They typically take around 30 seconds to fully darken and between two to five minutes to return to a clear state. Photochromic lenses were created in the s at the Corning Glass Works Inc. They will return to an almost clear state within two minutes and be fully clear within five minutes, however, excessively high or low temperatures can affect this timeframe. Photochromic lenses are an extremely convenient, cost effective and beneficial purchase for a number of reasons, although, there are some weaknesses.
There are pros and cons of photochromic lenses and sunglasses, including those listed below:. Reaction Times — Although photo lenses reaction from clear to sunglasses is quite quick, typically within 30 — 60 secs, the reversal takes a little longer as much as 5 minutes depending upon the temperature of the lens which could be dangerous if entering a dark room or certainly inconvenient at best.
Photochromic Lens Temperature Dependency:. Cold weather also increases the time taken to return to a clear shade.
Plastic photochromic lens molecules of silver and halide are usually layered or embedded evenly onto the surface of the lens providing an even shade of tint when darkening.
Glass photochromic lenses have the molecules contained within the glass and this can sometimes cause an uneven tinting effect on a lens with higher prescription due to the different thickness of the lens from one edge to the other. Can I use Photochromic sunglasses for driving? Even though both plastic and glass photochromic lenses will tint and retain the original color on exposure on exposure to the UV radiation, the chemistry behind every process is clearly different.
Now that you have learnt how photochromic lenses work, it will be important to know the exact reasons for investing in this accessory.
This lens will automatically adjust depending on the intensity of the surrounding ultraviolet radiation. How photochromic lenses change from clear to dark. In fact, it is for this reason that most people opt for photochromic lenses and not polarized lenses.
Photochromic lens provides an ultimate protection against the harmful ultraviolet radiations such as the blue violet light. Normally, the effectiveness of these lenses will depend on the quality of photochromic molecules on the material.
The truth is that you will only have a pair of sunglass or lens for both indoor and outdoor activities. This will reduce chances of suffering from eye problems due UV radiation , such as blindness or cataracts. Notably, to improve performance of your lenses, you can use photochromic alongside other lens coating technologies. That is, you can have hydrophilic anti-fog, anti-abrasion, UV resistant of augmented reality technologies , just to mention a few. But again, even though there have been significant improvements in the photochromic technology, you still have to deal with certain challenges.
It will mainly depend on the surrounding temperature, which tends to affect the reaction time of lenses. At times, photochromic lenses may not be dark enough to protect your eyes from extreme light conditions. This may require that you have an additional protective coating to block the extra ultraviolet radiation. If you often experience changing light conditions, such as going from inside to outdoors or vice versa, photochromic lenses could be a helpful lens solution for added convenience.
Sometimes known as light adaptive lenses, photochromic lenses will automatically adapt to the changing light conditions around you. This works when the lenses are exposed to UV light and the molecules embedded in the lens change their structure.
This change of structure darkens the lenses automatically to provide a comfortable tint, for optimal vision. Your optician will be able to discuss and talk you through this. The molecules in the lenses are not visible to the wearer or others and when the UV exposure decreases, the lenses will return to a clear state.
The most popular brand of photochromic lenses is Transitions 1. They are light intelligent lenses designed to protect your vision from harmful UV light and combat glare, resulting in comfortable vision.
Photochromic lenses will work even on a cloudy day because UV rays are able to penetrate the clouds, so your eyes are still protected. Some more advanced technologies, such as Transitions XTRActive, will work even behind a car windscreen by adapting off of visible light too. When your photochromic lenses start to take longer and longer to transition from indoor to outdoor light, that's a sure sign it is time to get new transition lenses.
Ask your eye doctor if photochromic lenses are right for you or add them to your glasses order online. Home Sunglasses Sunglasses Types. By Adam Debrowski. Schedule an exam Find Eye Doctor.
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