Failure of amniotic membrane transplantation in the treatment of acute ocular burns

Therapeutic effects of a novel venom abstract (ZK002) solution in an alkali-burned corneal wound-healing model

Purpose

Corneal alkali burns can progress to corneal epithelial defects, inflammation, scarring, and angiogenesis, potentially leading to blindness. Therefore, we examined the therapeutic effects of a novel ophthalmic solution (ZK002) on wound healing in alkali-burned rat corneas.

Methods

In this study, we attempted to treat alkali-exposed rat corneas using topical application of either an ophthalmic solution with ZK002 or an anti-vascular endothelial growth factor agent for 14 days. We evaluated corneal edema, corneal neovascularization area, and histological changes. We also assessed the inflammatory (MMP-9, MMP-2, and interleukin-1β) and angiogenic (vascular endothelial growth factor receptor 2, VEGFR2) markers. Levels of inflammatory (matrix metalloproteinase (MMP)-9, MMP-2, and interleukin-1β), profibrotic (α-smooth muscle actin, α-SMA; transforming growth factor-β2,TGF-β2), and angiogenic (vascular endothelial growth factor-receptor 2, VEGFR2) factors, as well as peroxisome proliferator-activated receptor γ (PPARγ) mRNA expression, were measured.

Results

The analyses showed that alkali exposure caused an increase in corneal edema and fibrosis with corneal neovascularization. The accumulation of α-smooth muscle actin-positive myofibroblasts and the deposition of transforming growth factor-β2 on the alkali-exposed corneas were noted on day 14. The mRNA expression levels of interleukin-1β, MMP-9, MMP-2, VEGFR2, and profibrotic factors were decreased in the ZK002 group compared with the control group during the early period of corneal alkali burns on day 14. However, the expression level of PPARγ mRNA was increased in the ZK002 group.

Conclusions

ZK002 decreased the fibrotic reaction and prevented neovascularization in the cornea after an alkali burn. Therefore, the novel ophthalmic solution ZK002 could be a potentially promising therapeutic clinical treatment for corneal wound healing.

Clinical outcomes of vacuum-dehydrated amniotic membrane (Omnigen) mounted on contact lens (Omnilenz) in eyes with acute chemical eye injuries

BACKGROUND

Omnigen is a vacuum-dehydrated amniotic membrane transplant. It can be delivered to the eye pre-mounted on a special bandage contact lens (Omnilenz) that enables its application without the need for sutures or glue; the aim of this study is to evaluate the short-term clinical outcomes of Omnilenz-Omnigen complex in eyes with acute chemical injury (CEI).

METHODS

A prospective interventional study included patients with different grades of acute CEI attending the casualty between July 2021 and November 2022. All patients received first aid measures followed by the application of Omnilenz-Omnigen within the first 2 days. Patients were followed up for at least 1 month. Primary outcomes include epithelial defect and limbal ischemia. Secondary outcomes include best-corrected visual acuity (BCVA) and tolerability.

RESULTS

The study included 23 eyes of 21 patients with acute CEI mostly due to alcohol (34.8%). After the 1st application, the size of the epithelial defect showed a statistically significant reduction (p = 0.016) with improvement in BCVA (p < 0.001). Restoration of the limbal vascularity was obtained in 56.5% of the eyes. Repeated application of Omnilenz was required in 5 eyes (21.7%). The size of the epithelial defect was reduced after the second application (p = 0.504) with improved BCVA (p = 0.185). After 1st month, complete epithelial healing was achieved in all the eyes. Mild limbal ischemia persists in 3 (13%) of the eyes. Final BCVA showed statistically significant improvement (p < 0.001). None of the patients develops any serious complications.

CONCLUSION

Omnilenz proved to be easy to apply and well tolerated by patients, with promising clinical outcomes.

Mustard Gas-Induced Ocular Surface Disorders: An Update on the Pathogenesis, Clinical Manifestations, and Management

PURPOSE

Mustard gas (MG) is a potent blistering and alkylating agent that has been used for military and terrorism purposes. Ocular surface injuries are common after exposure to MG. This review provides an update on the pathophysiology, ocular surface complications, and treatment options for MG-related ocular injuries.

METHODS

Required information was obtained by reviewing various databases such as Cochrane Library, Google Scholar, and PubMed until March 2022. Data were collected by using keywords: "mustard gas" OR "sulfur mustard" AND "eye" OR "cornea" OR "ocular complication" OR "keratitis" OR "keratopathy" OR "limbal stem cell deficiency" OR "dry eye."

RESULTS

Chronic intracellular toxicity, inflammation, and ischemia have been shown to play an essential role in the pathogenesis of MG injury. Ocular surface injuries can have acute, chronic, and most distinctly a delayed-onset presentation leading to various degrees of limbal stem cell deficiency. To date, no treatment has been agreed on as the standard treatment for chronic/delayed-onset MG keratopathy. Based on the authors' experience, we propose a management algorithm for MG-related ocular surface injuries involving optimization of ocular health, anti-inflammatory therapy, and if needed surgical interventions. The management of chronic and delayed-onset presentation remains challenging.

CONCLUSIONS

MG keratopathy is a unique form of chemical injury which can lead to a range of ocular surface pathologies. Long-term anti-inflammatory therapy even in patients with seemingly mild disease may potentially reduce the likelihood of the development of more severe delayed-onset disease.

Visual Acuity and Number of Amniotic Membrane Layers as Indicators of Efficacy in Amniotic Membrane Transplantation for Corneal Ulcers: A Multicenter Study

BACKGROUND

To evaluate new indicators in the efficacy of amniotic membrane transplantation (AMT) for non-healing corneal ulcers (NHCUs).

METHODS

Retrospective, multicenter study. In total, 223 AMTs for NHCU in 191 patients were assessed. The main outcomes studied were the success rate of AMT (complete re-epithelization), postoperative visual acuity (VA) gain, and number of AM layers transplanted.

