In June of 2005 I got new glasses. I opted to get "transition lenses" that changed from clear into sunglasses when exposed to the UV rays of sunlight.
This was a mistake! It turns out "transition lenses" only work for a year or two before they stop changing readily. Having glasses that stopped becoming fully clear was a great bother. Since my prescription is fairly mild, I stopped wearing them most of the time when indoors.
This week I finally got around to taking the glasses to the optometrist to see what could be done. For no charge he "retempered the glass", whatever that means, which supposedly fixes them for a month or two.
So far they are working again. Hooray! In June my insurance will allow me to get new glasses once again, and I'll get a new pair without "transition lenses".