Multi-dataset identification of innovative feature genes and molecular mechanisms in keratoconus.

This study aimed to identify feature genes and explore the molecular mechanisms of keratoconus (KC). We downloaded data files from NCBI GEO public database. The Limma package was used for differential expression analysis of gene profiles. Lasso regression was used to identify the feature genes. The CIBERSORT algorithm was used to infer the proportion of immune-infiltrating cells and analyse the correlation between gene expression levels and immune cells. Related transcription factors and miRNAs of key genes were predicted using the Cistrome DB and Mircode databases. Analysis of expression differences in disease genes was based on the GeneCards database. The CMap was used to analyse targeted therapeutic drugs. IHC was performed to verify the expression levels of ATOH7 and MYRF in corneas. Exactly 593 upregulated and 473 downregulated genes were identified. Lasso regression analysis identified ATOH7, DBNDD1, RNF217-AS1, ARL11, MYRF and SNORA74B as feature genes for KC. All key genes were correlated with immune infiltration and the levels of activated memory CD4+ T cells and plasma cells were significantly increased. miRNA, IRF and STAT families were correlated to feature genes. The expression levels of key genes were significantly correlated to KC-related genes. Entinostat, ochratoxin-a, diphencyprone and GSK-3-inhibitor-II were predicted as potential KC medications. The expression of MYRF was significantly higher in the KC samples, contrary to the expression of ATOH7. KC is related to both immune infiltration and genetic factors. MYRF and ATOH7 were newly identified and verified feature genes of KC.

Static magnetic field effects on the secondary structure and elasticity of collagen molecules; a possible biophysical approach to treat keratoconus.

Type I collagen is among the major extracellular proteins that play a significant role in the maintenance of the cornea's structural integrity and is essential in cell adhesion, differentiation, growth, and integrity. Here, we investigated the effect of 300 mT Static Magnetic Field (300 mT SMF) on the structure and molecular properties of acid-solubilized collagens (ASC) isolated from the rat tail tendon. The SMF effects at molecular and atomic levels were investigated by various biophysical approaches like Circular Dichroism Spectropolarimetery (CD), Fourier Transform Infrared Spectroscopy (FTIR), Zetasizer light Scattering, and Rheological assay. Exposure of isolated type I collagen to 300 mT SMF retained its triple helix. The elasticity of collagen molecules and the keratoconus (KCN) cornea treated with SMF decreased significantly after 5 min and slightly after 10, 15, and 20 min of treatments. The exposure to 300 mT SMF shifted the Amid I bond random coil to antiparallel wave number from 1647 to 1631 cm-1. The pH of the 300 mT SMF treated collagen solution increased by about 25 %. The treatment of the KCN corneas with 300 mT SMF decreased their elasticity significantly. The promising results of the effects of 300 mT SMF on the collagen molecules and KCN cornea propose a novel biophysical approach capable of manipulating the collagen's elasticity, surface charges, electrostatic interactions, cross binding, network formation and fine structure. Therefore, SMF treatment may be considered as a novel non-invasive, direct, non-chemical and fast therapeutic and manipulative means to treat KCN cornea where the deviated physico-chemical status of collagen molecules cause deformation.

Subclinical Keratoconus Detection and Characterization Using Motion-Tracking Brillouin Microscopy.

