Corneal transplantation

Traditional full-thickness corneal transplantation, known as penetrating keratoplasty (PK), was first performed over a century ago and remains the gold standard of corneal transplantation. Penetrating keratoplasty involves replacement of all layers of the central 7–9 mm of the host cornea with allograft tissue, usually derived from eye banks. Donor corneas are harvested from 1–2 weeks prior to transplantation. Tissue or blood typing is not routinely done. The overall optical clarity, integrity of donor tissue, and donor endothelial cell density are evaluated at the eye bank. The tissue is screened for multiple infectious diseases of the donor, a procedure commonly performed for other human allograft tissues. Penetrating keratoplasty Penetrating keratoplasty usually begins with the removal of the diseased central host cornea by use of various forms of trephine. Next, the donor tissue is trephinated from the donor corneal tissue and is usually slightly oversized. The donor tissue is secured in the recipient bed using either interrupted or continuous nylon sutures. When necessary, a cataract extraction may be performed in combination with intraocular lens implantation. Monitored anesthesia care in these cases usually includes brief, intravenous sedation combined with a retrobulbar block. General anesthesia may be required for selected patients unable to be cooperative, such as children or anxious adult patients. Total surgical time is around 30–45 minutes for an experienced surgeon. Corneal graft survival at 1 year is 90% for PK. Indications for PK include haze, ectatic disease, opacities in the cornea, and corneal edema causing decreased vision or pain. In addition, infections, scars, trauma, congenital dystrophies, and corneal decompensation or injury from prior intraocular surgery are also indications.