Corneal Nerve Fiber Length Research Articles

Corneal confocal microscopic characteristics of acute angle-closure crisis

BackgroundTo investigate characteristics of the acute angle-closure crisis (AACC) and fellow eyes using confocal microscopy.MethodsUnilateral AACC patients hospitalized at the Xi’an People’s Hospital from October 2017 to October 2020 were recruited in this cross-sectional study. Age-matched participants scheduled for cataract surgery were enrolled as a healthy control group. Corneal epithelial cells, subepithelial nerve fiber plexus, stromal cells, and endothelial cells were examined by confocal and specular microscopy.ResultsThis study enrolled 41 unilateral AACC patients (82 eyes) and 20 healthy controls (40 eyes). Confocal microscopy revealed that the corneal nerve fiber density, corneal nerve branch density and corneal nerve fiber length were reduced significantly in AACC eyes. The stromal cells were swollen and the size of the endothelial cells was uneven with the deposition of punctate high-reflective keratic precipitate on the surface. In severe cases, the cell volume was enlarged, deformed, and fused. The corneal subepithelial nerve fiber, stromal layer, and endothelial layer were unremarkable in the fellow eyes, and the density of the endothelial cells was 2601 ± 529 cells/mm2, which was higher than 1654 ± 999 cells/mm2 in AACC eyes (P < 0.001). Corneal edema prevented the examination of 17 eyes using specular microscopy and in only four eyes using confocal microscopy. There were no significant differences in endothelial cell density between confocal and specular microscopy in the AACC eyes (P = 0.674) and fellow eyes (P = 0.247). The hexagonal cell ratio reduced significantly (P < 0.001), and average cell size and coefficient of variation of the endothelial cells increased significantly compared with fellow eyes (P < 0.001, P = 0.008).ConclusionsAACC eye showed decreased density and length of corneal subepithelial nerve fiber plexus, activation of stromal cells, increased endothelial cell polymorphism, and decreased density.

Small fiber neuropathy for assessment of disease severity in amyotrophic lateral sclerosis: corneal confocal microscopy findings

BackgroundAmyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder with progressive motor system impairment, and recent evidence has identified the extra-motor involvement. Small fiber neuropathy reflecting by sensory and autonomic disturbances in ALS has been reported to accompany the motor damage. However, non-invasive assessment of this impairment and its application in disease evaluation of ALS is scarce. We aim to evaluate the use of corneal confocal microscopy (CCM) to non-invasively quantify the corneal small fiber neuropathy in ALS and explore its clinical value in assessing disease severity of ALS.MethodsSixty-six patients with ALS and 64 healthy controls were included in this cross-sectional study. Participants underwent detailed clinical assessments and corneal imaging with in vivo CCM. Using ImageJ, the following parameters were quantified: corneal nerve length (IWL) and dendritic cell density (IWDC) in the inferior whorl region and corneal nerve fiber length (CNFL), nerve fiber density (CNFD), nerve branch density (CNBD), and dendritic cell density (CDC) in the peripheral region. Disease severity was evaluated using recognized scales.ResultsCorneal nerve lengths (IWL and CNFL) were lower while dendritic cell densities (IWDC and CDC) were higher in patients with ALS than controls in peripheral and inferior whorl regions (p < 0.05). Additionally, corneal nerve complexity in the peripheral region was greater in patients than controls with higher CNBD (p = 0.040) and lower CNFD (p = 0.011). IWL was significantly associated with disease severity (p < 0.001) and progression (p = 0.002) in patients with ALS. Patients with bulbar involvement showed significantly lower IWL (p = 0.014) and higher IWDC (p = 0.043) than patients without bulbar involvement.ConclusionsCCM quantified significant corneal neuropathy in ALS, and alterations in the inferior whorl region were closely associated with disease severity. CCM could serve as a noninvasive, objective imaging tool to detect corneal small fiber neuropathy for clinical evaluation in ALS.

