COMMENTARY

New Simple Limbal Epithelial Transplantation Method Promising in Ocular Burns

Christopher J. Rapuano, MD

Disclosures

July 21, 2016

Viewpoint

The corneal epithelium is produced by the stem cells located deep in the palisades of Vogt at the limbus. When this limbal tissue is damaged, it either results in the corneal epithelium failing to heal, in turn causing a persistent epithelial defect, or in the conjunctival epithelium growing over the cornea. The conjunctival epithelium, however, is not as smooth as the corneal epithelium, resulting in reduced vision and a risk for corneal vascularization.

Fortunately, limbal stem cells can be transplanted, thereby normalizing the corneal surface. One of the techniques for limbal stem cell transplantation is to remove a small amount of limbal stem cells from the normal fellow eye and, in a specialized clinical laboratory, induce the cells to greatly increase their number. At a later date, these additional limbal stem cells are transplanted to the damaged recipient eye. Although this technique is successful, it is expensive and time-consuming and has significant regulatory restrictions in many countries, including the United States.

The authors note in their discussion that they see approximately 100 new cases of severe ocular burns every year, which seems extremely high to me. However, they operate out of a tertiary eye care center in India, a country with a huge population and a large number of industrial and domestic accidents. Of note, the most common cause of LSCD in children in this study was accidental "edible lime-related trauma." Compared with adults, children in the study had more alkali injuries (although they had a similar numbers of acid injuries) and more severe symblepharon.

The study authors had performed over 1000 of the ex vivo cultivated limbal epithelial transplants when they developed their SLET technique in 2010. SLET is a relatively rapid single procedure (albeit on both eyes) that does not involve maintaining a clinical-grade laboratory.

The success of SLET has surprised many ophthalmologists, because it essentially refuted the long-standing belief that you needed a minimum of approximately 3-6 clock-hours of limbal stem cells to repopulate an entire cornea. With the SLET procedure used in this study, transplanting 1 clock-hour of limbal stem cell tissue resulted in complete corneal re-epithelialization in approximately 75% of eyes. It is unknown whether a larger limbal piece (perhaps 2 clock-hours) might yield even better outcomes.

The relatively long-term results presented in this article are impressive. As mentioned earlier, the authors found acid injury, severe symblepharon, SLET combined with keratoplasty, and postoperative loss of SLET transplants to be risk factors for failure. They note that if symblepharon and severe corneal thinning were treated before or during the SLET procedure, the success rate might improve.

At a recent meeting, I heard about a modification of this technique in which the SLET grafts are covered with a second amniotic membrane tissue instead of a bandage soft contact lens in an attempt to minimize (ideally to the point of elimination) the loss of SLET grafts postoperatively. The SLET grafts reportedly remained in position and re-epithelialized the cornea without difficulty between the two amniotic membrane tissues. Another pearl I heard was to place the small SLET grafts outside the central cornea, because when they heal they do so with small corneal opacities, which are better kept outside the visual axis.

Although most of us don't see many patients with unilateral LSCD, we should consider performing SLET when we do. I know I will.

Abstract

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