Corneal Nerve Fiber Length Research Articles

Small fibre pathology, small fibre symptoms and pain in fibromyalgia syndrome

A proportion of people with fibromyalgia demonstrate small fibre pathology (SFP). However, it is unclear how SFP directly relates to pain phenomenology. Thirty-three individuals with FMS and ten healthy volunteers underwent assessment of SFP and sensory phenotyping using corneal confocal microscopy, validated questionnaires and quantitative sensory testing (QST). Corneal nerve fibre length was used to stratify participants with fibromyalgia into with SFP [SFP+] and without SFP [SFP−]. SFP was detected in 50% of the fibromyalgia cohort. Current pain score and QST parameters did not differ between SFP+ and SFP−. Mechanical pain sensitivity (MPS) demonstrated a significant gain-of-function in the SFP− cohort compared to healthy-volunteers (p = 0.014, F = 4.806, η2 = 0.22). Further stratification revealed a cohort without structural SFP but with symptoms compatible with small fibre neuropathy symptoms and a significant gain in function in MPS (p = 0.020 Chi-square). Additionally, this cohort reported higher scores for both depression (p = 0.039, H = 8.483, η2 = 0.312) and anxiety (p = 0.022, F = 3.587, η2 = 0.293). This study confirms that SFP is present in a proportion of people with fibromyalgia. We also show that in a proportion of people with fibromyalgia, small fibre neuropathy symptoms are present in the absence of structural SFP. Greater mechanical pain sensitivity, depression and anxiety are seen in these individuals.

The sub‐basal nerve plexus and central corneal stromal microstructure in subjects with congenital aniridia, using in vivo confocal microscopy

Purpose: Congenital aniridia is a rare disease, with a global prevalence of 1 in 40 000 to 1 in 100 000. During life up to 70% of aniridia sufferers develop aniridia‐associated keratopathy (AAK) with limbal stem cell insufficiency, impaired corneal epithelial cell differentiation, abnormal cell adhesion and wound healing. AAK is characterized by centripetal spreading vascularization, conjunctivalization, and thickening of the cornea. We examined the sub‐basal nerve plexus and central corneal stromal microstructure in subjects with congenital aniridia, using in vivo confocal laser scanning microscopy (IVCM).Methods: 31 eyes of 18 patients (55.6% males, mean age: 25.22 ± 16.35 years) with congenital aniridia and 47 eyes of 29 healthy subjects (41.4% males, mean age 30 ± 14.82 years) were examined using the Rostock Cornea Module of Heidelberg Retina Tomograph‐III. At the sub‐basal nerve plexus, corneal nerve fibre density (CNFD), corneal nerve fibre length (CNFL), corneal total branch density (CTBD) and corneal nerve fibre width (CNFW) were analysed using ACCMetrics software. Keratocyte density in the anterior, middle and posterior stroma was assessed manually.Results: The CNFD (2.02 ± 4.08 vs. 13.99 ± 6.34/mm2), CNFL (5.78 ± 2.68 vs. 10.56 ± 2.82 mm/mm2) and CTBD (15.08 ± 15.62 vs. 27.44 ± 15.05/mm2) were significantly lower in congenital aniridia subjects, than in controls (p < 0.001 for all). CNFW was significantly higher in aniridia subjects, than in controls (0.03 ± 0.004 vs. 0.02 ± 0.003 mm/mm2) (p < 0.003). Keratocyte density was significantly lower in all stromal layers of congenital aniridia subjects, than in controls (p < 0.001 for all). Stromal alterations included confluent keratocytes, keratocytes with long extensions and hyperreflective dots between keratocytes in congenital aniridia.Conclusions: CNFD, CNFL and CTBD decrease and CNFW increase well refer to the congenital aniridia associated neuropathy. The decreased keratocyte density contradicts the inflammatory hypothesis of congenital aniridia. Corneal stromal changes in different stages of AAK have to be further analysed in detail0.

