This entry was published at least two years ago (originally posted on April 13, 2018). Since that time the information may have become outdated or my beliefs may have changed (in general, assume a more open and liberal current viewpoint). A fuller disclaimer is available.
I’ve joked about this for years, and am really excited that it will soon be a real thing: Contact Lenses That Darken in Sunlight Are Going to Give You Some Creepy Alien Eyes.