Presence of Fleischer ring and prominent corneal nerves in keratoconus relatives and normal controls

AIMTo examine the occurrence of commonly known clinical signs of keratoconus (KC), i.e. Fleischer ring, prominent corneal nerves and thinning, among unaffected family members of KC patients and healthy control individuals.METHODSData of both eyes of 117 relatives of KC patients having no manifest disease based on videokeratography indices (KC relatives), and 142 controls were used for Pearson correlation and t-test statistics. Correlation of Fleischer ring, prominent corneal nerves and central pachymetry data were tested with each other and with videokeratography indices (KSI, KISA, 3 and 6 mm Fourier asymmetry, and I-S).RESULTSA moderate correlation was found between Fleischer ring and all examined topographical indices. Most important correlation was present with 6 mm Fourier asymmetry, and corneal pachymetry (r=0.272, P<0.001; r=-0.234, P=0.027, respectively). Similar correlations were found with prominent corneal nerves (r=0.234, P<0.001 for 6 mm Fourier asymmetry and r=-0.235, P=0.0265 for pachymetry). KC family members who exhibited Fleischer ring or prominent nerves had thinner and more asymmetric corneas than those without Fleischer ring or prominent corneal nerves (P<0.05 for pachymetry and topographic indices with t-test and Mann-Whitney rank sum test). Though rarely, Fleischer ring and prominent corneal nerves occurred among normal controls, indicating the existence of forme fruste cases in the normal population. Control subjects, who had corneal Fleischer ring or prominent nerves had corneas more similar to KC than other controls (t-test: increased KSI and KISA, P=0.048 and 0.012, respectively).CONCLUSIONIn KC family members and healthy individuals, Fleischer ring and prominent corneal nerves are associated with features of KC and may suggest a possibility of forme fruste KC. Searching for the possible presence of Fleischer ring or prominent nerves on the cornea may help in the decision whether or not to diagnose subclinical KC in a borderline case.

Interconnections between diabetic corneal neuropathy and diabetic retinopathy:diagnostic and therapeutic implications

Diabetic corneal neuropathy and diabetic retinopathy are ocular complications occurring in the context of diabetes mellitus.Diabetic corneal neuropathy refers to the progressive damage of corneal nerves.Diabetic retinopathy has traditionally been considered as damage to the retinal microvasculature.However,growing evidence suggests that diabetic retinopathy is a complex neurovascular disorder resulting from dysfunction of the neurovascular unit,which includes both the retinal vascular structures and neural tissues.Diabetic retinopathy is one of the leading causes of blindness and is frequently screened for as part of diabetic ocular screening.However,diabetic corneal neuropathy is commonly overlooked and underdiagnosed,leading to severe ocular surface impairment.Several studies have found that these two conditions tend to occur together,and they share similarities in their pathogenesis pathways,being triggered by a status of chronic hyperglycemia.This review aims to discuss the interconnection between diabetic corneal neuropathy and diabetic retinopathy,whether diabetic corneal neuropathy precedes diabetic retinopathy,as well as the relation between the stage of diabetic retinopathy and the severity of corneal neuropathy.We also endeavor to explore the relevance of a corneal screening in diabetic eyes and the possibility of using corneal nerve measurements to monitor the progression of diabetic retinopathy.

Clinical associations of corneal neuromas with ocular surface diseases

Corneal neuromas,also termed microneuromas,refer to microscopic,irregula rly-shaped enlargements of terminal subbasal nerve endings at sites of nerve damage or injury.The formation of corneal neuromas results from damage to corneal nerves,such as following corneal pathology or corneal or intraocular surge ries.Initially,denervated areas of sensory nerve fibers become invaded by sprouts of intact sensory nerve fibers,and later injured axons regenerate and new sprouts called neuromas develop.In recent years,analysis of corneal nerve abnormalities including corneal neuromas which can be identified using in vivo confocal microscopy,a non-invasive imaging technique with microscopic resolution,has been used to evaluate corneal neuropathy and ocular surface dysfunction.Corneal neuromas have been shown to be associated with clinical symptoms of discomfort and dryness of eyes,and are a promising surrogate biomarker for ocular surface diseases,such as neuropathic corneal pain,dry eye disease,diabetic corneal neuropathy,neurotrophic keratopathy,Sjogren's syndrome,bullous keratopathy,post-refra ctive surgery,and others.In this review,we have summarized the current literature on the association between these ocular surface diseases and the presentation of corneal microneuromas,as well as elaborated on their pathogenesis,visualization via in vivo confocal microscopy,and utility in monitoring treatment efficacy.As current quantitative analysis on neuromas mainly relies on manual annotation and quantification,which is user-dependent and labor-intensive,future direction includes the development of artificial intelligence software to identify and quantify these potential imaging biomarkers in a more automated and sensitive manner,allowing it to be applied in clinical settings more efficiently.Combining imaging and molecular biomarkers may also help elucidate the associations between corneal neuromas and ocular surface diseases.

