Amniotic membrane transplantation: structural and biological properties, tissue preparation, application and clinical indications

The amniotic membrane is a single epithelial layer of the placenta. It has anti-inflammatory, anti-scarring, anti-angiogenic and possibly bactericidal properties. The basement membrane of the amniotic membrane acts as a substrate to encourage healing and re-epithelialisation. It has been used in many ocular surface diseases including persistent epithelial defects (corneal or conjunctival), chemical or thermal burns, limbal stem cell deficiency, cicatrising conjunctivitis, ocular graft versus host disease, microbial keratitis, corneal perforation, bullous keratopathy, dry eye disease, corneal haze following refractive surgery and cross-linking, band keratopathy, ocular surface neoplasia, pterygium surgery, and ligneous conjunctivitis. This review provides an up-to-date overview of amniotic membrane transplantation including the structural and biological properties, preparation and application, clinical indications, and commercially available products.

Freeze-dried amniotic membrane graft with a spongy layer in bilateral peripheral ulcerative keratitis: a case report

BACKGROUND

Peripheral ulcerative keratitis (PUK) is a group of inflammatory corneal ulcers with stromal thinning and peripheral localization. Amniotic membranes (AM) are used for their anti-inflammatory and healing properties. A freeze-drying process now allows maintaining the AM viable for a long time at room temperature without altering its physical, biological, and morphologic characteristics. The effectiveness of spongy freeze-dried amniotic membrane (FD-AM) graft with multimodal imaging in the management of severe corneal thinning PUK has not been reported.

CASE PRESENTATION

A 67-year-old Caribbean man histologically diagnosed with ulcerative colitis, was referred to our tertiary eye care center for a deep nasal juxtalimbal ulcer of the left eye. He was treated with topical steroids and antibiotics, methylprednisolone pulses, and oral prednisone. Due to continuous stromal thinning with 100 μm of residual corneal thickness, the decision was made to perform surgery. Conjunctival resection, inlay and overlay spongy FD-AM (Visio Amtrix® S, Tissue Bank of France, FR) were performed to preserve globe integrity. Despite tapering off oral steroids, PUK developed in the fellow eye on the 2 months follow-up. Treatment with human monoclonal antibody against tumor necrosis factor-alpha was initiated to control the active underlying inflammation. Six months following surgery, the ulcer was healed and corneal thickness in front of the former ulceration was measured at 525 μm on anterior segment-optical coherence tomography. Confocal microscopy confirmed the integration of the amniotic membrane between the corneal epithelium and the anterior stroma.

CONCLUSION

Transplantation of FD-AM with a spongy layer was associated with restoration of normal corneal thickness in the PUK area. It seems to be a safe, effective, and easily accessible solution for the surgical management of PUK with impending perforation.

CLEAR - Medical use of contact lenses

The medical use of contact lenses is a solution for many complex ocular conditions, including high refractive error, irregular astigmatism, primary and secondary corneal ectasia, disfiguring disease, and ocular surface disease. The development of highly oxygen permeable soft and rigid materials has extended the suitability of contact lenses for such applications. There is consistent evidence that bandage soft contact lenses, particularly silicone hydrogel lenses, improve epithelial healing and reduce pain in persistent epithelial defects, after trauma or surgery, and in corneal dystrophies. Drug delivery applications of contact lens hold promise for improving topical therapy. Modern scleral lens practice has achieved great success for both visual rehabilitation and therapeutic applications, including those requiring retention of a tear reservoir or protection from an adverse environment. This report offers a practical and relevant summary of the current evidence for the medical use of contact lenses for all eye care professionals including optometrists, ophthalmologists, opticians, and orthoptists. Topics covered include indications for use in both acute and chronic conditions, lens selection, patient selection, wear and care regimens, and recommended aftercare schedules. Prevention, presentation, and management of complications of medical use are reviewed.

