AMT is an established technique in the treatment of various diseases of the external eye. In the last few years, AMT has brought about major advances in the reconstructive surgery of the ocular surface. Transplantation of preserved human amniotic membrane AM can be considered one of the major new developments in surgery of the ocular surface.
Although the first ophthalmological use of AM documented in the international literature took place almost 70 years ago, amniotic membrane transplantation AMT has only been performed in larger numbers of patients since , with promising results 1 — 3.
Various disorders of the ocular surface, including persistent epithelial defects of the cornea, acute chemical burns with long-term loss of integrity of the ocular surface epithelium or conjunctival scarring as a result of the healing of mucous membrane disorders still pose a clinical challenge in ophthalmic surgery. Since modern preservation methods were introduced, the innermost layer of the placenta, the AM, procured in sterile conditions following a Cesarean section, has experienced a renaissance as a basement membrane substitute.
Today it is hard to imagine reconstructive surgery of the ocular surface without it 1 — 3. Each type of application yields histologically different integration patterns for AM in the host corneal tissue 4. The most important indications in reconstructive surgery of the ocular surface are persistent epithelial defects of the cornea with corneal ulceration of varying etiology, covering defects after surgical removal of large conjunctival lesions, acute chemical burns, symblepharon and fornix reconstruction in healing conjunctival disorders, and limbal stem cell deficiency of the cornea with simultaneous stem cell grafting 5 — 7.
It reports new developments, mechanisms of action, and established indications of AMT. The AM is the innermost layer of the placenta, located next to the fetus. Histologically, it is a multilayer membrane approximately 0.
Appropriate standardized operating guidelines for procuring and manufacturing human AM from donor placenta are currently being developed with the support of the Tissue Transplantation and Biotechnology Section of the German Society of Ophthalmology Deutsche Ophthalmologische Gesellschaft, DOG e1.
When appropriately prepared it consists of a relatively thick basement membrane with devitalized amniotic epithelial cells and an avascular, almost acellular stroma. Clinical trials suggest that AM transplantation promotes epithelialization and differentiation of the epithelium of the ocular surface 5 — 9. The most important growth factors that promote wound healing, which have been isolated mainly from the amniotic epithelium but also from the AM stroma, are epidermal growth factor and keratocyte growth factor 8 , 9.
Structural proteins such as laminin and type VII collagen in the AM basement membrane explain the observed epitheliotropic effects 9 , Intrinsic neurotropic substances make AM an ideal substrate for reconstruction of the epithelium of the ocular surface 11 , In the initial phase after AMT, there is typically a significant reduction in inflammation.
In vitro, AM reduces expression of various growth factors and pro-inflammatory cytokines In addition, anti-inflammatory cytokines such as interleukin and interleukin-1 receptor antagonist are released in the epithelium and stroma of the AM and may modulate inflammatory processes. They may play a role in the healing of acute chemical burns of the cornea covered by AM 15 , AM also has an immunomodulatory effect 17 , and tissue rejection is therefore rarely observed in clinical use of AM.
As the cells of cryopreserved AM are devitalized after thawing, no enzyme activity appears, and no intact RNA can be extracted, these substances are released from the damaged, devitalized cells. Because these factors are removed after application of cryopreserved AM, longer-term use is problematic.
It is therefore advisable to replace an AM used as a patch in ocular surface reconstruction at regular weekly intervals until the desired epithelial wound closure occurs. Unlike the generally preferred cryopreservation of AM, other AM preparation procedures which are in use, such as acid pretreatment and subsequent air drying 18 , lead to near-complete loss of its biological properties, and as a result their possibilities for clinical application and their efficacy seem limited This allows procedures to be performed in a sequential manner, such as cornea transplantation with a reduced risk of rejection 5 , These aims are achieved using various different surgical procedures for AMT 5 , 6.
In the inlay technique, the AM is applied as a permanent basement membrane substitute. The main indications for this are persistent epithelial defects, corneal ulceration or to cover defects following excision of conjunctival tumors 5 , 6 , 20 — 23 , e2 Box. In deep defects, e. Epithelialization of the AM integrates AM into the host tissue 4. It remains detectable for months, sometimes years, and in defects of the cornea is even colonized by local keratocytes 4.
Covering defects after removal of large conjunctival lesions tumors, conjunctival intraepithelial neoplasia, scars, conjunctival folds parallel to the edges of the eyelids. The literature contains no evidence-based, randomized studies comparing AMT with the alternative options for these indications. Unlike the inlay technique, where the AM remains permanently on the cornea, with the onlay technique the AM patch typically becomes detached from the surface of the cornea after one to two weeks.
