Photochromatic Lens! Transitions Lens!

Photochromatic lens! I learnt plenty about photochromatic lens in the past couple of days. Aiseh, pho-to-chro-ma-tic means lens that darken when it's in sunlight & vice versa. I've been itching to get a pair of glasses with Transitions lens. And damn, is it complicated for the newbie. Some people think Transitions is a brand / manufacturer of lens, some people think Transitions is a type of lens ie. any lens that are photochromatic. Like what Xerox = photocopy, Thermos = vacuum flasks and NOS = nitrous oxide.

Actually, here's what it's all about:

- photochromatic lens are produced in generally one of 2 methods. Method 1 is to produce lens material (glass or plastic impregnated with an active material) that reacts to sunlight. Method 2 is to put a coating of active material that reacts to sunlight - onto ordinary lens.

- Transitions is a lens coating (method 2).

- Transitions is actually Transitions Optical, a JV between PPG and Essilor. Essilor is a major French lens manufacturer, and I think PPG are the ones who came up with the technology that is Transitions. I can't be bothered to look these up, but I think Transitions is the corporate brand vehicle that franchises the technology to lens mfrs or applies the coating onto someone else's lens. They don't produce any lens themselves, just the coating.

- So, if we combine the previous 2 points, the Transitions lens you've just bought are most probably Essilor lens with a Transitions coating. Apparently, other lens manufacturers like Hoya have now incorporated Transitions coatings into their range.

So, now... what does it mean to you & me?

To begin with, don't ask for Transitions lens. There is no such thing. Ask for Essilor or Hoya etc lens that come with Transitions coatings. Essilor for eg. has several types of lens of varying indexes (the higher the index, the thinner the lens) under different model/range names. Each model/range will have a sub-variant with Transitions coatings. And many of these lens have other coatings besides Transitions, like Crizal for eg, for anti reflection and scratch resistance. Hence the term multi-coated lens.

So, what do you do now? Learn more, that's what. Here's a couple of good sites:

http://www.transitions.com/transitions63/index.asp?id=1
http://www.essilor.com/Products/productsbrands.htm

Or just Google all the damn words you think are relevant. I did.