Infectious keratitis: A review

Self-knowledge distillation-empowered directional connectivity transformer for microbial keratitis biomarkers segmentation on slit-lamp photography

The lack of standardized, objective tools for measuring biomarker morphology poses a significant obstacle to managing Microbial Keratitis (MK). Previous studies have demonstrated that robust segmentation benefits MK diagnosis, management, and estimation of visual outcomes. However, despite exciting advances, current methods cannot accurately detect biomarker boundaries and differentiate the overlapped regions in challenging cases. In this work, we propose a novel self-knowledge distillation-empowered directional connectivity transformer, called SDCTrans. We utilize the directional connectivity modeling framework to improve biomarker boundary detection. The transformer backbone and the hierarchical self-knowledge distillation scheme in this framework enhance directional representation learning. We also propose an efficient segmentation head design to effectively segment overlapping regions. This is the first work that successfully incorporates directional connectivity modeling with a transformer. SDCTrans trained and tested with a new large-scale MK dataset accurately and robustly segments crucial biomarkers in three types of slit lamp biomicroscopy images. Through comprehensive experiments, we demonstrated the superiority of the proposed SDCTrans over current state-of-the-art models. We also show that our SDCTrans matches, if not outperforms, the performance of expert human graders in MK biomarker identification and visual acuity outcome estimation. Experiments on skin lesion images are also included as an illustrative example of SDCTrans' utility in other segmentation tasks. The new MK dataset and codes are available at https://github.com/Zyun-Y/SDCTrans.

Alternative photosensitizer penetration depth evaluation in ex vivo human eyes for photodynamic antimicrobial therapy

PURPOSE

Fungal keratitis has a poor prognosis given deep penetration into the corneal stroma. While Rose Bengal photodynamic antimicrobial therapy (RB-PDAT) is a promising adjunct treatment for refractory cases, poor penetration limits its effectiveness. This study explores the penetration depth of alternative photosensitizers to address this issue.

METHODS

Thirty-five human corneas were soaked for 30 minutes in 0.0075% solution of Rose Bengal disodium (n = 5), Rose Bengal lactone (n = 5), Erythrosin B disodium (n = 5), Erythrosin B lactone (n = 5), Eosin Y disodium (n = 5), Methylene blue (n = 5), or NaCl (control, n = 5). Confocal microscopy was used to assess penetration depth.

RESULTS

All photosensitizers penetrated greater into the cornea as compared to control. There was no significant difference in penetration between Rose Bengal lactone and Rose Bengal disodium (RB lactone: 106  ± 11 µm vs RB disodium: 99 ± 13 µm, p > 0.05). The penetration depths of the alternative photosensitizers was significantly greater than either Rose Bengal formulation (Erythrosin Blactone: 192 ± 31 µm, Erythrosin B disodium: 163 ± 13 µm, Eosin Y disodium: 249 ± 31 µm, Methylene Blue: 355 ± 151 µm).

CONCLUSIONS

Alternative photosensitizers exhibit superior penetration compared to Rose Bengal. However, antimicrobial efficacy and corneal safety require more robust evaluation before clinical use.

The Pseudomonas aeruginosa T3SS can contribute to traversal of an in situ epithelial multilayer independently of the T3SS needle

Multilayered epithelia lining our tissue surfaces normally resist traversal by opportunistic bacteria. Previously, we developed a strategy to experimentally perturb this resistance in situ in the corneas of mouse eyes and used it to show that traversal of a multilayered epithelium by Pseudomonas aeruginosa requires ExsA, the transcriptional activator of its type 3 secretion system (T3SS). Here, we developed a novel strategy for quantitatively localizing individual traversing bacteria within the in situ multilayered corneal epithelium and explored the contributions of T3SS components. The results showed that T3SS translocon and T3SS effector mutants had reduced epithelial traversal efficiency. Surprisingly, a ΔpscC mutant unable to assemble the T3SS needle traversed as efficiently as wild-type P. aeruginosa, while a ΔexsD mutant "constitutively on" for T3SS expression was traversal defective. The dispensability of the T3SS needle for effector-mediated traversal was confirmed using a mutant lacking the T3SS operon except for the effector genes (ΔpscU-L mutant). That mutant reacquired the ability to traverse if complemented with rhamnose-inducible exsA, but not if the effector genes were also deleted (ΔpscU-LΔexoSTY). Western immunoblot confirmed ExoS in culture supernatants of rhamnose-induced exsA-complemented ΔpscU-L mutants lacking all T3SS needle protein genes. Together, these results show that epithelial traversal by P. aeruginosa can involve T3SS effectors and translocon proteins independently of the T3SS needle previously thought essential for T3SS function. This advances our understanding of P. aeruginosa pathogenesis and has relevance to the development of therapeutics targeting the T3SS system.IMPORTANCEWhile the capacity to cross an epithelial barrier can be a critical step in bacterial pathogenesis, our understanding of the mechanisms involved is derived largely from cell culture experimentation. The latter is due to the practical limitations of in vivo/in situ models and the challenge of visualizing individual bacteria in the context of host tissue. Here, factors used by P. aeruginosa to traverse an epithelial multilayer in situ were studied by (i) leveraging the transparent properties and superficial location of the cornea, (ii) using our established method for enabling bacterial traversal susceptibility, and (iii) developing a novel strategy for accurate and quantitative localization of individual traversing bacteria in situ. Outcomes showed that T3SS translocon and T3SS effector proteins synergistically contribute to epithelial traversal efficiency independently of the T3SS needle. These findings challenge the assumption that the T3SS needle is essential for T3SS effectors or translocon proteins to contribute to bacterial pathogenesis.

Keratomycosis: An insight into epidemiology, etiology, and antifungal susceptibility testing of causative agents at a tertiary care centre

In India, mycotic keratitis accounts for 7%-63% of infectious keratitis. Ocular trauma being the primary predisposing factor for mycotic keratitis. The present prospective, observational study was conducted on the corneal scrapings from clinically suspected patients of keratomycosis. Samples were processed as per the standard mycological techniques. Antifungal susceptibility testing was performed as per CLSI guidelines M38A2 and M27A3 for mycelial fungi and yeast, respectively. Out of a total of 254 patients suspected to be suffering from mycotic keratitis based on clinical presentation, 68 (26.77%) were positive for fungal aetiology. Male preponderance was observed with male-to-female ratio of 2.78:1. Patients in age group 51-60 years were maximally affected. The majority of the isolates of patients having fungal keratitis were that of Aspergillus sp. (31, 45.6%), followed by Fusarium sp. (12, 17.6%), Curvularia lunata (5, 7.4%), Candida sp. (4, 5.9%), Alternaria sp. (2, 2.9%), Rhodotorula sp. (1, 1.5%), and Acremonium sp. (1, 1.5%). Some rare isolates were Colletotrichum sp. (1), Botryosphaeria dothidea (2), Lasiodiplodia pseudotheobromae (1), and Acrophialophora fusispora (1). Overall, MIC values for natamycin and amphotericin B were high in Aspergillus sp., while Fusarium sp. had high MIC for voriconazole and itraconazole. Candida sp. Curvularia and Alternaria sp. had high MIC values for fluconazole. As mycotic keratitis is an infective condition involving healthy eyes, leading to morbid eye conditions and even blindness, strong clinical suspicion of fungal keratitis followed by timely diagnosis and antifungal susceptibility testing-based treatment may help the clinicians in better management and improvement of the outcome of patients.

A Tear-Based Approach for Rapid Identification of Bacterial Pathogens in Corneal Ulcers Using Nanopore Sequencing

Purpose

This prospective observational study assesses the efficacy of using portable next-generation sequencing directly on tear samples to identify bacterial pathogens in corneal ulcers.

Methods

Tear samples were collected from ulcerated and contralateral eyes using Schirmer strips. Corneal scrapings and cultures were performed as medically indicated. The 16S rRNA gene was amplified from tear samples using polymerase chain reaction (PCR), and Nanopore sequencing was used for bacterial species identification and taxonomic classification.

Results

Bacterial DNA was identified in 8 of 10 samples using the tear-based sequencing method. Nanopore sequencing accurately identified the causative bacteria in all four samples that exhibited bacterial growth on culture and detected bacterial pathogens in two of the four ulcers that did not show bacterial growth on culture. In two cases where cultures could not be obtained due to the ulcer's small size, tear sequencing successfully identified bacterial species. Among the nine contralateral tear samples collected, Nanopore sequencing identified commensal bacteria in four samples.

Conclusions

PCR amplification of 16S rRNA directly from tears followed by Nanopore sequencing is an effective, noninvasive method to identify bacterial pathogens in corneal ulcers, offering noninferior results to traditional culture methods.

Translational Relevance

By eliminating the need for corneal scrapings and nucleic acid extraction, this tear-based method improves the timing and accuracy of bacterial pathogen diagnosis in corneal ulcers, allowing for prompt detection of causative organisms and enabling earlier targeted antimicrobial therapy, thereby improving patient outcomes.

