Nerve Fiber Length Research Articles

Decreased corneal subbasal nerve fiber length and density in diabetic dogs with cataracts using in vivo confocal microscopy.

To determine whether there is a difference in corneal sensitivity and corneal subbasal nerve plexus (CSNP) morphology in cataractous dogs with diabetes mellitus (DM) versus without DM. Twenty six domestic dogs with cataracts of various breeds presented for phacoemulsification, 13 with DM and 13 without DM. The inclusion criteria for the study were dogs with bilateral cataracts and no clinical evidence of corneal disease. The diabetic group had documented hyperglycemia and was currently treated with insulin. The non-diabetic group had no evidence of DM on examination and bloodwork. Complete ophthalmic examination, corneal esthesiometry, and in vivo confocal microscopy of the CSNP was performed for both eyes of each dog. The CSNP was evaluated using a semi-automated program and statistically analyzed. The mean (±SD) CSNP fiber length was significantly decreased in diabetic (3.8 ± 3.0 mm/mm2 ) versus non-diabetic (6.7 ± 1.9 mm/mm2 ) dogs. Likewise, the mean (±SD) fiber density was significantly decreased in diabetic (8.3 ± 3.1 fibers/mm2 ) versus non-diabetic (15.5 ± 4.9 fibers/mm2 ) dogs. The corneal touch threshold was significantly reduced in diabetic (2.1 ± 0.8cm) versus non-diabetic (2.8 ± 0.4cm) dogs. There was a non-significant trend towards subclinical keratitis in diabetic (9/13) versus non-diabetic (4/13) dogs. Morphological and functional abnormalities of the CSNP were present in dogs with DM, including decreased fiber length, fiber density, and corneal sensitivity. These findings are consistent with diabetic neuropathy and could contribute to clinically significant corneal complications after cataract surgery.

Diagnostic Accuracy of Perception Threshold Tracking in the Detection of Small Fiber Damage in Type 1 Diabetes.

An objective assessment of small nerve fibers is key to the early detection of diabetic peripheral neuropathy (DPN). This study investigates the diagnostic accuracy of a novel perception threshold tracking technique in detecting small nerve fiber damage. Participants with type 1 diabetes (T1DM) without DPN (n = 20), with DPN (n = 20), with painful DPN (n = 20) and 20 healthy controls (HCs) underwent perception threshold tracking on the foot and corneal confocal microscopy. Diagnostic accuracy of perception threshold tracking compared to corneal confocal microscopy was analyzed using logistic regression. The rheobase, corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), and corneal nerve fiber length (CNFL) (all P < .001) differed between groups. The diagnostic accuracy of perception threshold tracking (rheobase) was excellent for identifying small nerve fiber damage, especially for CNFL with a sensitivity of 94%, specificity 94%, positive predictive value 97%, and negative predictive value 89%. There was a significant correlation between rheobase with CNFD, CNBD, CNFL, and Michigan Neuropathy Screening Instrument (all P < .001). Perception threshold tracking had a very high diagnostic agreement with corneal confocal microscopy for detecting small nerve fiber loss and may have clinical utility for assessing small nerve fiber damage and hence early DPN. NCT04078516.

Corneal nerve loss and increased Langerhans cells are associated with disease severity in patients with rheumatoid arthritis.

Rheumatoid arthritis (RA) is a multisystem autoimmune disorder characterized by articular and extra-articular manifestations. Neuropathy is a poorly studied manifestation of RA. The aim of this study was to utilize the rapid non-invasive ophthalmic imaging technique of corneal confocal microscopy to identify whether there is evidence of small nerve fibre injury and immune cell activation in patients with RA. Fifty consecutive patients with RA and 35 healthy control participants were enrolled in this single-centre, cross-sectional study conducted at a university hospital. Disease activity was assessed with the 28-Joint Disease Activity Score and erythrocyte sedimentation rate (DAS28-ESR). Central corneal sensitivity was measured with a Cochet-Bonnet contact corneal esthesiometer. A laser scanning in vivo corneal confocal microscope was used to quantify corneal nerve fibre density (CNFD), nerve branch density (CNBD), nerve fibre length (CNFL), and Langerhans cell (LC) density. Corneal sensitivity (P = 0.01), CNFD (P = 0.02), CNBD (P < 0.001), and CNFL (P < 0.001) were lower, and mature (P = 0.001) and immature LC densities (P = 0.011) were higher in patients with RA compared to control subjects. CNFD (P = 0.016) and CNFL (P = 0.028) were significantly lower in patients with moderate to high (DAS28-ESR > 3.2) compared to mild (DAS28-ESR ≤ 3.2) disease activity. Furthermore, the DAS28-ESR score correlated with CNFD (r = -0.425; P = 0.002), CNBD (ρ = -0.362; P = 0.010), CNFL (r = -0.464; P = 0.001), total LC density (ρ = 0.362; P = 0.010) and immature LC density (ρ = 0.343; P = 0.015). This study demonstrates reduced corneal sensitivity, corneal nerve fibre loss and increased LCs which were associated with the severity of disease activity in patients with RA.

