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Using Corneal Microscopy to Detect Neuropathy in Prediabetes

Corneal confocal microscopy (CCM) could be used and adopted as a surrogate marker for small-fiber neuropathy in patients with diabetes or risk of diabetes….

The use of CCM has been increasingly publicized and used more often than skin biopsy, which was the original gold standard for assessing small-fiber neuropathy. It’s a noninvasive ophthalmic instrument that allows the doctor to detect if there is any nerve damage.

Researchers conducted a study which included 37 patients aged 30-75 years with oral glucose tolerance test values between 7.8-11.1 mmol/L (about 140-200mg/dL) and 20 normal controlled patients. Those in the impaired glucose tolerance (IGT) group had significantly lowered corneal nerve branch density (p<0.02), corneal nerve fiber density (p>0.001), and corneal nerve fiber length (p=0.05) when assessed by the CCM. In addition, those with IGT had significantly higher neuropathy symptom profile (p<0.001) as well as higher neuropathy disability score (p<0.001), vibration perception threshold (p<0.002), and McGill pain index (2.8 vs 0.2; p<0.001) when compared to control. The use of the CCM revealed that about 41% of the IGT group had corneal nerve fiber densities that were 2 standard deviations below the control group’s average.

This CCM used in the study suggests that there is an association between impaired glucose tolerance and nerve damages. With this novel instrument alongside sensory testing and skin biopsy, evidence of neuropathy becomes more apparent. A much larger study is warranted in the future to reassess the accuracy of the novel instrument in order to detect neuropathy in diabetes patients.

Practice Pearls:
  • Corneal confocal microscopy (CCM) is a non-invasive ophthalmic instrument that allows the doctor to detect for surrogate markers of small-fiber neuropathy in patients with diabetes.
  • The use of CCM has been increasingly publicized and used more often than skin biopsy, which was the original gold standard for assessing small-fiber neuropathy.
  • Those in the impaired glucose tolerance (IGT) group had a significantly lowered corneal nerve branch density, corneal nerve fiber density, and corneal nerve fiber length; this implies nerve damage in the patient.

Asghar O, Petropoulos IN, Jones W, et al. Corneal Confocal Microscopy Detects Neuropathy in Subjects With Impaired Glucose Tolerance. Diabetes Care. 2014 July 10.