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Department of Ophthalmology, Royal Victorian Ear and Eye Hospital, Centre for Eye Research Australia, Melbourne, AustraliaFaculty of Science, Medicine, and Health, The University of Melbourne, Australia
Corresponding author at: Department of Ophthalmology, Royal Victorian Eye and Ear Hospital, University of Melbourne, Centre for Eye Research Australia, Australia.
Department of Ophthalmology, Royal Victorian Ear and Eye Hospital, Centre for Eye Research Australia, Melbourne, AustraliaFaculty of Science, Medicine, and Health, The University of Melbourne, AustraliaFaculty of Medicine, Central Clinical School, Monash University, Australia
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Province Key Laboratory of Ophthalmology and Vision Science, Guangzhou, China
Department of Ophthalmology, Royal Victorian Ear and Eye Hospital, Centre for Eye Research Australia, Melbourne, AustraliaFaculty of Science, Medicine, and Health, The University of Melbourne, Australia
Sclera forms the outer fibrous coat of the eye and provides structural integrity for the housing of intraocular contents. Scleral thinning is a serious progressive condition which can lead to perforation and worsening visual functioning. This review aims to summarize the anatomical consideration and causes of scleral thinning, diagnosis, and the various surgical approaches available to treat scleral thinning.
Materials and methods
The narrative literature review was conducted by senior Ophthalmologists and researchers. PubMed, EMBASE, Web of Science, Scopus, and Google Scholar databases were searched for relevant literature from infinity till March 2022. Terms of the search referred to ‘sclera’ or ‘scleral thinning’ or ‘scleral melting’, and were combined with ‘treatment’, or ‘management’ or ‘causes’. Publications were included in this manuscript if they offered information about the nature of these topics. Reference lists of relevant literature was searched. There were no limits on type of article to be included for this review.
Results
Scleral thinning arises from diverse congenital, degenerative, immunological, infectious, post-surgical, and traumatic etiologies. It is diagnosed upon slit-lamp examination, indirect ophthalmoscopy, and optical coherence tomography. Conservative pharmacological treatment of scleral thinning may include anti-inflammatory drugs, steroid drops, immunosuppressors, monoclonal antibodies, and surgical treatments including tarsorrhaphy, scleral transplantation, amniotic membrane transplantation, donor corneal graft, conjunctival flaps, tenon’s membrane flap, pericardial graft, dermis graft, cadaveric dura mater graft, and other autologous and biological grafts.
Conclusion
Scleral thinning treatments have developed dramatically in recent decades and the rise of alternative grafts for scleral transplantation procedures or use of conjunctival flaps have taken center stage in surgical management. This review adds a comprehensive summary of the scleral thinning with attention to the positive and negative features of new treatments alongside previous mainstay management strategies.
Forming around 85% of the outer human eyeball, sclera is primarily comprised of Type 1 fibrous collagen arranged in a hydrated interfibrillar matrix of proteoglycans and glycoproteins.[
] Usually associated with systemic conditions or postsurgical complications, scleral thinning can be triggered by high myopia, chronic scleritis, systemic vasculitis or scleral injuries following trauma/pterygium surgery.[
] Excessive use of cautery in the scleral bed, overuse of antimetabolites like mitomycin for pterygium, various ocular surgeries, protracted irradiation and transscleral diode laser cycloablation can also predispose the sclera to thin.[
] Its pathophysiology lies in the proteolytic degradation of collagen and other extracellular matrix components of the sclera leading to stromal degradation and thinning. In rare instances, this condition can also lead to staphyloma formation, scleral perforation, and uveal melanoma.[
Exogenous scleritis: -Post-traumatic -Surgical infections secondary to intraocular surgeries like pterygium, cataract/lens, and scleral buckle surgery -From contiguous infections such as keratitis Endogenous variant –Non-infectious diffuse, nodular, or necrotizing scleritis
Graft dehiscence, resorption, low tectonic support, may transmit infectious agents from donor.
