Correlation of Diabetic Retinopathy and Corneal Neuropathy Using Confocal Microscopy

Abstract

Purpose/Aim: To employ corneal confocal microscopy to assess differences in the extent of corneal nerve fiber alterations between diabetic patients classed according to retinopathy status and nondiabetic patients.

Materials and Methods: Two hundred seventy-eight corneas of 139 patients with type 2 diabetes mellitus and 94 corneas of 47 age-matched control participants were scanned using corneal confocal microscopy. Images of the subbasal nerve plexus were collected and analyzed for nerve fiber density (NFD), nerve branch density (NBD), nerve fiber length (NFL), and nerve fiber tortuosity (NFT). Diabetic patients were categorized into three groups according to the classification of diabetic retinopathy (DR) proposed in the Early Treatment of Diabetic Retinopathy Study, based on indirect fundoscopy, fundus photography, and fluorescein angiography findings. A separate classification into four groups according to the severity of peripheral diabetic neuropathy (DN) was also used, based on the results of clinical and electrodiagnostic examinations.

Results: Average NFD, NBD, and NFL differed significantly according to DR status and were found to be lower, whereas NFT was found to be higher in diabetic patients than control participants. A positive correlation between diabetic corneal neuropathy and peripheral DN was also found.

Conclusions: Nerve fiber alterations of the subbasal nerve plexus of diabetic corneas appear to progress in parallel with DR and peripheral DN. Corneal confocal microscopy could possibly represent a promising adjuvant technique for the early diagnosis and assessment of human DN.

KEYWORDS::

• Corneal confocal microscopy
• Diabetic corneal neuropathy
• Diabetic retinopathy
• Peripheral diabetic neuropathy
• Subbasal nerve plexus

ACKNOWLEDGMENTS

The authors would like to thank Dr. Sotiris Plainis for his support and advice in the design of the study.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper. Some of the authors have attended conferences, given lectures and participated in advisory boards or trials sponsored by various pharmaceutical companies. Dr Kallinikos received a postdoctoral research grant from the Greek State Scholarship Foundation.