Commentary on “Serum vitamin D is substantially reduced and predicts flares in diabetic retinopathy patients”

Abstract

Dear Editor,

We read with great interest the article “Serum Vitamin D is Substantially Reduced and Predicts Flares in Diabetic Retinopathy Patients,” published in your esteemed journal¹. The study aimed to clarify whether vitamin D deficiency predisposes patients to diabetic retinopathy or if the disease leads to reduced vitamin D levels. The findings, namely, significantly lower serum vitamin D in patients with diabetic retinopathy and the suggestion that deficiency may accelerate disease onset, are intriguing and hold significant clinical relevance. We appreciate the authors' efforts in conducting this study and their commitment to advancing our understanding of this vital issue. However, we believe that addressing several limitations could enhance the clarity and impact of the study's conclusions.

The study's conclusions might be strengthened by incorporating additional laboratory parameters. The absence of data on markers such as serum albumin, zinc, vitamin B12, platelet-to-lymphocyte ratio (PLR), neutrophil-to-lymphocyte ratio (NLR), and the systemic immune-inflammatory index (SII) is a significant limitation that hinders the comprehensive validation of the findings. The inclusion of these parameters, as suggested by previous studies^{2, 3}, is crucial to better delineate the relationship between vitamin D deficiency and adverse outcomes.

Secondly, the study lacks detailed information regarding the pharmacological interventions administered to the participants. Data on medications such as corticosteroids and phosphodiesterase inhibitors, which can significantly influence patient outcomes, would provide important context for interpreting the results⁴.

Thirdly, the analysis is not adequately adjusted for potential confounding factors, including comorbid conditions like cerebrovascular disease, cardiovascular disorders, peripheral arterial disease, psychological disorders, immune deficiencies, and autoimmune disorders. Given their potential impact on patient outcomes, their inclusion is crucial to strengthen the study's conclusions.

Furthermore, key demographic variables, such as socioeconomic status, educational background, detailed smoking history (including current, former, and heavy smokers), and opium use, were not reported. This omission restricted both the analysis depth and the findings' generalizability. For instance, socioeconomic status and educational background could influence access to healthcare and adherence to treatment, while smoking history and opium use could affect the progression of diabetic retinopathy. Additionally, the explanation of methods used to assess insulin resistance and nutritional status was insufficient and warranted further clarification.

Lastly, there appeared to be a discrepancy between the introduction and discussion regarding the role of vitamin D in modulating vascular endothelial growth factor (VEGF). Resolving this inconsistency would enhance the overall coherence of the article and provide more precise insights into the mechanistic pathways involved.

In summary, while the study provides valuable insights into the potential predictive role of serum vitamin D in the progression of diabetic retinopathy, addressing the above limitations could significantly bolster its impact. For instance, incorporating additional laboratory parameters and adjusting for potential confounding factors could provide a more comprehensive understanding of the relationship between vitamin D deficiency and diabetic retinopathy.

The authors report that there was no funding source for the work that resulted in the article or the preparation of the article.

The authors declare no conflict of interest.

Approval of the research protocol: No ethical approval was required as this letter-to-the-editor article has no original research data.

Informed consent: No patient consent was required as this letter-to-the-editor article did not include any patients.

Registry and the registration no. of the study/trial: N/A.

Animal studies: N/A.