Self-assessment of Knowledge vs. Real Reactions in Simulated Emergency Situations among Contact Lens Wearers in Switzerland

BACKGROUND

If used properly, contact lenses (CLs) provide a safe and effective alternative to eyeglasses for refractive error correction. However, often due to patient noncompliance, CL-related complications may occur, such as discomfort, dry eye, as well as serious conditions like infectious keratitis. Our study aimed to assess the perceived knowledge and behavior of CL wearers in Switzerland regarding the handling of CLs and associated ocular health risks.

METHODS

This investigator-initiated, cross-sectional, qualitative, multicenter study was conducted in Switzerland from August 2023 to August 2024. After verbal consent, CL wearers were interviewed using a structured survey. The questionnaire explored participants' demographics, their perceived knowledge of the overall handling of CLs and associated health risks, as well as their behavior in two emergency scenarios involving monocular redness or pain. The descriptive statistical analysis was performed using Microsoft Excel (Microsoft Corp., Redmond, WA, USA). Figures were created with Prism version 10.2.3 (GraphPad Software, San Francisco, CA, USA).

RESULTS

A total of 172 participants with a median (IQR [range]) age of 39 (27 to 54 [10 to 82]) years were interviewed, whereby 81 (47.1%) were female. Myopia (61.0%) and keratoconus (30.2%) were the most reported indications for CL use. In terms of overall CL handling, 91.3% of participants felt well or sufficiently informed, whereas this was the case of 66.3% regarding CL-related health risks. In the scenario involving eye redness during CL use, 135 of 175 (77.1%) responses did not mention seeking professional advice, while 25 (14.3%) indicated visiting an ophthalmologist within 1 day of symptom onset. In the event of monocular pain, 67 of 179 (37.4%) responses did not consider seeking professional care, whereas 86 (48.0%) included consulting an ophthalmologist.

CONCLUSION

This study provides insight into the unmet educational need of CL wearers, especially regarding CL-related complications. Participants generally felt better informed about overall CL handling than about the potential health risks. This information discrepancy is reflected by their responses to scenarios involving monocular redness or pain, where a considerable number of participants failed to react adequately. Further studies are warranted to explore effective, practical strategies for improving patient awareness and behavior.

Dipeptidic Phosphonates: Potent Inhibitors of Pseudomonas aeruginosa Elastase B Showing Efficacy in a Murine Keratitis Model

The ubiquitous opportunistic pathogen Pseudomonas aeruginosa is responsible for severe infections and notoriously known for acquiring antimicrobial resistance. Inhibiting the bacterium's extracellular elastase, LasB - a zinc-dependent protease - presents a promising strategy to mitigate its virulence. Within this medicinal chemistry-driven hit-to-lead optimization campaign, a new series of highly potent dipeptidic phosphonates is designed and synthesized following a structure-based drug-discovery approach. In vitro and in vivo evaluation reveal beneficial pharmacokinetic profiles, excellent selectivity over human off-targets and good tolerability in murine toxicity studies. Ultimately, the scaffold presented herein demonstrates promising in vivo efficacy in a murine Pseudomonas aeruginosa keratitis model in combination with the antibiotic meropenem.

Nitroxoline evidence amoebicidal activity against Acanthamoeba castellanii through DNA damage and the stress response pathways

Acanthamoeba castellanii is a widespread unicellular eukaryote found in diverse environments, including tap water, soil, and swimming pools. It is responsible for severe infections, such as Acanthamoeba keratitis and granulomatous amebic encephalitis, particularly in individuals with immunocompromisation. The ability of protozoans to form dormant and persistent cysts complicates treatment, as current therapies are ineffective against cyst stages and suffer from poor specificity and side effects. Nitroxoline, a quinoline derivative with well-established antibacterial, antifungal, and antiviral properties, is a promising therapeutic candidate. This study aimed to elucidate cellular signalling events that counteract the effects of nitroxoline. In this study, nitroxoline significantly reduced the viability of A. castellanii trophozoites in a dose- and time-dependent manner, inducing morphological changes and apoptosis. Transcriptomic analysis revealed substantial alterations in gene expression, including enrichment of metabolic pathways, DNA damage responses, and iron ion binding. Nitroxoline treatment upregulated genes involved in DNA repair and oxidative stress response while regulating genes in the methionine and cysteine cycles. It also decreased the mitochondrial membrane potential, H₂S production, and total iron amount in A. castellanii. Bioinformatic analyses and molecular docking studies suggest direct interactions between nitroxoline and several A. castellanii proteins. Our research provides a comprehensive molecular map of the response of A. castellanii to nitroxoline, revealing significant changes in gene expression related to the stress response and metabolic pathways. These findings underscore the potential of nitroxoline as a potent anti-Acanthamoeba agent, offering new insights into its mechanism of action and paving the way for effective combinational therapeutic strategies.

Advances in the application of gelatin-based materials in anterior segment diseases

Anterior segment diseases are among the most common ocular conditions, severely impacting individuals' visual health. Additionally, due to the barrier functions of the anterior segment tissues, traditional treatment methods often suffer from low efficiency and significant side effects, presenting urgent challenges that need to be addressed. Gelatin inherently possesses excellent biocompatibility and biodegradability, and when combined with its unique cell adhesion sequences and the ability to flexibly modulate mechanical and optical properties through physical and chemical modifications, it demonstrates tremendous potential in anterior segment tissue engineering and drug delivery applications. Compared to conventional surgical and eye drop therapies, gelatin-based materials can reduce the risk of complications, enhance drug bioavailability, extend drug retention time, and achieve personalized and precise treatment for various anterior segment diseases through technologies such as 3D bioprinting. However, gelatin-based materials have limitations, including low mechanical strength and thermal stability. Therefore, this paper focuses on recent research regarding the application of gelatin-based materials in anterior segment diseases, systematically summarizing their advantages in treatment, the challenges they face, and their developmental potential.

Microbial Keratitis Before, During and After the COVID-19 Pandemic, and the Role of Contact Lens Wear and Hand Hygiene

Introduction

During the COVID-19 pandemic, there was a significant decline in the number of patients with both non-urgent and urgent ophthalmologic conditions presenting to emergency departments, leading to concerns about the whereabouts of patients in need of care. We hypothesized that there was an actual decrease in microbial keratitis (MK) cases, due to reduced contact lens (CL) wear and improved hand hygiene, including alcohol-based hand disinfection. Besides, we questioned if non-pharmaceutical interventions would have a sustained effect after the COVID-19 pandemic.

Methods

Retrospectively, characteristics of patients presenting with MK at a large ophthalmic tertiary referral center were compared during 9 March-15 June of 2018 and 2019 ("pre-COVID"), 2020 ("COVID") and 2022 and 2023 ("post-COVID"). In an online cross-sectional survey among CL wearers, CL wear and hand hygiene habits were compared for the recall months February and April 2020.

Results

Three hundred and one MK patients were included: 79 in 2018, 69 in 2019, 41 in 2020, 60 in 2022 and 52 in 2023. Presentation delay was ≥4 days in 38% during COVID, compared to 54% pre-COVID (p = 0.106). The proportion of CL related MK did not differ (p = 0.704). Fewer patients were admitted than pre-COVID (p = 0.026), without a difference in admission indications (p = 0.322). Pseudomonas aeruginosa and Staphylococcus aureus cases were not observed during COVID. Post-COVID, MK by Pseudomonas aeruginosa occurred more often than pre-COVID (p < 0.001). In the online survey with 791 respondents, hand washing before CL insertion and removal and hand disinfection were reported more often in April 2020 than February 2020 (respectively, p = 0.001, p < 0.001 and p < 0.001).

Conclusion

We found no evidence of MK patients facing barriers to accessing hospital care during the COVID-19 pandemic, as presentation delays were not longer and cases not more severe. Our data suggest that a decreased MK incidence may be due to improved hand hygiene practices, including alcohol-based hand disinfection.

An occupational health assessment of dinotefuran exposure in greenhouse vegetable workers: Metabolomic profiling and toxicokinetic analysis

This study aimed to explore the metabolite profiles of populations engaged in intensive vegetable cultivation and their exposure to pesticides. As urbanization progresses and eating habits evolve, intensive vegetable farming has rapidly expanded; however, this cultivation method poses potential health risks to farmers, particularly due to long-term exposure to "greenhouse gases" in enclosed environments. The study investigated the demographic characteristics of individuals in vegetable-growing areas, collected relevant biological samples, and assessed exposure levels by analyzing pesticide metabolites in urine. The results indicated that the types and concentrations of pesticide metabolites detected in the urine of the exposed group were significantly higher than those in the control group, with notable increases in neonicotinoid metabolites such as dinotefuran (DIN) and thiacloprid. Furthermore, the impact of these pesticides on mammalian organisms was examined through animal experiments, which revealed dynamic changes in the concentration of DIN in mouse serum and urine, providing valuable data on its biological metabolic characteristics. These findings underscore the importance of ongoing disease prevention, pollution control, and the need for enhanced health monitoring and protective measures for agricultural workers.