PURPOSE: To characterize focal biomechanical alterations in subclinical keratoconus (SKC) using motion-tracking (MT) Brillouin microscopy and evaluate the ability of MT Brillouin metrics to differentiate eyes with SKC from normal control eyes. DESIGN: Prospective cross-sectional study. PARTICIPANTS: Thirty eyes from 30 patients were evaluated, including 15 eyes from 15 bilaterally normal patients and 15 eyes with SKC from 15 patients. METHODS: All patients underwent Scheimpflug tomography and MT Brillouin microscopy using a custom-built device. Mean and minimum MT Brillouin values within the anterior plateau region and anterior 150 µm were generated. Scheimpflug metrics evaluated included inferior-superior (IS) value, maximum keratometry (Kmax), thinnest corneal thickness, asymmetry indices, Belin/Ambrosio display total deviation, and Ambrosio relational thickness. Receiver operating characteristic (ROC) curves were generated for all Scheimpflug and MT Brillouin metrics evaluated to determine the area under the ROC curve (AUC), sensitivity, and specificity for each variable. MAIN OUTCOME MEASURES: Discriminative performance based on AUC, sensitivity, and specificity. RESULTS: No significant differences were found between groups for age, sex, manifest refraction spherical equivalent, corrected distance visual acuity, Kmax, or KISA% index. Among Scheimpflug metrics, significant differences were found between groups for thinnest corneal thickness (556 µm vs. 522 µm; P < 0.001), IS value (0.29 diopter [D] vs. 1.05 D; P < 0.001), index of vertical asymmetry (IVA; 0.10 vs. 0.19; P < 0.001), and keratoconus index (1.01 vs. 1.05; P < 0.001), and no significant differences were found for any other Scheimpflug metric. Among MT Brillouin metrics, clear differences were found between control eyes and eyes with SKC for mean plateau (5.71 GHz vs. 5.68 GHz; P < 0.0001), minimum plateau (5.69 GHz vs. 5.65 GHz; P < 0.0001), mean anterior 150 µm (5.72 GHz vs. 5.68 GHz; P < 0.0001), and minimum anterior 150 µm (5.70 GHz vs. 5.66 GHz; P < 0.001). All MT Brillouin plateau and anterior 150 µm mean and minimum metrics fully differentiated groups (AUC, 1.0 for each), whereas the best performing Scheimpflug metrics were keratoconus index (AUC, 0.91), IS value (AUC, 0.89), and IVA (AUC, 0.88). CONCLUSIONS: Motion-tracking Brillouin microscopy metrics effectively characterize focal corneal biomechanical alterations in eyes with SKC and clearly differentiated these eyes from control eyes, including eyes that were not differentiated accurately using Scheimpflug metrics. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Advanced Corneal Imaging in Keratoconus: A Report by the American Academy of Ophthalmology.

PURPOSE: To review the published literature on the diagnostic capabilities of the newest generation of corneal imaging devices for the identification of keratoconus. METHODS: Corneal imaging devices studied included tomographic platforms (Scheimpflug photography, OCT) and functional biomechanical devices (imaging an air impulse on the cornea). A literature search in the PubMed database for English language studies was last conducted in February 2023. The search yielded 469 citations, which were reviewed in abstract form. Of these, 147 were relevant to the assessment objectives and underwent full-text review. Forty-five articles met the criteria for inclusion and were assigned a level of evidence rating by the panel methodologist. Twenty-six articles were rated level II, and 19 articles were rated level III. There were no level I evidence studies of corneal imaging for the diagnosis of keratoconus found in the literature. To provide a common cross-study outcome measure, diagnostic sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) were extracted. (A perfect diagnostic test that identifies all cases properly has an AUC of 1.0.) RESULTS: For the detection of keratoconus, sensitivities for all devices and parameters (e.g., anterior or posterior corneal curvature, corneal thickness) ranged from 65% to 100%. The majority of studies and parameters had sensitivities greater than 90%. The AUCs ranged from 0.82 to 1.00, with the majority greater than 0.90. Combined indices that integrated multiple parameters had an AUC in the mid-0.90 range. Keratoconus suspect detection performance was lower with AUCs ranging from 0.66 to 0.99, but most devices and parameters had sensitivities less than 90%. CONCLUSIONS: Modern corneal imaging devices provide improved characterization of the cornea and are accurate in detecting keratoconus with high AUCs ranging from 0.82 to 1.00. The detection of keratoconus suspects is less accurate with AUCs ranging from 0.66 to 0.99. Parameters based on single anatomic locations had a wide range of AUCs. Studies with combined indices using more data and parameters consistently reported high AUCs. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Deep Anterior Lamellar Keratoplasty Using Dehydrated versus Standard Organ Culture-Stored Donor Corneas: Prospective Randomized Trial.