Corneal confocal microscopy detects small-fiber neuropathy in patients with amyotrophic lateral sclerosis

Objective: To investigate small fiber neuropathy in patients with amyotrophic lateral sclerosis (ALS) by corneal confocal microscopy. Methods: A total of 57 ALS patients were consecutively enrolled in Department of Neurology between June 2015 and February 2016, including 37 men and 20 women with mean age 24-80 (52±11) years. There were 30 controls including 21 men and 9 women with mean age 23-76 (55±13) years. All subjects underwent corneal confocal microscopy (CCM), contact heat evoked potential (CHEP) and skin sympathetic reflection (SSR) to quantify small nerve fiber pathology. Four parameters, such as nerve fiber length (NFL), nerve branch density (NBD), nerve fiber density (NFD) and nerve fiber tortuosity (NFT) were assessed by corneal confocal microscopy. All statistical calculations were conducted using SPSS version 12.0. Results: Compared with control group, corneal nerve fiber length (NFL),nerve fiber density (NFD) were significantly decreased [(12.2±4.4)mm/mm2 vs.(15.1±4.5) mm/mm2,P=0.028;(50.8±24.0)/mm2 vs. (68.3±16.4)/mm2,P=0.002],and nerve fiber tortuosity (NFT) were significantly increased [(2.6±1.0)level vs.(1.0±0.5)level, P<0.01)] in SFN group, while nerve branch density (NBD) were comparable (P=0.700).The course of disease is correlated with NFT (r=0.25,P=0.030). Conclusions: CCM is a new sensitive noninvasive clinical technique that detects early small fiber nerve damage in patients with ALS.

Cell Morphology as an In Vivo Parameter for the Diagnosis of Limbal Stem Cell Deficiency.

The aim of this study was to investigate basal epithelial cell morphology (CM) in the central cornea and limbal areas of eyes with limbal stem cell deficiency (LSCD). This was a prospective, cross-sectional comparative study. We developed a CM scoring system based on basal epithelial cell phenotypes graded from 0 (normal) to 3 (severe morphologic alterations); this system was evaluated by 2 independent masked observers. The CM score was compared with the LSCD clinical score, mean best-corrected visual acuity, and in vivo laser scanning confocal microscopy parameters used to stage LSCD (ie, basal epithelial cell density, basal epithelial thickness, and subbasal corneal nerve fiber length density). One hundred sixty-eight eyes with LSCD and 63 normal eyes were included. Compared with the control group, the LSCD group had significantly higher mean (±SD) CM scores in the central cornea (1.8 ± 0.7 vs. 0.5 ± 0.4, respectively; P = 0.01) and limbal areas (1.6 ± 0.2 vs. 1.3 ± 0.0, respectively; P < 0.05). The mean CM score in the central cornea was positively correlated with the clinical score ( P < 0.01, r = 0.66) and negatively correlated with the best-corrected visual acuity ( P < 0.01, r = 0.42). The CM scores were positively correlated with all other in vivo laser scanning confocal microscopy parameters in the central cornea and limbal areas (all P < 0.001). Basal epithelial CM is altered in the central cornea and limbus of eyes with LSCD and thus can be used to stage the clinical severity of the disease.

Biomarkers of in vivo limbal stem cell function

PurposeTo evaluate in vivo parameters as biomarkers of limbal stem cell function and to establish an objective system that detects and stage limbal stem cell deficiency (LSCD). MethodsA total of 126 patients (172 eyes) with LSCD and 67 normal subjects (99 eyes) were included in this observational cross-sectional comparative study. Slit-lamp biomicroscopy, in vivo laser scanning confocal microscopy (IVCM), and anterior segment optical coherence tomography (AS-OCT) were performed to obtain the following: clinical score, cell morphology score, basal cell density (BCD), central corneal epithelial thickness (CET), limbal epithelial thickness (LET), total corneal nerve fiber length (CNFL), corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), and tortuosity coefficient. Their potential correlations with the severity of LSCD were investigated, and cutoff values were determined. ResultsAn increase clinical score correlated with a decrease in central cornea BCD, limbal BCD, CET, mean LET, maximum LET, CNFL, CNFD, CNBD, and tortuosity coefficient. Regression analyses showed that central cornea BCD, CET and CNFL were the best parameters to differentiate LSCD from normal eyes (Coef = 3.123, 3.379, and 2.223; all p < 0.05). The rank correlation analysis showed a similar outcome between the clinical scores and the central cornea BCD (ρ = 0.79), CET (ρ = 0.82), and CNFL (ρ = 0.71). A comprehensive LSCD grading formula based on a combination of these parameters was established. ConclusionsA comprehensive staging system combining clinical presentation, central cornea BCD, CET, and CNFL is established to accurately and objectively diagnose LSCD and stage its severity.

