Whether on the road or in the woods, your eyes need protection from UV rays and debris. A photochromic lens can help you adapt to changing light conditions without changing glasses.
They self-adjust to tint when the sun goes down, making them an excellent choice for long rides through forested areas. They typically take about 30 seconds to go from clear to dark.
Photochromic lenses are perfect for persons who must always wear glasses.
Optical properties
Photochromic lenses darken when exposed to sunlight or UV rays, then transition back to clear when removed from exposure to those rays. This ability to adapt to varying light conditions makes them ideal for cycling, especially mountain biking, where riders frequently go from bright, sunny open fields into darker wooded areas and back again.
The transition happens because the lenses are made from transparent polycarbonate and embedded particles of silver chloride or silver halide. The molecules are invisible and remain so until they come into contact with UV light, at which point a chemical reaction occurs. This darkens the lens, reducing the visible light that passes through it. The lenses will return to their clear state when moved out of direct sunlight or UV light, such as when the rider goes indoors.
One thing to remember with photochromic lenses is that they are slower to change between tints than regular glasses and can take longer when the weather is warm. To speed up the process, some competent cyclists like to put their photochromic lenses in a fridge right before their workout, which will help them turn dark much more quickly.
The best photochromic cycling glasses will also be made from a durable, shatter-resistant material that is lightweight and comfortable to wear. Common choices include plastic, nylon, and titanium. Metal frames are more expensive and heavier but are more rugged and suitable for high-impact sports.
UV protection
Photochromic lenses are an excellent choice for cyclists because they adapt to changing light conditions. They allow the rider to see in shaded areas and switch over to sunglasses when they reach sunnier parts of their route. This is especially important for mountain bikers riding through wooded areas and into brighter sunlight.
The transition of the lenses from clear to tinted is achieved through a chemical reaction within the lens itself. Trillions of silver halide and chloride molecules are embedded in the lens and remain invisible until exposed to UV rays. This causes the molecules to shift, change shape, and absorb light causing the lenses to darken. Once away from the UV rays, the lenses revert to a transparent state.
Several different manufacturers produce cycling glasses with photochromic lenses. Some are big, well-known brands that charge a premium, while others are small direct-to-consumer brands looking to make a name for themselves. It can be challenging to sort through the options and find a pair of photochromic cycling glasses worth your money.
The photochromic lenses are impressive for their price range, changing over quickly and getting as dark as many standalone cycling sunglasses.
Adjustability
A good pair of cycling glasses will protect your eyes from bright sunlight, glare, and airborne debris. These include road spray, dust, bugs, rain, snow, and mud. These glasses will also block out UV rays that can damage your eyes.
Photochromic lenses are great for cyclists as they allow your eyes to adapt quickly to changing light conditions on the bike. This is especially important for mountain biking, where you frequently move in and out of dark wooded areas into lighter open areas. Lenses that don’t respond to these changes quickly can leave you blinded, or you might not be able to see that gnarly root in front of you.
The best photochromic lenses adjust to brightness quickly, a process that can take around 1 minute. This is faster than other cycling sunglasses with regular lenses, which can change slowly and may not fully darken.
These sunglasses are lightweight and have a frame with no gap around the lenses for a full field of vision. They have a polycarbonate mirrored lens with an anti-reflective treatment and are coated to resist scratching. The nose pads and arms are adjustable for a comfortable fit. They don’t mist or fog and have a wide range of ventilation openings to encourage airflow. They are available in various colors and come with a spare transparent lens.
Comfort
Photochromic cycling glasses provide a barrier to sunlight, road spray, bugs, and dust. The best designs also offer technology to improve visual acuity so you can spot things more easily.
Most cycling sunglasses either come with a set of lenses that can be switched out depending on the light conditions, or they have one lens that adapts to changing conditions automatically. The latter category of glasses tends to be preferred by MTB cyclists who often ride in terrain where the brightest and darkest areas alternate within minutes.
