Amniotic membrane transplantation for the treatment of ocular burns

Ocular surface burns vary in severity from mild and self-limiting to devastating injuries characterised by failure of regeneration of the ocular surface, leading to blindness and disfigurement. The historical use of amniotic membrane transplantation (AMT) to treat eye burns during the acute phase has re-emerged in recent years, although its precise effects on the healing process have not been proven by randomised controlled trials (RCTs). One RCT conducted in India included a subset of patients who fulfilled the criteria for analysis in this review. The participants included 68 men and women of all ages with chemical or thermal burns to the ocular surface, who were randomised to treatment with conventional medical therapy alone or to medical therapy and AMT in the first seven days after injury. Conventional medical therapy included topical steroids, antibiotics, sodium ascorbate, sodium citrate, tear substitutes and cycloplegic drops, and oral vitamin C. Pressure-lowering drops and/or oral acetazolamide were prescribed if required. Data from the RCT were analysed to compare corneal wound closure rates by the 21st day after the injury and visual outcomes at final follow-up. The burns were classified as moderate or severe. In the moderate category, the AMT group had a higher proportion of eyes with complete epithelial closure by day 21 (not statistically significant) and significantly better visual acuity at final follow-up. There was a high risk of bias resulting from the uneven characteristics of the control and treatment eyes at presentation and from the failure to mask personnel and outcome assessors involved in the study. 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.

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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 strategy: 

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.

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