Corneal nerve loss detected with corneal confocal microscopy is symmetrical and related to the severity of diabetic polyneuropathy

OBJECTIVE

To establish if corneal nerve loss, detected using in vivo corneal confocal microscopy (IVCCM), is symmetrical between right and left eyes and relates to the severity of diabetic neuropathy.

RESEARCH DESIGN AND METHODS

Patients (n = 111) with type 1 and type 2 diabetes and 47 age-matched healthy control subjects underwent detailed assessment and stratification into no (n = 50), mild (n = 26), moderate (n = 17), and severe (n = 18) neuropathy. IVCCM was performed in both eyes and corneal nerve fiber density (CNFD), branch density (CNBD), and fiber length (CNFL) and the tortuosity coefficient were quantified.

RESULTS

All corneal nerve parameters differed significantly between diabetic patients and control subjects and progressively worsened with increasing severity of neuropathy. The reduction in CNFD, CNBD, and CNFL was symmetrical in all groups except in patients with severe neuropathy.

CONCLUSIONS

IVCCM noninvasively detects corneal nerve loss, which relates to the severity of neuropathy, and is symmetrical, except in those with severe diabetic neuropathy.

Corneal confocal microscopy to assess diabetic neuropathy: an eye on the foot

Accurate detection and quantification of human diabetic peripheral neuropathy are important to define at-risk patients, anticipate deterioration, and assess new therapies. Easily performed clinical techniques such as neuro-logical examination, assessment of vibration perception or insensitivity to the 10 g monofilament only assess advanced neuropathy, i.e., the at-risk foot. Techniques that assess early neuropathy include neurophysiology (which assesses only large fibers) and quantitative sensory testing (which assesses small fibers), but they can be highly subjective while more objective techniques, such as skin biopsy for intra-epidermal nerve fiber density quantification, are invasive and not widely available. The emerging ophthalmic technique of corneal confocal microscopy allows quantification of corneal nerve morphology and enables clinicians to diagnose peripheral neuropathy in diabetes patients, quantify its severity, and potentially assess therapeutic benefit. The present review provides a detailed critique of the rationale, a practical approach to capture images, and a basis for analyzing and interpreting the images. We also critically evaluate the diagnostic ability of this new noninvasive ophthalmic test to diagnose diabetic and other peripheral neuropathies.

Diabetes, Obesity and Atrial Fibrillation: Epidemiology, Mechanisms and Interventions

Body mass index (BMI) is a powerful predictor of death, type 2 diabetes (T2DM) and cardiovascular (CV) morbidity and mortality. Over the last few decades, we have witnessed a global rise in adult obesity of epidemic proportions. Similarly, there has been a parallel increase in the incidence of atrial fibrillation (AF), itself a significant cause of cardiovascular morbidity and mortality. This may be partly attributable to advances in the treatment of coronary heart disease (CHD) and heart failure (HF) improving life expectancy, however, epidemiological studies have demonstrated an independent association between obesity, diabetes and AF, suggesting possible common pathophysiological mechanisms and risk factors. Indeed, cardiac remodeling, haemodynamic alterations, autonomic dysfunction, and diastolic dysfunction have been reported in obese and diabetic cohorts. Moreover, diabetic cardiomyopathy is characterized by an adverse structural and functional cardiac phenotype, which may predispose to the development of AF. In this review, we discuss the pathophysiological and mechanistic relationships between obesity, diabetes and AF, and some of the challenges posed in the management of this high-risk group of individuals.

Medical strategies to reduce amputation in patients with type 2 diabetes

Lower extremity amputation is a common and disabling complication of Type 2 diabetes. Whilst the introduction of specialist multidisciplinary teams has led to a reduction in the incidence of lower extremity amputation in some centres, the overall prevalence of diabetes-related amputation has actually increased in recent decades. The aetiology of diabetes-related amputation is complex, with neuropathy, macrovascular and microvascular disease contributing significantly. Ulceration, previous amputation, increasing diabetes duration and poor long-term control of glycaemia and lipids are important risk factors for amputation in populations with diabetes. Major randomized intervention trials of blood glucose-lowering or anti-hypertensive therapies in populations with diabetes have shown limited reductions in neuropathy and/or macrovascular disease, and no benefit on amputation rates. In contrast, a recent analysis from the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) study showed a significantly reduced rate of minor, but not major amputations in patients with Type 2 diabetes treated with fenofibrate. Mechanistic studies are clearly needed to understand the basis of this benefit.