Assessing Corneal Confocal Microscopy and Other Small Fiber Measures in Diabetic Polyneuropathy.

Damage to small nerve fibers is common in diabetic polyneuropathy (DPN), and the diagnosis of DPN relies on subjective symptoms and signs in a combination with objective confirmatory tests, typically electrophysiology or intraepidermal nerve fiber density (IENFD) from skin biopsy. Corneal confocal microscopy (CCM) has been introduced as a tool to detect DPN. However, it is unclear if CCM can reliably be used to diagnose DPN and how the technique compares with other commonly used measures of small fiber damage, such as IENFD, cold detection threshold (CDT), and warm detection threshold (WDT). Therefore, we assessed and compared the use of CCM, IENFD, CDT, and WDT in the diagnosis of DPN in patients with type 2 diabetes. In this cohort study, the participants underwent detailed neurologic examination, electrophysiology, quantification of IENFD, CCM, and quantitative sensory testing. Definition of DPN was made in accordance with the Toronto criteria for diabetic neuropathy (without relying on IENFD and thermal thresholds). A total of 214 patients with at least probable DPN, 63 patients without DPN, and 97 controls without diabetes were included. Patients with DPN had lower CCM measures (corneal nerve fiber length [CNFL], nerve fiber density, and branch density), IENFD, CDT, and WDT compared with patients without DPN (p ≤ 0.001, <0.001, 0.002, p < 0.001, p = 0.003, and <0.005, respectively), whereas there was no difference between controls and patients with diabetes without DPN. All 3 CCM measures showed a very low diagnostic sensitivity with CNFL showing the highest (14.4% [95% CI 9.8-18.4]) and a specificity of 95.7% (88.0-99.1). In comparison, the sensitivity of abnormal CDT and/or WDT was 30.5% (24.4-37.0) with a specificity of 84.9% (74.6-92.2). The sensitivity of abnormal IENFD was highest among all measures with a value of 51.1% (43.7-58.5) and a specificity of 90% (79.5-96.2). CCM measures did not correlate with IENFD, CDT/WDT, or neuropathy severity in the group of patients with DPN. CCM measures showed the lowest sensitivity compared with other small fiber measures in the diagnosis of DPN. This indicates that CCM is not a sensitive method to detect DPN in recently diagnosed type 2 diabetes. This study provides Class III evidence that CCM measures aid in the detection of DPN in recently diagnosed type 2 diabetics but with a low sensitivity when compared with other small fiber measures.

In Vivo Corneal Confocal Microscopy in Multiple Sclerosis: Can it Differentiate Disease Relapse in Multiple Sclerosis?

This study aims to investigate the role of in vivo corneal confocal microscopy (IVCCM) in the detection of corneal inflammatory activity and subbasal nerve alterations in patients with multiple sclerosis (MS) and to further determine whether IVCCM can be used to detect (acute) disease relapse. Prospective cross-sectional study, with a subgroup follow-up. This single-center study included 58 patients with MS (MS-Relapse group [n=27] and MS-Remission group [n=31]), and 30 age- and sex-matched healthy control subjects. Patients with a history of optic neuritis or trigeminal symptoms were excluded. Corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), corneal nerve fiber length (CNFL), and dendritic cell (DC) density were evaluated in all patients with MS and control subjects by IVCCM. Patients in the MS-Relapse group who were in remission for ≥6 months after the MS incident underwent a repeat IVCCM. No statistical difference was observed between the MS-Relapse and MS-Remission groups regarding age, sex, MS duration, and the number of relapses (P > .05). Compared with healthy control subjects, all subbasal nerve parameters were significantly lower (CNFD: P < .001, CNFL: P < .001, CNBD: P < .001), and the DC density was significantly higher (P=.023) in patients with MS. However, no significant difference was observed between MS-Relapse and MS-Remission groups in terms of CNFD (mean [SE] difference -2.05 [1.69] fibers/mm2 [95% confidence interval {CI} -1.32 to 5.43]; P < .227), CNFL (mean [SE] difference -1.10 [0.83] mm/mm2 [95% CI -0.56 to 2.75]; P < .190), CNBD (mean [SE] difference -3.91 [2.48] branches/mm2 [95% CI -1.05 to 8.87]; P < .120), and DC density (median [IQR], 59.38 [43.75-85.0] vs 75.0 [31.25-128.75]; P=.596). The repeat IVCCM in relapse patients (n=16 [59.3%]) showed a significant increase in CNFD (P=.036) and CNBD (P=.018), but no change was observed in CNFL (P=.075) and DC density (P=.469). Although increased inflammation and neurodegeneration can be demonstrated in patients with MS compared with healthy control subjects, a single time point evaluation of IVCCM does not seem to be sufficient to confirm the occurrence of relapse in patients with MS. However, IVCCM holds promise for demonstrating early neuroregeneration in patients with MS.