Contralateral eye comparison of the efficacy and safety of two artificial tear formulations for corneal subbasal nerve fiber regeneration after photorefractive keratectomy

Background: Currently, artificial tears (ATs) are the first-line agents for managing dry eye disease (DED). This study compared the efficacy and safety of two different AT formulations, Systane® Hydration (SH) and Systane® Ultra (SU), on symptoms of DED and regeneration of the subbasal corneal nerve fiber length (CNFL) in photorefractive keratectomy (PRK)-treated eyes.
 Methods: This prospective contralateral comparative study recruited myopic eyes scheduled for PRK, and either SH or SU were administered for up to 3 months postoperatively. All participants underwent a standard comprehensive preoperative ophthalmological examination, in vivo confocal microscopy to evaluate the subbasal CNFL, and completed Ocular Surface Disease Index (OSDI) questionnaire for assessing dry eye symptoms. Image analysis software was used to calculate the subbasal CNFL (micrometer/mm2). Assessments were repeated at the 1- and 3-month follow-up visits. Pre- and postoperative subbasal CNFL and OSDI scores were compared to determine inter- and intra-group differences.
 Results: Fifty eyes of 25 participants were included in this study. The mean (standard deviation) age of the participants was 22.7 (3.8) years. The OSDI scores for both groups increased significantly at 1 month (both P<0.05), followed by a decrease at 3 months to values comparable to the preoperative scores (both P>0.05). Although OSDI scores were comparable at baseline and at the 1-month postoperative visit (both P>0.05), the SU-treated eyes had a significantly better OSDI score at the 3-month visit (P<0.05), despite being clinically insignificant. Preoperative subbasal CNFL differed significantly between the groups (P=0.001), yet the mean values at both postoperative visits were comparable (both P>0.05). In both groups, subbasal CNFL was significantly reduced at 1 month, followed by a significant increase at the 3-month postoperative visit compared to baseline (all P<0.05). No treatment-related complications were observed at the end of the study period.
 Conclusions: No significant difference was found between the preoperative and 3-month postoperative OSDI scores in the SH- or SU-treated eyes. Subbasal CNFL regeneration indicated a positive effect of both ATs, with a longer mean CNFL noted in the SH-treated eyes at the final visit. This suggests that SH may be a better option for improving corneal reinnervation after PRK. These observations must be verified in further trials with longer follow-up periods and larger sample sizes.

Fully Automatic, Semiautomatic, and Manual Corneal Nerve Fiber Analysis in Patients With Sarcoidosis.

No guidelines are available on the preferred method for analyzing corneal confocal microscopy (CCM) data. Manual, semiautomatic, and automatic analyzes are all currently in use. The purpose of the present study was threefold. First, we aimed to investigate the different methods for CCM analysis in patients with and without small fiber neuropathy (SFN). Second, to determine the correlation of different methods for measuring corneal nerve fiber length (CNFL) and nerve fiber area (NFA). Finally, we investigated the added value of automatic NFA analysis. We included 20 healthy controls and 80 patients with sarcoidosis, 31 with established SFN and 49 without SFN. The CNFL was measured using CCMetrics, ACCMetrics, and NeuronJ. NFA was measured with NFA FIJI and ACCMetrics NFA. CNFL and NFA could not distinguish sarcoidosis with and without SFN or healthy controls. CCMetrics, NeuronJ, and ACCMetrics CNFL highly correlated. Also, NFA FIJI and ACCMetrics NFA highly correlated. Reproducing a nonlinear formula between CNFL and NFA confirmed the quadratic relation between NFA FIJI and ACCMetrics CNFL. CCMetrics and NeuronJ instead showed a square root relationship and seem to be less comparable owing to differences between automatic and manual techniques. ACCMetrics can be used for fully automatic analysis of CCM images to optimize efficiency. However, CNFL and NFA do not seem to have a discriminatory value for SFN in sarcoidosis. Further research is needed to determine the added value and normative values of NFA in CCM analysis. Our study improves the knowledge about CCM software and pathophysiology of SFN.

Identification of corneal and intra-epidermal axonal swellings in amyotrophic lateral sclerosis.

In patients with amyotrophic lateral sclerosis (ALS), axonal spheroids in motor axons have been identified in post-mortem studies. In this study, axonal spheroids and swellings on C-fibers of ALS patients were investigated using corneal confocal microscopy (CCM) and skin biopsy, respectively. Thirty-one ALS patients and 20 healthy subjects were evaluated with CCM to assess corneal nerve-fiber length (CNFL), -fiber density (CNFD), -branch density (CNBD), dendritic cell (DC) density, and axonal spheroids originating from C-fibers (>100 μm2 ). In addition, intraepidermal nerve fiber density (IENFD) and axonal swellings (>1.5 μm) were assessed in skin biopsies obtained from the arms and legs of 22 patients and 17 controls. In ALS patients, IENFD, CNFD, CNFL, and CNBD were not different from controls. The density of DCs and the number of patients with increased DC density were higher in ALS patients than controls (p = .0005 and p = .008). The number of patients with axonal spheroids was higher than controls (p = .03). Evaluation of DCs and axonal bulbs in C-fibers of ALS patients could provide insights into pathophysiology or potentially serve as biomarkers in ALS.

