Gauging the Weather: How Extreme Temperatures Affect Light-Reactive Lenses

Heavy jackets, boots and gloves…winter is here, and for people who call the Midwest or East Coast home, this means snow, lots of that beautiful powdery stuff that blankets front yards and streets.  Frigid weather brings change for patients, but for those who wear light-reactive lenses (photochromics), it also means a change in how their lenses perform. 

Light-reactive lenses react differently in extreme temperatures, both hot and cold, because temperature is an important catalyst that impacts the chemical reaction in the photochromic dyes in the lens. However, a light-reactive lens can be an invaluable asset for vision clarity and ocular protection in extreme temperatures.

How Do Photochromic Lenses Work?

The technology behind light-reactive lenses is quite remarkable when you think about it. These specialized lenses include molecules that respond to the UV rays emitted by sunlight. When exposed, the size and color of the molecules change, opening up the individual photochromic dyes like umbrellas to expose the dye elements (the color elements of the lens). This allows them to absorb more visible light, and the lens darkens or tints to its activated state. Indoors, when UV rays are not present, the process reverses, and the lenses return to clear in a few minutes, or in the case of SunSync^® Elite in under a minute.¹

Loyal fans of light-reactive lenses love the convenience of not having to switch glasses when going from inside to outdoors, but there are many other benefits as well. Light-reactive lenses like SunSync Elite and Sun Sync Drive XT, which retains its tint behind the wheel, provide 100% UV protection. Overexposure to UV rays can lead to damaging effects for patients, and while most people wouldn’t think twice about wearing sunglasses on a bright, sunny day, it’s just as important to protect eyes on snowy days. Snow reflects UV rays, and exposure to this invisible hazard can be intense.

Chemistry 101: Photochromics in Extreme Temperatures

Light-reactive lenses do a great job of keeping patients protected from powerful UV rays, but as impressive as these lenses are, there are temperature factors all wearers should know. Light-reactive lenses perform differently in extreme temperatures, both hot and cold. In very cold environments, the molecules get a bit sluggish. Remember your high school chemistry class. When molecules are heated, they move faster; when they are cold, they move slower. This means it takes longer for the lenses to return to clear in extremely cold temperatures. The upside is that extreme cold tends to "shock" the photochromic molecules into an optimum state of activation, resulting in a darker tint, a factor patients will appreciate on sunny days.

Light-reactive lenses are also impacted by extremely hot environments but in the opposite way. In high temperatures, the molecules move more quickly so activation time (clear to dark) will be swifter. However, the chemical reaction triggered by a higher temperature means that the lenses will not get as dark when exposed. This is the case in all photochromic lenses, no matter what brand a patient chooses. 

While there‘s no need for dispensers to get into scientific detail about performance in extreme temperatures, it’s important that patients know this upfront. This way you can avoid the phone call or email later from new wearers who thought the lenses would be darker or turn back to clear more quickly. This is especially true if you are located in places like Arizona or Texas where extreme heat is common, as well as the East Coast and Midwest where temperatures can dip below zero. While all photochromics will perform differently in these temperatures, most wearers will find that the differences are subtle. The industry standard temperature for measuring photochromic performance is about 73 degrees, so variances in temperature in our environment above or below that temperature means variances in performance.

SunSync for Comfort, Convenience, and Clarity in Any Weather

Photochromics like SunSync Elite and SunSync Drive XT will vastly improve the patient experience with fast activation and deactivation and excellent visual clarity indoors and outdoors. If you dispense SunSync, be sure to remind patients about what separates these lenses from any other photochromic lens in the market. 
SunSync Elite provides one of the fastest fade-back speeds in the industry (2x faster than the competition²), and our improved version is now a darker outdoors and extra-clear indoors. These lenses offer exceptional blue light reduction and 100% UV protection.  

SunSync Drive XT is an extra-dark light-reactive lens and one of the few photochromic lenses that stays dark inside a vehicle. In addition, these lenses also offer fast activation and fade-back speed, 100% UV protection, and “always on” blue light reduction. 

If you’re ready to find out just how well these lenses perform—in all temperatures—ask for a free personalized demo, and remember that both SunSync Elite and SunSync Drive XT offer a one-year satisfaction guarantee for your VSP customers. Check out the comparison chart to learn more about SunSync Light-Reactive Lenses.

1. t½F of SunSync Elite in polycarbonate is 51 seconds at 73.4°.
2. In independent testing, SunSync Elite fades from fully activated to 56 %T in 40 seconds compared to 54.5 %T in 120 seconds for Transitions^® Signature^® Gen 8™. Testing conducted in Polycarbonate to ISO 8980-3 standard.