04-11-2009, 08:09 AM
I've had them before lasik surgery. Working in a cold building would keep the the lenses dark for a longer period of time after entering. Also, most car windshields have a UV coating that prevents the lenses from getting dark. I would have to take them off and hold them up to the side window to get them to darken. I used to have two pairs of glasses. Regular clear prescription and prescription sunglasses.
Joe
Joe