The severity of corneal nerve loss differentiates motor subtypes in patients with Parkinson's disease.

Parkinson's disease (PD) is a heterogeneous movement disorder with patients manifesting with either tremor-dominant (TD) or postural instability and gait disturbance (PIGD) motor subtypes. Small nerve fiber damage occurs in patients with PD and may predict motor progression, but it is not known whether it differs between patients with different motor subtypes. The aim of this study was to explore whether there was an association between the extent of corneal nerve loss and different motor subtypes. Patients with PD classified as TD, PIGD, or mixed subtype underwent detailed clinical and neurological evaluation and corneal confocal microscopy (CCM). Corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), and corneal nerve fiber length (CNFL) were compared between groups, and the association between corneal nerve fiber loss and motor subtypes was investigated. Of the 73 patients studied, 29 (40%) had TD, 34 (46%) had PIGD, and 10 (14%) had a mixed subtype. CNFD (no./mm2, 24.09 ± 4.58 versus 28.66 ± 4.27; p < 0.001), CNBD (no./mm2, 28.22 ± 11.11 versus 37.37 ± 12.76; p = 0.015), and CNFL (mm/mm2, 13.11 ± 2.79 versus 16.17 ± 2.37; p < 0.001) were significantly lower in the PIGD group compared with the TD group. Multivariate logistic regression showed that higher CNFD (OR = 1.265, p = 0.019) and CNFL (OR = 1.7060, p = 0.003) were significantly associated with the TD motor subtype. The receiver operating characteristic (ROC) analysis demonstrated that combined corneal nerve metrics showed excellent discrimination between TD and PIGD, with an area under the curve (AUC) of 0.832. Greater corneal nerve loss occurs in patients with PIGD compared with TD, and patients with a higher CNFD or CNFL were more likely to have the TD subtype. CCM may have clinical utility in differentiating different motor subtypes in PD.

Corneal axonal loss as an imaging biomarker of neurodegeneration in multiple sclerosis: a longitudinal study.

Resourceful endpoints of axonal loss are needed to predict the course of multiple sclerosis (MS). Corneal confocal microscopy (CCM) can detect axonal loss in patients with clinically isolated syndrome and established MS, which relates to neurological disability. To assess corneal axonal loss over time in relation to retinal atrophy, and neurological and radiological abnormalities in MS. Patients with relapsing-remitting (RRMS) (n = 68) or secondary progressive MS (SPMS) (n = 15) underwent CCM and optical coherence tomography. Corneal nerve fibre density (CNFD-fibres/mm2), corneal nerve branch density (CNBD-branches/mm2), corneal nerve fibre length (CNFL-mm/mm2) and retinal nerve fibre layer (RNFL-μm) thickness were quantified along with neurological and radiological assessments at baseline and after 2 years of follow-up. Age-matched, healthy controls (n = 20) were also assessed. In patients with RRMS compared with controls at baseline, CNFD (p = 0.004) and RNFL thickness (p < 0.001) were lower, and CNBD (p = 0.003) was higher. In patients with SPMS compared with controls, CNFD (p < 0.001), CNFL (p = 0.04) and RNFL thickness (p < 0.001) were lower. For identifying RRMS, CNBD had the highest area under the receiver operating characteristic (AUROC) curve (0.99); and for SPMS, CNFD had the highest AUROC (0.95). At follow-up, there was a further significant decrease in CNFD (p = 0.04), CNBD (p = 0.001), CNFL (p = 0.008) and RNFL (p = 0.002) in RRMS; in CNFD (p = 0.04) and CNBD (p = 0.002) in SPMS; and in CNBD (p = 0.01) in SPMS compared with RRMS. Follow-up corneal nerve loss was greater in patients with new enhancing lesions and optic neuritis history. Progressive corneal and retinal axonal loss was identified in patients with MS, especially those with more active disease. CCM may serve as an imaging biomarker of axonal loss in MS.

Impact of Chronic Kidney Disease on Corneal Neuroimmune Features in Type 2 Diabetes.

