Introduction of Photochromic/ Changeable/ Transition Lenses
The word “photochromic” derives from the two Greek words “photos” and “chroma” which mean
Photo = Light
Chroma = Colour
So it simply means something that changes colour in response to the light. Photochromic lenses change its darken and lighten shades depends upon the exposure to UV light.
Since 1960s photochromic lenses are available, traditionally these type of lenses were made from Glasses but in this modern time Photochromic lenses which is also known as changeable lenses, Day and Night lenses or transition lenses are now available on plastic and polycarbonate material and now also they contain organic (carbon-based) molecules that react to light in a slightly different way. Now many of premium ophthalmic lens manufacturer produce customized photochromic lenses also which mean they can offer different categories of sun protection to meet specific needs of customers.
How do photochromic lenses work?
Reaction Time (Darkening & Lightening timings)
Typically, photochromic lenses darken substantially in response to UV light in less than one minute, and continue to darken a little more over the next fifteen minutes.(1) The lenses begin to clear in the absence of UV light, and will be noticeably lighter within two minutes, mostly clear within five minutes, and fully back to their non-exposed state in about fifteen minutes. It may also depends upon other variables such as temperature, thickness, exposure.
- It help your eyes to cope up as they react to different light conditions during the day
- Good Photochromic lenses blocks 100% of most harmful radiation
- Protects you from UV which can cause lost of harm to eyes. (UV Rays)
- Gives a visual comfort whether indoor or out door
Photochromic lenses disadvantages
- These lenses do not adjust immediately.
- It could take up to two minutes for the lenses to adequately change from light to dark or vice versa
- Another disadvantage for some users is that they will not darken when worn inside vehicles because wind screen green glass absorbs virtually 100% of UV light, so without UV light these lenses won’t darken.
- It gradually loses its darkening ability with time.
What are transition lenses?
In United States photochromic lenses are made by Transitions Optical and many people including some eye care practitioners mistakenly call all photochromic lenses as based on their product name “transitions lenses” or “transition lenses.” But there are many brands of photochromic lenses offered by different lens manufacturers in market.
Available Photochromic lenses from various brands in Nepal
Photo chromic are available in single vision, bifocal and progressive lenses forms in Nepal. There are many best photochromic lenses available nowadays.
Popular brands of photochromic lenses sold in the Nepal are as follows.
- Crizal UV Transition Classic Thin & Light
- Eyezen+ Crizal Transitions Signature
- ZEISS PhotoFusion
- ESPACE Plus transition
- Varilux Progress transition
- SOLIO Photochromic lens
- Hoya Sensity Photochromic Lenses
Price of Photochromic Transition Lenses in Nepal
1. Photochromic lens. (2020). Retrieved 4 September 2020, from https://en.wikipedia.org/wiki/Photochromic_lens