Histologic findings after amniotic membrane graft in the human cornea

Allogeneic anterior lens capsule transplantation (ALCT) for the management of HSV neurotrophic keratitis

Purpose

To report a case of allogeneic anterior lens capsule transplantation (ALCT) for the management of HSV neurotrophic epithelial keratitis.

Observations

An 81-year-old man was referred to our department due to neurotrophic keratitis in the left eye that he had been suffering from over the past 3 months. He had recurrent episodes of HSV keratitis in the left eye over the past 3 years and despite multiple previous treatments, there was no improvement. At the time of presentation, corrected distance visual acuity (CDVA) was 20/200 in the right eye and no light perception (NLP) in the left eye. Slit-lamp examination revealed a corneal epithelial defect with underlying stromal thinning and concomitant scarring. An allogeneic anterior lens capsule (ALC) was placed over the epithelial defect to act as a biological dressing, anchored with a droplet of fibrin glue. A bandage contact lens (BCL) was placed over to prevent the slippage of the ALC. No intra or postoperative complications were observed. Two weeks later, the ALC was removed revealing complete epithelial healing, while two months later the epithelium remained completely healed with a significant reduction of corneal scarring.

Conclusions and importance

Anterior Lens Capsule transplantation (ALCT) seems to be a promising new treatment option for the management of corneal neurotrophic keratitis.

Tenons Patch Graft: A Review of Indications, Surgical Technique, Outcomes and Complications

PURPOSE

Corneal perforations are common corneal emergencies faced by ophthalmologists across the globe. There are multiple modalities of management, most of which require an eye bank support or availability of tissue adhesives. Tenons patch graft (TPG) is a technique that does not depend on these factors as the graft is harvested from the same eye of the patient. The aim of this review is to provide an overview of the indications, technique, normal postoperative course, and management of complications.

METHODS

After carrying out a literature search on "tenons capsule", "corneal patch graft", "tenons patch graft", "multilayered amniotic membrane" and "corneal perforations", 28 articles were included for this review.

RESULTS

TPG graft can be performed in cases of small to moderate perforations without active suppuration. The procedure can also be combined with amniotic membrane grafting or tissue adhesives to provide additional tectonic support. Postoperatively, the epithelium heals over a course 2-3 weeks and restoration of a stable ocular surface with a corneal scar is completed by the third postoperative month. Complications following the surgical procedure are rare but can include graft displacement, melt and pseudoectasia. Subsequent visual rehabilitation with contact lenses or keratoplasties can be planned in these eyes that yields good visual outcomes.

CONCLUSIONS

Tenons patch graft is a simple yet viable option in management of small to moderate corneal perforations. The procedure does not necessitate the prior availability of specialized products and can be performed with routine equipment of an ophthalmic theatre, making it an attractive option in low resource settings.

Superior limbic keratoconjunctivitis: a comprehensive review

Superior limbic keratoconjunctivitis (SLK) is characterized by chronic inflammation of the superior limbus and superior bulbar and tarsal conjunctivae. Patients also often have fine punctate staining of the limbus and adjacent area, superior limbic proliferation seen as thickening of the limbal epithelium and surrounding conjunctiva, and occasionally filaments at the superior limbus and upper cornea. SLK frequently presents with ocular irritation, foreign body sensation, and photophobia. SLK can be associated with other ocular and non-ocular conditions, such as thyroid disease. Although the pathogenesis of SLK is still unknown, it is thought to be related to mechanical injury, tear film instability, or an autoimmune/inflammatory etiology. Many patients with SLK can be asymptomatic or have symptoms that resolve or remit spontaneously. For symptomatic SLK, patients are managed medically with treatments such as lubricants, topical anti-inflammatory or immunomodulatory medications, punctal occlusion, and bandage contact lenses. Patients with symptoms refractory to medical management may need surgical interventions. We detail the current literature on the epidemiology, clinical manifestations, associated conditions, histopathology, pathogenesis, and treatment of SLK.

[Wound healing following amniotic membrane, limbal stem cell and corneal transplantation]

Knowledge of wound healing processes involved in amniotic membrane, limbal stem cell and corneal transplantation enables an assessment of clinical findings and a targeted treatment. The amniotic membrane serves as a basal membrane substrate or temporary transplant in corneal epithelial wound healing. It has an anti-inflammatory effect, supports corneal wound healing and counteracts scar formation. Amniotic membranes are integrated intraepithelially, subepithelially, or intrastromally in the course of healing. Limbal epithelial stem cells express multiple genes necessary for corneal wound healing. The rho-associated, coiled-coil containing protein kinase (ROCK) inhibitor Y‑27632 can improve the proliferation of limbal epithelial cells and therefore represents a new therapeutic option for limbal stem cell deficiency. Wound healing following penetrating keratoplasty involves fibroblasts, type III and IV collagens, proteoglycans, and chondroitin-6-sulfate. A certain inflammatory reaction seems to be necessary for final corneal wound closure.