Corneal nerve fiber measures independently predict progression from MCI to dementia: Follow‐up of the Qatar Longitudinal Study Cohort

AbstractBackgroundThere is an urgent need for biomarkers of neurodegeneration to identify individuals with MCI at higher risk for developing dementia. Corneal confocal microscopy (CCM) is a non‐invasive imaging biomarker which has identified corneal nerve loss in individuals with mild cognitive impairment (MCI) and dementia. This study assessed the predictive capability of CCM and MRI brain volumetry for progression from participants with MCI to dementia.MethodIn this prospective study, participants aged 50‐85 with MCI underwent assessment of clinical dementia rating (CDR), Montreal cognitive assessment (MoCA), MRI brain volumetry and CCM at baseline and CDR and MoCA at 1‐4 year follow‐up.ResultThe study cohort comprised 107 participants with MCI aged 68.4±7.7 years. Over a median follow‐up of 2.4 years, 33 of 107 participants (30.8%) with MCI progressed to dementia. Corneal nerve fibre density (P&lt;0.0001), branch density (P&lt;0.0001) and length (P&lt;0.0001) were significantly lower in MCI participants who progressed to dementia. Reduced baseline corneal nerve fiber density (≤25 fiber/mm2), length (≤15 mm/mm2) and branch density (≤44 branches/mm2) accurately predicted future dementia (area under the curve (AUC) = 71‐74%, P≤0.0001). Reduced baseline intra‐cranial volume percentage (ICV %), hippocampus (≤0.44%), whole brain (≤69.4%), frontal lobe (≤10.8%), amygdala (≤0.17%), cortical gray matter (≤29%), thalamus (≤0.90%) and increased ventricle (≥3.0%) volume predicted future dementia (AUC = 65‐78%, P&lt;0.05), whilst temporal, parietal, occipital lobe, entorhinal cortex, cingulate gyrus and brainstem did not. The adjusted odds ratios (AOR) for progression to dementia were 5.1‐11.1 times higher with abnormal corneal nerve fiber measures (P&lt;0.05), 5.9 higher with abnormal hippocampal volume (P&lt;0.05) and 10.8 times higher with whole‐brain volume (P&lt;0.05).ConclusionThe predictive capability of CCM is comparable to hippocampal and whole brain volume for progression to dementia in individuals with MCI.

Characteristics of ocular findings of patients with neuronal intranuclear inclusion disease.

This study aimed to explore the ocular characteristics of neuronal intranuclear inclusion disease (NIID), caused by GGC repeat expansion in the NOTCH2NLC gene, combined with the systemic clinical manifestations, and propose early diagnostic features of NIID. Six patients (12 eyes) were enrolled in this study. In vivo corneal confocal microscopy (IVCCM), fundus photography, fundus autofluorescence (FAF) imaging, optical coherence tomography (OCT), full-field electroretinography (ERG), and electromyography were performed. The average corneal nerve fiber density (CNFD) was 6.83 ± 4.96 number/mm2, and the corneal nerve fiber length (CNFL) was 6.76 ± 1.96mm/mm2. The nerves were looser and more curved in affected individuals. Dendritic cells were observed in patients with NIID. Chorioretinal atrophy, hyper-AF spots, and outer retinal abnormalities were observed during FAF imaging and OCT examinations. In full-field ERGs, the amplitudes of the a-wave and b-wave reduced or extinguished over time. The compound muscle action potential and motor nerve conduction velocity of the left common peroneal nerve decreased substantially. The findings of IVCCM and retinal changes should be included in the diagnostic criteria for NIID. Corneal confocal characteristics may precede the systemic neurological manifestations and provide a clinical basis for the early treatment and staging of the disease. ClincalTrials.gov. Identifier: ChiCTR21000500227.