To promote epithelization/inhibit fibrosis in isolation or combination with scleral grafts for greater support, multilayered AMT may provide additional reconstruction and healing.
Fashions the surrounding conjunctiva to cover a melted or necrotic lesion
Wide surface coverage, better control of corneal inflammation and pain, no need of donor tissue, ease of procedure, protects against infection
Ptosis, retraction of the eyelid, fornix shortening and eyelid margin deformities
Provides a vascularized flap for nutrient and oxygen delivery to relieve ischemia and provide immunogenic support
Necrotizing scleritis following pterygium excision, hypersensitivity reactions and post-operative infections, scleromalacia following pterygium excision.
Easily obtained from the patient without the for need additional donor site preparation
Vascularity, good graft survival, lowered inflammatory response
Not to be used alone in large ischemic defects
Provides a vascularized flap for nutrient and oxygen delivery to relieve ischemia and provide immunogenic support against infection, provides a bridge for conjunctival or limbus cells to migrate
M. Alkharashi, A.F. Dagi, L.R. Dagi. Pericardial patch graft repair of severe localized scleral thinning encountered during strabismus surgery, Journal of American Association for Pediatric Ophthalmology and Strabismus {JAAPOS} 21(2) (2017) 156-156. e1.
R.W. Enzenauer, R.J. Enzenauer, V.B. Reddy, F.M. Cornell, S. West. Treatment of scleromalacia perforans with dura mater grafting, SLACK Incorporated Thorofare, NJ. 1992. 829-832.
Randomized trial comparing multilayer amniotic membrane transplantation with scleral and corneal grafts for the treatment of scleral thinning after pterygium surgery associated with beta therapy.
] While reinforcement of sclera is necessary to prevent secondary infection and descensus of ocular contents, the normal healing mechanism is complex, involves proteins and their corresponding integrin receptors, growth factors, and numerous proteolytic enzymes.[
Randomized trial comparing multilayer amniotic membrane transplantation with scleral and corneal grafts for the treatment of scleral thinning after pterygium surgery associated with beta therapy.
] This has led to the rise of topical treatments like lubricants and epithelialization stimulators for the conjunctiva to buffer and prevent further thinning. These include hyaluronic acid, autologous serum, and fibronectin, and growth factors, such as nerve growth factor and epidermal growth factor. Systemic drugs like immunosuppressants, tetracycline derivatives, and biologics have also successfully treated scleral injuries.[
] In the event of clinical treatment failure, various surgical techniques have taken centre stage of management including scleral transplantation procedures using scleral homografts or allografts, pericardium patch grafts (tutoplasty), amniotic membrane grafting or use of conjunctival flaps.[
] Although these have been revolutionary for preventing adverse outcomes of scleral thinning, they each carry distinct advantages and disadvantages depending on scleral patch graft materials and technique used. To date, a comprehensive summary of these new treatments is yet to be published, therefore this literature review aimed to summarize the anatomy of sclera, causes of scleral thinning, and the various surgical approaches available for scleral thinning.
2. Methods
A systematic search of PubMed, EMBASE, Web Of Science, Scopus, and Google Scholar databases was conducted to collect relevant literature until March 2022. Terms of the search referred to ‘sclera’ or ‘scleral thinning’ or ‘scleral melting’, and were combined with ‘treatment’, or ‘management’ or ‘causes’. Publications were included in this manuscript if they offered information about the nature of these topics and were published in the English language or had published translated alternatives. All publication types were considered as long as they included the topics related to the systematic search. Reference lists of relevant literature were also screened. There were no limits on type of article to be included for this review.
