From the medicare website I downloaded some data (well, over 2 million records) from the Official Physician Compare Data. After filtering and just keeping the ophthalmologists and optometrists as primary specialty (now down to over 80.000 records) I wanted to see how they are distributed in the U.S. Fortunatly the dataset comes with the zipcode so I plotted how many of them are per zipcode. You can click on any of the three images for a larger view. 

 

 

As expected they follow a population pattern. You can find the code to reproduce the maps here.