Conjunctival Limbal Autograft

Indications

A conjunctival limbal autograft (CLAU) is indicated for patients needing epithelial stem cell (SC) transplantation for management of corneal surface disease due to unilateral limbal stem cell deficiency (Table 16.1). Prior chemical or thermal injuries are the most common causes of limbal SC deficiency. Other etiologies include iatrogenic limbal SC deficiency and extensive limbal or conjunctival neoplasias, such as conjunctival intraepithelial neoplasia, squamous cell carcinoma, and sebaceous cell carcinoma. Although these groups account for the majority of cases of unilateral limbal SC deficiency, it is important to recognize that additional cases can occur as a result of any condition where the common underlying pathology is chronic, usually severe, ocular surface inflammation.

Contraindications

In considering a CLAU for unilateral ocular surface disease (OSD), the vital criterion for tissue selection is that the donor eye be free from any condition that may predispose it to later development of limbal SC deficiency, such as long-term contact lens use, multiple prior surgeries, or glaucoma (where the success of potential future filtering surgery could be adversely affected by prior conjunctival surgery). Jenkins et al.1 reported on conjunctival limbal autografts in five patients with severe epitheliopathy secondary to chronic contact lens wear. Two of the five procedures failed, and one of the donor eyes developed epitheliopathy. These results are likely due to the fact that the donor tissue was obtained from the fellow eyes that were not normal, in that they had also been exposed to chronic contact lens wear. Patients with contact-lens-induced keratopathy may present with unilateral (typically superior) limbal deficiency. Yet with the exception of the rare instance in which the individual has worn a contact lens only in the

affected eye, a CLAU from the other eye is ill advised in any bilateral long-term contact lens wearer due to the risk of causing limbal SC deficiency in the donor eye. If any contraindications exist, either a living-related conjunctival allograft or a keratolimbal allograft is advised.

Past, Present and Future of CLAU

The Evolution of CLAU

Procedures designed to restore normal corneal epithelium have evolved over the past several decades. Epithelial transplantation for severe ocular surface disease was first described in 1977 by Thoft,2 when he described conjunctival transplantation for monocular chemical burns. This conjunctival autograft procedure used several pieces of bulbar conjunctiva from a normal fellow eye as donor tissue. In 3 of 17 eyes, successful reepithelialization of the cornea was achieved and was accompanied by improved vision and decreased neovascularization. The mean follow-up time of 9 months was relatively short. In 1982 Thoft reported on an additional 17 cases of ocular surface disease that were managed with a conjunctival autograft.3 Sixteen of these eyes achieved a stable ocular surface with a median followup of 36 months and a range of 12 to 60 months. Ten of these eyes had a significant improvement in vision. In 1982, Vastine et al.4 reported on the use of conjunctival autografts from fellow eyes in 14 patients, 7 with diagnoses consistent with limbal deficiency. They reported that all 7 of these cases developed a stable ocular surface postoperatively with a median follow-up of 16.5 months and a range of 10 to 18 months.

The conjunctival autograft procedure was based on the concept of conjunctival transdifferentiation.2,4,5,6 Although a conjunctival autograft is useful to re-establish an intact ocular surface in patients with conjunctival scarring, concerns exist whether this procedure truly results in normal corneal epithelium.7 Tsai et al.8 com-

pared the results of limbal transplantation to conjunctival transplantation in a rabbit model of OSD. They reported a significant decrease in corneal neovascularization with limbal transplantation, and the resultant corneal epithelia displayed the corneal phenotype. Conjunctival transplantation resulted in corneal epithelia with the phenotype of conjunctiva. The technique of conjunctival autograft remains a valuable procedure for the management of fornix reconstruction and primary and recurrent pterygium, but the success of conjunctival transplantation for the establishment of the corneal surface when a source of limbal stem cells is not available remains to be determined. It is possible that in some of the patients reported above there was only conjunctival or partial limbal deficiency, so that with transfer of healthy, noninflamed conjunctiva the recipient eye improved because of reduced inflammation, allowing the residual healthy limbal tissue to restore the corneal epithelium to its proper state.