3. Sclera anatomy
Embryologically the sclera originates from the mesoderm and is thicker in males than in females. Ultra-structurally, sclera can be divided into three parts: (1) episclera: the thin densely vascularized layer of connective tissue overlying sclera that is situated below tenon’s capsule and is supplied by anterior and posterior ciliary arteries; (2) scleral stroma, which comprises 95% of the total sclera and is largely composed of collagen, fibroblasts, proteoglycans, and glycoproteins; (3) lamina fusca, the innermost layer of sclera characterized by richness of melanocytes (Fig. 1).[
] The human sclera is thickest near the optic nerve, thinnest at the insertion of extraocular muscles, and gradually thickens towards the cornea. Sclera is a relatively avascular structure; hence its tissue has a low metabolic demand from slower turnover rates of collagen and other cell types.[
] Sclera is richly supplied by the ciliary nerves. While the anterior segment is mainly innervated by the two long ciliary nerves branching from the nasociliary nerve, the posterior sclera receives innervations from the short ciliary nerves derived from the ciliary ganglion. Any damage to these nerves causes inflammation and pain resulting in episcleritis and scleritis.[
Congenital thinning of sclera and the natural transparency of collagen fibers in this tissue lead to a blueish hue of the eye from the underlying uvea showing through.[
] Congenital and hereditary diseases associated with blue sclera include collagen disorders like osteogenesis imperfecta and Marfan's syndrome, although non-congenital diseases like iron deficiency anemia also can be associated with blue sclera.[
] Severe forms are most often diagnosed early in life, but mild cases may not be noted until later ages.
4.2 Degenerative
Pathological myopia, also known as degenerative myopia, is characterized by excessive axial elongation resulting in gradual scleral thinning and shearing forces within the choroid, retina, and vitreous body.[
] Though these changes are minor initially they can lead to substantial scleral thinning and Bruch’s membrane defects over time, causing pathological conditions of the posterior fundus like maculopathy, retinal detachment, and posterior staphyloma. Degenerative myopia is distinct from high myopia, which in contrast is a disease of refractive error rather than myopic lesions.
4.3 Immunological
Scleral melting secondary to necrotizing scleritis is associated with systemic diseases, in particular the vasculitides or autoimmune conditions like rheumatoid arthritis,[
]. Although systemic diseases like rheumatoid arthritis and polyarthritis are mostly stable with close management, the ocular inflammatory response may spread to the episcleral, choroid, ciliary body, and retina, producing secondary complications such as choroiditis, chorioretinitis, retinal detachment, keratitis, cyclitis, episcleritis, cataract, secondary glaucoma, and perforation. In such cases, management is mainly directed towards treating the immunological cause.
4.4 Infectious
Viruses, bacteria, fungi, and parasites can cause infectious scleritis which comprises 4–10% of all scleral thinning cases. Often indistinguishable from those caused by underlying systemic disease, infectious scleritis can be classified into its exogenous and endogenous forms.[
] Exogenous scleritis arises from post-traumatic and surgical infections, and extend from contiguous infections, such as keratitis. Its endogenous variant is less frequent and can mimic non-infectious diffuse, nodular, or necrotizing scleritis. It is mainly managed with topical/systemic -antimicrobials and steroids. Exogenous scleritis usually requires combined medical and surgical management because of its destructive, suppurative nature and poor antibiotic penetration.[
Surgically induced necrotizing scleritis (SINS) is mainly characterized by non-infectious granulomatous inflammation secondary to intraocular surgeries like pterygium, cataract/lens, and scleral buckle surgery. Scleral melting and necrosis are well reported complications following pterygium surgery with adjunctive treatment of beta irradiation or mitomycin C and thiotepa – enzymatic agents used to reduce pterygium recurrence post excision.[
] Though etiology of SINS is unclear, hypersensitivity and localized ischemia at the surgical site post pterygium excision is well documented. This disrupts the episcleral vasculature leaving an avascular scleral bed that is perpetuated by excessive punctual cautery. Early clinical suspicion and appropriate staining of scrapings, cultures, or biopsies are crucial for its diagnosis.