PURPOSE: To compare the outcomes of deep anterior lamellar keratoplasty (DALK) using dehydrated versus standard organ culture-stored donor corneas for eyes with keratoconus. DESIGN: Prospective, randomized, single-center trial conducted in Italy. PARTICIPANTS: Adult patients (age ≥ 18 years) with keratoconus scheduled for elective DALK. METHODS: Patients undergoing successful type 1 bubble pneumatic dissection using a standard DALK technique were randomized during surgery to receive either dehydrated (n = 30) or standard organ culture-stored (n = 30) donor corneas. MAIN OUTCOME MEASURES: The primary study outcome was best spectacle-corrected visual acuity (BSCVA) 12 months after surgery. Secondary outcomes were refractive astigmatism (RA), endothelial cell density (ECD), and complication rates. RESULTS: Postoperative BSCVA did not significantly differ between groups at both time points: mean difference at 6 months was 0.030 logarithm of the minimum angle of resolution (logMAR; 95% confidence interval [CI], -0.53 to 0.10 logMAR; P = 0.471) and at 12 months was -0.013 logMAR (95% CI, -0.10 to 0.08 logMAR; P = 0.764). No significant differences between groups were observed in terms of postoperative RA and ECD at all time points. In the first 3 days after DALK, an epithelial defect was present in 10 patients (33%) in the organ culture cornea group and in 29 patients (97%) in the dehydrated cornea group. Complete re-epithelialization was achieved by day 7 in all patients (100%) in both groups. CONCLUSIONS: The study provides evidence that the use of dehydrated corneas is noninferior to the use of standard organ culture donor corneas for DALK. Corneal tissue dehydration represents a viable solution that can allow long-term cornea preservation and avoid wastage of unused corneas. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Trends and Sociodemographic Patterns in Keratoconus Management 2015-2020: An American Academy of Ophthalmology IRIS® Registry Analysis.

PURPOSE: Investigate trends in keratoconus (KCN) treatment patterns and diagnosis age from 2015 to 2020 and evaluate sociodemographic associations with the treatment approach. DESIGN: Retrospective cohort study. PARTICIPANTS: Patients with a new KCN diagnosis from 2015 to 2020 were identified in the Academy IRIS® Registry (Intelligent Research in Sight). METHODS: Associations between sociodemographic factors and treatment were evaluated using multivariable logistic regression. MAIN OUTCOME MEASURES: Outcomes included percentages and rates of each treatment (collagen crosslinking [CXL], keratoplasty, or no procedure) from 2015 to 2020, age at diagnosis during this period, and sociodemographic factors associated with treatment type. RESULTS: A total of 66 199 patients with a new diagnosis of KCN were identified. The percentage of patients undergoing CXL increased from 0.05% in 2015 to 29.5% in 2020 (P = 0.008). The average age (standard deviation) of KCN patients decreased from 44.1 (±16.9) years in 2015 to 39.2 (±16.9) years in 2020 (P < 0.001). In multivariable analyses comparing CXL versus no procedure and keratoplasty versus no procedure, patients undergoing CXL tended to be younger with the odds of having CXL decreasing with increasing age, for example, comparing CXL and no procedure patients, using ages 0-20 years as reference, the odds ratio (OR) (95% confidence interval [CI]) decreased from 0.62 (0.57-0.67; P < 0.0001) for patients aged 21-40 years to 0.03 (0.02-0.04; P < 0.0001) for patients aged > 60 years. Men were more likely than women to have CXL (OR, 1.31; 95% CI, 1.23-1.40; P < 0.0001) and keratoplasty (OR, 1.30; 95% CI, 1.19-1.42; P < 0.0001). Black patients were less likely than White patients to have CXL (OR, 0.70; 95% CI, 0.63-0.77; P < 0.0001) and more likely to have keratoplasty (OR, 2.24; 95% CI, 2.01-2.50; P < 0.0001). Likewise, Hispanic patients had higher odds of CXL (OR, 1.12; 95% CI, 1.00-1.24; P < 0.05) and keratoplasty (OR, 1.29; 95% CI, 1.12-1.50; P < 0.001) compared with non-Hispanic patients. Collagen crosslinking and keratoplasty also varied by region and insurance status. CONCLUSIONS: A significant increase in use of CXL was noted from 2015 to 2020. Sociodemographic differences in treatment among KCN patients may reflect differences in access, use, or care patterns, and future studies should aim to identify strategies to improve access for all patients. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Safety and Efficacy of Epithelium-Off Corneal Collagen Cross-Linking for the Treatment of Corneal Ectasia: A Report by the American Academy of Ophthalmology.

