Corneal confocal microscopy able to detect clinical, subclinical DPN

Corneal confocal microscopy (CCM) can detect small nerve fibre loss in both clinical and subclinical cases of diabetic peripheral neuropathy (DPN), reports a recent meta-analysis.

The researchers retrieved 38 studies from the online databases of PubMed, Embase, Centra, and ProQuest, selecting for observational studies that reported on at least one CCM parameter and assessed its diagnostic utility for DPN. The cumulative sample included approximately 4,000 participants.

Twenty-nine studies compared corneal nerve fibre density (CNFD) between patients with and without DPN and found that the former group had significantly lower CNFD (mean difference [MD], –7.01 fibre/mm², 95 percent confidence interval [CI], –7.45 to –6.57; p<0.00001).

Notably, diabetics without DPN also showed significantly lower CNFD relative to controls (MD, –5.85, 95 percent CI, –6.12 to –5.57; p<0.00001).

Similar patterns were observed for corneal nerve branch density, corneal nerve fibre length, and inferior whorl length, which were all significantly lower in diabetics with vs without DPN, and in diabetics without DPN vs controls.

“CCM is a rapid, noninvasive and reproducible imaging technique to quantify small nerve fibre damage. Our systematic review and meta-analysis provides robust evidence that corneal confocal microscopy can be used to diagnose subclinical and established DPN,” the researchers said.

“Furthermore, we demonstrate a lesser but significant reduction in all corneal nerve parameters in patients without DPN compared to controls, suggesting that CCM detects early subclinical DPN,” they added.