RESULTS

The overall AMT success rate was 74.4%. In 92% of our patients VA stability or improvement. Postoperative VA was significantly higher than preoperative VA in the entire cohort (p < 0.001) and in all etiological groups of ulcers (post-bacterial, p ≤ 0.001; post-herpetic, p ≤ 0.0038; neurotrophic ulcers, p ≤ 0.014; non-rheumatic peripheral, p ≤ 0.001; and ulcers secondary to lagophthalmos and eyelid malposition or trauma, p ≤ 0.004). Most participants (56.5%) presented a preoperative VA equal to or less than counting fingers (≤0.01). Of these, 13.5% reached a postoperative VA equal to or better than legal blindness (≥0.05) after AMT. A higher success rate was observed in the monolayer than in the multilayer AMT (79.5% and 64.9%, respectively; p = 0.018). No statistically significant values were found between the number of layers transplanted and VA gain (p = 0.509).

CONCLUSION

AMT is not only beneficial in achieving complete re-epithelialization in NHCUs but also in improving postoperative VA; these improvements are independent of etiologies of ulcers. Furthermore, the use of monolayer AMT seems to be a more appropriate option than multilayer AMT for NHCU since the multilayer AMT did not present better outcomes (success rate and VA gain) compared to monolayer AMT in the different types of ulcers studied.

Amniotic membrane transplant in acute ocular surface burns in Western India: A tertiary eye care center study

Purpose

To evaluate the outcomes of early amniotic membrane transplant (AMT) in acute ocular surface burns using Dua's classification.

Methods

In this retrospective analysis conducted at a tertiary eye care center in Western India. We included 27 eyes of 24 patients from May 2014 to May 2019 who underwent AMT within 2 weeks post insult along with medical treatment for acute ocular surface burns using Dua's classification for grading on presentation. Post-operative assessment for ocular surface epithelization, corneal vascularization, symblepharon formation, and visual outcome at the time of complete epithelization was done.

Results

Eight, seven, three, and nine eyes with grade III, IV, V, and VI, respectively, were included in the study. The mean duration of the presentation was 5.5 ± 3.6 days, with the mean follow-up of 4.83 ± 2.2 months. Alkali burn (62.96%, 17/27 eyes) was the commonest. The mean epithelization time was 5.80 ± 2.92 weeks. Corneal vascularization for >6 clock hours was seen in 52.38% (11/21 eyes with vascularization). Symblepharon was seen in 55.55% (15/27 eyes). Vision improvement and corneal vascularization to a lesser extent (<6 clock hours) was observed in Group A (grades III and IV) as compared to group B (grades V and VI) and found to be significant (P-value = 0.031, P value = 0.007, respectively).

Conclusion

Amniotic membrane grafting is a useful aid in moderate grades of acute ocular surface burns with an important adjunct role in severe cases.

Heparin-Modified Amniotic Membrane Combined With Growth Factors for Promoting Corneal Wound Healing After Alkali Burn

Ocular chemical burns are potentially blinding ocular injuries and require urgent management. Amniotic membrane (AM) transplantation is an effective surgical treatment, one of the reasons is because AM is a rich source of growth factors that can promote epithelialization and wound healing. However, growth factors will be gradually lost and insufficient after preparation process and long-time storage, leading to unsatisfactory therapeutic effects. Herein, we present a modified AM (AM-HEP) for the supplement and sustained release of growth factor by surface grafting heparin for treatment of ocular chemical burns. Heparin grafting rate and stability, microstructure, physical property, and sustained release of epithelial growth factor (EGF) of AM-HEP were characterized. Biocompatibility and ability to promote corneal epithelial cell growth and migration were evaluated and compared with a biological amnion, which is available on the market in vitro. The therapeutic effects of AM-HEP combined with EGF (AM-HEP@EGF) in vivo had been evaluated in a model of mouse corneal alkali burn. The results indicated that heparin was introduced into AM and maintain stability over 3 weeks at 37°C. The modification process of AM-HEP did not affect microstructure and physical property after comparing with non-modified AM. EGF could be combined quickly and effectively with AM-HEP; the sustained release could last for more than 14 days. AM-HEP@EGF could significantly promote corneal epithelial cell growth and migration, compared with non-modified AM and control group. Faster corneal epithelialization was observed with the transplantation of AM-HEP@EGF in vivo, compared with the untreated control group. The corneas in the AM-HEP@EGF group have less inflammation and were more transparent than those in the control group. The results from in vitro and in vivo experiments demonstrated that AM-HEP@EGF could significantly enhance the therapeutic effects. Taken together, AM-HEP@EGF is exhibited to be a potent clinical application in corneal alkali burns through accelerating corneal epithelial wound healing.

Management Strategies of Ocular Chemical Burns: Current Perspectives

Ocular chemical burns are absolute ophthalmic emergencies and require immediate management to minimize devastating sequelae. Management of alkali and acid burns is started at the scene of the accident by copious irrigation. Treatment is directed at improving epithelial integrity and stromal stability, reduction of undue inflammation, and prevention or timely management of complications. To ascertain the best possible outcome, numerous biological medications and surgical interventions have been merged into conventional therapeutic regimens. These include autologous and umbilical cord serum preparations, platelet-rich plasma, amniotic membrane transplantation, limbal stem-cell transplantation, and anti-angiogenic agents.

Allogenic Simple Limbal Epithelial Transplantation Versus Amniotic Membrane Grafting in the Early Management of Severe-Grade Ocular Chemical Injuries-A Retrospective Comparative Study

PURPOSE

To compare outcomes of management in the early stage of severe chemical injury (grade 4 and worse; Dua classification) with amniotic membrane grafting (AMG) alone vs allogenic simple limbal epithelial transplantation (alloSLET).

DESIGN

Retrospective comparative interventional case series.

