Subnormal cytokine profile in the tear fluid of keratoconus patients

Keratoconus

Keratoconus is a progressive eye disorder primarily affecting individuals in adolescence and early adulthood. The ectatic changes in the cornea cause thinning and cone-like steepening leading to irregular astigmatism and reduced vision. Keratoconus is a complex disorder with a multifaceted aetiology and pathogenesis, including genetic, environmental, biomechanical and cellular factors. Environmental factors, such as eye rubbing, UV light exposure and contact lens wearing, are associated with disease progression. On the cellular level, a complex interplay of hormonal changes, alterations in enzymatic activity that modify extracellular membrane stiffness, and changes in biochemical and biomechanical signalling pathways disrupt collagen cross-linking within the stroma, contributing to structural integrity loss and distortion of normal corneal anatomy. Clinically, keratoconus is diagnosed through clinical examination and corneal imaging. Advanced imaging platforms have improved the detection of keratoconus, facilitating early diagnosis and monitoring of disease progression. Treatment strategies for keratoconus are tailored to disease severity and progression. In early stages, vision correction with glasses or soft contact lenses may suffice. As the condition advances, rigid gas-permeable contact lenses or scleral lenses are prescribed. Corneal cross-linking has emerged as a pivotal treatment aimed at halting the progression of corneal ectasia. In patients with keratoconus with scarring or contact lens intolerance, surgical interventions are performed.

Tear levels of apoptotic, matrix-degrading and antioxidant biomarkers in patients with and without keratoconus: A cross sectional study

PURPOSE

To assess the tear levels of a set of apoptotic, matrix-degrading and antioxidant biomarkers, including Metalloproteinase 9 (MMP9), High Mobility Group Box 1 (HMGB1) and Superoxide Dismutase 3-Extracellular (SOD3).

METHODS

Sandwich-ELISA commercial kits were used to test the expression of the three tear biomarkers in the lacrimal fluid of eligible participants. Linear logistic regression analysis was performed todetermine whether the set of tear biomarkers could be associated with clinically manifest keratoconus. ROC curve analysis using 10-fold cross-validation was performedto evaluate the prediction accuracy of the model.

RESULTS

Eighty-one participants aged 30-48 years old were enrolled in this study; 48 were patients with keratoconus and 33 were age-matched healthy subjects. The linear combination of the three tear biomarkers levels (AUC = 0.811; CI 95 %: 0.712-0.911) accurately indicated the existence of keratoconus; higher levels of MMP9 (Odd Ratio: 1.069; CI 95 %: 1.029-1.130) and HMGB1 (OR: 1.011; CI 95 %: 1.003-1.022) and lower levels of SOD3 (OR: 0.994; CI 95 %: 0.989-0.997) were significantly associated with a higher probability of keratoconus.

CONCLUSION

Multivariable analysis of the set of tear levels of MMP9, HMGB1 and SOD3 biomarkers confirmed a chronic state of inflammation in the ocular surface of patients with keratoconus.

Mendelian randomization reveals that abnormal lipid metabolism mediates the causal relationship between body mass index and keratoconus

Previous studies suggest that a high body mass index (BMI) may be a risk factor for keratoconus (KC), but the causal relationship remains unclear. This study used Mendelian randomization (MR) to investigate this connection and explore the mediating role of circulating serum metabolites and inflammatory factors in this association. Two-sample MR analysis was conducted to assess the relationship between BMI and KC. The study employed a two-step MR approach to evaluate the mediating roles of 91 inflammatory markers and 249 serum metabolites in the BMI-KC relationship. Inverse variance weighting (IVW) was the primary method, and multiple sensitivity analyses were performed to ensure robustness. IVW analysis revealed a positive causal relationship between BMI and KC (OR IVW = 1.811, 95% CI 1.005-3.262, P = 0.048). Although IL-12β and IL-4 were causally associated with KC, they did not mediate the BMI-KC relationship. Five serum metabolites were identified as potential mediators, with HDL cholesterol and triglyceride ratios showing significance. This study clarified the causal relationship between high BMI and KC, suggesting that high BMI may induce KC through lipid metabolism abnormalities. These findings underscore the importance of managing BMI for KC prevention.

Causal Association Between Atopic Dermatitis and Keratoconus: A Mendelian Randomization Study

Purpose

Although many studies have indicated that atopic dermatitis (AD) could contribute to the risk of keratoconus (KC), the causality between AD and KC remains controversial. This study aimed to explore the potential causal associations between AD and KC.

Methods

Instrumental variables for both exposures and outcomes were obtained from large-scale genome-wide association study summary statistics from previous meta-analyses. Mendelian randomization (MR) was applied to infer causal associations between AD and KC. Our main analyses were conducted by inverse-variance weighted (IVW) method multiplicative random effect model, complemented with additional five models and sensitivity analyses. Reverse MR analysis was applied to determine the direction of the causal association between AD and KC.

Results

Both IVW and weighted median methods revealed a causal effect of AD on KC (IVW odds ratio [OR], 1.475; P = 4.16 × 10-4; weighted median OR, 1.351; P = 7.65 × 10-3). The weighted mode, simple mode, and MR Egger methods demonstrated consistent direction of causality. Evidence from all sensitivity analyses further supported these associations. Reverse MR analyses did not suggest causal effects of KC on AD.

Conclusions

This study supported a significant causal effect of AD on KC, and reverse MR analysis proved that the causal association was unilateral.

Translational Relevance

This study provides valid evidence that regular ophthalmic examinations are recommended for patients with AD to detect and prevent KC at an early stage.

Targeted next-generation sequencing analysis in Italian patients with keratoconus

OBJECTIVE

To report variants in 26 candidate genes and describe the clinical features of Italian patients with keratoconus (KC).

SUBJECTS/METHODS

Sixty-four patients with a confirmed diagnosis of KC were enrolled in this genetic association study. Patients were classified into two study groups according to whether they had a confirmed diagnosis of progressive or stable KC. A purpose-developed Next Generation Sequencing (NGS) panel was used to identify and analyse the coding exons and flanking exon/intron boundaries of 26 genes known to be associated with KC and corneal dystrophies. Interpretation of the pathogenic significance of variants was performed using in silico predictive algorithms.

RESULT

The targeted NGS research identified a total of 167 allelic variants of 22 genes in the study population; twenty-four patients had stable keratoconus (n. 54 variants) and forty patients had progressive disease (n. 113 variants). We identified genetic variants of certain pathogenic significance in five patients with progressive KC; in addition, eight novel genetic variants were found in eight patients with progressive KC. Mutations of FLG, LOXHD1, ZNF469, and DOCK9 genes were twice more frequently identified in patients with progressive than stable disease. Filaggrin gene variants were found in 49 patients (76% of total), of whom 32 patients (80% of progressive KC group) had progressive disease.

CONCLUSIONS

Targeted NGS research provided new insights into the causative effect of candidate genes in the clinical phenotype of keratoconus. Filaggrin mutations were found to represent a genetic risk factor for development of progressive disease in Italy.

Pachychoroid pigment epitheliopathy in keratoconic eyes

PURPOSE

To report the association between keratoconus (KC) and pachychoroid pigment epitheliopathy (PPE). As secondary outcome, we explored the relation between subfoveal choroidal thickness (SFCT) and topometric indexes.

METHODS

Retrospective, observational, cross-sectional, case-control study. Multicentric study including patients with KC and healthy controls. Each subject underwent a complete ophthalmological visit, Placido-based corneal topography, Scheimpflug corneal tomography and spectral-domain OCT (SD-OCT) with the enhanced depth imaging (EDI) mode on. Linear mixed models (LMM) were employed for comparison between groups, and to examine the impact of different topometric factors on SFCT. KC stages were defined according to Belin grading.

RESULTS

Overall, 56 eyes from 35 KC patients and 52 eyes from 27 healthy, age- and axial length-matched control subjects were included in the study. PPE was found in 10 (17.9%) eyes from 8 KC patients, whereas was absent in all healthy controls. SFCT was statistically significantly higher in keratoconic eyes (median: 390 µm; interquartile range (IQR): 339 - 425 µm) compared to healthy eyes (median: 240 µm; IQR: 200 - 288 µm) (p < 0.001). SFCT did not differ across different KC stages and between keratoconic eyes with and without PPE.

CONCLUSIONS

PPE is a relatively frequent finding in eyes with KC, being present in about 1 out of 6 cases, regardless of disease stage.

KEY MESSAGES

What is known: Keratoconus (KC) is a corneal disorder commonly associated with other chorioretinal abnormalities. It is well known that keratoconic eyes display increased choroidal thickness, and the rare association between KC and central serous chorioretinopathy (CSC) has already been reported in the literature.

WHAT IS NEW

We identified an association between KC and pachychoroid pigment epitheliopathy (PPE), a precursor or forme fruste of pachychoroid diseases, such as CSC. PPE presence is independent from corneal parameters and is observed in about 1 out 6 KC eyes.