Corneal confocal microscopy demonstrates axonal loss in different courses of multiple sclerosis

Axonal loss is the main determinant of disease progression in multiple sclerosis (MS). This study aimed to assess the utility of corneal confocal microscopy (CCM) in detecting corneal axonal loss in different courses of MS. The results were confirmed by two independent segmentation methods. 72 subjects (144 eyes) [(clinically isolated syndrome (n = 9); relapsing–remitting MS (n = 20); secondary-progressive MS (n = 22); and age-matched, healthy controls (n = 21)] underwent CCM and assessment of their disability status. Two independent algorithms (ACCMetrics; and Voxeleron deepNerve) were used to quantify corneal nerve fiber density (CNFD) (ACCMetrics only), corneal nerve fiber length (CNFL) and corneal nerve fractal dimension (CNFrD). Data are expressed as mean ± standard deviation with 95% confidence interval (CI). Compared to controls, patients with MS had significantly lower CNFD (34.76 ± 5.57 vs. 19.85 ± 6.75 fibers/mm2, 95% CI − 18.24 to − 11.59, P < .0001), CNFL [for ACCMetrics: 19.75 ± 2.39 vs. 12.40 ± 3.30 mm/mm2, 95% CI − 8.94 to − 5.77, P < .0001; for deepNerve: 21.98 ± 2.76 vs. 14.40 ± 4.17 mm/mm2, 95% CI − 9.55 to − 5.6, P < .0001] and CNFrD [for ACCMetrics: 1.52 ± 0.02 vs. 1.45 ± 0.04, 95% CI − 0.09 to − 0.05, P < .0001; for deepNerve: 1.29 ± 0.03 vs. 1.19 ± 0.07, 95% − 0.13 to − 0.07, P < .0001]. Corneal nerve parameters were comparably reduced in different courses of MS. There was excellent reproducibility between the algorithms. Significant corneal axonal loss is detected in different courses of MS including patients with clinically isolated syndrome.

Reduced Corneal Sensitivity With Neuronal Degeneration is a Novel Clinical Feature in Wolfram Syndrome

To evaluate corneal sensitivity and corneal nerve morphology among patients with Wolfram syndrome (WFS). An observational clinical case series with confirmatory experiments. We included a group of 12 patients with biallelic mutations in the WFS1 gene and a control group composed of 30 individuals with type 1 diabetes (T1D). All participants (n=42) underwent a complete ophthalmic examination, esthesiometry, and retinal nerve fiber layer assessment using optical coherence tomography. Morphologic assessment of corneal neuropathy by in vivo corneal confocal microscopy was conducted in 11 patients with WFS (both eyes) and 1 WFS patient (1 eye) as well as in 24 patients with T1D (both eyes in 6 patients and 1 eye in 18 patients). Additionally, corneas from Wfs1KO mice and their wild-type littermates were subjected to laser scanning confocal microscopy. Corneal sensitivity was significantly reduced in patients with WFS compared with patients with T1D (4.50 cm [interquartile range, 3.50-5.50 cm] vs 6.00 cm [interquartile range, 6.00-6.00 cm]; P < 10-5). Additionally, corneal nerve fiber and branch density as well as nerve fiber length were low among patients with WFS. Corneal sensitivity correlated with macular average thickness (R=0.6928; P=.039) and best-corrected visual acuity (R=-0.61; P=.002) in the WFS group. Similarly, Wfs1 knockout mice also presented corneal neurodegeneration changes when corneal nerve fiber density and length were measured using laser scanning confocal microscopy. Decreased corneal sensitivity and corneal nerve degeneration are observed in WFS. Corneal sensitivity is linked with the degree of disease progression as measured by visual acuity and retinal thinning.

Corneal Sensation and Nerve Fiber Changes in Patients With Interstitial Cystitis.

Central sensitization syndromes are associated with ocular surface discomfort and certain changes in corneal sensation. The aim of this study was to evaluate corneal changes in patients with interstitial cystitis (IC). Thirty patients with IC and 32 healthy control subjects were included in this study. All patients had a detailed ophthalmological examination including measurement of corneal sensation with Cochet-Bonnet esthesiometer, tear breakup time, Schirmer I test, and Ocular Surface Disease Index questionnaire. After these examinations, corneal subbasal nerve plexus of the patients was evaluated with in vivo corneal confocal microscopy (IVCM) and the images were analyzed using fully automated software (ACC Metrics Corneal Nerve Fiber Analyzer V.2). There was no significant difference between the groups regarding age and gender distribution. Corneal sensation was significantly higher in patients with IC (P = 0.03), whereas tear breakup time, Schirmer I test, and Ocular Surface Disease Index scores were similar between the patients and controls. IVCM demonstrated nerve fiber loss in patients with IC. Corneal nerve fiber density, corneal nerve branch density, and corneal nerve fiber length were significantly reduced in patients with IC compared with healthy controls (P < 0.001, P = 0.04, and P < 0.001, respectively). Patients with IC had increased corneal sensation and decreased nerve fiber density in IVCM analysis. Corneal nerve fiber loss might decrease the induction threshold of the remaining fibers to induce peripheral sensitization, which may also trigger central sensitization in long term.

