Q4 LONG ANSWER 10M ★ High-yield

Describe keratoplasty with its types, indications, donor criteria and complications.

Ophthalmology · 3rd Professional

Types and Indications

Keratoplasty (corneal grafting) is the replacement of diseased corneal tissue by healthy donor cornea.
It is the oldest and the most successful of all solid tissue transplants, because the cornea is avascular and has NO lymphatics, giving it a degree of immune privilege.

Classification	Types
By indication	Optical — to restore vision, the commonest; therapeutic — to remove infected tissue in an unresponsive ulcer; tectonic — to restore structural integrity in thinning or perforation; and cosmetic — to improve the appearance of a disfigured blind eye
Penetrating keratoplasty (PK)	Full-thickness replacement. The traditional operation; still needed for full-thickness scarring and for large perforations. Disadvantages: an open-sky procedure with the risk of expulsive haemorrhage, high astigmatism, prolonged rehabilitation, a permanently weak wound, and rejection of all three layers
Deep anterior lamellar keratoplasty (DALK)	The stroma is replaced and the patient’s own descemet and endothelium retained. For keratoconus, stromal dystrophies and anterior scars with a healthy endothelium. Since no donor endothelium is transplanted, there is NO endothelial rejection and the graft survives far longer — the great advantage. The big-bubble technique bares Descemet
DSAEK / DSEK	Descemet stripping (automated) endothelial keratoplasty — a thin disc of donor posterior stroma, Descemet and endothelium is inserted through a small incision and held by an air bubble. For endothelial disease: FUCHS dystrophy and pseudophakic bullous keratopathy. Rapid visual recovery, minimal astigmatism, a closed eye and low rejection
DMEK	Descemet membrane endothelial keratoplasty — Descemet and endothelium alone, with no stroma. The best visual results and the lowest rejection rate of all, but technically demanding
Keratoprosthesis	An artificial cornea (Boston KPro, osteo-odonto-keratoprosthesis) for eyes in which repeated grafts have failed, or in severe dry eye and cicatrising disease

The Donor Cornea and Eye Banking

Corneas are retrieved within 6 hours of death (longer if the body is refrigerated), by whole-globe enucleation or by in-situ corneoscleral excision, which is preferred as it leaves the globe intact for the family
Storage — McCAREY-kaufman medium at 4°C for up to 4 days; optisol-GS for up to 14 days, which is the standard; and organ culture at 34°C for up to 4 weeks
Assessment of the donor tissue — slit-lamp examination and specular microscopy for the endothelial cell count, which should exceed 2,000 to 2,400 cells per square millimetre; the endothelium is what determines graft survival

Graft Rejection and Complications

Graft rejection is an immune response to donor antigen, and is the commonest cause of late graft failure. It is reversible if treated promptly, which is why the patient must know the warning symptoms
Warning symptoms — "RSVP": redness, sensitivity to light, vision reduced, pain. Every graft recipient should be told to attend immediately if any of these occur
Signs by layer — epithelial rejection line, an elevated irregular line advancing across the graft; subepithelial infiltrates (krachmer spots), resembling those of adenoviral keratitis; stromal haze and oedema; and endothelial rejection — the khodadoust line, a line of keratic precipitates advancing across the endothelium, which is the most serious form since endothelial loss is irreversible

Factors Determining Graft Success

Favourable	Unfavourable
Avascular host cornea	Vascularisation, especially in more than two quadrants — the single most important adverse factor
Quiet, non-inflamed eye at surgery	Active inflammation or infection at the time of surgery
Keratoconus or a stromal dystrophy as the indication	Chemical burn, cicatricial disease, and severe dry eye
First graft	Repeat graft; each successive graft does worse
Small, central graft	Large or eccentric graft approaching the limbus.
Normal intraocular pressure	Glaucoma, which damages the donor endothelium
Older adult	Child — a more vigorous immune response and greater amblyopia risk
Intact ocular surface and normal lids	Lid abnormality, trichiasis, limbal stem cell deficiency
Good donor endothelial count, short death-to-preservation time	Poor donor tissue — primary graft failure
Compliant patient attending for review	Poor follow-up — rejection detected late is irreversible

Applied Aspects

Teach every graft patient "RSVP"; rejection is reversible if it is treated within days and irreversible if it is not, and the patient is the one who detects it
Choose a lamellar procedure where the disease is lamellar; DALK for keratoconus and DMEK for Fuchs give better vision and far less rejection than penetrating keratoplasty
Reduce vascularisation and inflammation before grafting; operating on a vascularised, inflamed cornea is the commonest reason a graft fails

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