Instillation of a 1.5% (w/v) levofloxacin ophthalmic solution three times a day, which is the dosage or dose regimen of the present invention, has features to cure bacterial conjunctivitis in a shorter time than instillation of a 0.5% (w/v) ophthalmic solution three times a day, which is the conventional dosage or dose regimen, and not to increase the rate of occurrence of side effects. Curing the ocular infection in a short time leads to shortening of the duration of exposure of the ocular-infection-causing bacterium to levofloxacin. Therefore, the levofloxacin ophthalmic solution in the dosage or dose regimen of the present invention is eventually expected to suppress emergence of the resistant bacterium resulting from the long-term use of the levofloxacin ophthalmic solution in the conventional dosage or dose regimen. In addition, it is confirmed that the levofloxacin ophthalmic solution in the dosage or dose regimen of the present invention directly inhibits the ocular-infection-causing bacterium such as Staphylococcus aureus from becoming resistant to levofloxacin, which results from the short-term use of the levofloxacin ophthalmic solution in the conventional dosage or dose regimen.
