Alterations of retinal thickness measured by optical coherence tomography correlate with neurophysiological measures in diabetic polyneuropathy

• Main Authors: Yuichiro Yamada, Tatsuhito Himeno, Kotaro Tsuboi, Yuka Shibata, Miyuka Kawai, Yuriko Asada‐Yamada, Yusuke Hayashi, Emi Asano‐Hayami, Tomohide Hayami, Yuichiro Ishida, Yohei Ejima, Mikio Motegi, Saeko Asano, Makoto Kato, Eriko Nagao, Hiromi Nakai‐Shimoda, Takahiro Ishikawa, Yoshiaki Morishita, Masaki Kondo, Shin Tsunekawa, Yoshiro Kato, Takayuki Nakayama, Motohiro Kamei, Jiro Nakamura, Hideki Kamiya
• Format: Article
• Language: English
• Published: Wiley 2021-08-01
• Series: Journal of Diabetes Investigation
• Subjects: Diabetic polyneuropathies; Neuroretina
• Online Access: https://doi.org/10.1111/jdi.13476
• ISSN: 2040-1116; 2040-1124

Abstract Aims/Introduction Diabetic polyneuropathy (DPN) and diabetic retinopathy (DR) are traditionally regarded as microvascular complications. However, these complications may share similar neurodegenerative pathologies. Here we evaluate the correlations in the severity of DPN and changes in the thickness of neuroretinal layers to elucidate whether these complications exist at similar stages of progression. Materials and Methods A total of 43 patients with type 2 diabetes underwent a nerve conduction study (NCS), a macular optical coherence tomography, and a carotid artery ultrasound scan. Diabetic polyneuropathy was classified according to Baba’s classification using NCS. The retina was automatically segmented into four layers; ganglion cell complex (GCC), inner nuclear layer/outer plexiform layer (INL/OPL), outer nuclear layer/photoreceptor inner and outer segments, and retinal pigment epithelium (RPE). The thickness of each retinal layer was separately analyzed for the fovea and the parafovea. Results Fourteen patients were classified as having moderate to severe diabetic polyneuropathy. The thicknesses of the foveal and parafoveal INL/OPL increased in patients with diabetic polyneuropathy compared with patients without. The thickness of the parafoveal retinal pigment epithelium decreased in patients with diabetic polyneuropathy. The thinning of parafoveal ganglion cell complex and foveal and parafoveal retinal pigment epithelium were positively correlated with deterioration of nerve functions in the nerve conduction study, but the thickening of INL/OPL was positively correlated with the nerve function deterioration. The thinning of parafoveal ganglion cell complex and foveal retinal pigment epithelium were positively correlated with the thickening of the carotid intima‐media. Conclusions Depending on the progression of diabetic polyneuropathy, the ganglion cell complex and retinal pigment epithelium became thinner and the INL/OPL became thicker. These retinal changes might be noteworthy for pathological investigations and for the assessment of diabetic polyneuropathy and diabetic retinopathy.