It is the UV light casues transition lenses to change color.

The silver nitrate changes to silver when the UV lights hit.  This reaction is reversible and the lenses become clear without UV lights.  If you drive with car window closed, the UV lights is blocked by glass therefore transition lense remain clear. If you open the car window, it will change color.

I have been using transition lesens for more than 10 years/5 pair of glasses with no problems. However, I still have a pair of prescription sun glasses in my car for driving becasue I don't drive with car window open. 

It costs more to have transition lense. If you don't want that, you have 2 options:

1. get a clip-on for your glasses. It only costs $20 in costo.

2. get a frame set that comes with the sun glasses that use magnetic clip-on. I have that too.  It looks better and works better. The frame itself costs $200 and you have carry the case with you when you go out.  

所有跟帖： 

• I C， thanks， I think i will get one pair of TL plus a clip-on s -梦中夕阳- ♀ (0 bytes) () 08/19/2015 postreply 20:35:39