4.6 Trauma
Trauma, swelling and/or severe inflammation of sclera can lead to dangerous thinning and perforation from rises in intraocular pressure.[
] Following direct penetrating trauma, increased stress in the corneoscleral shell and globe rupture may occur. If the force from the insulting object is mild but sufficiently blunt, the increased intraocular pressure can cause rupture of the sclera at the site where it is thinnest and weakest.[
Patients with scleral thinning complain of non-specific irritation to the eye, while pain is generally absent, and vision is unaffected. Changes in scleral color is often noticed by a relative that prompts the patient to see their doctor, or by a medical practitioner during routine examinations. Scleral thinning is best identified on slit-lamp examinations and indirect ophthalmoscopy where weakening of the anterior and posterior segment of the eye is visualized.[
] Several features may be identified, and include translucent or blue/red/violaceous sclera, congestive superficial episcleral networks, necrotic scleral plaques, dark uveal tissue, bulging staphyloma, and displaced slit lamp beams although confirmatory investigations may be required at higher magnifications. Ultrasound biomicroscopy (UBM) is a good investigation for measuring the scleral thickness of the anterior segment, although it only visualizes 3.0 mm posterior from the scleral spur. Therefore, for posterior segment disorders like glaucoma, if sclera close to the posterior optic nerve head needs examination, optical coherence tomography (OCT) is more useful.[
] OCT also allows for anterior and posterior segment imaging and uses low-coherence light to obtain a high-resolution image. When comparing the two, UBM requires a supine posture, topical anesthesia and is more time-consuming, while OCT is a non-contact imaging technique with a higher resolution for measurement of the anterior sclera and conjunctiva-tenon capsule.[
] Its newer alternative, swept-source OCT, improves resolution of the posterior segment further through higher scanning speeds and longer wavelengths for deeper penetration.[
Pharmacological management of scleral thinning is directed towards the underlying cause and may comprise topical and systemic treatment. If arising from an underlying disease, targeted therapy of that cause may alleviate further thinning. As an adjunct, topical eye drops containing steroids or non-steroidal anti-inflammatory drugs like flurbiprofen, indomethacin are used. For those with an infectious origin, topical antibiotics are the mainstay of treatment. Though eye drops can control inflammation to an extent, these are insufficient to halt the process and systemic treatment may be necessary. While oral corticosteroids considerably reduce ocular inflammation they are also associated with dose-dependent side effects,[
] If scleral thinning is particularly severe, cyclophosphamide, anti-tumour necrosis factor therapies or biologic therapies (i.e rituximab, infliximab or adalimumab) may also implemented.[
] In a study by Cao JH et al., biologics like rituximab has resulted in drug free remission in cases of recalcitrant non-infectious scleritis, where 93.3% of patients showed initial improvement at six months and 61% patients showed sustained effect at 32 months follow up.[
Non-invasive, may be targeted to the cause of scleral thinning (i.e infection, autoimmune condition).
Disadvantages.
Pharmacological side effects of immunosuppressive drugs, which mainly include risk of diabetes, indigestion, weight gain and risk of infection, as well as negative effects on the function of metabolizing organs including liver and kidney enzymes, which require ongoing monitoring. Biologic therapies which are only administered intravenously (i.e infliximab) also require multiple visits to clinic.
6.2 Tarsorrhaphy
Tarsorrhaphy is a surgical process whereby the eyelids are sutured together to protect the cornea (Fig. 2).[
] It was first used to prevent scleral thinning and other post-operative complications following pterygium treatment with mitomycin in 2005 by Wood et al, but has also been used frequently following carbon dioxide laser to prevent scleral show.[
] Following excision of excessive fibrovascular tissue, Wood et al. applied mitomycin intraoperatively for one minute to sclera and sub-conjunctiva before conjunctive reattachment and tarsorrhaphy was performed. Tarsorrhaphy prevented adverse effects associated with mitomycin, likely through the promotion of re-epithelialization of collagen and elastin in the conjunctiva. The degree of lid closure needed to protect the ocular surface determines whether a temporary or permanent tarsorrhaphy needs to be performed to promote epithelial healing, but Wood et al. was able to reopen sutures after 36.7 and 17 days for the mitomycin and non-mitomycin groups, respectively. Depending on the extent and location of the injury, a medial, lateral, or central tarsorrhaphy may be performed.[
Fig. 2A) Vertical incision between tarsus and orbicularis oculi for tarsorrhaphy. B) View of the tarsus of the upper and lower eyelids. C) Double armed mattress suture is passed through the upper and lower tarsal plates with sutures 4–5 mm from each other. D) The sutures are then tied over to complete the tarsorrhaphy.
