Use of nonpreserved human amniotic membrane for the reconstruction of the ocular surface

Update in the Diagnosis and Management of Ocular Surface Squamous Neoplasia (OSSN)

Ocular surface squamous neoplasia (OSSN) includes a variety of ocular surface tumors ranging from mild epithelial dysplasia to invasive squamous cell carcinoma. OSSN is one of the most frequent non-pigmented malignancies of the ocular surface. Debate persists between surgical excision and medical management concerning the optimal regimen for OSSN treatment, with surgical excision continuing to be the recognized standard of care in contemporary medicine. Medical and conservative therapy techniques have advanced significantly in recent years, leading to widespread use in everyday ophthalmology practice. This study aims to look into the efficacy of current treatment options for conjunctival squamous cell carcinoma and to evaluate the available evidence for the most up-to-date approach for the management of the disease.

Comparison of the effects of preservation methods on structural, biological, and mechanical properties of the human amniotic membrane for medical applications

Amniotic membrane (AM), the innermost layer of the placenta, is an exceptionally effective biomaterial with divers applications in clinical medicine. It possesses various biological functions, including scar reduction, anti-inflammatory properties, support for epithelialization, as well as anti-microbial, anti-fibrotic and angio-modulatory effects. Furthermore, its abundant availability, cost-effectiveness, and ethical acceptability make it a compelling biomaterial in the field of medicine. Given the potential unavailability of fresh tissue when needed, the preservation of AM is crucial to ensure a readily accessible and continuous supply for clinical use. However, preserving the properties of AM presents a significant challenge. Therefore, the establishment of standardized protocols for the collection and preservation of AM is vital to ensure optimal tissue quality and enhance patient safety. Various preservation methods, such as cryopreservation, lyophilization, and air-drying, have been employed over the years. However, identifying a preservation method that effectively safeguards AM properties remains an ongoing endeavor. This article aims to review and discuss different sterilization and preservation procedures for AM, as well as their impacts on its histological, physical, and biochemical characteristics.

Preserved Corneal Lamellar Grafting Reduces Inflammation and Promotes Wound Healing in a Scleral Defect Rabbit Model

Purpose

To investigate the effect of preserved corneal lamellar grafting on inflammation and wound healing and to compare its effect with that of preserved scleral grafting in a scleral defect rabbit model.

Methods

New Zealand White rabbits were assigned to a corneal lamellar grafting group (n = 5) or a scleral grafting group (n = 5). After lamellar dissection of superotemporal sclera using 6.0-mm trephine, the same sizes of preserved human corneal or scleral grafts were transplanted with 10-0 nylon interrupted sutures. The grafted areas were photodocumented at 3 to 21 days after surgery to evaluate epithelial wound healing index (%), neovascularization and presence of filaments. The existence of CD3⁺ T cells and CD34⁺ cells at the grafted areas was analyzed at 21 days.

Results

Epithelial wound healing index was significantly higher in the corneal grafting group at 9 days (P < 0.05). Scleral grafts showed copious formation of filaments adherent to the engrafted area from 9 to 14 days, whereas the corneal grafts were free of filaments. The numbers of inflammatory cells were significantly higher in the scleral grafts (P < 0.05), and CD3⁺ T cells and CD34⁺ cells were populated within inflammatory cells at graft-recipient junctions in both groups. The mean areas of the estimated perigraft and intragraft neovascularization tended to be higher in scleral grafts.

Conclusions

Preserved corneal lamellar grafting enhances epithelial wound healing and alleviates inflammation in a scleral defect rabbit model.

Translational Relevance

This work suggests that the preserved corneal graft may be considered as a favorable alternative option for repairing scleral defects.

Amniotic membrane, clinical applications and tissue engineering. Review of its ophthalmic use

The use of amniotic membrane in ophthalmology has been increasing in recent years due to its multiple biological and tectonic properties, improvement in the process of obtaining, ease of use, and advancement in tissue engineering. The amniotic membrane has become one of the main adjuvant treatments, in ophthalmic surgery as well as in other medical-surgical specialties. The development of tissue engineering has allowed it to be used, not only in its classic form, but also by the use of drops and other presentations. The different steps prior to its use (preparation and conservation), the different surgical techniques, and their main clinical applications are described throughout the article.

