Being extremely nearsighted I am always looking for ways to see small flies or flush floating terrestrials. Lefty Kreh mentioned the use of a crystal flash post in ADVANCED FLY FISHING TECHNIQUES. The idea of tying a synthetic post under the shank and bringing it up around the shank to minimize bulk came from a tutorial on Charley Cravens web site, Charley's fly box. The crystal flash post catches the light as the fly bobs along so that I get a glimpse of it every couple of seconds even when I can't see the body of the fly on the water.