Inflammation and keratoconus: A comprehensive bidirectional Mendelian randomization analysis

An increasing body of evidence supports the involvement of inflammation and immune responses in the occurrence and development of keratoconus (KC). However, the causal relationship between inflammatory factors and KC remains unclear. We employed a 2-way Mendelian randomization (MR) approach to investigate the interaction between KC and inflammatory factors. Instrumental variables for 41 circulating inflammatory regulators and 12 matrix metalloproteinases (MMPs) were selected from genome-wide association studies of European ancestry. Summary statistics for KC were obtained from a genome-wide association study comprising 2116 cases and 24,626 controls of European ancestry. The primary analytical method for assessing causality was the inverse-variance weighted method. Two additional MR methods (MR-Egger and weighted median) were employed to complement the inverse-variance weighted results. In addition, several sensitivity analyses were conducted to evaluate heterogeneity, horizontal pleiotropy, and stability. Our findings indicated that genetically predicted higher levels of macrophage inflammatory protein-1β (odds ratio = 1.126, 95% confidence interval: 1.029-1.232, P = .01) and MMP-13 (odds ratio = 1.211, 95% confidence interval: 1.070-1.371, P = .003) were positively associated with an elevated risk of KC. Conversely, genetically predicted KC was associated with increased levels of interferon-gamma, interleukin-4, and MMP-1. Our current study provided suggestive evidence supporting causal associations of macrophage inflammatory protein-1β and MMP-13 with the risk of KC. In addition, KC appeared to affect the expression of interferon-gamma, interleukin-4, and MMP-1.

Subfoveal choroidal thickness increases after excimer laser-assisted penetrating keratoplasty but not after excimer laser-assisted deep anterior lamellar keratoplasty

To evaluate the impact of excimer laser-assisted deep anterior lamellar keratoplasty (Exc-DALK) and excimer laser-assisted penetrating keratoplasty (Exc-PKP) on subfoveal choroidal thickness (SFCT) in eyes with advanced keratoconus. A retrospective comparative clinical study, which compares the outcomes of 24 eyes treated with Exc-DALK (G1) against matched group of 43 eyes treated with Exc-PKP (G2) at both 2 months (T1) and 2 years (T2) postoperatively. Main outcomes included best-corrected visual acuity (BCVA), central macular thickness (CMT), and SFCT. Preoperatively, there were no significant differences between both groups regarding BCVA, CMT or SFCT (p > 0.05). There were no significant differences between both groups regarding BCVA at both follow-ups (p > 0.05). There were no significant differences between both groups regarding CMT at both follow-ups (p > 0.05). SFCT was higher in G2 than G1 at both follow-ups (p < 0.01). Compared to preoperative SFCT, there were no significant changes in SFCT in G1 at both follow-ups (p > 0.05). In G2, SFCT increased significantly at T1 (p < 0.01) and did not differ significantly at T2 (p = 0.17). SFCT increased significantly after Exc-PKP but not after Exc-DALK, which might indicate that Exc-DALK affects the choroid less and thus could represent a less traumatic approach to ocular tissue than Exc-PKP.

In Vitro Expression Analysis of Cytokines and ROS-Related Genes in Human Corneal Fibroblasts and Keratocytes of Healthy and Keratoconus Corneas

PURPOSE

To investigate expression of cytokines and ROS-related genes in stromal cells of healthy and keratoconus (KC) corneas.

METHODS

Expression analysis was performed for cytokines including several interleukins (IL), Tumor necrosis factor-α (TNF-α), Transforming growth factor-β1 (TGF-β1), Interferon-γ (IFN-γ) and ROS-related genes such as Catalase, Glutathione peroxidase 1, NADPH oxidase 1, superoxide dismutase 1 in corneal fibroblasts (HCFs/KC-HCFs) or keratocytes (Keratocytes/KC-Keratocytes) by qPCR and ELISA.

RESULTS

Gene and protein expression of most inflammatory markers was decreased in keratocytes compared to fibroblasts, whereas no differences were found between healthy and keratoconus cells for the majority of cytokines measured. TNF-α expression was increased at gene (KC keratocytes) and protein levels (supernatant of Keratocytes/KC-Keratocytes) compared to corneal fibroblasts. No differential expression of ROS-related genes was detected between healthy and diseased cells in both fibroblasts and keratocytes.

CONCLUSION

Increased expression of several inflammatory markers described as altered in KC was not evident in KC cells in vitro.

Identification of hub genes and molecular pathways in keratoconus by integrating bioinformatics and literature mining at the RNA level

OBJECTIVE

Keratoconus (KC) is a condition characterized by progressive corneal steepening and thinning. However, its pathophysiological mechanism remains vague. We mainly performed literature mining to extract bioinformatic and related data on KC at the RNA level. The objective of this study was to explore the potential pathological mechanisms of KC by identifying hub genes and key molecular pathways at the RNA level.

METHODS

We performed an exhaustive search of the PubMed database and identified studies that pertained to gene transcripts derived from diverse corneal layers in patients with KC. The identified differentially expressed genes were intersected, and overlapping genes were extracted for further analyses. Significantly enriched genes were screened using "Gene Ontology" (GO) and "Kyoto Encyclopedia of Genes and Genomes" (KEGG) analysis with the "Database for Annotation, Visualization, and Integrated Discovery" (DAVID) database. A protein-protein interaction (PPI) network was constructed for the significantly enriched genes using the STRING database. The PPI network was visualized using the Cytoscape software, and hub genes were screened via betweenness centrality values. Pathways that play a critical role in the pathophysiology of KC were discovered using the GO and KEGG analyses of the hub genes.

RESULTS

68 overlapping genes were obtained. Fifty genes were significantly enriched in 67 biological processes, and 16 genes were identified in 7 KEGG pathways. Moreover, 14 nodes and 32 edges were identified via the PPI network constructed using the STRING database. Multiple analyses identified 4 hub genes, 12 enriched biological processes, and 6 KEGG pathways. GO enrichment analysis showed that the hub genes are mainly involved in the positive regulation of apoptotic process, and KEGG analysis showed that the hub genes are primarily associated with the interleukin-17 (IL-17) and tumor necrosis factor (TNF) pathways. Overall, the matrix metalloproteinase 9, IL-6, estrogen receptor 1, and prostaglandin-endoperoxide synthase 2 were the potential important genes associated with KC.

CONCLUSION

Four genes, matrix metalloproteinase 9, IL-6, estrogen receptor 1, and prostaglandin endoperoxide synthase 2, as well as IL-17 and TNF pathways, are critical in the development of KC. Inflammation and apoptosis may contribute to the pathogenesis of KC.

Evaluation of Keratoconus Disease with Tear Cytokine and Chemokine Levels Before and After Corneal Cross-Linking Treatment

OBJECTIVES

To compare tear cytokine and chemokine levels of keratoconus (KC) patients with controls to perceive etiology distinctly and to clarify the molecular changes after cross-linking (CXL).

METHODS

Tear samples were gathered from 34 participants in this prospective study. Participants underwent anterior and posterior segment examinations with slit-lamp biomicroscopy. Patients were assessed by corneal topography before and 3 months after CXL. Flat (K1), steep (K2), and average keratometry (Kmean), cylinder (CYL), and central corneal thickness (CCT) values were evaluated. After 3 months from CXL, samples were re-collected, and comparisons were made with preoperative values.

RESULTS

Levels of IFN-gamma, IL-8, IL-12, IL-17, TNF-α, IL-4 and IL-13 were detected higher in KC patients (p= 0.008, p= 0.047, p= 0.001, p= 0.001, p= 0.001, p= 0.001, p= 0.027, respectively). After CXL IL-4, IL-5, IL-6, IL-7, IL-8, TNF-α levels showed significant decrease (p= 0.005, p= 0.045, p= 0.010, p= 0.022, p= 0.001, p=0.002, respectively). As for the topographic measurements, postoperative CCT values were increased whereas Kmean reduced after CXL (p < 0.001, p = 0.015, respectively). (p= 0.001, p= 0.027, respectively).

CONCLUSION

Our findings imply that inflammation plays a key role in the development of KC and that this link is influenced by CXL therapy.

Brillouin microscopy

The field of Brillouin microscopy and imaging was established approximately 20 years ago, thanks to the development of non-scanning high-resolution optical spectrometers. Since then, the field has experienced rapid expansion, incorporating technologies from telecommunications, astrophotonics, multiplexed microscopy, quantum optics and machine learning. Consequently, these advancements have led to much-needed improvements in imaging speed, spectral resolution and sensitivity. The progress in Brillouin microscopy is driven by a strong demand for label-free and contact-free methods to characterize the mechanical properties of biomaterials at the cellular and subcellular scales. Understanding the local biomechanics of cells and tissues has become crucial in predicting cellular fate and tissue pathogenesis. This Primer aims to provide a comprehensive overview of the methods and applications of Brillouin microscopy. It includes key demonstrations of Brillouin microscopy and imaging that can serve as a reference for the existing research community and new adopters of this technology. The article concludes with an outlook, presenting the authors' vision for future developments in this vibrant field. The Primer also highlights specific examples where Brillouin microscopy can have a transformative impact on biology and biomedicine.

