A corneal button is a replacement cornea to be transplanted in the place of a damaged, diseased or opacified cornea, normally approximately 8.5–9.0 mm in diameter. It is used in a corneal transplantation procedure (also corneal grafting) whereby the whole, or part, of a cornea is replaced. The donor tissue can now be held for days to even weeks of the donor's death and is normally a small, rounded shape. The main use of the corneal button is during procedures where the entirety of the cornea needs to be replaced, also known as penetrating keratoplasty.

Greek physician Galen is said to have first consider the possibility of corneal transplantation however, there is no evidence that he actually attempted the procedure. It was only until the 18th century that early surgical proposals for keratoplasty would arise and the 19th century for experimentation in the field to begin.

In 1813, Karl Himley suggested that opaque animal corneas can be replaced by transplanting corneas from other animals; with his student Franz Reisenger commencing experimentation in 1818.

In 1844, Edward Kissam undertook the first ever recorded attempt of a xenograft on a human; the donor was a pig and was ultimately unsuccessful. Henry Power made a suggestion in 1867 that using human tissue rather than animal tissue for transplantation would be more effective however, it would not be until 1905 for the first successful human corneal transplant by MD, Eduard Zirm.

Since 1905, various techniques and procedures have been developed to increase the effect of the transplantation and success rate. Traditionally, the most common procedure for corneal transplantation was penetrating keratoplasty whereby an entire corneal button is replaced. Recently however, procedures such as anterior and posterior lamellar techniques where only diseased or damaged layers of the cornea are selectively replaced have become increasingly popular.

After the death of the donor, the cornea must be retrieved within a few hours and will be screened for diseases and assessed for its viability to be used for a corneal transplantation by assessing its health. If passed, the cornea will be stored in a nutrient solution at an eye bank until needed for an operation. In most cases, the corneal button is removed from the donor cornea prior to storage as this extends its possible storage time.

For the operation procedure, the patient is anaesthetised and the damaged or diseased corneal button will be removed using a bladed instrument called a trephine (approximately 8.0–8.5 mm in diameter). A corneal button of matching size is then put in place of the removed tissue and stitched in place. Usually, twelve clock-hour nylon stitches are used with a continuous band nylon stitch.

The procedure takes approximately 60–90 minutes however, a few months will be required for vision to return to what it was like preceding the operation; and continue to improve from then on. Approximately 12–18 months after the operation, all stitches will be removed. During this time, anti-rejection drops will be needed to minimise inflammation; the dosage of which is carefully monitored by a corneal surgeon.