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

Abstract

Aim/purpose: It is believed that small nerve bundles are damaged in the earliest stages of neuropathy caused by diabetes mellitus. Our goal was to evaluate and compare anatomical characteristics of corneal nerve fibers and corneal sensitivity in type 1 diabetes mellitus patients and in healthy control subjects. Design: cross-sectional study. Method: 30 patients with type 1 diabetes mellitus 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 diabetes mellitus. 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 1 diabetes mellitus possibly predicting the development of neuropathy.