Amniotic Membrane Transplant for Bullous Keratopathy: Confocal Microscopy & Anterior Segment Optical Coherence Tomography

PURPOSE

To assess amniotic membrane retention after amniotic membrane transplant in bullous keratopathy patients and whether there were any corneal structural changes that may hinder further penetrating keratoplasty Methods: A retrospective study including 22 patients who have undergone amniotic membrane transplant from 1 Jan 1998 till 30 Jun 2016. Confocal microscopy and anterior segment optical coherence tomography (ASOCT) were performed to assess the retention of amniotic membrane and to detect any corneal structural changes. The comparison was made with 5 controls who had bullous keratopathy awaiting endothelial keratoplasty.

RESULTS

Patients had a mean follow-up of 61 ± 33.7 months. Pain reduction was significant (p < .001) although it did not significantly correlate with the regularity of the superficial, intermediate or basal epithelial layers, nor with the retention of the amniotic membrane. No long-term structural changes that may hinder future penetrating keratoplasty were detected.

CONCLUSION

This procedure is a safe and effective long-term treatment for symptomatic bullous keratopathy patients.

Efficacy of Anterior Stromal Puncture Surgery with Corneal Bandage Lens for Bullous Keratopathy

Objective: To investigate the safety and efficacy of the combination therapy of anterior stromal puncture (ASP) with bandage contact lens for bullous keratopathy (BK). Methods: Twelve cases (12 eyes) with vision acuity no better than light perception were treated with ASP surgery and bandage contact lens. 200 points punctures were made through the corneal epithelium and Bowman's layer vertically, using fine needles. A soft bandage contact lens was applied immediately and removed 2 weeks later. The severity of irrigating symptoms including pain, photophobia and tearing was graded and calculated before treatment and 1, 2, 4, 12 weeks after the surgery, slit-lamp microscope examination was used to quantify the time for corneal epithelial blisters disappearing, optical coherence tomography (OCT) was used to monitor the central corneal thickness. Results: No cornea infection was observed during the following up period. The average grade scores of the irrigating symptoms was 8.3 ± 2.1 before surgery, while it was reduced to 4.8 ±1.9 two weeks after the surgery (p=0.0003). Slit-lamp microscope examination showed that corneal edema relieved obviously after the operation, the average time for epithelial blisters disappearing was 15.6 ± 4.0 days. The average central corneal thickness of the eyes was 999.3 ±278.0 μm before the treatment, while it was 805.1 ± 145.0 μm four weeks after the treatment, with a statistically significant difference (p=0.043). Conclusions: ASP with bandage contact lens is an effective and safe treatment for patients with BK and low vision that not suitable for corneal transplantation.

Corneal endothelial cell dysfunction: etiologies and management

A transparent cornea is essential for the formation of a clear image on the retina. The human cornea is arranged into well-organized layers, and each layer plays a significant role in maintaining the transparency and viability of the tissue. The endothelium has both barrier and pump functions, which are important for the maintenance of corneal clarity. Many etiologies, including Fuchs’ endothelial corneal dystrophy, surgical trauma, and congenital hereditary endothelial dystrophy, lead to endothelial cell dysfunction. The main treatment for corneal decompensation is replacement of the abnormal corneal layers with normal donor tissue. Nowadays, the trend is to perform selective endothelial keratoplasty, including Descemet stripping automated endothelial keratoplasty and Descemet’s membrane endothelial keratoplasty, to manage corneal endothelial dysfunction. This selective approach has several advantages over penetrating keratoplasty, including rapid recovery of visual acuity, less likelihood of graft rejection, and better patient satisfaction. However, the global limitation in the supply of donor corneas is becoming an increasing challenge, necessitating alternatives to reduce this demand. Consequently, in vitro expansion of human corneal endothelial cells is evolving as a sustainable choice. This method is intended to prepare corneal endothelial cells in vitro that can be transferred to the eye. Herein, we describe the etiologies and manifestations of human corneal endothelial cell dysfunction. We also summarize the available options for as well as recent developments in the management of corneal endothelial dysfunction.

Corneal Tattooing and Anterior Stromal Puncture for Treating Symptomatic Bullous Keratopathy

PURPOSE

To investigate the efficacy of corneal tattooing, through anterior stromal puncture (ASP), for managing painful bullous keratopathy (BK).