PURPOSE: To review the evidence on the safety and effectiveness of epithelium-off corneal collagen cross-linking (CXL) for the treatment of progressive corneal ectasia. METHODS: A literature search of the PubMed database was most recently conducted in March 2024 with no date restrictions and limited to studies published in English. The search identified 359 citations that were reviewed in abstract form, and 43 of these were reviewed in full text. High-quality randomized clinical trials comparing epithelium-off CXL with conservative treatment in patients who have keratoconus (KCN) and post-refractive surgery ectasia were included. The panel deemed 6 articles to be of sufficient relevance for inclusion, and these were assessed for quality by the panel methodologist; 5 were rated level I, and 1 was rated level II. There were no level III studies. RESULTS: This analysis includes 6 prospective, randomized controlled trials that evaluated the use of epithelium-off CXL to treat progressive KCN (5 studies) and post-laser refractive surgery ectasia (1 study), with a mean postoperative follow-up of 2.4 years (range, 1-5 years). All studies showed a decreased progression rate in treated patients compared with controls. Improvement in the maximum keratometry (Kmax) value, corrected distance visual acuity (CDVA), and uncorrected distance visual acuity (UDVA) was observed in the treatment groups compared with control groups. A decrease in corneal thickness was observed in both groups but was greater in the CXL group. Complications were rare. CONCLUSIONS: Epithelium-off CXL is effective in reducing the progression of KCN and post-laser refractive surgery ectasia in most treated patients with an acceptable safety profile. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found after the references.

Revisiting rabbit models for keratoconus: A long-term study on collagenase-induced disease progression.

Keratoconus (KC) is a degenerative disorder resulting from the degradation of the stromal collagen fibril network in the cornea, leading to its thinning and conical deformation. Various studies have established animal models of KC by using the collagenase type II enzyme to gain a better understanding of the pathogenesis, however, long-term monitoring or follow-up of the models have not been reported so far. This study evaluates the long-term stability of collagenase type II-induced KC in a rabbit model. Six New Zealand rabbits were divided into 4 study groups with 3 eyes per group. The groups were control (group 1), 0.5% proparacaine + 5 min collagenase treatment on day 0 and day 30 (group 2), 0.5% proparacaine + 10 min collagenase treatment on day 0 (group 3) and, mechanical debridement + 2 min collagenase treatment on day 0 (group 4). Inflammation was observed in group 4 till week 10. Significant decrease in the central corneal thickness was observed in group 3 by week 4 (p < 0.001) however, the thickness was regained in the subsequent follow-ups in all the groups. Keratography results showed no changes in Km values but an increased astigmatic power in all groups. Scanning electron microscopy images revealed thinner collagen fibrils arranged in a mesh-like pattern above the uniform layer of the collagen lamellae in the central part of the treated corneas. Similarly, histological staining revealed loosely packed stromal fibrils in the anterior portion of the cornea which corroborates with the immunofluorescent staining results. This study revealed the remodeling of the corneal structure by eight weeks of collagenase treatment. Consequently, the possibility of creating a rabbit keratoconus model induced by collagenase may warrant further consideration.

Impact of a 50bp insertion/deletion polymorphism of the superoxide dismutase-1 on oxidative stress status and risk of keratoconus.

Keratoconus (KC) is characterized by the predominant primary ectatic disease, affecting the cornea, necessitating corneal transplants in some cases. While some loci associated with KC risk have been identified, the understanding of the disease remains limited. Superoxide dismutase (SOD) enzymes play a crucial role in countering the reactive oxygen species and providing protection against oxidative stress (OS). Accordingly, the objective of this study was to investigate a potential association of a 50 nucleotide base pairs (bp) insertion/deletion (I/D) within the SOD1 promoter, and the located 1684 bp upstream of the SOD1 ATG, with KC in the Iranian population. Additionally, an assessment was conducted on SOD activity and the total antioxidant capacity (TAC), as determined by the ferric reducing-antioxidant power assay, along with malondialdehyde (MDA) levels. In this case-control study, genomic DNA was extracted from the blood cells of KC (n = 402) and healthy (n = 331) individuals. The genotype of this gene was determined using the PCR technique. Furthermore, the amount of SOD enzyme activity and the MDA and TAC levels were measured in the serum of the study groups. The (I/I) genotype was present in 84.23%, the (I/D) genotype in 15.06%, and the (D/D) genotype in 0.69% of both groups. A statistically significant relationship was seen between different genotypes and TAC, MDA, and SOD1 activity indices (P < 0.05). Individuals with the D/D genotype exhibited a decrease in total antioxidant capacity, an increase in the amount of MDA, and a decrease in SOD1 enzyme activity (P < 0.05). Moreover, the logistic regression analysis of KC development indicated that elevated levels of MDA increased the risk of KC incidence in the patient group compared to the healthy group, while a higher activity of SOD1 and greater values of TAC decreased the KC risk. The removal of the 50 bp fragment reduced SOD1 activity and elevated OS levels, thereby impacting the oxidant-antioxidant balance. This could potentially play a significant role in individuals afflicted by KC.

