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Eyeglasses allow rays of light to bend so to help your eyes focus correctly.
If a person is nearsighted, it means their eye is too long and that the light rays focus in front of their retina. So a concave lens is used to scatter the light a little so the convergence point of the light is directly upon the retina.
If a person is farsighted and cannot see up close, it is because their eye is essentially too short, making the light focus somewhere behind the retina. So a convex lens is used to concentrate the light and cause it to converge directly upon the retina. Similar is true in the case of reading glasses, except that the eye is unable to push its own lens forward enough (the process of accommodation) to cause near print to focus properly on the retina, so reading glasses or an additional lens that is more convex than the main lens is used.
Astigmatism is when the eye is out of round, and more cylindrical shaped. So a toric lens is used, or one of the above types of lenses (spherical prescription) are modified to be more toric (cylinder prescription).
There are also high order refractive errors which cause halos and other distortion. These are most common after eye surgery, and is because the lens or surface of the cornea is uneven. Correcting these takes specialized equipment to make specialized lenses that are customized to the patient. Advanced math formulas are used to map out the surface of the lenses needed to correct this. Then specialized lasers are used to make contact lenses or to alter the power of a layer of special material embedded into eyeglass lenses.
You can read more about how eye glasses work by clicking on the related links.
What else can I help you with?
What type of eye protection should you wear when using high intensity light?
When using high intensity light you should use eye protection that is designed to reduce the light intensity sufficiently that your eyes will not be injured. Selecting the correct eye wear requires knowing how bright the light is and at what wavelengths the light is produced. Just picking up a pair of dark glasses may not provide the needed level of protection.
I'm thinking of using a pair of 3D glasses that you got from a 3D movie and use it this 4th of July for firework glasses-- Are 3D glasses and Firework Glasses the same thing?
No. Firework glasses use diffraction to make light from the fireworks look different. 3D glasses use polarization to block either vertical or horizontal light coming through the lenses deending on which lense you look through.
Reading glasses use what property of light waves to help people see better?
Reading glasses use the property of light waves called refraction. The lenses in reading glasses help to focus light rays onto the retina at the back of the eye, making objects appear sharper and clearer.
What is the collective noun for perspective glasses?
The standard collective noun for 'glasses' is a pair of glasses, which can be used for a pair of Perspective glasses. Note: The noun Perspective, in this use, is the name of a specific brand of glasses, a proper noun. Proper nouns are always capitalized.
What are diffraction glasses?
Diffraction glasses differ from traditional glasses because they use a special pair of lenses that offer light grating as an entertainment source. When viewing a light source the grating effect will break the light into a prism of colors, offering the user a unique experience. You can check out companies like GloFX to view the various glasses that will feature this special lens. They also have a great FAQ page about diffraction glasses, you can read up on it by searching GloFX Glasses What Are Diffraction Glasses.
Can I use 3d tv glasses as my eye sight specs?
No dear, you cannot use your 3d tv glasses as your eye specs. Since, 3d tv glass is using special film on their lenses which will not allow you to use as an eye specs.
What can you use to keep eye glasses from slipping down?
Wedgees eye glass retainers are the best way to secure your glasses. They are inexpensive and work great. They can be purchased at WWW.wedgees.com I bought a pair a few years ago and have been buying them for friends ever since.
What is the need and use and type of eye and hearing protection?
you can use earplugs, goggles, glasses
What should you use to clean glasses?
eye glass cleaning cloth
Buy A Pair Of Protective Glasses?
Before you use any power tools, you should have a pair of protective eye glasses that you can wear. These are very inexpensive. They are generally made from thin plastic. While this does not sound like much, it can keep you very safe. The glasses will keep little particles from flying up into your eyes when you are drilling a hole in a metal pipe or sawing a board in half. You could need medical attention for the serious injuries that can occur if you are struck in the eye, so buying these cheap glass is well worth the price.
Is the word glasses considered as a singular noun?
Glasses is plural for a glass for holding liquid.Glasses is singular for a pair of glasses, eyeglasses; the plural form is pairs of glasses.
Why opticians use mirror to test eyesight of patient?
Opticians use mirrors during eye exams to perform a retinoscopy, a technique that helps determine the patient's eyeglass prescription. By shining a light into the patient's eye and observing how the light reflects off the back of the eye, the optician can assess the patient's refractive error and determine the appropriate prescription for glasses or contact lenses.
