Corneal Confocal Microscopy Detects Neuropathy in Subjects With Impaired Glucose Tolerance

Omar Asghar; Ioannis N. Petropoulos; Uazman Alam; Wendy Jones; Maria Jeziorska; Andrew Marshall; Georgios Ponirakis; Hassan Fadavi; Andrew J.M. Boulton; Mitra Tavakoli; Rayaz A. Malik

Disclosures

Diabetes Care. 2014;37(9):2643-2646. 

In This Article

Research Design and Methods

Study Subjects

The study comprised 37 subjects aged 30–75 years with IGT (oral glucose tolerance test: 2-h glucose = 7.8–11.1 mmol/L) and 20 age-matched control subjects with glucose tolerance within normal limits. Subjects with any other cause of peripheral neuropathy, active corneal disease, surgery, or chronic contact lens use were excluded. This research adhered to the tenets of the declaration of Helsinki and was approved by the North Manchester Research Ethics committee. Informed written consent was obtained from all subjects before participation.

Clinical and Peripheral Neuropathy Assessment

All subjects underwent assessment of systolic and diastolic blood pressure, BMI, HbA1c, lipid fractions (total cholesterol, LDL, HDL, and triglycerides), and estimated glomerular filtration rate. Signs and symptoms of neuropathy were assessed using the neuropathy symptom profile, neuropathy disability score, vibration perception threshold (VPT; Horwell Scientific Laboratory Supplies, Wilford, Nottingham, U.K.), and cool (CT) and warm (WT) thresholds (Medoc Ltd., Ramat-Yishai, Israel). Sural sensory nerve amplitude and conduction velocity, and peroneal motor nerve amplitude and conduction velocity were assessed. Heart rate variability deep breathing (HRVdb) was assessed with an ANX 3.0 autonomic nervous system monitoring device (ANSAR Medical Technologies Inc., Philadelphia, PA). Sudomotor function was assessed using Neuropad (miro Verbandstoffe, Wiehl-Drabenderhole, Germany).

Skin Biopsy

A 3-mm punch skin biopsy specimen was obtained from the dorsum of the foot ~2 cm above the second metatarsal head after local anesthesia (1% lidocaine), and IENFD was quantified in accord with established criteria.[8]

CCM

Patients underwent examination with CCM (Heidelberg Engineering GmbH, Heidelberg, Germany), and three established corneal nerve parameters—corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), and corneal nerve fiber length (CNFL)—were quantified in a masked fashion, as previously described.[9]

Statistical Analysis

SPSS for Mac version 19.0 software (IBM Corp., Armonk, NY) was used for descriptive and frequency statistics. An unpaired t test (or nonparametric Mann-Whitney U test) was used to study differences between means. All data are expressed as mean ± SEM, and a P < 0.05 was considered significant.

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