Analysis of Cytokine and Chemokine Level in Tear Film in Keratoconus Patients before and after Corneal Cross-Linking (CXL) Treatment

Keratoconus (KC) is a degenerative corneal disorder whose aetiology remains unknown. The aim of our study was to analyse the expressions of cytokines and chemokines in KC patients before and after specified time intervals after corneal cross-linking (CXL) treatment to better understand the molecular mechanisms occurring before and after CXL in KC patients process of corneal regeneration.; Tear samples were gathered from 52 participants immediately after the CXL procedure and during the 12-month follow-up period. All patients underwent a detailed ophthalmological examination and tear samples were collected before and after CXL at regular intervals: 1 day before and after the surgery, at the day 7 visit, and at 1, 3, 6, 9, and 12 months after CXL. The control group consisted of 20 healthy people. 10 patients were women (50%) and 10 were men (50%). The mean age was 30 ± 3 years of age. Tear analysis was performed using the Bio-Plex 3D Suspension Array System. Corneal topography parameters measured by Scheimpflug Camera included: keratometry values (Ks, Kf), PI-Apex, PI-Thinnest, Cylinder.; All the 12 months post-op values of the KC patients' topographic measurements were significantly lower than the pre-op. As for the tear cytokine levels comparison between the patient and control groups, cytokine levels of TNF-α, IL-6, and CXCL-10, among others, were detected in lower amounts in the KC group. The pre-op level of IL-6 exhibited a significant increase the day after CXL, whereas comparing the day after the procedure to 12 months after CXL, this showed a significant decrease. Both TNF-α and IL-1 showed a significant decrease compared to the day before and after CXL. We observed significantly higher levels of IL-1β, IL-10, IFN-γ and TNF-α in moderate and severe keratoconus than in mild keratoconus (p < 0.05). We also demonstrated a statistically significant positive correlation between both pre-op and 12 months after CXL TNF-α, IFN-γ, IL-6 and Ks and Kf values (p < 0.05, r > 0); Alterations of inflammatory mediators in tear fluid after CXL link with topographic changes and may contribute to the development and progression of KC.

Pathogenesis of Common Ocular Diseases: Emerging Trends in Extracellular Matrix Remodeling

The prevalence of visual impairments in human societies is worrying due to retinopathy complications of several chronic diseases such as diabetes, cardiovascular diseases, and many more that are on the rise worldwide. Since the proper function of this organ plays a pivotal role in people's quality of life, identifying factors affecting the development/exacerbation of ocular diseases is of particular interest among ophthalmology researchers. The extracellular matrix (ECM) is a reticular, three-dimensional (3D) structure that determines the shape and dimensions of tissues in the body. The ECM remodeling/hemostasis is a critical process in both physiological and pathological conditions. It consists of ECM deposition, degradation, and decrease/increase in the ECM components. However, disregulation of this process and an imbalance between the synthesis and degradation of ECM components are associated with many pathological situations, including ocular disorders. Despite the impact of ECM alterations on the development of ocular diseases, there is not much research conducted in this regard. Therefore, a better understanding in this regard, can pave the way toward discovering plausible strategies to either prevent or treat eye disorders. In this review, we will discuss the importance of ECM changes as a sentimental factor in various ocular diseases based on the research done up to now.

Level of Secretion and the Role of the Nerve Growth Factor in Patients with Keratoconus before and after Collagen Fibre Cross-Linking Surgery

BACKGROUND

The aim of this study was to analyse the concentration of the nerve growth factor (NGF-β) in patients with keratoconus (KC) who are undergoing collagen fibre cross-linking (CXL) surgery in order to better understand the pathogenesis of this disease and observe the molecular changes occurring after the procedure. Among many cytokines, β-NGF seems to play an important role in the healing processes of corneal damage. Therefore, its role in the regenerative process after CXL treatment may affect the course of treatment and its final results. Tear samples from 52 patients were collected in this prospective study. Additionally, the patients also had a number of tests performed, including corneal topography using optical coherence tomography. Flat (K 1), steep (K 2), cylindrical (CYL), and central corneal thickness (CCT) keratometry were assessed. The tear samples were collected, and other tests were performed before the CXL procedure and afterwards, during the 12-month follow-up period. The NGF concentration was measured using the Bio-Plex Magnetic Luminex Assay. Lower levels of NGF-β were detected in the KC patients than in the control group (p < 0.001). The day after the procedure, the NGF-β level was significantly lower (on average by 2.3 pg/mL) (p = 0.037) than before the procedure, after which, the level of the reagent increases, but only in the group with the advanced cone, one month after CXL it was significantly higher (p = 0.047). Regarding the correlation of NGF with topographic measurements, the following were found: NGF-β correlates significantly (p < 0.05) and positively (r > 0) with K1 before the CXL procedure; NGF-β correlates significantly (p < 0.05) and positively (r > 0) with K1 one month after CXL; NGF-β correlates significantly (p < 0.05) and positively (r > 0) with CYL nine months after CXL; and, after twelve months, NGF-β correlates significantly (p < 0.05) and positively (r > 0) with K2 and K1. Corneal sensitivity did not statistically and significantly correlate with the level of NGF-β secretion. Our study suggests that NGF may be crucial in the development and progression of KC as well as in the repair mechanisms after CXL surgery. Further research is needed on the role of NGF and other inflammatory biomarkers for rapid diagnosis and selection of targeted therapy in patients with keratoconus.

Tear Fluid Inflammatory Proteome Analysis Highlights Similarities Between Keratoconus and Allergic Conjunctivitis

Purpose

Keratoconus is characterized by the progressive thinning of the cornea, which leads to a cone-like appearance of the eye over time. Although conventionally defined as a noninflammatory condition, a number of recent studies have associated keratoconus (KC) with allergic conjunctivitis (AC) based on clinical parameters. This study aimed to consolidate this association by performing a proteomic analysis of tear fluid from patients with keratoconus and/or allergic conjunctivitis.

Methods

Of 51 patients, 17 were diagnosed with KC, 17 were diagnosed with AC, and 17 were diagnosed with both KC and AC (combined). Nine of 34 patients with KC had a progressive form of the disease. Tear fluid samples (n = 51, one eye per patient) were collected by the Schirmer's strips. Tear proteins were extracted from the Schirmer's strips. Proteomic profiling of 384 inflammatory proteins was assessed by a multiplex proximity extension assay (Olink Explore 384 Inflammation Panel I).

Results

A total of 384 inflammatory proteins were measured. Two hundred seventy-two of the 384 proteins passed stringent data cleaning and were compared among the patient groups. Compared to the 2 other groups, LGALS9 was upregulated uniquely in KC, whereas FGF19, PDGFB, HPCAL1, OSM, and FCAR were downregulated in KC. Similarly, TNFRSF4 and CCL13 were specifically upregulated in AC, whereas ectodysplasin A receptor (EDAR) was uniquely downregulated in AC.

Conclusions

High-throughput proteomic profiling of tear fluid confirms the association between KC and AC on a molecular level and raise the importance of redefining KC as an inflammatory condition.

Identification of the immune-associated characteristics and predictive biomarkers of keratoconus based on single-cell RNA-sequencing and bulk RNA-sequencing

Background

Whether keratoconus (KC) is an inflammatory disease is currently debated. Hence, we aimed to investigate the immune-related features of KC based on single-cell RNA sequencing (scRNA-seq) and bulk RNA sequencing (bulk RNA-seq) data.

Methods

scRNA-seq data were obtained from the Genome Sequence Archive (GSA), bulk RNA-seq data were obtained from the Gene Expression Omnibus (GEO), and immune-associated genes(IAGs) were obtained from the ImmPort database. Cell clusters of KC were annotated, and different cell clusters were then selected. The IAG score of each cell was calculated using the AUCell package. Three bulk RNA-seq datasets were merged and used to identify the differentially expressed genes (DEGs), biological functions, and immune characteristics. Weighted gene coexpression network analysis (WGCNA) was used to select the IAG score-related hub genes. Based on scRNA-seq and bulk RNA-seq analyses, three machine learning algorithms, including random forest (RF), support vector machine (SVM), and least absolute shrinkage and selection operator (LASSO) regression analysis, were used to identify potential prognostic markers for KC. A predictive nomogram was developed based on prognostic markers.

Results

Six cell clusters were identified in KC, and decreased corneal stromal cell-5 (CSC-5) and increased CSC-6 were found in KC. CSC and immune cell clusters had the highest IAG scores. The bulk RNA-seq analysis identified 1362 DEGs (553 upregulated and 809 downregulated) in KC. We found different immune cell populations and differentially expressed cytokines in KC. More than three key IAG score-related modules and 367 genes were identified. By integrating the scRNA-seq and bulk RNA-seq analyses, 250 IAGs were selected and then incorporated into three machine learning models, and 10 IAGs (CEP112, FYN, IFITM1, IGFBP5, LPIN2, MAP1B, RNASE1, RUNX3, SMIM10, and SRGN) were identified as potential prognostic genes that were significantly associated with cytokine and matrix metalloproteinase(MMP)1-14 expression. Finally, a predictive nomogram was constructed and validated.

Conclusion

Taken together, our results identified CSCs and immune cell clusters that may play a key role during KC progression by regulating immunological features and maintaining cell stability.

Ocular surface inflammation and ectatic corneal disorders

PURPOSE OF REVIEW

Inflammatory mediators are a focus of recent corneal ectasia (CE) research and are a profound, modifiable contributor to CE in general and keratoconus (KC) in particular, opening a path to explore new methods of control. As advanced imaging technology and expanded population screening allow for earlier detection, the possibility of early intervention can profoundly change the prognosis of CE.

RECENT FINDINGS

Significant increases in the inflammatory mediators and immune components have been observed in the cornea, tear fluid, and blood of ectasia patients, while inflammation dampeners such as vitamin D and their receptors are reduced. Atopy and allergy have a strong association with KC, known to increase itch factors and stimulate eye rubbing, a risk factor in ectasia pathogenesis. Management of atopy or allergic conditions and topical anti-inflammatories has helped stabilize CE disease.

SUMMARY

Strategies such as monitoring inflammatory factors and using immune or inflammatory modulators, including managing subclinical inflammation, may be clinically beneficial in stabilizing the disease and improving outcomes. The detected factors are biomarkers, but as yet unproven to be sensitive or specific enough to be considered biomarkers for early detection of CE. The establishment of such biomarkers could improve the therapeutic outcome.

