|
Glasses, also called eyeglasses or spectacles are frames,
bearing lenses worn in front of the eyes normally for
vision correction, eye protection, or for protection
from UV rays. |
Modern glasses are typically supported by pads on
the bridge of the nose and by temples placed over
the ears. Historical types include the pince-nez,
monocle, and lorgnette.
|
|
Eyeglass frames are commonly made from metal, horn or plastic.
Lenses were originally made from glass, but many are
now made from various types of plastic, including CR-39
or polycarbonate. These materials reduce the danger
of breakage and weigh less than glass lenses. Some plastics
also have more advantageous optical properties than
glass, such as better transmission of visible light
and greater absorption of ultraviolet light.[1] Some
plastics have a greater index of refraction than most
types of glass; this is useful in the making of corrective
lenses shaped to correct various vision abnormalities
such as myopia, allowing thinner lenses for a given
prescription. |
| Scratch-resistant
coatings can be applied to most plastic lenses giving
them similar scratch resistance to glass. Hydrophobic
coatings designed to ease cleaning are also available,
as are anti-reflective coatings intended to improve
night vision and make the wearer's eyes more visible.[2]
|
Polycarbonate lenses are the lightest
and most shatter-resistant, making them the best for
impact protection,[1] yet offer poor optics due to high
dispersion, and having a low Abbe number of 31. CR-39
lenses are the most common plastic lenses due to their
low weight, high scratch resistance, and low transparency
for ultra violet and infrared radiation. Eyeglasses |
|
Not all glasses are designed solely
for vision correction, but rather for protection, viewing
visual information (such as stereoscopy) or simply just
for aesthetic or fashion values. Safety glasses are
a kind of eye protection against flying debris or against
visible and near visible light or radiation. Sunglasses
allow better vision in bright daylight, and may protect
against damage from high levels of ultraviolet light. |
|
How
can we discount eyeglasses so much? |
|
39 Dollar Glasses.com was developed
by eye doctors to create an inexpensive method for people
to acquire high quality, finished prescription eyeglasses
online. From their experience in both private offices
and retail establishments, the founders decided they
could provide this service for people inexpensively,
bypassing expensive retail establishments. |
|
We use the same high quality materials,
but can offer them at a high discount because of our
high volume, since we don't have the additional overhead
constraints (such as retail rent space, behind-the-counter
employees, and expensive displays) that your doctor's
office or optical must overcome. Since operating this
website is much less expensive than a typical retail
establishment, we are able to pass these savings on
to the general public online.
|
|
|
|