Treatment of acute ocular chemical burns

Ocular chemical burns are an ophthalmic emergency and are responsible for 11.5%-22.1% of ocular injuries. Immediate copious irrigation is universally recommended in acute ocular burns to remove the offending agent and minimize damage. Conventional medical therapy consists of the use of agents that promote epithelialization, minimize inflammation, and prevent cicatricial complications. Biological fluids such as autologous serum, umbilical cord blood serum, platelet-rich plasma, and amniotic membrane suspension are a rich source of growth factors and promote healing when used as adjuncts to conventional therapy. Surgical treatment of acute ocular burns includes the debridement of the necrotic tissue, application of tissue adhesives, tenoplasty, and tectonic keratoplasty. Amniotic membrane transplantation is a novel surgical treatment that is increasingly being used as an adjunct to conventional treatment to promote epithelial healing, minimize pain, and restore visual acuity. Various experimental treatments that aim to promote wound healing and minimize inflammation are being evaluated such as human mesenchymal and adipose stem cells, beta-1,3 glucan, angiotensin-converting enzyme inhibitors, cultivated fibroblasts, zinc desferrioxamine, antifibrinolytic agents, antioxidants, collagen cross-linking, and inhibitors of corneal neovascularization.

Comparison of impact of two decontamination solutions on the viability of the cells in human amnion

Human amniotic membrane (HAM) is used as an allograft in regenerative medicine or as a source of pluripotent cells for stem cell research. Various decontamination protocols and solutions are used to sterilize HAM before its application, but little is known about the toxicity of disinfectants on HAM cells. In this study, we tested two decontamination solutions, commercial (BASE·128) and laboratory decontamination solution (LDS), with an analogous content of antimycotic/antibiotics for their cytotoxic effect on HAM epithelial (EC) and mesenchymal stromal cells (MSC). HAM was processed in a standard way, placed on nitrocellulose scaffold, and decontaminated, following three protocols: (1) 6 h, 37 °C; (2) 24 h, room temperature; (3) 24 h, 4 °C. The viability of EC was assessed via trypan blue staining. The apoptotic cells were detected using terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL). The mean % (±SD) of dead EC (%DEC) from six fresh placentas was 12.9 ± 18.1. Decontamination increased %DEC compared to culture medium. Decontamination with BASE·128 for 6 h, 37 °C led to the highest EC viability (81.7%). Treatment with LDS at 24 h, 4 °C resulted in the lowest EC viability (55.9%) in the set. MSC were more affected by apoptosis than EC. Although the BASE·128 expresses lower toxicity compared to LDS, we present LDS as an alternative decontamination solution with a satisfactory preservation of cell viability. The basic formula of LDS will be optimised by enrichment with nutrient components, such as glucose or vitamins, to improve cell viability.

Repair of Experimental Plaque-Induced Periodontal Disease in Dogs

Forty mongrel dogs were used in this study for induction of periodontal disease by placing subgingival silk ligatures affecting maxillary and mandibular premolar teeth during a 12-month period. Experimental premolar teeth received monthly clinical, radiographic, and histometric/pathologic assessments. The results demonstrated significant increases in scores and values of periodontal disease parameters associated with variable degrees of alveolar bone loss. The experimental maxillary premolar teeth exhibited more severe and rapid rates of periodontal disease compared with mandibular premolar teeth. Histometric analysis showed significant reduction in free and attached gingiva of the experimental teeth. Histopathological examination of buccolingual sections from experimental premolar teeth showed the presence of rete pegs within the sulcular epithelium with acanthosis and erosive changes, widening of the periodontal ligament, and alveolar bone resorption. Various methods for periodontal repair were studied in 194 experimental premolar teeth exhibiting different degrees of periodontal disease. The treatment plan comprised non-surgical (teeth scaling, root planing, and oral hygiene) and surgical methods (closed gingival curettage, modified Widman flap, and reconstructive surgery using autogenous bone marrow graft and canine amniotic membrane). The initial non-surgical treatment resulted in a periodontal recovery rate of 37.6 % and was found effective for treatment of early periodontal disease based on resolution of gingivitis and reduction of periodontal probing depths. Surgical treatment by closed gingival curettage to eliminate the diseased pocket lining resulted in a recovery rate of 48.8 % and proved effective in substantially reducing deep periodontal pockets. Open root planing following flap elevation resulted in a recovery rate of 85.4 % and was effective for deep and refractory periodontal pockets. Autogenous bone graft implantation combined with canine amniotic membrane as a biodegradable membrane was used in 18 premolar teeth and failed to improve advanced furcation defects in most teeth.

