Lamellar keratoplasty

Indications for lamellar keratoplasty were corneal haziness leading to decreased visual acuity, photophobia, discomfort caused by corneal surface irregularity, abnormal deposits or severe thinning threatening globe integrity, or a combination thereof ( Figure 1 , Left). A Barron-Hessburg suction trephine with a diameter of 7.0 to 8.0 mm (based on the vertical corneal diameter and the extent of corneal involvement) was used to trephine at least 50% of the corneal thickness, and manual lamellar dissection was performed using a crescent blade (Alcon Laboratories, Fort Worth, Texas, USA). During lamellar dissection, an attempt was made to remove all scars and deposits, which chiefly were confined to the anterior and mid stroma, and to create a single-plane, smooth, and clear recipient bed ( Figure 1 , Right). A partial-thickness donated cornea, prepared from a fresh whole globe with an intact epithelium and oversized by 0.5 mm, was sutured into the recipient bed using 10-0 nylon sutures (Sharpoint; Angiotech, Vancouver, Canada). In most cases, temporary or permanent lateral tarsorrhaphy, punctal occlusion, or both were performed on conclusion of the operation.

Photographs showing abnormalities of the limbal region and cornea in mustard gas keratitis. (Left) Conjunctiva contains areas of ischemia and vessel tortuosity and the cornea demonstrates surface irregularity, thinning, and intrastromal lipid and amyloid deposits. (Right) Simultaneous keratolimbal allograft and lamellar keratoplasty were performed to address coexisting mustard gas-induced limbal stem cell deficiency and corneal involvements in the same patient. A portion of the deeply located opacity was left in the stromal bed.

In 3 eyes, deep anterior lamellar keratoplasty was attempted using the Anwar big-bubble technique. However, the procedure very soon was abandoned because it was not possible to achieve a successful big bubble even after several intrastromal air injections.

Stem cell transplantation

Limbal stem cell deficiency was diagnosed clinically as shown by limbal ischemia, loss of limbal palisades of Vogt, corneal surface irregularities, superficial vascularization ( Figure 2 , Left), and late corneal staining with fluorescein ( Figure 2 , Right) and was confirmed in 11 eyes using impression cytologic analysis. Limbal stem transplants, which were segmental in all cases, were harvested from cadaveric eyes (keratolimbal allograft) without human leukocyte antigen matching.

Images showing limbal stem cell deficiency caused by mustard gas. (Left) Normal corneal epithelium is replaced with conjunctival epithelium, resulting in surface irregularities and superficial vascularization. (Right) Pooling and late staining of corneal epithelium with fluorescein indicates an abnormal epithelial layer.

To prepare the recipient bed, involved limbal areas adjacent to the epithelial defects or thin cornea were chosen, and local peritomy, shaving, and mild cauterization of the sclera were performed. This was followed by half-thickness rectangular corneoscleral removal with an attempt to dissect all ischemic limbal areas as well as peripheral thin and opaque corneas up to the paracentral areas, if necessary. A corneoscleral block exactly matching the shape of the recipient bed and containing conjunctiva was prepared from a cadaveric eye and was sutured to the bed with interrupted 10-0 nylon sutures (Sharpoint; Figure 1 , Right).

When indicated, both types of transplantation were performed either sequentially or simultaneously. Initially, a staged approach, in which keratolimbal allograft was performed first ( Figure 3 , Left) and then followed by lamellar keratoplasty after a few months, was carried out. Additionally, in some cases, limbal stem cell deficiency did not coincide with severe corneal opacities necessitating lamellar keratoplasty at the time. In these eyes, lamellar keratoplasty was performed after keratolimbal allograft when corneal involvements became severe enough to justify corneal transplantation. After a while, however, the technique evolved to a simultaneous approach in which the recipient was prepared for both transplantations harvested from a single cadaveric eye ( Figure 1 , Right).

Images showing segmental keratolimbal allograft for the management of localized mustard gas-induced limbal stem cell deficiency. (Left) In addition to providing stem cells, the graft is large enough to replace the abnormal peripheral stroma. (Right) Fluorescein staining demonstrates a regular corneal surface after keratolimbal allograft in the same patient.

Postoperative course

In all cases, topical eye drops, including chloramphenicol 0.5% every 6 hours, betamethasone 0.1% every 6 hours, preservative-free artificial tears every 2 hours, and lubricants every 8 hours, as well as systemic prednisolone 1 mg/kg daily, were started after surgery. The topical antibiotic was discontinued after complete reepithelialization, and systemic and topical corticosteroids were tapered off and discontinued over 2 to 4 weeks and 2 to 3 months, respectively, according to the severity of the ocular inflammation.

For patients who underwent keratolimbal allograft, oral cyclosporine A (Sandimmune; Novartis Pharma, Tokyo, Japan) 5 mg/kg daily, which was decreased to 3 mg/kg daily after a few weeks, and mycophenolate mofetil (CellCept; Hoffmann La Roche, Nutley, New Jersey, USA) 1 g twice daily were started at the time of surgery and were continued for at least 6 months. Afterward, the systemic immunosuppressive medications gradually were tapered off and discontinued after 1.5 to 2 years according to the condition of the patients. Cell blood counts, blood pressure, and renal and liver function tests were monitored at appropriate intervals in collaboration with a kidney transplant expert to monitor for possible complications of immunosuppressive therapy.

An episode of corneal graft rejection was defined as subepithelial or stromal infiltration in the corneal grafts. Corneal graft failure was diagnosed when the central portion of the graft became significantly opaque because of scarring, with or without vascularization (limbal stem cell deficiency or corneal ulcer). The presence of significant interface haziness involving the visual axis also was considered to be a failure ( Figure 4 ) . In eyes that underwent stem cell transplantation, acute stem cell graft rejection was diagnosed by limbal and perilimbal vascular engorgement, conjunctival chemosis in the transplant areas, or both ( Figure 5 ) . Stem cell transplantation failure was diagnosed in cases with progressive corneal vascularization or persistent epithelial defects (more than 2 weeks) adjacent to the graft. Acute rejection episodes of both corneal and stem cell transplantations were treated by increasing the dose and frequency of topical or systemic steroids, or both.

Image showing graft–host interface haziness 4 years after lamellar keratoplasty for mustard gas keratitis. The interface is invaded by new vessels stemming from the heavily vascularized recipient cornea, which leads to significant interface haziness encroaching on the visual axis.

Image showing an acute episode of stem cell graft rejection after keratolimbal allograft for mustard gas-induced limbal stem cell deficiency. Limbal vessels adjacent to the keratolimbal block are engorged.