Photochromic Lenses: Transitions
and Other Light-Adaptive Lenses
Photochromic lenses are eyeglass lenses that darken automatically when exposed to sunlight, then fade back when you return indoors. In most cases, photochromic lenses are clear (or nearly clear) indoors and darken to a medium sun tint outdoors. But there are exceptions.
Because the most popular photochromic lenses sold in the United States are made by Transitions Optical, many people including some eye care practitioners mistakenly call all photochromic lenses "transitions lenses" or "transition lenses." But there are many brands of photochromic lenses offered by different lens manufacturers (see below).
Other generic terms sometimes used for photochromic lenses include "light-adaptive lenses" and "variable tint lenses."
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The molecules responsible for causing photochromic lenses to darken are activated by the sun's ultraviolet radiation. Because UV rays penetrate clouds, photochromic lenses will darken on overcast days as well as sunny days. But because the windshield and window glass of cars and trucks blocks most UV rays, photochromic lenses typically won't get as dark inside a vehicle as they do outdoors.
Photochromic lenses are available in nearly all lens materials and designs, including high-index lenses, bifocals and progressive lenses. An added benefit of photochromic lenses is that they shield your eyes from 100 percent of the sun's harmful UVA and UVB rays.
Because a person's lifetime exposure to sunlight and UV radiation has been associated with cataracts later in life, it's a good idea to consider photochromic lenses for children's eyewear as well as for eyeglasses for adults. Polycarbonate is the safest lens material for kids, providing up to 10 times the impact resistance of other lens materials.
Though photochromic lenses cost more than clear eyeglass lenses, they offer the convenience of reducing the need to carry a pair of prescription sunglasses with you everywhere you go.
Indoor/Outdoor Photochromic Lenses
Popular brands of all-purpose, indoor/outdoor photochromic lenses sold in the United States include:
Light-adaptive lenses can be placed in just about any fashion frame. They're convenient for everyday use as well as travel.
Transitions Signature (Transitions Optical) Transitions Signature lenses (also called Transitions Signature VII lenses) represent the seventh generation of Transitions photochromic lenses. Introduced in 2014, Transitions Signature lenses are available in a wide variety of lens materials and designs, in either a gray or brown light-adaptive tint. The lenses are clear indoors, get 15 to 21 percent darker outdoors than previous Transitions lenses, and are preferred 2-to-1 over previous-generation Transitions lenses, according to the company.
LifeRx (Vision-Ease Lens) LifeRx lenses are made of polycarbonate and are available in gray and brown photochromic tints in a variety of lens designs. The lenses take less than a minute to darken outdoors and fade back faster indoors than other photochromic lenses, according to the company.
PhotoFusion (Carl Zeiss Vision) Made in Germany, PhotoFusion lenses are available in a neutral gray tint for accurate color vision in all lighting conditions, according to the company. The lenses darken up to 20 percent faster and lighten indoors up to twice as fast as previous Zeiss photochromic lenses.
ColorMatic (Rodenstock) Also made in Germany, Rodenstock's ColorMatic lenses are available in gray, brown and green photochromic tints. The company also offers ColorMatic IQ Contrast photochromic lenses in contrast-enhancing shades of orange and green.
PhotoViews (Signet Armorlite) PhotoViews lenses are made of lightweight plastic and are available in gray and brown photochromic tints in a variety of lens designs.
SunSensors (Corning) Corning's SunSensors are made of mid- and high-index plastic materials and are available in gray and brown tints in a variety of lens designs.
PhotoGray; PhotoBrown (Corning) These glass photochromic lenses offer superior scratch resistance but are significantly heavier and less impact resistant than other photochromic lenses. Corning created the first mass-produced glass photochromic lenses in the 1960s and continues to produce glass photochromic lenses in gray and brown tints.
Thin & Dark (Corning) Corning's Thin & Dark lenses feature a gray tint and are up to 30 percent thinner and lighter than conventional glass photochromic lenses, according to the company.
To overcome the issue of photochromic lenses not getting dark enough for some wearers either outdoors or inside a vehicle Transitions Optical has introduced three light-adaptive lenses that might better be described as "photochromic sunglasses."
Fasano sunglasses, by Serengeti Sport, have photochromic lenses with an anti-glare coating.
These lenses are primarily for outdoor wear and are not as clear indoors as other photochromic lenses, but they provide extra comfort in bright sunlight and behind the wheel:
Transitions XTRActive (Transitions Optical) These lenses are darker than Signature VII lenses (both indoors and outdoors) for wearers who are light-sensitive indoors and desire a darker lens when driving and outdoors. Available in gray tint only.
Transitions Vantage (Transitions Optical) These lenses have a light tint indoors and become polarized as they darken outdoors for greater glare control in bright, reflective conditions. Transitions Vantage lenses do not darken inside a vehicle, however. Available in gray tint only.
Transitions Drivewear (Transitions Optical and Younger Optics) These are polarized sunglasses specifically designed for optimum driving vision in variable daylight conditions. Depending on lighting conditions, Drivewear lenses change from green/yellow to copper to dark red/brown. Because they remain significantly tinted at all times, these photochromic lenses are not recommended for indoor or night-time wear.
Medical Applications of Photochromic Lenses
In addition to adjusting automatically to different lighting conditions, some photochromic lenses also have medical applications.
Corning's CPF family of glass photochromic lenses has specially selected red colors. These lenses sometimes are used to enhance the vision of patients who have various eye pathologies, including macular degeneration. Doctors who specialize in low vision are familiar with these lenses and can determine if they will be effective for specific vision problems.
Non-Photochromic Tinted Lenses
Alternatives to photochromic lenses for improving visual comfort are lenses with tints that remain constant at all times.
Tints of virtually any color can be applied to eyeglass lenses. Lighter, fashion tints are used primarily for cosmetic purposes to enhance a wearer's looks. Darker tints allow the wearer to use the lenses as sunglasses.
Color can be added to a lens as a solid tint, where the entire lens has the same color density, or as a gradient tint, where the color density is darkest at the top of the lens and gradually fades to clear or nearly clear at the bottom.
Different colors can be applied to lenses for different purposes:
Yellow often is added to a lens to enhance contrast, especially in overcast conditions, making it a popular tint for hunters who desire "shooting glasses."
Green, or its cousin G-15 (the classic color of lenses in Ray-Ban sunglasses), is sometimes used as a sunglass tint, though brown and gray are the most popular sun shades.
Red is a bold fashion color and also is popular among people who enjoy seeing the world through "rose-colored glasses."
About the Author: Gary Heiting, OD, is senior editor of AllAboutVision.com. Dr. Heiting has more than 25 years of experience as an eye care provider, health educator and consultant to the eyewear industry. His special interests include contact lenses, nutrition and preventive vision care. Connect with Dr. Heiting via Google+.
[Page updated February 2014]
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