In the beginning, all lenses were made from glass. However,
glass lenses, even safety tempered glass, carry a higher risk of injury
due to shattering from impact. For this reason, we do not offer
glass lenses to our patients as there are safer and better
When evaluating lens materials, there are
typically five factors that eyeglass wearers to consider: thinness
of the lenses, amount of color distortion, weight, ultraviolet
protection, and strength/impact resistance of the material.
The thinness of a lens material is
characterized by its index of refraction or the amount light
bends. A higher index of refraction for a lens material means it
will be thinner for the same prescription than a lower index of
Certain lens materials distort colors
more than others. A large amount of color distortion or chromatic
aberration are ideal for diamonds which sparkle many colors but not
ideal for color true vision. Color true vision helps to see
objects in their real hues.
Different lens materials will have
different weights even when the lenses are identical in prescription and
lens diameter much like a box of feathers versus a box of bricks of the
Lens materials can filter or allow
different amounts of ultraviolet rays from the sun. Large amounts
of ultraviolet A rays are considered harmful to eyes and are known to
contribute to age related cataracts.
The strength of the lenses is important
especially for those who might need eye protection against projectiles
and chemicals. A stronger lens material could help in situations where
your eyewear and eyes are at risk for impact (e.g. racquetball,
volleyball, bicycle riding, working in a laboratory). These lenses
are strongly recommended for children and those with one good eye.
Below we list some of the lens materials
we offer for our eyewear with some pros and cons for each.
Plastic CR-39, Index
cost. Excellent chromatic vision properties.
Cons: Allows over 10% ultraviolet A. One of the weaker materials.
Weight is heavier due to greater thickness.
cost. Thin Lens. Very Strong Impact Protection. 100% UVA protection.
Cons: Prone to chromatic distortions especially in high
cost. Very Strong Impact Protection. 100% UVA protection. Very Good
chromatic vision properties.
Cons: Not as thin as other materials.
EYRY, Index of
of thinnest plastic materials. Strong Impact Protection. 100% UVA
protection. Good chromatic vision properties.
Cons: High Cost.
419 Eccles Ave. South
San Francisco, CA 94080
Tel: (650) 873-1089, Monday-Friday 11:00AM to 5:00PM