Long-term efficacy of glycerine-processed amniotic membrane transplantation in patients with corneal ulcer

PURPOSE

The aim of this study was to determine the long-term treatment efficacy of glycerine-preserved human amniotic membrane transplantation in patients suffering from corneal ulcers.

METHODS

This was a retrospective, non-controlled, monocentric analysis. Included were patients with corneal ulcers that were non-responsive to ointment or contact lenses and had been treated by amniotic membrane transplantation with either the overlay or sandwich procedure. Analysis parameters were visual acuity before and following treatment, recurrence rate and subjective comfort at the last follow-up.

RESULTS

Of the 371 amniotic membrane transplantations that were conducted, 135 surgical treatments in 108 patients (51.9% male, 48.1% female; mean age 63.7 years) met the inclusion criteria. In total, 99 overlay and 36 multilayer amniotic membrane transplantations were performed. The follow-up period was 47.5 ± 66.7 weeks (mean ± SD). The recurrence rate at the last follow-up was 47.8% with overlay membranes and 51.8% with the sandwich technique. There was no significant change in best-corrected visual acuity following treatment with overlays (p = 0.219) or sandwich procedure (p = 0.703). At the last follow-up, 72.1% (overlay) and 78.3% (sandwich) of the patients reported either no pain or increased comfort.

CONCLUSION

The recurrence rates and changes in visual acuity following overlay or sandwich amniotic membrane transplantation in patients suffering from corneal ulcer were lower than reported elsewhere in the literature. More than half of the patients profited from each of the amniotic membrane transplantation techniques with respect to recurrence and postoperative comfort.

Amniotic membrane properties and current practice of amniotic membrane use in ophthalmology in Slovenia

Amniotic membrane (AM) is the innermost, multilayered part of the placenta. When harvested, processed and stored properly, its properties, stemming from AM biological composition, make it a useful tissue for ophthalmic surgery. AM was shown to have several beneficial effects: it promotes epithelization, has antimicrobial effects, decreases inflammation, fibrosis and neovascularization. Many case reports and case series as well as practical experience (e.g. reconstruction of conjunctival and corneal defects, treatment of corneal ulcers) demonstrated the beneficial effect of AM for different ophthalmological indications. The combination of the above mentioned beneficial effects and reasonable mechanical properties are also the reason why AM is used as a substrate for ex vivo expansion of epithelial progenitor cells. Recently, amnion-derived cells, which also have stem cell characteristics, have been proposed as potential contributors to cell-based treatment of ocular surface disease. However, the use of AM remains one of the least standardized methods in ophthalmic surgery. In this review, the various properties of AM and its current clinical use in ophthalmology in Slovenia are discussed.

The effects of preservation procedures on antibacterial property of amniotic membrane

Amniotic membrane (AM), the innermost layer of the fetal membranes, has been widely employed in the surgical reconstruction and tissue engineering. Expression of the antimicrobial peptides such as defensins, elafin and SLPI which are essential elements of the innate immune system results in antibacterial properties of the AM. Preservation is necessary to reach a ready-to-use source of the AM. However, these methods might change the properties of the AM. The aim of this study was to evaluate antibacterial properties of the AM after preservation. Antibacterial property of the fresh AM was compared with cryopreserved and freeze-dried AM by modified disk diffusion method. Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922 and two clinical isolated strains of E. coli were cultured in Mueller Hinton agar and a piece of the AM was placed on agar surface. After 24h incubation, the inhibition zone was measured. In addition, one of the most important antibacterial peptides, elafin, was measured by ELISA assay before and after preservations procedures. Antibacterial properties of the AM were maintained after cryopreservation and freeze-drying. However, the inhibition zone was depending on the bacterial strains. The cryopreservation and freeze-drying procedures significantly decreased elafin which shows that antibacterial property is not limited to the effects of amniotic cells and the other components such as extracellular matrix may contribute in antibacterial effects. The promising results of this study show that the preserved AM is a proper substitute of the fresh AM to be employed in clinical situations.

