First off, the eye textures. I've provided 10 eye textures you can print  off. Print these off on your home printer to about the size you'll  need. Use photo quality paper. Plain paper will bleed though and not  look nearly as good. (More on that later) 

 Ok, other things you are going need.  

Cheap Plastic paint palettes.  You can get these at Wal-Mart, Hobby  -Lobby, but likely, you already have some somewhere. They need to be  clean, at free of scratches as we will use them as molds. 

 Next, you need a two part epoxy. For this, I've been using Smooth-On's Epoxy Cast 690  The stuff isn't very expensive, one trial size pack will do like a  million eyes. lol . It hardens in 24hours, so you have lots of time to  work. When hard, it is as clear as it was when liquid. You can likely  use other epoxies, I think Hobby - Lobby carries a brand, but I've never  used it.  

Take the eye texture prints and cut them out to the round size of the  palette wells. I recommend at first casting a blank well with epoxy  only, and you can use this to cut out the eye textures, just lay it on  the paper and cut around it with an exact-o knife.  

The process is pretty simple. Set your palettes on a level surface. Mix  the epoxy per instructions, and fill each well that you plan to make an  eye in. Fill the well, don't overfill. Now carefully glide the print  face down from the edge of the edge of the palette over the puddle of  epoxy in the well, until you have it completely over the epoxy, centered  on the well. Placing the paper this way as opposed to just dropping it  on the puddle helps make sure you don't get an air bubble caught between  the epoxy and the paper.  

Once you position the paper so that its floating on top of the epoxy, I  cover the back with a few drops. This way  the paper is fully embedded,  and this thing is now completely waterproof. Set this a side for a day  or so to harden.  

Once hard, WHACK the palette to demold them. You may or may not destroy  the palette, guess that depends on your palette, and your whacking. Your  eyes are ready! You can polish them up if you wish, but I find that  they are glossy enough coming out of the clean palette.  

Here is a photo of some finished. 

 Cool thing with this method, you get nice refraction on them at an  angle. You can see this in this next pic. I think it makes them look  more real.