Amniotic membrane transplantation for managing dry eye and neurotrophic keratitis

Neurotrophic keratitis (NK), a degenerative disease caused by damage to the trigeminal nerve, abolishes both tearing and blinking reflexes, thus causing the most severe forms of dry eye disease (DED). Conversely, the increasing severity of DED also leads to progressive loss of corneal nerve density, potentially resulting in NK. Both diseases manifest the same spectrum of corneal pathologies including inflammation and corneal epithelial keratitis, which can progress into vision-threatening epithelial defect and stromal ulceration. This review summarizes the current literature regarding outcomes following sutured and sutureless cryopreserved amniotic membrane (AM) in treating DED as well as epithelial defects and corneal ulcers due to underlying NK. These studies collectively support the safety and effectiveness of cryopreserved AM in restoring corneal epithelial health, improving visual acuity in eyes with NK and DED, and alleviating symptomatic DED. Future randomized controlled trials are warranted to validate the above findings and determine whether such clinical efficacy lies in promoting corneal nerve regeneration.

Histological Equivalence of a Hyper-Dry Amniotic Membrane and the Ambio2TM after Implantation in the Rabbit Conjunctiva

PURPOSE

A hyper-dry amniotic membrane (HDAM) has been used clinically for ocular surface reconstruction, but sufficient evidence of the histological dynamics and long-term safety have not been obtained. We examined the histological changes in an HDAM after its subconjunctival implantation in rabbit eyes, and we compared these changes to those in the Ambio2TM Amniotic Membrane Graft (IOP Ophthalmics, Costa Mesa, CA, USA) after the same surgery.

DESIGN

A prospective controlled animal study.

METHODS

We used 27 rabbits in two groups: the HDAM group (36 eyes of 18 rabbits) and the Ambio2 group (18 eyes of 9 rabbits). The HDAM or Ambio2 was transplanted on the bare sclera and covered with a conjunctival autograft. The histological changes were determined by evaluating the amniotic membrane graft, inflammatory cells, and foreign body granulomas in hematoxylin/eosin-stained sections at 30 days, 93 days, and 184 days postoperatively.

RESULTS

In all cases, the amniotic membrane graft was completely absorbed without scarring at 184 days postoperatively. The positive rate of inflammatory cells was significantly higher in the HDAM group compared to the Ambio2 group at 30 days postoperatively. The positive rate of foreign body granulomas decreased with time, with no significant difference between the two groups.

CONCLUSIONS

Both the HDAM and Ambio2 were completely absorbed without scarring within 6 months after surgery. The two types of membranes showed histologically equivalent responses. Translational Relevance: Since the HDAM was completely absorbed without scarring within 6 months after surgery, we could confirm its long-term safety.

Effectiveness of Cryopreserved Amniotic Membrane Transplantation in Corneal Ulceration: A Meta-Analysis

PURPOSE

To evaluate the effectiveness of cryopreserved amniotic membrane transplantation (AMT) in corneal ulceration.

METHODS

The following electronic databases were searched: PubMed, EMBASE, and Cochrane Library. We evaluated the corneal epithelium healing rate (CEHR) and vision improvement rate (VIR) after AMT in the treatment of corneal ulceration. We analyzed the differences in the CEHR and VIR between the 2 groups of infective and noninfective corneal ulcerations. Subgroup analysis for the CEHR and VIR was performed based on the surgical methods. There were 3 subgroups: single-layered inlay, multilayered inlay, and sandwich (SAN). The differences were tested by referring to the Cochrane Handbook. Pooled estimates were determined with STATA software, version 15.

RESULTS

Eighteen eligible studies reporting the outcomes in 390 eyes of 385 patients were included. The results of the meta-analysis showed that the pooled CEHR was 97% (I = 37.9%, 95% confidence interval: 0.94-0.99, P = 0.089). The pooled VIR was 53% (I = 68.1%, 95% confidence interval: 0.42-0.65, P < 0.001). There were no significant differences in either the CEHR or the VIR between the 2 groups of infective and noninfective corneal ulcerations. Among the 3 subgroups of single-layered inlay, multilayered inlay, and SAN, the differences in both CEHR and VIR were statistically significant.

CONCLUSIONS

Consistent with many published reports, this meta-analysis also concluded that AMT was effective in the treatment of corneal ulceration. The curative effect of AMT was not different between the infective and noninfective corneal ulcerations. The differences in both CEHR and VIR were statistically significant among the subgroups.

