The Importance Of Corneal Transplantation

Corneal transplantation is the oldest, most common and most successful transplantation in humans overall. Corneal transplantation refers to surgical replacement of a full-thickness or lamellar portion of the host cornea with that of a donor eye.

General indications of keratoplasty include: optical keratoplasty done to improve vision as in keratoconus, tectonic keratoplasty done to restore or preserve corneal integrity as in descemetocele, therapeutic keratoplasty to remove infected corneal tissue in cases unresponsive to antimicrobial therapy and cosmetic keratoplasty to improve the appearance of the eye which is a rare indication (Seitz et al., 2005).

DONOR TISSUE PREPARATION

Donor tissue should be removed within 12-24 hours of death. The

Most hematological malignancies, diseases of the central nervous system such as Creutzfeldt-Jakob disease, Alzheimer's disease, dementia, multiple sclerosis and motor neuron disease are contraindications to ocular tissue donation as well. Other contraindications include recipients of transplanted organs, prior ocular surgery and ocular diseases that are likely to compromise the graft outcome as inflammation and malignancy.

Eye Bank Association of America. Medical Standards. http://www.restoresight.org.

The donor tissue is inspected by slit-lamp biomicroscopy and the endothelial cell count is determined by specular microscopy. A cornea suitable for transplantation should display a noninterrupted epithelial layer, a stroma free of opacities or folds and a viable and regular endothelium with a cell density above 2000-2200 cells/mm2 (Wiffen et al., 1995).

Wiffen SJ, Nelson LR, Ali AF, Bourne WM. Morphologic assessment of corneal endothelium by specular microscopy in evaluation of donor corneas for transplantation. Cornea. 1995; 14(6): 554-561.

O’Day DM. Donor selection. In: Brightbill FS, ed. Corneal surgery, theory, technique and tissue, St Louis: Mosby-Year Book; 1993: 549-562.

Indications for Penetrating and Lamellar Keratoplasty by

Impact of graft diameter on corneal power and the regularity of post-keratoplasty astigmatism before and after suture removal. Ophthalmology. 2003; 110: 2162-2167.

PROCEDURE

Excision of donor cornea should always precede that of host cornea. Donor tissue is prepared by trephining a previously excised corneoscleral button. The donor button is usually trephined to be about 0.25 mm larger in diameter than the planned diameter of the host opening to facilitate watertight closure, minimize postoperative flattening and reduce the possibility of postoperative glaucoma. A mechanically-guided trephination is standard although newer non-mechanical laser techniques are more accurate and are preferred by some surgeons when available (Gaster et al., 2012).

Gaster RN, Dumitrascu O, Rabinowitz YS. Penetrating keratoplasty using femtosecond laser-enabled keratoplasty with zig-zag incisions versus a mechanical trephine in patients with keratoconus. Br J Ophthalmol. 2012; 96: