Light sensitive lenses, widely known as Transitions, may be a good option for a great deal of people. They are lenses that, when exposed to UV light will darken. The more intense the UV outside, the darker the lenses become.
The technology behind photochromatic lenses
The technology behind this transition of colour is in the molecular structure of the lenses. Tiny molecules of silver halide and chloride are embedded within a photochromatic lens. They are invisible and clear until exposed to UV rays. The molecules react to the UV, causing them to move, change shape and absorb the light. This process changes the molecules so that they darken to a sunglass tint. Temperature may have an effect on the reaction time of the molecules. In the cold weather the molecules move more slowly in changing from dark to light than they would in a warm climate. When the lenses become warm, the molecules speed up and become more reactive, which allows the lens to fade back faster.
New technology over the years has improved both the speed at which the lenses turn dark, the time it takes to lighten up, and the intensity of the darkness. The lenses remain virtually clear when indoors.
There are now options for other than the standard transition lenses. For those who are very light sensitive or would like a lens that will provide bright light protection in the car, there is the Transition Xtractive new generation lens. It has an approximate 5% tint at all
times when not activated. When in the sunlight it does go slightly darker than the standard transition lens and it does change colour in the car.
For people who are frequently exposed to bright light and reflective glare, there is now an Xtractive Polarized lens. These lenses become extra dark and polarized at the same time when they activate outdoors, and like the Xtractive lens, they will darken behind the windshield of a car. However they do not polarize in the car because the polarization does require the UV which is absorbed in the windshield.
Pros and cons of photochromatic lenses
There are definitely Pros and Cons for purchasing transition lenses. Let’s start with the Cons.
CONS
1) Lenses do not turn dark in the car unless you go with an Xtractive lens that will always have a slightly visible tint even indoors.
2) Lenses can take a few minutes to go clear once coming indoors, although with recent advancement in transition technology the lenses do darken quicker and lighten up in less time.
3) On a hazy day outside transition lenses will still darken slightly since there is still UV rays present.
4) If you are sitting by a window indoors with bright sun shining through, some UV will escape the glass and provide a slight colour to the lenses.
And now the Pro’s
PROS
1) There is the convenience of buying a single pair of dual purpose photochromatic glasses that provide corrected vision both indoors when clear and outside providing sunglass protection.
2) It is also cost effective as some might choose this option over 2 separate pairs of glasses.
3) Lenses provide 100% UV protection, which in turn lowers the risk of eye related diseases and illnesses.
4) Transition lenses filter out harmful blue light both indoors and outdoors, so no need to add an additional blue light filter for those on digital devices frequently.
In summation, photochromatic, or transition lenses are a good option for consideration on purchasing a new pair of glasses.
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