Superficial Keratectomy and Amniotic Membrane Patch in the Treatment of Corneal Plaque of Vernal Keratoconjunctivitis

Purpose

To report the importance of early surgical treatment of corneal ulcers associated with vernal keratoconjunctivitis (VKC) which may potentially produce severe lesions and permanent visual sequelae.

Methods

The authors present the case of a child with corneal ulcer in plaque who did not respond to medical treatment and had a good response to surgical treatment.

Results

A superficial keratectomy with an amniotic membrane patch was performed. A rapid postoperative epithelialization with a final good visual acuity was achieved.

Conclusions

Although amniotic membrane grafts following keratectomy have been described as a successful treatment in deep ulcers, in cases with slight stromal thinning, the amniotic membrane patch may be enough to achieve epithelialization. This procedure avoids the presence of the remains of membrane under the epithelium, which may affect postoperative corneal transparency.

Reconstruction of Conjunctiva with Amniotic Membrane after Excision of Large Conjunctival Melanoma: A Long-Term Study

Purpose

To evaluate, on a long- term basis, the role of amniotic membrane in the reconstruction of large conjunctival defects after excision of large conjunctival melanoma.

Methods

Four consecutive patients with diffuse conjunctival melanoma involving both bulbar and palpebral conjunctiva were studied. Conjunctival melanoma was completely excised (with wide clinically disease-free margins) and amniotic membrane immediately sutured to the surrounding conjunctiva and sclera to cover the conjunctival defect. Minimum follow-up was 48 months.

Results

Successful conjunctival surface reconstruction and physiologic fornical depth were achieved in all patients within 6 weeks. No recurrence of primary melanoma was observed during long-term follow-up.

Conclusions

Amniotic membrane transplantation is an effective alternative in ocular surface repairing surgery after removal of large conjunctival tumors.

Amniotic Membrane Transplantation for the Treatment of Infectious Ulcerative Keratitis Before Elective Penetrating Keratoplasty

PURPOSE

Emergency keratoplasties for inflamed eyes are considered to have a worse prognosis because of immunologic graft rejection. Amniotic membranes have antiinflammatory and antiangiogenic abilities. Therefore, amniotic membrane transplantation (AMT) was performed to stabilize the situation of eyes with severe infectious keratitis before elective penetrating keratoplasty (PK).

METHODS

Retrospective, nonrandomized observational case series. Seven to 41 days (median, 20 days) after the onset of intensive antiinfectious medication, an AMT (6 multigrafts and 6 sandwich) was performed in 12 patients [8 men and 4 women; age 46-80 years (median, 66 years)] with herpetic (n = 5), bacterial keratitis (n = 3), or combinations (n = 4). Three to 12 months (median, 5 months) after cessation of the inflammatory status of the eye, a central elective PK (diameter, 7-8 mm) became feasible in 10 eyes. Follow-up ranged from 4 to 38 months (median, 20 months) after PK.

RESULTS

The primary success rate of AMT was 11/12 (92%). Five recurrences (41%) were treated successfully 4 times by repeat AMT (sandwich) and 1 time by emergency PK. In 2 of the 12 eyes, an irreversible endothelial immunologic graft reaction appeared 18 and 21 months after PK. One eye suffered from reversible recurrence of herpetic keratitis on the corneal graft. At the end of the follow-up, 10 of 12 grafts (83%) were clear.

CONCLUSIONS

A rapid decrease in the inflammatory reaction and a fast reepithelialization because of AMT after intensive antiinfectious medication in case of severe ulcerative keratitis may help to avoid an emergency keratoplasty and improves the prognosis of the elective keratoplasty.

Postoperative changes in amniotic membrane as a carrier for allogeneic cultured limbal epithelial transplantation

PURPOSE

To investigate the morphologic changes and outcomes of the amniotic membrane as a carrier for allogeneic cultivated limbal epithelial transplantation.

DESIGN

Prospective, noncomparative, interventional study.

METHODS

A total of 16 eyes receiving allogeneic cultivated limbal epithelial transplantation with amniotic membrane as a carrier were enrolled. Morphologic changes in the amniotic membrane were observed by confocal microscopy and RTVue optical coherence tomography. The paired t test was employed to compare the mean best corrected visual acuity (BCVA) and corneal stromal thickness.

