Safety Products Marketplace Guide to Photochromic Lenses

Photochromic lenses transition from clear to a moderate sunglass tint when they are exposed to UV light from the sun.  The greater the intensity of UV light, the darker they become.  In the absence of UV light the lenses remain clear. 

Photochromic, or transitional, lenses protect the eyes from UV rays and help them cope as they react to changing light conditions.  They are especially useful for people who will be wearing glasses all day and going back and forth from inside to outside, such as people who wear safety glasses at work, or prescription glasses.  With photochromic lenses one set of glasses takes the wearer from indoors to outdoors with comfort and protection. 

Because they react to UV light, there are some situations where they will not transition to a darker tint, such as driving a car with a UV blocking windshield.  Temperature is another factor that affects the performance of transitional lenses.  They react more quickly in cold weather.  Photochromic lenses are usually tested at a temperature of 72 degrees Fahrenheit as the standard.  In warmer temperatures they may react more slowly and not darken to the same degree. 

Brand new photochromic lenses have a break-in period during which they will not perform at their optimum level.  When you first purchase your photochromic glasses, allow them to be exposed to sunlight at least five periods of 30 minutes or longer to break them in. 

Photochromic lenses are available in both glass and plastic.  In the early days of transitional lenses the glass lenses were superior for a fast reaction and darker tint, but new innovations in the plastic lenses make them equal in performance and very versatile.  Glass lenses often weigh twice as much as plastic and are not shatter resistant.  Plastic lenses are lightweight and shatter and scratch resistant.  The polycarbonate lenses used on safety glasses are shatter proof.  Plastic lenses should be replaced approximately every 2 years because they do gradually lose some of the ability to transition.

Photochromic lenses offer exceptional protection for your eyes from harmful UV rays.  You may not even realize that your eyes are being exposed to UV rays, but your transitional lenses will respond and darken to protect you.  You can wear them inside the house or office as clear lenses and then wear the same pair outside with confidence that your eyes are protected.


Safety Products Marketplace:  Keeping an Eye on Your Safety