Aslan MG, Fındık H, Okutucu M, et al. - Researchers conducted the study for assessing the serum 25-hydroxy vitamin D, vitamin B12, and folic acid (FA) levels in progressive and nonprogressive patients with keratoconus (KCN). The sample consisted of 55 patients with KCN (28 progressive and 27 nonprogressive) who were followed up for at least 12 months and separated into 2 groups according to corneal topographic progression criteria. Age- and sex-matched 30 healthy people formed the control group. In nonprogressive, progressive, and control groups, respectively, serum vitamin D levels were 12.77 ± 5.52, 11.78 ± 4.32, and 17.40 ± 5.12 ng/mL. In both KCN groups, serum vitamin D levels were significantly decreased. In all groups, however, serum vitamin B12, FA, and Ca levels were identical. Evaluation of serum vitamin D in KCN patients at onset and follow-up examinations can help to predict the course of the disease.