Corneal nerve loss is related to the severity of painful diabetic neuropathy

Background and purposePreviously it has been shown that patients with painful diabetic neuropathy (PDN) have greater corneal nerve loss compared to patients with painless diabetic neuropathy. This study investigated if the severity of corneal nerve loss was related to the severity of PDN.MethodsParticipants with diabetic neuropathy (n = 118) and healthy controls (n = 38) underwent clinical and neurological evaluation, quantitative sensory testing, nerve conduction testing and corneal confocal microscopy and were categorized into those with no (n = 43), mild (n = 34) and moderate‐to‐severe (n = 41) neuropathic pain.ResultsCorneal nerve fibre density (p = 0.003), corneal nerve fibre length (p < 0.0001) and cold perception threshold (p < 0.0001) were lower and warm perception threshold was higher (p = 0.002) in patients with more severe pain, but there was no significant difference in the neuropathy disability score (p = 0.5), vibration perception threshold (p = 0.5), sural nerve conduction velocity (p = 0.3) and amplitude (p = 0.7), corneal nerve branch density (p = 0.06) and deep breathing heart rate variability (p = 0.08) between patients with differing severity of PDN. The visual analogue scale correlated significantly with corneal nerve fibre density (r = −0.3, p = 0.0002), corneal nerve branch density (r = −0.3, p = 0.001) and corneal nerve fibre length (r = −0.4, p < 0.0001). Receiver operating curve analysis showed that corneal nerve fibre density had an area under the curve of 0.78 with a sensitivity of 0.73 and specificity of 0.72 for the diagnosis of PDN.ConclusionsCorneal confocal microscopy reveals increasing corneal nerve fibre loss with increasing severity of neuropathic pain and a good diagnostic outcome for identifying patients with PDN.

Corneal nerve loss as a surrogate marker for poor pial collaterals in patients with acute ischemic stroke

In patients with acute ischemic stroke, pial collaterals play a key role in limiting neurological disability by maintaining blood flow to ischemic penumbra. We hypothesized that patient with poor pial collaterals will have greater corneal nerve and endothelial cell abnormalities. In a cross-sectional study, 35 patients with acute ischemic stroke secondary to middle cerebral artery (MCA) occlusion with poor (n = 12) and moderate-good (n = 23) pial collaterals and 35 healthy controls underwent corneal confocal microscopy and quantification of corneal nerve and endothelial cell morphology. In patients with MCA stroke, corneal nerve fibre length (CNFL) (P < 0.001), corneal nerve fibre density (CNFD) (P = 0.025) and corneal nerve branch density (CNBD) (P = 0.002) were lower compared to controls. Age, BMI, cholesterol, triglycerides, HDL, LDL, systolic blood pressure, NIHSS and endothelial cell parameters did not differ but mRS was higher (p = 0.023) and CNFL (p = 0.026) and CNBD (p = 0.044) were lower in patients with poor compared to moderate-good collaterals. CNFL and CNBD distinguished subjects with poor from moderate-good pial collaterals with an AUC of 72% (95% CI 53–92%) and 71% (95% CI 53–90%), respectively. Corneal nerve loss is greater in patients with poor compared to moderate-good pial collaterals and may act as a surrogate marker for pial collateral status in patients with ischemic stroke.