Classical indications range from acute burns to acute herpetic keratitis and the acute stage of Stevens-Johnson syndrome 5 , 6 , 16 , 20 , If delayed wound healing is demonstrated clinically, on the basis of the above-mentioned experimental data it seems to be advisable to change the AM patch weekly until the wound closes as desired. The orientation of the AM plays only a minor role with this surgical procedure: in most cases attaching the AM loosely in the episcleral space or to the bulbar conjunctiva using monofilament vicryl sutures is considered sufficient 5 , 6.
This technique, also called the sandwich technique, is a combination of the two described above and is used mainly in serious disorders of the ocular surface such as deep and extensive corneal ulceration, or in surgical revisions 5 , 6. The main purpose of the onlay is to protect the inlay and promote its epithelialization 4 , 5. The AM has only recently been described as a culture substrate for ex vivo expansion of the epithelium of the ocular surface 7 , 25 , e3 — e5.
Here the AM functions as a biomatrix and is placed on the surface of the eye together with the cultivated cells e3 , e4. This technique is mainly used to treat limbal stem cell deficiency, but also in reconstruction of major surface defects of the outer eye 7 , 25 , e5 , e6. So many indications of AMT have already been described in the literature that they would go well beyond the boundaries of this review article 5 — 7 , 16 , 21 — 25 , e2 , e5 , e6.
The main indications of AMT are therefore summarized in the Box. Unfortunately, reliable clinical data have only been published in small to medium numbers of cases, with a relatively short follow-up period, and overwhelmingly in retrospectively analyzed case series e6 , probably due to the low incidence of individual disorders of the ocular surface.
There are no Cochrane Reviews or meta-analyses available from either the Cochrane Library or PubMed on the subjects discussed in this review article. Five eyes were noted to have asymptomatic thinning of the patch without evidence of tube erosion. Conclusions: Preserved human cadaveric pericardial patch grafts appear to be well-tolerated for use with glaucoma drainage devices. Scleritis is a serious inflammatory disease with an etiology of idiopathic, autoimmune, or infectious, that can cause severe ocular pain and occasionally impaired vision.
It is usually associated with systemic diseases such as systemic lupus erythematosus, rheumatoid arthritis, and granulomatosis with polyangiitis.
Responsive sclera inflammation occasionally arouse in the process of infectious diseases such as syphilis, tuberculosis, and zoster. Gram-negative bacteria, Gram-positive cocci and filamentous fungi, which are also responsible for microbial keratitis, are often reported causes.
Fortunately, the graft were stable and did not developed graft necrosis after a surgery of sclera patch graft and autologous conjunctival pedicle flap in the 36 months follow-up. Nevertheless, it is necessary to screen and rule out systemic vasculitic disorders preoperatively. Non-emergency surgery should be deferred until medical therapy, such as systemic glucocorticoids or immunosuppressive agents, has controlled the primary disease, if detected.
Attention should be paid to iatrogenic injury in ocular medical activities. A patch graft helps to restore structural integrity of the globe. A various of material and techniques are commonly employed today to manage ocular diseases that devastate to structural stability of the eye. Still no material has been proved to be generally accepted. Allogeneic sclera was commonly used as a graft in cases of impending scleral rupture, ectasias, or dehiscence. Varied success has been reported with the use of scleral patch grafts.
Scleral patch graft remains a universal option 10 due to its relatively availability, strength, flexibility and easy to preserve. The only criticism is that it may involve in the ongoing process of necrosis and melting because of avascular. The scleral stroma is normally avascular and receives its nutritional supply from choroidal blood vessels and from the vascular plexus in the tenon capsule and on the episcleral surface Acute severe chemical, thermal burns and ocular surgeries are the common causes of scleral ischemia, thinning, and melt.
In addition, scleral melt has been described after retinal detachment repair, glaucoma surgery, and cataract surgery. How to deal with scleral dissolution is still challenging.
Victoria E. Casas reported four successfully cases of use tenon pedicle graft to cover the ischemic zone for scleral ischemia and melt 7. Yazici B reported two successfully cases of use of Conjunctiva-Muller muscle pedicle flap in surgical treatment of necrotizing scleritis About Foundation Museum of the Eye. About Our Coding Experts About Our Coding Experts Our expert staff have decades of combined experience, covering all aspects of coding and reimbursement.
David B. Email coding aao. SEP 28, Medical and Surgical Options for Presbyopia.
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