Corneal characteristics of Mongolian population with type 2 diabetic peripheral neuropathy in inner Mongolia, China: an assessment using corneal confocal microscopy

ObjectiveTo quantify corneal nerve fiber parameters in a Mongolian population with diabetic peripheral neuropathy (DPN) by corneal confocal microscopy.MethodsThis study conducted a comprehensive evaluation of 114 participants from Hulunbuir between January 2020 and December 2021. The participants included healthy controls, Mongolian and Han patients with type 2 diabetes mellitus. Demographic, medical, and laboratory data were collected, and neuropathy was evaluated by confocal corneal microscopy. And compare various parameters between Han and Mongolian were performed using SPSS software.ResultsThe average waist circumference of Mongolian diabetic patients was larger than that of Han diabetic patients (P < 0.05). The mean HbA1c of Mongolian was 9.30 (8.15, 10.30) %, and that of Han was 8.30 (7.20, 9.40) % (P = 0.023). The average values of Corneal Nerve Fiber Density (CNFD), Corneal Nerve Fiber Length (CNFL) and corneal nerve branch density (CNBD) in Mongolian diabetic patients were significantly lower than those in Han diabetic patients (P < 0.05). The correlation coefficient between CNFL and age was − 0.368. ROC results show that CNBD has a certain diagnostic value for DPN in Mongolian patients with type 2 diabetes and the optimal cut-off point value is 24.99(no./mm2), the sensitivity is 80.0%, and the specificity is 77.8%.ConclusionThe corneal confocal microscopy could possibly represent a promising adjuvant technique for the early diagnosis and assessment of PDN in Mongolian T2DM patients.

Corneal confocal microscopy demonstrates varying degrees of neurodegeneration in atypical parkinsonian disorders

ObjectiveWe have used corneal confocal microscopy (CCM) to identify corneal nerve loss as a potential marker of neurodegeneration in participants with Parkinson's disease (PD), multiple system atrophy (MSA) and progressive supranuclear palsy (PSP). MethodsPatients with PD (n = 19), PSP (n = 11), MSA (n = 8) and healthy controls (n = 18) underwent neurological assessment and CCM. ResultsCorneal nerve fibre density was significantly lower in participants with PD (p = 0.005), PSP (p = 0.005) and MSA (p = 0.0003) compared to controls. Corneal nerve branch density was significantly lower in participants with PD (p = 0.01) and MSA (p = 0.019), but not in participants with PSP (p = 0.662), compared to controls. Corneal nerve fibre length was significantly lower in participants with PD (p = 0.002) and MSA (p = 0.001) but not in participants with PSP (p = 0.191) compared to controls. ConclusionCCM detects corneal nerve loss in participants with PD and MSA and to a lesser extent in PSP compared to healthy controls.

Impact of Latent Virus Infection in the Cornea on Corneal Healing after Small Incision Lenticule Extraction.

The aim of the present study is to analyze the impact of cornea virus latent infection on corneal healing after small incision lenticule extraction (SMILE) and predict the positive rate of virus latent infection in corneal stroma. A total of 279 patients who underwent SMILE were included in this study. Fluorescence quantitative PCR was used to detect virus infection in the lenticules, which were taken from the corneal stroma during SMILE. Herpes simplex virus type 1 (HSV-1), herpes simplex virus type 2 (HSV-2), Epstein-Barr virus (EBV), and cytomegalovirus (CMV) were detected. Postoperative visual acuity, spherical equivalent, intraocular pressure, corneal curvature (Kf and Ks), corneal transparency, and corneal staining were compared between the virus-positive group and the virus-negative group. The number of corneal stromal cells and inflammatory cells, corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), corneal nerve fiber length (CNFL), corneal total branch density (CTBD), and corneal nerve fiber width (CNFW) were evaluated using an in vivo confocal microscope. Out of 240 herpes simplex virus (HSV) tested samples, 11 (4.58%) were positive, among which 5 (2.08%) were HSV-1-positive and 6 (2.50%) were HSV-2-positive. None of the 91 CMV- and EBV-tested samples were positive. There was no statistical significance in the postoperative visual acuity, spherical equivalent, intraocular pressure, Kf and Ks, corneal transparency, corneal staining, the number of corneal stromal cells and inflammatory cells, CNFD, CNBD, CNFL, CTBD, and CNFW between the virus-positive and virus-negative groups (p > 0.05). In conclusion, there is a certain proportion of latent HSV infection in the myopia population. Femtosecond lasers are less likely to activate a latent infection of HSV in the cornea. The latent infection of HSV has no significant impact on corneal healing after SMILE.