Obesity, diabetes and atrial fibrillation; epidemiology, mechanisms and interventions

The last few decades have witnessed a global rise in adult obesity of epidemic proportions. The potential impact of this is emphasized when one considers that body mass index (BMI) is a powerful predictor of death, type 2 diabetes (T2DM) and cardiovascular (CV) morbidity and mortality [1, 2]. Similarly we have witnessed a parallel rise in the incidence of atrial fibrillation (AF), the commonest sustained cardiac arrhythmia, which is also a significant cause of cardiovascular morbidity and mortality. Part of this increase is attributable to advances in the treatment of coronary heart disease (CHD) and heart failure (HF) improving life expectancy and consequently the prevalence of AF. However, epidemiological studies have demonstrated an independent association between obesity and AF, possibly reflecting common pathophysiology and risk factors for both conditions. Indeed, weight gain and obesity are associated with structural and functional changes of the cardiovascular system including left atrial and ventricular remodeling, haemodynamic alterations, autonomic dysfunction, and diastolic dysfunction. Moreover, diabetic cardiomyopathy is characterized by an adverse structural and functional cardiac phenotype which may predispose to the development of AF [3]. In this review, we discuss the pathophysiological and mechanistic relationships between obesity, diabetes and AF, and the challenges posed in the management of this high-risk group of individuals.

Effects of bariatric surgery on human small artery function: evidence for reduction in perivascular adipocyte inflammation, and the restoration of normal anticontractile activity despite persistent obesity

Objectives

The aim of this study was to investigate the effects of bariatric surgery on small artery function and the mechanisms underlying this.

Background

In lean healthy humans, perivascular adipose tissue (PVAT) exerts an anticontractile effect on adjacent small arteries, but this is lost in obesity-associated conditions such as the metabolic syndrome and type II diabetes where there is evidence of adipocyte inflammation and increased oxidative stress.

Methods

Segments of small subcutaneous artery and perivascular fat were harvested from severely obese individuals before (n = 20) and 6 months after bariatric surgery (n = 15). Small artery contractile function was examined in vitro with wire myography, and perivascular adipose tissue (PVAT) morphology was assessed with immunohistochemistry.

Results

The anticontractile activity of PVAT was lost in obese patients before surgery when compared with healthy volunteers and was restored 6 months after bariatric surgery. In vitro protocols with superoxide dismutase and catalase rescued PVAT anticontractile function in tissue from obese individuals before surgery. The improvement in anticontractile function after surgery was accompanied by improvements in insulin sensitivity, serum glycemic indexes, inflammatory cytokines, adipokine profile, and systolic blood pressure together with increased PVAT adiponectin and nitric oxide bioavailability and reduced macrophage infiltration and inflammation. These changes were observed despite the patients remaining severely obese.

Conclusions

Bariatric surgery and its attendant improvements in weight, blood pressure, inflammation, and metabolism collectively reverse the obesity-induced alteration to PVAT anticontractile function. This reversal is attributable to reductions in local adipose inflammation and oxidative stress with improved adiponectin and nitric oxide bioavailability.

A simple new non-invasive sweat indicator test for the diagnosis of diabetic neuropathy

A simple non-invasive indicator test (Neuropad(®)) has been developed for the assessment of sweating and, hence, cholinergic innervation in the diabetic foot. The present review summarizes current knowledge on this diagnostic test. The diagnostic ability of this test is based on a colour change from blue to pink at 10 min, with excellent reproducibility, which lends itself to patient self-examination. It has a high sensitivity (65.1-100%) and negative predictive value (63-100%), with moderate specificity (32-78.5%) and positive predictive value (23.3-93.2%) for the diagnosis of diabetic peripheral neuropathy. It also has moderate to high sensitivity (59.1-89%) and negative predictive value (64.7-91%), but low to moderate specificity (27-78%) and positive predictive value (24-48.6%) for the diagnosis of diabetic cardiac autonomic neuropathy. There are some data to suggest that Neuropad can detect early diabetic neuropathy, but this needs further evaluation. It remains to be established whether this test can predict foot ulceration and amputation, thereby contributing to the identification of high-risk patients.

A phase 2a, randomized, double-blind 28-day study of TZP-102 a ghrelin receptor agonist for diabetic gastroparesis

BACKGROUND

Gastroparesis causes significant morbidity and treatment options are limited. TZP-102 a novel, macrocyclic, selective, oral ghrelin receptor agonist, was evaluated in a randomized, double-blind, placebo-controlled trial in patients with diabetic gastroparesis.

