I just drop some food at the 'entrance' to thier cave. They come out to get it eventually. With time mine have come to expect thier food to be dropped there and will come out to get it almost right away. They dont see very well, but they smell it. They kind of grope around blindly to find it, so they are very shy about coming out to get it until they have established that things will be OK. Here is a 'best that I could do at the time' photo of mine making a rare appearance.
Good Luck,
-Christine