Is There a Relationship between Optic Nerve and Chiasm Measurements with HbA1c Levels in Diabetic Patients?

Objectives  We investigated the optic nerve (ON) and chiasm (OC) in magnetic resonance (MR) in diabetic patients by comparing them with hemoglobin A1c (HbA1c) levels. Methods  In this retrospective study, cranial MRIs of 42 adults (19 males and 23 females) with diabetes mellitus (DM) (group1) and 40 healthy controls (19 males and 21 females) (group 2) were included. In both groups, bilateral ON widths and OC area, width, and height were measured. In the DM group, HbA1c values were also obtained at the time of MRI or within the same month. Results  In the DM group, the mean of the HbA1c values was 8.31 ± 2.51%. There were no significant differences between ON diameter; and OC area, width and height of the DM and control groups ( p  > 0.05). In each of the DM and control groups, ON diameter was not different between the right and left sides ( p  > 0.05). In DM groups, correlation tests showed that there were positive correlations between right and left ON diameters, OC area and OC width, and OC height ( p  < 0.05). In males, ON diameters were higher than those in females bilaterally ( p  < 0.05). In patients with higher HbA1c values, OC width was smaller ( p  < 0.05). Conclusion  A significant correlation of OC width and HbA1c levels suggests that uncontrolled DM causes ON atrophy. Our study represents a thorough assessment of OC measures using standard brain MRI to evaluate optic degeneration in DM patients and shows that the OC width measurement is suitable and reliable. This simple method can be obtained from clinically available scans.