METHODS

A total of 92 outpatients were randomized to once-daily administrations of 10-mg (n = 22), 20-mg (n = 21), 40-mg (n = 23) TZP-102 or placebo (n = 26). The primary endpoint was the change from baseline in gastric half-emptying time (T(½)) utilizing (13)C-breath test methodology and secondary endpoints included symptom improvement using patient-reported gastroparesis symptom scores (PAGI-SYM questionnaire) and patient and physician overall treatment evaluations (OTE).

KEY RESULTS

Gastric T½ changes were not statistically significant between TZP-102 and placebo after 28 days of treatment at any dose. Clinical improvements (-1.0 to -1.4 point mean decrease in symptom severity) occurred in the Gastroparesis Cardinal Symptom Index (GCSI) component of the PAGI-SYM, which was significant vs placebo for all TZP-102 doses combined. Improvements became evident after 1 week of treatment. Significantly, more patients given TZP-102 (any dose) had a 50% reduction in baseline GCSI score (28.8%vs 7.7% placebo). Safety profiles were similar across groups. All TZP-102 doses were well-tolerated with no adverse cardiac, weight, or glucose control outcomes.

CONCLUSIONS & INFERENCES

TZP-102 for 28 days, at doses of 10-40 mg once daily, was well-tolerated and resulted in a reduction in symptoms of gastroparesis. The lack of correlation between symptom improvement and gastric emptying change is consistent with previous studies in diabetic gastroparesis, and emphasizes the value of patient-defined outcomes in determining therapeutic benefit.

Corneal confocal microscopy detects early nerve regeneration in diabetic neuropathy after simultaneous pancreas and kidney transplantation

Diabetic neuropathy is associated with increased morbidity and mortality. To date, limited data in subjects with impaired glucose tolerance and diabetes demonstrate nerve fiber repair after intervention. This may reflect a lack of efficacy of the interventions but may also reflect difficulty of the tests currently deployed to adequately assess nerve fiber repair, particularly in short-term studies. Corneal confocal microscopy (CCM) represents a novel noninvasive means to quantify nerve fiber damage and repair. Fifteen type 1 diabetic patients undergoing simultaneous pancreas-kidney transplantation (SPK) underwent detailed assessment of neurologic deficits, quantitative sensory testing (QST), electrophysiology, skin biopsy, corneal sensitivity, and CCM at baseline and at 6 and 12 months after successful SPK. At baseline, diabetic patients had a significant neuropathy compared with control subjects. After successful SPK there was no significant change in neurologic impairment, neurophysiology, QST, corneal sensitivity, and intraepidermal nerve fiber density (IENFD). However, CCM demonstrated significant improvements in corneal nerve fiber density, branch density, and length at 12 months. Normalization of glycemia after SPK shows no significant improvement in neuropathy assessed by the neurologic deficits, QST, electrophysiology, and IENFD. However, CCM shows a significant improvement in nerve morphology, providing a novel noninvasive means to establish early nerve repair that is missed by currently advocated assessment techniques.

A pocket-sized disposable device for testing the integrity of sensation in the outpatient setting

AIMS

To compare the Ipswich Touch Test and the VibraTip with the Neuropathy Disability Score and the vibration perception threshold for detecting the 'at-risk' foot.

METHODS

We directly compared the Ipswich Touch Test and the VibraTip with both the Neuropathy Disability Score ≥ 6 and the vibration perception threshold ≥ 25 V indicating 'at-risk' feet in 83 individuals.

RESULTS

The vibration perception threshold and Neuropathy Disability Score tests exhibited almost perfect agreement with each other (P < 0.001). The VibraTip and Ipswich Touch Test results were identical (P < 0.001). The VibraTip and Ipswich Touch Test results also exhibited almost perfect agreement with the vibration perception threshold (P < 0.001) and the Neuropathy Disability Score (P < 0.001).

CONCLUSIONS

These two simple and efficient tests are easy to teach, reliable and can be used in any setting, and neither requires an external power source. We conclude that both the VibraTip and the Ipswich Touch Test are reliable and sensitive tests for identifying the 'high-risk' foot.