Responsive Microneedles for Diagnostic and Therapeutic Applications of Ocular Diseases

Traditional ophthalmic formulations are characterized by low bioavailability, short intraocular retention time, strong irritation, and failure to achieve the expected therapeutic effect due to the special physiological structure of the eye and the existence of many barriers. Microneedle drug delivery is a novel transdermal drug delivery modality. Responsive microneedles are defined as controllably releasing the drug payloads in response to physiological stimuli, including pH levels, temperature, enzymes, and reactive oxygen species (ROS), as well as external stimuli such as magnetic fields and light. In addition to inheriting the advantages of traditional microneedles, which include enhanced targeting and permeability, non-invasiveness, and painless application, the integration with stimulus-responsive materials enables responsive microneedles to achieve a personalized precision drug delivery process, which further increases the accuracy and efficiency of ocular treatments, making on-demand drug delivery possible. This article systematically reviews the classification, mechanisms, and characteristics of responsive microneedles and provides a detailed introduction to their diagnostic and therapeutic applications as well as real-time monitoring potential in ocular diseases, aiming to offer insights for the precision treatment of ocular diseases in the future.

Epidemiological and Antimicrobial Resistance Trends in Bacterial Keratitis: A Hospital-Based 10-Year Study (2014-2024)

Bacterial keratitis (BK) is a severe ocular infection that can lead to vision loss, with antimicrobial resistance (AMR) posing a growing challenge. This study retrospectively analyzed 1071 bacterial isolates from corneal infections over a 10-year period (2014-2024) at a tertiary ophthalmic center in Beijing, categorizing them into three distinct phases: pre-COVID-19, during COVID-19, and post-COVID-19. The results indicated significant changes in pathogen distribution, including a marked decrease in Gram-positive cocci (from 69.8% pre-COVID-19 to 49.3% in post-COVID-19, p < 0.001), particularly in Staphylococcus epidermidis. In contrast, Gram-positive bacilli, particularly Corynebacterium spp., increased from 4.2% to 16.1% (p < 0.001). The susceptibility to gatifloxacin, moxifloxacin, and ciprofloxacin significantly declined in both Gram-positive cocci and bacilli during the COVID-19 period (all p < 0.01). Gatifloxacin resistance in Staphylococcus rose from pre-COVID-19 (15.2%) to COVID-19 (32.7%), remaining high post-COVID-19 (29.7%). A similar trend was observed in Streptococcus and Corynebacterium, where resistance rose sharply from 12.0% and 22.2% pre-COVID-19 to 42.9% during COVID-19, and remained elevated at 40.0% and 46.4% post-COVID-19, respectively (p < 0.01). These findings emphasize the rapid rise of fluoroquinolone resistance in several bacterial groups, underscoring the urgent need for continuous surveillance and improved antimicrobial stewardship to enhance treatment outcomes.

An exploration of the ocular mysteries linking nanoparticles to the patho-therapeutic effects against keratitis

Microbial keratitis, a sight-threatening corneal infection, remains a significant global health concern. Conventional therapies using antimicrobial agents often suffers from limitations such as poor drug penetration, side effects, and occurrence of drug resistance, with poor prognosis. Novel treatment techniques, with their unique properties and targeted delivery capabilities, offers a promising solution to overcome these challenges. This review delves into timely update of the state-of-the-art advance therapeutics for keratitis treatment. The diverse microbial origins of keratitis, including viral, bacterial, and fungal infections, exploring their complex pathogenic mechanisms, followed by the drug resistance mechanisms in keratitis pathogens are reviewed briefly. Importantly, the emerging therapeutic techniques for keratitis treatment including piezodynamic therapy, photothermal therapy, photodynamic therapy, nanoenzyme therapy, and metal ion therapy are summarized in this review showcasing their potential to overcome the limitations of traditional treatments. The challenges and future directions for advance therapies and nanotechnology-based approaches are discussed, focusing on safety, targeting strategies, drug resistance, and combination therapies. This review aims to inspire researchers to revolutionize and accelerate the development of functional materials using different therapies for keratitis treatment.

Enhancing Acanthamoeba diagnostics: rapid detection of viable Acanthamoeba trophozoites and cysts using viability PCR assay

Acanthamoeba keratitis (AK) is a sight-threatening corneal infection that is challenging to diagnose and treat due to the resistance of Acanthamoeba to standard antimicrobial agents. Current detection methods have limitations. This study aimed to develop and validate a sensitive viability PCR (v-PCR) assay using a photoreactive dye to distinguish viable from non-viable Acanthamoeba for rapid identification of viable Acanthamoeba trophozoites and cysts. Propidium monoazide (PMAxx) was used as a photoreactive dye. Mixtures containing decreasing percentages of viable Acanthamoeba, including reference strains Acanthamoeba polyphaga trophozoites and cysts, Acanthamoeba castellanii trophozoites, and Acanthamoeba castellanii trophozoites from a clinical sample, were prepared. Disinfectant efficacy against Acanthamoeba was also assessed. Samples were divided into PMAxx-treated and non-PMAxx-treated parts, and v-PCR assay was applied to both. The difference in viable Acanthamoeba was determined by subtracting the cycle threshold (Ct) value of the PMAxx-treated sample from the non-PMAxx-treated sample. Mixtures with decreasing concentrations of viable Acanthamoeba trophozoites and cysts showed increasingly lower delta Ct values as the percentage of viable Acanthamoeba decreased, as expected. This relationship was observed across all tested samples. Menicon Progent effectively eliminated A. polyphaga trophozoites and cysts, while propamidine, chlorhexidine, or their combination resulted in approximately 2-log reductions in A. polyphaga trophozoites and cysts. In the current study, a rapid v-PCR assay was developed that can distinguish between viable and non-viable Acanthamoeba, for both trophozoites and cysts, across multiple species. The presence of viable Acanthamoeba, as determined by v-PCR, allows monitoring of treatment response and efficacy in AK.IMPORTANCEThe development of a sensitive viability PCR (v-PCR) assay using propidium monoazide (PMAxx) as a photoreactive dye marks a significant advancement in the diagnosis and treatment of Acanthamoeba keratitis (AK), a severe corneal infection notorious for its resistance to conventional antimicrobials. This innovative assay offers a rapid and accurate method to distinguish viable from non-viable Acanthamoeba trophozoites and cysts, addressing a critical need in the field. By effectively distinguishing between viable and non-viable Acanthamoeba, this test enables monitoring of treatment response and efficacy, essential for guiding clinical interventions in AK cases. The successful validation of this v-PCR assay across various Acanthamoeba species and its ability to assess disinfectant efficacy further underline its potential as a valuable tool for improving diagnostic precision and therapeutic outcomes in the treatment of AK.

Healing the cornea: Exploring the therapeutic solutions offered by MSCs and MSC-derived EVs

Affecting a large proportion of the population worldwide, corneal disorders constitute a concerning health hazard associated to compromised eyesight or blindness for most severe cases. In the last decades, mesenchymal stem/stromal cells (MSCs) demonstrated promising abilities in improving symptoms associated to corneal diseases or alleviating these affections, especially through their anti-inflammatory, immunomodulatory and pro-regenerative properties. More recently, MSC therapeutic potential was shown to be mediated by the molecules they release, and particularly by their extracellular vesicles (EVs; MSC-EVs). Consequently, using MSC-EVs emerged as a pioneering strategy to mitigate the risks related to cell therapy while providing MSC therapeutic benefits. Despite the promises given by MSC- and MSC-EV-based approaches, many improvements are considered to optimize the therapeutic significance of these therapies. This review aspires to provide a comprehensive and detailed overview of current knowledge on corneal therapies involving MSCs and MSC-EVs, the strategies currently under evaluation, and the gaps remaining to be addressed for clinical implementation. From encapsulating MSCs or their EVs into biomaterials to enhance the ocular retention time to loading MSC-EVs with therapeutic drugs, a wide range of ground-breaking strategies are currently contemplated to lead to the safest and most effective treatments. Promising research initiatives also include diverse gene therapies and the targeting of specific cell types through the modification of the EV surface, paving the way for future therapeutic innovations. As one of the most important challenges, MSC-EV large-scale production strategies are extensively investigated and offer a wide array of possibilities to meet the needs of clinical applications.

A Transformative Wearable Corneal Microneedle Patch for Efficient Therapy of Ocular Injury and Infection

Ocular injury and infection are significant causes of vision impairment and blindness globally. Effective treatment is, however, challenging due to the physical barrier of the cornea, which restricts drug penetration in the eye, as well as the presence of eye injury that necessitates continuous delivery of growth factors on the ocular surface for cornea healing. Here, we introduce a transformative wearable corneal microneedle (MN) patch designed for efficient therapy of ocular injury and infection. The MN patch comprises water-soluble tips that encapsulate antibacterial nanoparticles (NPs), along with a transformative backing layer that contains epidermal growth factor (EGF). Upon insertion into the eye, the MN tips dissolve swiftly within the cornea stroma, resulting in the release of the antimicrobial NPs to efficiently eradicate bacteria. Meanwhile, the residual backing layer undergoes rapid in situ transformation upon contact with mildly acidic fluid from infected corneal edema, converting into a contact lens that conforms to the eye's surface, which facilitates sustained release of EGF on the ocular surface over 8 h to promote corneal healing. Benefiting from these features, the designed transformative corneal MN patch demonstrates superior efficacy in treating ocular injuries and infections in vivo, offering a promising therapeutic strategy to manage eye diseases.

