Which instrument would be used during a keratoplasty to remove the cornea?

The trephine is the correct instrument for removing the cornea during a keratoplasty, which is a surgical procedure to replace a diseased or damaged cornea. The trephine is a circular cutting instrument that allows for the precise excision of a circular section of tissue, which is essential in corneal transplantation. Its design enables the surgeon to create a clean, uniform cut, which is critical for ensuring proper alignment and adherence of the donor cornea when it is sutured into place.

In contrast, the other instruments listed have different functions. The Westcott scissor is utilized for dissection during procedures but is not specifically designed for excising the cornea. The oculotome is designed for a more specific purpose, often involving the cutting of the sclera or other eye tissues, but not for removing the entire corneal area. The phacoemulsifier is a device used primarily in cataract surgery to break up and remove the lens of the eye, thus it does not have a role in corneal removal. Each of these instruments serves a unique purpose in ocular surgery, but for keratoplasty, the trephine is the appropriate choice.