Current concepts of ocular adnexal surgery

Ophthalmic Plastic and Reconstructive Surgery is a specialized area of ophthalmology that deals with the management of deformities and abnormalities of the eyelids, lacrimal system and the orbit. An ophthalmoplastic surgeon is able to identify and correct abnormalities of the ocular adnexae such as ectropion, lid retraction, conjunctival scarring with severe entropion, that can cause secondary ocular surface disorders; manage patients with watering eye, and when needed intervene with a dacryocystorhinostomy by external or endonasal approach and moreover minimize disfigurement following enucleation or evisceration and prevent further corneal damage, alleviate complains of tearing and grittiness, but also cosmetic complaints in patients with Graves' orbitopathy. Aim of this manuscript was to review current established and recently evolving surgical procedures.

Adnexal Surgery for Severe Ocular Surface Disease

Secondary causes of ocular surface disease are-to a large extent-due to disorders of the ocular adnexae. The main pathomechanisms involved include exposure, abrasion and malnutrition, resulting from a multitude of disorders such as ec- or entropion (e.g. in cicatrizing conjunctivitis), lid retraction and severe aqueous deficiency. In the presence of these problems, surgical attempts of ocular surface reconstruction frequently fail. Here we review established and evolving new techniques in the field of adnexal surgery to specifically address these problems.

Current Concepts in Ocular Surface Reconstruction

Diseases that affect the limbal stem cells are multifactorial and present with different stages of severity. The most important features to be considered in evaluating these patients include the degree of limbal stem cell loss, the extent of conjunctival disease, and the presence and etiology of ocular surface inflammation. Other important factors are tear film and eyelid abnormalities, keratinization of the ocular surface, laterality of the disease process, health and age of the patient. Careful consideration of all of these factors help tremendously in tailoring the most suitable method of treatment for each patient. The management of severe ocular surface disease has benefited from numerous advances in recent years. At one time, available techniques for visual rehabilitation consisted of superficial keratectomy, use of artificial tears, tarsorraphy as well as lamellar and penetrating keratoplasty. A lamellar or penetrating keratoplasty procedure resulted in a stable surface only for as long as the donor epithelium was present and once the epithelium sloughed off, the ocular surface failed due to conjunctivalization. The last few decades enjoyed the development and, especially, progress of new ocular surface reconstruction techniques such as amniotic membrane transplantation, limbal stem cell transplant procedures, transplantation of cultivated oral mucosal or limbal stem cell sheets. This review will briefly focus on the indications and methodology of each procedure and the currently available clinical data on the results of these procedures.

In vivo laser confocal microscopy findings of cryopreserved and fresh human amniotic membrane

BACKGROUND AND OBJECTIVE

Recently, the cornea-specific in vivo laser confocal microscope has become available. The objective of the current study was to obtain laser confocal images of fresh and cryopreserved human amniotic membrane.

MATERIALS AND METHODS

Fresh and cryopreserved amniotic membranes from different donors were examined using the in vivo laser scanning confocal microscope (Heidelberg Retina Tomograph II Rostock Cornea Module [HRT II-RCM]; Heidelberg Engineering GmbH, Dossenheim, Germany).

RESULTS

In all samples of both fresh and cryopreserved amniotic membranes, the HRT II-RCM resolved four distinct layers: the epithelium, a basement membrane, a cell-rich stromal layer (fibroblast layer), and a spongy stromal layer. In a posterior aspect of the basement membrane layer (facing the fibroblast layer), microfolds were more prominent in fresh amniotic membranes than in cryopreserved amniotic membranes. For the cell-rich stromal layer, mesenchymal cells were observed more distinctively in fresh amniotic membranes than in cryopreserved amniotic membranes.

CONCLUSION

These baseline laser confocal images can be used for future investigation of in vivo remodeling after amniotic membrane transplantation.

Autologous amnion graft for repair of myelomeningocele: technical note and clinical implication

OBJECTIVE AND IMPORTANCE

Amniotic membrane can be used as autologous reconstruction graft material when aseptically obtained. We introduce here a novel repair technique using autologous amnion graft, and report a case presentation of myelomeningocele successfully treated with this graft material.

TECHNIQUE

Amniotic membrane, which was composed of amnion and chorion, was aseptically harvested at cesarean section. Removing chorionic tissue, amnion containing monolayer of amniotic epithelial cells and underlining fibrous tissue was isolated. After the procedure of reconstruction of neural and meningeal elements, the membrane was placed as onlay autograft over the reconstructed neural structure followed by suture of undermined skin flap without any myocutaneous flap transfer technique or fascial transposition from paraspinal muscles.

RESULTS

The postoperative healing process of the wound was excellent.

