How long does it take for bacterial keratitis to heal with eye drops?

This depends on the severity of infection. Often, bacterial keratitis presents with pain, sensitivity to light, redness and blurring. Treatment with frequent antibiotic drops needs to be started immediately. If the selected treatment is effective, the first thing to improve is the pain and this should improve within the first 24 to 48 hours. However, if there is blurring, that could continue to worsen because even though infection is coming under control the associated corneal swelling that may cause blurring can still get worse before it gets better. After that the inflamed cells from the infection and the surrounding corneal swelling will gradually improve. Finally, as these improve there may be a resulting scar that, depending on location and severity of initial infection, may cause persistent visual loss. The scar may gradually improve and become somewhat more transparent over time and this phase may take many months. So, the infection should be brought under control within 24 to 48 hours; the swelling phase that also involves the surface epithelium may take several days to heal, and in a very severe infection even weeks. Finally the evolution of the scar can take months. However this is all very variable — a small peripheral ulcer may be a very minor and quick problem while a large, aggressive more central ulcer can be very severe resulting in long term damage to vision, which may require a corneal transplant.