Corneal confocal microscopy detects small-fiber neuropathy in Charcot-Marie-Tooth disease type 1A patients

INTRODUCTION

Although unmyelinated nerve fibers are affected in Charcot-Marie-Tooth type 1A (CMT1A) disease, they have not been studied in detail due to the invasive nature of the techniques needed to study them. We established alterations in C-fiber bundles of the cornea in patients with CMT1A using non-invasive corneal confocal microscopy (CCM).

METHODS

Twelve patients with CMT1A and 12 healthy control subjects underwent assessment of neuropathic symptoms and deficits, electrophysiology, quantitative sensory testing, corneal sensitivity, and corneal confocal microscopy.

RESULTS

Corneal sensitivity, corneal nerve fiber density, corneal nerve branch density, corneal nerve fiber length, and corneal nerve fiber tortuosity were significantly reduced in CMT1A patients compared with controls. There was a significant correlation between corneal sensation and CCM parameters with the severity of painful neuropathic symptoms, cold and warm thresholds, and median nerve CMAP amplitude.

CONCLUSIONS

CCM demonstrates significant damage to C-fiber bundles, which relates to some measures of neuropathy in CMT1A patients.

Assessing corneal nerve structure and function in diabetic neuropathy

The accurate detection and quantification of human diabetic peripheral neuropathy are important to define at-risk patients, anticipate deterioration and assess new therapies. Two emerging ophthalmic techniques, namely, corneal confocal microscopy and corneal aesthesiometry, demonstrate the ability to diagnose, quantify severity and assess therapeutic benefit in diabetic peripheral neuropathy. Corneal confocal microscopy allows quantification of corneal nerve morphology and non-contact corneal aesthesiometry assesses corneal sensitivity. The present review provides a detailed critique of the rationale, practical application in terms of the instruments used to capture images and the basis on which images are interpreted and analysed. We also critically evaluate how these two new non-invasive ophthalmic tests can be deployed to diagnose diabetic and other peripheral neuropathies.

Relationship of endothelial function and atherosclerosis to treatment response in late-life depression

OBJECTIVE

Treatment response in late-life depression has been linked to cerebrovascular disease notably via the vascular depression hypothesis. This study investigated the relationship between endothelial function and atherosclerosis and treatment response to antidepressant monotherapy.

METHODS

Twenty five patients with late-life depression were compared with 21 non-depressed control subjects in a case control study. Nine of the depressed subjects were responders to antidepressant monotherapy and 16 were not. Vascular measures included assessment of carotid intima media thickness (IMT) representing atherosclerosis and biopsied small artery dilatation to acetylcholine to assess endothelial function in a subset of subjects.

RESULTS

There were no group differences in vascular risks or sociodemographic variables. There was a significant group difference (responders versus non-responders versus controls) on both IMT and endothelial function (p < 0.01 and p < 0.05, respectively) with a significant difference between controls and non-responders (p < 0.001) on IMT and between controls and responders (p < 0.05) and control versus non-responders (p < 0.05) on endothelial function but no significant difference between responders and non-responders. On both IMT and endothelial function, there was a gradient across groups, with control subjects having best vascular structure or function, non-responders worse and responders in-between.

CONCLUSIONS

The results are consistent with a hypothesis that poorer antidepressant response in later life depressive disorder may be linked to an underlying vascular dysfunction and pathology. The study is small, and the results require replication but if confirmed, trials with vasoprotective medication aimed at improving vascular function in order to alter the prognosis of late-life depression would be a rational development.

Retinal nerve fibre layer thinning associated with diabetic peripheral neuropathy

AIMS

To investigate the relationship between retinal nerve fibre layer thickness and peripheral neuropathy in patients with Type 2 diabetes, particularly in those who are at higher risk of foot ulceration.

METHODS

Global and sectoral retinal nerve fibre layer thicknesses were measured at 3.45 mm diameter around the optic nerve head using optical coherence tomography (OCT). The level of neuropathy was assessed in 106 participants (82 with Type 2 diabetes and 24 healthy controls) using the 0-10 neuropathy disability score. Participants were stratified into four neuropathy groups: none (0-2), mild (3-5), moderate (6-8), and severe (9-10). A neuropathy disability score ≥ 6 was used to define those at higher risk of foot ulceration. Multivariable regression analysis was performed to assess the effect of neuropathy disability scores, age, disease duration and retinopathy on RNFL thickness.

