KERATOPLASTY

Keratoplasty, also called corneal grafting or corneal transplantation, is an operation in which the patient's diseased cornea is replaced by the donor's healthy
clear cornea.

Types
1. Penetrating keratoplasty (full-thickness grafting)
2. Lamellar keratoplasty (partial-thickness grafting).

Indications
1. Optical, i.e., to improve vision. Important indications are: corneal opacity, bullous keratopathy, corneal dystrophies, advanced keratoconus.
2. Therapeutic, i.e., to replace inflamed cornea not responding to conventional therapy.
3. Tectonic graft, i.e., to restore integrity of eyeball e.g. after corneal perforation and in marked corneal thinning.

4. Cosmetic, i.e., to improve the appearance of the eye.

 

  Donor tissue
The donor eye should be removed as early as possible (within 6 hours of death). It should be stored under sterile conditions. Evaluation of donor cornea. Biomicroscopic examination of the whole globe, before processing the tissue for media stroage, is very important. The donor corneal tissue is graded into excellent, very good, good, fair, and poor depending upon the condition of corneal epithelium, stroma, Descemet's membrane and endothelium (Table 1).

Methods of corneal preservation
1. Short-term storage (up to 48 hours). The whole globe is preserved at 4oC in a moist chamber.
2. Intermediate storage (up to 2 weeks) of donor cornea can be done in McCarey-Kaufman (MK) medium and various chondroitin sulfate enriched
media such as optisol medium.
3. Long-term storage up to 35 days is done by organ culture method.

Surgical technique
1. Excision of donor corneal button (Fig. 1A). The donor corneal button should be cut 0.25 mm larger than the recipient, taking care not to damage
the endothelium.
2. Excision of recipient corneal button. With the help of a corneal trephine (7.5 mm to 8 mm in size) a partial thickness incision is made in the host
cornea (Fig. 1B). Then, anterior chamber is entered with the help of a razor blade knife and excision is completed using corneo-scleral scissors
(Fig. 1C).
3. Suturing of corneal graft into the host bed (Fig. 1D) is done with either continuous (Fig. 1E) or interrupted (Fig. 1F) 10-0 nylon sutures.

Fig. 1. Technique of keratoplasty : A, excision of donor corneal button; B & C, excision of recipient corneal button;
D, suturing of donor button into recipient's bed; E, showing pattern of continuous sutures in keratoplasty; F, Clinical
photograph of a patient with interrupted sutures in keratoplasty.

Complications
1. Early complications. These include flat anterior chamber, iris prolapse, infection, secondary glaucoma, epithelial defects and primary graft failure.

2. Late complications. These include graft rejection,
recurrence of disease and astigmatism.