Transition glasses are equipped with transition lenses which are a brand-specific type of photochromic lenses. Transition lenses use photochromic technology to assist user vision through a range of light condition, which will darken when exposed to ultraviolet light.
Transition glasses are produced in a sterile, dust-free manufacturing environment so airborne particles and dust do not lodge in the lens material. A liquid containing millions of photochromic molecules is applied to the front surface of the lenses after they are heated gently so that the lenses become porous. The lens acts like a sponge, absorbing the photochromic material into the top layers. Once the liquid has dried, the lenses are UV sensitive and will change from clear to dark. When exposed to UV light, the molecules become energized and activated and cause the lens to darken. After the lenses are coated with the photochromic liquid, they can scratch very easily in their raw state. So, Transition glasses always receive a scratch resistant coating.
Transition glasses are different from standard lenses as they develop tint when exposed to UV rays. This means users don't need a separate pair of prescription sunglasses, as the transition lenses will form a tint to shield their eyes on sunny days. This can be tiresome, especially if you are going from shop to shop on a hot summer's day and can't see price tags due to the tint on your sunglasses. Switching glasses is not only irritating, but can also increase the chance of a pair being left in a cafe or restaurant. Glasses that can rest on your face for the whole day are much less likely to go astray.
Transitions glasses don't only produce a tint on glorious summer days. UV rays are present even on cloudy days and these rays can damage your eyes if experienced for prolonged periods. Transitions lenses produce a pale tint on overcast days, with the tint becoming darker as higher levels of sunlight occur. When indoors, Transitions lenses become clear again, meaning you can watch TV or read a book without the tint disturbing your vision.
Transition glasses were formulated to take the hassle out of changing glasses for outdoor and indoor tasks. Transition lenses may not react, however, when driving a car. This is due to the fact that most windscreens come fitted with some UV protection in the glass. If the windscreen inhibits UV levels sufficiently, there may not be enough UV to activate the tint in the glasses. Many people who use Transitions lenses keep a cheap pair of sunglasses in the car due to this lack of reaction.