Assessment and comparison of corneal subbasal nerve plexus morphology and corneal sensitivity in type 1 diabetic and non-diabetic patients

Abstract

Background It is believed that small nerve bundles are damaged in the earliest stages of neuropathy caused by diabetes mellitus (DM). Our goal was to evaluate and compare anatomical characteristics of corneal nerve fibers and corneal sensitivity in type 1DM patients and in healthy control subjects. Methods 30 patients with type 1DM and 10 non-diabetic healthy subjects underwent a corneal confocal microscopy to evaluate the corneal sub-basal nerve fibers (density, number of nerves and branches, total nerve length) and contact corneal aesthesiometry. Results Diabetic patients had significantly lower corneal nerve fiber density (14,32 ± 5,87 vs. 19,71 ± 5,59 mm/mm2 p=0,023 ), nerve branches number (4,57 ± 3,91 vs. 9,90 ± 5,8 n°/image, p=0,006) , nerve fiber length (2,28 ± 0,94 vs. 3,13 ± 0,89 mm, p=0,032) and corneal sensitivity (1,13 ± 0,29 vs. 0,98 ± 0,058 gr/mm2 p=0,02), as compared with controls. A negative correlation was found between corneal nerve fiber length, corneal nerve number, corneal nerve fiber density and diabetes duration (p<0,05). Conclusion Corneal confocal microscopy and corneal sensitivity evaluation may help to evaluate early changes in the sub-basal nerve plexus typical to diabetic neuropathy in patients with DM. Further studies using corneal confocal microscopy as a novel noninvasive technique are needed to locate the earliest alterations in corneal nerves in patients with type 1DM possibly predicting the development of neuropathy.