Relationship between ocular surface pain and corneal nerve loss in dry eye diabetics: a cross-sectional study in Shenyang, China

BackgroundDiabetes mellitus has been associated with increased dry eye disease (DED) and exacerbates DED pathology.ObjectiveTo investigate the potential relationship between corneal nerve loss and ocular pain among diabetic patients with...

Impact of Age on the Characteristics of Corneal Nerves and Corneal Epithelial Cells in Healthy Adults.

The aim of this study was to investigate age-related changes in corneal nerves and corneal epithelial cell parameters and to establish age-adjusted reference values. A total of 7025 corneal nerve images and 4215 corneal epithelial images obtained using in vivo confocal microscopy from 281 eyes of 143 healthy participants were included. Seven corneal nerve parameters and 3 corneal epithelial cell parameters were quantified using 2 automatic analytic software and analyzed across 6 age groups ranging from 21 to 80 years. There was a declining trend in all 7 nerve parameters with advancing age. In particular, corneal nerve fiber length and corneal nerve fiber density demonstrated a significant decrease in subjects aged 65 years or older compared with subjects younger than 65 years (10.8 ± 2.6 mm/mm 2 vs. 9.9 ± 2.0 mm/mm 2 , P = 0.011 in corneal nerve fiber length; 15.8 ± 5.2 fibers/mm 2 vs. 14.4 ± 4.3 fibers/mm 2 , P = 0.046 in corneal nerve fiber density), whereas corneal nerve fractal dimension demonstrated a borderline significant decrease ( P = 0.057). Similarly, there was a general declining trend in all epithelial cell parameters with advancing age. Corneal epithelial cell circularity was significantly lower in subjects aged 65 years and older as compared to subjects younger than 65 years (0.722 ± 0.021 μm 2 vs. 0.714 ± 0.021 μm 2 ; P = 0.011). Advancing age results in reduced corneal nerve metrics and alteration of corneal cell morphology. Aging effects should be considered when evaluating patients with corneal neuropathy.

Corneal Confocal Microscopy Predicts Cardiovascular and Cerebrovascular Events and Demonstrates Greater Peripheral Neuropathy in Patients with Type 1 Diabetes and Foot Ulcers.

In this study, we evaluate small and large nerve fibre pathology in relation to diabetic foot ulceration (DFU) and incident cardiovascular and cerebrovascular events in type 1 diabetes (T1D). A prospective observational study was conducted on people with T1D without diabetic peripheral neuropathy (DPN) (n = 25), T1D with DPN (n = 28), T1D with DFU (n = 25) and 32 healthy volunteers. ROC analysis of parameters was conducted to diagnose DPN and DFU, and multivariate Cox regression analysis was performed to evaluate the predictive ability of corneal nerves for cardiac and cerebrovascular events over 3 years. Corneal nerve fibre length (CNFL), fibre density (CNFD) and branch density (CNBD) were lower in T1D-DPN and T1D-DFU vs. T1D (all p < 0.001). In ROC analysis, CNFD (sensitivity 88%, specificity 87%; AUC 0.93; p < 0.001; optimal cut-off 7.35 no/mm2) and CNFL (sensitivity 76%, specificity 77%; AUC 0.90; p < 0.001; optimal cut-off 7.01 mm/mm2) had good ability to differentiate T1D with and without DFU. Incident cardiovascular events (p < 0.001) and cerebrovascular events (p < 0.001) were significantly higher in T1D-DPN and T1D-DFU. Corneal nerve loss, specifically CNFD predicted incident cardiovascular (HR 1.67, 95% CI 1.12 to 2.50, p = 0.01) and cerebrovascular (HR 1.55, 95% CI 1.06 to 2.26, p = 0.02) events. Our study provides threshold values for corneal nerve fibre metrics for neuropathic foot at risk of DFU and further demonstrates that lower CNFD predicts incident cardiovascular and cerebrovascular events in T1D.