RESULTS

Of the 16 eyes, 12 had stable ocular surfaces (group A), while the other 4 eyes had failed surgeries due to immune rejection (group B). Confocal microscopy showed residual amniotic membrane tissues in 8 eyes in group A at 1 year. However, the amniotic membrane was not detected in group B at 8-10 months. RTVue optical coherence tomography showed discontinuous amniotic membrane tissues in all eyes in group A at 1 year, while highly reflective opacity was seen in the corneal stroma in group B. There were no statistically significant differences in mean BCVA and corneal stromal thickness in group A at 1 month and 1 year after transplantation (P > 0.05), but the mean BCVA showed a statistically significant difference at 1 month and after the disappearance of the amniotic membrane in group B (P < 0.05).

CONCLUSIONS

For eyes with stable ocular surfaces after cultivated limbal epithelial transplantation, the amniotic membrane can be present in the cornea for at least 1 year, with no impact on visual acuity or corneal stromal thickness. Chronic inflammation and neovascularization on the ocular surface may accelerate the disappearance of the amniotic membrane.

"Swiss roll" amniotic membrane technique for the management of corneal perforations

PURPOSE

To describe a novel technique for using amniotic membrane in the management of corneal perforations.

METHODS

Interrupted 10-0 nylon sutures are passed across the perforation site. A roll of amniotic membrane is then placed across the row of preplaced sutures, and the sutures are tied to secure the membrane. An amniotic membrane patch is placed over the graft, which is then protected by a bandage contact lens.

RESULTS

We illustrate the results of our 2 most recent patients.

CONCLUSIONS

Amniotic membrane has been widely used in ocular surgery. We recommend the "Swiss roll" amniotic membrane graft technique in cases of severe corneal thinning or localized perforations.

In vivo analysis of stromal integration of multilayer amniotic membrane transplantation in corneal ulcers

PURPOSE

To evaluate integration of amniotic membrane into the corneal stroma using laser scanning in vivo confocal microscopy and anterior segment optical coherence tomography (AS-OCT).

DESIGN

Prospective noncomparative interventional case series.

METHODS

Twenty-two eyes of 22 consecutive patients (mean age 53.9 ± 9.2 years) presenting with noninfectious corneal ulcers and stromal thinning unresponsive to medical treatment were enrolled. Multiple layers of amniotic membrane were applied over the ulcer bed to fill the ulcer crater and held in place with an overlying amniotic membrane patch, which was anchored to the surrounding cornea with 10-0 nylon interrupted sutures. Outcome measures were healing of the corneal ulcers, corneal morphology and stromal thickness changes at the ulcer site as measured by AS-OCT and surface epithelialization, stromal repopulation, and structural modifications of the amniotic membrane grafts as evaluated by confocal microscopy.

RESULTS

Follow-up extended to 12 months. Successful result was observed in 20 of 22 eyes (90.9%). AS-OCT showed that the mean residual stromal thickness at the ulcer bed was 222 ± 70 μm before surgery. The mean thickness of amniotic membrane layers at the same site was 394 ± 80 μm while the mean total corneal thickness was 623 ± 51 μm at day 1 post surgery. Thereafter a progressive reduction in thickness to 420 ± 61 μm at 6 months occurred, after which the thickness stabilized. Confocal microscopy showed that integration of the amniotic membrane tissues with corneal stroma was preceded by epithelialization over the amniotic membrane covering the ulcer. This occurred 15 ± 5 days post surgery in the successful cases. Confocal microscopy also showed that the amniotic membrane patch was degraded during the first few weeks after surgery, while the integrated amniotic tissues underwent progressive modifications characterized by early loss of amniotic epithelial cells, changes in fibrillar structure, and migration into the amniotic stroma by corneal stroma-derived cells.

CONCLUSIONS

Multiple layers of amniotic membrane can integrate into the corneal stroma with resulting increase in corneal thickness. This appears to be related to re-epithelialization of the transplanted membrane. Integrated amnion within the stromal defect undergoes progressive changes including contraction of tissue and repopulation by corneal stroma-derived cells.

New insights into the diagnosis and treatment of neurotrophic keratopathy

Abnormalities of the ocular surface can be acquired or inherited disorders of the central nervous system. Loss of neural stimulation from the sensory division of the trigeminal nerve or from the autonomic nervous system can have devastating consequences on corneal epithelial wound healing and the precorneal tear film, leading to decreased vision. The pathogenesis of neurotrophic keratopathy is reviewed, and treatment modalities are recommended.

Rate of epithelialisation and re-operations in corneal ulcers treated with amniotic membrane transplantation combined with botulinum toxin-induced ptosis

OBJECTIVE

To examine the efficacy of amniotic membrane transplantation (AMT) and/or botulinum toxin type A-induced ptosis (Dysport) in the treatment of corneal ulcerations of different entities.

