Comparison of patients with different stages of keratoconus in terms of cornea endothelial cell changes, serum vitamin D levels and serum eosinophil count

In our study, the data and topography findings of 80 patients who were followed up with the diagnosis of keratoconus in the Ophthalmology Department of Gaziantep University Faculty of Medicine between January 2021 and December 2021 were retrospectively analyzed. We aimed to compare the structural and quantitative changes in corneal endothelial cells and changes in serum vitamin D levels and serum eosinophil counts in patients with keratoconus according to stages. Of these patients, patients who had previously given blood for any reason and had serum vitamin D levels and serum eosinophil counts in the system were included in the study. In the study, the data obtained from the autorefractometer, uncorrected and corrected visual acuity values, corneal topographic features with the Sirius topography device, which combined Scheimpflug camera and Plasido disc technology, and specular microscopy results obtained with the Nidek CEM 530 device were recorded. The parameters evaluated in the study from specular microscopy measurement were determined as endothelial cell density (ECD), endothelial mean cell surface area, coefficient of variation (CV) and hexagonal cell percentage (HEX). The patients were divided into 4 stages according to the Amsler Krumeich Classification. Patients in Stage 4 were omitted because their corneal opacities prevented an appropriate specular microscopy and corneal topography evaluation. The mean age of the patients included in the study was 23 ± 4.15 years (range 18-35 years). A total of 47 (58.8%) men and 33 (41.2%) women were included in the study. No statistically significant difference was found in terms of ECD (p=0.144), mean cell surface area (p=0.594), CV (p=0.199) and HEX (p=0.195) in different stages of keratoconus. Although a decrease in ECD, an increase in CV and a decrease in HEX were detected in patients with keratoconus as the stage progressed, this difference was not statistically significant. HEX was found to be significantly lower in the mild-moderate keratoconus (stage 1 and stage 2) group (n=60) compared to the severe keratoconus (stage 3) group (n=20) (p=0.048). Although there was a decrease in serum vitamin D levels as the stage progressed, there was no statistically significant difference in serum vitamin D levels according to the stages (p=0.486). Although deficiency (≤10 ng/mL) was detected most frequently in stage 3 in terms of serum vitamin D level distribution (deficient, insufficient, and optimal), there was no statistically significant difference between stages in terms of serum vitamin D level distribution (p=0.571). There was no significant difference between different stages of keratoconus in terms of serum eosinophil count (p=0.535). In conclusion, in this study conducted using specular microscopy, it was found that there were structural and quantitative changes in the corneal endothelium in different stages of keratoconus.In addition, we found a reduction in serum vitamin D level as the stage of keratoconus proceeded, even if it was not statistically significant; however, further studies with more patients are needed in terms of serum vitamin D level and keratoconus pathophysiology and the efficacy of vitamin D supplementation in the treatment of keratoconus. Key Words: Keratoconus, Vitamin D, Specular Microscopy, Eosinophil