Final answer:
Erythromycin ophthalmic ointment is primarily used to protect newborns against eye infections such as neonatal conjunctivitis, which can lead to serious eye damage and blindness if untreated.
Step-by-step explanation:
Erythromycin ophthalmic ointment is an antibiotic used in the prevention of bacterial infections of the eye, particularly for newborns immediately after birth. Its main purpose is to protect against neonatal conjunctivitis, which is often caused by bacteria like N. gonorrhoeae or C. trachomatis. These bacterial infections can lead to serious conditions such as inflammation of conjunctiva, keratitis, and in severe cases, can cause ulceration or perforation of the cornea and potentially result in vision loss or permanent blindness if left untreated. Therefore, the correct answer to the question is that Erythromycin ophthalmic ointment protects the eyes against (b) Infection.