Whole-exome sequencing screening for candidate genes and variants associated with primary sporadic keratoconus in Chinese patients.

The pathogenesis of keratoconus (KC) is complex, and genetic factors play an important role. The purpose of this study was to screen and analyse candidate genes and variants in Chinese patients with primary sporadic KC. Whole-exome sequencing (WES) was performed to identify candidate genes and variants in 105 unrelated Chinese patients with primary sporadic KC. Through a series of screening processes, 54 candidate variants in 26 KC candidate genes were identified in 53 KC patients (53/105, 50.5%). These 54 candidate variants included 10 previously identified variants in 9 KC candidate genes and 44 novel variants in 20 KC candidate genes. The previously identified variants occurred in 25.7% (27/105) of patients. Of these, 4 variants (COL6A5, c.5014T > G; CAST, c.1814G > A; ZNF469, c.946G > A; and MPDZ, c.3836A > G) were identified for the first time in Chinese KC patients. The novel variants occurred in 33.3% (35/105) of patients. Of the 26 screened KC candidate genes, 11 KC candidate genes (CAT, COL12A1, FLG, HKDC1, HSPG2, PLOD1, ITGA2, TFAP2B, USH2A, WNT10A, and COL6A5) were found to be potentially pathogenic in Chinese KC patients for the first time. Gene Ontology (GO) biological process (BP) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed on the 26 KC candidate genes using the Database for Annotation, Visualization, and Integrated Discovery (DAVID). The results showed that the KC candidate genes were significantly enriched in biological processes such as collagen fibril organization and extracellular matrix (ECM) organization and in ECM-receptor interaction and protein digestion and absorption pathways. The results further expand the spectrum of KC candidate variants and provide a basis for further KC gene studies.

Circular RNA expression profile identifies potential circulating biomarkers for keratoconus.

Early diagnosis is important for improving the outcomes of keratoconus (KC). Stable expression and a closed-loop structure of circular RNAs (circRNAs) make them ideal for the diagnosis and treatment of diseases. However, the expression pattern and potential function of circRNAs in KC is not studied yet. Hence, this study explored the circRNA expression profile of KC corneas through transcriptome sequencing and circRNA expression profile analysis. The diagnostic potential of blood circRNAs for KC was explored by analysing the circRNAs' expression levels of fifty paired blood samples from patients with KC and normal controls. The results showed that 107 significantly upregulated and 145 significantly downregulated circRNAs (|fold change| ≥ 2.0, p-value <0.05) were identified in KC tissues. Eight top differently expressed circRNAs were further validated in more cornea samples. Among them, five circRNAs expressed in peripheral blood, and four circRNAs (circ_0006156, circ_0006117, circ_0000284 and circ_0001801) showed significant downregulation in KC patients' peripheral blood too. The blood circ_0000284 expression levels of early, moderate, and advanced KC patients both were significantly lower than the controls. The blood circ_0006117 expression levels present a positive correlation with corrected distance visual acuity values, and a negative correlation with back elevation values of KC eyes. Notably, the expression levels of these circRNAs distinguished KC patients from their healthy counterparts, with the area under the curve (AUC) of circ_0000284, circ_0001801, and circ_0006117 being 0.7306, 0.6871 and 0.6701, respectively. Further, the AUC value for five circRNAs under the logistic regression model was 0.8203, indicating that they can function as effective biomarkers for the KC diagnostics. In conclusion, the expression of circRNAs showed a relationship with KC, with four significantly differentially expressed circRNAs demonstrating potential as biomarkers for the disease.

Glycosaminoglycans and collagen fibril distribution at various depths of the corneal stroma of normal and CXL treated rats.

