I am not a vet, but it has been my experience that gerbils appear to get conjunctivitis, more commonly known as pink eye. It is characterized by crustiness around the eye and after a while the eye is more shut than open. It is contagious to humans so please wash your hands when handling the gerbil. It is however, easily treatable. You can get antibacterial ointment from the vet, but I have found that an over the counter tube of triple antibiotic ointment has the same active ingredients and works just as well. It may say not for ophthalmic use, but I have used it with only positive results. Take a cotton swab and carefully apply a small amount around the outer part of the eye. Do not place directly on the eye. The gerbil will probably try to wipe it off, but enough of the medicine makes contact to destroy the bacteria that is causing the problem. I would recommend applying this 3 times a day for the first day or two, followed by a daily application for a couple more days. This can vary, depending on the severity of the infection. The gerbil's pink eye should show signs of improvement within 24 hours.
