Correlation between corneal and retinal neurodegenerative changes and their association to parafoveal microvascular perfusion in patients with type II diabetes

Abstract

Purpose : The pathophysiologic role of neurodegeneration and angiopathy are controversially discussed for diabetic retinal disease. Changes in the thickness of inner retinal layers as well as corneal nerve fiber loss represent potential biomarkers of neuropathy. The purpose of this study was to determine the correlation between these neurodegenerative features and their association to retinal microvascular perfusion.

Methods : Type II diabetic patients without diabetic retinopathy were included in this cross-sectional study. Nerve fiber -length (NFL), -density (NFD), and -branch density (NBD) was assessed in the corneal subbasal nerve plexus with confocal microscopy using the Rostock Cornea Module of the Heidelberg HRT III Retina Tomograph. The mean retinal nerve fiber- (RNFL), ganglion cell- (GCL), inner plexiform- (IPL), and inner nuclear layer (INL) thickness was analyzed within the 6 mm Early Treatment Diabetic Retinopathy Study grid excluding the central subfield in macular volume scans acquired with Heidelberg Spectralis optical coherence tomography (OCT). Peripapillary RNFL was measured in a circular scan centered on the optic disc. OCT angiography 6x6 mm volume scans were acquired with the RTVue-XR Avanti (Optovue) to determine the parafoveal vessel density (PVD) in the superficial and deep capillary plexus.

Results : We analyzed 118 eyes (58 left eyes) of 61 patients (mean age 57±11 years, 23 female). Peripapillary RNFL, macular RNFL, GCL, IPL and INL were 101±8 μm, 29±3 μm, 43±4 μm, 36±3 μm and 36±3 μm. Corneal NFL, NFD and NBD were 12.3±4.4 mm/mm², 17.8±7.4/mm² and 26.7±15.2/mm². Corneal nerve fiber parameters were neither associated with inner retinal layer thicknesses nor superficial or deep PVD. A significant positive correlation was found between the thickness of the macular GCL, IPL and the peripapillary, but not the macular RNFL with PVD in the deep capillary plexus (p ≤ 0.01 for all).

Conclusions : Our results indicate that corneal and retinal neurodegeneration occur as independent changes in the development of diabetic microvascular complications and that distinct retinal, but not corneal neurodegenerative features are associated with the microvascular perfusion status of the retina. Precise assessment of both types of ocular neurodegeneration is crucial for an early identification of patients at risk.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.