I just bought an eye pencil sharpener because well, you can't really use a normal sharpener (from what I've sadly learned lol >>) and I've been wondering what the difference was. Apparently there are two holes/parts for sharpening the tip and the part that holds the actual eye colour.
I got the Quo double sharpener and was around $3.50 but I was lucky and realized it was on sale for only $1.99 when I got home to look at my receipt... should have looked at it earlier but meh =p
The sharpener is extremely handy. It comes with a tiny pick inserted inside of the sharpener which you can use to pick out the mess left from the colour and the sharpener opens from the top and bottom. I really love it and glad I got it =]