Keratoplasty

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1. KERATOPLASTY - Dr. Narang

2. Keratoplasty / corneal grafting / corneal transplantation Definition: It 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) - anterior or posterior lamellar

3. Indications: Optical , i.e. , to improve vision - corneal opacity, bullous keratopathy , corneal dystrophies, advanced keratoconus . Therapeutic , i.e., to replace inflamed cornea not responding to conventional therapy Tectonic graft , i.e., to restore integrity of eyeball in eyes with severe structural changes such as severe thinning with descemetocele . Cosmetic , i.e., to improve the appearance of the eye.

4. Donor tissue : removed as early as possible ( 12–24 hours of death ). Corneas from infants (3 years and under) are rarely used - surgical, refractive and rejection problems. It should be stored under sterile conditions . Evaluation – medical history review and donor blood screening to exclude contraindications, and microscopic examination of the cornea including endothelial cell count determination

5. Methods of corneal preservation Short-term storage (up to 2 days) - The whole globe is preserved at 4 C in a moist chamber. Intermediate storage (up to 2 weeks) - McCarey -Kaufman (MK) medium and various chondroitin sulfate enriched media such as optisol medium used. Long-term storage ( up to 35 days) -It is done by organ culture method.

6. Contraindications to ocular tissue donation Death of unknown cause . Certain systemic infections such as HIV, viral hepatitis, syphilis, congenital rubella, tuberculosis, septicaemia and active malaria. Prior high-risk behavior for HIV and hepatitis. infectious diseases of the CNS. Receipt of a transplanted organ. Most hematological malignancies. Ocular disease such as inflammation and malignancies ( e.g. retinoblastoma) and corneal refractive surgery.

7. H ost factors may adversely affect the prognosis: Severe stromal vascularization, extreme thinning at the proposed host-graft junction and active corneal inflammation. Abnormalities of the eyelids ( blepharitis , ectropion , entropion and trichiasis ). Recurrent or progressive forms of conjunctival inflammation. Tear film dysfunction. Anterior synechiae . Uncontrolled glaucoma . Uveitis.

8. Penetrating keratoplasty most commonly performed corneal transplantation procedure. INDICATIONS INCLUDE: Disease involving all layers of the cornea . Specific common indications: keratoconus , pseudophakic bullous keratopathy , Fuchs endothelial and other dystrophies.

9. Technique: Determination of graft size: by trial placement of trephines with different diameters or by measurement with a calliper . An ideal size is 7.5  mm. grafts smaller than this may give rise to high astigmatism . Grafts of diameter 8.5 mm or more are prone to postoperative anterior synechiae formation, vascularization and increased intraocular pressure.

10. Excision of donor corneal button - The donor corneal button should be trephined 0.25 mm larger than the recipient, taking care not to damage the endothelium. to facilitate watertight closure, minimize postoperative flattening and reduce the possibility of postoperative glaucoma.

11. Excision of recipient corneal button - care should be taken, not to damage the iris and lens. - Recipient trephining can be performed freehand or with suction trephine systems which stabilize the globe and ensure that the angle of trephination is perpendicular to the surface.

12. Suturing of corneal graft into the host bed is done with either continuous or interrupted 10-0 nylon sutures.

13. Postoperative management: Topical steroids are used to decrease the risk of immunological graft rejection . Other immunosuppressants –azathioprine, ciclosporin may be rarely used in high-risk for prevention of rejection. Mydriatics - if uveitis persists . Monitoring of IOP is performed during the early postoperative period. Removal of sutures when the graft-host junction has healed. This is usually after 12–18 months. Rigid contact lenses -to optimize visual acuity in eyes with astigmatism .

14. Postoperative complications: Early complications: persistent epithelial defects, irritation by protruding sutures, wound leak, flat anterior chamber, iris prolapse, uveitis, elevation of intraocular pressure, microbial keratitis and endophthalmitis . Late : astigmatism , recurrence of initial disease process, late wound separation, retro-corneal membrane formation, glaucoma and cystoid macular oedema .

15. Superficial lamellar keratoplasty This involves partial thickness excision of the corneal epithelium and stroma . endothelium and part of the deep stroma are left behind . Indications: Opacification of the superficial one-third of the corneal stroma . Marginal corneal thinning or infiltration as in recurrent pterygium , marginal degeneration. Localized thinning or descemetocele formation.

16. Deep anterior lamellar keratoplasty O paque corneal tissue is removed almost to the level of Descemet membrane. decreased risk of rejection because the endothelium, a major target for rejection, is not transplanted. Indications: Disease involving the anterior 95% of corneal thickness with a normal endothelium and absence of breaks or scars in Descemet membrane . Chronic inflammatory disease such as atopic keratoconjunctivitis which carries an increased risk of graft rejection.

17. Descemet stripping endothelial keratoplasty It involves removal only of diseased endothelium along with Descemet membrane, through a corneoscleral or corneal incision . Folded donor tissue is introduced through the same small (about 5 mm) incision. Indications: include endothelial disease such as pseudophakic bullous keratopathy .