8.1.6.3  The Limbus Allograft

The limbus allograft has the same goal as the autograft [24]. The limbus allograft is operated in case of extended limbal lesions whether they are bilateral or unilateral on a unique eye. The tissue is sampled from a corneal graft or from an eye kept by a bank of tissues. The graft must be sampled within 24 h because the lifetime of LSC in a preservation milieu is not well known [25]. The sample must fulfill the requirements of a transfixion keratoplasty. It results from two concentric trepanations: one located 1 mm before the limbus and the other 2 mm at the back. The dissection of a lamella goes from the corneal side – as a starting point – to the conjunctiva. The dimension of the sample relates to the limbal destruction. It may cover all of the limbal edge (360°). It is sutured to the receiving cornea by some separated stitches of 10/0 nylon threads and to the conjunctiva by some resorbable 8/0 threads. The sample may be more scarcely taken from a living donor who is a relative of the victim [26]. The limbus allograft improves the condition of the ocular surface in more than 50% cases. It also improves the prognosis of a secondary penetrating keratoplasty [17, 20, 27]. There is a major risk of graft rejection and this requires a prolonged immunosuppression. The therapy by corticoids and the cyclosporine are prescribed as local and general treatments. A matching HLA type between donor and recipient should lower the rejection risk, but it yet requires an immunosuppressive therapy [26, 28]. The limbus autograft combined with a transplantation of amniotic membrane enables the restoration of the corneal epithelium of normal phenotype [29].

8.1.7  The Transplantation

of Amniotic Membrane

Used for ocular burns as soon as 1947 by Sorsby [30], the amniotic membrane is a tissue located at the interface of the placenta and the amniotic fluid. It is constituted of an unstratified epithelium, a basement lamina, and an avascular mesenchyma. The amniotic membrane facilitates the reepithelialization by reducing the inflammatory and cicatricial reaction [31]. It helps the migration of the epithelial cells and the adhesion of the basement cells [32]. It behaves as an actual replacing basement membrane and facilitates the phenotypic

epithelial expression. As it is not doted of class II HLA antigens, the amniotic membrane cannot be rejected. The amniotic membrane used for transplantation comes from a placenta taken from a delivery without cesarean operation in order to reduce the risk of bacterial contamination. It is preserved frozen at a −80° temperature. The amniotic membrane must fulfill the same sanitary security norms as a transfixion keratoplasty. The sample of amniotic membrane is sutured, with its epithelial side upwards, to the deepithelialized cornea by some separated 10/0 nylon stitches. Several layers may be layered over each other. The amniotic membrane is covered by the corneal epithelium, integrated to the stroma then resorbed. It can be used for the reflection of the conjunctival sacs after exeresis of the symblepharons [32, 33]. The preoperatory application of 0.04% mitomycin C for 5 min before the positioning of the amniotic membrane would reduce the conjunctival inflammation and improve the depth of the conjunctival sacs and the quality of the lacrymal film [34]. The current trend is to practice the transplantation of amniotic membrane early enough, during the precocious phase of the burn. The reepithelialization would reach more than 80% within 15 days, the visual acuity would improve in 77% cases, and the symblepharons would be rare [35]. Even when the transplantation is practiced later, there are some good results [36].

The transplantation of amniotic membrane does not suffice for the treatment of a severe LSC deficiency due to a burn [37]. In such a case, it needs to be associated with an LSC transplantation. The amniotic membrane is first sutured to the deepithelialized cornea and the limbal graft is set astride the edge of the amniotic membrane [38]. The cicatrization of the corneal epithelium is completed for 75–100% cases within 3 weeks when the LSC deficit is incomplete and for 70% cases when the deficit is complete [39, 40].

8.1.8  Keratoplasties

8.1.8.1  Big Diameter Transfixion Keratoplasty

An 11–12 mm diameter transfixion keratoplasty (TK) provides a double advantage: that of an optic or architectonic keratoplasty and that of an intake of LSC guaranteeing the cicatrization of the corneal epithelium [41, 42]. It can be operated either in the precocious or in the

cicatricial phase of severe burns. The big diameter TK has a high risk of rejection, which alters its results. It is preferable to replace it with a preliminary LSC transplantation followed by a usual diameter TK.

8.1.8.2  The Usual Diameter Transfixion

Keratoplasty

Burns can cause an edema due to a toxic necrosis of the endothelial cells, an opacification of the corneal stroma, and a thinning of the stroma, which generates an important irregular astigmatism. The aim of the TK is to restore the corneal transparency.