Photoactivated chromophore for keratitis-Corneal cross-linking in dogs and cats: A retrospective study in Italy

OBJECTIVE

To evaluate the success and failure rate of photoactivated chromophore for keratitis-corneal cross-linking (PACK-CXL) therapy in a single population of dogs and cats. To identify the usefulness of the PACK-CXL based on ulcer depth and establish a cutoff at which this procedure could be recommended. To analyze the influence of the different variables in corneal healing time and to report the presence of secondary endothelial damage and cataract formation.

MATERIALS AND METHODS

Medical records of dogs and cats with presumptive infectious keratitis which underwent accelerated epithelium-off PACK-CXL between 2016 and 2023 were reviewed and analyzed.

RESULTS

Records for 369 animals were included, and the overall success rate for healing was 97% (range 4-74 days and no rescue procedure). The second success (re-epithelialization <30 days and no rescue procedure) rate was 86%, and a total of 40 eyes needed more than 1 month for the corneal repair. Corneal ulcers were classified in three categories based on the depth: 0%-33% (46%), 34%-66% (37.4%), and 67%-100% (16.5%). The cutoff at which PACK-CXL had a higher probability of failure was with ulcer depth >66.5%. Animals who suffered from keratomalacia and hypopyon at presentation, or were treated with topical serum or gentamicin after PACK-CXL showed an increase in epithelial healing time (EHT). Increasing age, brachycephalic conformation, keratomalacia alone, and deeper ulcers were identified as risk factors for the treatment outcome. Secondary endothelial injury or cataract formation was not noted in this study.

CONCLUSIONS

Accelerated PACK-CXL is a non-invasive, adjunctive treatment to medical therapy, which can be used in presumed infectious keratitis with a high probability of success. However, it is important to take in consideration the patient age, skull conformation, presence of keratomalacia, and the ulcer depth.

Transmission rates of UV-A and green light in an ex vivo corneal crosslinking model for infectious keratitis

PURPOSE

To investigate the light transmission (LT) of UV-A and green light through infected corneas saturated with riboflavin or rose bengal in an ex vivo porcine model for infectious keratitis.

SETTING

University of Zurich, Zurich, Switzerland, and Empa, St. Gallen, Switzerland.

DESIGN

Laboratory study.

METHODS

Ex vivo porcine eyes (n = 162) were divided into 3 groups: control eyes, eyes infected with Staphylococcus aureus , and eyes infected with Pseudomonas aeruginosa . Corneas remained either uninfected or were infected with S. aureus and P. aeruginosa and were either left untreated or were instilled with 0.1% riboflavin or 0.1% rose bengal. Corneal buttons were prepared, and corneal LT was measured at 365 nm and 522 nm using a spectrophotometer. LT values were calculated and compared. Transmission electron microscopy (TEM) was used to visualize structural damage and bacteria within infected corneas.

RESULTS

Riboflavin-saturated corneas infected by S. aureus or P. aeruginosa (LT = 0.77% [0.41-1.87] and 0.81% [0.23, 1.46]) exhibited 3.18-fold and 3.02-fold lower LT values, respectively, than uninfected corneas (LT = 2.45% [2.15, 5.89]) (both P -values < 0.001). No LT difference was found between rose bengal-saturated corneas infected by S. aureus or P. aeruginosa and uninfected corneas (all LT values = 0.01% [0.01-0.01]; both P -values = 0.08). TEM showed bacteria on corneal stroma borders and occasionally inside the stroma.

CONCLUSIONS

The results indicate that the amount of light arriving at the corneal endothelium is substantially reduced in infected corneas. The total fluence of clinical photoactivated chromophore for keratitis corneal crosslinking protocols can be safely increased substantially while maintaining a low risk of corneal endothelial damage.

Fungal keratitis complicating the diagnosis of Acanthamoeba keratitis

A 42-year-old woman was referred to an emergency department. She had an unresponsive corneal ulcer that was initially diagnosed as Herpes simplex virus keratitis. Later, the microbiological studies revealed fungal keratitis. Although the patient was given topical antifungal medication, the clinical presentation did not support improvement. Despite using antifungal medication, the infiltration continued to progress, and the patient underwent therapeutic penetrating keratoplasty (T-PKP). Corneal tissue was collected and sent for histopathologic and molecular examination. The results revealed the presence of both Acanthamoeba T4 subgroup and Fusarium sp. This case emphasizes the importance of considering Acanthamoeba infection in progressive and non-responsive infectious keratitis, especially fungal specimens. Polymerase chain reaction (PCR) is an appropriate laboratory molecular diagnostic test for accurate diagnosis of Acanthamoeba keratitis.

Clinical strategies to prevent recurrence of Herpes simplex and Herpes zoster following ocular surgery: A comprehensive review with practical guidelines

Recurrences of herpetic infections following intraocular surgeries pose a threat to optimal surgical outcomes. The high prevalence of herpetic diseases require ophthalmologists to be familiar with the special measures in the surgery of these patients. A thorough preoperative assessment and meticulous postoperative surveillance should be tailored for each patient, depending on the surgery and the risk of virus reactivation. We compile the relevant evidence in the literature and provide a comprehensive review of the preoperative assessment and postoperative diagnostic clues and management of the herpetic infections following different types of intraocular surgeries, including cataract surgery, keratoplasty, corneal crosslinking, glaucoma, and refractive surgeries.

Factors Associated with Vision Outcomes in Microbial Keratitis: A Multisite Prospective Cohort Study

PURPOSE

To investigate factors associated with 90-day vision in patients with microbial keratitis (MK).

DESIGN

Multicenter prospective cohort study recruited patients with MK from the United States and India from July 23, 2020, through May 1, 2024, and followed them for 90 days.

PARTICIPANTS

Individuals ≥ 15 years of age with MK of > 2 mm2 in stromal infiltrate area without prior corneal surgery or gluing, impending corneal perforation or keratoplasty, no light perception vision, current pregnancy, or incarceration.

METHODS

Data on sociodemographics, history, symptoms, clinical measures, and best-corrected visual acuity (BCVA) (as logarithm of the minimum angle of resolution (logMAR) units) at initial and 90-day visits were gathered, with BCVA carried forward for those healed before 90 days. Features were summarized overall and by site. Site-stratified multivariable linear regression models were investigated for associations with 90-day BCVA.

MAIN OUTCOME MEASURES

Ninety-day logMAR BCVA.

RESULTS

Of 479 participants analyzed, after exclusions (n = 31) and participants without a 90-day BCVA (n = 52), participants had an average 90-day BCVA of 1.36 ± 1.40 logMAR in the United States (US) and 0.70 ± 0.99 logMAR in India (P < 0.0001). For the US, worse 90-day BCVA was associated with worse presenting BCVA (β = 0.05-logMAR per 0.1-logMAR unit increase in presenting BCVA; P < 0.0001), longer time until presentation (β = 0.01 per day; P < 0.0001), no contact lens use (β = 0.46; P = 0.0131), and larger stromal infiltrate area (bacterial: β = 0.02 per 1-mm2 [P = 0.0082]; fungal: β = 0.10 per 1-mm2 increase in area [P = 0.0002]; P = 0.0017 for interaction). For the India, worse 90-day BCVA was associated with worse presenting BCVA (β = 0.04 logMAR; P < 0.0001), longer delays to presentation (β = 0.03 per day; P = 0.0004), diabetes mellitus (β = 0.41; P = 0.0019), hypopyon (β = 0.27; P = 0.0083), no recent ocular trauma (β = 0.21; P = 0.0370), and larger stromal infiltrate area (fungal: β = 0.03 per 1-mm2 [P < 0.0001]; bacterial: nonsignificant β [P = 0.07]; P = 0.0001 for interaction).

CONCLUSIONS

Initial vision, longer time until presentation, and larger infiltrate size conferred risk for worse 90-day BCVA, whereas other factors were unique. Systems to mitigate care delays and to support access care are needed would support clinicians and improve vision outcomes.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Fungal infection monitoring on corneal epithelium ex vivo model and its collection over polyethersulfone membrane for detecting Candida albicans and Aspergillus fumigatus

In this paper we report a human ex vivo model of Aspergillus fumigatus and Candida albicans infection of the cornea. We demonstrate the ability to monitor fungal growth on the cornea through optical and immunofluorescence microscopy. Additionally, we establish a method for collection of fungal antigens in polyethersulfone (PES) membrane-based sample collectors from the surface of fungal inoculated corneas. Immunofluorescence microscopy was performed directly on both corneal tissue and PES membrane sample collectors. For the latter case, we devised an original ad-hoc method by attaching the membranes used for the collection on standard glass slides, which we call glass slide KIT. This enabled easy handling and improved efficiency for specifically recognizing the corresponding fungal infections by simple immunoassay protocols. As a result, we firstly observe the ability to monitor fungi in corneal tissue, and secondly demonstrate the adsorption of fungal antigens onto PES membranes. Thus, we report for the first time the specific detection of fungal corneal infections in easy to use PES membrane based glass slide KITs through simple immunofluorescence, as an alternative to microbiological culture.

