Both the neuropathic complications and improvements experienced by Type I diabetes patients might originate in surprising places. Although blood sugar plays an inconsequential role in corneal function, researchers have found that corneal nerve fiber status was most robust among patients with high glycemic variability and also in those with high insulin doses.

The study, conducted in the Czech Republic, tested for possible associations between parameters of glycemia compensation (HbA1c, glycemic variation and insulin dose) and corneal sub-basal nerve fiber status. In 20 patients with diabetes treated using an intensified insulin regimen, researchers examined the corneas of both eyes using in vivo corneal confocal microscopy and evaluated corneal nerve fiber density, nerve fiber length and nerve branch density.

The researchers were surprised to find that HbA1c had a negligible association with the corneal nerve parameters, while a strong connection existed with glycemic variability. All were statistically significantly higher in those with a higher total dose of insulin per kilogram. Total insulin dose also correlated with glycemic variability.

The study concludes that total insulin dose per kilogram may be an important factor influencing nerve fiber status and needs to be considered in future studies of diabetic neuropathy pathophysiology and its progression.

Mahelková G, Burdová MC, Malá S, et al. Higher total insulin dose has positive effect on corneal nerve fibers in DM1 patients. Invest Ophthalmol Vis Sci. 2018;59:3800-7.