Comparing the results of manual and automated quantitative corneal neuroanalysing modules for beginners

This study aimed to evaluate the reliability of in vivo confocal microscopic neuroanalysis by beginners using manual and automated modules. Images of sub-basal corneal nerve plexus (SCNP) from 108 images of 18 healthy participants were analyzed by 7 beginner observers using manual (CCMetrics, [CCM]) and automated (ACCMetrics, [ACCM]) module. SCNP parameters analyzed included corneal nerve fiber density (NFD), corneal nerve branch density (NBD), corneal nerve fiber length (NFL), and tortuosity coefficient (TC). The intra-observer repeatability, inter-observer reliability, inter-module agreement, and left–right eye symmetry level of SCNP parameters were examined. All observers showed good intra-observer repeatability using CCM (intraclass correlation coefficient [ICC] > 0.60 for all), except when measuring TC. Two observers demonstrated especially excellent repeatability in analyzing NFD, NBD, and NFL using manual mode, indicating the quality of interpretation may still be observer-dependent. Among all SCNP parameters, NFL had the best inter-observer reliability (Spearman’s rank-sum correlation coefficient [SpCC] and ICC > 0.85 for the 3 original observers) and left–right symmetry level (SpCC and ICC > 0.60). In the additional analysis of inter-observer reliability using results by all 7 observers, only NFL showed good inter-observer reliability (ICC = 0.79). Compared with CCM measurements, values of ACCM measurements were significantly lower, implying a poor inter-module agreement. Our result suggested that performance of quantitative corneal neuroanalysis by beginners maybe acceptable, with NFL being the most reliable parameter, and automated method cannot fully replace manual work.

Corneal nerve fiber loss relates to cognitive impairment in patients with Parkinson\u2019s disease

Cognitive impairment in Parkinson’s disease (PD) adversely influences quality of life. There is currently no available biomarker to predict cognitive decline in PD. Corneal confocal microscopy (CCM) has been used as a non-invasive tool for quantifying small nerve damage in PD. The present study investigated whether corneal nerve measures were associated with cognitive function in PD. Patients with PD were classified into those with normal cognitive function (PD-CN), mild cognitive impairment (PD-MCI), and dementia (PDD). Corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), and corneal nerve fiber length (CNFL) were quantified with CCM and compared with a control group. Sixty-five PD patients and thirty controls were studied. CNFD was decreased and CNBD was increased in PD patients compared to controls (P < 0.05). CNBD and CNBD/CNFD ratio was higher in PD-CN compared to controls. CNFD was positively correlated with the Montreal cognitive assessment (MoCA) score (r = 0.683, P < 0.001), but negatively associated with unified Parkinson disease rating scale (UPDRS)-part III (r = −0.481, P < 0.001) and total UPDRS scores (r = −0.401, P = 0.001) in PD patients. There was no correlation between CNFD and Levodopa equivalent daily dose (LEDD) (r = 0.176, P = 0.161). CNFD, CNBD, CNFL, and CNBD/CNFD ratio was lower with increasing Hoehn and Yahr stage. PD patients show evidence of corneal nerve loss compared with controls and corneal nerve parameters are associated with the severity of cognitive and motor dysfunction in PD. CCM could serve as an objective in vivo ophthalmic imaging technique to assess neurodegeneration in PD.

Characteristics of Toxic Keratopathy, an In Vivo Confocal Microscopy Study.