METHODS

Retrospective evaluation of 137 cases of corneal ulcers which have been treated with AMT, botulinum toxin type A and perforating keratoplasty (pKP). Regarding corneal ulcerations the patients were divided into three groups: group A, patients initially having received an AMT (92 eyes eventually followed by AMT or pKP as a second intervention); group B, patients initially having received an AMT (32 eyes followed by botulinum toxin type A injection in the upper lid as a second intervention); group C, patients initially treated only by botulinum toxin type A injection (13 eyes followed occasionally by AMT or pKP or additional botulinum toxin type A injection). Additionally, we analysed the complete epithelialisation rate of the ocular surface in respect to different ocular and systemic diseases and compared the frequency of re-operations in each group.

RESULTS

The overall follow-up was 14.2 (+/-14.7 months; range from 1 to 60 months). The total frequency of re-operations was 45.3% (overall time until complete epithelialisation 12.7 (+/-6.1) days). If the patient was initially treated with an AMT (group A), the re-operation rate was 44.6%. Treating affected eyes in this group with a subsequent amniotic membrane resulted in a reduction of re-operation rate to 30.4%. In cases with induced ptosis by injecting botulinum toxin type A in the M. levator palpebrae (group B), the re-operation frequency could be reduced to 34.4% with similar times of epithelialisation [group A: 12.0 (+/-6.5) days and group B: 11.7 (+/-5.5) days]. In group C, with botulinum toxin type A alone initially, the re-operation rate of 69.2% was the highest one compared with groups A and B; this rate could be drastically reduced by a following AMT to 23.1%. Surprisingly, in the few successful cases with botulinum toxin type A alone a quite low epithelialisation time of 6.5 (+/-1.3) days was achieved, but turned out to be similar after additional interventions if compared with the other groups (botulinum toxin type A + AMT: 15.7 (+/-4.9) day).

CONCLUSION

AMT alone and combined with botulinum toxin type A-induced ptosis is an effective surgical approach for managing severe corneal ulcerations by promoting wound healing and stabilizing ocular surface homeostasis.

Aspectos clínicos e imunopatológicos da ceratoplastia com membrana amniótica xenógena fresca e conservada em glicerina: estudo experimental em coelhos

Avaliaram-se, por meio da análise clínica, histopatologia e imunoistoquímica, os efeitos da aplicação da membrana amniótica xenógena fresca e conservada em glicerina, sobre os mecanismos imunológicos da superfície ocular. Para tal, utilizaram-se 40 coelhos, distribuídos em dois grupos experimentais, os quais foram avaliados por 21 dias. A avaliação clínica revelou que a membrana amniótica xenógena conservada em glicerina estimulou uma resposta inflamatória aguda maior que a membrana aplicada fresca. A análise histopatológica indicou que ambas se comportaram de forma semelhante a partir da primeira semana de pós-operatório, apresentando as alterações clássicas da resposta inflamatória da córnea, com o predomínio de infiltrado do tipo polimorfonuclear. A análise imunoistoquímica indicou que, ainda aos 21 dias, a resposta imune local é inespecífica, permitindo concluir que a resposta imune específica na córnea é tardia e que a córnea é um sítio privilegiado para aplicação de enxertos com características imunológicas diferentes, visto que não houve o estímulo para o desenvolvimento de uma resposta mais específica nos grupos avaliados durante toda a execução do experimento.

Integration patterns of cryopreserved amniotic membranes into the human cornea

PURPOSE

Because of the wide spectrum of indications and the different techniques used, amniotic membrane transplantation (AMT) may result in many variants of wound healing. Our aim was to investigate and classify the integration patterns of amniotic membrane (AM) into the human anterior cornea following AMT.

DESIGN

Retrospective, noncomparative, nonconsecutive, interventional case series.

PARTICIPANTS

Twenty-four eyes of 24 patients (age, 64.9+/-13.6 years).

METHODS

Eyes underwent penetrating keratoplasty 26.1+/-25.1 weeks (range, 0.3-79) after transplantation of cryopreserved human AM. Histopathologic and ultrastructural examinations were performed on the excised corneal buttons.

MAIN OUTCOME MEASURES

Patterns were classified according to the topographic relationship between AM and corneal epithelium. The respective thicknesses of the corneal epithelium and AM layer(s) were measured.

RESULTS

Integrated AM was found in 18 of 24 corneas up to 79 weeks after transplantation. Amniotic epithelium was present in only 4 of 24 cases with intracellular signs of degeneration. Amniotic membrane stroma was integrated in 4 patterns: (1) intraepithelial (4 eyes); (2) subepithelial (11 eyes); (3) intrastromal, with various grades of retraction (4 eyes); and (4) superficial localization--AM present on the corneal surface (disintegration) (7 eyes). More than 1 pattern was found in 4 specimens. The thickness of corneal epithelium varied between 13.4 and 102.6 microm, and the thickness of AM between 9.0 and 162.5 microm.