Corneal nerve changes by anti-glaucoma medications examined by in vivo confocal microscopy

AIM:To evaluate the effects of antiglaucoma eye drops on corneal nerves by in vivo confocal microscopy(IVCM).METHODS:This study comprised 79 patients diagnosed with glaucoma and 16 healthy control individuals.Among the glaucoma patients,54 were treated with medication,while 25 remained untreated.Central corneal images were evaluated by IVCM,and then ACCMetrics was used to calculate the following parameters:corneal nerve fiber density(CNFD),branch density(CNBD),fiber length(CNFL),total branch density(CTBD),fiber area(CNFA),fiber width(CNFW),and fractal dimension(CNFrD).The correlation between IVCM parameters and drugs was evaluated using non-parametric measurements of Spearman’s rank correlation coefficient.RESULTS:The CNFD was reduced in glaucoma groups compared to healthy subjects(P<0.01).Patients using anti-glaucoma medications exhibited poorer confocal parameters compared to untreated patients.As the number of medications and usage count increased,CNFD,CNBD,CNFL,CTBD,CNFA,and CNFrD experienced a decline,while CNFW increased(all P<0.01).For the brinzolamide-therapy group,there was a significant decrease in CNFD and CNFL compared to the other monotherapy groups(P<0.001).In the absence of medication,CNFD in males was lower than that in females(P<0.05).Among patients under medication therapy,CNFD remained consistent between males and females.CONCLUSION:Antiglaucoma eye drops affect the microstructure of corneal nerves.IVCM and ACCMetrics are useful tools that could be used to evaluate the corneal nerve changes.

Diabetic corneal neuropathy as a surrogate marker for diabetic peripheral neuropathy

Diabetic neuropathy is a prevalent microvascular complication of diabetes mellitus,affecting nerves in all parts of the body including corneal nerves and peripheral nervous system,leading to diabetic corneal neuropathy and diabetic peripheral neuropathy,respectively.Diabetic peripheral neuropathy is diagnosed in clinical practice using electrophysiological nerve conduction studies,clinical scoring,and skin biopsies.However,these diagnostic methods have limited sensitivity in detecting small-fiber disease,hence they do not accurately reflect the status of diabetic neuropathy.More recently,analysis of alterations in the corneal nerves has emerged as a promising surrogate marker for diabetic peripheral neuropathy.In this review,we will discuss the relationship between diabetic corneal neuropathy and diabetic peripheral neuropathy,elaborating on the foundational aspects of each:pathogenesis,clinical presentation,evaluation,and management.We will further discuss the relevance of diabetic corneal neuropathy in detecting the presence of diabetic peripheral neuropathy,particularly early diabetic peripheral neuropathy;the correlation between the severity of diabetic corneal neuropathy and that of diabetic peripheral neuropathy;and the role of diabetic corneal neuropathy in the stratification of complications of diabetic peripheral neuropathy.

Corneal neuromediator profiles following laser refractive surgery

Laser refractive surgery is one of the most commonly performed procedures worldwide.In laser refractive surgery,Femtosecond Laser in Situ Keratomileusis and Refractive Lenticule Extraction have emerged as promising alternatives to microkeratome Laser in Situ Keratomileusis and Photorefractive Keratectomy.Following laser refractive surgery,the corneal nerves,epithelial and stromal cells release neuromediators,including neurotrophins,neuropeptides and neurotransmitters.Notably,nerve growth factor,substance P,calcitonin gene-related peptide and various cytokines are important mediators of neurogenic inflammation and corneal nerve regeneration.Alterations in neuromediator profiles and ocular surface parameters following laser refractive surgery are attributed to the surgical techniques and the severity of tissue insult induced.In this review,we will discuss the(1)Functions of neuromediators and their physiological and clinical significance;(2)Changes in the neuromediators following various laser refractive surgeries;(3)Correlation between neuromediators,ocular surface health and corneal nerve status;and(4)Future directions,including the use of neuromediators as potential biomarkers for ocular surface health following laser refractive surgery,and as adjuncts to aid in corneal regeneration after laser refractive surgery.

