Methodologies for Interventional Myopia Studies

Myopia studies are notoriously difficult to carry out. Past studies on intervention in myopia progression have given conflicting results. Beside inaccurate and inadequate measurements, the most important cause for this is the very variable nature of myopia, which makes it difficult to achieve baseline comparability between the control and the study group. Although there were inclusion criteria in these studies, for age, sex, race, degree of myopia and stigmatism, the most important variate – the rate of myopia progression – was not included. Randomisation can achieve baseline comparability of the myopia progression rate, provided the sample sizes are large enough. Unfortunately, past studies have been limited to 100 to 200 children only. Studies on twins are more reliable than random groups because myopia progression rates are more likely to be the same in a pair of twins. Studies on the same subject, comparing the right eye and the left eye would be even better, but this method is practicable for some studies only (e.g., we cannot have a spectacle lens for one eye and a contact lens on the fellow eye). There is another method of doing an interventional study on myopia. Because myopia progression is linear in its early stage until the early teenage years, it is possible to observe what happens to the linear progression upon intervention. In this way, we avoid the problem of trying to compare “apples with apples” but use the “same apple” instead. Key words: Cross-over study, Linear progression, Myopia progression rate, Randomised controlled trial, Rigid gas-permeable contact lenses</jats:p

The unrecognized burden of typhoid fever

Introduction: Typhoid fever (TF), caused by Salmonella enterica serovar Typhi, is the most common cause of enteric fever, responsible for an estimated 129,000 deaths and more than 11 million cases annually. Although several reviews have provided global and regional TF disease burden estimates, major gaps in our understanding of TF epidemiology remain. Areas covered: We provide an overview of the gaps in current estimates of TF disease burden and offer suggestions for addressing them, so that affected communities can receive the full potential of disease prevention offered by vaccination and water, sanitation, and hygiene interventions. Expert commentary: Current disease burden estimates for TF do not capture cases from certain host populations, nor those with atypical presentations of TF, which may lead to substantial underestimation of TF cases and deaths. These knowledge gaps pose major obstacles to the informed use of current and new generation typhoid vaccines