Procedures to transplant the limbus have been devised based on the concept of limbal stem cells. Kenyon and Tseng9 in 1989 described a modification of the conjunctival autograft, which they named limbal autograft transplantation. In this procedure, conjunctiva and limbus from a normal fellow were used to manage diffuse limbal deficiency in unilateral ocular surface disease, or focal limbal deficiency in unilateral or bilateral disease. Their technique used grafts of bulbar conjunctiva that extended approximately 0.5 millimeter onto the clear cornea centrally, thus containing limbal cells. The authors reported data on 21 cases with 6 months or more of fol- low-up. Preoperative diagnoses included acute and chronic chemical injuries, thermal injury, contact-lens- induced keratopathy, and surface disease secondary to multiple surgeries. The results were impressive with rapid surface healing in 19 cases, stable ocular surface in 20 cases, improved visual acuity in 17 cases, and arrest or regression of corneal neovascularization in 15 cases. No complications developed in the donor eyes. Seven of 7 patients underwent simultaneous or subsequent successful penetrating or lamellar keratoplasty. Based on the nomenclature system of Holland and Schwartz,5 this procedure is termed conjunctival limbal autograft.

Present and Future Use of CLAU

CLAU has been a major advance in the management of severe unilateral OSD. These procedures are now widely utilized by many corneal surgeons, and numerous patients have benefitted. As indicated earlier, a concern remains of potentially inducing iatrogenic limbal SC deficiency in the donor eye. Fortunately, the risk appears quite low based on several decades of both our clinical experience, and that of others in the literature.9

In Chapter 21, Drs. Isseroff and Schwab discuss exciting recent advancements in ex vivo stem cell expansion, which potentially could eliminate the need for harvesting relatively larger amounts of limbal tissue for autologous SC transfer. Such a breakthrough will be readily welcomed, although with the reality of inequitable availability of economic and medical resources around the world, it would not likely eliminate the usefulness and need for the standard CLAU procedure for many years to come.

Preoperative Considerations

Risks and Benefits

The major benefit in using autologous tissue as the donor source in any ocular epithelial transplantation procedure is that the need for systemic immunosuppression is eliminated, since there is no risk for tissue rejection. Additionally, a CLAU is particularly beneficial for patients with conjunctival inflammation because it provides normal, noninflamed, unscarred conjunctiva in addition to healthy limbal stem cells. These benefits can improve the prognosis for a favorable outcome compared to allograft procedures.

A major concern already discussed is the potential risk for the donor fellow eye. One study has demonstrated that partial removal of full-thickness limbal zone will compromise the donor surface.10 When a large corneal epithelial defect was subsequently introduced in these eyes, a clinical picture consistent with limbal deficiency occurred. In addition, it has been shown that even the removal of partial-thickness limbal epithelium

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could cause a milder form of limbal deficiency and abnormal corneal epithelial wound healing.11 We believe the risk of donor epithelial problems is low especially if less than 6 clock hours of limbal tissue and a moderate amount of conjunctiva are removed from the donor eye. We have not seen complications in the donor eyes of our patients, nor did Kenyon and Tseng9 in one of the largest series of CLAU in the literature.

Management of Coexistent Pathology

Ocular adnexa and anterior segment structures of patients with severe OSD must be carefully examined. Abnormal globe-to-eyelid anatomy can lead to chronic exposure, chronic inflammation, and direct corneal trauma with resultant complications such as recurrent corneal epithelial erosion, secondary microbial keratitis, vascularization, and scarring. Significant abnormal lid positions such as entropion or ectropion should be corrected prior to limbal transplantation. Trichiasis and distichiasis can be treated with cryotherapy, argon laser, surgical excision, or manual epilation. Palpebral conjunctival keratinization and loss of normal forniceal architecture can be treated with mucous membrane or amniotic membrane grafting.