Corneal collagen cross-linking (CXL) is widely used to treat keratoconus and ecstatic corneal disorders. The present studies were carried out to investigate the distribution of glycosaminoglycans (GAGs) and collagen fibril (CF) at different depths of the normal and CXL treated corneal stroma of four week old rats 7 days after standard CXL application. Ten Wistar rats' corneas were used for the study. The epithelium of the cornea from the left eye of each rat was removed and treated with standard CXL application using riboflavin and Ultraviolet-A (UVA) (3 mW/cm2 for 30 min). The cornea from the right eye was used as the control cornea. The cornea was removed from the eye and processed for transmission electron microscopy. A bottom mounted Quemesa camera was used to capture digital images and these images were analysed using iTEM software. In the control cornea, the GAGs area size was not significantly different in the anterior, middle, and posterior stroma. In the CXL treated rats the GAGs area size gradually increased from the anterior to the posterior stroma whereas the spacing between the GAGs gradually decreased. There were very large GAGs present in the posterior stroma of the CXL treated rats. When comparing the control and CXL cornea, the GAGs area in the CXL cornea was significantly higher and inter-GAGs-spacing was smaller than in the control cornea. In the control cornea, the collagen fibrils diameter was higher in the anterior stroma and lowest in the posterior stroma. In the CXL treated cornea, the CF diameter and the interfibrillar spacing gradually decreased from the anterior to the posterior stroma. On comparison between the control and the CXL treated cornea, the interfibrillar spacing was significantly smaller in the CXL treated cornea than the control cornea in the anterior, middle, and posterior stroma but there was no difference in the diameter. The CXL treatment significantly increased the GAGs area and decreased the inter-GAGs-spacing, and inter-CF-spacing. This could be due to the gradual decline in the availability of riboflavin, UVA, and oxygen in the middle and posterior stroma. Further studies are required to investigate the role of keratan sulphate and chondroitin sulphate by using monoclonal antibodies with immunogold technique.

Planar biaxial testing of CXL strengthening effects.

The stiffening effect of corneal crosslinking (CXL) treatment, a therapeutic approach for managing the progression of keratoconus, has been primarily investigated using uniaxial tensile experiments. However, this testing technique has several drawbacks and is unable to measure the mechanical response of cornea under a multiaxial loading state. In this work, we used biaxial mechanical testing method to characterize biomechanical properties of porcine cornea before and after CXL treatment. We also investigated the influence of preconditioning on measured properties and used TEM images to determine microstructural characteristics of the extracellular matrix. The conventional method of CXL treatment was used for crosslinking the porcine cornea. The biaxial experiments were done by an ElectroForce TestBench system at a stretch ratio of 1:1 and a displacement rate of 2 mm/min with and without preconditioning. The experimental measurements showed no significant difference in the mechanical properties of porcine cornea along the nasal temporal (NT) and superior inferior (SI) direction. Furthermore, the CXL therapy significantly enhanced the mechanical properties along both directions without creating anisotropic response. The samples tested with preconditioning showed significantly stiffer response than those tested without preconditioning. The TEM images showed that the CXL therapy did not increase the diameter of collagen fibers but significantly decreased their interfibrillar spacing, consistent with the mechanical property improvement of CXL treated samples.

The Chinese keratoconus (CKC) cohort study.

The Chinese keratoconus (CKC) cohort study is a population-based longitudinal prospective cohort study in the Chinese population involving a clinical database and biobanks. This ongoing study focuses on the prevention of KC progression and is the first to involve the effect of gene‒environment interactions on KC progression. The CKC cohort is hospital-based and dynamic and was established in Zhengzhou, China; KC patients (n = 1114) from a large geographical area were enrolled from January 2019 to June 2023, with a mean age of 22.23 years (6‒57 years). Demographic details, socioeconomic characteristics, lifestyle, disease history, surgical history, family history, and visual and social function data are being collected using questionnaires. General physical examination, eye examination, biological specimen collection, and first-degree relative data were collected and analyzed in the present study. The primary focus of the present study was placed on gene, environment and the effect of gene‒environment interactions on KC progression. The follow-up of the CKC cohort study is expected to include data collection at 3 months, 6 months, and 1 year after the initial examination and then at the annual follow-up examinations. The first follow-up of the CKC cohort study was recorded. A total of 918 patients completed the follow-up by June 1, 2023, with a response rate of 82.40%. Aside from the younger age of patients who were followed up, no significant differences were found between patients who were followed up and patients who were not.

Long-term outcomes of corneal crosslinking.

