Can you treat eye and ear infections with oral antibiotics? and how long the treatment should be?

That would depend on the type of infection in either location. Some would respond better to topical medicated drops. Duration of treatment would also depend on the type of infection. You get more specific guidance from this site when you provide more detailed information on the issues involved.

There are instances where eye infections can/should be treated with systemic antibiotics. However in the majority of cases infections in the eye are best treated with drops or injections around or inside the eye. With these local therapies, one is able to achieve higher and more directed doses of medication with fewer side effects than with systemc medications.

In addition to the other answers, i might add that middle ear or ear drum infections are treated with oral antibiotics for a week or so while infections of the ear canal are most often treated with antibacterial, antifungal ear drops usually for a week or so.