Eye Rubbing in Chinese Patients With Keratoconus: A Multicenter Analysis

PURPOSE

To investigate the eye rubbing habits of Chinese patients with keratoconus.

METHODS

This study was carried out from 2018 to June 2022 at Shandong Eye Hospital, Qingdao Eye Hospital, and Henan Eye Hospital. The study compared the number of patients who rubbed their eyes between medical records and second time questionnaires, eye rubbing of patients with myopia and patients with keratoconus, and disease severity between patients with keratoconus. A questionnaire survey of ophthalmologists was conducted to determine their degree of awareness that eye rubbing is a risk factor for keratoconus.

RESULTS

The study assessed 799 patients with keratoconus and 798 control patients, and 97 ophthalmologists. The average proportion of patients with keratoconus who rubbed their eyes was 31.0% in the medical records with an increasing trend related to the increase in ophthalmologists' awareness, 66.6% after the second follow-up, and 25.4% among patients with myopia. After multivariate analysis, the following variables showed significant results: eye rubbing frequency more than 10 times/day (odds ratio [OR], 9.168; P < .001); rubbing with knuckles (OR, 9.804; P = .001); and prone sleep position (OR, 12.427; P < .001). The proportion of patients who rubbed their eyes with stage IV keratoconus was 71.9%, 18.9% higher than those with stage I, 4.8% higher than stage II, and 17.8% higher than stage III.

CONCLUSIONS

The proportion of Chinese patients with keratoconus who rubbed their eyes was relatively high. The main reasons for the low proportions reported were lack of attention. Clinical attention should be paid to eye rubbing in patients with keratoconus who should be educated to avoid it. [J Refract Surg. 2023;39(10):712-718.].

Characteristics of Autophagy-Related Genes, Diagnostic Models, and Their Correlation with Immune Infiltration in Keratoconus

Purpose

Keratoconus (KTCN) is one of the most common degenerative keratopathies, significantly affecting vision and even leading to blindness. This study identifies potential biomarkers of KTCN based on the characterization of autophagy-related genes (ARGs) and the construction of a diagnostic model; and explores their relevance to immune infiltrating cells in KTCN.

Methods

Gene Expression Omnibus (GEO) data were downloaded and ARGs were acquired from GeneCards and Molecular Signatures Database (MSigDB). Autophagy-related differential expression genes (ARDEGs) were discovered through the integration of differentially expressed genes (DEGs) with ARGs, while hub genes of KTCN were discovered by protein-protein interaction (PPI) network analysis. The probable biological roles of these hub ARDEGs were examined using functional enrichment analysis, and a KTCN diagnostic model was generated using the least absolute shrinkage and selection operator (LASSO) regression analysis. We also employed the CIBERSORTx and ssGSEA algorithms to identify potential regulatory pathways to compare the abundance of immune cell infiltrates and their association with hub genes. Finally, the hub gene expression levels were confirmed using validation datasets as well as blood samples from KTCN and healthy individuals.

Results

In this study, we identified 12 hub ARDEGs, of which 9 genes were substantially distinct between KTCN patients and normal groups. The LASSO risk score was used to generate the nomogram, and the calibration curve evaluated the model's effective diagnostic performance (C index of 0.961). Patients with KTCN had greater percentages of M2 Macrophages and Gamma delta T cells, according to CIBERSORTx and ssGSEA. The outcomes of the bioinformatics analysis were supported by the DDIT3 and BINP3 expression levels in KTCN patients and healthy controls, according to the qRT-PCR data.

Conclusion

Five biomarkers (CFTR, PLIN2, DDIT3, BAG3, and BNIP3) and diagnostic models offer fresh perspectives on identifying and managing KTCN.

Inflammatory profile of keratoconic corneal epithelium

BACKGROUND

Recent studies have presented inflammatory features on keratoconus (KC) and many inflammatory markers are described in the tears of patients with this disease. The KC pathogenesis is still unknown just like the correlation with inflammatory patterns. However, environmental and genetic issues may be part of the progress of KC. In addition, some systemic features, such as allergy and obesity, seem to be related to the progression of KC. Our purpose was to evaluate the neuropeptides vasoactive intestinal peptide (VIP), neuropeptide Y (NPY), chemokines ligand 2 (CCL-2) and 5 (CCL-5), and interleukins 6 (IL-6) and 8 (IL-8) on corneal epithelial cells and blood of patients with KC and in healthy controls. In addition, the neutrophil-to-lymphocyte ratio (NLR) was evaluated to predict inflammation.

METHODS

This including prospective observational study included 32 KC patients who underwent corneal crosslinking (CXL) and 32 control patients who underwent photorefractive keratectomy (PRK). Patients' corneal epithelial cells were removed surgically, and blood (buffy coat) was analyzed. Samples in triplicate were evaluated on rt-PCR for neuropeptides (VIP e NPY), interleukins (IL-6 e IL-8), and chemokines (CCL-2 and CCL-5).

RESULTS

Our study showed statistically higher CCL-5 and IL-8 on corneal epithelial cells in patients with KC. Blood cells were statistically higher in VIP and NPY in the KC group. Interleukin-8 on blood cells was statistically significant in KC'S group; for CCL-2 and CCL-5 they were statistically lower in patients with KC compared with controls. NLR showed no difference between the groups.

CONCLUSIONS

Our data support the findings of other studies that suggested altering KC status, such as inflammatory corneal disease. The presence of IL-8 in the cornea and blood samples of KC's group suggested systemic disease with a possible local or repercussion action. Further studies are warranted to elucidate KC pathogenesis and its correlation to systemic disease.

Sequence variants contributing to dysregulated inflammatory responses across keratoconic cone surface in adolescent patients with keratoconus

Background

Keratoconus (KTCN) is the most common corneal ectasia resulting in a conical shape of the cornea. Here, genomic variation in the corneal epithelium (CE) across the keratoconic cone surface in patients with KTCN and its relevance in the functioning of the immune system were assessed.

Methods

Samples from four unrelated adolescent patients with KTCN and two control individuals were obtained during the CXL and PRK procedures, respectively. Three topographic regions, central, middle, and peripheral, were separated towards the whole-genome sequencing (WGS) study embracing a total of 18 experimental samples. The coding and non-coding sequence variation, including structural variation, was assessed and then evaluated together with the previously reported transcriptomic outcomes for the same CE samples and full-thickness corneas.

Results

First, pathway enrichment analysis of genes with identified coding variants pointed to "Antigen presentation" and "Interferon alpha/beta signaling" as the most overrepresented pathways, indicating the involvement of inflammatory responses in KTCN. Both coding and non-coding sequence variants were found in genes (or in their close proximity) linked to the previously revealed KTCN-specific cellular components, namely, "Actin cytoskeleton", "Extracellular matrix", "Collagen-containing extracellular matrix", "Focal adhesion", "Hippo signaling pathway", and "Wnt signaling" pathways. No genomic heterogeneity across the corneal surface was found comparing the assessed topographic regions. Thirty-five chromosomal regions enriched in both coding and non-coding KTCN-specific sequence variants were revealed, with a most representative 5q locus previously recognized as involved in KTCN.

Conclusion

The identified genomic features indicate the involvement of innate and adaptive immune system responses in KTCN pathogenesis.

Features of the local cytokine profile of patients with bullous keratopathy by using personalized therapy with cellular technologies

Background. Today we have active development of ophthalmic surgery, but the role of cytokines in the pathogenesis of bullous keratopathy of the cornea remains insufficiently studied at present.

The aim. To study the dynamics of the local cytokine profile in bullous keratopathy by using personalized treatment with suspension of autologous blood mononuclears.

Material and methods. Two groups of patients with bullous keratopathy were formed: the main group (30 people, 30 eyes), who received an intrastromal injection of a suspension of autologous blood mononuclears and comparison (28 people, 28 eyes), who received a course of pharmacotherapy. The level of interleukins (IL) – IL-10, IL-4, IL-6, IL-1ß, transforming growth factor beta-2 (TGF-β2), tumor necrosis factor alpha (TNF-α) was determined in the lacrimal fluid of the patient’s eye by enzyme immunoassay.

Results. All patients before treatment showed an increase of IL-1ß in the lacrimal fluid by 3.3 times, IL-6 – by 4.2 times, TNF-α – by 2.0 times (p < 0.05); an increase in the level of IL-4, IL-10 and TGF-β2 by 1.1 times (p > ˂ 0.05). In the main group, after treatment, there was a decrease in IL-1ß by 2.0 times, IL-6 – by 2.1 times and TNF-α – by 1.8 times, and an increase in IL-10 by 1.5 times, IL-4 – by 1.9 times, TGF-β2 – by 1.4 times (p < 0.05), persisting for 12 months. There was a short-term decrease of IL-1ß by 1.7 times, IL-6 and TNF-α – by 1.2 times and an increase of IL-10, IL-4, TGF-β2 by 1.2 times (p >< 0.05) in the comparison group which then reached the initial values. Conclusion. There is an imbalance in the system of pro- and anti-inflammatory cytokines in bullous keratopathy in the lacrimal fluid. Injection of autologous mononuclear cells in the stroma of the cornea reduces the severity of the imbalance of the local cytokine system compared to the course of pharmacotherapy. Key words: bullous keratopathy, cellular technologies, autologous mononuclear leukocytes, cytokines>˂ 0.05), persisting for 12 months. There was a short-term decrease of IL-1ß by 1.7 times, IL-6 and TNF-α – by 1.2 times and an increase of IL-10, IL-4, TGF-β2 by 1.2 times (p ˂ 0.05) in the comparison group which then reached the initial values.

