Just a clarifying point:

Optometrists are different from Ophthalmologists. Ophthalmologists are medical doctors (i.e. they have an MD), optometrists are not. Optometry also involves post-graduate training, and results in an OD (Doctorate of Optometry).

In the type of store you're talking about, it's much more likely you'll see an optometrist, not an ophthalmologist.