Dear Editor, I recently read the article "To study the role of hematological biomarkers in type 2 diabetes patients with diabetic retinopathy" by Bajaj et al., published in the Pan-American Journal of Ophthalmology.[1] We now have a better grasp of diabetic retinopathy and possible biomarkers thanks to this informative work. Nonetheless, I would like to discuss a significant methodological issue that affects the inferences made from this research. The authors have concluded that platelet distribution width (PDW) and mean platelet volume (MPV) may be used to predict the onset and severity of diabetic retinopathy. It is important to remember that the study's cross-sectional methodology naturally restricts the capacity to infer causality or predictive power, even if the study data point to a connection and other researchers have described the relation using a meta-analysis.[2] While cross-sectional studies are great for spotting correlations, they cannot prove a time-based link between exposure and results.[3] Although higher MPV and PDW are linked to more severe diabetic retinopathy in the setting of this investigation, it is not clear from the data alone whether these increases are indicative of the onset or course of the problem. A longitudinal research design, where patients are tracked over time to assess the course of diabetic retinopathy in connection to changes in MPV and PDW levels, is necessary to establish these biomarkers as predictive tools. A more thorough knowledge of whether alterations in these biomarkers occur before the beginning or worsening of diabetic retinopathy would be possible with such a study design. Therefore, understanding their role on the course of the disease. This could create new opportunities for therapeutic intervention in addition to validating their usage as prognostic indicators. Furthermore, broadening this study area to encompass varied people across various geographic regions will enhance the external validity of the results. Ultimately, the study's significance would be increased by delving further into the pathophysiological pathways that connect these biomarkers to diabetic retinopathy. New treatment targets may become available if it is determined if the microvascular alterations in diabetic retinopathy are caused or exacerbated by these higher biomarker levels.[4] The research community must address these methodological issues to guarantee that therapeutic practices are supported by solid and thorough evidence. I value the authors' efforts in carrying out this investigation and raising awareness of these possible indicators. Further study is necessary to fully understand MPV and PDW's role in predicting diabetic retinopathy, especially in long-term studies. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.