CONCLUSION

Autograft of amniotic tissue has no risks of rejection, foreign body reaction, or transmission of slow virus infection to reconstruct the lesion of newborn patient. Amnion autograft would be a biologic rationale to promote wound healing, being applied as a part of a variety of pediatric neurosurgical procedure.

Transplante de membrana amniótica canina criopreservada para cicatrização de córnea com deficiência de células límbicas em coelhos

Avaliaram-se as alterações relacionadas à deficiência das células límbicas precursoras do epitélio corneano de coelhos e o efeito da membrana amniótica sobre sua cicatrização. A lesão, induzida com n-heptanol associado à peritomia conjuntival em 360°, foi recoberta com membrana amniótica canina, suturada à episclera perilímbica, criopreservada em meio para congelação de embrião ou em meio próprio, ambos com glicerol a 50% e mantida a -80°C. O grupo-controle não foi tratado com a membrana. As avaliações histológicas foram realizadas ao sétimo, 15º e 30º dias. Todos desenvolveram deficiência de células germinativas do limbo, denominada conjuntivalização, com presença de neovascularização, inflamação e defeitos epiteliais recorrentes, caracterizada na histopatologia pela presença de neovasos, edema, leucócitos e células caliciformes. O transplante de membrana amniótica não foi eficiente para o tratamento desta deficiência, entretanto auxiliou o processo de cicatrização da córnea.

Management of Primary Pterygia Using Free Conjunctival and Limbal-Conjunctival Autografts Without Antimetabolites

PURPOSE

To report the incidence of recurrence after primary pterygium surgery using either a free conjunctival or limbal-conjunctival autograft without antimetabolites.

METHODS

One hundred eleven eyes of 90 patients underwent pterygium resection; a free conjunctival autograft was used in 88 surgeries and a free limbal-conjunctival autograft in 24; the latter technique was reserved for dark-skinned patients, under age 30, and with a history of recurrent pterygium in the contralateral eye.

RESULTS

Mean age was 42.5 years (range, 23-75), and 50% of the patients were male. Mean follow-up was 9 months (range, 3-12). There were 2 recurrences (1.8%), both observed in the third postoperative month.

CONCLUSIONS

With a good surgical technique, the incidence of recurrence after primary pterygium surgery is very low, making the use of antimetabolites unnecessary.

Fibrin sealant in corneal stem cell transplantation

PURPOSE

To determine if transplanted corneal epithelial stem cells are safely and efficiently attached to the deficient limbal niche with use of fibrin sealant. The primary outcome is measured with respect to the stability of the transplant, with secondary qualitative evaluations of inflammation, patient comfort, speed of operation, and incidence of complications.

METHODS

This retrospective case study examined a total of 114 corneal stem cell reconstructions performed in 95 patients from 1996 to 2004 using corneal stem cells primarily, with a minority of amnion alone, or both. Fibrin sealant was used as the only technique of stem cell adhesion for limbal reconstruction for primary or recurrent pterygia and various stem cell-deficient diseases from 2000 to 2004.

RESULTS

The fibrin sealant group showed 1 small recurrence of pterygium but no complications. With sutures, there were 3 recurrences in the pterygia group. After completion of all surgical procedures, all patients were free of pterygia. Miscellaneous stem cell deficiencies were included to demonstrate that corneal stem cell transplants can be used in other corneal procedures in addition to pterygia.

CONCLUSIONS

Fibrin sealant alone effectively and safely attached corneal stem cell transplants to the limbal niche. The additional qualitative observations of a reduction in operation time, postoperative pain, and inflammation augurs for more extensive use of fibrin sealants in ophthalmology.

Amniotic Membrane Transplantation for Ocular Surface Reconstruction

The amniotic membrane, composed of 3 layers, the epithelium, basement membrane, and the stroma, was first used along with the chorion as a biologic membrane to promote healing of skin burns in 1910. In ophthalmology, it was used in 1940 in the management of conjunctival defects. Its revival in the 1990s was due to its ability to reduce ocular surface inflammation and scarring, promote rapid epithelialization due to the presence of growth factors, and antimicrobial properties. This has resulted in its application in several ocular disorders. A review of the literature shows that amniotic membrane is definitely beneficial in some but not all pathology. The future of amniotic membrane transplantation is very exciting, especially in the field of limbal stem cell research. However, further work is needed to elucidate whether it functions merely as a biologic contact lens or whether it has additional benefits.