Optical Coherence Tomography in Infectious Keratitis After Femtosecond Keratorefractive Surgery

Objectives: Anterior Segment Optical coherence tomography (AS-OCT) can help in the diagnosis and treatment of infectious keratitis, but it has not been studied in cases occurring after corneal refractive surgery procedures such as femtosecond laser in situ keratomileusis (FS-LASIK) and keratorefractive lenticule extraction (KLEx). In these procedures, a surgical interface is created, where infections usually start, thus determining a different AS-OCT pattern compared to non-surgical infections, which begin on the corneal surface. Methods: We retrospectively reviewed 22,756 eyes of 13,564 patients who underwent FS-LASIK and KLEx at our surgical center. Results: Four cases of post-refractive surgery infectious keratitis were included (two after FS-LASIK and two after KLEx), in which the AS-OCT identified an initial infiltrate in the interface, followed by interface inflammation. In one case, after FS-LASIK, interface fluid accumulation occurred. In one case, after KLEx, diffuse interface inflammation led to stromal reabsorption, later compensated by stromal reformation and epithelial hyperplasia, well documented by OCT. Conclusions: AS-OCT represents a useful tool for assessing corneal infections after refractive surgery, guiding the treatment, and evaluating the healing process and residual corneal scarring.

Contact Lens Wear Alters Transcriptional Responses to Pseudomonas aeruginosa in Both the Corneal Epithelium and the Bacteria

Purpose

Healthy corneas resist colonization by virtually all microbes, yet contact lens wear can predispose the cornea to sight-threatening infection with Pseudomonas aeruginosa. Here, we explored how lens wear changes corneal epithelium transcriptional responses to P. aeruginosa and its impact on bacterial gene expression.

Methods

Male and female C57BL/6J mice were fitted with a contact lens on one eye for 24 hours. After lens removal, corneas were immediately challenged for 4 hours with P. aeruginosa. A separate group of naïve mice was similarly challenged with bacteria. Bacteria-challenged eyes were compared to uninoculated naïve controls, as was lens wear alone. Total RNA sequencing determined corneal epithelium and bacterial gene expression.

Results

Prior lens wear profoundly altered the corneal response to P. aeruginosa, including upregulated pattern recognition receptors (tlr3, nod1); downregulated lectin pathway of complement activation (masp1); amplified upregulation of tcf7, gpr55, ifi205, and wfdc2 (immune defense); and further suppression of efemp1 (corneal stromal integrity). Without lens wear, P. aeruginosa upregulated mitochondrial and ubiquinone metabolism genes. Lens wear alone upregulated axl, grn, tcf7, and gpr55 (immune defense) and downregulated Ca2+-dependent genes necab1, snx31, and npr3. P. aeruginosa exposure to prior lens wearing versus naïve corneas upregulated bacterial genes of virulence (popD), its regulation (rsmY, PA1226), and antimicrobial resistance (arnB, oprR).

Conclusions

Prior lens wear impacts corneal epithelium gene expression, altering its responses to P. aeruginosa and how P. aeruginosa responds to it favoring virulence, survival, and adaptation. Impacted genes and associated networks provide avenues for research to better understand infection pathogenesis.

Inactivation of antibiotic resistant bacteria by nitrogen-doped carbon quantum dots through spontaneous generation of intracellular and extracellular reactive oxygen species

The widespread antibiotic resistance has called for alternative antimicrobial agents. Carbon nanomaterials, especially carbon quantum dots (CQDs), may be promising alternatives due to their desirable physicochemical properties and potential antimicrobial activity, but their antimicrobial mechanism remains to be investigated. In this study, nitrogen-doped carbon quantum dots (N-CQDs) were synthesized to inactivate antibiotic-resistant bacteria and treat bacterial keratitis. N-CQDs synthesized via a facile hydrothermal approach displayed a uniform particle size of less than 10 nm, featuring a graphitic carbon structure and functional groups including -OH and -NH2. The N-CQDs demonstrated antimicrobial activity against Staphylococcus aureus (S. aureus) and methicillin-resistant S. aureus, which was both dose- and time-dependent, reducing the survival rate to below 1 %. The antimicrobial activity was confirmed by live/dead staining. In in vivo studies, the N-CQDs were more efficient in treating drug-resistant bacterial keratitis and reducing corneal damage compared to the common antibiotic levofloxacin. The N-CQDs were shown to generate intracellular and extracellular ROS, which potentially caused oxidative stress, membrane disruption, and cell death. This antimicrobial mechanism was supported by scanning and transmission electron microscopy, significant regulation of genes related to oxidative stress, and increased protein and lactate dehydrogenase leakage. This study has provided insight into the development, application, and mechanism of N-CQDs in antimicrobial applications.

Antagonizing NK-1R modulates pain perception following corneal injury

Substance P (SP) expressed by corneal nerves, is an 11-amino acid long neuropeptide from the tachykinin family, encoded by the Tac1 gene, and binds to neurokinin receptors. SP overexpression is associated with various pathological responses in the cornea including vasodilation, pain, inflammation, and angiogenesis in the normally avascular tissue. This study investigates the role of neurokinin-1 receptor (NK-1R) mediated signaling in nociception, nerve regeneration, and neuronal activation following mechanical corneal injury in mice. Corneal injuries were induced in age- and sex-matched C57BL/6 mice by removing corneal epithelium and partial anterior stroma. Following injury, mice were treated with either L-733,060, an NK-1R antagonist, or vehicle, administered topically twice daily for 21 days. Corneal SP levels were measured using ELISA, and nerve regeneration was assessed by quantifying corneal nerve fiber density (CNFD) via β-Tubulin III staining. Gene expression of neuronal markers (ATF3, GFAP, cFos, TRPV1, and TRPM8) in the trigeminal ganglia was measured using qPCR. Pain responses were evaluated using the eye-wiping test (EWT) and palpebral ratio (PR). Results indicated a persistent increase in corneal SP post-injury, significantly reduced by NK-1R antagonism. At 21 days, NK-1R antagonist-treated mice showed higher CNFD, reduced expression of neuronal activation markers, and lower pain perception compared to controls. These findings suggest that SP/NK-1R signaling is critical in corneal nociception post-injury, and its inhibition reduces pain, prevents neuronal hyperactivation, and supports nerve regeneration.

Etiology of infectious keratitis

OBJETIVES

Analyze the etiology of infectious keratitis in our hospital.

MATERIAL AND METHODS

Retrospective study in which the medical records of patients were reviewed in which a keratitis-producing microorganism was detected during the last 9 years (January 2014-December 2022). The sample was obtained by corneal scraping and seeded in non-selective media. Bacterial and fungal identification was carried out by mass spectrometry and viral identification by polymerase chain reaction (PCR). Sensitivity was obtained using disk-plate antibiograms, E-test or broth microdilution systems.

RESULTS

A total of 433 samples of corneal scrapings belonging to 416 patients were processed. Of the total samples, 196 were positive (44,3%). The average age was 55 years, with 51% being women. Regarding the etiology, we found the following isolates: Gram-positive bacteria (N=83) (44%), highlighting Staphylococcus aureus (N=33), coagulase-negative staphylococci (N=26), being Staphylococcus epidermidis the most frequent (N=19). Gram-negative bacteria (N=67) (35%), including: Pseudomonas aeruginosa (N=31), 42% associated with the use of contact lenses and Enterobacterales (N=16). Anaerobes (N=19), which 18 isolates were Cutibacterium acnes. Regarding viral etiology (N=10): herpes simple type 1 (N=7). Varicella-zoster virus (N=3). Finally, the fungal etiology (N=13), highlighting Candida spp. (N=10).

CONCLUSIONS

The main agents of infectious keratitis are Staphylococcus aureus and Pseudomonas aeruginosa. The causative agent was detected in 44,3% of the samples, so microbiological analysis of these samples is highly advisable.

The Pseudomonas aeruginosa T3SS can contribute to traversal of an in situ epithelial multilayer independently of the T3SS needle

Multilayered epithelia lining our tissue surfaces normally resist traversal by opportunistic bacteria. Previously, we developed a strategy to experimentally perturbate this resistance in situ in the corneas of mouse eyes and used it to show that traversal of a multilayered epithelium by Pseudomonas aeruginosa requires ExsA, the transcriptional activator of its type 3 secretion system (T3SS). Here, we developed a novel strategy for quantitively localizing individual traversing bacteria within the in situ multilayered corneal epithelium and explored contributions of T3SS components. The results showed that T3SS translocon and T3SS effector mutants had reduced epithelial traversal efficiency. Surprisingly, a ΔpscC mutant unable to assemble the T3SS needle traversed as efficiently as wild-type P. aeruginosa, while a ΔexsD mutant 'constitutively on' for T3SS expression was traversal defective. Dispensability of the T3SS needle for effector-mediated traversal was confirmed using a mutant lacking the T3SS operon except the effector genes (ΔpscU-L mutant). That mutant reacquired the ability to traverse if complemented with rhamnose-inducible exsA, but not if the effector genes were also deleted (ΔpscU-LΔexoSTY). Western immunoblot confirmed ExoS in culture supernatants of rhamnose-induced exsA-complemented ΔpscU-L mutants lacking all T3SS needle protein genes. Together, these results show that epithelial traversal by P. aeruginosa can involve T3SS effectors and translocon proteins independently of the T3SS needle previously thought essential for T3SS function. This advances our understanding of P. aeruginosa pathogenesis and has relevance to development of therapeutics targeting the T3SS system.