Aim: To determine the impact of chronic kidney disease on corneal nerve measures and dendritic cell counts in type 2 diabetes. Methods: In vivo corneal confocal microscopy images were used to estimate corneal nerve parameters and compared in people with type 2 diabetes with chronic kidney disease (T2DM-CKD) (n = 29) and those with type 2 diabetes without chronic kidney disease (T2DM-no CKD) (n = 29), along with 30 healthy controls. Corneal dendritic cell densities were compared between people with T2DM-CKD and those with T2DM-no CKD. The groups were matched for neuropathy status. Results: There was a significant difference in corneal nerve fiber density (p < 0.01) and corneal nerve fiber length (p = 0.04) between T2DM-CKD and T2DM-no CKD groups. The two diabetes groups had reduced corneal nerve parameters compared to healthy controls (all parameters: p < 0.01). Immature central dendritic cell density was significantly higher in the T2DM-CKD group compared to the T2DM-no CKD group ((7.0 (3.8−12.8) and 3.5 (1.4−13.4) cells/mm2, respectively, p < 0.05). Likewise, central mature dendritic cell density was significantly higher in the T2DM-CKD group compared to the T2DM-no CKD group (0.8 (0.4−2.2) and 0.4 (0.6−1.1) cells/mm2, respectively, p = 0.02). Additionally, total central dendritic cell density was increased in the T2DM-CKD group compared to T2DM-no CKD group (10.4 (4.3−16.1) and 3.9 (2.1−21.0) cells/mm2, respectively, p = 0.03). Conclusion: The study showed that central corneal dendritic cell density is increased in T2DM-CKD compared to T2DM-no CKD, with groups matched for peripheral neuropathy severity. This is accompanied by a loss of central corneal nerve fibers. The findings raise the possibility of additional local factors exacerbating central corneal nerve injury in people with diabetic chronic kidney disease.

In vivo confocal microscopy demonstrates longitudinal bilateral changes of corneal immune cells and nerves in herpetic keratitis

AbstractPurpose: To analyse bilateral corneal immune cell and nerve alterations in patients with unilateral herpes zoster ophthalmicus (HZO) by laser in vivo confocal microscopy (IVCM) and their correlation with corneal sensation and clinical findings.Materials and methods: This is a prospective, cross‐sectional, controlled, single‐center study. Twenty‐four eyes of 24 HZO patients and their contralateral clinically unaffected eyes and normal controls (n = 24) were included. Laser IVCM (Heidelberg Retina Tomograph/Rostock Cornea Module), corneal esthesiometry (Cochet‐Bonnet) were performed. Changes in corneal dendritiform cell (DC) density and morphology, number and length of subbasal nerve fibres and their correlation to corneal sensation, pain, lesion location, disease duration, and number of episodes were analysed.Results: HZO‐affected and contralateral eyes showed a significant increase in DC influx of the central cornea as compared to controls (147.4 ± 33.9, 120.1 ± 21.2, and 23.0 ± 3.6 cells/mm2; p &lt; 0.0001). In HZO eyes DCs were larger in area (319.4 ± 59.8 μm2; p &lt; 0.001) and number of dendrites (3.5 ± 0.4 n/cell; p = 0.01) as compared to controls (52.2 ± 11.7, and 2.3 ± 0.5). DC density and size showed moderate negative correlation with total nerve length (R = −0.43 and R = −0.57, respectively; all p &lt; 0.001). A higher frequency of nerve beading and activated DCs close to nerve fibres were detected specifically in pain patients.Conclusions: Chronic unilateral HZO causes significant bilateral increase in corneal DC density and decrease of the corneal subbasal nerves as compared to controls. Negative correlation was observed for DC density and size to nerve parameters, suggesting interplay between the immune and nervous systems. Patients with chronic pain also showed increased nerve beading and activated DCs.

Continuous glucose monitoring reveals a novel association between duration and severity of hypoglycemia, and small nerve fiber injury in patients with diabetes.

Continuous glucose monitoring (CGM) has revealed that glycemic variability and low time in range are associated with albuminuria and retinopathy. We have investigated the relationship between glucose metrics derived from CGM and a highly sensitive measure of neuropathy using corneal confocal microscopy in participants with type 1 and type 2 diabetes. A total of 40 participants with diabetes and 28 healthy controls underwent quantification of corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), corneal nerve fiber length (CNFL) and inferior whorl length (IWL) and those with diabetes underwent CGM for four consecutive days. CNBD was significantly lower in patients with high glycemic variability (GV) compared to low GV (median (range) (25.0 (19.0-37.5) vs 38.6 (29.2-46.9); P = 0.007); in patients who spent >4% compared to <4% time in level 1 hypoglycemia (54-69 mg/dL) (25.0 (22.9-37.5) vs 37.5 (29.2-46.9); P = 0.045) and in patients who spent >1% compared to <1% time in level 2 hypoglycemia (<54 mg/dL) (25.0 (19.8-41.7) vs 35.4 (28.1-44.8); P = 0.04). Duration in level 1 hypoglycemia correlated with CNBD (r = -0.342, P = 0.031). Duration in level 1 (181-250 mg/dL) and level 2 (>250 mg/dL) hyperglycemia did not correlate with CNFD (P > 0.05), CNBD (P > 0.05), CNFL (P > 0.05) or IWL (P > 0.05). Greater GV and duration in hypoglycemia, rather than hyperglycemia, are associated with nerve fiber loss in diabetes.