PurposeToxic keratopathy (TK) involves complex clinical manifestations and is difficult to differentiate from other ocular surface diseases by conventional slit-lamp examination. The challenge faced by clinicians in confidently diagnosing TK cannot be underestimated. This study aimed to explore the microstructural characteristics and diagnostic parameters by in vivo confocal microscopy (IVCM) in TK.MethodsIn this prospective, cross-sectional, comparative study, slit-lamp and IVCM examinations were performed on 20 normal eyes and 54 eyes with TK. Based on slit-lamp imaging, TK subjects were divided into four groups: superficial punctate keratitis (n = 10 eyes), pseudodendritic keratitis (n = 14 eyes), ulcerative keratitis (UK; n = 16 eyes), and ring keratitis (RK; n = 14 eyes). The microstructural characteristics of TK were described according to the following IVCM parameters: basal cell (BC) density, dendritiform cell (DC) density, DC size, corneal nerve fiber (CNF) length, nerve tortuosity, and keratocyte reflectivity. A receiver operating characteristic (ROC) curve model was also formulated to compare the predictive power of BC density, DC density, and CNF length.ResultsTK eyes showed significantly higher values for DC density (45.8 cells/mm2; range, 25.0–100.0) compared with normal eyes (24.0 cells/mm2; range, 20.8–32.3; P = 0.013; DC size (111.0 µm2; range, 92.0–137.8) compared with normal eyes (63.7 µm2; range, 47.7–70.3; P < 0.001); nerve tortuosity (0.08; range, 0.05–0.09) compared with normal eyes (0.04; range, 0.02–0.04; P < 0.001); and keratocyte reflectivity. BC density and CNF length values were found to be significantly less than those for normal controls (both P < 0.001). In all subgroups, CNF length appeared to be significantly lower than that of controls (all P < 0.001), and DC density was only statistically significantly higher in the UK (P = 0.003) and RK (P < 0.001) groups. Corneal fluorescein staining had no correlation with the analyzed IVCM parameters (all P ˃ 0.05). However, the increase in DC density and DC size showed negative correlations to CNF length (density: r = −0.325, P < 0.005; size: r = −0.493, P < 0.005), as well as positive correlations to duration and frequency of topical eye drops and DC size (density: r = 0.361, P < 0.05; size: r = 0.581, P < 0.05). A ROC curve showed that CNF length had the strongest predictive power, with the estimated area under the curve being 0.992 ± 0.008.ConclusionsLower BC density and CNF length, greater DC density and DC size, and greater keratocyte reflectivity were the microstructural characteristics of TK. The role of subbasal nerve, inflammatory response, and limbal stem cells in the progression of TK and the appropriate treatment of different TK stages are future research directions.Translational RelevanceThe evaluation of basal cells, subbasal nerve, and dendritiform cells is helpful to our understanding of the pathological process of TK.

Corneal confocal microscopy for the diagnosis of diabetic peripheral neuropathy: A systematic review and meta-analysis.

ABSTRACTIntroductionCorneal confocal microscopy (CCM) is a rapid non‐invasive ophthalmic imaging technique that identifies corneal nerve fiber damage. Small studies suggest that CCM could be used to assess patients with diabetic peripheral neuropathy (DPN).AimTo undertake a systematic review and meta‐analysis assessing the diagnostic utility of CCM for sub‐clinical DPN (DPN−) and established DPN (DPN+).Data sourcesDatabases (PubMed, Embase, Central, ProQuest) were searched for studies using CCM in patients with diabetes up to April 2020.Study selectionStudies were included if they reported on at least one CCM parameter in patients with diabetes.Data extractionCorneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), corneal nerve fiber length (CNFL), and inferior whorl length (IWL) were compared between patients with diabetes with and without DPN and controls. Meta‐analysis was undertaken using RevMan V.5.3.Data synthesisThirty‐eight studies including ~4,000 participants were included in this meta‐analysis. There were significant reductions in CNFD, CNBD, CNFL, and IWL in DPN− vs controls (P < 0.00001), DPN+ vs controls (P < 0.00001), and DPN+ vs DPN− (P < 0.00001).ConclusionThis systematic review and meta‐analysis shows that CCM detects small nerve fiber loss in subclinical and clinical DPN and concludes that CCM has good diagnostic utility in DPN.

The effect of Rho Kinase inhibition on corneal nerve regeneration in vitro and in vivo

PurposeImpairment of corneal nerves can lead to neurotrophic keratopathy accompanied with severe ocular surface damage, which due to limited treatment options, can result in severe visual deterioration. This study evaluates a possible new treatment by enhancing the corneal nerve regeneration using a Rho Kinase inhibitor (Y27632). ROCK is known to play an important role in regulating cell morphology, adhesion and motility but little is known about its role in corneal nerve regeneration. MethodsEffects of ROCK inhibition on murine peripheral nerves was assessed in single cell- and wound healing assays as well as a 3D in vitro model. Furthermore, Sholl analysis evaluating neuronal branching and life-death assays evaluating toxicity of the inhibitor were performed. An in vivo mouse model was established, with monitoring weekly corneal nerve regrowth using confocal microscopy. Additionally, corneal nerve fiber length was evaluated by immunofluorescence staining. Underlying pathways were examined by qrtPCR. ResultsROCK inhibition leads to a significant enhancement of fiber growth in vitro. Sholl analysis revealed a higher degree of branching of treated fibers. Cytotoxicity assay showed no influence of Y27632 on cellular survival. In vivo measurement revealed significant enhanced regeneration after injury in the treated group. QrtPCR of trigeminal ganglia confirmed ROCK knock-down as well as altered pathways. ConclusionThe inhibition of ROCK after corneal nerve injury resulted in an enhanced regrowth of fibers in vitro and in vivo. This might be a step towards a new therapeutic concept for the treatment of impaired corneal nerves in diseases such as neurotrophic keratopathy.

