Sunglasses

Sorting Out those Conflicting Claims

New sunglasses have been designed to protect eyes from the sun´s harmful effects. They promise protection from ultraviolet light and other kinds of natural radiation. It is more important to protect your eyes from some kinds of light than others.

Blocks 99% of ultraviolet rays Always buy sunglasses with this feature. Long-term exposure to ultraviolet (UV) radiation in sunlight is linked to eye disease. Both plastic and glass lenses absorb some UV light, but UV absorption can be improved by adding chemicals to the lens material during manufacturing or by applying special lens coatings. Shop for sunglasses that block 99 or 100% of all UV light. Some manufacturers labels say UV absorption up to 400nm. This is the same thing as 100% UV absorption.Blocks 90% of infrared rays Infrared wavelengths are invisible (they are longer than light rays that you can see) and produce heat. Sunlight has low levels of infrared rays, and the eye tolerates infrared well. Some sunglasses manufacturers make health claims for their products based on infrared protection, but research has not shown a close connection between eye disease and infrared rays.Blue-blocking Whether blue light is harmful to the eye is still controversial. Lenses that block all blue light are usually amber and make your surroundings look yellow or orange. The tint supposedly makes distant objects appear more distinct, especially in snow or haze. For this reason, amber sunglasses are popular among skiers, hunters, boaters and pilots.Polarized Polarized lenses cut reflected glare - sunlight that bounces off smooth surfaces like pavement or water. They can be particularly useful for driving and fishing. Polarization has nothing to do with UV light absorption, but many polarized lenses are now combined with a UV-blocking substance. Check the label to make sure the lenses provide maximum UV protection.Mirror-coated Mirror finishes are thin layers of various metallic coatings on an ordinary lens. Although they do reduce the amount of visible light entering your eyes, do not assume they will fully protect you against UV radiation.Wraparound Wraparound glasses are shaped to keep light from shining around the frames and into your eyes. Studies have shown that enough UV rays enter around ordinary eyeglass frames to reduce the benefits of protective lenses. Large-framed wraparound sunglasses can protect your eyes from all angles.Gradient Gradient lenses are permanently shaded from top to bottom or from top and bottom toward the middle. Single-gradient lenses (dark on top and lighter on the bottom) can cut glare from the sky but allow you to see clearly below. They are useful for driving because they don t dim your view of the dashboard. But they re not as good on snow or at the beach, especially if they re clear on the bottom. Double-gradient lenses (dark on top and bottom and lighter in the middle) may be better for sports where light reflects up off the water or snow, such as sailing or skiing. Double-gradient lenses are not recommended for driving, because they make the dashboard appear dim.Photochromic A photochromic lens automatically darkens in bright light and becomes lighter in low light. Most of the darkening takes place in about half a minute, while the lightening takes about five minutes. They come in a uniform or gradient tint. Although photochromic lenses may be good UV-absorbent sunglasses (again, the label must say that), it takes time for them to adjust to different light conditions.Judith Lee