In vivo corneal confocal microscopic analysis in patients with keratoconus

AIM: To quantify corneal ultrastructure using laser scanning in vivo confocal microscopy(IVCM) in patients with keratoconus and control subjects. METHODS: Unscarred corneas of 78 keratoconic subjects without a history of contact lens use and 36age-matched control subjects were evaluated with slit-lamp examination(SLE), corneal topography and laser scanning IVCM. One eye was randomly chosen for analysis. Anterior and posterior stromal keratocyte,endothelial cell and basal epithelial cell densities and sub-basal nerve structure were evaluated.RESULTS: IVCM qualitatively demonstrated enlarged basal epithelial cells, structural changes in sub-basal and stromal nerve fibers, abnormal stromal keratocytes and keratocyte nuclei, and pleomorphism and enlargement of endothelial cells. Compared with control subjects, significant reductions in basal epithelial cell density( 5817 ± 306 cells / mm2 vs 4802 ±508 cells/mm2,P 【 0. 001), anterior stromal keratocyte density(800 ±111 cells/mm2 vs 555 ±115 cells/mm2, P 【0.001),posterior stromal keratocyte density(333±34 cells/mm2vs270 ±47 cells/mm2, P 【0.001), endothelial cell density(2875 ±223 cells/mm2 vs 2686 ±265 cells/mm2, P 【0.001),sub-basal nerve fiber density(31.2 ±8.4 nerves/mm2vs18.1 ±9.2 nerves/mm2, P 【0.001), sub-basal nerve fiber length(21.4±3.4 mm/mm2 vs 16.1±5.1 mm/mm2, P 【0.001),and sub-basal nerve branch density(median 50.0(first quartile 31.2- third quartile 68.7) nerve branches/mm2 vs median 25.0(first quartile 6.2- third quartile 45.3) nerve branches/mm2, P 【0.001) were observed in patients with keratoconus.CONCLUSION: Significant microstructural abnormalities were identified in all corneal layers in the eyes of subjects with keratoconus using IVCM. This non-invasive in vivo technique provides an important means to define and follow progress of microstructural changes in patients with keratoconus.

Correlation of the retinopathy degree with the change of ocular surface and corneal nerve in patients with type 2 diabetes mellitus

AIM:To investigate the change of ocular surface and corneal nerve and their correlation in patients suffering from type 2 diabetes mellitus under different degrees of retinopathy.METHODS:Totally 129 type 2 diabetes mellitus patients(257 eyes)were included.They were divided into three groups:no diabetic retinopathy(NDR)group(33 cases,66 eyes),non-proliferative diabetic retinopathy(NPDR)group(32 cases,64 eyes),and proliferative diabetic retinopathy(PDR)group(34 cases,67 eyes).Healthy normal individuals were enrolled as controls(30 cases,60 eyes).Ocular Surface Disease Index(OSDI)questionnaire was completed by all subjects,and dry eye analyzer was applied to examine tear meniscus height(TMH),first tear break-up time(FTBUT),average tear break-up time(ATBUT),tear film lipid layer thickness classification,and meibomian gland loss(MGL)score.Corneal nerve fiber density(CNFD),corneal nerve branch density(CNBD),corneal nerve fiber length(CNFL),and corneal nerve fiber tortuosity(CNFT)were examined by in vivo confocal microscopy(IVCM).The differences and correlation among these parameters were analyzed.RESULTS:Total OSDI score,TMH,FTBUT,ATBUT,tear film lipid layer thickness,MGL score,CNFD,CNBD,CNFL,and CNFT were statistically different among the four groups(P<0.05).In NDR group,CNFL was positively correlated with TMH(r=0.493,both P<0.01)and ATBUT(r=0.437,P<0.05).CNFL in NPDR group was positively correlated with TMH(r=0.642,P<0.01)and ATBUT(r=0.6,P<0.01).CNFL in PDR group was positively correlated with TMH(r=0.364,P<0.05)and ATBUT(r=0.589,P<0.01),with low negative correlation with MGL score(r=-0.331,P<0.05).CONCLUSION:With the progression of diabetic retinopathy,TMH,BUT,lipid layer thickness,CNFL,CNFD,and CNBD gradually decreased,while total OSDI score,MGL score,and CNFT increased.CNFL is correlated with TMH and ATBUT in diabetic patients.

Changes in corneal nerve morphology and function in patients with dry eyes having type 2 diabetes