RESULTS

Inferior (but not global or other sectoral) retinal nerve fibre layer thinning was associated with higher neuropathy disability scores (P = 0.03). The retinal nerve fibre layer was significantly thinner for the group with neuropathy disability scores ≥ 6 in the inferior quadrant (P < 0.005). Age, duration of disease and retinopathy levels did not significantly influence retinal nerve fibre layer thickness. Control participants did not show any significant differences in thickness measurements from the group with diabetes and no neuropathy (P > 0.24 for global and all sectors).

CONCLUSIONS

Inferior quadrant retinal nerve fibre layer thinning is associated with peripheral neuropathy in patients with Type 2 diabetes, and is more pronounced in those at higher risk of foot ulceration.

Utility of corneal confocal microscopy for assessing mild diabetic neuropathy: baseline findings of the LANDMark study

BACKGROUND

For those in the field of managing diabetic complications, the accurate diagnosis and monitoring of diabetic peripheral neuropathy (DPN) continues to be a challenge. Assessment of sub-basal corneal nerve morphology has recently shown promise as a novel ophthalmic marker for the detection of DPN.

METHODS

Two hundred and thirty-one individuals with diabetes with predominantly mild or no neuropathy and 61 controls underwent evaluation of diabetic neuropathy symptom score, neuropathy disability score, testing with 10 g monofilament, quantitative sensory testing (warm, cold, vibration detection) and nerve conduction studies. Corneal nerve fibre length, branch density and tortuosity were measured using corneal confocal microscopy. Differences in corneal nerve morphology between individuals with and without DPN and controls were investigated using analysis of variance and correlations were determined between corneal morphology and established tests of, and risk factors for, DPN.

RESULTS

Corneal nerve fibre length was significantly reduced in diabetic individuals with mild DPN compared with both controls (p < 0.001) and diabetic individuals without DPN (p = 0.012). Corneal nerve branch density was significantly reduced in individuals with mild DPN compared with controls (p = 0.032). Corneal nerve fibre tortuosity did not show significant differences. Corneal nerve fibre length and corneal nerve branch density showed modest correlations to most measures of neuropathy, with the strongest correlations to nerve conduction study parameters (r = 0.15 to 0.25). Corneal nerve fibre tortuosity showed only a weak correlation to the vibration detection threshold. Corneal nerve fibre length was inversely correlated to glycated haemoglobin (r = -0.24) and duration of diabetes (r = -0.20).

CONCLUSION

Assessment of corneal nerve morphology is a non-invasive, rapid test capable of showing differences between individuals with and without DPN. Corneal nerve fibre length shows the strongest associations with other diagnostic tests of neuropathy and with established risk factors for neuropathy.

Corneal sensitivity is related to established measures of diabetic peripheral neuropathy

PURPOSE

The objective was to investigate the association between corneal sensitivity and established measures of diabetic peripheral neuropathy (DPN).

METHODS

Corneal sensitivity was measured in 93 individuals with diabetes, 146 diabetic individuals without neuropathy and 61 control individuals without diabetes or neuropathy using a non-contact corneal aesthesiometer at the baseline visit of a five-year longitudinal natural history study of DPN. The correlation between corneal sensitivity and established measures of neuropathy was estimated and multi-dimensional scaling was used to represent similarities and dissimilarities between variables.

RESULTS

The corneal sensitivity threshold was significantly correlated with a majority of established measures of DPN. Correlation coefficients ranged from -0.32 to 0.26. Using multi-dimensional scaling, non-contact corneal aesthesiometry was closer to the neuropathy disability score, diabetic neuropathy symptom score and Neuropad and most dissimilar to electrophysiological parameters and quantitative sensory testing.

CONCLUSION

Corneal sensitivity, although not strongly related, is associated with other functional measures of DPN and might provide a useful adjunct in identifying functional loss of small nerve fibre integrity.

Visual sensitivity loss in the central 30° of visual field is associated with diabetic peripheral neuropathy

AIMS/HYPOTHESIS

Impaired central vision has been shown to predict diabetic peripheral neuropathy (DPN). Several studies have demonstrated diffuse retinal neurodegenerative changes in diabetic patients prior to retinopathy development, raising the prospect that non-central vision may also be compromised by primary neural damage. We hypothesise that type 2 diabetic patients with DPN exhibit visual sensitivity loss in a distinctive pattern across the visual field, compared with a control group of type 2 diabetic patients without DPN.

METHODS

Increment light sensitivity was measured by standard perimetry in the central 30° of visual field for two age-matched groups of type 2 diabetic patients, with and without neuropathy (n = 40/30). Neuropathy status was assigned using the neuropathy disability score. Mean visual sensitivity values were calculated globally, for each quadrant and for three eccentricities (0-10°, 11-20° and 21-30°). Data were analysed using a generalised additive mixed model (GAMM).