METHODS

Retrospective comparative interventional series. Records of patients with severe ocular chemical injury who underwent AMG alone (between 2009 and 2013) vs alloSLET (between 2013 and 2017) were analyzed for grade of injury, time of and interventions for epithelial healing, ocular surface status post healing (grade of symblepharon, and limbal stem cell deficiency [LSCD]), and type of and need for interventions in the chronic stage.

RESULTS

Among patients presenting in early stage of severe chemical injury, 38 eyes (median age 11 years) managed with AMG alone were compared with 39 eyes (median age 8 years) managed with alloSLET. The mean time of presentation post injury was 33.85 ± 27.5 and 40.6 ± 23.5 days in the AMG and alloSLET group, respectively. The rate of epithelial healing was faster in the alloSLET group and the difference was noted to be statistically significant (odds ratio [OR] 0.966, P = .001). Similarly, the lower occurrence of LSCD (OR 0.137, P = .004) and need for keratoplasty (OR 0.093, P = .003) favored alloSLET over AMG. Final best-corrected visual acuity of >20/200 was achieved in 39.4% and 53.8% in the AMG and alloSLET groups, respectively.

CONCLUSION

AlloSLET helps in faster epithelialization of the surface, thus reducing the need for subsequent surgeries in the chronic stage and aiding faster visual rehabilitation. The outcomes of alloSLET appear superior to amniotic membrane grafting alone and should be considered in eyes with grade 4 and above (Dua classification) chemical injuries in the early stage.

Hyperdry human amniotic membrane application as a wound dressing for a full-thickness skin excision after a third-degree burn injury

Background

Severe burn injuries create large skin defects that render the host susceptible to bacterial infections. Burn wound infection often causes systemic sepsis and severe septicemia, resulting in an increase in the mortality of patients with severe burn injuries. Therefore, appropriate wound care is important to prevent infection and improve patient outcomes. However, it is difficult to heal a third-degree burn injury. The aim of this study was to investigate whether hyperdry human amniotic membrane (HD-AM) could promote early granulation tissue formation after full-thickness skin excision in third-degree burn injury sites in mice.

Methods

After the development of HD-AM and creation of a third-degree burn injury model, the HD-AM was either placed or not placed on the wound area in the HD-AM group or HD-AM group, respectively. The groups were prepared for evaluation on postoperative days 1, 4 and 7. Azan staining was used for granulation tissue evaluation, and estimation of CD163, transforming growth factor beta-1 (TGF-β1), vascular endothelial growth factor (VEGF), CD31, alpha-smooth muscle actin (α-SMA) and Iba1 expression was performed by immunohistochemical staining. Quantitative reverse-transcription polymerase chain reaction (PCR) was used to investigate gene expression of growth factors, cell migration chemokines and angiogenic and inflammatory markers.

Results

The HD-AM group showed significant early and qualitatively good growth of granulation tissue on the full-thickness skin excision site. HD-AM promoted early-phase inflammatory cell infiltration, fibroblast migration and angiogenesis in the granulation tissue. Additionally, the early infiltration of cells of the immune system was observed.

Conclusions

HD-AM may be useful as a new wound dressing material for full-thickness skin excision sites after third-degree burn injuries, and may be a new therapeutic technique for improving the survival rate of patients with severe burn injuries.

Mapping of proteomic profile and effect of the spongy layer in the human amniotic membrane

The graft of human amniotic membrane (HAM) contributes to the healing of corneal perforating ulcers and so to save a large number of eyes suffering of severe chemical burns. This biological material is used for the treatment of ocular surface diseases because of its capacity to reduce inflammation and promote a quicker wound healing. For clinical use, the HAM is denuded from its spongy layer, but this layer can be an important source of growth factors which promote re-epithelialization. The aim of our study is to provide a general view of protein expression of the HAM and the spongy layer and therefore to determine if the spongy layer and/or a specific part of HAM have a beneficial role in the process of wound healing in patients with corneal ulcers. For this study, human placentas were obtained from healthy women after vaginal delivery or caesarean section after signing the consent form. Mapping of protein expression is done by dividing the placenta in 2 equal parts, one with spongy layer and another without (conventional HAM). Each part is also divided in 3 zones depending on the distance from the umbilical cord. The proteomic analysis was done by ELISA, targeting growth factors (EGF, HGF, KGF, NGF and TGF-beta1) and pro inflammatory cytokine TNF-α in the HAM without spongy layer and in the spongy layer. In this study we observed significant difference in the total amount of protein extract between the different donors. We do not observe a significant difference in the growth factor level between the conventional HAM and the spongy layer. No variation was observed in the expression of HGF, KGF and NGF in different zone of HAM and neither between conventional HAM and spongy layer in each zone. (*p value < 0.05, **p value<0.01,***p value < 0.001). We do detect very low dose of TNF-α and no correlation with the amount of growth factors. In our study we demonstrated that keeping the spongy layer in conventional method of handling HAM can add more GF, and so probably have a positive affect the wound healing process. Variation in some growth factors expression has been observed between the placentas and therefore this may explain the variation in clinical results. No indicator for the selection of placentas with a higher rate of growth factor was found.

Tenonplasty Combined With Amniotic Membrane Transplantation for Patients With Severe Ocular Burns Induced Anterior Segment Necrosis

This article describes a novel surgical technique for successful repair of intractable corneoscleral necrosis caused by severe ocular burns. In this prospective case series, 19 eyes of 15 consecutive patients with sectional scleral necrosis and persistent corneal epithelial defects were treated with tenonplasty and amniotic membrane transplantation. The main outcome measure was the stability of the ocular surface after reepithelialization and repair of defects. All patients underwent successful combined surgery involving tenonplasty and amniotic membrane transplantation, in which the conjunctival and corneal surfaces were reconstructed. The interval from injury to surgery was 37.4 ± 24.5 days (3-91 days), and the ocular surfaces became stabilized in 82.2 ± 35.4 days (26-156 days, median 87 days). At the final visit, all cases presented with corneal opacity and neovascularization to various degrees. The best-corrected visual acuity decreased from 2.83 ± 1.02 LogMAR preoperatively to 2.87 ± 1.31 LogMAR postoperatively. The results imply that tenonplasty combined with amniotic membrane transplantation could provide vascular supply to the ischemic sclera, repair defects in the conjunctiva, and promote corneal reepithelialization, thus facilitating ocular surface stabilization after burns.

