Corneal confocal microscopy and not optical coherence tomography detects progressive worsening of neuropathy in Type 1 Diabetes

Abstract

Purpose : Damage to peripheral nerve fibres and retinal microvasculature is common in type 1 diabetes (T1D) and both are associated with diabetic foot ulceration. To assess differences in ocular biomarkers of corneal confocal microscopy (CCM), optical coherence tomography (OCT) and OCT Angiography (OCTA) in T1D without neuropathy (T1D), with diabetic neuropathy (T1DPN) and neuropathic foot ulcers (T1DFU).

Methods : Detailed neuropathy phenotyping was undertaken in participants with T1D-(n=21), T1DPN-(n=14) and T1DFU-(n=16) using neuropathy symptom profile-(NSP), McGill pain questionnaire-(SF-MPQ), vibration perception threshold-(VPT), sural nerve conduction velocity-(SCV) and amplitude-(SAmp). CCM determined corneal nerve fibre density-(CNFD), branch density-(CNBD) and fibre length-(CNFL). Macular vessel density-(MVD), retinal nerve fibre length-(RNFL), ganglion cell layer-(GCL), inner nuclear layer-(INL), choroid thickness-(CT) and fovea avascular zone-(FAZ) were obtained with OCT and OCTA. Assessments were conducted in a masked fashion.

Results : When comparing T1D vs T1DPN vs T1DFU: There were no differences in age, diabetes duration, BMI, systolic BP and cholesterol (Figure 1). HbA1c (mean±SD) (68±13, 72±12, 81±15mmol/mol; p<0.026), NSP (1.6±1.9, 8.0±4.1, 17.4±6.5; p<0.001), SF-MPQ visual analogue scale(-/10) (1.7±2.8, 4.4±3.2, 6.6±3.2; p<0.001), VPT (9.25±2.1, 22.7±8.7, 30.7±13.0V; p<0.001) were higher, whilst SCV (50.2±4.8, 41.5±9.3, 30.3±5.1m/s; p<0.001) and SAmp (6.8±3.3, 4.4±3.0, 1.6±0.9mV; p<0.001) were lower in T1DPN and T1DFU. CCM showed progressive deterioration in CNFL (8.4±1.9, 5.8±1.8, 5.2±1.5mm/mm²; p<0.001), CNFD (17.6±6.2, 9.3±3.3, 6.9±4.6no/mm²; p<0.001) and CNBD (21.9±12.4, 8.7±5.5, 5.7±5.5 no/mm²; p<0.001) from T1D to T1DPN to T1DFU. No between group differences were seen in RNFL, GCL, INL, CT, MVD and FAZ.

Conclusions : CCM detects diabetic neuropathy in type 1 diabetes and greater neuropathy burden in definite neuropathy and foot ulceration prior to retinal biomarkers of OCT/OCTA.

This is a 2020 ARVO Annual Meeting abstract.

 

Demographic data of the patients who have type 1 diabetes without neuropathy (T1D), with diabetic neuropathy (T1DPN) and neuropathic foot ulcers (T1DFU).