Brain structural network to investigate the mechanism of cognitive impairment in patients with acoustic neuroma.

Acoustic neuroma (AN) is a common benign tumor. Little is known of neuropsychological studies in patients with acoustic neuroma, especially cognitive neuropsychology, and the neuropsychological abnormalities of patients affect their life quality. The purpose of this study was to explore the changes in the cognitive function of patients with acoustic neuroma, and the possible mechanism of these changes by structural magnetic resonance imaging. We used a neuropsychological assessment battery to assess cognitive function in 69 patients with acoustic neuroma and 70 healthy controls. Then, we used diffusion tensor imaging data to construct the structural brain network and calculate topological properties based on graph theory, and we studied the relation between the structural brain network and cognitive function. Moreover, three different subnetworks (short-range subnetwork, middle-range subnetwork, and long-range subnetwork) were constructed by the length of nerve fibers obtained from deterministic tracking. We studied the global and local efficiency of various subnetworks and analyzed the correlation between network metrics and cognitive function. Furthermore, connectome edge analysis directly assessed whether there were differences in the number of fibers in the different brain regions. We analyzed the relation between the differences and cognitive function. Compared with the healthy controls, the general cognitive function, memory, executive function, attention, visual space executive ability, visual perception ability, movement speed, and information processing speed decreased significantly in patients with acoustic neuroma. A unilateral hearing loss due to a left acoustic neuroma had a greater impact on cognitive function. The results showed that changes in the global and local metrics, the efficiency of subnetworks, and cognitively-related fiber connections were associated with cognitive impairments in patients with acoustic neuroma. Patients exhibit cognitive impairments caused by the decline of the structure and function in some brain regions, and they also develop partial compensation after cognitive decline. Cognitive problems are frequent in patients with acoustic neuroma. Including neuropsychological aspects in the routine clinical evaluation and appropriate treatments may enhance the clinical management and improve their life quality.

Impact of Peripheral and Corneal Neuropathy on Markers of Ocular Surface Discomfort in Diabetic Chronic Kidney Disease.

There is a reduction in corneal nerve fiber density and length in type 2 diabetes mellitus with chronic kidney disease compared with type 2 diabetes mellitus alone; however, this difference does not result in worse ocular surface discomfort or dry eye disease. This study aimed to determine the clinical impact of corneal nerve loss on ocular surface discomfort and markers of ocular surface homeostasis in people with type 2 diabetes mellitus without chronic kidney disease (T2DM-no CKD) and those with type 2 diabetes mellitus with concurrent chronic kidney disease (T2DM-CKD). Participants were classified based on estimated glomerular filtration rates into two groups: T2DM-CKD (n = 27) and T2DM-no CKD (n = 28). There was a significant difference between the T2DM-CKD and T2DM-no CKD groups in corneal nerve fiber density (14.9 ± 8.6 and 21.1 ± 7.1 no./mm 2 , respectively; P = .005) and corneal nerve fiber length (10.0 ± 4.6 and 12.3 ± 3.7 mm/mm 2 , respectively; P = .04). Fluorescein tear breakup time was significantly reduced in T2DM-CKD compared with T2DM-no CKD (8.1 ± 4.4 and 10.7 ± 3.8 seconds, respectively; P = .01), whereas ocular surface staining was not significantly different (3.5 ± 1.7 and 2.7 ± 2.3 scores, respectively; P = .12). In terms of ocular surface discomfort, there were no significant differences in the ocular discomfort score scores (12.5 ± 11.1 and 13.6 ± 12.1, respectively; P = .81) and Ocular Pain Assessment Survey scores (3.3 ± 5.4 and 4.3 ± 6.1, respectively; P = .37) between the T2DM-CKD and T2DM-no CKD. The current study demonstrated that corneal nerve loss is greater in T2DM-CKD than in T2DM-no CKD. However, these changes do not impact ocular surface discomfort or markers of ocular surface homeostasis.

Artificial Intelligence and Corneal Confocal Microscopy: The Start of a Beautiful Relationship.

