Cases of corneal ectatic disorders in which corneal thinning extends to the periphery are difficult to treat surgically. Some examples of corneal ectatic disorders include keratoglobus, severe keratoconus, concurrent keratoconus and pellucid marginal degeneration (PMD), peripheral progression of keratoconus after penetrating keratoplasty (PK). Standard surgical techniques, such as lamellar keratoplasty, may not be appropriate for these cases, as there is no tectonically stable host margin to which to affix the graft. Furthermore, discrepancy between thickness of the host and donor corneas creates a difficult procedure, often concluding with poor visual results.
In theory, larger-diameter grafts may be appropriate choices for patients with corneal thinning at the periphery; however, graft survival is poor and reports show that up to 100% of grafts are rejected.1 Other surgical techniques, such as epikeratoplasty or corneoscleroplasty, vary in their degree of success.2-6 Recently, we devised a lamellar technique designed for the treatment of these advanced corneal ectasias.7-8 Called tuck-in lamellar keratoplasty (TILK), this technique is designed to provide adequate tectonic support to the central and peripheral cornea, avoiding damage to the limbal stem cells or drainage angle. Currently, TILK is indicated in keratoglobus, severe keratoconus involving the peripheral cornea, concurrent keratoconus and PMD, and peripheral progression of keratoconus.
TILK may be performed under local or general anesthesia; however, we prefer general. As is also the case during standard lamellar keratoplasty, the host cornea is prepared first (see Preparation of the Host Bed) and the donor cornea second (see Preparation of the Graft). The donor lenticule should have a peripheral partial thickness flange of posterior stromal tissue. The central 8.5 mm of the graft provides tectonic support to the central ectatic cornea, and the peripheral flange is integrated into the host to provide tectonic support at the peripheral cornea.7-8 The peripheral flange can extend circumferentially7 or across only the inferior aspect of the donor lenticule.8 Placement of the flange corresponds to the area of thinning. The graft may then be fixated to the host (see Fixation of the Graft). Figure 5 reveals the postoperative appearance of the fixated graft.
After successful completion of TILK, we prescribe topical steroids and antibiotics, tapered over 3 to 4 months, and topical unpreserved lubricants for 6 months. Patients are followed weekly for 1 month, monthly until 6 months, and every 6 months thereafter. Sutures were removed at 6 months.
We have used TILK to successfully treat cases of extreme corneal ectasia.7-8 In a study by Kaushal et al,8 12 of 12 grafts were clear at last follow-up (mean, 1.7 years), and there was no significant interface haze or corneal vascularization. Preoperatively, all patients had BCVA of less than 20/200. Postoperatively, all patients' BCVA improved to 20/80 or better. Spherical equivalent refractive error decreased from a mean of -7.80 D to -1.23 D at last follow-up.
TILK provides a single-stage technique for the management of extreme corneal ectasias, successfully stabilizing the peripheral cornea and allowing optimal visual outcome, without compromise to the host limbal stem cells.
Jacqueline Beltz, MBBS, is a corneal fellow at the Centre for Eye Research Australia. Dr. Beltz states that she has no financial interest in the products or companies mentioned. She may be reached at e-mail: firstname.lastname@example.org.
Rasik B. Vajpayee, MS, FRCS(Edin), FRANZCO, is Head of the Corneal Unit at the Centre for Eye Research Australia. Dr. Vajpayee states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +61 3 9929 8368; fax: +61 3 9662 3959; e-mail: email@example.com.