CONCLUSIONS

Amniotic membrane can integrate into the host corneal tissue after AMT in intraepithelial, subepithelial, or intrastromal patterns, or may be localized on the corneal surface. The thicknesses of corneal epithelium and AM are extremely variable. The morphology of the individual pattern seems to depend on the ocular surface disorder and AMT technique. Classification of AM integration patterns may assist in selecting the most suitable transplantation technique for specific surface disorders.

Measurement of Light Transmittance of Cryopreserved Human Amniotic Membrane

PURPOSE

To measure the light transmission of human amniotic membrane (AM) and compare it with that of therapeutic soft contact lens (TSCL).

METHODS

Total light transmittance of each sample (4 AMs and 2 TSCLs) was measured in the 250- to 800-nm range by using a spectrophotometer.

RESULTS

The percent light transmission of TSCL was nearly 100% at wavelengths greater than 450 nm, decreased gradually in the sub-450-nm range, and reached 78.4 +/- 3.7 at 250 nm. In contrast, the percent transmission of the 4 AMs decreased gradually and continually throughout the spectrum as wavelength shortened. The transmission of light through AM dropped to less than 20% at 250 nm but remained 90% or more at wavelengths more than 600 nm.

CONCLUSION

Light transmittance properties of cryopreserved human AM and human cornea are relatively similar, but AM (and not cornea) allows transmission of 24.6% of UVC.

Amnios et problèmes de surface oculaire

The amniotic membrane, the most internal placental membrane, has various properties useful in ophthalmology. Collected on delivery by elective Caesarean section, the amnion is prepared under sterile conditions, and, usually, cryopreserved until its use as a biological bandage or as a substrate for epithelial growth in the management of various ocular surface conditions. Specifically, the amnion is used to : (1) limit formation of adhesive bands between eyelids and eyeball (symblepharon) or the progression of a fibrovascular outgrowth towards the cornea (pterygium) or to (2) facilitate the healing of corneal ulcers, bullous keratopathy, and corneal stem cell deficiency. In this last condition, either hereditary or acquired after a thermal or a chemical burn, corneal stem cells, located at a transitional zone between the cornea and conjunctiva, are lost. These cells are essential for renewal of corneal epithelium in normal and in diseased states. The loss of these cells leaves the corneal surface free for invasion by conjunctival epithelium. Not only, does conjunctival epithelium support the development of vascularisation on the normally avascular cornea, but some conjunctival cells differentiate into mucus secreting goblet cells. Such a change in phenotype leads to loss of corneal transparency and visual disability. The removal of this fibro-vascular outgrowth in combination with transplantation of both amniotic membrane and corneal stem cells are used to treat this condition. The amnion stimulates the proliferation of less differentiated cells which have the potential to reconstruct the cornea. This potential is at the origin of the hypothesis that the amnion may provide an alternative niche for limbal stem cells of the corneal epithelium. It abounds in cytokines and has antalgic, anti-bacterial, anti-inflammatory and anti-immunogenic properties, in addition to allowing, like fetal skin does, wound healing with minimal scar formation. These desirable properties are responsible for the increasing use of amniotic membrane in ophthalmology. The complete understanding of the mechanisms of action of amniotic membrane for ocular surface diseases has yet to be understood. Once revealed by research, they may provide new pharmacological avenues to treat ocular surface diseases.

Amniotic Membrane Transplantation and Fibrin Glue in the Management of Corneal Ulcers and Perforations

PURPOSE

To evaluate the efficacy of amniotic membrane in corneal ulcers refractive to conventional treatment and amniotic membrane with fibrin glue in corneal perforations.

METHODS

Amniotic membrane transplantation (AMT) was performed in 33 eyes from 32 patients for corneal ulcers refractive to conventional treatment. Fourteen ulcers were perforated and received fibrin glue and amniotic membrane. Ulcers were divided into 3 groups: neurotrophic or exposure, autoimmune, and other etiology.

RESULTS

Overall success was observed in 80% (27/33 eyes) of the cases, with success rates of 87.5% (14/16 eyes), 70% (7/10 eyes), 85.7% (6/7 eyes) in groups 1, 2, and 3, respectively. The ulcers healed in a mean time of 3.6 +/- 1.6 weeks and the follow-up was 14.8 +/- 9.9 months. Failure was noted in 6 eyes with severe neurotrophic keratitis, Stevens-Johnson syndrome, ocular cicatricial pemphigoid, and Acanthamoeba keratitis. Grafts with fibrin sealant showed a success rate of 92.9 % (13/14 eyes) compared to 73.7% (14/19 eyes) for amniotic grafts alone. In patients with severe limbal damage, a success rate of only 20% (1/5) was observed.

