For which ophthalmic procedure is a trephine needed?

A trephine is specifically used in full-thickness keratoplasty, which is a surgical procedure to replace the entire thickness of the cornea. This intricate procedure requires precise cutting of the corneal tissue to ensure that the donor material fits seamlessly into the recipient's eye. The trephine operates as a circular cutting instrument that allows for consistent and controlled removal of the corneal tissue.

In contrast, corneal scraping is typically performed using a scalpel or other specific surgical instruments designed for superficial or partial corneal procedures, not involving the depth and precision needed for full-thickness keratoplasty. Eyelid repair and intraocular lens implantation are unrelated to corneal replacement and involve different surgical techniques and tools. Therefore, the utility of the trephine is distinctly aligned with the requirements of performing a full-thickness keratoplasty.