Nonpreserved human amniotic membrane transplantation for conjunctival reconstruction after excision of extensive ocular surface neoplasia

PURPOSE

To report our experience on the use of nonpreserved human amniotic membrane transplantation (AMT) in ocular surface reconstruction after excision of extensive ocular surface neoplasia (OSN).

DESIGN

Prospective noncomparative interventional case series.

PARTICIPANTS

In all, 10 eyes of 10 consecutive patients with extensive OSN involving various areas of limbus, conjunctiva, and cornea (conjunctival carcinoma in situ, four eyes; squamous cell carcinoma, three eyes; malignant melanoma, two eyes; conjunctival-orbital lymphangioma, one eye) were included in this prospective noncomparative interventional case series. After excision of the neoplasia with 3-4 mm tumour-free margins, double freeze-thaw cryotherapy was applied to the margins of the remaining conjunctiva, and nonpreserved human amniotic membrane graft was sutured to the adjacent conjunctiva using 8/0 vicryl sutures and cornea using 10/0 nylon sutures, with the epithelial side facing up to cover the bare sclera and cornea. Postoperatively, topical corticosteroids were used for 3 months.

RESULTS

After tumour excision and AMT, a satisfactory result with a wet, stable conjunctiva, and rapid and complete healing was observed in all eyes. Over a mean follow-up of 10.0 months (range, 6-27 months), all but one eye remained free of tumour recurrence. In one eye with conjunctival melanoma, there was a small recurrence, which was treated with excision and cryotherapy. Treatment complications were partial stem cell deficiency in two eyes and symblepharon formation in one eye. Immune graft rejection was not encountered.

CONCLUSION

Nonpreserved human AMT appears to be useful for reconstruction of ocular surface following excision of extensive OSN.

Amniotic Membrane Transplantation in the Management of Severe Ocular Surface Disease: Indications and Outcomes

Since 1995, with the availability of cryopreserved amniotic membrane (AM), the use of AM as a patch or graft for ocular surface reconstruction has become recognized as an important alternative for treatment of persistent epithelial defects and sterile ulceration that are refractory to conventional therapy. A major problem with evaluating the efficacy of AM transplantation is the lack of controlled clinical studies. Moreover, for some diseases there is no accepted "standard" therapy, and the incidence of the disease is too low to allow proper randomization. In this review, we have attempted to assess the indications and outcomes of AM transplantation based on 661 cases reported in the peer-reviewed literature. Successful outcome was defined as the healing of an epithelial defect (corneal or conjunctival) over a specified time period and the lack of induced motility disturbance.

The amniotic membrane in ophthalmology

The amniotic membrane is the innermost of the three layers forming the fetal membranes. It was first used in 1910 in skin transplantation. Thereafter it has been used in surgical procedures related to the genito-urinary tract, skin, brain, and head and neck, among others. The first documented ophthalmological application was in the 1940s when it was used in the treatment of ocular burns. Following initial reports, its use in ocular surgery abated until recently when it was re-discovered in the Soviet Union and South America. Its introduction to North America in the early 1990s heralded a massive surge in the ophthalmic applications of this membrane. The reintroduction of amniotic membrane in ophthalmic surgery holds great promise; however, although it has been shown to be a useful and viable alternative for some conditions, it is currently being used far in excess of its true useful potential. In many clinical situations it offers an alternative to existing management options without any distinct advantage over the others. Further studies will undoubtedly reveal the true potential of the membrane, its mechanism(s) of action, and the effective use of this tissue in ophthalmology.

Ocular surface reconstruction update

Ocular surface reconstruction (OSR) is now a standard procedure in the treatment of severe ocular surface disorders. The past few years have revealed the long-term results of patients who were operated on during the early stages of OSR development, and we now have a more realistic view of the benefits and limits of the procedure. On the other hand, further understanding of the physiologic role played by the amniotic membrane (AM) has opened doors to further refined techniques in treating these patients. This review will introduce some of the major contributions made during the past years in the advancement of OSR. Clinically, we are at a stage of reviewing the pros and cons of the various transplantation techniques. Identification of factors crucial for a successful OSR procedure will further improve surgical results. Basic researchers are on the verge of identifying the so-called limbal stem cells, and further understanding of AM physiology will lead the way to tissue engineering techniques as another alternative in OSR surgery.