A Sneaky Culprit: Secondary Infectious Keratitis Due to Brevundimonas diminuta

PURPOSE

To describe a rare case of infectious keratitis secondary to Brevundimonas diminuta, a gram-negative bacillus with fluoroquinolone resistance and rare clinical isolation.

METHODS

A 50-year-old man with contact lens overuse presented with a large corneal ulcer and hand motion visual acuity. Initial treatment with fortified topical tobramycin and vancomycin yielded slow improvement, and initial culture grew Staphylococcus epidermidis, Staphylococcus hominis, and Corynebacterium bovis. Therapy was tapered to topical moxifloxacin. Loteprednol was added to reduce corneal inflammation after presumed sterilization. Persistent epithelial defect and worsening infiltrate after 3 weeks prompted repeat culture and corneal punch biopsy.

RESULTS

Repeat culture revealed B. diminuta resistant to moxifloxacin. Treatment was modified to tobramycin, and therapeutic penetrating keratoplasty was pursued to prevent further stromal loss. Four months postoperatively, the cornea remained clear without recurrence or neovascularization.

CONCLUSION

To our knowledge, this is the second reported culture-positive case of secondary infectious keratitis with B. diminuta, highlighting its rarity and potential for delayed identification. The atypical response to initial therapy underscores the importance of repeat cultures and corneal biopsy in persistent cases. This case contributes to the growing understanding of rare ocular pathogens, advocating for a vigilant clinical approach.

Reply to Troisi et al. Comment on "Cabrera-Aguas, M.; Watson, S.L. Updates in Diagnostic Imaging for Infectious Keratitis: A Review. Diagnostics 2023, 13, 3358"

We appreciate the interest of Troisi and his colleagues [...].

Topical Caspofungin 0.5% Monotherapy for Filamentous Fungal Keratitis

PURPOSE

To describe a case series of patients with 12 fungal keratitis treated with caspofungin 0.5% eye drops.

METHODS

In this study, 12 patients diagnosed with fungal keratitis were treated with topical compounded caspofungin 0.5% eye drops. The authors also reviewed the existing literature on topical caspofungin 0.5% for managing fungal keratitis.

RESULTS

The average age of the patients was 50.16 ± 13.74 years, and the average time to presentation was 9.66 ± 6 days from the onset of symptoms. Out of the 12 patients, 10 were males, and 2 were females. Three (25%) patients had infiltrates extending up to the mid-stromal level, whereas 9 (75%) had superficial infiltration. Topical caspofungin monotherapy successfully treated the fungal infection in 8 (66.6%) patients, whereas 4 patients required additional medication and/or surgical intervention. The average size of the infiltration was 3.44 ± 1.21 mm. The group that responded to treatment had better final visual acuity compared to the nonresponding group, with values of 0.41 ± 0.48 logarithm of the minimum angle of resolution and 1.39 ± 0.10 logarithm of the minimum angle of resolution (P-value = 0.023), respectively.

CONCLUSIONS

Topical caspofungin 0.5% is a safe and effective treatment for selected cases of fungal keratitis. However, cases with larger or deeper initial infiltrates, or those caused by Fusarium infection, may not respond adequately to topical caspofungin monotherapy.

The evolution of antifungal therapy: Traditional agents, current challenges and future perspectives

Fungal infections kill more than 3 million people every year. This high number reflects the significant challenges that treating these diseases worldwide presents. The current arsenal of antifungal drugs is limited and often accompanied by high toxicity to patients, elevated treatment costs, increased frequency of resistance rates, and the emergence of naturally resistant species. These treatment challenges highlight the urgency of developing new antifungal therapies, which could positively impact millions of lives each year globally. Our review offers an overview of the antifungal drugs currently available for treatment, presents the status of new antifungal drugs under clinical study, and explores ahead to future candidates that aim to help address this important global health issue.

A Convolutional Neural Network Using Anterior Segment Photos for Infectious Keratitis Identification

Purpose

To develop a comprehensively deep learning algorithm to differentiate between bacterial keratitis, fungal keratitis, non-infectious corneal lesions, and normal corneas.

Methods

This retrospective study collected slit-lamp photos of patients with bacterial keratitis, fungal keratitis, non-infectious corneal lesions, and normal cornea. Causative organisms of infectious keratitis were identified by either positive culture or clinical response to single treatment. Convolutional neural networks (ResNet50, DenseNet121, VGG19) and Ensemble with probability weighting were used to develop a deep learning algorithm. The performance including accuracy, precision, recall, F1 score, specificity and AUC has been reported.

Results

Total of 6478 photos from 2171 eyes, composed of 2400 bacterial keratitis, 1616 fungal keratitis, 1545 non-infectious corneal lesions, and 917 normal corneas were collected from hospital database. DenseNet121 demonstrated the best performance among three convolutional neural networks with the accuracy of 0.8 (95% CI 0.74-0.86). The ensemble technique showed higher performance than single algorithm with the accuracy of 0.83 (95% 0.78-0.88).

Conclusion

Convolutional neural networks with ensemble techniques provided the best performance in discriminating bacterial keratitis, fungal keratitis, non-infectious corneal lesions, and normal corneas. Our models can be used as a screening tool for non-ophthalmic health care providers and ophthalmologists for rapid provisional diagnosis of infectious keratitis.

Advances in adhesive hydrogels applied for ophthalmology: An overview focused on the treatment

Adhesive hydrogels, composed of hydrophilic polymers arranged in a three-dimensional network, have emerged as a pivotal innovation in ophthalmology due to their ability to securely adhere to ocular tissues while providing sustained therapeutic effects. The eye, with its delicate structure and specific needs, presents unique challenges for drug delivery and tissue regeneration. This review explores the transformative potential of adhesive hydrogels in addressing these challenges across a range of ocular conditions, including corneal injuries, cataracts, glaucoma, vitreoretinal disorders, and ocular trauma. By detailing the mechanisms of polymerization and adhesion, this paper highlights how these materials can be customized for specific ophthalmic applications, offering insights into their current use and future possibilities. The emphasis is placed on the clinical significance and future directions of adhesive hydrogels in advancing ophthalmic therapy, potentially revolutionizing the treatment of complex eye diseases.

Ocular infections in international travelers

INTRODUCTION

Ophthalmological conditions in international travelers may be associated with low mortality but high morbidity. Eye involvement in travelers is less frequently reported than febrile, gastrointestinal and respiratory infections, but data probably represent a degree of under-notification.

METHODS

an extensive narrative review of the main viral, bacterial, fungal and parasitic infections affecting the eye in travelers was performed.

MAIN FINDINGS

Common respiratory tract viral infections may cause ocular complications in travelers, human influenza viruses have been associated with conjunctivitis and emerging avian influenza subtypes may also affect the eye. Vector-borne viral infections may affect travelers, usually with systemic symptoms, but eye disease may be the first presenting feature. A spectrum of manifestations have been described with dengue, chikungunya and Zika infections, including conjunctivitis, anterior uveitis, posterior uveitis with chorioretinitis and macular involvement. Staphylococcus spp, Streptococcus spp, and Pseudomonas spp (especially associated with use of contact lenses) are common causes of keratitis, however, resistance patterns to antimicrobials might vary depending on area of travel. Less frequent infections, such as Burkholderia pseudomallei, associated with environmental exposure, and Bartonella spp. may rarely present with ophthalmological involvement in travelers. Fungal ocular infections, especially after ocular trauma caused by plants and contact lens use, should be considered in patients with stromal keratitis not improving with antibiotic eye drops. Parasitic eye infections tend to occur in tropical areas, but some, such as acanthamoebic keratitis or Toxoplasma spp retinitis, are found worldwide. Increasing exposure to animals, undercooked food consumption or poor hygiene during international travels might be leading to the emergence of certain parasitic eye diseases.

CONCLUSIONS

Clinical features, with identification of risk factors and geographical region of exposure, can assist in the definitive diagnosis of imported ophthalmological infections. Management of imported eye infections requires a multi-disciplinary approach involving ophthalmologists, travel medicine/infectious diseases physicians and other specialists.

