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Limbal-sparing lamellar keratoplasty

Stephanie L Watson, Saaeha Rauz, John Dart

Corneal and External diseases, Moorfields Eye Hospital NHS Foundation Trust

Correspondence: Miss SL Watson, Corneal and External Disease, Moorfields Eye Hospital NHS Foundation Trust, City Road, London, EC1V 2PD. Tel: 0207 566 2821; Fax: 0207 566 2821; Email: stephanie.watson{at}moorfields.nhs.uk stephanie.watson{at}moorfields.nhs.uk

Accepted for publication:  December 2nd, 2004

 

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Keywords
Limbus, Lamellar, Keratoplasty, Corneoscleral ectasia, Limbal stem cell

Introduction
Extreme corneal thinning extending to the limbus occasionally follows severe corneal inflammation, such as Mooren's ulcer, or may occur in advanced corneal ectasia. Corneal reconstruction in these cases requires a large tectonic lamellar graft instead of penetrating keratoplasty (PK) (1;2). Conventional PK can then be performed at a later date to restore vision, if necessary. (1) Such large tectonic grafts are often attached to the anterior scleral tissue necessitating excision of the limbus, with a risk of surface failure if the majority of the limbus is involved. (1) In this situation a corneal allograft with preservation of the autologous limbal tissue by superficial dissection and reflection provides an alternative to corneoscleral allografting. This technique of ‘limbal-sparing lamellar keratoplasty' (LSLK) is described in 3 cases and a surgical video presented.

 

Case Reports
Case 1
A 66-year-old man presented with bilateral corneal ectasia and visual acuities of 6/12 on the right and 1/60 on the left. A PK had previously been performed in his right eye for keratoconus. He had left superior keratoconus with a superior descemetocoele and pellucid marginal degeneration. LSLK was performed in this eye and an optimal unaided vision of 6/24 was achieved. Eight months later, he underwent left cataract extraction and intraocular lens (IOL) implantation, attaining a final visual acuity of 6/18. An epiretinal membrane was found on fundal examination.

Case 2
A 24-year-old Ethiopian man had recurrent episodes of bilateral interstitial keratitis, panuveitis, and scleritis of unknown aetiology that required systemic immunosuppression for control. Vision was right 6/36 and left 1/60. Lamellar keratoplasty had been performed in the right eye. Global ectasia and deep vascularisation affected the left cornea. (Figure 1A, B) LSLK was complicated by an interface haemorrhage; his vision was reduced to the perception of light. Post-operatively an exacerbation of bilateral scleritis and a left persistent epithelial defect were managed by increased immunosuppression and a therapeutic contact lens, respectively. (Figure 1C) Following control of his ocular inflammation for 3 months, PK and extracapsular cataract extraction with posterior chamber IOL implantation was performed within the lamellar graft. (Figure 1D) An epiretinal membrane limited the final vision to 6/60 achieved with a diagnostic contact lens. The corneal epithelium remained stable.

Case 3
A 41-year-old man with a diagnosis of Mooren's ulcer presented with a scarred, vascularised and grossly ectatic right cornea (VA=hand movements), and a small left PK surrounded by a thin and scarred host cornea (VA= hand movements). Although a right LSLK was performed, post-operative disease reactivation led to ulceration and melting of the lamellar graft. Oral immunosuppression induced remission and repeat LSLK was performed 9 months later followed by a right PK, extracapsular cataract extraction and posterior chamber IOL implantation a further 7 months later. The final post-operative visual acuity, with a scleral contact lens, was 6/6. Systemic immunosuppresion was tapered and then ceased.

Figure 1 Case two. A and B. Pre-operative photographs: Global corneal ectasia and vascularisation complicated by hydrops. C. Post-operative photograph: Persistent epithelial defect complicating limbal-sparing lamellar keratoplasty at 7 months post-operative. D. Post-operative photograph: Penetrating keratoplasty performed 10 months after limbal-sparing lamellar keratoplasty.