Histopathology of human corneas after amniotic membrane and limbal stem cell transplantation for severe chemical burn

PURPOSE

To describe the histopathologic changes in the cornea following amniotic membrane transplantation (AMT) combined with limbal transplantation.

METHODS

Four eyes with complete limbal stem cell deficiency after severe chemical burn underwent AMT with either a living-related conjunctival limbal allograft (lr-CLAL) (three eyes) or a conjunctival limbal autograft (CLAU) (one eye) for ocular surface reconstruction. Penetrating keratoplasty was performed several months after the initial procedure for further visual rehabilitation. Mean follow up time was 20 months. Light and transmission electron microscopy (TEM) and indirect immunofluorescence microscopy of the excised corneal buttons were performed.

RESULTS

All specimens displayed a multilayered epithelium without conjunctival goblet cells over the entire corneal surface. Basal epithelial cells demonstrated a firm connection to the remnants of the transplanted amniotic membrane (AM), which at some places appeared to be in a state of "modification" or "remodeling" in the collagen layers. The basement membrane zone displayed a positive staining when using antibodies against collagen IV and VII, integrin alpha6 and beta4, laminin 5, and bullous pemphigoid antigen 2. Remnants of the AM in the specimen showed staining of collagen IV, which was found also in cross-sections of cryopreserved AM. The recipients Bowman's membranes that were only partially present after the initial trauma were significantly disturbed.

CONCLUSION

Within the time frame studied, the transplanted AM apparently survives and integrates into the host tissue being modified or remodeled by recipient cells. AMT in combination with a CLAU or lr-CLAL is a useful technique in promoting a rapid and stable reepithelialization of a corneal surface following severe chemical or thermal damage.

Nonpreserved human amniotic membrane transplantation in acute and chronic chemical eye injuries

PURPOSE

To evaluate the safety and efficacy of nonpreserved amniotic membrane transplantation (AMT) with or without limbal autograft transplantation (LAT) in management of acute and chronic chemical eye injuries.

METHODS

Amniotic membrane transplantation or AMT + LAT was performed on nine eyes of seven consecutive patients, five eyes with acute chemical burn and four eyes with limbal stem cell deficiency secondary to previous chemical burn. Nonpreserved amniotic membrane was used in all procedures.

RESULTS

Five patients (71.5%) were men and two (28.5%) were women. The average age at the time of surgery was 32.7 +/- 10.9 years (range, 20-45). Mean follow-up after last surgery was 8.9 +/- 3.2 months (range, 6-14). The average epithelial healing time was 24.6 +/- 17.3 days (range, 3-45). At the end of the follow-up period, visual acuity improved in all eyes, inflammation subsided, and the subjective complaints decreased remarkably.

CONCLUSION

AMT with nonpreserved amniotic membrane promoted epithelial healing, reduced surface inflammation, increased patient comfort, and decreased the extent and severity of vascularization when used in patients with acute chemical burns. When used in limbal stem cell deficiency owing to past chemical burns, AMT alone or in combination with LAT aided in ocular surface reconstruction. Infectious, inflammatory, or toxic/allergic reactions were not encountered in any patient owing to the use of nonpreserved amniotic membrane. Further studies are required to establish the safety and efficacy of preserved and nonpreserved AMT in ocular surface reconstruction.

Amniotic membrane surgery

Human amniotic membrane (AM) is composed of three layers: a single epithelial layer, a thick basement membrane, and an avascular stroma. Amniotic membrane has anti-adhesive properties and is felt to promote epithelialization and decrease inflammation, neovascularization, and fibrosis. Amniotic membrane transplantation (AMT) is currently being used for a continuously widening spectrum of ophthalmic indications. Amniotic membrane transplantation has been shown to be effective in the reconstruction of the corneal surface in the setting of persistent epithelial defects, sterile corneal ulcerations, and partial limbal stem cell (LSC) deficiency states, including those secondary to chemical or thermal burns. Amniotic membrane transplantation also has been used in conjunction with limbal stem cell transplantation (LSCT) both in a concurrent fashion as well as in preparation for LSCT. Amniotic membrane transplantation also has been used in place of conjunctival autografting after pterygium excision and to reconstruct the conjunctival surface after removal of conjunctival lesions. Most recently, ex vivo cultivation and expansion of limbal epithelial cells has been performed utilizing AM as a matrix. However, the superiority of AMT over other treatment modalities in many of these settings needs to be substantiated by controlled clinical trials.