An assessment of aqueous tear production should be performed. Patients with a low Schirmer test, a scant tear lake, and rose bengal or fluorescein staining consistent with aqueous tear deficiency usually require permanent punctal occlusion. Additional medical management of dry eye from either aqueous or lipid tear deficiency is covered in Chapter 4. Blepharitis should also be treated maximally and is covered in Chapter 3. If lagophthalmos or poor lid closure exists, lateral tarsorrhaphy at the time of surgery will improve chances for success by narrowing the palpebral fissure and improving ocular surface wetting through reduced surface area exposure and tear evaporation.

It is crucial to ask about any past history of glaucoma, and to look for evidence of this condition during the physical examination. Patients with severe OSD are at increased risk for developing secondary glaucoma. Prolonged anterior segment inflammation after chemical and thermal injuries can cause scarring and decreased functioning of the trabecular meshwork and normal aqueous outflow pathways. Chronic topical corticosteroid adds additional risk. Patients with iatrogenic limbal SC deficiency from multiple prior surgical procedures may have poorly controlled intraocular pressures if there is significant scarring of the peripheral angle of the anterior chamber. Glaucoma should be managed aggressively to ensure the best prognosis for visual rehabilitation. Poorly controlled chronic glaucoma is a major risk factor for long-term poor visual outcome in patients who otherwise undergo successful limbal SC grafting.

C.R. Croasdale, E.J. Holland, and M.J. Mannis

Surgical Technique

This procedure involves transfer of limbal stem cells from the healthy fellow eye to the diseased eye primarily utilizing conjunctiva as a carrier.

Anesthesia

The procedure involves both eyes. If the patient is healthy and can safely tolerate general anesthesia, this is often our preferred method because it eliminates time constraints of local anesthesia and reduces patient anxiety over a bilateral procedure. Alternatively, local anesthesia can be employed with a perior retrobulbar block with or without a VIIth cranial nerve block (O’Brien) for the recipient eye, and topical/subconjunctival anesthesia for the donor eye.

Preparation of the Recipient Eye

Any speculum providing adequate exposure is used. A lateral canthotomy is sometimes necessary to increase exposure. If symblepharon formation has occurred and limits exposure of the ocular surface, it can be released at the limbus.

A 360° limbal peritomy is performed, and conjunctiva is resected posteriorly 2 to 3 mm from the limbus with Westcott scissors. It is important to remove this tissue from the limbus because the new source of epithelium must repopulate the ocular surface prior to reinvasion by the fibrovascular tissue of the conjunctiva. Extensive bleeding can occur due to neovascularization of the injured eye’s surface. If this interferes with visualization, one can operate on a single quadrant at a time to control bleeding. Topical epinephrine (1:10,000 dilution) and thrombin applied with surgical spears are useful adjuncts to wet-field cautery. Once the limbal conjunctival tissue is excised, the recipient CLAU sites are prepared. The grafts will be centered at the 12 o’clock and 6 o’clock meridians and will measure approximately 8 mm horizontally by 5–8 mm vertically (no more than 3 clock hours each). If the limbal peritomy and conjunctival recession do not accommodate these dimensions, additional resection is done at the recipient sites as necessary (Figure 16.1A).

Next, abnormal corneal epithelium and fibrovascular pannus are removed by superficial dissection. Various approaches can be useful. Blunt dissection with a cellulose sponge may work. If a dissection plane is established, forceps can sometimes be used to peel off the abnormal tissue in a sheet. However, sharp dissection is often needed in areas to find an adequate tissue plane to create a smooth ocular surface. A No. 64 Beaver or equivalent crescent blade can be used for this maneuver. Care is taken to avoid cutting deep into stroma because of the risk of corneal perforation and postoperative optical distortion from surface irregularity. Bleeding is often encountered with the corneal surface

pannus removal, and topical epinephrine and thrombin can be used on this tissue as well (Fig. 16.1B).

When hemostasis is achieved, the surface is moistened, the speculum removed, and the eyelids are closed while the autografts are being harvested from the other eye.