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

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

[Not Available]

Chemical corneal burns are a common pathology. Those with strong bases penetrate deeply into the anterior segment and are particularly severe. We report the case of a patient suffering from corneal perforation secondary to an accidental projection of soda, and we propose to discuss the clinical and therapeutic particularities.

Amniotic Membrane Transplantation in Acute Severe Ocular Chemical Injury: A Randomized Clinical Trial

PURPOSE

To compare the outcomes of conventional medical treatment vs combined medical treatment and amniotic membrane transplantation (AMT) in the management of patients with Roper-Hall grade IV ocular chemical injury.

DESIGN

Randomized, parallel-controlled clinical trial.

METHODS

Setting: Single tertiary referral hospital.

PATIENTS

Sixty eyes of 60 patients with Roper-Hall grade IV ocular chemical injury with a minimum follow-up of 12 months were enrolled in the study.

INTERVENTION

Patients were randomly assigned to 2 groups: Group 1 (30 eyes) received topical preservative-free lubricating gel and drops, chloramphenicol, betamethasone, homatropine, oral vitamin C, and doxycycline; Group 2 (30 eyes) received amniotic membrane transplant (AMT) on the entire ocular surface in addition to the medical treatment provided in Group 1.

OUTCOME MEASURES

The main outcome measure was time to complete corneal epithelialization. Secondary outcome measures were best-corrected visual acuity (BCVA) and neovascularization in the central 5 mm of the cornea.

RESULTS

Mean follow-up time was 20.3 ± 2.5 months (range 13-24 months). Corneal epithelial defects healed within 72.6 ± 30.4 (21-180) days in Group 1 vs 75.8 ± 29.8 (46-170) days in Group 2 (P = .610). Mean BCVA was 2.06 ± 0.67 (0.4-2.6) logMAR vs 2.06 ± 0.57 (1-2.9) logMAR in Groups 1 and 2, respectively (P = .85). Group 1 developed more central corneal neovascularization (22 eyes; 73.3%) compared to Group 2 (16 eyes; 53.3%); however, it was not statistically significant (P = .108).

CONCLUSIONS

In comparison to conventional medical therapy, combined amniotic membrane transplantation and medical therapy does not accelerate corneal epithelialization or affect final visual acuity in severe chemical injuries.

Algorithmic approach to management of acute ocular chemical injuries-I's and E's of Management

Ocular chemical injuries are associated with significant morbidity leading to vision loss and ocular surface damage. Appropriate management and intervention in the acute stage dictates the final outcome as well as the prognosis for visual rehabilitative procedures in chronic stage. Classifying the parameters to be addressed in the acute stage and providing an algorithmic approach for managing the alterations in each of them will facilitate the primary goal of ensuring epithelialization of the ocular surface. Broadly categorizing them into the I's and E's (inciting agent, inflammation, epithelial defect, ischemia, exposure and intraocular pressure) and treating each will directly and/or indirectly influence re-epithelialization of the ocular surface, which in turn will reduce or prevent the various detrimental sequelae of ocular chemical injury.

Comparison of Collagen Cross-Linking and Amniotic Membrane Transplantation in an Experimental Alkali Burn Rabbit Model

PURPOSE

To compare the effects of collagen cross-linking (CXL) and amniotic membrane transplantation (AMT) on acute corneal alkali burns.

METHODS

After establishment of an alkali burn model, 32 rabbits were divided into 4 groups: control group, AMT group, CXL group, and AMT + CXL (combined) group. Clinical parameters, including epithelial wound, opacity, ulceration, and neovascularization, were evaluated on postinjury days 1, 7, 14, and 18. Histological parameters were examined in hematoxylin/eosin (H&E) and Masson trichrome-stained corneal sections. Immunohistochemical analyses, including a terminal deoxynucleotidyl transferase-mediated biotin-deoxyuridine triphosphate nick-end labeling assay and cluster of differentiation 68 (CD68) labeling, were performed to determine the apoptotic index and macrophage activation.

RESULTS

On postinjury day 18, the epithelial wound of AMT {4.08% [interquartile range (IQR), 0.68%-5.22%]}, CXL [1.84% (IQR, 0.01%-3.89%)], and combined [3.44% (IQR, 0.01%-4.36%)] groups were significantly lower than the control [15.23% (IQR, 9.86%-23.06%)] group (P = 0.003). No significant difference was detected between the groups in terms of opacity (P = 0.303). Neovascularization was the least severe in the CXL group [16.18% (IQR, 8.39%-21.28%)] and the most severe in the AMT [34.47% (IQR, 17.71%-62.77%)] and combined [35.12% (IQR, 31.96%-59.98%)] groups on day 18 (P = 0.033). Significant increases in the apoptotic index and CD68 labeling were detected in the CXL and combined groups compared with those in the control group (P = 0.047 and P = 0.001, respectively).

CONCLUSIONS

CXL treatment is an effective adjuvant treatment for promoting reepithelialization, reducing inflammation and neovascularization, and preventing ulceration in acute alkali burns. Providing AMT after suppressing inflammation may be a more effective treatment.

Comparative proteomic analysis of amnion membrane transplantation and cross-linking treatments in an experimental alkali injury model

PURPOSE

In this study, by using a two-dimensional (2D) electrophoresis-based experimental approach, we aimed at understanding the nature of alkali injuries and the underlying mechanisms. A secondary aim was to compare the effects of cross-linking (CXL) and amnion membrane transplantation (AMT) on corneal protein compositions at the end of the early repair phase after injured with alkali.