CONCLUSIONS

AMT is a viable option in the treatment of nonhealing corneal ulcers of various depth and etiologies. Perforations up to 3 mm can be safely managed by fibrin glue and AMT. These techniques lead to rapid reconstruction of the corneal surface and can give a good final functional result or allow keratoplasty to be done in more favorable conditions.

Greffe de membrane amniotique et traitement des ulcères de cornée lors des kératoconjonctivites chroniques allergiques

PURPOSE

To determine whether amniotic membrane implantation is a safe and effective alternative treatment for shield ulcers and persistent corneal epithelial defects associated with ulcers in chronic allergic keratoconjunctivitis (vernal or atopic keratoconjunctivitis).

METHODS

Amniotic membrane implantation was performed in four consecutive patients with persistent corneal epithelial defects or vernal plaques unresponsive to conventional medical treatment lasting an average of 18 weeks. Surgery was done under general anesthesia using amniotic membrane as a therapeutic contact lens.

RESULTS

A significant decrease in symptoms and complete reepithelialization of the corneal ulcers were observed in all cases within the first 7 days. These remained stable during a mean follow-up of 12 weeks, with no intraoperative or postoperative complications. Early detachment occurred in all cases with no negative consequences on ulcer healing.

CONCLUSION

Patients with severe chronic allergic keratoconjunctivitis derive benefits from amniotic membrane implantation used as a therapeutic contact lens in the treatment of persistent corneal epithelial defects and vernal plaques unresponsive to conventional medical treatment.

Amniotic membrane transplantation for reconstruction of corneal ulcer in graves ophthalmopathy

OBJECTIVE

To report one case of corneal ulceration associated with a severe manifestation of Graves ophthalmopathy that was treated with amniotic membrane (AM) transplantation using the inlay and overlay technique.

METHODS

Case report.

RESULTS

A 40-year-old woman with Graves ophthalmopathy had a corneal ulcer on the left eye refractory to topical treatment and orbital decompression surgery. Severe Graves ophthalmopathy was characterized by tear film instability, lagophthalmus, and reduced Bell phenomenon. After amniotic membrane transplantation the epithelial and stromal defect healed quickly with improvement of visual acuity and within the dissolution period of the overlay AM.

CONCLUSION

Amniotic membrane transplantation is a successful and alternative approach to treat severe corneal surface disorders refractory to medical treatment in patients with Graves ophthalmopathy. Besides having an anti-inflammatory action mechanism, the overlay AM used herein as a temporary patch was possibly functioning as a protective shield to ensure epithelialization of the AM used as a graft in the ulcer bed.

Amniotic membrane graft: Histopathological findings in five cases

Amniotic membrane transplantation (AMT) is an effective treatment for ocular surface reconstruction; however, the mechanisms through which amniotic membrane (AM) exerts its effects as well as its fate after transplantation have not been entirely elucidated and have been investigated only in part. We evaluate the integration of AM in the host cornea in five patients who underwent AMT as the result of Bowen's disease, band keratopathy, radio- or cryotherapy-induced keratopathy, chemical burn or post-herpetic deep corneal ulcer with descemetocele. Due to persistent opacification in four cases and a progressing tumor in one case, penetrating keratoplasty (PK) and enucleation were performed as early as 2 months and up to 20 months after AMT. The corneas were analyzed histopathologically. To evaluate AM remnants, corneas were stained with periodic acid Schiff's reaction (PAS), Alcian blue, and Gomory and Masson trichrome; immunostaining including collagens III and IV antibodies was also performed. None of the corneas showed remnants of AM. In all cases, we observed discontinuity of Bowman's membrane. In three cases, the corneal epithelium was completely restored, ranging from three to six cell layers. In the other two cases, we detected an intense inflammatory reaction with rich neovascularization; the epithelial surface of the central cornea was completely restored, while at the periphery of the cornea goblet mucus-producing cells were present. Although clinically useful in all cases, restoration of a stable corneal epithelium through AMT is limited by the extent and severity of limbal stem cell deficiency (LSCD). The lack of histologically documented AM remnants in our cases seems to explain the efficacy of AMT more through its biological properties than through its mechanical properties.

