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

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.

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.