METHOD

The right corneas of 24 rabbits were injured with a 1 N solution of NaOH. Groups were formed based on the adjuvant therapies as (1) healthy group, (2) control group, (3) CXL group, (4) AMT group. In addition to the therapies, a conventional medical treatment was applied to all groups. Left eyes were used as within-subject healthy corneas (1). The corneas were excised at day 21, and a comparative proteomic analysis was performed using 2D gel electrophoresis coupled with MALDI-TOF/TOF.

RESULT

2D gel electrophoresis revealed the presence seven protein spots whose abundance changed among the groups. Those proteins were SH3 domain-binding protein, plant homeodomain finger protein 23, S100 calcium binding protein A-11(S100 A11), keratin type 2 cytoskeletal 1 and 2, transketolase and glyceraldehyde 3-phosphate dehydrogenase. Ingenuity pathway analysis predicted that the observed changes may be linked to a central metabolic pathway, transforming growth factor beta 1. Canonical pathway analysis focused our attention to two different pathways, namely nicotinamide adenine dinucleotide repair pathway and non-oxidative branch of pentose phosphate pathway.

CONCLUSION

Our results shed some light onto the molecular mechanisms affected by alkali injury and adjuvant treatments. Further research is needed to propose medically significant target molecules that may be used for novel drug developments for alkali injury.

Effect of 1- and 6-Hour-Delayed Corneal Collagen Cross-Linking on Corneal Healing in a Rabbit Alkali-Burn Model: Clinical and Histological Observations

PURPOSE

To study the effect of 1- and 6-hour-delayed corneal collagen cross-linking (CXL) on wound-healing of experimental alkali burns of the cornea.

METHODS

Twenty-four albino rabbits were used. Alkali burns were created using 1 M NaOH. The animals were divided randomly into 2 groups: group 1 (control group, n = 6) and group 2 (experimental group, n = 18). The experimental group was further divided into 3 subgroups as follows: group 2A, untreated (non-CXL) subgroup; group 2B, 1-hour-delayed CXL treatment subgroup; and group 2C, 6-hour-delayed CXL treatment subgroup. All rabbits were examined periodically for 21 days after treatment and then killed. The corneas were excised and histologically examined.

RESULTS

Corneal ulceration, edema, and opacity scores were 4.0 ± 1.64, 1.6 ± 0.65, and 3.5 ± 1.21 in group 2A, 1.5 ± 1.76, 1.3 ± 0.87, and 3.1 ± 1.12 in group 2B, and 2.0 ± 1.90, 1.5 ± 0.79, and 3.3 ± 1.09 in group 2C, respectively. These scores were significantly less in groups 2B and 2C than in group 2A (P = 0.023, P = 0.043, and P = 0.034, respectively). Corneal epithelialization, evident upon staining, was best in group 2B and worst in group 2A (P = 0.012). Histopathology revealed that destruction of corneal collagen fibers and infiltration of inflammatory cells into corneal tissue were reduced in groups 2B and 2C compared with group 2A.

CONCLUSIONS

We found that CXL treatment exerted positive effects on severe alkali-induced corneal burns. However, the effects were more pronounced in the 1-hour treatment group. We believe that CXL treatment may be a possible treatment for corneal alkali burn.

Treatment of acute ocular chemical burns

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

Antioxidant properties of amniotic membrane: novel observations from a pilot study

OBJECTIVE

Amniotic membrane (AM) is used to manage various debilitated ocular surface conditions. The impact of oxidative stress and free radicals on the ocular surface is increasingly being recognized. Hyaluronic acid (HA) has anti-inflammatory properties and is abundantly present in AM. In this in vitro pilot study, we investigated the potential of AM for intrinsic free radical scavenging properties.

METHODS

Strips of AM were incubated in sealed tubes with hydrogen peroxide (H2O2). After being sonicated, uptake of reactive oxygen species (ROS) was measured by the Amplex Red Hydrogen Peroxide/Peroxidase assay. For comparison, 1630 kDA HA was used.

RESULTS

There was uptake of ROS by all AM samples, which decreased with increasing concentrations of H2O2. Mean ROS uptake for 5 different AMs at 1 hour was significantly greater for 50 μM (83%; SD 11.7, SEM 5.23) compared with 100 μM (67%; SD 20.48, SEM 9.16; p = 0.028; 95% CI 2.8-29.2). The HA comparison group showed similar uptake and trend.

CONCLUSION

This pilot study demonstrates that AM is able to remove ROS from its environment. Demonstrating total antioxidant capacity in AM provides evidence for use as a free radical scavenger. The antioxidant properties of AM and the contribution from HA require more research.

Preparation, indications and results of human amniotic membrane transplantation for ocular surface disorders

In comparison with other biologic tissues used as reconstructive grafts, the amniotic membrane has the advantage that it is thinner and better tolerated by the patient. Amniotic membrane, when appropriately preserved, can be used as a substrate replacement, such that host cells can migrate into the membrane to form new and healthy tissue. The amniotic membrane is the deeper layer of the fetal membrane; it is avascular, multilayered tissue with antiangiogenic, antiscarring and anti-inflammatory properties. Since it does not express antigens of histocompatibility, the membrane is never rejected by the receiving tissues. In addition, the beneficial effects of reducing inflammation and neovascularization persist for a long time, if properly cryopreserved.

Amniotic Membrane Transplantation in Treatment of Persistent Corneal Ulceration after Severe Chemical and Thermal Eye Injuries

Purpose

To analyze results of amniotic membrane transplantation (AMT) in treatment of corneal ulceration after severe chemical and thermal injuries.

