Which topical agent is used to anesthetize the cornea for blocks during equine ocular examination?

• A. Proparacaine
• B. Tropicamide 1%
• C. Carbocaine
• D. Xylazine

Answer: (A)

Topical corneal anesthesia is achieved with a fast-acting local anesthetic applied directly to the eye. Proparacaine is used in horses because it quickly blocks nerve conduction in the corneal nerves, numbing the cornea within seconds to a minute and providing a short, safe window to perform exams or corneal blocks. This surface anesthesia is ideal for touch and manipulation of the cornea without causing pain.

Tropicamide is a pupil-dilating agent, not an anesthetic, so it doesn’t numb the cornea. Carbocaine is a local anesthetic used for injections around nerves or tissues, not applied topically to the corneal surface for surface anesthesia. Xylazine is a sedative/analgesic given systemically and does not provide topical corneal numbness.