Corneal confocal microscopy (CCM) is a rapid non-invasive in vivo ophthalmic imaging technique that images the cornea. Historically, it was utilised in the diagnosis and clinical management of corneal epithelial and stromal disorders. However, over the past 20 years, CCM has been increasingly used to image sub-basal small nerve fibres in a variety of peripheral neuropathies and central neurodegenerative diseases. CCM has been used to identify subclinical nerve damage and to predict the development of diabetic peripheral neuropathy (DPN). The complex structure of the corneal sub-basal nerve plexus can be readily analysed through nerve segmentation with manual or automated quantification of parameters such as corneal nerve fibre length (CNFL), nerve fibre density (CNFD), and nerve branch density (CNBD). Large quantities of 2D corneal nerve images lend themselves to the application of artificial intelligence (AI)-based deep learning algorithms (DLA). Indeed, DLA have demonstrated performance comparable to manual but superior to automated quantification of corneal nerve morphology. Recently, our end-to-end classification with a 3 class AI model demonstrated high sensitivity and specificity in differentiating healthy volunteers from people with and without peripheral neuropathy. We believe there is significant scope and need to apply AI to help differentiate between peripheral neuropathies and also central neurodegenerative disorders. AI has significant potential to enhance the diagnostic and prognostic utility of CCM in the management of both peripheral and central neurodegenerative diseases.

Implementation of corneal confocal microscopy for screening and early detection of diabetic neuropathy in primary care alongside retinopathy screening: Results from a feasibility study.

ObjectiveScreening for diabetic peripheral neuropathy (DPN) is essential for early detection and timely intervention. Quantitative assessment of small nerve fiber damage is key to the early diagnosis and assessment of its progression. Corneal confocal microscopy (CCM) is a non-invasive, in-vivo diagnostic technique that provides an accurate surrogate biomarker for small-fiber neuropathy. In this novel study for the first time, we introduced CCM to primary care as a screening tool for DPN alongside retinopathy screening to assess the level of neuropathy in this novel cohort.Research design and methods450 consecutive subjects with type 1 or type 2 diabetes attending for annual eye screening in primary care optometry settings underwent assessment with CCM to establish the prevalence of sub-clinical diabetic peripheral neuropathy. Subjects underwent assessment for neurological and ocular symptoms of diabetes and a history of diabetic foot disease, neuropathy and diabetic retinopathy (DR).ResultsCCM examination was completed successfully in 427 (94.9%) subjects, 22% of whom had neuropathy according to Diabetic Neuropathy Symptom (DNS) score. The prevalence of sub-clinical neuropathy as defined by abnormal corneal nerve fiber length (CNFL) was 12.9%. In the subjects with a short duration of type 2 diabetes, 9.2% had abnormal CNFL. CCM showed significant abnormalities in corneal nerve parameters in this cohort of subjects with reduction of corneal nerve fiber density (CNFD, p<0.001), CNFL (p<0.001) and corneal nerve branch density (CNBD, p<0.001) compared to healthy subjects. In subjects who had no evidence of DR (67% of all subjects), 12.0% had abnormal CNFL.ConclusionsCCM may be a sensitive biomarker for early detection and screening of DPN in primary care alongside retinopathy screening.

Mosaic vs. Single Image Analysis with Confocal Microscopy of the Corneal Nerve Plexus for Diagnosis of Early Diabetic Peripheral Neuropathy.

The assessment of the corneal nerve fibre plexus with corneal confocal microscopy (CCM) is an upcoming but still experimental method in the diagnosis of early stage diabetic peripheral neuropathy (DPN). Using an innovative imaging technique-Heidelberg Retina Tomograph equipped with the Rostock Cornea Module (HRT-RCM) and EyeGuidance module (EG)-we were able to look at greater areas of subbasal nerve plexus (SNP) in order to increase the diagnostic accuracy. The aim of our study was to evaluate the usefulness of EG instead of single image analysis in diagnosis of early stage DPN. This prospective study was performed on 60 patients with type2 diabetes mellitus, classified equally into two subgroups based on neuropathy deficient score (NDS): patients without DPN (group1) or with mild DPN (group2). The following parameters were analysed in the two subgroups: corneal nerve fibre length (CNFL; mm/mm2), corneal nerve fibre density (CNFD;no./mm2), corneal nerve branch density (CNBD;no./mm2). Furthermore, we compared the data calculated with the novel mosaic, EG-based method with those received from single image analysis using different quantification tools. Using EG we did not find a significant difference between group1 and group2: CNFL (16.81 ± 5.87mm/mm2 vs. 17.19 ± 7.19mm/mm2, p = 0.895), CNFD (254.05 ± 115.36no./mm2 vs. 265.91 ± 161.63no./mm2, p = 0.732) and CNBD (102.68 ± 62.28no./mm2 vs. 115.38 ± 96.91no./mm2, p = 0.541). No significant difference between the EG method of analysing the SNP and the single image analysis of 10 images per patient was detected. On the basis of our results it was not possible to differentiate between early stages of large nerve fibre DPN in patients with type2 diabetes mellitus via SNP analysis. To improve sensitivity and specificity of this method newer technologies are under current evaluation. ClinicalTrials.gov Identifier NCT05326958.

