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Eye Scan Predicts Peripheral Neuropathy in Type 1 Diabetes

Corneal confocal microscopy (CCM) can predict incipient peripheral neuropathy in patients with type 1 diabetes…

The technique involves the examination of unmyelinated nerve fibers at high magnification using a laser-scanning corneal confocal microscope to image the subbasal nerve plexus of the patient’s cornea. Increased severity of diabetic peripheral neuropathy is associated with reduced corneal-nerve fiber length and corneal sensitivity.

Previous studies have demonstrated utility for CCM in assessing peripheral diabetic neuropathy, autonomic neuropathy, and neuropathy in those with prediabetes.

In the current study of 90 initially nonneuropathic patients with type 1 diabetes, CCM had 63% sensitivity and 74% specificity for detecting 4-year incidence of diabetic peripheral neuropathy using a corneal-nerve fiber-length cutoff of 14.1 mm/mm2.

The new study enrolled 101 patients aged 14 to 80 years who had no peripheral neuropathy at baseline. Of the 90 who were assessed at 4 years, 16 (18%) had developed diabetic peripheral neuropathy.

With CCM, results showed that corneal-nerve fiber length was significantly lower among those who had developed diabetic peripheral neuropathy at 4 years, 14.0 mm/mm2, compared with 16.2 mm/mm2 among those who did not (P = .041).

Other significant predictors included: longer duration of diabetes; higher triglycerides; retinopathy; nephropathy (higher albumin-to-creatinine ratio; P = 0.001); higher neuropathy disability score; lower cold-sensation and cold-pain thresholds; higher warm-sensation and warm-pain and vibration thresholds; impaired monofilament response; and slower peroneal and sural-nerve-conduction velocities. Cold-sensation threshold had the highest predictive capacity, with sensitivity 88% and specificity 55% at a cutoff of 29.2°C.

“These findings confirm an expanded role of CCM in the assessment of diabetic peripheral neuropathy as a supplement to the wide array of neurological tests currently in use,” the authors state.

Practice Pearls:

  • Increased severity of diabetic peripheral neuropathy is associated with reduced corneal-nerve fiber length and corneal sensitivity.
  • CCM can be used to predict those who will develop diabetic peripheral neuropathy.
  • Corneal-nerve fiber length was significantly lower among those who had developed diabetic peripheral neuropathy at 4 years, 14.0 mm/mm2, compared with 16.2 mm/mm2 among those who did not (P = .041).

Nicola Pritchard, Corneal Confocal Microscopy Predicts 4-Year Incident Peripheral Neuropathy in Type 1 Diabetes, Diabetes Care, pub online January 8, 2015, doi: 10.2337/dc14-2114