Chronic Kidney Disease Has No Impact on Tear Film Substance P Concentration in Type 2 Diabetes.

The study aimed to ascertain the potential effects of chronic kidney disease (CKD) on substance P concentration in the tear film of people with type 2 diabetes. Participants were classified into two groups: type 2 diabetes with concurrent chronic kidney disease (T2DM-CKD (n = 25)) and type 2 diabetes without chronic kidney disease (T2DM-no CKD (n = 25)). Ocular surface discomfort assessment, flush tear collection, in-vivo corneal confocal microscopy, and peripheral neuropathy assessment were conducted. Enzyme-linked immunosorbent assays were utilized to ascertain the levels of tear film substance P in collected flush tears. Correlation analysis, hierarchical multiple linear regression analysis, and t-tests or Mann-Whitney U tests were used in the analysis of data for two-group comparisons. There was no substantial difference between the T2DM-CKD and T2DM-no CKD groups for tear film substance P concentration (4.4 (0.2-50.4) and 5.9 (0.2-47.2) ng/mL, respectively; p = 0.54). No difference was observed in tear film substance P concentration between the low-severity peripheral neuropathy and high-severity peripheral neuropathy groups (4.4 (0.2-50.4) and 3.3 (0.3-40.7) ng/mL, respectively; p = 0.80). Corneal nerve fiber length (9.8 ± 4.6 and 12.4 ± 3.8 mm/mm2, respectively; p = 0.04) and corneal nerve fiber density (14.7 ± 8.5 and 21.1 ± 7.0 no/mm2, respectively; p < 0.01) were reduced significantly in the T2DM-CKD group compared to the T2DM-no CKD group. There were significant differences in corneal nerve fiber density (21.0 ± 8.1 and 15.8 ± 7.7 no/mm2, respectively; p = 0.04) and corneal nerve fiber length (12.9 ± 4.2 and 9.7 ± 3.8 mm/mm2, respectively; p = 0.03) between the low- and high-severity peripheral neuropathy groups. In conclusion, no significant difference in tear film substance P concentration was observed between type 2 diabetes with and without CKD. Corneal nerve loss, however, was more significant in type 2 diabetes with chronic kidney disease compared to type 2 diabetes alone, indicating that corneal nerve morphological measures could serve greater utility as a tool to detect neuropathy and nephropathy-related corneal nerve changes.

Impact of corrected refractive power on the corneal denervation and ocular surface in small-incision lenticule extraction and LASIK.

To evaluate the impact of corrected refractive power on the corneal denervation and ocular surface in small-incision lenticule extraction (SMILE) and laser in situ keratomileusis (LASIK). Singapore National Eye Center, Singapore. Prospective study. 88 eyes undergoing SMILE or LASIK were divided into low-moderate (manifest refractive spherical equivalent [MRSE] <-6.0 diopters [D]) and high myopic (MRSE ≥-6.0 D) groups. In vivo confocal microscopy and clinical assessments were performed preoperatively and at 1 month, 3 months, 6 months, and 12 months postoperatively. In SMILE, high myopic treatment presented with significantly greater reduction in the corneal nerve fiber area (CNFA) and nerve fiber fractal dimension (CFracDim) compared with low-moderate myopic treatment (both P < .05). There was a significant and negative correlation between the corrected MRSE and the reduction in corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), corneal nerve fiber length, CNFA, and CFracDim after SMILE (r = -0.38 to -0.66, all P < .05). In LASIK, a significant correlation between the MRSE and the changes in CNBD, corneal nerve fiber total branch density, CNFA (r = -0.37 to -0.41), and corneal nerve fiber width (r = 0.43) was observed (all P < .05). Compared with SMILE, LASIK had greater reduction in CNBD and CNFA for every diopter increase in the corrected MRSE. High myopic SMILE, compared with low-moderate myopic SMILE, resulted in significantly lower tear break-up time at 1 and 6 months (both P < .05). The changes in CNFA and CFracDim were significantly associated with Schirmer test values (both P < .001). Postoperative corneal denervation was related to corrected refractive power in both SMILE and LASIK. With the same refractive correction, LASIK led to more prominent corneal denervation.

Corneal confocal microscopy demonstrates sensory nerve loss in children with autism spectrum disorder.