Association between systemic omega-3 polyunsaturated fatty acid levels, and corneal nerve structure and function

BackgroundOmega-3 polyunsaturated fatty acids (PUFAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have anti-inflammatory and neuroprotective properties. This study sought to determine the relationship between corneal parameters and systemic omega-3 fatty acid levels.MethodsForty-seven participants with no/mild peripheral neuropathy (26 with diabetes and 21 without) underwent comprehensive ocular surface and systemic PUFA assessments. Corneal anatomical parameters were assessed using in vivo confocal microscopy. Corneal sensitivity was measured using non-contact esthesiometry. Relationships between systemic PUFA levels and corneal parameters were evaluated with multiple linear regression, adjusted for age, sex, neuropathy symptom score, and presence of diabetes and dry eye disease. The relationship between corneal nerve fibre length (CNFL) and corneal sensitivity threshold was evaluated.ResultsThe median Omega-3 Index, a measure of erythrocyte EPA and DHA, was 5.21% (interquartile range: 4.44–5.94%) in the study population. Mean ( ± SD) CNFL was 13.53 ± 3.37 mm/mm2. Multiple linear regression showed that Omega-3 Index (β = 0.33; p = 0.02), age (β = −0.46; p = 0.001) and diabetes (β = −0.30; p = 0.03) were independently associated with CNFL (R2 = 0.39, p = 0.002). In a separate model, DHA (β = 0.32; p = 0.027) and age (β = −0.41; p = 0.003) were associated with CNFL (R2 = 0.37, p = 0.003). Neither systemic EPA nor omega-6 fatty acid levels correlated with CNFL. There was no association between PUFA levels and corneal sensitivity or corneal immune cell density. A negative correlation was found between CNFL and corneal sensation thresholds to a cooled stimulus in diabetes participants, in the central (ρ = −0.50; p = 0.009) and peripheral (ρ = −0.50; p = 0.01) cornea.ConclusionsA positive relationship between the systemic Omega-3 Index and corneal nerve parameters suggests omega-3 PUFA intake may influence corneal nerve architecture.

Stress-induced myelin damage in the hippocampal formation in a rat model of depression

BackgroundAccording to previous studies, myelin damage may be involved in the occurrence of depression. However, to date, no study has quantitatively investigated the changes in myelinated fibers and myelin sheaths in the hippocampal formation (HF) and hippocampal subfields in the context of depression. Methods: Male Sprague-Dawley (SD) rats (aged 4–5 weeks) were evenly divided into the control group and chronic unpredictable stress (CUS) group. Behavioral tests were performed, and then changes in myelinated fibers and myelin ultrastructure in hippocampal subfields in depression model rats were investigated using modern stereological methods and transmission electron microscopy techniques. Results: After a four-week CUS protocol, CUS rats showed depressive-like and anxiety-like behaviors. The total length and total volume of myelinated fibers were reduced in the CA1 region and DG in the CUS group compared with the control group. The total volumes of myelin sheaths and axons in the CA1 region but not in the DG were significantly lower in the CUS group than in the control group. The decrease in the total length of myelinated nerve fibers in the CA1 region in CUS rats was mainly due to a decrease in the length of myelinated fibers with a myelin sheath thickness of 0.15 μm–0.20 μm. Limitations: The exact relationship between the degeneration of myelin sheaths and depression-like, anxiety-like behaviors needs to be further investigated. Conclusions: CUS induces depression- and anxiety-like behaviors, and the demyelination in the CA1 region induced by 4 weeks of CUS might be an important structural basis for these behaviors.

Reproducibility and Reliability of Subbasal Corneal Nerve Parameters of the Inferior Whorl in the Neurotoxic and Healthy Cornea.