Methods

Analysis of 55 AMT in 53 patients (53 eyes) with corneal ulceration and limbal deficiency 180–360° of the limbus after grade 4–6 (Dua classification, 2001) chemical and thermal injuries was performed. Mean terms of the operation were 46.1 ± 46.4 days after the injury (range 8–181 days). Preoperative visual acuity (VA) was <0.01 in 33/53 patients (62.3%). Mean follow-up period was 8.8 ± 10.1 months (range 1.5–46 months).

Results

Further corneal ulceration was prevented in 54/55 cases (98.1%), cornea epithelialized after 42/55 AMT (76.3%). Mean terms of corneal epithelialization were 24.2 ± 26.7 days after AMT (range 6–123 days). Corneal defect recurred in 3/42 successful cases (7.1%). Limbal deficiency of different extent with subsequent corneal conjunctivalization developed in all successful patients. The VA was ≥0.01 (range 0.01–1.0) in 23/42 patients (54.8%) with corneal epithelialization. The VA at the last visit was improved on 2 and more lines on the eye chart compared to preoperative VA in 15/42 patients with corneal epithelialization (35.7%), did not change in 18/42 successful patients (42.9%), and decreased on one line in 9/42 of these patients (26.2%). Symblepharon developed in 23/42 successful patients (54.7%).

Conclusions

Amniotic membrane transplantation may stop ulceration and promote corneal epithelialization in the majority of patients with the most severe chemical or thermal eye injuries in case of timely application of the operation and adequate fixation of the AMT graft.

Course and outcome of accidental sodium hydroxide ocular injury

PURPOSE

To evaluate the course and outcome of patients with accidental ocular alkali burns.

DESIGN

Prospective, interventional case series.

METHODS

Study of a cohort of 16 patients (31 eyes) who sustained concomitant accidental sodium hydroxide ocular burns and received appropriate treatment at a tertiary care eye hospital in India. The patients were followed up for 1 year, and parameters including best-corrected visual acuity, epithelial defect area, conjunctival and limbal involvement, and injury-related complications were evaluated.

RESULTS

Severe sodium hydroxide exposure of a mean duration of 12 ± 2.5 minutes and delay in specialist eye care caused moderate to severe injury (grade II, 19% [n = 6]; grade III, 19% [n = 6]; grade IV, 10% [n = 3]; and grade VI, 52% [n = 16]). Median best-corrected visual acuity at presentation was 1.0 logarithm of the minimal angle of resolution (logMAR) units (range, 0.3 to 1.9 logMAR units), and at 1 year, it was 1.0 logMAR units (range, 0 to 1.9 logMAR units; P = .121). The median initial epithelial defect was 100 mm(2) (range, 18 to 121 mm(2)), which healed in all eyes by 3.5 months. Initial median limbal involvement was 12 clock hours (range, 3 to 12 clock hours), resulting in a residual limbal stem cell deficiency of 6 clock hours (range, 0 to 12 clock hours) at 1 year. Most common complications were glaucoma and cataract. Corneal ulcers developed in 2 eyes, and keratolimbal graft was performed in 1 patient. Grade VI injuries had significantly worse outcome than the lower-grade injuries.

CONCLUSIONS

The course and outcome of ocular alkali burns depends on effective first aid (including a thorough eyewash), age, initial grade of injury, response to treatment, prevention of secondary infection, and control of glaucoma. Despite appropriate treatment, these eyes responded poorly and carried a guarded visual prognosis.

Amniotic membrane transplantation for acute ocular burns

BACKGROUND

Ocular surface burns can be caused by chemicals (alkalis and acids) or by direct heat. Amniotic membrane transplantation (AMT) performed in the acute phase (day 0 to day 7) of an ocular surface burn is reported to relieve pain, accelerate healing and reduce scarring and blood vessel formation. The surgery involves applying a patch of amniotic membrane (AM) over the entire ocular surface up to the eyelid margins.

OBJECTIVES

To assess the effects of AMT on the eyes of people having suffered acute ocular surface burns.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2012, Issue 6), MEDLINE (January 1946 to June 2012), EMBASE (January 1980 to June 2012), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to June 2012), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 11 June 2012.

SELECTION CRITERIA

We included randomised trials of medical therapy and AMT applied in the first seven days after an ocular surface burn compared to medical therapy alone.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the risk of bias of included studies and extracted relevant data. We contacted trial investigators for missing information. We summarised data using risk ratios (RRs) and mean differences (MDs) as appropriate.

MAIN RESULTS

We included one RCT of 100 participants with ocular burns that were randomised to treatment with AMT and medical therapy or medical therapy alone. A subset of patients (n = 68) who were treated within the first seven days of the injury met the inclusion criteria and were included in the analysis. The remaining 32 eyes were excluded. The included subset consisted of 36 moderate (Dua classification II-III) and 32 severe (Dua classification IV-VI) ocular burns from alkali, acid and thermal injuries. In the moderate category, 13/20 control eyes and 14/16 treatment eyes had complete epithelialisation by 21 days. The RR of failure of epithelialisation by day 21 was 0.18 in the treatment group (95% confidence interval (CI) 0.02 to 1.31; P = 0.09). Mean LogMAR final visual acuities were 0.06 (standard deviation (SD) 0.10) in the treatment group and 0.38 (SD 0.52) in the control group, representing a MD of -0.32 (95% CI -0.05 to -0.59). In the severe category, 1/17 treatment and 1/15 control eyes were epithelialised by day 21. The RR of failure of epithelialisation in the treatment group was 1.01 (95% CI 0.84 to 1.21; P = 0.93). Final visual acuity was 1.77 (SD 1.31) in the treated eyes and 1.64 (SD 1.48) in the control group (MD 0.13; 95% CI -0.88 to 1.14). The risks of performance and detection biases were high, because treating personnel and outcome assessors could not be masked to treatment. There was also a high risk of bias in the visual outcomes of the moderate category, since mean visual acuity was significantly worse at presentation in the control eyes. This reduced confidence in the study findings.

