Transition or photochromic lenses begin as clear prescription lenses and darken when sunlight or UV rays are exposed. They return to a clear state when no longer exposed to light or UV rays. The activation of these molecules is influenced by temperature; when the lenses are cold, they react more slowly, taking more time to fade back to a clear state.
UV Light
Many things can affect how dark your transition lenses appear in direct sunlight. The most important factor is how much UV light they’re exposed to. UV rays cause the molecules in transition lenses to darken and change shape, reducing their visible light transmission (making them look darker). When outdoors in bright sunlight, your transition lens colors will gradually darken within about 35 seconds. When the UV rays are gone, your lenses will return to their clear state. You can also speed up the process of your lens’s darkening by using a UV lamp to activate them. This can be useful if traveling to an unfamiliar environment where you may need access to a natural UV source. Transition lenses are one of the most popular photochromic lenses and can be added to any single-vision, multifocal, or bifocal lens. They offer convenience and eye health protection by protecting your eyes against harmful UV rays outside and eliminating the need for sunglasses in most situations.
Indoor Light
The ability of transition lenses to darken when exposed to UV rays and fade back to clear when they are not exposed to UV light is one of the most important aspects of this technology. It also distinguishes it from other lens brands that may say “transition” or even photochromic. The most common way to activate your transition lenses is by going outside on a sunny day, but you can also use a UV flashlight to trigger the molecules in the lenses to change. If you want your lenses to darken faster, you can use a higher-wattage UV flashlight, which will have more of an effect on the molecules in the lens than a lower-wattage version. Several factors can affect how quickly the lenses can activate or darken and fade back to clear, including the lens brand and the temperature of the environment/weather conditions. For example, plastic photochromic lenses react more slowly than glass versions and take longer to fade to a clear shade when exposed to cold weather. While it may be inconvenient for your transition lenses to take a little extra time to adjust from dark to clear, it is beneficial for your eyes as the lenses protect them from harmful UV rays and reduce glare from the sun.
Cold Weather
When cold weather comes around, your lenses will darken faster than in warm temperatures. This is because it’s harder for the photochromic molecules to switch back into their clear state as they cool down. It’s similar to water freezing at a certain temperature; it happens very quickly because the bonds are already formed, but it takes a little longer for the water to melt again as the molecules break those bonds. Having the ability to adjust your glasses automatically to different light conditions is very convenient, especially for those who spend a lot of time outdoors during the day and indoors at night. Transition lenses can be worn anywhere, anytime, protecting eyes from harmful UV rays and filtering out the blue-violet light that damages retinal cells. When choosing a pair of transition lenses, be sure to look for an option with an anti-reflective coating, as this will improve clarity when wearing your lenses in darker environments or at night.
High Temperatures
The molecules that make photochromic lenses darken react to UV rays, but the lens color may not change as quickly when they’re cold. The molecules move more slowly when cold, making them less reactive. When the temperature warms up, the molecules speed up and become more reactive. So, it’s important to keep your glasses in a temperature-controlled environment. Whether sunny or cloudy, Transition lenses adapt to the light around them. They act like sunglasses when you’re outdoors, blocking out UV rays and protecting your eyes from harm. When you come indoors, the lenses fade to clear, so you can see clearly without squinting. The lenses are especially useful for people who spend much time outdoors, such as construction workers and gardeners. Although the technology behind transition lenses is highly advanced, the lenses have limitations. The first limitation is the tint of the lenses, which can be too light or too dark for some people’s preferences. The second limitation is the time it takes for the lenses to fade back from a darkened state to a clear state. The fade time is affected by the temperature, and it can be frustrating if you need to go outside in a hurry and aren’t prepared for it. A new generation of lenses was developed to address these limitations. They are the fastest light-adaptive lenses available today. They get darker and clearer faster than previous transition lenses, and it takes about 30% less time to fade into a clear state when darkened.