Harvesting the Donor Tissue

The speculum is placed in the fellow eye. The two conjunctival limbal autografts are taken from the corre-

sponding 12 o’clock and 6 o’clock positions. A gentian violet surgical marking pen is used to mark the conjunctival portions of the grafts with the same dimensions as the recipient beds. Light cautery can be used to mark the conjunctival dimensions, although drawbacks include tissue damage and potential fusion of the conjunctiva to the underlying Tenon’s capsule. The conjunctiva can be elevated from Tenon’s layer with use of a subconjunctival injection of balanced salt solution or anesthetic without epinephrine. The needle entry point

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into the conjunctiva should be outside of the graft portion to minimize unnecessary defects. Dissection of the graft begins by incising with Westcott scissors along the lateral borders. If possible, the tissue should be completely undermined between the lateral edges before cutting along the posterior edge. This sequence helps keep the tissue on stretch. Once the posterior edge is cut, the thin conjunctival tissue folds and scrolls easily upon itself, making inadvertent damage such as buttonholes somewhat more likely. Non-toothed forceps are recommended to help avoid tearing the tissue. When the graft is completely free it is possible to become confused as to proper orientation. For this reason

C.R. Croasdale, E.J. Holland, and M.J. Mannis

it is helpful to include the gentian violet markings within the graft to delineate which side is the epithelial surface (Figure 16.1C).

Once the lateral and posterior edges are free, the conjunctiva is reflected anteriorly over the cornea and blunt dissection is continued anteriorly. When the point of conjunctival insertion at the limbus is reached, further blunt dissection should be performed with a dull scarifier (e.g., Tooke blade) into the peripheral cornea approximately 1 mm beyond the peripheral corneal vascular arcades. Some surgeons may prefer to complete the epitheliectomy with a sharp crescent blade, or even Vannas scissors. The desired corneal epithelial extent of

16. Conjunctival Limbal Autograft

the dissection should be lightly marked with any type of blade from the corneal side. It is important to emphasize that this maneuver is essentially a superficial epithelial keratectomy of peripheral limbus and cornea and not a lamellar dissection into stroma or sclera. It is also extremely important to carry the dissection onto the peripheral cornea and to avoid prematurely excising the piece of tissue without the SCs.

Once the tissue is free, it is transferred epithelial- side-upward to a Petri dish and covered with corneal storage media (or balanced salt solution if the former is unavailable). The same procedure is completed at the 6 o’clock position. The donor sites are left open to

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heal. The lid speculum is removed and the surface moistened before closing the lids and returning to the recipient eye.

Placement of the Donor Tissue

The recipient eye of the patient is reopened with placement of a speculum. One autograft is sutured at a time into its anatomically correct position (limbus to limbus) with multiple interrupted sutures. We recommend 10- 0 nylon over polyglactin (Vicryl) because it causes less postoperative inflammation. Some surgeons use a combination, with 10-0 nylon for the anterior corneal sutures

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and 9-0 Vicryl for the conjunctival sutures. The corners are secured first, and additional sutures are placed along the conjunctival portions to prevent postoperative dehiscence. The sutures are placed first through the conjunctival graft, then through the recipient episcleral tissue, and finally through the recipient conjunctiva. We cut nylon sutures on the knot and leave short tails with Vicryl sutures. Knots can be left unburied because the bites are short, and attempts to bury them often result in the sutures either breaking or being pulled out accidentally. During suturing, the autograft epithelium should be protected from desiccation and trauma with balanced salt solution and a viscoelastic (Figure 16.1D). Figure 16.2 demonstrates a series of clinical photographs of a patient with a conjunctival limbal autograft.

At the conclusion of the operation, an antibiotic-ste- roid ointment can be placed on the recipient eye and a drop of antibiotic-steroid solution placed on the donor eye. A patch and protective shield is placed over the recipient eye until the patient is seen the next day.

C.R. Croasdale, E.J. Holland, and M.J. Mannis

Postoperative Care

The donor eye is treated with the antibiotic-steroid drops 3 to 4 times daily until epithelization is complete (usually 1 to 2 weeks) and inflammation has subsided. A rare complication is the occurrence of a pyogenic granuloma at a graft donor site.