AUTHORS' CONCLUSIONS

Conclusive evidence supporting the treatment of acute ocular surface burns with AMT is lacking. Heterogeneity of disease presentation, variations in treatment, undefined criteria for treatment success and failure, and non-uniform outcome measures are some of the factors complicating the search for clear evidence regarding this treatment.

Amniotic membrane traps and induces apoptosis of inflammatory cells in ocular surface chemical burn

PURPOSE

Severe chemical burns can cause necrosis of ocular surface tissues following the infiltration of inflammatory cells. It has been shown that amniotic membrane transplantation (AMT) is an effective treatment for severe chemical burns, but the phenotypes of cells that infiltrate the amniotic membrane and the clinical significance of these cellular infiltrations have not previously been reported. The present work studies the inflammation cell traps and apoptosis inducing roles of the amniotic membrane after AMT in patients with acute chemical burns.

METHODS

A total of 30 patients with acute alkaline burns were classified as having either moderate or severe burns. In all participants, AMT was performed within one week of his/her injury. After 7-9 days, the transplanted amniotic membranes were removed. Histopathological and immunohistochemical techniques were used for the examination and detection of infiltrating cells, and tests for the expression of CD (cluster of differentiation)15, CD68, CD3, CD20, CD57, CD31, CD147, and CD95 (Fas) were performed. A TUNEL (TdT-mediated dUTP nick end labeling) assay was used to confirm apoptosis of the infiltrating cells. Three patients with herpes simplex-induced keratitis who had undergone AMT to treat persistent epithelium defects were used as a control group. Amniotic membrane before transplantation was used as another control.

RESULTS

After amniotic membrane transplantation, the number of infiltrating cells in patients with severe burns was significantly higher than in patients with moderate burns or in control patients (p<0.05). Among the severe burns patients, CD15 and CD68 were widely expressed in the infiltrating cells, and CD3, CD20, and CD57 were only found in a small number of cells. Occasionally, CD31-positive cells were found in the amniotic membranes. More cells that were CD147, Fas, and TUNEL positive were found in patients with severe burns than in patients with moderate burns or in control patients.

CONCLUSIONS

Neutrophils and macrophages were the main cells that had infiltrated into the amniotic membrane during the acute phase of healing from a chemical burns. AMT can trap different inflammatory cells and induce apoptosis of inflammatory cells in acute ocular chemical burns.

Amniotic membrane transplantation: An option for ocular surface disorders

BACKGROUND

Ocular surface disorders (OSD) are challenging to treat. They can introduce serious morbidity and might even lead to visual loss. In such situations, keratoplasty remains the last option. Amniotic membrane transplantation (AMT) has been shown to be effective in the management of ocular surface pathologies. The aim of the study was to assess the efficacy of AMT for various indications of OSD.

MATERIALS AND METHODS

Experience of AMT in 65 patients with different OSD was evaluated. The aim of AMT was to achieve symptomatic relief, reduced inflammation, recurrence, and corneal haze; improve epithelization, stromal healing and visual acuity; and delay keratoplasty. Fresh amniotic membrane was used in all cases by a single surgeon. Follow-up and observations were done to evaluate success of achieving the goal.

RESULTS

Indications for AMT included primary and recurrent pterygium, various types of corneal ulcers (non-healing ulcer, descemetocele, corneal thinning and perforation), spheroidal degenerations, chemical burn and bullous keratopathy. The aim of AMT was different in different etiological indications. Postoperative follow-up was between 6 and 18 months. Success and complication rate were observed. Symptomatic relief (reduced pain and redness) was seen in patients with various corneal ulcers, chemical burn and bullous keratopathy. Improved epithelialization and stromal healing was noted in corneal ulcer cases. In spheroidal degenerations, keratectomy with AMT improved vision. Recurrence of pterygium was low (4.61%); graft failure in the form of graft rejection was seen in only 3.07% cases of acute keratitis. Corneal vascularization (4.61%) was present but not severe enough to hamper vision. Success in gaining intended effect was the most significant result with AMT.

CONCLUSION

AMT in various ocular surface pathologies shows success in achieving the goal of symptomatic relief, improved epithelialization, stromal healing and vision. Reduction in inflammation, corneal haze and recurrence of original disease is achieved with minimum complications.

Oxygen therapy for acute ocular chemical or thermal burns: a pilot study

PURPOSE

To evaluate the effect of systemic oxygen therapy in the management of acute ocular chemical and thermal burns.

DESIGN

Prospective, nonrandomized, comparative, interventional case series.

METHODS

Twenty-four eyes of 22 patients with grade III to IV acute ocular chemical and thermal burns received conventional medical therapy. The oxygen therapy group (13 eyes) additionally received 100% oxygen using a simple mask at a flow rate of 10 L/minute for 1 hour twice daily. Main outcome measures were time for healing of the corneal epithelial defect and improvement in perilimbal ischemia. Secondary outcome measures included visual acuity, corneal transparency and vascularization, and complications.

RESULTS

Corneal epithelial defects healed within 15.23 ± 3.94 days (range, 10 to 21 days) in the oxygen group versus 59.9 ± 23.33 days (range, 28 to 95 days) in controls (P < .001). Vascularization of ischemic areas was complete in 14.54 ± 2.70 days (range, 10 to 21 days) in the oxygen group versus 45.09 ± 22.20 days (range, 25 to 105 days) in controls (P = .001). In the oxygen group, the cornea was more transparent and less vascularized 3 and 6 months after injury. Mean final visual acuity (logarithm of the minimal angle of resolution) was 0.40 ± 0.52 (range, 0 to 1.3) versus 1.11 ± 0.83 (range, 0.1 to 3) in the oxygen and control groups, respectively (P = .018). In the oxygen group, symblepharon or corneoscleral melting did not develop in any patient; however, in the control group, symblepharon developed in 3 eyes and corneoscleral melting developed in 1 patient.