Autism spectrum disorder (ASD) is a developmental disorder characterized by difficulty in communication and interaction with others. Postmortem studies have shown cerebral neuronal loss and neuroimaging studies show neuronal loss in the amygdala, cerebellum and inter-hemispheric regions of the brain. Recent studies have shown altered tactile discrimination and allodynia on the face, mouth, hands and feet and intraepidermal nerve fiber loss in the legs of subjects with ASD. Fifteen children with ASD (age: 12.00 ± 3.55 years) and twenty age-matched healthy controls (age: 12.83 ± 1.91 years) underwent corneal confocal microscopy (CCM) and quantification of corneal nerve fiber morphology. Corneal nerve fibre density (fibers/mm2) (28.61 ± 5.74 vs. 40.42 ± 8.95, p = 0.000), corneal nerve fibre length (mm/mm2) (16.61 ± 3.26 vs. 21.44 ± 4.44, p = 0.001), corneal nerve branch density (branches/mm2) (43.68 ± 22.71 vs. 62.39 ± 21.58, p = 0.018) and corneal nerve fibre tortuosity (0.037 ± 0.023 vs. 0.074 ± 0.017, p = 0.000) were significantly lower and inferior whorl length (mm/mm2) (21.06 ± 6.12 vs. 23.43 ± 3.95, p = 0.255) was comparable in children with ASD compared to controls. CCM identifies central corneal nerve fiber loss in children with ASD. These findings, urge the need for larger longitudinal studies to determine the utility of CCM as an imaging biomarker for neuronal loss in different subtypes of ASD and in relation to disease progression.

Neural Regeneration in Dry Eye Secondary to Systemic Lupus Erythematosus Is Also Disrupted like in Rheumatoid Arthritis, but in a Progressive Fashion.

Our objective in this study was to analyze the aberrant neural regeneration activity in the cornea by means of in vivo confocal microscopy in systemic lupus erythematosus patients with concurrent dry eye disease. We examined 29 systemic lupus erythematosus patients and 29 age-matched healthy control subjects. Corneal nerve fiber density (CNFD, the number of fibers/mm2) and peripheral Langerhans cell morphology were lower (p < 0.05) in systemic lupus erythematosus patients compared to the control group. Interestingly, corneal nerve branch density, corneal nerve fiber length, corneal nerve fiber total branch density, and corneal nerve fiber area showed a negative correlation with disease duration. A negative correlation was also demonstrated between average corneal nerve fiber density and central Langerhans cell density. This is in line with our hypothesis that corneal somatosensory terminal Piezo2 channelopathy-induced impaired Piezo2-Piezo1 crosstalk not only disrupts regeneration and keeps transcription activated, but could lead to Piezo1 downregulation and cell activation on Langerhans cells when we consider a chronic path. Hence, Piezo2 containing mechanosensory corneal nerves and dendritic Langerhans cells could also be regarded as central players in shaping the ocular surface neuroimmune homeostasis through the Piezo system. Moreover, lost autoimmune neuroinflammation compensation, lost phagocytic self-eating capacity, and lost transcription regulation, not to mention autoantibodies against vascular heparin sulfate proteoglycans and phospholipids, could all contribute to the progressive fashion of dry eye disease in systemic lupus erythematosus.

106-OR: Degludec-Like Insulin Analog Improves Peripheral Neuropathy More than Control Insulin Independent of Glycemic Control in a Rat Model of Type 2 Diabetes

Current treatments for type 2 diabetes fail to prevent the development of peripheral neuropathy. To examine insulin degludec’s effect on peripheral neuropathy in rats, we tested insulin 700, an analog identical to insulin degludec with the same pharmacokinetic (PK) and pharmacodynamic (PD) characteristics, but with the absence of the terminal threonine on the B-chain. Rats were fed a high fat diet for 8 weeks and then treated with a low dose of streptozotocin to induce hyperglycemia. After 2 weeks, diabetic rats were treated with I700 or a control basal insulin (IC) with similar PK twice daily for 18 weeks. A healthy reference group fed a chow diet and not subjected to streptozotocin treatment was also included. The endpoints evaluated included sensory and motor nerve conduction velocity, allodynia using von Frey’s test, thermal sensitivity using Hargreaves test and corneal sensitivity. We evaluated innervation of sensory nerves using corneal confocal microscopy and, in the skin, using histological methods. We also tested vascular reactivity of epineurial arterioles using pressure myography. The insulin analogues were equally effective at correcting hyperglycemia as determined by HbA1C levels of 4.1±0.1 and 4.1±0.1% for I700 and IC, respectively. Both insulin analogues improved all neuropathy related parameters. However, I700 was more effective in that by the end of the treatment period there was no difference in thermal sensitivity, corneal sensitivity, corneal nerve fiber length and sensory and motor nerve conduction velocity between the group treated with I700 and the healthy reference rats. Interestingly, vascular relaxation to acetylcholine improved more with IC treatment. In conclusion, this study demonstrates that I700 (a degludec-like insulin analog) is a more effective treatment for diabetic peripheral neuropathy than a comparable control insulin, independent of glycemic control. Disclosure T.C.A.Åkerström: Employee; Novo Nordisk. L.Andreasen: Employee; Novo Nordisk. E.Nishimura: Employee; Novo Nordisk A/S. M.A.Yorek: Consultant; Novo Nordisk.

