Final answer:
Optometrists are authorized to administer epinephrine injections for anaphylactic reactions, but regulations may vary by location.
Step-by-step explanation:
The injection that optometrists are allowed to perform is the intramuscular (IM) or subcutaneous (SC) injection to counteract anaphylactic reactions. This is commonly an epinephrine injection which is administered to provide urgent treatment for a life-threatening allergic reaction. Notably, the laws and regulations concerning optometric procedures, including injections, can vary significantly between different states or countries. Therefore, optometrists must adhere to the specific protocols and scope of practice defined by their local regulatory boards.