BACKGROUND Dry eye syndrome(DES)is a common disease with various clinical manifestations.DES had a significant association with diabetes.Blink reflex(BR)is also known as trigeminal nerve facial reflex.The stimulation of corneal nerves is one of the origins of BR stimulation.The parasympathetic fibers sent out through the facial nerve are the outlet of tear reflexes.BR can be used to assess the function of the corneal nerve closed-loop;however,whether the BR changes in these patients is unclear.AIM To understand the morphology and function of the corneal nerve in patients with dry eyes having diabetes or not.METHODS This study enrolled 131 patients who visited the inpatient and outpatient services of ophthalmology and endocrinology departments between January 2019 to August 2020 with subjective symptoms of dry eyes and non-dry eye reasons,as well as volunteers such as colleagues.The patients were divided into four groups:DEwDM,with dry eyes having type 2 diabetes mellitus(T2DM);DMnDE,with T2DM not having dry eyes;DEnDM,with dry eyes not having diabetes;and nDMnDE,with neither dry eyes nor diabetes.The tear film break-up time,Schirmer I test,in vivo confocal microscopy,and BR were performed.RESULTS The DEwDM,DMnDE,DEnDM,and nDMnDE groups included 56,22,33,and 20 patients,respectively.Sex and age were not statistically different among the four groups.The nerve fiber length(NFL)of patients in the DEwDM,DEnDM,and DMnDE groups reduced(P<0.001,P=0.014,and P=0.001,respectively).No significant difference in corneal nerve fiber density(NFD)(P=0.083)and corneal nerve branch density(NBD)(P=0.195)was found among the four groups.The R1 Latency of blink reflexes increased only in the DEwDM group(P=0.008,P=0.001,P<0.001,compared with the DMnDE,DEnDM,and nDMnDE groups,respectively).The NBD and R1 Latency were different between DEwDM and DEnDM groups in patients with moderate and severe dry eyes.CONCLUSION The corneal nerve morphology changed in patients with dry eyes or diabetes,or with both,while the function of corneal nerve closed-loop reduced only in those with dry eyes and diabetes.

Clinical observation of recombinant human nerve growth factor in the treatment of neurotrophic keratitis

AIM:To characterize changes of corneal nerve morphology and tear indices in patients with neurotrophic keratitis(NK)treated with recombinant human nerve growth factor(rhNGF).METHODS:In a prospective observational study,six patients(nine eyes)were locally treated with rhNGF.Visual acuity,corneal fluorescein staining score,the heights of the tear river,lipid layer thickness(LLT),tear ferning(TF)test,conjunctival impression cytology(CIC)examination,the densities of cornea subbasal nerve fibers were determined before and after treatment.RESULTS:Compared with baseline,there was a significant difference in corneal fluorescence staining scores(P<0.01);all patient corneal epithelial defects recovered completely within 8wk,but there was no significant improvement in the height of the tear river(P=0.202).LLT was significantly increased when compared with baseline(P=0.042);however,the function of conjunctival goblet cells and mucin content did not significantly improve using the TF test and CIC examination(P=0.557,P=0.539).After 8wk of treatment,the average corneal subbasal nerve fiber density increased significantly(P<0.01),as did the number of corneal nerve fiber branches(P=0.001).CONCLUSION:RhNGF can increase the density of corneal subbasal nerve fibers,promote the healing of persistent corneal epithelial defects and corneal ulcers in patients with NK,also improving tear function partially.

Corneal subepithelial nerve fibers in type 2 diabetes:potential biomarker of diabetic neuropathy

AIM:To observe the changes in corneal subepithelial nerve fibers(CNFs)and Langerhans cells(LCs)in patients with type 2 diabetes using corneal laser confocal microscopy(CLCM).METHODS:A total of 60 patients(64 eyes),including 40 patients with type 2 diabetes(DM group)and 20 subjects without diabetes(control group)were included with CLCM.Neuron J plugin of Image J software were used for quantitative analysis of CNF length(CNFL),CNF density(CNFD),corneal nerve branch fiber density(CNBD),main branch length density,branch length density,corneal nerve fiber tortuosity(NT)score,and LCs density.An independent samples t-test to analyze the variability between the two groups was performed,and Pearson correlation analysis was used to analyze the relationships between CNF and multiple biochemical indicators in the DM group.The predictive power of CNF for type 2 diabetes was assessed using the receiver operating characteristic(ROC)curve.RESULTS:There were significant differences in the CNFL,CNFD,and main branch length density between two groups.The results of Pearson correlation analysis showed a significant negative correlation between CNFD and the duration of diabetes as well as triglyceride levels and total cholesterol,and a significant positive correlation between CNFD and serum albumin.In addition,the NT score showed a positive correlation and urea nitrogen,similar to the positive correlation observed between LC density and glycosylated hemoglobin(HbA1c)levels.CNFD showed the highest area under the curve(AUC of ROC)value,followed by main branch length density and CNFL.The AUC of the ROC curve under the logistic regression model also demonstrated good predictive values.The cut-off values of CNFD,CNFL,and main branch length density for diabetes showed 31.25,18.85,and 12.56,respectively.CONCLUSION:In patients with type 2 diabetes,there is a notable reduction in both CNFL and CNFD.These measurements can be influenced by various blood biochemical factors.However,the compromised nerve fibers can serve as valuable indicators for predicting the onset of type 2 diabetes and also as biomarkers for detecting diabetic neuropathy and its related complications.