I dont personally know, I've shadow several optometrist myself, most have lots of debt and are starting a family and I ask them if they are going to buy out someone elses practice in the future, and they told me not in the near future with the debt they have.
One optometrist I've shadow had virtually no debt thanks to his parents, and was working for an OD before, that OD he worked for is retiring and he is in the process of buying it out.
In general, its safe to say that starting out you'll work as an associate or something commercial, and not uncommon if you have to piece together many different part time jobs at different offices in order to have a full income. But after a few years depending on what your aspirations are, as well as what opportunities present itself, you can make your own private practice or buy someone elses. A good portion obtains a full time position as an Associate at their desirable place with a reasonable income.
Again, this is third party information =P.
That being said having debt for a long time isnt necessarily a bad thing. Optometrists (in my views) have very relax schedule compare to say Physicians, spend your time living life and have a happy balance of work and play while paying off your debt.