The association between grade of coronary heart disease and risk of developing keratopathy: a nationwide cohort study

Purpose: To evaluate the association between coronary heart disease (CHD) severity and the risk of developing keratopathy. Method: A retrospective cohort study was conducted with data from the Taiwan National Health Insurance Research Database (NHIRD). A total of 593100, 593100 and 296500 patients were included in the control, mild CHD and severe CHD groups, respectively. The primary outcomes were the development of superficial keratopathy and infectious keratitis with antibiotic usage. Cox proportional hazard regression was used to calculate the adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs) for the primary outcomes among the groups. Results: A total of 30697, 32134, and 15977 superficial keratopathy episodes and 6021, 6010, and 2982 infectious keratitis episodes were recorded in the control, mild CHD, and severe CHD groups, respectively. The incidence of superficial keratopathy was significantly greater in the severe CHD group (P = 0.037), and both groups presented a greater risk of developing superficial keratopathy than did the control group (both P < 0.05). The cumulative incidence of superficial keratopathy was also significantly greater in the severe CHD group than in the mild CHD group (P < 0.001). In the subgroup analyses, the incidence of superficial keratopathy was significantly greater in severe CHD patients than in mild CHD patients older than 70 years, and the correlation between CHD severity and superficial keratopathy incidence was significantly greater in those older than 70 years of age (P = 0.002). Conclusions: Severe CHD is related to a greater risk of developing superficial keratopathy, especially in those older than 70 years of age.

Topical losartan ophthalmic drops - a review of corneal wound healing and topical losartan for managing corneal haze and potential future indications

Corneal haze, a consequence of pathological wound healing, manifests as opacity and sometimes irregularity impairing vision. This condition arises from breaches in the epithelial barrier, triggering an inflammatory cascade culminating in myofibroblasts formation. Surgical procedures such as photorefractive keratectomy (PRK), laser in situ keratomileusis (LASIK) and corneal cross-linking (CXL) are major contributors, alongside non-surgical causes like trauma and infections. Research has extensively explored post-surgical corneal haze, focusing on the transforming growth factor beta (TGFβ) pathway, inflammation management, and extracellular matrix remodeling. Losartan, traditionally an antihypertensive, has gained attention in ophthalmology for its anti-fibrotic and anti-inflammatory properties. Studies have supported its efficacy in reducing corneal fibrosis post-descemetorhexis, alkali burn, and PRK injuries in animal models, and human case reports. This review aims to examine the topical use of losartan 0.08% in ophthalmology, assessing its effectiveness against post-surgical corneal haze and exploring its pharmacological profile and potential future applications. We provide a systematic review of all published in-human studies of the use of topical losartan in corneal disease.

Customised 96-ocular TaqMan (iCAM) microarray PCR card for rapid diagnosis of microbial keratitis

AIM

To validate the diagnostic performance of a custom 96-micro-organism TaqMan PCR card (iCAM) for microbial keratitis (MK) from a single corneal epithelial sample.

METHODS

Patients over the age of 18 referred to Cambridge University Hospital with MK were recruited in this single-site prospective cohort study between September 2021 and January 2023. An ocular-specific, customised microarray card (iCAM) was constructed according to primer and probe nucleotide sequences developed in our department to detect bacteria, viruses, Acanthamoeba and fungi commonly implicated in MK using a single corneal epithelial sample. Part of the corneal epithelial sample was taken for conventional cultures per local protocol, followed by iCAM array. Microbial detection rate and positive predictive value (PPV) were evaluated.

RESULTS

38 corneal epithelial samples from 32 patients with MK and 4 control samples from healthy participants were obtained from 36 consecutive patients. A causative microbe was isolated in 15/34 samples (44%) using the iCAM test, compared with 15 by conventional methods (44%). iCAM test processing time varied between 6 and 24 hours compared with up to 7 days for conventional tests. Combined, the microbial detection rate was 65%, with the correlation between methods at 62%. The iCAM test could detect all major micro-organism groups with 56% sensitivity and 60% PPV.

CONCLUSIONS

The iCAM test can detect bacterial, fungal, viral and protozoan organisms using one corneal epithelial sample. The limitations include small patient cohort size and reduced volume of available corneal epithelial sample when shared between the iCAM PCR test and conventional culture methods utilised in the study. A multicentre trial is being planned to validate the clinical impact of using iCAM test on accuracy of diagnosis, early institution of appropriate antimicrobials and clinical outcomes.

TRIAL REGISTRATION NUMBER

ISRCTN17422545.

Risk Factors, Clinical Characteristics, and Antibiotic Susceptibility Patterns of Streptococcal Keratitis: An 18-Year Retrospective Study from a Tertiary Hospital in China

Purpose: Our aim was to investigate risk factors, clinical characteristics, and antibiotic susceptibility patterns of cornea-isolated Streptococcus species collected at a tertiary hospital in China over 18 years. Methods: This retrospective study reviewed data from 350 patients diagnosed with Streptococcal keratitis at Beijing Tongren Hospital between January 2006 and December 2023, including demographics, risk factors, clinical signs, in vivo confocal microscopy (IVCM) imaging, and antibiotic susceptibility testing. Results: The predominant type was Streptococcus pneumoniae (n = 108, 29.8%), followed by Streptococcus mitis (n = 90, 24.9%) and Streptococcus oralis (n = 85, 23.5%). Main risk factors included previous ocular surface disease (24.6%), ocular surgery (21.4%), and trauma (16.3%). Significant differences in clinical characteristics were observed among S. pneumoniae, S. oralis, and S. mitis regarding infiltration location (p = 0.038) and size (p = 0.037), as well as hypopyon presence (p = 0.006). IVCM revealed deeper inflammatory cell distribution and structural disruption as the disease progressed. Resistance rates of aminoglycosides, β-lactams, and fluoroquinolones have increased, with significant differences among species for amikacin (p = 0.010), gentamicin (p = 0.007), and others. Poor outcomes correlated with disease duration over one month, central corneal ulcers, dense infiltrations, hypopyon, and scar tissue presence on IVCM. Conclusions:Streptococcal keratitis is a complex ocular infection with multiple risk factors. S. pneumoniae, S. mitis, and S. oralis are the primary causative agents, exhibiting varying clinical features and antibiotic resistance patterns. Key factors associated with poor outcomes include long disease duration, central corneal ulcers, and severe infiltration.

Contact Lens Wear Alters Transcriptional Responses to Pseudomonas aeruginosa in Both the Corneal Epithelium and the Bacteria

Purpose

Healthy corneas resist colonization by virtually all microbes yet contact lens wear can predispose the cornea to sight-threatening infection with Pseudomonas aeruginosa. Here, we explored how lens wear changes corneal epithelium transcriptional responses to P. aeruginosa and its impact on bacterial gene expression.

Methods

Male and female C57BL/6J mice were fitted with a contact lens on one eye for 24 h. After lens removal, corneas were immediately challenged for 4 h with P. aeruginosa. A separate group of naïve mice were similarly challenged with bacteria. Bacteria-challenged eyes were compared to uninoculated naive controls as was lens wear alone. Total RNA-sequencing determined corneal epithelium and bacterial gene expression.

Results

Prior lens wear profoundly altered the corneal response to P. aeruginosa, including: upregulated pattern-recognition receptors (tlr3, nod1), downregulated lectin pathway of complement activation (masp1), amplified upregulation of tcf7, gpr55, ifi205, wfdc2 (immune defense) and further suppression of efemp1 (corneal stromal integrity). Without lens wear, P. aeruginosa upregulated mitochondrial and ubiquinone metabolism genes. Lens wear alone upregulated axl, grn, tcf7, gpr55 (immune defense) and downregulated Ca2+-dependent genes necab1, snx31 and npr3. P. aeruginosa exposure to prior lens wearing vs. naïve corneas upregulated bacterial genes of virulence (popD), its regulation (rsmY, PA1226) and antimicrobial resistance (arnB, oprR).

Conclusion

Prior lens wear impacts corneal epithelium gene expression altering its responses to P. aeruginosa and how P. aeruginosa responds to it favoring virulence, survival and adaptation. Impacted genes and associated networks provide avenues for research to better understand infection pathogenesis.

[Bacterial keratitis: Retrospective and prospective 2024]

Bacterial keratitis (BK) is an infection of the cornea caused by one or more bacteria. Contact lens wear is the main risk factor. Staphylococcus and Pseudomonas are the most frequently isolated pathogens in developed countries. BK requires a standardized work-up to avoid diagnostic and therapeutic delays that may negatively affect visual prognosis. Corneal signs, the speed at which lesions progress and the presence of risk factors allow the clinician to presume an empirical microbiological diagnosis, but corneal scraping, which allows the isolation and identification of the bacteria involved in the infection, is the only way to confirm the diagnosis. The type of antibiotic treatment depends on the severity of the lesions, the risk factors involved, and the bacteria identified. Corticosteroids have been shown to be effective as adjuvant therapy and may be used under certain well-defined circumstances. Surgical treatment is sometimes necessary.