Conclusion. There is an imbalance in the system of pro- and anti-inflammatory cytokines in bullous keratopathy in the lacrimal fluid. Injection of autologous mononuclear cells in the stroma of the cornea reduces the severity of the imbalance of the local cytokine system compared to the course of pharmacotherapy. 

The Impaired Wound Healing Process Is a Major Factor in Remodeling of the Corneal Epithelium in Adult and Adolescent Patients With Keratoconus

Purpose

Keratoconus (KTCN) is the most common corneal ectasia, characterized by pathological cone formation. Here, to provide an insight into the remodeling of the corneal epithelium (CE) during the course of the disease, we evaluated topographic regions of the CE of adult and adolescent patients with KTCN.

Methods

The CE samples from 17 adult and 6 adolescent patients with KTCN, and 5 control CE samples were obtained during the CXL and PRK procedures, respectively. Three topographic regions, central, middle, and peripheral, were separated toward RNA sequencing and MALDI-TOF/TOF Tandem Mass Spectrometry. Data from transcriptomic and proteomic investigations were consolidated with the morphological and clinical findings.

Results

The critical elements of the wound healing process, epithelial-mesenchymal transition, cell-cell communications, and cell-extracellular matrix interactions were altered in the particular corneal topographic regions. Abnormalities in pathways of neutrophils degranulation, extracellular matrix processing, apical junctions, IL, and IFN signaling were revealed to cooperatively disorganize the epithelial healing. Deregulation of the epithelial healing, G2M checkpoints, apoptosis, and DNA repair pathways in the middle CE topographic region in KTCN explains the presence of morphological changes in the corresponding doughnut pattern (a thin cone center surrounded by a thickened annulus). Despite similar morphological characteristics of CE samples in adolescents and adults with KTCN, their transcriptomic features were different. Values of the posterior corneal elevation differentiated adults with KTCN from adolescents with KTCN and correlated with the expression of TCHP, SPATA13, CNOT3, WNK1, TGFB2, and KRT12 genes.

Conclusions

Identified molecular, morphological, and clinical features indicate the effect of impaired wound healing on corneal remodeling in KTCN CE.

Cataract surgery in patients with underlying keratoconus: focused review

An underlying diagnosis of keratoconus (KC) can complicate cataract surgery. In this study, the results of a focused review of the literature pertaining to cataract surgery in patients with KC are detailed. Topics essential for the appropriate management of this patient population are discussed. First, the individual and shared epidemiology and pathophysiology of cataract and KC are reviewed. Then, the theory and approach to intraocular lens power calculation are discussed, highlighting particularities and pitfalls of this exercise when performed in patients with KC. Finally, several special-although not uncommon-management scenarios and questions are addressed, such as surgical planning in cases where corneal stabilization or tissue replacement interventions are also necessitated.

Changes in Tear Proteomic Profile in Ocular Diseases

The search for proteomic biomarkers in ocular disease is one of the most important research directions in recent years. Reliable biomarkers can be an immense adjuvant for both diagnostic and therapeutic approaches. There is no more readily available ocular tissue for proteomic analysis than tear film, which makes an interesting target for the biomarker search. Tear film is a complex fluid consisting of a superficial lipid layer, which covers the aqueous-mucous layer. Its complexity makes it a perfect candidate for all the "omics" approaches. Glaucoma, cataract, age-related macular degeneration, and other diseases are commonly thought to have a multifactorial background. Currently, no reliable non-invasive tests are available that would help physicians with screening and further patient management. The aim of the study is to present modern methods of measuring biomarkers in tears, with particular emphasis on spectrometric methods, and to discuss their diagnostic and therapeutic usefulness.

Exosomes Released by Corneal Stromal Cells Show Molecular Alterations in Keratoconus Patients and Induce Different Cellular Behavior

Exosomes have been related to various disorders, but their study in relation to ocular pathologies has been limited. In this article, we analyze exosomes produced by corneal stromal cells from healthy individuals and from patients with keratoconus. The proteomic study allowed for the identification of 14 new proteins with altered expression, related to molecules previously associated with the pathology. miRNA analysis detected 16 altered species, including miR-184, responsible for familial severe keratoconus. The prediction of its potential biological targets identified 1121 genes, including some related to this pathology. Exosomes produced by keratoconic cells induced a marked increase in the migration of stromal cells and corneal epithelium, while those produced by healthy cells had no effect on stromal cells. Both types of nanovesicles reduced the proliferation of stromal and corneal cells, but those produced by healthy cells had less effect. Exosomes produced by healthy cells had concentration-dependent effects on the transcription of genes encoding proteoglycans by keratoconus cells, with a relative normalization observed at concentrations of 240 µg/mL. These results show the alteration of stromal exosomes in keratoconus and suggest an influence on the development of the pathology, although the use of healthy exosomes could also have therapeutic potential.

Identification of Key Genes and Molecular Pathways in Keratoconus: Integrating Text Mining and Bioinformatics Analysis

Purpose. To identify the potential key genes and molecular pathways associated with keratoconus and allergic disease. Methods. The pubmed2ensembl database was used to identify the text mining genes (TMGs) collectively involved in keratoconus and allergic disease. The GeneCodis program was used to perform the Gene Ontology (GO) biological process and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of TMGs. The protein-protein interaction (PPI) network of the TMGs was established by STRING; the significant gene modules and hub genes of PPI were further performed using the Cytoscape software. The DAVID database was used to perform the GO and KEGG analyses of the significant module. Results. In total, 98 TMGs collectively involved in keratoconus and allergic disease were identified. 19 enriched biological processes including 71 genes and 25 enriched KEGG pathways including 59 genes were obtained. A TMG PPI network was constructed, and 51 genes/nodes were identified with 110 edges; 3 most significant modules and 12 hub genes were chosen from the PPIs. GO enrichment analysis showed that the TMGs were primarily associated with collagen catabolic process, extracellular matrix organization and disassembly, cell adhesion and migration, collagen-containing extracellular matrix, extracellular matrix, and structure organization. KEGG pathway analysis showed that these DEGs were mainly involved in the IL-17 signaling pathway, inflammatory bowel disease, rheumatoid arthritis, allograft rejection, T cell receptor signaling pathway, cytokine-cytokine receptor interaction, and TNF signaling pathway. Conclusions. The results revealed that IL10, IL6, MMP9, MMP1, HGF, VEGFA, MMP3, MMP2, TGFB1, IL4, IL2, and IFNG were potential key genes involved in keratoconus. IL-17 signaling pathway was the potential pathways accounting for pathogenesis and development of keratoconus.

Update on Pediatric Corneal Diseases and Keratoplasty

Managing pediatric corneal disorders is challenging as the prognosis of pediatric keratoplasty depends on several factors. Advancements in the genetic basis of congenital corneal diseases and investigations in congenital corneal conditions provide a better understanding of pediatric corneal conditions. Surgeons performing keratoplasty in children now have a choice of various techniques. Evolving surgical techniques of anterior lamellar and endothelial keratoplasties has expanded the management interventions in these pediatric corneal morbidity conditions; however, considerable concerns still exist in association with corneal transplantation in infants and children. Outcomes in pediatric keratoplasty depend upon the preoperative indications, the timing of surgical intervention, intraoperative and postoperative factors including the patient/care givers' compliance. Factors such as low scleral rigidity, higher rate of graft failure, need for frequent examinations under anesthesia, and difficulty in optimal visual acuity assessment still remain a considerable challenge in pediatric scenarios. In children, deprivation amblyopia as a result of the corneal opacification can adversely affect visual development, causing dense amblyopia. Outcomes to surgical interventions for management of corneal opacification in children is further compromised by the pre-existing amblyopia apart from the concerns of refractive outcome of the graft. Graft rejection, graft infection, amblyopia, and glaucoma continue to be serious concerns. In recent years both anterior and posterior lamellar keratoplasty techniques are being increasingly performed in pediatric eyes, which offer advantages in the form of lower risk of graft rejection. The timing of surgery, careful case selection, cautious intraoperative approach, and optimal postoperative management can improve the anatomical and functional outcome in difficult cases.

Dry eye disease and ocular surface characteristics in patients with keratoconus

PURPOSE

The purpose of this study is to investigate the ocular surface alterations in patients with mild or severe keratoconus (KC).

METHODS

A total of 80 participants were included in the study. The corneal topography was performed on each participant using Pentacam and the grouping was done accordingly. The patients with Kmax ≥52.0 D (severe KC) were considered Group 1 (n = 28), the patients with Kmax ≥47.2 and <52.0 D (mild KC) were considered Group 2 (n = 30). Healthy control participants with Kmax <47.2 D were considered Group 3 (n = 22). Tear breakup time (TBUT), Schirmer-I test, ocular surface disease index (OSDI) questionnaire, and conjunctival impression cytology (CIC) were evaluated among the groups.

RESULTS

The mean values of TBUT and Schirmer-I test were significantly lower (P = 0.012, P = 0.012) and the mean scores of OSDI and CIC were significantly higher (P = 0.006, P < 0.001) in Group 1 and Group 2 than in Group 3. The mean values of TBUT and Schirmer-I test were lower and the mean scores of OSDI and CIC were higher in Group 1 than in Group 2 but the differences were insignificant (P > 0.05 for all).

CONCLUSION

These results indicated that the tests associated with dry eye disease are correlated with KC. Tear film alterations and goblet cell loss are higher in severe KC.

