I have this lovely collection of antique brown and blue eye prosthetic eyes. They are so real looking, being handblown in Germany, years ago. Down the the tiny red blood vessels. They're delightful, but take extra care to use. The glass is fragile, and there's two walls of glass. The front wall is fairly thick, but the back wall is thin. What I usually do when I use one, is to back fill the eye, using my E6000 glue and sometimes a custom dapped disc. The glue takes 24 hours to cure, and often I have to use multiple layers of it. I've got a piece of clay that allows the eye to balance level. The end result makes a wonderful piece, and further weaving and placement of botanical pieces, give it a level of protection it wouldn't have otherwise.