METHODS

This retrospective, case-controlled, consecutive case series study was performed at a university-based referral clinic. Patients with painful BK who underwent corneal tattooing with Chinese ink between 2007 and 2013 were included in analyses. Patients diagnosed with symptomatic BK who only underwent ASP during the same period were included as a control group.

RESULTS

A total of 40 patients (27 men, 13 women) with a mean age of 57.5 ± 15.3 years were included in analyses. The clinical diagnosis was pseudophakic BK in 5 subjects (12.5%), failed graft in 11 subjects (27.5%), BK secondary to perforating corneal injury repair in 19 subjects (47.5%), and end-stage glaucoma in 5 subjects (12.5%). Subjects were followed for a mean period of 26.4 ± 7.5 months (range: 6-55 months). Recurrent bullae formation occurred in 3 of 31 patients (9.68%) who had undergone corneal tattooing and in all 9 patients (100%) who had undergone ASP (P < 0.001).

CONCLUSIONS

Corneal tattooing with Chinese ink is a simple, effective outpatient procedure for treating painful BK in eyes with no visual potential.

Long-term symptomatic relief of bullous keratopathy with amniotic membrane transplant

The purpose of this study was to assess the long-term outcome of patients with symptomatic bullous keratopathy after amniotic membrane transplant. A retrospective cohort study includes that 20 patients with symptomatic bullous keratopathy, who have underwent amniotic membrane transplant at the Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Prince of Wales Hospital & Alice Ho Miu Ling Hospital, Hong Kong between 04/1998 and 06/2011, were invited back. Clinical examination was performed, including, pain score assessment (pain score out of 10), epithelial healing, and vision. A total of 21 eyes of 20 patients returned for our study. The majority of eyes experienced pain reduction (94 %), with a significant mean pain score difference of 6.8 ± 2.6, 2-tail p < 0.001 (99 % CI 4.9-8.7). The mean pre-operative and post-operative pain scores were 7.3 ± 2.9 and 0.5 ± 1.0, respectively. 16 eyes (76 %) were completely pain free, and 10 eyes (47 %) remained symptom free after a mean follow-up of 39.0 ± 36.3 months (range 5-171 months). The median epithelial healing time was 2 weeks (range 1-20 weeks). Amniotic membrane transplant may be considered as a longer-term treatment for bullous keratopathy patients, especially in patients with poorer visual prognosis, but it may also be used as an interim measure for patients awaiting corneal transplant.

Alternatives to corneal transplantation for the management of bullous keratopathy

PURPOSE OF REVIEW

Corneal transplantation remains the gold-standard treatment for bullous keratopathy patients as it provides symptomatic relief and visual rehabilitation. As corneas are not always available for transplant, alternative treatments have to be considered for alleviation of discomfort and pain.

RECENT FINDINGS

Various treatment options available in such cases include conjunctival flaps, anterior stromal puncture, amniotic membrane transplantation, phototherapeutic keratectomy, bandage contact lenses, and hypertonic saline eye drops. A combination of the above treatments can be employed depending upon the severity of bullous keratopathy and co-existing corneal edema. New potential treatments include collagen cross-linking (CXL), cultured endothelial cell injection, and topical treatment with Rho-associated kinase (ROCK) inhibitor.

SUMMARY

There is a lack of clinical trials comparing the safety and efficacy of the currently available treatment options for the management of bullous keratopathy. The effect of these treatments on subsequent corneal transplant has not been observed. CXL seems to offer short-term benefit for relief of pain. Newer potential treatment modalities such as ROCK inhibitors are claimed to be useful for the reversal of early edema associated with corneal endothelial dysfunction; however, long-term clinical trials are awaited.

[Suture-free amniotic membrane transplantation]

Amniotic membrane transplantation has been used very successfully in ophthalmology since the 1940s for treatment of surface disorders. Over the course of the years the indications for use have been continuously extended. In contrast the operative technique is predominantly invasive, i.e. the amniotic membrane is surgically sutured onto the surface of the eye. In order to avoid surgical trauma the authors have developed a device which allows the amniotic membrane to be stretched in a ring and the amniotic ring can then be placed suture-free on the eye surface. The authors are hopeful that the biological principle of the amniotic membrane can be better utilized by uncomplicated repetitive application.