I just got bifocals with the "hidden" line and am still getting used to them. I'm nearsighted, but have aged enough to have some problems seeing very close up. I go from using the bifocal lens for reading to taking my glasses off to see very close up. My distance vision without glasses is very poor - which in itself is a survival risk if something really bad happens. Without glasses it would be very easy for me to trip & fall while walking, plus I wouldn't be able to see planes and other small objects at a distance.

I've tried with the small glass signal mirror sold at countycomm.com, the Starflash mirror, and the AMK Rescue Flash mirror used in Doug's kits.