Are photochromic lenses suitable for driving?

Photochromic lenses require the presence of UV light to react. Nowadays windscreens block the UV light needed to help the lens react, so normal photochromic lenses remain in their unactivated state inside the car. At night or in poor visibility, you must not wear tinted glasses, lenses or visors or anything that restricts your vision. However, you may wear tinted lenses in good driving conditions.