How long do transition eyeglasses take to change?

[Kendrick]

I just wonder how long do transition eyeglasses take to change when they are exposed to UV rays? My transition glasses start to change color 2 minutes after I take them out. Is that normal?

[Moses]

Transitions eyeglasses are made of transition lenses which also called photochromic lenses. They are made with a proprietary and patented photochromic dye system that enables them to activate, or darken, when exposed to the sun's ultraviolet light. And transitions lenses begin to dark when they are exposed to the sun's UV light, reaching 70% tint within 35 seconds. And when UV rays are no longer present, the lenses will begin to fade back immediately, achieving 70% clear in just a few minutes. Good transition eyeglasses can adjust smoothly that wears may not aware it is occurring at the time. So, some people also take transition eyeglasses as one type of uv sunglasses.

[Arjun]

When transition eyeglasses are exposed to UV light directly, they will change the color. A good pair of photochromic lenses usually turn dark in response to UV light within one minute, for 40 seconds. And they continue to darken over the next fifteen minutes. When they are away from UV light, they begin to fade back to clear immediately. The color of the lenses will get lighter within two minutes and mostly clear within five minutes. It is abnormal for your photochromic lenses to start to change color 2 minutes later. You'd better check with your optician.