The ratio for rural is 1 OD per 6000 (Not including the MD's).
The ratio for urban is 1 OD per 11000 ("")
Hint: Contact Yellowbook or a phone company that had dual phonebook and internet advertising. They can tell you how many people in a given geographic region google the term "optometrist" or "optical" or whatever you like.
Knowing that information would've been a big PLUS in the business plan that I had to submit to Bank of America. I went off of the standard 1:6000 ratio and that was fine.
I found out how many people are searching for "optometrist" per month in my area and WOW, this area can fit one more OD besides me!