Corneal Nerve Tortuosity in Diabetic Patients with Neuropathy

PURPOSE. Corneal confocal microscopy is a reiterative, rapid, noninvasive in vivo clinical examination technique capable of imaging corneal nerve fibers. Nerve fiber tortuosity may indicate a degenerative and attempted regenerative response of nerve fibers to diabetes. The purpose of this study was to define alterations in the tortuosity of corneal nerve fibers in relation to age, duration of diabetes, glycemic control, and neuropathic severity. METHODS. The cornea and collected images of the subbasal nerve plexus of 18 diabetic patients (stratified into mild, moderate, and severe neuropathic groups using conventional clinical measures of neuropathy) and 18 age-matched nondiabetic control subjects were scanned, and a novel mathematical paradigm was applied to quantify the extent of nerve tortuosity, which was termed the tortuosity coefficient (TC). RESULTS. TC was significantly different between the four clinical groups (F3 = 12.2, P <0.001). It was significantly greater in the severe neuropathic group than in control subjects (P <0.003) and in the mild (P <0.004) and moderate (P <0.01) neuropathic groups. TC did not correlate significantly with the age (r = -0.003, P <0.05), duration of diabetes (r = -0.219, P > 0.05), or hemoglobin Alc (HbA1c; r = 0.155, P > 0.05) of diabetic patients. CONCLUSIONS. Corneal confocal microscopy allows rapid, non-invasive in vivo evaluation of corneal nerve tortuosity. This morphologic abnormality relates to the severity of somatic neuropathy and may reflect an alteration in the degree of degeneration and regeneration in diabetes.