PURPOSE OF REVIEW: This manuscript summarizes contemporary research from 2018 to 2023 evaluating long-term (≥2 years) outcomes of corneal crosslinking (CXL) for progressive keratoconus (KCN). RECENT FINDINGS: The standard Dresden protocol (SDP) has been utilized clinically since the early 2000 s to treat ectatic disorders, primarily progressive KCN and postrefractive ectasia. Various modifications have since been introduced including accelerated and transepithelial protocols, which are aimed at improving outcomes or reducing complications. This review summarizes data demonstrating that the SDP halts disease progression and improves various visual and topographic indices (UDVA, CDVA, Kmax, K1, K2) up to 13 years postoperatively. Accelerated and transepithelial protocols have been found to be well tolerated alternatives to SDP with similar efficacy profiles. Studies focusing on pediatric populations identified overall higher progression rates after CXL. All protocols reviewed had excellent safety outcomes in adults and children. SUMMARY: Recent studies revealed that SDP successfully stabilizes KCN long term, and a variety of newer protocols are also effective. Pediatric patients may exhibit higher progression rates after CXL. Further research is required to enhance the efficacy and ease of these protocols.

Update on corneal crosslinking for keratoconus and corneal ectasia.

PURPOSE OF REVIEW: To review corneal crosslinking for keratoconus and corneal ectasia, and recent developments in the field. This study will review the mechanism of crosslinking, clinical approaches, current results, and potential future innovations. RECENT FINDINGS: Corneal crosslinking for keratoconus was first approved by U.S. FDA in 2016. Recent studies have confirmed the general long-term efficacy of the procedure in decreasing progression of keratoconus and corneal ectasia. New types of crosslinking protocols, such as transepithelial treatments, are under investigation. In addition, adjunctive procedures have been developed to improve corneal contour and visual function in these patients. SUMMARY: Crosslinking has been found to be well tolerated and effective with the goal of decreasing progression of ectatic corneal diseases, keratoconus and corneal ectasia after refractive surgery. Studies have shown its long-term efficacy. New techniques of crosslinking and adjunctive procedures may further improve treatments and results.

Responsive porous microneedles with riboflavin ocular microinjection capability for facilitating corneal crosslinking.

Riboflavin-5-phosphate (riboflavin) is the most commonly used photosensitizer in corneal crosslinking (CXL); while its efficient delivery into the stroma through the corneal epithelial barrier is challenging. In this paper, we presented novel responsive porous microneedles with ocular microinjection capability to deliver riboflavin controllably inside the cornea to facilitate CXL. The microneedle patch was composed of Poly (N-isopropyl acrylamide) (PNIPAM), graphene oxide (GO), and riboflavin-loaded gelatin. After penetrating the cornea by the stiff and porous gelatin needle tip, the photothermal-responsive characteristic of the PNIPAM/GO hydrogel middle layer could realize the contraction of the gel under the stimulation of near-infrared light, which subsequently could control the release of riboflavin from the backing layer into the cornea stromal site both in vitro and in vivo. Based on the microneedles system, we have demonstrated that this microinjection technique exhibited superior riboflavin delivery capacity and treatment efficacy to the conventional epithelial-on protocol in a rabbit keratoconus model, with benefits including minimal invasiveness and precise administering. Thus, we believe the responsive porous microneedles with riboflavin ocular microinjection capability are promising for clinical corneal crosslinking without epithelial debridement.

Enhanced morphological assessment based on interocular asymmetry analysis for keratoconus detection.

PURPOSE: To clarify the interocular asymmetry of corneal morphological descriptors and evaluate its discriminant ability of keratoconus (KC). METHODS: This retrospective study recruited 344 normal participants and 290 KC patients, randomized to training and validation datasets. Interocular correlation and agreement were evaluated on 44 corneal morphological descriptors derived from Schiempflug tomography. Logistic regression models were constructed using binocular data and of which diagnostic performance was evaluated using the area under receiver operating characteristics curve (AUC), net reclassification improvement (NRI), and integrated discrimination improvement (IDI). RESULTS: Interocular agreement of corneal descriptors is better in the normal than in KC except for dimensions of cornea and anterior chamber. The interocular asymmetry increases along with the severity of KC. Interocular asymmetry in maximum anterior keratometry, mean anterior keratometry and higher-order aberrations of anterior surface show high AUC above 0.950. Binocular logistic regression index reaches an AUC of 0.963 with high specificity (95.2%) and brings gain to monocular parameters in distinguishing the normal eyes from KC (NRI = 0.080 (0.042 ~ 0.118), P < 0.001) and IDI = 0.071 (0.049 ~ 0.092), P < 0.001). Interocular asymmetry benefits even more in subclinical keratoconus (SKC) detection reflected by NRI (0.4784 (0.2703-0.6865), P < 0.001) and IDI (0.2680 (0.1495-0.3866), P < 0.001) measures. CONCLUSION: Interocular asymmetry is a well-characterized feature of KC and related to the severity. It is feasible to apply the interocular asymmetry in diagnosis of KC and SKC as a replenishment of monocular parameters and in progression tracking.