Performances of Corneal Topography and Tomography in the Diagnosis of Subclinical and Clinical Keratoconus

Aim

The purpose of the study was to assess the efficacy of topographical and tomographical indices given by the Pentacam (pachymetric, tomopetric, and aberometric) in clinical and subclinical keratoconus (KCN) diagnosis.

Material and Methods

In this observational analytic retrospective study, patients with abnormal findings in topography and tomography maps but with no signs on clinical examination (subclinical KCN group, sKCN), patients with clinical keratoconus (KCN group), and healthy subjects (Control group) were evaluated.

Results

The KCN group proved significantly different (p < 0.001) values of the investigated parameters than the Control group. Eleven out of 28 investigated parameters proved significantly different in the sKCN group compared to controls (p < 0.001). Two topographic measurements, namely I-S (cut-off = 1.435, a large value indicates the presence of KCN) and CCT (cut-off = 537, a small value indicates the presence of KCN), showed AUCs equal to 1 [0.999 to 1]. Six other Pentacam measurements, including Back maximum keratometry (Back Kmax) proved to be excellent parameters for case-finding and screening. In distinguishing sKCN from normal eyes, Pentacam index of vertical asymmetry (IVA), inferior-superior difference (I-S) value, thinnest point (TP), Belin Ambrosio Enhanced Ectasia Display (BAD_D) and root mean square total (RMS total) performed best.

Conclusions

In distinguishing sKCN from normal eyes, Back Kmax, IVA, I-S, and RMS total values demonstrated higher accuracy and utility. Six indices, namely ISV, IVA, KISA, PRC, RMS-HOA, and Back Kmax demonstrate excellent utility in case-finding and screening for clinical KCN.

Pediatric Crosslinking: Current Protocols and Approach

Keratoconus (KC) is likely to be more aggressive in the pediatric population, with a higher risk of progression and visual loss. Several techniques have been proposed for corneal crosslinking (CXL) so far. The standard CXL (SCXL) technique, or the Dresden Protocol, originally developed by Wollensak et al., has been shown to be safe and effective in the pediatric KC group. With similar efficacy to the conventional method, the accelerated CXL (ACXL) protocols proposed a reduced UVA exposure time by increasing the intensity of UVA irradiation. Transepithelial CXL (TCXL), considered an "epithelium-on" method, emerged as a strategy to improve safety and reduce postoperative complications and discomfort. For thinner corneas, we can highlight the use of hypoosmolar riboflavin and new studies, such as contact lens-assisted CXL (CACXL), the epithelial-island CXL (EI-CXL), and the Sub400 protocol. In addition to the different protocols used, another factor that changes CXL results is the type of carrier used: dextran-based or hydroxypropyl methylcellulose-based (HPMC) riboflavin solutions. There are several ways to perform a CXL surgery, and it is still unclear which method is the safest and most effective in the pediatric group. This review of the literature in English, available in PubMed, provides an update on corneal CXL in the pediatric KC group, exploring the data on the techniques currently used and under investigation, including their advantages, efficacy, safety profiles, risks, and cost analyses.

Pathogenesis of keratoconus: NRF2-antioxidant, extracellular matrix and cellular dysfunctions

Keratoconus (KC) is a degenerative disease associated with cell and extracellular matrix (ECM) loss that causes gradual thinning and steepening of the cornea and loss of vision. Collagen cross linking with ultraviolet light treatment can strengthen the ECM and delay weakening of the cornea, but severe cases require corneal transplantation. KC is multifactorial and multigenic, but its pathophysiology is still an enigma. Multiple approaches are being pursued to elucidate the molecular changes that underlie the corneal phenotype to identify relevant genes for tailored candidate searches and to develop potential biomarkers and targets for therapeutic interventions. Recent proteomic and transcriptomic studies suggest dysregulations in oxidative stress, NRF2-regulated antioxidant programs, WNT-signaling, TGF-β, ECM and matrix metalloproteinases. This review aims to provide a broad update on the transcriptomic and proteomic studies of KC with a focus on findings that relate to oxidative stress, and dysregulations in cellular and extracellular matrix functions.

Evaluating the association between MPDZ-NF1B rs1324183 and keratoconus in an independent northwestern Chinese population

Background

Keratoconus (KC) is a complex, non-inflammatory corneal degenerative disease. Although numerous studies have analyzed the correlation of SNP rs1324183, which located in MPDZ-NF1B gene, and KC in different populations, only few findings were repeated. In this study, to evaluate the association between rs1324183 and KC in a new independent Chinese population, we performed a replication study of the significantly associated rs1324183.

Methods

In total of 114 unrelated KC patients and 88 unrelated controls were recruited from Ningxia, China. We detected the genotypes and alleles of rs1324183 using PCR technology and Sanger sequencing and also analyzed the association between this locus and KC, its clinical parameters by statistical methods.

Results

The frequency of genotype AA (11, 9.6%) and genotypes containing allele A (47, 41.2%) of rs1324183 in KC were both higher than those of the control group. And genotype AA of rs1324183 conferred a higher risk of KC (OR > 1). Moreover, corneal parameter Belin/Ambrósio enhanced ectasia display final D value (BAD-D) had significant correlation (p = 0.002) with AA genotype of rs1324183 in KC.

Conclusions

Our replication study indicates that the results of rs1324183 associated with KC in our population is robust and further better illustrates the significance of BAD-D as a diagnostic indicator for KC. rs1324183 should be considered as the first genetic mark of KC risk in its future diagnosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02359-1.

Risk factors and severity of keratoconus on the East Coast of China

PURPOSE

This study aims to investigate the characteristics, potential risk factors and associated severity of keratoconus on the east coast of China.

METHODS

In this case-control study, patients diagnosed with keratoconus were invited to fill in the online electronic questionnaire designed with the help of the App named WenJuanXing. Several questions like, sex, age of diagnosis and eye care habits were administered to each subject through this e-questionnaire. Corneal topographies at diagnosis taken from Pentacam were also collected.

RESULTS

Totally 391 Chinese keratoconus outpatients were enrolled in this study, among which 159 patients were newly diagnosed. Only three patients (0.77%) had a positive family history of keratoconus. Atopy could be identified in 66.0% of our patients. A total of 357 patients (91.3%) mentioned the habit of eye rubbing, with 191 patients (48.8%) rubbing their eyes frequently. Patients with younger age at onset (p = 0.005), male sex (p = 0.042), frequent eye rubbing (p = 0.003) and smoke (p = 0.002) were found significantly associated with increased risk of acute hydrops. In newly diagnosed patients, 79.9% had the maximum keratometry (Kmax) more than 52D, with males and patients aged 21-30 being even more serious (p = 0.009; p = 0.005). Besides, in patients aged over 21, frequent eye rubbing was significantly associated with steeper Kmax and more severe astigmatism (all p < 0.05).

CONCLUSION

Our results suggest that frequent eye rubbing is closely related to the severity of keratoconus in Chinese patients. Chinese keratoconus patients always had much serious disease condition at the time of diagnosis. Thus, increasing the publicity of keratoconus and advocating appropriate eye care habits are needed urgently in China.

REGISTRATION

The research was retrospectively registered, and the trial registration number is ChiCTR1900021273, and the registration date is 2019/02/09.

Keratoconus: An updated review

Keratoconus is a bilateral and asymmetric disease which results in progressive thinning and steeping of the cornea leading to irregular astigmatism and decreased visual acuity. Traditionally, the condition has been described as a noninflammatory disease; however, more recently it has been associated with ocular inflammation. Keratoconus normally develops in the second and third decades of life and progresses until the fourth decade. The condition affects all ethnicities and both sexes. The prevalence and incidence rates of keratoconus have been estimated to be between 0.2 and 4,790 per 100,000 persons and 1.5 and 25 cases per 100,000 persons/year, respectively, with highest rates typically occurring in 20- to 30-year-olds and Middle Eastern and Asian ethnicities. Progressive stromal thinning, rupture of the anterior limiting membrane, and subsequent ectasia of the central/paracentral cornea are the most commonly observed histopathological findings. A family history of keratoconus, eye rubbing, eczema, asthma, and allergy are risk factors for developing keratoconus. Detecting keratoconus in its earliest stages remains a challenge. Corneal topography is the primary diagnostic tool for keratoconus detection. In incipient cases, however, the use of a single parameter to diagnose keratoconus is insufficient, and in addition to corneal topography, corneal pachymetry and higher order aberration data are now commonly used. Keratoconus severity and progression may be classified based on morphological features and disease evolution, ocular signs, and index-based systems. Keratoconus treatment varies depending on disease severity and progression. Mild cases are typically treated with spectacles, moderate cases with contact lenses, while severe cases that cannot be managed with scleral contact lenses may require corneal surgery. Mild to moderate cases of progressive keratoconus may also be treated surgically, most commonly with corneal cross-linking. This article provides an updated review on the definition, epidemiology, histopathology, aetiology and pathogenesis, clinical features, detection, classification, and management and treatment strategies for keratoconus.

Increased lacrimal inflammatory mediators in patients with keratoconus

Purpose

This study aimed to characterize the tear film immunologic profile in keratoconus (KC) patients compared with healthy individuals (control group) and to investigate the correlation between the tear film immunologic profile and atopy, disease severity, and disease status over time.