Surgical Techniques
In each case, LSLK was performed by creating a radial conjunctival incision in each quadrant. Host limbal tissue was dissected superficially via the conjunctival incisions and then reflected. The recipient bed was prepared by removing host epithelium facilitated by the application of ethanol 100% and, if there was adequate corneal tissue remaining, a superficial keratectomy. A freehand scleral groove was made with a 0.3mm step-knife peripheral to the limbus, a rim of anterior sclera trimmed, a sclera pocket fashioned in the recipient bed, and a paracentesis performed to release aqueous humour to facilitate fitting of the graft over the ectactic cornea. A custom-cut lamellar donor button was prepared from fresh whole donor eye; the endothelium and Descemet's membrane removed by direct visualisation with trypan blue (Vision Blue, DORC, The Netherlands). The posterior peripheral edge of the button was trimmed with vannas scissors to complement the area of trimmed scleral bed. Interrupted 9/0 nylon sutures were used to suture the graft in place with long bites into the scleral pocket. Host limbal tissue was repositioned and sutured with 8/0 vicryl to the graft at the limbus.

Comment
A technique for lamellar keratoplasty with limbal preservation in three patients with different aetiologies of corneal ectasia has been described. Tectonic repair was achieved in all cases thereby reducing the risk of perforation in the event of progressive corneal thinning.

Similar techniques (1;2) have previously been described for keratoglobus in which maximal corneal thinning occurs in the midperiphery. In these techniques (2) dissection of the limbus is performed from the corneal side following superficial trephination of the peripheral cornea. We have demonstrated our technique in Mooren's ulceration, interstitial keratitis and in a patient with superior keratoconus, pellucid marginal degeneration and a superior descemetocoele. In all cases, thinning was severe both centrally and in the peripheral cornea. Dissection of the limbus was performed from the conjunctival side to avoid inadvertent perforation on corneal trephination.

Following primary tectonic surgery, visual acuity may improve to adequate levels for the needs of the patient, or as in case 1, after additional cataract surgery. By contrast, as in cases 2 and 3, a secondary PK with or without combined cataract surgery may achieve further visual rehabilitation. (1;2) In the first instance, the primary lamellar surgical procedure is the definitive grafting procedure and virtually eliminates the risk of endothelial rejection that may occur if a secondary PK was performed. (2)

Limbal epithelial stem cells (LESC) are a small population of cells at the limbus that are the source of transient amplifying cells that migrate, proliferate and differentiate to maintain a stable corneal epithelium. Preservation of the limbus is therefore essential during surgery to minimise the risk of post-operative epithelial disturbance, especially in patients with pre-existent ocular surface disease.

Large corneoscleral lamellar grafts have previously been described for a variety of conditions including keratoglobus, post-herpetic corneal perforation, rheumatoid corneal melt, Mooren's ulceration, dermoids, ocular surface disorders associated with Stevens-Johnson syndrome, ocular cicatricial pemphigoid, chemical burns and oculus fragilis (1-3). Post-operative complications after such surgery include persistent epithelial defects due to an iatrogenically compromised limbus, graft/interface vascularisation, and graft rejection. (2;3) In one retrospective case series of conventional keratolimbal lamellar grafts seven of eight cases experienced persistent epithelial defects; infection complicated 4 of these cases. (3)

Modern surgical instrumentation, such as adjustable stepped diamond knifes, have facilitated conventional lamellar surgery and the development of techniques that spare the limbus. (1;2) Limbal-sparing lamellar surgery should be considered as a viable option for reconstruction of extreme corneal thinning that extends to the limbus and could possibly be combined with newer techniques that augment LESC numbers or improve their microenvironment.

 

Acknowledgements
SL Watson is supported by a Gustav Nossal National Health and Medical Research Council Scholarship, Australia.
The authors have no financial interest in the subject matter.

 

References

(1) Jones D, Kirkness CM. A new surgical technique for keratoglobus-tectonic lamellar keratoplasty followed by secondary penetrating keratoplasty. Cornea 2001; 20(8):885-7.

(2) Vajpayee RB, Bhartiya P, Sharma N. Central lamellar keratoplasty with peripheral intralamellar tuck. A new surgical technique for keratoglobus. Cornea 2002; 21(7):657-660.

(3) Shimmura S, Ando M, Shimazaki J, Tsubota K. Complications with one-piece lamellar keratolimbal grafts for simultaneous limbal and corneal pathologies. Cornea 2000; 19(4):439-442.