Amniotic membrane transplantation in ocular surface disorders

Chronic ocular surface disorders, which can result in severe functional impairment, have been viewed for decades as untreatable diseases. In 1995, the reintroduction of amniotic membrane transplantation (AMT), either alone or associated with limbal stem cell transplantation, has offered new hope of using tissue and cell therapy strategies to repair ocular surface disorders. Amniotic membrane (AM) has been found to exert its effects by acting as a substrate for the growth of ocular surface epithelia, by suppressing inflammation and scarring and by serving as an anti-microbial barrier. Moreover, AM has recently been used as a substrate for ex vivo expansion of corneal epithelial cells for ocular surface reconstruction. Notwithstanding the substantial agreement among Authors regarding its clinical efficacy, there are still many uncertainties regarding the fate of grafted AM and consequently the mechanisms through which it exerts its long-term effects. Further studies including controlled clinical trials with numerous cases are required to understand which ocular surface conditions are certain to benefit from AM transplantation and how its mechanical properties interact with the mediators produced to favor ocular surface reconstruction.

Conjunctival Healing after Amniotic Membrane Graft over Ischemic Sclera

PURPOSE

To present a case of chemical injury associated with calcification and severe conjunctival and scleral ischemia, in which tissue regeneration was achieved using an amniotic membrane graft.

METHODS

A 65-year-old man presented to our department 8 weeks after suffering a chemical injury of his left eye with sulfuric acid. There was extensive calcification of the cornea and conjunctiva, associated with severe ischemia of the adjacent sclera. After resection of the calcified tissue and nonviable tissue, amniotic membrane was grafted to cover the extensive zone of scleral ischemia.

RESULTS

In the weeks following grafting, slow epithelialization and revascularization was observed over the amniotic membrane, stemming from the surrounding healthy conjunctiva.

CONCLUSION

Although the presence of ischemia at the base of the graft has been considered a contraindication for amniotic membrane transplantation, this case demonstrates that, provided that the surrounding tissue is not affected, a graft may be useful. In such cases an amniotic membrane graft could be attempted before other alternatives, such as conjuntival or oral mucosal autografts.

Amniotic membrane transplantation for ocular surface pathology: long-term results

Amniotic membrane transplantation has been used for >90 years for cutaneous and mucous lesions for regeneration of tissues. In recent years its effectiveness has been demonstrated in the treatment of diseases of the ocular surface. We present our experience with 53 amniotic membrane transplantations for different ocular pathologies with two different forms of implantation. The 53 cases were divided into three groups according to pathology and type of implant. Group 1 included 24 eyes with amniotic membrane grafts after resection of extensive conjunctival lesions. Group 2 included 19 eyes with amniotic membrane grafts for corneal pathology, and group 3 consisted of 10 eyes with amniotic membrane patches for corneal epithelial defects without ulceration. No intra- or postoperative complications were observed during an average follow-up period of 32 months (24-48 months). Group 1 demonstrated rapid healing of the lesions with minimal scarring in all cases. In group 2 a favorable response was observed in 16 of 19 cases. In group 3 complete healing was achieved in only 3 of 10 cases, and the time for which the graft remained was related to the success of the treatment. The primary intention was to achieve prolonged fixation of the implant. Finally, amniotic membrane transplantation is a safe and effective technique for the treatment of different pathologies of the ocular surface. After the resection of extensive conjunctival lesions it is currently the preferred treatment. In corneal pathology, it represents an additional therapeutic alternative when conservative medical treatments fail.

Experimental anterior lens capsule transplantation for chronic corneal ulcers-Bowman's layer replacement?

PURPOSE

This study was designed to measure the value of allografted anterior lens capsule in the reepithelialization of recurrent corneal ulcers.

METHODS

Mechanical ulcers of uniform size were created with a 6-mm corneal trephine in both eyes of four Chinchilla male rabbits at one-third corneal depth. Following initial epithelial regrowth, an identical injury was created in the same area of each cornea a second time. In four eyes (treated group), an anterior lens capsule from a healthy donor rabbit was sutured into the ulcer bed followed by antibiotic/steroid drops three times daily for 1 week. The remaining four control eyes were allowed to heal without surgical intervention using the same antibiotic/steroid drops only. Slit-lamp examination and histopathology findings were recorded over a 6-month follow-up period.

RESULTS

The four treated eyes reepithelialized after the second injury at a faster rate than the control group eyes and had a lower percentage of corneal opacification at all follow-up exam dates. Histopathology revealed normal epithelium overlying the transplanted anterior lens capsule and no infiltration of inflammatory cells in the subepithelial stroma.

CONCLUSIONS

In experimental conditions, allotransplantation of anterior lens capsule speeds up reepithelialization after repeated mechanical trauma to the cornea. To our knowledge, this is the first experimental transplantation of an anterior lens capsule to create an artificial Bowman's layer in recurrent corneal ulcerations to aid reepithelialization and minimize corneal scarring.