Tissue banking, retrieval & graft evaluation
The chain from donation to theatre determines the outcome. No endothelial procedure is better than the quality of its graft.
Retrieval, selection & safety
The graft is retrieved from a deceased donor (corneoscleral rim or whole globe), within a short interval after death. Selection rules out infectious contraindications (HIV, hepatitis and syphilis serologies; suspected prion disease/Creutzfeldt-Jakob), certain haematological malignancies, and a history of corneal refractive surgery for grafts intended for anterior-surface endothelial use. In France, the activity is regulated by the Agence de la biomédecine and rests on the principles of non-commercialisation, anonymity and presumed consent.
Storage: hypothermia vs organ culture
| Method | Principle | Usual duration | Distribution |
|---|---|---|---|
| Hypothermia (4 °C) | Optisol-GS-type medium; metabolic slowdown | ~1-2 weeks | Dominant North-American model |
| Organ culture (31-37 °C) | Metabolically active culture, extensive microbiological control, final deturgescence | Up to ~4 weeks | Predominant European / French model |
Evaluation & modern preparation
Evaluation covers the endothelial cell density (specular microscopy; acceptance threshold often ≥ 2000-2200 cells/mm² depending on indication), morphology (polymegathism, pleomorphism), stromal clarity and the absence of epithelial defect or contamination. The 2026 era is that of bank-prepared tissue: precut DSAEK grafts, prestripped or even preloaded DMEK grafts (already loaded in the injector, S-stamped for orientation). These preparations standardise the procedure, reduce the risk of intraoperative loss and shorten operating time.
A DMEK graft has a mandatory polarity: it scrolls spontaneously with the endothelium facing outward. A graft implanted upside-down = guaranteed primary failure. Hence the asymmetric marking (a readable “F/S” = correct orientation) and the orientation-checking manoeuvres before fixation by the gas bubble.
Graft immunology & rejection
Rejection remains — alongside late endothelial failure and recurrence of the original disease — one of the three major causes of failure. Its incidence and severity depend closely on the technique and the host.
The three lines of rejection
| Type | Clinical sign | Prognosis |
|---|---|---|
| Epithelial | Migrating epithelial rejection line | Benign, often reversible |
| Stromal (subepithelial) | Subepithelial infiltrates (Krachmer type) | Intermediate |
| Endothelial | Retrocorneal keratic precipitates, Khodadoust line, sectoral oedema | The most threatening — destroys the endothelial reserve |
Risk hierarchy by technique
A major, often under-appreciated principle: the less endothelium and antigen you graft, the less you reject. The rate of clinically significant rejection follows the gradient DMEK < DSAEK < penetrating keratoplasty; DALK, which preserves the recipient's endothelium, effectively eliminates endothelial rejection (the most serious form). DMEK shows rejection rates of the order of 1-2%, versus several percent for DSAEK and up to 10% or more for PK on a vascularised cornea.
High immunological risk factors
- Corneal neovascularisation (loss of immune privilege) — the dominant factor.
- Repeat grafts, active inflammation, prior rejection episode.
- Young age (vigorous immune response), large graft close to the limbus.
- Synechiae, glaucoma, diseased ocular surface.
The role of HLA matching remains debated: a possible benefit in very-high-risk cases, but heavy logistics and inconsistent data; it is not standard in routine practice. Prevention relies more on prolonged topical corticosteroids, control of inflammation and neovascularisation (anti-VEGF, vessel targeting), and choosing a less immunogenic technique when possible.
Endothelial rejection is a relative emergency: early recognition (redness, visual loss, keratic precipitates) and intensive corticosteroids (hourly topical ± systemic/periocular route) often save the graft. Educating the patient about warning signs is part of the treatment.