This will depend largely on the type of lenses you are referring to. However, many stores like Wal-mart and Walgreens offer discounts on eyeglass lenses if you make frequent purchases in their eyeglass department.
You can purchase new eyeglass lenses online through the Eyeglass Lens Direct website. You can also receive a new lens through local companies such as 1 Hour Lenses.
Eyeglass lenses could be made of nearly any plastic or glass. For example, some glasses lens, such as my own, are made of a plastic called polycarbonate which is the material used to make bulletproof glass so my glasses are impact resistant. Other eyeglass lenses can be made from other plastics and glasses such as CR-39, Homopolyer and crown glass.
dropping them.
Eyeglasses are plural. Each lens is an eyeglass.
That is something for you to discuss with your optician or optometrist. Technology on lenses changes and improves. What works for one person doesn't work for another - and cost is always a consideration.
Carl Zeiss sell a wide range of lenses including: eyeglass lenses, camera lenses, cinematography lenses and also lenses for technical applications which assist scientists and engineers.
Aspheric lenses are very good for individuals with a strong eyeglass prescription because they can be made thinner and lighter than conventional lenses.
According to Wikipedia, today's lenses are typically made from plastic, such as polycarbonate. Plastic is used in order to lessen the chance of breakage.
Because the oil from your skin and hair transfers to the lenses and smudges them up.
An optician makes the corrective lenses prescribed by an optometrist or ophthalmologist, creates the lenses, fits them to supporting structures such as eyeglass frames) and fits the whole to the person who will use them.
The raw material of lenses is plastic polymer in most cases. There are some lenses which are made from glass materials as well.