RESULTS

Global and quadrant between-group visual sensitivity mean differences were marginally but consistently lower (by about 1 dB) in the neuropathy cohort compared with controls. Between-group mean differences increased from 0.36 to 1.81 dB with increasing eccentricity. GAMM analysis, after adjustment for age, showed these differences to be significant beyond 15° eccentricity and monotonically increasing. Retinopathy levels and disease duration were not significant factors within the model (p = 0.90).

CONCLUSIONS/INTERPRETATION

Visual sensitivity reduces disproportionately with increasing eccentricity in type 2 diabetic patients with peripheral neuropathy. This sensitivity reduction within the central 30° of visual field may be indicative of more consequential loss in the far periphery.

Small fibre neuropathy: role in the diagnosis of diabetic sensorimotor polyneuropathy

Small fibres constitute 70-90% of peripheral nerve fibres and regulate several key functions such as tissue blood flow, temperature and pain perception as well as sweating, all of which are highly relevant to the clinical presentation and adverse outcomes associated with foot ulcerations in patients with diabetes. Recent studies demonstrated significant abnormalities in the small fibres in subjects with impaired glucose tolerance and diabetes, despite normal electrophysiology, suggesting that the earliest nerve fibre damage is to the small fibres. Unfortunately, guidelines and consensus statements focus on large fibres and continue to advocate electrophysiology as a diagnostic modality and as a primary end point for the assessment of therapeutic benefit. (In part, this reflects the difficulties in quantifying small fibre dysfunction and damage.) We have therefore critically assessed currently available techniques that measure small fibre dysfunction in diabetic neuropathy, using quantitative sensory and sudomotor testing. We have assessed the role of identifying structural damage by quantifying intraepidermal nerve fibre density in skin biopsies and corneal nerve morphology using corneal confocal microscopy. Finally, we propose a definition for diabetic neuropathy that incorporates small fibre damage.

Corneal confocal microscopy detects improvement in corneal nerve morphology with an improvement in risk factors for diabetic neuropathy

AIM

We have assessed whether corneal confocal microscopy can be used to detect alterations in nerve morphology following an improvement in risk factors associated with diabetic neuropathy.

METHODS

Twenty-five patients with diabetes with mild to moderate neuropathy and 18 control subjects underwent corneal confocal microscopy to quantify corneal nerve fibre (density, branch density, length and tortuosity) at baseline and after 24 months from first visit. This was not planned as an intervention trial and was simply an observational follow-up.

RESULTS

At baseline, nerve fibre density (18.8 ± 2.1 vs. 46.0 ± 3.8 number/mm(2), P = 0.001), nerve branch density (6.9 ± 1.5 vs. 35.6 ± 6.7 number/mm(2), P < 0.0001), nerve fibre length (8.3 ± 0.9 vs. 13.5 ± 0.8 mm/mm(2), P < 0.0001) and nerve fibre tortuosity (19.8 ± 1.6 vs. 22.7 ± 2.2, P < 0.05) were significantly lower in patients with diabetes than in control subjects. At follow-up, glycaemic control (HbA(1c) 64 ± 3 to 58 ± 2 mmol/mol, P = 0.08), total cholesterol (4.9 ± 0.2 to 4.2 ± 0.2 mmol/l, P = 0.01), systolic blood pressure (145.8 ± 4.9 to 135.9 ± 3.7 mmHg, P = 0.09) and diastolic blood pressure (77.8 ± 2.7 to 70.8 ± 2.5, P = 0.03) improved. Nerve fibre density (24.1 ± 2.0, P = 0.05), nerve branch density (11.1 ± 1.3, P < 0.01) and nerve fibre tortuosity (22.6 ± 1.5, P = 0.05) increased significantly, with no change in nerve fibre length (8.4 ± 0.5). Improvement in nerve fibre density correlated significantly with the improvement in HbA(1c) (r = -0.51, P = 0.008). Via four multifactorial regressions, this confirms the negative association between HbA(1c) and nerve fibre density (P = 0.02).

CONCLUSIONS

This study shows that corneal confocal microscopy may be employed in longitudinal studies to assess progression of human diabetic neuropathy and also supports the hypothesis that improvements in risk factors for diabetic neuropathy, in particular HbA(1c) , may lead to morphological repair of nerve fibres.