the white of the eye.
Once properly fit, the lens must stay hydrated in order to work properly.
On soft contact lenses, this is accomplished simply by blinking. Think of
your lids as windshield washers that constantly clean the lens. If you
wear lenses, you may notice that they blur a little after long term
computer use. This is directly related to the fact that a persons blink rate
slows when focusing on anything up close, i.e. the computer screen.
As you can see the optical qualities, proper fitting, and constant blinking
are the main factors when figuring how contact lenses work.
About the Author
Steve Cogger helps thousands of contact lenses wearers find the perfect lens for their eyes. His busy New York practice specializes in all lens modalities. For more consumer information and education, http://www.All-About-Contact-Lenses.com
Article Source: http://www.simplysearch4it.com/article/6106.html
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