3.2 Risk of bias of included studies
The overall risk of bias was not high. The key limitations were the lack
of information on random methods and the low level of reported blinding
of participants because the TA was administered by injection and could
not be blinded. The assessment of the risk of bias in the included
studies is shown in Figure 2. Of the 16
studies, for selection bias, 4
studies (25%) were at low risk of bias in the randomisation process, 4
studies (25%) were at low risk of bias in deviations from the intended
interventions, and 16 trials (100%) were at low risk in missing outcome
data. The outcome indicator (IOP) in this analysis was objective and was
not influenced by evaluators, so the 16 studies (100%) were at low risk
for measurement of the outcome and selection of the reported result.
Overall, three studies (19%) had a low risk of bias, thirteen studies
(81%) had some concerns of bias, and no trials had a high risk of bias.
A quantitative synthesis of the evidence through a network meta-analysis
was deemed appropriate given the comparability in study design, outcome
measures, patients involved, and inclusion and exclusion criteria.
Homogeneity and consistency assumptions were confirmed.