Temporary tarsorrhaphy allows the lids to be kept securely closed over several weeks without damage to the lid margins and permits inspection by untying and retying the suture without needing replacement.[
Scleral patch grafting is a surgical procedure which aims to patch or cover the thinned sclera with full or partial thickness donor tissue to restore integrity and prevent inflammation.[
] Coating of orbital implants and exposed glaucoma drainage devices with patch grafts is necessary to promote epithelialization of conjunctiva and assist with scleral reconstruction. When patch graft autologous tissues provide insufficient scleral coverage, allogeneic grafts are opted. Desirable characteristics of an allogenic graft material include biocompatibility, immunological safety, cost effectiveness, easy availability, and usage procedure.[
] The most used patch graft material are preserved sclera, pericardium, cadaveric dura mater, amniotic membrane, and donor cornea. A case series by Robert and Watzke,[
] reported a case of unexpected extreme scleral thinning secondary to scleral buckling procedure in a 77-year-old female with retinal detachment, where preserved sclera was used as a patch graft alongside pars plana vitrectomy with good outcomes. The first case of poryphoria cutanea tarda with severe scleral involvement treated successfully by allogenic donor scleral patch graft was recently documented by Tiple et al,[
Of all the materials, scleral patch graft is commonly used in anterior segment pathologies due to its low cost and easy preservability. It has demonstrated good suitability for a range of emergent acute and chronic etiologies, which suggest it has diverse applications.
Disadvantages.
Avascularity of the sclera poses risk for progressive tissue necrosis and melting.[
] In addition, the preserved sclera is thick and less preferred cosmetically, with allied limitations of sterility and variable quality. Complications like graft retraction, thinning, dehiscence, and necrosis are also associated with used of preserved scleral grafts.[
Amniotic membrane transplantation (AMT) has been used in recent years to prevent scleral abnormalities post pterygium surgery and after ocular surface biopsies but has also reduced scleral melting by accelerating epithelialization of the ocular surface and providing tectonic support for deep tissue loss. Amniotic membrane, the innermost layer of placental membrane, consists of a thick basement membrane and an avascular stroma, the schematic diagram of AMT alone or procedure in conjunction with other adjuncts can be seen in Fig. 3.[
] Hwan and Kim reported the effectiveness of using AMT along with scleral grafting, especially when the adjacent conjunctiva was deficient or not suitable. Rapid re-epithelialization of the conjunctiva and marked improvement in visual acuity was noted in most patients.[
] reported a cluster of four cases where they studied efficacy and safety of cryopreserved AMT, which showed it reduced stromal melting and promoted re-epithelialization of the ocular surface in extensive infectious scleral and corneoscleral ulcers. Two case reports of infectious scleritis and melting from Pseudomonas aeruginosa following pterygium surgery was successfully treated with combined umbilical amnion graft and AMT.[
Randomized trial comparing multilayer amniotic membrane transplantation with scleral and corneal grafts for the treatment of scleral thinning after pterygium surgery associated with beta therapy.
Fig. 3A) Amniotic membrane transplantation alone (amniotic membrane is colored as yellow being placed over the denuded cornea, limbus and conjunctiva). B) Amniotic membrane transplantation being combined with limbal stem cell transplantation. C) Amniotic membrane transplant as a patch covering the limbal tissues. D) Amniotic membrane patch covering the limbal tissues placed between limbal grafts, known as ‘sandwich’ technique.