486-P: Reduced Serum Netrin-1 Levels Correlate with Corneal Nerve Fiber Loss in Diabetic Neuropathy

Objective: Deficiency of endogenous neurotropic factors are implicated in diabetic neuropathy (DN). While Netrin-1, a neurotropic factor, is downregulated in type 2 diabetes, its involvement in Diabetic Neuropathy (DN) is yet to be reported. While corneal confocal microscopy (CCM) is a sensitive, in-vivo, non-invasive technique for detection of DN at its earliest stages, the association between CCM parameters and serum Netrin-1 levels has not been reported before. The present study looked at serum netrin levels in populations with type 2 diabetes with or without neuropathy, using CCM as the gold standard. Methods: Sixty subjects with type 2 diabetes (DN- 30, DN+ 30)] were stratified using DN4Q and Vibration perception Threshold Test (VPT). Cornea was assessed using CCM. Serum Netrin-1 level was measured by ELISA. Data compared 27 healthy controls were also studied. Results: There was a significant reduction in corneal nerve fibre density (CNFD), branch density (CNBD), and fibre length (CNFL) in T2D. DN was associated with a greater reduction in all CCM parameters compared to those with type 2 diabetes but no DN (p&amp;lt;0.05). There was a progressive decline in the mean serum netrin-1 level from healthy controls to T2D DN- to T2D DN+ (Control vs T2D, p&amp;lt;0.05; T2D DN- vs DN+, p&amp;lt;0.01)]. Netrin-1 correlated only with CNBD in T2D DN- group, (p=0.02). While ROC analysis showed CNFD, CNBD and CNFL to predict DN in 55.6%, 57.1% and 62.1% respectively, Netrin-1 alone predicted DN in 63.3%. CNBD and CNFL correlated with Netrin-1 (p=0.04 and p=0.01) in T2D DN+ group. Conclusion: Serum netrin-1 levels declined progressively from controls to T2D to T2D with DN; netrin-1 levels correlated significantly with the CCM parameters. Serum Netrin-1 levels showed a significant positive correlation with CNBD in type 2 diabetes (DN- or DN+). A strong correlation was seen between CNFL and netrin-1 levels in more advanced diabetic neuropathy (abnormal VPT). The results of our pilot study need validation in larger populations. Disclosure A.Mondal: None. C.Bose: None. S.Pramanik: None. A.Mukherjee: None. B.Mukherjee: None. S.Mukhopadhyay: None. Funding Research Society for the Study of Diabetes in India

The diagnosis and treatment of contact lens-induced limbal stem cell deficiency

Objective: To analyze the clinical features and treatment outcomes of eyes with contact lens-induced limbal stem cell deficiency (CL-iLSCD). Methods: This cross-sectional study involved patients diagnosed with CL-iLSCD at the Eye, Ear, Nose & Throat Hospital of Fudan University between October 2018 and September 2022. A total of 17 patients (25 eyes) with a mean age of (36.4±6.9) years were enrolled. Among them, 14 were females (82.4%). Corneal and limbal abnormalities, especially the range of epitheliopathy, were observed under a slit lamp biomicroscope with fluorescein staining. Anterior segment optical coherence tomography and in vivo laser scanning confocal microscopy were performed to obtain the central corneal epithelial thickness, density of basal epithelial cells and corneal nerve fiber length. The clinical features of CL-iLSCD, along with their treatment outcomes and related risk factors, were analyzed. Results: All patients wore soft contact lenses, with an average daily wearing time of (10.5±2.5) hours and a median wearing duration of 10 (4 to 30) years. Ocular symptoms, including decreased vision, ocular discomfort or pain, redness, and photophobia, were present in 22 eyes (88.0%). The most characteristic clinical sign of CL-iLSCD was comb-or whorl-pattern late fluorescein staining under cobalt blue light, which was most commonly seen at the superior limbus (25/25, 100.0%). Additionally, reductions in central corneal epithelial thickness, basal cell density, and corneal nerve fiber length were observed. A comprehensive score was assigned to each eye based on clinical findings and in vivo imaging biomarkers. LSCD was mild, moderate, and severe in 5, 11, and 8 eyes, respectively. A history of misdiagnosis was found in 20 eyes (80.0%). After discontinuing the use of contact lenses and receiving medical treatment, significant improvement was observed in all eyes, with 13 eyes fully recovered. Conclusions: The symptoms and clinical signs of CL-iLSCD can be subtle at the early stage. Discontinuing contact lens wear and medication are effective to treat CL-iLSCD.