CONCLUSIONS

In the acute phase of ocular chemical or thermal burns, oxygen therapy improves limbal ischemia, accelerates epithelialization, increases corneal transparency, and decreases corneal vascularization. It also may improve visual acuity and reduce complications.

Management of severe ocular burns with symblepharon

BACKGROUND

To evaluate the effect of lamellar keratoplasty combined with limbal stem cells, using amniotic membrane, autologous conjunctiva, and pseudopterygium to reconstruct external eyes for severe ocular burns with symblepharon.

METHODS

Thirty eyes of 29 patients had severe symblephara resulting from eye burns. According to the range of the symblepharon and the loss of limbal stem cells, partial lamellar keratoplasty combined with partial limbal stem cell treatment was performed in 19 eyes, and total lamellar keratoplasty with total limbus was performed in 11 eyes. All patients had amniotic membrane and autologous conjunctival transplantation, and the pseudopterygium was preserved to reconstruct the fornix.

RESULTS

Symblephara were completely relieved in 19 eyes. They remained partially in ten eyes in strip-like form, but seven of these were completely relieved after further autologous conjunctival transplantation. One eye was treated with tarsorrhaphy for eyelid malformation. The remaining pseudopterygium became thinner after the operation and showed no symblepharon. Immune rejection occurred in eight corneal grafts; clarity was restored in four of these, while there was graft neovascularization in the remaining four.

CONCLUSIONS

Depending on the area of symblepharon and the loss of limbal stem cells, partial or total lamellar keratoplasty combined with limbal stem cells, using amniotic membrane, autologous conjunctiva and pseudopterygium to reconstruct external eyes appears to be effective in treating severe ocular burns with symblepharon. Pseudopterygium can partly substitute autologous conjunctiva in ocular surface reconstruction.

Temporary sutureless amniotic membrane patch for acute alkaline burns

OBJECTIVE

To evaluate the clinical outcome of a new sutureless approach for a temporary amniotic membrane patch (ProKera; Bio-Tissue, Inc, Miami, Florida) in eyes with acute burns.

METHODS

Retrospective review of 5 eyes of 5 patients with grades I to III acute alkaline burns, receiving ProKera insertion within 8 days of injury.

RESULTS

These eyes had either total (2 cases) or extensive (60%-75%, 3 cases) corneal epithelial defects with limbal (120 degrees -360 degrees ) and conjunctival (30%-60%) epithelial defects. ProKera was inserted within a mean (SD) of 3.7 (3.1) days after burn and repeated 1 to 3 times for 3 cases. Conjunctival defects reepithelialized in 8.2 (5) days (range, 5-17 days), while limbal and corneal defects healed in 13.6 (8.3) days (range, 5-25 days). The latter was completed with circumferential closure of limbal defects followed by centripetal healing of corneal defects. In 3 eyes, early peripheral corneal neovascularization was followed by marked regression on completion of healing. During 16.8 (10.8) months of follow-up, all eyes retained a stable surface with improved corneal clarity, and without limbal deficiency or symblepharon.

CONCLUSION

This sutureless application of an amniotic membrane patch allows for early delivery of its biologic actions, which may help preserve remaining limbal stem cells for rapid expansion and prevent late cicatricial complications in eyes with mild and moderate acute alkaline burns.

[Advantages of amniotic membrane transplantation in eye surface diseases]

Amniotic membrane transplantation is now a widely adopted technique in the field of eye surface diseases. Depending on the indication, the amniotic membrane can be used as either a graft or a patch. When used as a graft, the amniotic membrane serves as a substrate for regrowth of deficient epithelium; the aim is to integrate this membrane. The basal membrane reinforces the adhesion and differentiation of the corneal epithelial cells, facilitates their migration, and prevents their apoptosis. When used as a patch, the amniotic membrane is sutured epithelium-down so as to maximize the concentration of biological factors delivered by this membrane: the membrane covers the diseased cornea and acts as a biological bandage and analgesic. The best indications for amniotic membrane grafts are acute chemical burns and trophic corneal ulcers refractory to all medical treatment. When these ulcers are perforated or in the early stages of perforation, it is best to use multiple layers of amniotic membrane, restoring the thickness of the cornea. In cases of confirmed limbal deficiency, amniotic membrane grafts may be a useful complement to the necessary limbal stem cell grafts. In the future, amniotic membranes will provide an indispensable support for the expansion of cultured stem cells. Amniotic membrane grafts may also be used to reconstruct the conjunctiva following the exeresis of symblepharons or conjunctival tumors. However, the use of this technique is currently limited to diseases with little inflammation and no extensive fibrosis.

The use of impression cytology in the follow-up of severe ocular burns

AIMS

To evaluate by impression cytology (IC) the expression of the MHC class II inflammatory marker HLA-DR by the conjunctival epithelium, the cytological modifications of the conjunctival surface according to the Nelson's classification, and the eventual correlation between the two after severe ocular burns.

METHODS

A total of 24 patients (24 eyes) who presented with severe ocular burns underwent IC. We compared them with 18 healthy eyes. HLA-DR expression was studied by flow cytometry as well as the conjunctival histology evaluated with the Nelson's classification from 2-24 months after the onset of burns.

RESULTS

There was a significant upregulation of the expression of HLA-DR in eyes with burns compared to the healthy population at 2 months (p<0.001), 6 months (p<0.001), 12 months (p = 0.019), 18 months (p = 0.0171) and 24 months (p = 0.01766). A significant difference was found between the Nelson grade in the pathological population and those of the healthy population at 2 months (p = 0.0157). HLA-DR upregulation was significantly correlated with the Nelson's grades between 2 months (r = 0.69, p<0.0001) and 6 months (r = 0.61, p = 0.0001).

CONCLUSION

The IC technique can act as a useful tool for following-up ocular surface inflammation after severe ocular burns.