AMT helps with rapid surface epithelialization on the conjunctiva, wound healing, basement membrane reconstruction, reduced inflammation, reduced vascularization, and reduced scarring.[
The scleral graft does not contain epithelium and survival is jeopardized on avascular surfaces; graft dehiscence is noted in cases where the amniotic membrane retracts leaving the sclera bare.[
] A randomized control trial revealed AMT alone had a fast resorption, and median scleral thickness in AMT groups was less compared with thickness of sclera post lamellar corneal and lamellar scleral transplants 6 months after surgery.[
Randomized trial comparing multilayer amniotic membrane transplantation with scleral and corneal grafts for the treatment of scleral thinning after pterygium surgery associated with beta therapy.
Corneal patch grafts have appreciable strength, rigidity and tectonic support that can preserve globe integrity. Corneal patch grafts also have less propensity to cause graft melting and conjunctival rejection, and does not usually require additional AMT of flaps, which make it more advantageous over other graft materials. This technique has reportedly shown improved functional and cosmetic outcomes for treatment of anterior segment disorders of the cornea and sclera.[
]. Cornea is also transparent in nature compared to sclera, which is otherwise opaque, enabling better monitoring of glaucoma drainage device (GDD). More obvious corneal curvatures resulting from corneal grafts may cause surface swelling when placed on a large scleral defect. To prevent this, partial-thickness corneal grafts prepared from donor corneas are used for better cosmetic outcomes and prevention of dellen.[
] Kim et al., noted significantly higher epithelial wound healing indexes of conjunctiva and lower immune reaction in corneal grafts compared with scleral grafts in scleral defect rabbit models.[
] Ti and Tan also noted 19/20 patients receiving corneal grafts for scleral necrosis post-pterygium surgery were successful alongside conjunctival flap or pedicle.[
] Naseripour et al., found corneal graft successfully treated scleral necrosis with satisfactory cosmetic outcomes secondary to plaque radiotherapy following malignant melanoma management at mean follow up of 28.5 months.[
Compared to scleral tissue, corneal tissue is more compact and resistant to recurrent melting and infection spread and may provide superior epithelialization and lower immunogenicity.
Disadvantages.
Because corneal tissue has a shorter radius of curvature compared with sclera, the placement of a large corneal patch on the scleral bed usually results in a segment of raised tissue.[
] Moreover, developing countries may not have the resources to harvest and use these materials, due to inappropriate facilities, lack of eye care specialists and sterilization services.
6.6 Conjunctival flaps
Conjunctival flaps are useful for covering melted or necrotic areas of sclera by providing a vascularized tissue which delivers nutrients and factors for healing.[
] post-operative infections, and hypersensitive reactions, and benefits from conjunctival flaps as unlike other surgical options conjunctiva comes with a good vascular supply to relieve ischemia. Conjunctival flap surgeries do not usually require donor tissue and can cover a wide area.[
] Conjunctival flaps have also shown benefit for scleromalacia following pterygium excision with tenonplasty.
The tarsoconjunctival pedicle flap, conjunctiva-Müller muscle pedicle flap can optimally revascularize the area affected by scleral necrosis but can cause ptosis, retraction of the eyelid, fornix shortening and eyelid margin deformities are some of the complications seen, for which a secondary flap separation procedure may be necessary.[
Rotational tarsoconjunctival flaps have been successfully used in patients with chemical ocular injury and exposed orbital implants, as well as autoimmune necrotizing scleritis. The superior tarsal muscle is easily incorporated into the pedicle flap because it is adherent to the conjunctiva and easily separated from the levator aponeurosis.[
Conjunctiva–Muller muscle flaps cover the necrotic areas with healthy conjunctival tissue, allowing for secondary epithelialization of the graft. The Muller muscle also provides tectonic support to the patch graft. Because of the pedicle, less aggressive immunotherapy may be indicated if a patch graft is supported with a conjunctiva–Muller muscle flap.[
Conjunctival flaps allow for larger surface coverage which may not be treated by other grafts or transplants. They also effectively control corneal inflammation and pain, and do not require donor tissue. This along with its comparative ease of procedure makes this technique a good option for scleral thinning.[
Tarsoconjunctival pedicle flaps and conjunctiva-Müller muscle pedicle flaps are associated with ptosis, retraction of the eyelid, fornix shortening and eyelid margin deformities.
