Final answer:
Hyaluronidase is the drug added to local ophthalmic anesthetics to increase diffusion by acting as a spreading factor, enhancing the drug's dispersion.
Step-by-step explanation:
The drug added to a local ophthalmic anesthetic to increase diffusion is hyaluronidase. Hyaluronidase is used as a spreading factor that facilitates the dispersion and absorption of administered drugs by breaking down hyaluronic acid in the body. This action enhances the diffusion of the anesthetic, thereby promoting a more rapid and effective onset of anesthesia. While epinephrine is also used in anesthetic solutions, its primary role is to constrict blood vessels to prolong the duration of the anesthetic and reduce bleeding, not for increasing diffusion. Hyaluronidase is an enzyme that acts as a spreading factor, helping to break down hyaluronic acid and allowing the anesthetic to spread more easily. It is commonly used in ophthalmology to improve the efficacy of local anesthetics during eye surgeries or procedures.