BackgroundVitamin D is a multi-functional fat-soluble metabolite essential for a vast number of physiological processes. Non-classical functions are gaining attention because of the close association of vitamin D deficiency with diabetes, and its complications. The present study was undertaken to evaluate the role of vitamin D as a biomarker for proliferative diabetic retinopathy.MethodsA tertiary care center based cross-sectional study was undertaken. Seventy-two consecutive cases of type 2 diabetes mellitus were included. Diagnosis of diabetes mellitus was made using American Diabetes Association guidelines. Study subjects included: diabetes mellitus with no retinopathy (No DR) (n = 24); non-proliferative diabetic retinopathy (n = 24); and proliferative diabetic retinopathy (n = 24) and healthy controls (n = 24). All of the study subjects underwent complete ophthalmological evaluation. Best Corrected Visual Acuity (BCVA) was measured on the logarithm of the minimum angle of resolution (logMAR) scale. Serum 25-OH Vitamin D assay was done using chemiluminescent microparticle immunoassay technology. Diagnostic accuracy of vitamin D was assessed using receiver operating characteristics curve analysis and area under curve (AUC) was determined for the first time.ResultsANOVA revealed a significant decrease in serum vitamin D levels with severity of diabetic retinopathy (F = 8.95, p < 0.001). LogMAR BCVA was found to increase significantly with the severity of DR (F = 112.64, p < 0.001). On AUC analysis, a cut off value of 18.6 ng/mL for Vitamin D was found to be significantly associated with proliferative diabetic retinopathy [sensitivity = 86.36% (95% CI 65.1–96.9); specificity = 81.82% (95% CI 59.7–94.7); AUC = 0.91 (excellent); and Z value = 8.17].ConclusionsSerum vitamin D levels of ≤ 18.6 ng/mL serve as sensitive and specific indicator for proliferative disease, among patients of DR.
To study the correlation of serum vitamin D levels with quantitative (central subfield thickness [CST], cube average thickness [CAT]), cross-sectional (disorganisation of retinal inner layer [DRIL] and ellipsoid zone [EZ]) and topographic parameters (retinal pigment epithelium [RPE]) on spectral domain optical coherence tomography (SD-OCT) in diabetic retinopathy (DR), for the first time. Methods: Eighty-eight consecutive cases of type 2 diabetes mellitus with no retinopathy (No DR; n = 22); non-proliferative DR (NPDR; n = 22); proliferative DR (PDR; n = 22) and healthy controls (n = 22) were included, after sample size calculation. On SD-OCT, physician-friendly grading systems were created for DRIL, EZ disruption and RPE alterations. Serum vitamin D was analysed using a standard protocol. Statistical analysis was done using Pearson correlation, Student's t-test, ANOVA, Newman-Keuls test, chi-square test and univariate ordinal logistic regression analysis. Results: Mean serum vitamin D levels (ng/ml) were: No DR = 23.36 ± 2.00, NPDR = 17.88 ± 1.86, PDR = 14.07 ± 1.21, and controls = 25.11 ± 1.59. Low vitamin D levels correlated significantly with severity of retinopathy, VA (r = 0.50), CST (r = 0.36), CAT (r = 0.41), DRIL (r = 0.35), EZ disruption (r = 0.40) and RPE alterations (r = 0.37), respectively (p < 0.01). Significantly low vitamin D levels were observed in subjects with DRIL present versus DRIL absent; EZ disruption, focal versus global versus intact; RPE alterations, focal versus global versus none, respectively (p < 0.05). Conclusions: Low serum vitamin D levels correlate with the presence of DRIL, EZ disruption and RPE alterations and increased severity of DR.
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