6.7 Tenon’s capsule flap (Tenonoplasty)
Involve the transposition of tenon tissue, a fascial sheath below the conjunctiva extending from the limbus to the optic nerve, over a nearby scleral or corneal defect, schematic drawing of the surgical procedure can be seen in Fig. 4. Tenon flaps are seldom used alone long term for scleral thinning as they can only provide a bridge for limbus and conjunctival cells, which are often too compromised to heal over the flap. Teping and Reim mentioned needing additional epithelial grafts to cover defects post tenonplasty in ocular burns patients.[
] Since, tenonplasty has been used in conjunction with oral buccal mucosa grafts for treatment of burns induced scleral melting. It has also been used with conjunctiva to treat scleromalacia following pterygium surgery.[
Fig. 4A) The Tenon’s tissue is separated from globe with blood vessels intact, then Tenon’s flap is advanced and rotated and sutures to the sclera or cornea. B) Fibrin glue is then used to increase the area of the attachment of the flap.
Tenon tissue flaps are easily prepared and do not require additional donor site preparation. Considering the abundant vasculature of this autologous flap, it has a better graft survival rate and a lowered post-operative immune response, negating the need for immunosuppressants.[
] Tutoplast pericardium patch graft (Innovative Ophthalmic Products, Inc., Costa Mesa, CA, USA), supplied by IOP Ophthalmic in the United Kingdom, is a dehydrated, processed pericardium from human donor tissue that is converted into a multidirectional, collagen tissue matrix.[
] Having attributes of 400-µm thickness, easy storage capability and long shelf life, tutoplasty is used for tectonic support and as an epithelialization substrate.[
] tutoplasty demonstrated appreciable safety profile and proved its suitability as a patch graft material for implant exposure. Tutoplast is also documented for scleral bucking and melting following strabismus repairs, with positive results.[
M. Alkharashi, A.F. Dagi, L.R. Dagi. Pericardial patch graft repair of severe localized scleral thinning encountered during strabismus surgery, Journal of American Association for Pediatric Ophthalmology and Strabismus {JAAPOS} 21(2) (2017) 156-156. e1.
] Pericardium tends to melt over extended follow-up, which makes it only a temporary solution for scleral thinning.
6.9 Dermis graft
The dermis fat graft can be used in isolation or as a secondary implant option alongside allogenic grafts. This autologous graft technique uses dermis with adjacent subcutaneous fat which supports tissue growth, spontaneous re-epithelization, and hassle-free conjunctiva closure.[
] reported a case of 30-year-old female with absolute glaucoma status post-evisceration, who developed recurrent orbital implant exposure and scleral melting that was successfully treated using secondary dermis fat graft implant. Maurellio et al., reported long-term success using half-thickness dermal grafts in 8–10 patients who had otherwise failed initial attempts to curtail their scleral melting.
Advantages.
Dermis fat grafts allow for revascularization, procedure ease, relatively low post-operative immunological response, suitable material thickness to cover the affected area, and a reduced risk of fat atrophy.
Disadvantages.
Maurellio et al., noted the graft thinned and retracted over time in all patients but did not result in need to re-operate, although this may be a particular issue for the elderly in future. If hair is on the graft, this can cause chronic irritation. Donor site complications include hypertrophic scars and infection.
