History of corneal transplants
Corneal transplants are now over a century old and represent the first transplants performed on humans, across all organs. The first technique, called penetrating keratoplasty, involved replacing the entire thickness of the cornea using a cornea from a deceased donor. While this technique is still used for certain indications today, newer procedures have been developed that replace only a single layer of the cornea, thus allowing for a faster postoperative recovery. These are lamellar grafts, the thinnest of which are 0.02 mm.
The first corneal transplants
The terms keratoplasty and corneal transplantation were mentioned as early as the beginning of the 19th century by physicians such as Franz Reisinger and Wilhelmus Thome, although no procedure was ever performed on a human being. In fact, the first corneal transplant was carried out not on a human, but between two gazelles by James Bigger in 1837 in the Sahara, in order to negotiate his release from Bedouins who had captured him. Subsequent attempts in humans involved xenografts (that is, corneas from animals), but all of these resulted in failure.
Zirm and the first corneal transplant in humans
The first corneal allograft in a human was performed in 1905 near Prague by Dr. Eduard Konrad Zirm, an Austrian ophthalmologist. Alois Golgar, the first patient to receive an allograft (a cornea from another human), suffered bilateral corneal blindness following an eye injury caused by lime splash. Karl Brauer, an 11-year-old boy, was the donor. He had lost the use of one eye after a penetrating injury from a metallic foreign body. Zirm enucleated the boy's eye, whose cornea had remained transparent, and cut the recipient's cornea twice to obtain two circular grafts, each 5 mm in diameter. The corneal transplant on the right side failed and had to be removed; however, the graft on the left side became transparent, and after fifteen weeks of hospitalization, Alois Golgar was able to return home.
Popularization of penetrating corneal transplants
Subsequently, penetrating corneal transplants (or keratoplasties) became popular, but with a high failure rate due to the lack of topical corticosteroids, antibiotics, operating microscopes, and nylon sutures. There were significant disparities in success rates depending on the initial indication for the transplant. For example, while the success rate for keratoconus was 65%, it was 0% for transplants performed on patients with Fuchs' endothelial dystrophy. This figure can be explained by the small diameter of the transplants at the time (around 4–5 mm) as well as by the surgical procedure itself, which was certainly more traumatic than today, resulting in a greater loss of endothelial cells in the graft, the number of which was already reduced by its small size. The lack of a standardized protocol for preserving grafts and of a cornea bank at that time also contributed to this failure.
Improvement of penetrating keratoplasties
The creation of an American eye bank in 1961, the increased attention paid to the endothelium, and subsequent improvements in surgical techniques have contributed to increased graft survival rates. Indeed, 100 years after the first corneal transplant in humans, the success rate of penetrating keratoplasty has risen to 90% for keratoconus , as well as for decompensated pseudophakic corneas and Fuchs' dystrophy. However, this success remains limited by the significant rejection rate and substantial postoperative astigmatism, which has led to the development of posterior lamellar grafts to further improve postoperative outcomes.
The first posterior endothelial grafts
Posterior endothelial keratoplasty encompasses various surgical techniques that involve replacing only the posterior (or inner) portion of the cornea when it is diseased. Given their effectiveness and the significant reduction in complications with these techniques, they have gradually become the most frequently performed transplants when indicated. The first posterior lamellar keratoplasty was performed in 1955 by C. Tillett on a 68-year-old patient with advanced Fuchs' endothelial dystrophy. In 1998, Melles et al. described their first cases of posterior lamellar keratoplasty, which closely resembled the technique developed by Tillett. In 2004, the same team modified the technique for preparing the recipient cornea by performing the first descemetorhexis, that is, peeling the endothelial Descemet membrane without damaging the posterior stroma. This procedure then took the name "Descemet stripping endothelial keratoplasty" DSEK and was improved two years later by Gorovoy who used a microkeratome instead of manual dissection to prepare the graft and thus allow more reproducible results (DSAEK for "Descemet stripping automated endothelial keratoplasty").
The DMEK, the culmination of a century of progress
Following the popularization of DSAEK, Melles and his team developed a new endothelial keratoplasty procedure on human cadavers called DMEK, for "Descemet Membrane Endothelial Keratoplasty." This is the latest technique developed and has superseded others today. In this technique, the donor endothelium is directly peeled using forceps without the need for dissection with a microkeratome or knife. Studies now suggest the superiority of DMEK in terms of final visual acuity and faster postoperative recovery compared to other techniques. Faced with graft shortages in some parts of the world, hemi-DMEK and quarter-DMEK have been developed to allow a single graft to be shared among several patients. These techniques are not currently used in France; each patient receives a whole graft for their eye.