Methods

The study involved 30 KC patients and 18 healthy individuals. Tear collection was obtained using microcapillary tubes. Tear film levels of fractalkine, granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon (IFN)-γ, interleukin (IL)-1β, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13, IL-17A, IL-21, IL-23, interferon-inducible T-cell alpha chemoattractant (ITAC), macrophage inflammatory protein-1 alpha (MIP-1α), MIP-1β, MIP-3α, and tumor necrosis factor (TNF)-α were detected. Keratometric measurements and topographic patterns were used to diagnose and define disease progression. Tear immunologic profiles were compared, emphasizing the presence or absence of ocular allergy. Correlations between the cytokine profile, disease severity, and disease status were also analyzed longitudinally in the KC patients.

Results

Lacrimal cytokine concentrations were higher in the KC patients than they were in the controls in 14 of 21 cytokines analyzed. IL-6 was the most relevant cytokine found in KC patients, especially when associated with ocular allergy. There was no correlation between KC progression and the level of inflammatory cytokines when analyzed longitudinally. KC severity correlated with IL-6 concentration, where the more severe KC presented a higher IL-6 concentration in tears.

Conclusions

Inflammatory activity seems to be involved in the pathogenesis of KC. Out of 21 cytokines, 14 were more concentrated in the tears of KC patients than healthy subjects. IL-6 was significantly higher in KC patients' tears and was related to disease severity. Disease progression did not correlate with cytokine levels when analyzed longitudinally.

Association of IL4 rs2070874, FoxP3 rs3761548 Polymorphisms with Keratoconus in Algeria

Purpose

The aim of this case–control study was to determine the impact of environmental factors on the predisposition to develop keratoconus in a sample of Western Algerian population. Subsequently, we were interested in the implication of two single nucleotide polymorphisms (SNPs) IL4 rs2070874 and FOXP3 rs3761548, previously described as contributing to the occurrence of allergy, in the development of keratoconus.

Methods

The study included 70 unrelated KC cases and 70 controls originating from Western Algeria. DNA genotyping was done using predesigned probe-based allelic discrimination TaqManⓇ assays. Allele and genotype frequencies were compared between the cases and controls by Chi-square test and odds ratios with 95% confidence intervals.

Results

A significant association between risk factors such as family history, atopy, eye rubbing, and the development of keratoconus was found in our sample. Smoking would provide a protective effect against the pathology. No statistically significant differences were found in the allele and genotype frequencies between cases and controls neither for IL4 rs2070874 nor for FOXP3 rs3761548.

Conclusion

Our study provides, for the first time, a clear demonstration of the absence of association of the allergy-associated IL4 and FOXP3 polymorphisms with KC in a sample from Western Algerian population.

Age and sex-specific differences in interleukin 4, interferon gamma, macrophage migration inhibitory factor, and vascular endothelial growth factor levels in the tears of healthy subjects

OBJECTIVE

To investigate the physiological profile of pro-inflammatory and anti-inflammatory cytokines in tears produced by epithelial cells under the effect of endogenous and exogenous biological factors. Knowing the physiological cytokine profile in tears with its biological characteristics including sex- and age-specific effects is fundamental when tears are analyzed for diagnostic or prognostic purposes in eye diseases.

METHODS

Tear samples were collected from right eye of 45 healthy volunteers (24 males, 21 females) by 5 μl microcapillary tube. Cytokines interleukin 1β, interleukin 10, interleukin 4, interferon gamma, macrophage migration inhibitory factor, and vascular endothelial growth factor were quantified by multiplex Bio-Plex system.

RESULTS

The production of macrophage migration inhibitory factor cytokine by epithelial cells on the ocular surface is higher in males compared to females (p = 0.05); actually, most of female tear samples present with undetectable macrophage migration inhibitory factor levels. Our results show the negative correlations between the age and concentrations of interleukin 4 (p < 0.01) and interferon gamma (p < 0.01) in tears, respectively, and positive associations of vascular endothelial growth factor levels with the age above 45 years (p < 0.05).

CONCLUSIONS

Data in this study indicate that age and sex may affect the physiological levels of cytokines in tears. Consequently, the impacts of biological factors need to be recognized and taken into consideration before the levels of cytokines in patients' tears are analyzed for medical reasons. Concentrations of interleukin 1β and interleukin 10 cytokines, however, are very low in healthy tears and do not seem to be influenced by studied biological factors; therefore, they meet the requirements for analytes suitable for medical diagnostic and prognostic purposes.

Interleukin-6 and tumor necrosis factor-α levels in tear film of Keratoconus patients

Background:

It is hypothesized that increased inflammatory markers in keratoconus (KC) may be one of the causes of corneal damage. The aim of our study was to the measurement of tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL)-6 in tear of patients with KC and investigate their relationship with the severity of KC.

Materials and Methods:

The current study was performed on KC patients and healthy controls with a case-control setting. Tear levels of TNF-α and IL-6 were measured after collecting the tears from the tear lake using a filter paper via Schirmer I method without anesthesia.

Results:

Eighty-one KC patients (mean age 29.45 ± 5.06 years) and 85 controls (mean age 28.01 ± 5.14 years) were enrolled. The mean levels of IL-6 and TNF-α were 26.77 ± 8.16, and 34.58 ± 9.82 pg/ml in the healthy group and 103.22 ± 51.94, and 183.76 ± 54.61 pg/ml in the KC group, respectively (P < 0.001). There was a significant relationship between the severity of the KC and the mean levels of IL-6 TNF-α in the case group (P < 0.001).

Conclusion:

Our results indicated that the mean levels of IL-6 and TNF-α are significantly higher in KC than the healthy group, and the disease severity was significantly associated with TNF-α and IL-6.

Potential underlying genetic associations between keratoconus and diabetes mellitus

Background Keratoconus (KC) is the most common ectatic corneal disease, characterized by significantly localized thinning of the corneal stroma. Genetic, environmental, hormonal, and metabolic factors contribute to the pathogenesis of KC. Additionally, multiple comorbidities, such as diabetes mellitus, may affect the risk of KC. Main Body Patients with diabetes mellitus (DM) have been reported to have lower risk of developing KC by way of increased endogenous collagen crosslinking in response to chronic hyperglycemia. However, this remains a debated topic as other studies have suggested either a positive association or no association between DM and KC. To gain further insight into the underlying genetic components of these two diseases, we reviewed candidate genes associated with KC and central corneal thickness in the literature. We then explored how these genes may be regulated similarly or differentially under hyperglycemic conditions and the role they play in the systemic complications associated with DM. Conclusion Our comprehensive review of potential genetic factors underlying KC and DM provides a direction for future studies to further determine the genetic etiology of KC and how it is influenced by systemic diseases such as diabetes.

Different mRNA expression patterns in keratoglobus and pellucid marginal degeneration keratocytes

PURPOSE

Alike keratoconus (KC), keratoglobus (KG) and pellucid marginal degeneration (PMD) belong to ectatic corneal diseases. While there are numerous studies on keratoconus pathophysiology, there is no exact knowledge on genetic and pathophysiological background of KG and PMD, so far. It is not yet clarified, whether KG and PMD are independent clinical entities or represent different stages of the same disease. Our purpose was to investigate key parameters concerning collagen synthesis, intracellular LOX expression and inflammation in corneal stromal cells of KG and PMD subjects, in vitro.

METHODS

Normal human keratocytes of corneas from the LIONS Cornea Bank Saar-Lor-Lux, Trier/Westpfalz and human keratocytes of KG and PMD patients were isolated and cultured as keratocytes. To examine Collagen I and V (Col I, Col V), heat shock protein 47 (Hsp47), Lysyl Oxidase (LOX), nuclear factor kappa B (NF-κB) mRNA and protein expression in all cell types, quantitative PCR and Western blot analysis has been performed.

RESULTS

Col5A1 mRNA expression was significantly lower in KG and PMD keratocytes and LOX mRNA expression was significantly higher in KG-keratocytes, compared to controls. Col1A1, Hsp47 and NF-κB mRNA expression and the analyzed protein expressions did not differ from controls, in KG or PMD.

CONCLUSIONS

Col5A1 mRNA expression is decreased in KG and PMD and LOX mRNA expression is increased in KG. Therefore, the pathophysiology of KG and PMD differs from KC and these seem to be from KC independent entities. The explanation of the peripheral corneal thinning in KG and PMD must be investigated in further studies.

Keratoconus patients exhibit a distinct ocular surface immune cell and inflammatory profile

Inflammatory factors have been considered to contribute to keratoconus (KC) pathogenesis. This study aims to determine the immune cells subsets and soluble inflammatory factor profile on the ocular surface of KC patients. 32 KC subjects (51 eyes) across different grades of severity and 15 healthy controls (23 eyes) were included in the study. Keratometry and pachymetry measurements were recorded. Ocular surface immune cells (collected by ocular surface wash) immunophenotyped using flow cytometry include leukocytes, neutrophils, macrophages, natural killer (NK) cells, pan-T cells, gamma delta T (γδT) cells and NKT cells. Tear fluid collected using Schirmer's strip was used to measure 50 soluble factors by multiplex ELISA. Proportions of activated neutrophils, NK cells and γδT cells were significantly increased in KC patients. Significantly higher levels of tear fluid IL-1β, IL-6, LIF, IL-17A, TNFα, IFNα/β/γ, EPO, TGFβ1, PDGF-BB, sVCAM, sL-selectin, granzyme-B, perforin, MMP2, sFasL and IgE, along with significantly lower levels of IL-1α and IL-9 were observed in KC patients. Alterations observed in few of the immuno-inflammatory parameters correlated with grades of disease, allergy, eye rubbing and keratometry or pachymetry measurements. The observation implies a distinct immuno-inflammatory component in KC pathogenesis and its potential as an additional therapeutic target in KC management.