Most of the time, the sampling of cornea is operated by in situ excision. Donors are selected according to criteria defined by the associations of cornea banks, who also assume the quality control, the preservation, and the distribution of the samples. The first step of intervention consists in trepanning the graft to a ­diameter close to 8 mm. The recipient cornea is then trepanned to a slightly smaller diameter. The most used is the Hessburg–Barron vacuum corneal trephine. The sample is sutured to the recipient cornea by separated stitches and/or by a continuous suture. The postoperatory treatment includes a corticoid collyrium coupled with an antibiotic collyrium prescribed for 1–2 years. Overall about 10%, the risk of rejection is higher for chemical burns, especially because of the frequency and the importance of the stromal neovascularization of the recipient cornea [43–45].

A TK does not provide any LSC; therefore, it does not suffice to treat extended limbal ischemia. It must be coupled with a limbus transplantation [46].

A TK can be practiced in the same operatory step as a limbus allograft. The intervention begins with a limbal peritectomy, followed by the TK [47]. However, the epithelial cicatrization and the corneal transparency are better when the TK is secondarily realized (from 1 to 13 months). The endothelial rejection is less important too: 0% against 53% for a transplantation occurring in the first month [18].

An auto-TK coupled with a limbus autograft may exceptionally be practiced as illustrated in Figs. 8.1–8.4.

This is the case of a monophthalmic left eye patient wounded by a grade 4 burn due to a strong base. Two TK have not succeeded because of successive rejections. The visual acuity of the left eye was reduced to a good localization of the light. The cornea was white,

Fig. 8.1  Right eye. No light perception. Presurgery aspect. Clear cornea, calm anterior chamber, old posterior synechia, extracapsular surgical aphakia. Normal ocular pressure

Fig. 8.2  Left eye. Presurgery aspect. Visual acuity reduced to a good localization of the light. White cornea, ulcerated and neovascularized. Complete limbus deficiency related to a 360° destruction of the limbus

ulcerated, and neovascularized. There was a complete limbus deficiency. The right eye had not been functioning since childhood because of a closed contusion. In the same operatory step, we have sampled from the right eye: the cornea (8 mm trepanation) and the limbus over 360°. After the ablation of the conjunctival pannus covering the limbus and the cornea of the left eye, we have transplanted the cornea and the limbus, which had previously been sampled from the left eye.

Fig. 8.3  Right eye. One month postsurgery. White left cornea sutured with 16 separated stitches of 10/0 nylon

Fig. 8.4  Left eye. One month postsurgery. Clear right cornea sutured with 16 separated stitches of 10/0 nylon. 360° limbus autograft taken from right eye and sutured with 8 separated stitches of 10/0 nylon on the cornea and with 8 separated stitches of 8/0 vicryl on the conjunctiva

8.1.8.3  The Deep Lamellar Keratoplasty

The deep lamellar keratoplasty (DLK) consists in transplanting the stroma and the epithelium of the graft while preserving the Descemet membrane and the endothelium of the recipient. It is used to treat corneal burns in which the Descemet membrane and the endothelium have been spared. The graft is sampled and preserved in the same conditions as the graft used for a TK. The operation begins with an 8 mm

trepanation of the graft, followed by a non-transfixing 75% trepanation of the thinnest part of the recipient’s cornea. A dissection enables the ablation of the epithelium and of the anterior and medium stroma. An injection of air into the posterior stroma helps to loosen the Descemet membrane and therefore facilitates its exeresis. The Descemet membrane of the sample is removed with the use of a pincer and the graft is sutured to the recipient cornea in the same manner as when practicing a TK.

As the endothelium is not grafted, the risk of endothelial rejection is nil. Yao records the results achieved by limbus autografts combined with DLP for 34 patients with sequelae due to unilateral corneal burns. All patients were operated at least 6 months after the burn. All had normal lacrymal secretion. The DLP was practiced at the same operatory time as the limbus autograft. The operation begins with the DLP, followed by the limbus autograft. In 30 cases, there is an improvement of the visual acuity and the central corneal transparency is restored for 29 patients [48]. The series of Fogla includes seven eyes. Very good results are also noticed: improvement of the visual acuity for 85% cases and a 4/10 average postoperatory visual acuity [49]. The practice of a DLP with limbus autograft does not require any immunosuppressive therapy. In comparison with TK, the risk of failure is lower even when the cornea is highly ­neovascularized [49].

8.1.8.4  The Big Diameter Lamellar Keratoplasty

The big diameter LK was first introduced in the year 2000 by Vajpayee [50] for a use in the surgical treatment of sequelae due to corneal burns. Vajpayee has recorded the results of nine ocular operations. The intervention begins with a conjunctival peritectomy over 360°. The conjunctiva is reclined backwards. The recipient cornea is trepanned to a 12–13 mm diameter and to a 300 mm depth. The lamellar graft is sampled via a trepanation at 1.5 mm back to the limbus in order to include LSC. It is then sutured by 24 10/0 nylon stitches. Despite the limbus allograft, no immunosuppressive therapy has been prescribed. The operation was practiced about 30 months after the occurrence of the burn. Results are recorded after a 7.4 month observation. The visual acuity has improved in six cases. No recurrence of the corneal neovascularization and no