The recipient eye is treated with a low-toxicity antibiotic several times daily as prophylaxis during epithelization. In addition, nonpreserved artificial tears are used frequently while the patient is awake. Topical steroids are used 3 or 4 times daily for inflammation. It is important to avoid excessive use of preserved topical medications because preservative toxicity can damage the fragile new epithelium. If significant inflammation occurs in the immediate postoperative period, oral steroids should be considered.

Nylon sutures can be left in place for many months. Those that become loose or cause irritation should be removed, preferably after at least several weeks of healing. Vicryl sutures usually loosen over 3 to 4 weeks and require removal if they do not fall out on their own.

Adjunctive Use of Amniotic Membrane

There are insufficient data to determine whether the adjunctive use of amniotic membrane with CLAU increases the success of the procedure. Details on the applications of amniotic membrane are covered in Chapter 19.

Proposed advantages include reduced inflammation postoperatively and faster epithelization of conjunctival and corneal surfaces with their appropriate respective epithelial phenotypes. The end result of these processes should be a reduction in postoperative vascularization and scarring. In partial limbal SC deficiency, amniotic membrane may work by providing a more hospitable substrate environment for the healthy remaining limbal SC, thereby facilitating expansion and re-epithelization with normal corneal epithelium.12

Disadvantages to the use of amniotic membrane primarily include high cost and relative unavailability. Most surgeons need the tissue only infrequently and lack the resources and facilities to prepare it on their own.

If adjunctive amniotic membrane is available, it can be applied in several ways. On the donor eye it can be placed over the donor graft sites to facilitate faster epithelization with reduced inflammation and scarring. On the recipient eye it can be placed either over the areas of recessed conjunctiva alone, or as a single sheet over both the cornea and exposed sclera. When used only on the exposed sclera and not the cornea, its role is to act as a barrier against conjunctivalization of the cornea. When applied additionally over the cornea, it may facilitate improved epithelization, although in patients with better preoperative visual acuity, it can be expected that vision will be affected until the amniotic membrane absorbs over the first several months.

References

1.Jenkins C, Tuft S, Liu C, et al. Limbal transplantation in the management of chronic contact-lens-associated epitheliopathy. Eye 1993; 7:629–633.

2.Thoft RA. Conjunctival transplantation. Arch Ophthalmol 1977; 95:1425–1427.

3.Thoft RA. Indications for conjunctival transplantation. Ophthalmology 1982; 89:335–339.

4.Vastine DW, Stewart WB, Schwab IR. Reconstruction of the periocular mucous membrane by autologous conjunctival transplantation. Ophthalmology 1982; 89:1072–1081.

5.Holland EJ, Schwartz GS. The evolution of epithelial transplantation for severe ocular surface disease and a proposed classification system. Cornea 1996; 15:549–556.

6.Kwitko S, Marinho D, Barcaro S, et al. Allograft conjunctival transplantation for bilateral ocular surface disorders. Ophthalmology 1995; 102:1020–1025.

7.Kruse FE, Chen JJY, Tsai RJF, et al. Conjunctival transdifferentiation is due to incomplete removal of limbal basal epithelium. Invest Ophthalmol Vis Sci 1990; 31:1903–1913.

8.Tsai RJ-F, Sun T-T, Tseng SCG. Comparison of limbal and conjunctival autograft transplantation in corneal surface reconstruction in rabbits. Ophthalmology 1990; 97:446–55.

9.Kenyon KR, Tseng SCG. Limbal autograft transplantation for ocular surface disorders. Ophthalmology 1989; 96:709–723.

10.Chen JJY, Tseng SCG. Corneal epithelial wound healing in partial limbal deficiency. Invest Ophthalmol Vis Sci 1990; 31:1301–1314.

11.Chen JJY, Tseng SCG. Abnormal corneal epithelial wound healing in partial thickness removal of limbal epithelium.

Invest Ophthalmol Vis Sci 1991; 32:2219–2233.

12.Tseng SCG, Prabhasawat P, Barton K, et al. Amniotic membrane transplantation with or without limbal allografts for corneal surface reconstruction in patients with limbal stem cell deficiency. Arch Ophthalmol 1998; 116:431–441.