Tear Levels of Inflammatory Cytokines in Keratoconus: A Meta-Analysis of Case-Control and Cross-Sectional Studies

Purpose

To assess the tear levels of inflammatory cytokines in patients with keratoconus (KC).

Design

Systemic review and meta-analysis.

Methods

The following electronic databases and search engine were searched: PubMed, EMBASE, Web of Science, and Google Scholar. A systematic search of all relevant studies published through January 2021 was conducted, and the standardized mean difference (SMD) and 95% confidence interval (CI) of cytokine levels were calculated to estimate the pooled effects. Sensitivity analysis, subgroup analysis, and metaregression were applied to explore the sources of heterogeneity.

Results

A total of 7 studies with 374 participants (374 eyes) from clinical studies were included. The tear levels of interleukin-1 beta (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α) were significantly increased in KC compared with normal controls. The SMD of IL-1β was 1.93 (95% CI 0.22 to 3.65, P = 0.03). The SMD of IL-6 was 1.22 (95% CI 0.59 to 1.84, P < 0.001). The SMD of TNF-α was 1.75 (95% CI 0.66 to 2.83, P = 0.002). There was no significant difference between the two groups on interleukin-4 (IL-4) and interleukin-10 (IL-10). The SMD for IL-4 was 2.36 (95% CI -0.28 to 5.00, P = 0.08) and for IL-10 was 0.30 (95% CI -1.29 to 1.89, P = 0.71). Meta-regression analysis indicated that the heterogeneity maybe significantly correlated with the method of detection, the different ages, and the source of population.

Conclusions

Our meta-analysis demonstrated that proinflammatory cytokines IL-1β, IL-6, and TNF-α were increased, indicating that cytokine profile changed in KC tears and inflammation may play an important role in the pathogenesis and development of KC.

Assessing the role of systemic inflammation in the etiopathogenesis of advanced stage keratoconus

PURPOSE

It was aimed to compare the levels of inflammation-related parameters, such as neutrophil/lymphocyte ratio (NLR) and platelet/lymphocyte ratio (PLR), in patients with advanced keratoconus (KC) and healthy controls. Also, we evaluated the relationships between these parameters and several corneal topography values used in the KC diagnostic index.

METHODS

Forty patients with advanced and 40 healthy volunteers were included in this study. In the KC group, 20 patients were nonprogressive KC and 20 patients were progressive KC. In all participating individuals, we evaluated detailed ophthalmologic examination findings and complete blood count data, while corneal topographic measurements were also recorded in patients with KC.

RESULTS

The mean NLR value was 2.3 ± 1.19 in the progressive KC group; nonprogressive KC values were 1.99 ± 1.69 and 1.81 ± 0.72 in the control group. Mean PLR value was 113.24 ± 48.44 in the progressive KC group, nonprogressive KC values were 96.47 ± 31.04 and 104.09 ± 35.14 in the control group. No statistically significant difference was found between patients with progressive KC, nonprogressive KC, and healthy volunteers in terms of mean NLR and PLR values (P > 0.05). NLR values were found to demonstrate significant positive correlations with the corneal topography parameters, Symmetry Index front (r = 0.278, P = 0.025), KC Vertex front (r = 0.247, P = 0.048), and Baiocchi Calossi Versaci front (r = 0.273, P = 0.028); there was no significant relationship between corneal topography parameters and PLR values.

CONCLUSION

Although there was no significant difference between the progressive KC, nonprogressive KC, and control groups in inflammation parameters such as NLR and PLR, a positive correlation was observed between the NLR value and some corneal topography findings used in the diagnosis of KC. The role of inflammation in the etiology of KC can be better understood by clinical studies and laboratory tests conducted with prospective studies involving a higher number of patients.

Influence of interleukin 17 A and 17 F polymorphisms in keratoconus

BACKGROUND

Until a few years ago, keratoconus was defined as a noninflammatory degenerative disease. However, recent studies have shown that the altered balance between inflammatory cytokines, proteases, and protease inhibitors, as well as free radicals and oxidants, have a crucial role in the pathogenesis of this disease. The aim of this study is to investigate whether interleukin 17 A G197A (rs2275913) and interleukin 17 F T7488C (rs763780) polymorphisms are associated with keratoconus in patients from a population of the northwestern region of the State of São Paulo, Brazil.

METHODS AND RESULTS

35 patients and 61 controls were enrolled. Genotyping of interleukin 17 A G197A and interleukin 17 F T7488C polymorphisms was carried out using the polymerase chain reaction-restriction fragment length polymorphism technique. Statistical analyses were conducted using the chi-square test, and an odds ratio with a 95% confidence interval was also calculated to evaluate the association between polymorphisms and disease. Evaluating interleukin 17 F T7488C, we found that the TT genotype is associated as a risk factor for keratoconus (P = 0.04; OR = 3.01; CI 1.11-8.14). As for evaluating interleukin 17 A G197A, the allele and genotype frequencies between patients and controls were compared and no statistically significant differences were found.

CONCLUSIONS

Our data showed that the interleukin 17 F T7488C polymorphisms may exert an influence in keratoconus.

Assessment of ganglion cell complex, macular thickness, and optic disc parameters in keratoconus patients

PURPOSE:

Keratoconus (KC) is bilateral noninflammatory corneal disorder characterized by progressive corneal thinning, protrusion, and scarring. The purpose of this study was to evaluate ganglion cell complex(GCC), macula thickness(MT) and optic head disc parameters in keratoconus patients.

METHODS:

A hospital based prospective clinical case series was performed in Inonu University School of Medicine. 52 eyes of 52 keratoconus patients and 50 eyes of 50 normal patients were enrolled.

RESULTS:

There is no statistically significant in MT between groups. GCC in nasal superior, temporal superior and temporal inferior 9 mm from macula were found statistically significant decrease in keratoconus group (p<0,05). In optic disc analysis fifth and the eleventh clock-hour quadrants of peripapiller retina nerve fiber layer and cup area ratio were found statistically significant decrease in keratoconic eyes (p<0,05).

CONCLUSION:

We thought that structural retinal changes seem in keratoconus eyes; keratoconus pathogenesis may affect not only cornea but also retina and optic nerve head.

Systemic immune-inflammation index, neutrophil-to-lymphocyte ratio, and platelet-to-lymphocyte ratio levels are associated with keratoconus

Purpose:

The aim of this study was to assess the systemic immune-inflammation index (SII) levels, neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR) in patients with keratoconus (KC).

Methods:

A total of 42 patients with KC (KC group) and 42 age- and sex-matched healthy subjects (control group) were included into this cross sectional study. Complete blood count parameters were assayed. SII, NLR, red cell distribution width (RDW), and PLR values were calculated. The SII value was calculated as follows: platelet count × (neutrophil/lymphocyte).

Results:

SII, NLR, RDW, and PLR values were significantly higher in KC group compared to control group [709 ± 236 vs. 418 ± 117 (P < 0.001), 2.5 ± 0.8 vs. 1.76 ± 0.3 (P < 0.001), 14.3 ± 1.6% vs. 12.9 ± 0.54% (P < 0.001), and 143 ± 36 vs. 106 ± 23 (P < 0.001), respectively]. Using the receiver operating characteristics (ROC) curve analysis to predict KC, the highest area under the curve (AUC) was determined SII (0.846 for SII, 0.778 for NLR, and 0.796 for PLR).

Conclusion:

SII, NLR, RDW, and PLR levels were significantly increased in patients with KC. This study supports the idea that several inflammatory pathways may play important role in the pathogenesis of this disorder. SII may be much better marker than NLR and PLR for predicting the inflammatory status of the disease.

Association between chronic kidney disease and the most common corneal ectasia disease (keratoconus): a nationwide cohort study

BACKGROUND

Both keratoconus (KCN) and chronic kidney disease (CKD) are multifactorial conditions with multiple aetiologies and share several common pathophysiologies. However, the few studies that have described the relationship between KCN and CKD are limited to case reports and small case series. This study aimed to evaluate the association between KCN and CKD.

METHODS

The study cohort included 4,609 new-onset keratoconus patients ≥ 12 years identified by the International Classification of Diseases, Ninth Revision, Clinical Modification, code 371.6 and recruited between 2004 and 2011 from the Taiwan National Health Insurance Research Database. The age-, sex-, and comorbidity-matched control group included 27,654 non-KCN patients, selected from the Taiwan Longitudinal Health Insurance Database, 2000. Information for each patient was collected and tracked from the index date until December 2013. The incidence and risk of CKD were compared between the two groups. The adjusted hazard ratios (HRs) for CKD were calculated with Cox proportional hazard regression analysis. Kaplan-Meier analysis was used to calculate the cumulative CKD incidence rate.

RESULTS

The incidence rate of CKD was 1.36 times higher in KCN patients than in controls without statistically significant difference (95 % confidence interval [CI] = 0.99-1.86, p = 0.06). In total, 29 male KCN patients and 90 male controls developed CKD during the follow-up period. The incidence rate of CKD was 1.92 times (95 % [CI] = 1.26-2.91; p = 0.002) higher in male KCN patients than in controls. After adjusting for potential confounders, including age, hypertension, hyperlipidaemia, and diabetes mellitus, male KCN patients were 1.75 times (adjusted HR = 1.75, 95 % [CI] = 1.14-2.68, p < 0.05) more likely to develop CKD.

CONCLUSIONS

We found that male KCN patients have an increased risk of CKD. Therefore, it is recommended that male KCN patients should be aware of CKD.