Comparison of corneal measurements in keratoconus eyes with two swept-source-optical coherence tomography devices and a Scheimpflug device.

PURPOSE: To assess the feasibility and reliability of biometric measurements taken with the Eyestar 900 device in keratoconus eyes in comparison with those taken with the Pentacam HR and IOLMaster 700. METHODS: Seventy-five eyes of 75 patients with keratoconus were included. The central corneal thickness (CCT), thinnest point of corneal thickness (TCT), axial length (AL), flat (K1) and steep (K2) anterior and posterior (Kp1, Kp2) keratometry, maximal keratometry (KMax) and anterior chamber depth (ACD) were compared between the Eyestar 900, Pentacam HR and IOLMaster 700. Reliability parameters such as the coefficient of variation (CoV) and intraclass correlation coefficient (ICC) were calculated. Pearson's r was determined to assess the correlation between devices. RESULTS: A high repeatability (CoV < 1%) and intraclass correlation (ICC > 0.9) was found for all devices, led by AL, TCT, K1 and K2 (CoV 0.01-0.36%; ICC 0.994-1.00). The largest correlation between devices was found for AL (Eyestar vs. IOLMaster, r = 1.0), K1 (Eyestar vs. IOLMaster, r = 0.997) and ACD (Eyestar vs. IOLMaster, r = 0.995; Pentacam vs. IOLMaster, r = 0.987; Eyestar vs. Pentacam, r = 0.983), but there were significant differences in measured values between devices (p < 0.001), whereas the correlation was only slightly lower (r = 0.947 to 0.994) for KMax, CCT, TCT, K2, Kp1 and Kp2. CONCLUSION: Keratometric and axial length measurements with the Eyestar 900 were feasible and revealed a high repeatability and a good correlation to the other devices in eyes with keratoconus.

Accelerated corneal cross-linking (18mW/cm2 for 5 min) with HPMC-riboflavin in progressive keratoconus - 5 years follow-up.

PURPOSE: To evaluate long-term results of accelerated corneal cross-linking (ACXL) in patients with progressive keratoconus, seventy-four eyes of 53 patients with progressive keratoconus (documented Kmax progression > 1D/a) who underwent ACXL (18mW/cm2 for 5 min) were included in a retrospective observational clinical study. The investigation focused on tomographic and keratometric parameters, refractive data, and visual outcomes at 5 years follow-ups. METHODS: Corrected distance visual acuity (CDVA), slit lamp, and Pentacam® examinations were conducted, including assessments of thinnest corneal point (TP), minimum radius (Rmin), corneal astigmatism, and maximum anterior keratometry (Kmax). These examinations were performed two weeks before the surgery and, on average, 56 months after the surgery. In a subgroup of 24 eyes, Pentacam® examination data from an intermediate visit at 12 months until the final visit was evaluated to confirm continuous stability. The ACXL protocol included corneal abrasion, hydroxypropylmethylcellulose (HPMC)-riboflavin eye drops administered every 5 min for a total duration of 30 min, and irradiation with 18mW/cm2 for 5 min using riboflavin eye drops applied every minute during the irradiation process. Intraoperatively, minimal corneal pachymetry of > 400 µm was ensured in every patient. RESULTS: After 56 months, all values exhibited statistically significant changes (paired t-test; CDVA p = 0.002; Kmax p < 0.001; Rmin p < 0.001; astigmatism p = 0.03; TP p < 0.001). In the subgroup analysis of 24 eyes, which included tomographical and keratometric parameters, no statistically significant changes were observed during the last 12 months of observation (paired t-test; Kmax p = 0.72; Rmin p = 0.67; astigmatism p = 0.72). Treatment failure was strictly defined as an increase in Kmax (> 1D) during the 5-year follow-up and was observed in only 3 eyes (4%). CONCLUSIONS: ACXL is an effective and safe treatment for patients with progressive keratoconus. Our results demonstrate improvements in functional and tomographical outcomes even after high-energy ACXL (18mW/cm2 for 5 min) over a long-term period of 56 months. Our analysis indicates stable conditions in previously progressive keratoconus, particularly during the final year of the observation period. The treatment failure rate was 4%.