6.10 Cadaveric dura mater graft
Commercially prepared and sterilized sheets of cadaveric dura mater are obtained from human autopsy specimens and was first used for patch grafting for treatment of scleromalacia perforans in 1992.[
] The material is packaged as a rectangular flat sheet of dehydrated cadaveric dura mater, terminally sterilized with gamma-irradiation for single use. It has a stiff consistency which allows the surgeon to carefully trim the material prior to rehydration. Once moistened with balanced saline, the consistency of the material is similar to sclera. The dura uniform thickness and can be placed close to the limbus without creating dellen, a problem associated with thick scleral grafts. It has also had successful use as a tectonic graft for scleromalacia post complex retinal detachment repair.[
Good tectonic strength, good elasticity, low risk of dellen formation, and good compatibility and similarity with sclera.
Disadvantages.
Associated with transmission of infectious diseases leading to iridocyclitis. There has been reported cases of Creutzfeldt-Jakob Disease transmission through cadaveric dura graft.[
R.W. Enzenauer, R.J. Enzenauer, V.B. Reddy, F.M. Cornell, S. West. Treatment of scleromalacia perforans with dura mater grafting, SLACK Incorporated Thorofare, NJ. 1992. 829-832.
] used temporalis fascia for exposure of porous polyethylene (Medpor) sphere implants, wherein grafting successfully closed the defect without re-exposure in three out of four patients studied. Use of autogenous periosteum has also been reported[
] and offers advantages over other tissues as a tectonic graft for necrotizing scleritis as a strong, vascular, easy to harvest and handle material that is not subject to immunological rejection or systemic complications.
A biodegradable bioengineered implant, Ologen™ collagen matrix (OCM, Aeon Astron Europe B.V., Leiden, The Netherlands), implant has also been used as a graft tissue.[
] OCM helps the ocular surface stay flat and regular, and fills the scleral bed easily. OCM consists of lyophilized porcine atelocollagen (>90 %) and lyophilized porcine glycosaminoglycan (<10 %) with pore sizes of 10–300 μm. When placed into the subconjunctival space, the porous structure guides conjunctival fibroblasts and myoblasts to proliferate randomly and secrete connective tissue in the form of a loose matrix during the wound healing process which reduces scar formation and wound contraction. The device completely degrades within 90–180 days, leaving behind a loose alignment of collagen fibers. OCM is mainly used in glaucoma filtering surgeries due to its porous and spongy structure that permits percolation of aqueous material during wound healing.
8. Graft rejection and management
Graft rejection is one of the most difficult complications of scleral thinning, and manifests as an immunologic response against the donor tissue.[
] Management of graft rejection and likelihood of its reversibility is largely dependent on the site affected. While first line management requires use of topical steroids and/or corticosteroids, calcineurin inhibitors like cyclosporin A and tacrolimus are used when corticosteroids are contraindicated.[
] Educating transplant patients on early symptom detection and to seek urgent help at first signs is imperative for preventing adverse outcomes.
The recent surge in surgical management strategies for scleral thinning recalcitrant to medical treatments has provided novel solutions for a complication which once caused considerable morbidity. While surgical options were once constricted to allogenic or autologous patch graft materials, newer innovations include the use of biodegradable collagen matrix and tutoplast as graft tissues. As efficacy of these treatments build in the literature, graft rejections, dehiscence, and necrosis are complications which should be continually reported to guide the optimal selection of grafts. Approaches to scleral thinning should be considered based on the severity of scleral melting and underlying pathogenesis of disease.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Appendix A. Supplementary data
The following are the Supplementary data to this article:
Randomized trial comparing multilayer amniotic membrane transplantation with scleral and corneal grafts for the treatment of scleral thinning after pterygium surgery associated with beta therapy.
M. Alkharashi, A.F. Dagi, L.R. Dagi. Pericardial patch graft repair of severe localized scleral thinning encountered during strabismus surgery, Journal of American Association for Pediatric Ophthalmology and Strabismus {JAAPOS} 21(2) (2017) 156-156. e1.
R.W. Enzenauer, R.J. Enzenauer, V.B. Reddy, F.M. Cornell, S. West. Treatment of scleromalacia perforans with dura mater grafting, SLACK Incorporated Thorofare, NJ. 1992. 829-832.
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