Frequently Asked Questions about
Sunglasses

Q: What Lens Types are Available?

• Clip-on lenses: These are used on top of prescription lenses. They are convenient, but may not fully cover the lens. Together with the lens surfaces of the regular glasses, clip-on lenses may cause reflections. They may scratch prescription lenses or fall off.
• Gradient lenses: Sunglasses can be of gradient density (dark on the top, tapering to light at the bottom) or double gradient density (dark top and bottom, lighter in the center). They come in handy when sunlight comes from overhead, or is reflected into the eyes from below.
• Mirrored lenses: Lenses can be coated with a thin metallic film, which looks like a mirror and reflects light rays, further reducing the amount of light that can reach the eye.
• Photochromatic lenses: This type of lens changes according to the amount of light. They darken in bright light and lighten in dim light. These lenses are helpful under a wide variety of light conditions. The amount of light, lens thickness and temperature all affect how dark the lenses will get. One problem with these lenses is that they may not change quickly enough to adjust to new light situations.
• Polarizing lenses: These lenses, which reduce glare and "bounce-up" reflections from flat surfaces, are useful for driving, boating, fishing and other activities where there is glare off the water of the ground.

Q: What Color Lenses Do I Need?

Neutral gray or "smoke" lenses allow for best color perception. Other good choices are amber and brown tints (which usually block more blue light), or green. Dark lenses may be preferred by those whose eyes are very sensitive to light. Tints such as red, orange, blue or purple are unsuitable because they may interfere with color perception and tend to let in too much light. Since all of the colors we see are made up of visible light, tint is not related to the degree of UV protection provided.

Q: How Do I Know My Lenses are Safe?

Lenses should be inspected for flaws such as scratches, bubbles and distortions. Poorly-made glasses will not damage the structure of your eyes. But flaws and distortion in the lenses may cause your eyes to work harder. That can result in squinting, blinking, tearing and even slight headaches, nausea and dizziness. The Food and Drug Administration requires that all lenses be impact resistant and made of optical-quality glass or plastic. These are valuable with or without a corrective prescription. This does not mean the lenses are shatterproof or unbreakable, but that they can withstand moderate impact.

Glasses for ball sports or sports with physical impact should be made of polycarbonate, which is the most shatter-resistant material widely available today. Polycarbonate is also the best choice for children's sunglasses.

Copyright ©2010 Prevent Blindness America

Last updated September 12, 2011

Printer-friendly format