The aim of this study was to investigate the reliability of subbasal corneal nerve plexus parameters of the inferior whorl compared with the central cornea with in vivo corneal confocal microscopy and to investigate the impact of inferior whorl pattern complexity on reproducibility. Subbasal corneal nerves of healthy controls (n = 10) and patients with chemotherapy-induced peripheral neuropathy (n = 10) were imaged with a laser scanning confocal microscope. Two masked, experienced observers and the original image taker were tasked with selecting representative images of the central cornea and inferior whorl for each participant. This was conducted on 2 occasions 1 week apart. Corneal nerve fiber length (CNFL) and fractal dimension (CNFrD) [central cornea: CNFL and CNFrD; inferior whorl region: inferior whorl length (IWL) and inferior whorl fractal dimension (IWFrD)] were analyzed. Intraclass correlation coefficient (ICC) was analyzed for interobserver and intraobserver reliability. Inferior whorl complexity was classified according to the ease of identification of the center point of convergence. Interobserver ICC was 0.992 for CNFL, 0.994 for CNFrD, 0.980 for IWL, and 0.954 for IWFrD. When analyzed by inferior whorl complexity, the interobserver reliability was similar for simple (0.987 for IWL; 0.960 for IWFrD) and complex patterns (0.967 for IWL; 0.949 for IWFrD). However, intraobserver ICC were reduced for complex (IWL 0.841-0.970; IWFrD 0.830-0.955) compared with simple patterns (IWL 0.931-0.970; IWFrD 0.921-0.969). Although the overall interobserver reliability was excellent for the central corneal and inferior whorl parameters, there was lower intraobserver reliability for the inferior whorl parameters for complex morphological patterns. To improve reliability, more sophisticated wide-field imaging of the inferior whorl may be needed.

Multimodal testing reveals subclinical neurovascular dysfunction in prediabetes, challenging the diagnostic threshold of diabetes.

To explore if novel non-invasive diagnostic technologies identify early small nerve fibre and retinal neurovascular pathology in prediabetes. Participants with normoglycaemia, prediabetes or type 2 diabetes underwent an exploratory cross-sectional analysis with optical coherence tomography angiography (OCT-A), handheld electroretinography (ERG), corneal confocal microscopy (CCM) and evaluation of electrochemical skin conductance (ESC). Seventy-five participants with normoglycaemia (n=20), prediabetes (n=29) and type 2 diabetes (n=26) were studied. Compared with normoglycaemia, mean peak ERG amplitudes of retinal responses at low (16-Td·s: 4.05 μV, 95% confidence interval [95% CI] 0.96-7.13) and high (32-Td·s: 5·20 μV, 95% CI 1.54-8.86) retinal illuminance were lower in prediabetes, as were OCT-A parafoveal vessel densities in superficial (0.051 pixels/mm2 , 95% CI 0.005-0.095) and deep (0.048 pixels/mm2 , 95% CI 0.003-0.093) retinal layers. There were no differences in CCM or ESC measurements between these two groups. Correlations between HbA1c and peak ERG amplitude at 32-Td·s (r=-0.256, p=0.028), implicit time at 32-Td·s (r=0.422, p < 0.001) and 16-Td·s (r=0.327, p=0.005), OCT parafoveal vessel density in the superficial (r=-0.238, p=0.049) and deep (r=-0.3, p=0.017) retinal layers, corneal nerve fibre length (CNFL) (r=-0.293, p=0.017), and ESC-hands (r=-0.244, p=0.035) were observed. HOMA-IR was a predictor of CNFD (β=-0.94, 95% CI -1.66 to -0.21, p=0.012) and CNBD (β=-5.02, 95% CI -10.01 to -0.05, p=0.048). The glucose threshold for the diagnosis of diabetes is based on emergent retinopathy on fundus examination. We show that both abnormal retinal neurovascular structure (OCT-A) and function (ERG) may precede retinopathy in prediabetes, which require confirmation in larger, adequately powered studies.

Can Bioactive Compounds in Beetroot/Carrot Juice Have a Neuroprotective Effect? Morphological Studies of Neurons Immunoreactive to Calretinin of the Rat Hippocampus after Exposure to Cadmium.

Cadmium ions (Cd2+) penetrate the blood–brain barrier and can, among other effects, influence intracellular calcium metabolism, leading to neurodegeneration. In the presented work, we estimated the effect of Cd2+ on the expression of calretinin in the neurons of the rat hippocampus and analyzed the reverse effect of freshly pressed beetroot/carrot juice in this context. In the 12-week lasting experiment, 32 8-week-old male Wistar rats were divided into four experimental groups (n = 8): the control group (C) received pure tap water; the Cd group (Cd)—received Cd2+ dissolved in tap water (5 mg Cd2+/kg b.w.); and two groups received beetroot/carrot juice: the BCJ group was administered only juice, and the Cd + BCJ group received juice with the addition of Cd2+ (5 mg Cd2+/kg b.w.). The exposition to low doses of Cd2+ caused a significant decrease in calretinin-immunoreactive (Cr-IR) neurons compared to the non-exposed groups. Moreover, the addition of Cd2+ to tap water reduced the numbers and length of Cr-IR nerve fibers. The negative effect of Cd2+ was significantly attenuated by the simultaneous supplementation of beetroot/carrot juice (Cd + BCJ). The study showed that the bioactive compounds in the beetroot/carrot juice can modulate Ca2+ levels in neurons, and thus, potentially act as a neuroprotective factor against neuronal damage.