Occurrence of corneal sub-epithelial microneuromas and axonal swelling in people with diabetes with and without (painful) diabetic neuropathy

Aims/hypothesisNon-invasive in vivo corneal confocal microscopy is gaining ground as an alternative to skin punch biopsy to evaluate small-diameter nerve fibre characteristics. This study aimed to further explore corneal nerve fibre pathology in diabetic neuropathy.MethodsThis cross-sectional study quantified and compared corneal nerve morphology and microneuromas in participants without diabetes (n=27), participants with diabetes but without distal symmetrical polyneuropathy (DSPN; n=33), participants with non-painful DSPN (n=25) and participants with painful DSPN (n=18). Clinical and electrodiagnostic criteria were used to diagnose DSPN. ANCOVA was used to compare nerve fibre morphology in the central cornea and inferior whorl, and the number of corneal sub-epithelial microneuromas between groups. Fisher’s exact tests were used to compare the type and presence of corneal sub-epithelial microneuromas and axonal swelling between groups.ResultsVarious corneal nerve morphology metrics, such as corneal nerve fibre length and density, showed a progressive decline across the groups (p<0.001). In addition, axonal swelling was present more frequently (p=0.018) and in higher numbers (p=0.03) in participants with painful compared with non-painful DSPN. The frequency of axonal distension, a type of microneuroma, was increased in participants with painful and non-painful DSPN compared to participants with diabetes but without DSPN and participants without diabetes (all p≤0.042). The combined presence of all microneuromas and axonal swelling was increased in participants with painful DSPN compared with all other groups (p≤0.026).Conclusions/interpretationMicroneuromas and axonal swelling in the cornea increase in prevalence from participants with diabetes to participants with non-painful DSPN and participants with painful DSPN.Graphical

Corneal confocal microscopy reveals small nerve fibre loss correlating with motor function in adult spinal muscular atrophy.

5q Spinal muscular atrophy (SMA) is a progressive, inherited, and severely disabling - yet treatable - motor neuron disease. Although treatment options have evolved in recent years, biomarkers for treatment monitoring and prognosis prediction remain elusive. Here, we investigated the utility of corneal confocal microscopy (CCM), a non-invasive imaging technique to quantify small corneal nerve fibres in vivo, as a diagnostic tool in adult SMA. In this cross-sectional study, 19 patients with SMA type 3 and 19 healthy controls underwent CCM to measure corneal nerve fibre density (CNFD), corneal nerve fibre length (CNFL), and corneal nerve branch density (CNBD), as well as corneal immune cell infiltration. Hammersmith Functional Motor Scale Expanded (HFMSE) and Revised Upper Limb Module (RULM) scores and a 6-Minute Walk Test (6MWT) were conducted to explore any correlation between CCM findings and motor function. Corneal nerve fibre parameters were decreased in SMA patients versus healthy controls (CNFD: p = 0.030; CNFL: p = 0.013; CNBD: p = 0.020) in the absence of relevant immune cell infiltration. CNFD and CNFL correlated with HFMSE scores (CNFD: r = 0.492, p = 0.038; CNFL: r = 0.484, p = 0.042) and distance covered in the 6MWT (CNFD: r = 0.502, p = 0.042; CNFL: r = 0.553, p = 0.023). Corneal confocal microscopy CCM reveals sensory neurodegeneration in SMA, thereby supporting a multisystem view of the disorder. Subclinical small nerve fibre damage correlated with motor function. Thus, CCM may be ideally suited for treatment monitoring and prognosis.