Response to comment on: Incidence of ocular and systemic disease affecting visual function among state bus drivers

Dear Editor,

We thank the authors for their interest in our article.[1] We sincerely appreciate the fact that the authors have raised a valid point related to the statistics of the manuscript. We agree with the authors’ comments.[2] In addition, we would like to briefly summarize few important points related to epidemiological studies with respect to our study.

Epidemiology is defined as the study of distribution and determinants of health-related events (various ocular and systemic diseases affecting visual function) in a specific population (state bus drivers) and the application of the study outcomes to control the health problems (road traffic accidents, RTA). It forms the cornerstone of public health and preventive healthcare, thereby helping shape the policy decisions (related to driving licensing rules) necessary to avoid preventable diseases (RTA). Epidemiological studies can be either observational or experimental. The former can be either descriptive or analytical (ecological, cross-sectional, case-control, and cohort).[3]

Our study was a cross-sectional study, i.e., it evaluated the health profile of state bus drivers at a specific point of time (in the year 2019). Such a study is capable of evaluating “point prevalence,” i.e., the proportion of state bus drivers that suffered from various ocular and systemic diseases which can potentially affect their visual function, in the year 2019. Such a data can help us determine the proportion of state bus drivers who were at risk of being involved in RTA in the year 2019.[4] On the contrary, the incidence is defined as the number of people that develop the disease in a particular period during a specified population. For example, we can re-examine the same set of drivers next year and evaluate the number of drivers who developed a new disease (e.g., visually significant cataract) in the year 2020. Incidence is expressed as the number of drivers who developed cataracts per 1,000 drivers per year.

Case-control and cohort studies can help us understand the association between a particular disease (cataract) and RTA.[5] Case-control studies can help us calculate the odds ratio, i.e., the odds of drivers with cataracts being involved in RTA to the odds of drivers without cataracts being involved in RTA. Similarly, cohort studies can help us calculate the attributable risk, i.e., the extent to which RTA can be attributed to cataracts among the drivers. This will help us estimate the number of RTAs that can be avoided if these drivers underwent timely cataract surgery.[4] Case-control and cohort studies are required to understand the association between the visual function-hampering diseases and RTA. The results of such studies can be used to nitpick the “at-risk” drivers and evaluate their driving skills through simulated tests and fatigue tests. More studies in this regard need to be planned with the aim of improving the laws related to the mandatory standards required for obtaining and renewing driving licensing. Continuous research is needed to tackle this important public health issue and make the roads safer.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.