Tear Neuromediator and Corneal Denervation Following SMILE.

To investigate the changes in tear neuromediators and corneal subbasal nerve plexus following small incision lenticule extraction (SMILE) and to study its association with different refractive power of corrections. Thirty patients were included for tear neuromediator analysis (40 eyes) and corneal nerve analysis using in vivo confocal microscopy scans (20 eyes). Tear samples were collected preoperatively and 1 week and 1, 3, 6, and 12 months postoperatively and analyzed for the substance P, calcitonin gene-related peptide (CGRP), and nerve growth factor (NGF) concentrations using the enzyme-linked immunosor-bent assay (ELISA). Corneal nerve fiber density (CNFD), corneal nerve fiber length (CNFL), and corneal nerve branch density (CNBD) decreased significantly postoperatively, then gradually increased from 3 months onward, but did not recover to the baseline levels at 12 months. Tear substance P and CGRP levels remained stable over 12 months. Tear NGF levels demonstrated a small peak at 1 week before decreasing significantly compared to preoperative levels at 6 months (P = .03) and 12 months (P = .007). The 1-month reduction in CNFL, tear substance P, and CGRP concentrations were significantly correlated with the corrected spherical equivalent (SE) (r = 0.71 for CNFL; r = -0.33 to -0.52 at different time points for substance P and CGRP, respectively, all P < .05). Compared to the low to moderate myopia group, the high myopia group (corrected SE greater than -6.00 diopters) had a significantly greater decrease in CNFD, significantly higher tear substance P concentrations at 1 week, 1 month, and 6 months, and significantly higher tear CGRP concentrations at 1 and 6 months. These results provide new insight into the neurobiological responses and their potential implications in corneal nerve damage and recovery after SMILE. High myopia treatment was associated with greater corneal denervation and neuroinflammation. [J Refract Surg. 2021;37(8):516-523.].

Corneal confocal microscopy identifies corneal nerve fibre loss and increased dendritic cells in patients with long COVID

Background/AimsLong COVID is characterised by a range of potentially debilitating symptoms which develop in at least 10% of people who have recovered from acute SARS-CoV-2 infection. This study has quantified...

Using corneal confocal microscopy to compare Mecobalamin intramuscular injections vs oral tablets in treating diabetic peripheral neuropathy: a RCT

This randomized controlled study used corneal confocal microscopy (CCM) to compare the efficacy of Mecobalamin intramuscular injections vs oral tablets in treating mild to moderate diabetic peripheral neuropathy (DPN) by detecting early nerve fiber repair. Enrolled patients were randomized approximately 1:1 to receive Mecobalamin intramuscular injections (0.5 mg/day, 3 times/week) or Mecobalamin oral tablets (1.5 mg/day) for 8 weeks. Primary outcome was change of inferior whorl length (IWL) from baseline. Secondary outcomes included changes of corneal nerve fibre length (CNFL), corneal nerve fibre density (CNFD), corneal nerve branch density (CNBD) and the Survey of Autonomic Symptoms (SAS). 15 (93.75%) patients in the injection group and 17 (89.47%) patients in the tablet group completed the study. The injection treatment significantly improved patients’ IWL from baseline (21.64 ± 3.00 mm/mm2 vs 17.64 ± 4.83 mm/mm2, P < 0.01) while the tablet treatment didn’t. Additionally, the injection treatment led to significantly improved CNFL, CNBD and SAS from baseline (all P < 0.05) while the tablet treatment did not. No patient experienced any adverse events. In conclusion, CCM is sensitive enough to detect the superior efficacy of 8-week Mecobalamin intramuscular injection treatment for DPN compared to the oral tablet treatment.ClinicalTrials.gov registration number: NCT04372316 (30/04/2020).