Pear Tree Leaf Problem
 

I have a pear tree in my garden which has lots of pears on it but the leaves appears to have some kind of disease. It looks like lots of raised black/brown dots under the surface of the leaf. (i have tried to upload a photo but couldn't)

I am trying to find out what this disease is and how I can best treat it. Also, can I still eat the pears?

Thanks,

Jim