Antimicrobial and antifouling hyaluronic acid-cobalt nanogel coatings built sonochemically on contact lenses

The wearing of contact lenses (CLs) may cause bacterial infections, leading in turn to more serious complications and ultimately vision impairment. In this scenario, the first step is the adhesion of tear proteins, which provide anchoring points for bacterial colonization. A possible solution is the functionalization with an antimicrobial coating, though the latter may also lead to sight obstruction and user discomfort. In this study, adipic acid dihydrazide-modified hyaluronic acid-cobalt (II) (HA-ADH-Co) nanogels (NGs) were synthesized and deposited onto commercial CLs in a single-step sonochemical process. The coating hindered up to 60 % the protein adsorption and endowed the CLs with strong antibacterial activity against major ocular pathogens like Staphylococcus aureus and Pseudomonas aeruginosa, reducing their concentration by around 3 logs. Cytotoxicity assessment with human corneal cells demonstrated viabilities above 95 %. The nanocomposite coating did not affect the optical power and the light transmission of the CLs and provided enhanced wettability, important for the wearer comfort.

Advances in Corneal Diagnostics Using Machine Learning

This paper provides comprehensive insights into the cornea and its diseases, with a particular focus on keratoconus. This paper explores the cornea's function in maintaining ocular health, detailing its anatomy, pathological conditions, and the latest developments in diagnostic techniques. Keratoconus is discussed extensively, covering its subtypes, etiology, clinical manifestations, and the application of the Q-value for quantification. Several diagnostic techniques, such as corneal topography, are crucial points of discussion. This paper also examines the use of machine learning models, specifically Decision Tree and Nearest Neighbor Analysis, which enhance the accuracy of diagnosing based on topographical corneal parameters from corneal topography. These models provide valuable insights into disease progression and aid in clinical decision making. Integrating these technologies in medical research opens promising avenues for enhanced disease detection. Our findings demonstrate the effectiveness of Decision Tree and Nearest Neighbor Analysis in classifying and predicting conditions based on corneal parameters. The Decision Tree achieved classification accuracy of 62% for training and 65.7% for testing, while Nearest Neighbor Analysis yielded 65.4% for training and 62.6% for holdout samples. These models offer valuable insights into the progression and severity of keratoconus, aiding clinicians in treatment and management decisions.

The mammalian Ire1 inhibitor, 4µ8C, exhibits broad anti-Aspergillus activity in vitro and in a treatment model of fungal keratitis

Objective

The fungal unfolded protein response consists of a two-component relay in which the ER-bound sensor, IreA, splices and activates the mRNA of the transcription factor, HacA. Previously, we demonstrated that hacA is essential for Aspergillus fumigatus virulence in a murine model of fungal keratitis (FK), suggesting the pathway could serve as a therapeutic target. Here we investigate the antifungal properties of known inhibitors of the mammalian Ire1 protein both in vitro and in a treatment model of FK.

Methods

The antifungal activity of Ire1 inhibitors was tested against conidia of several A. fumigatus isolates by a broth microdilution assay and against fungal biofilm by XTT reduction. The influence of 4μ8C on hacA mRNA splicing in A. fumigatus was assessed through gel electrophoresis and qRT-PCR of UPR regulatory genes. The toxicity and antifungal profile of 4μ8C in the cornea was assessed by applying drops to uninfected or A. fumigatus-infected corneas 3 times daily starting 4 hours post-inoculation. Corneas were evaluated daily through slit-lamp imaging and optical coherence tomography, or at endpoint through histology or fungal burden quantification via colony forming units.

Results

Among six Ire1 inhibitors screened, the endonuclease inhibitor 4μ8C displayed the strongest antifungal profile with an apparent fungicidal action. The compound both blocked conidial germination and hyphal metabolism of A. fumigatus Af293 in the same concentration range that blocked hacA splicing and UPR gene induction (60-120 µM). Topical treatment of sham-inoculated corneas with 0.5 and 2.5 mM 4μ8C did not impact corneal clarity, but did transiently inhibit epithelialization of corneal ulcers. Relative to vehicle-treated Af293-infected corneas, treatment with 0.5 and 2.5 mM drug resulted in a 50% and >90% reduction in fungal load, respectively, the latter of which corresponded to an absence of clinical signs of infection or corneal pathology.

Conclusion

The in vitro data suggest that 4μ8C displays antifungal activity against A. fumigatus through the specific inhibition of IreA. Topical application of the compound to the murine cornea can furthermore block the establishment of infection, suggesting this class of drugs can be developed as novel antifungals that improve visual outcomes in FK patients.

In Situ Forming Hydrogel Reinforced with Antibiotic-Loaded Mesoporous Silica Nanoparticles for the Treatment of Bacterial Keratitis

Bacterial keratitis (BK) is a serious ocular infection that can lead to vision impairment or blindness if not treated promptly. Herein, we report the development of a versatile composite hydrogel consisting of silk fibroin and sodium alginate, reinforced by antibiotic-loaded mesoporous silica nanoparticles (MSNs) for the treatment of BK. The drug delivery system is constructed by incorporating vancomycin- and ceftazidime-loaded MSNs into the hydrogel network. The synthesized MSNs were found to be spherical in shape with an average size of about 95 nm. The loading capacities of both drugs were approximately 45% and 43%, for vancomycin and ceftazidime respectively. Moreover, the formulation exhibited a sustained release profile, with 92% of vancomycin and 90% of ceftazidime released over a 24 h period. The cytocompatibility of the drug carrier was also confirmed by MTT assay results. In addition, we performed molecular dynamics (MD) simulations to better reflect the drug-drug and drug-MSN interactions. The results obtained from RMSD, number of contacts, and MSD analyses perfectly corroborated the experimental findings. In brief, the designed drug-MSN@hydrogel could mark an intriguing new chapter in the treatment of BK.

Ag/Cu nanoparticles-loaded glycocalyx biomimetic corneal bandage lenses for combatting bacterial keratitis

Bacterial keratitis is a major cause of blindness, hindered by the rising threat of antibiotic resistance. Although corneal bandage lenses (CBLs) are widely utilized in ophthalmic treatment, their effectiveness in treating bacterial keratitis remains limited due to risks of secondary infections, patient discomfort, and complications. In this study, we developed a novel biomimetic coating on CBLs by grafting Ag/Cu bimetallic nanoparticles (Ag/Cu-NPs) and thiol-functionalized heparin (Hep-SH) using a rapid polydopamine (PDA) deposition technique, effectively mimicking the ocular surface glycocalyx structure. The resulting Ag/Cu-NPs/Hep-SH coated CBLs (PNH-CBLs) exhibited significant antibacterial activity, with over 80 % reduction in Staphylococcus aureus (S. aureus) and 70 % in Escherichia coli (E. coli) due to the sustained release of Ag+ and Cu2+, along with displaying favorable in vitro biocompatibility. Animal experiments conducted on New Zealand white rabbits with bacterial keratitis demonstrated successful treatment therapeutic outcomes, with PNH-CBLs leading to a significant decrease in clinical score. These biomimetic lenses also exhibited selective anti-protein adsorption properties, minimizing inflammation and promoting surface lubrication. Overall, this innovative approach addresses critical challenges in antibiotic resistance and offers a promising therapeutic strategy for managing ophthalmic infectious diseases.

Advancements in Hydrogels for Corneal Healing and Tissue Engineering

Hydrogels have garnered significant attention for their versatile applications across various fields, including biomedical engineering. This review delves into the fundamentals of hydrogels, exploring their definition, properties, and classification. Hydrogels, as three-dimensional networks of crosslinked polymers, possess tunable properties such as biocompatibility, mechanical strength, and hydrophilicity, making them ideal for medical applications. Uniquely, this article offers original insights into the application of hydrogels specifically for corneal tissue engineering, bridging a gap in current research. The review further examines the anatomical and functional complexities of the cornea, highlighting the challenges associated with corneal pathologies and the current reliance on donor corneas for transplantation. Considering the global shortage of donor corneas, this review discusses the potential of hydrogel-based materials in corneal tissue engineering. Emphasis is placed on the synthesis processes, including physical and chemical crosslinking, and the integration of bioactive molecules. Stimuli-responsive hydrogels, which react to environmental triggers, are identified as promising tools for drug delivery and tissue repair. Additionally, clinical applications of hydrogels in corneal pathologies are explored, showcasing their efficacy in various trials. Finally, the review addresses the challenges of regulatory approval and the need for further research to fully realize the potential of hydrogels in corneal tissue engineering, offering a promising outlook for future developments in this field.

Effects of the COVID-19 Pandemic on Microbial Keratitis: A 5-Year Comparative Study

PURPOSE

To report the clinical and microbiological profiles of microbial keratitis and its antimicrobial resistance before, during, and after COVID-19.

METHODS

This was a retrospective case-note review of all corneal scrape specimens collected from patients with microbial keratitis from January 2018 to December 2023. Case records were analyzed for demographic characteristics, microbiological diagnosis, and antibiograms. All outcome variables were collected, stratified, and compared between 3 periods: the pre-COVID-19 group (January-December 2019), the COVID-19 group (January 2020-December 2022), and the post-COVID-19 group (January-December 2023).

RESULTS

A total of 947 corneal cultures from 947 patients were reviewed. Gram-positive bacteria predominated in all periods, with no significant differences in their distribution. Staphylococcus epidermidis was the most frequently identified organism. Pseudomonas aeruginosa was the most common Gram-negative bacterium, with its incidence significantly lower in the post-COVID period. Fungal infections showed a significant increase in the post-COVID group, with Fusarium sp. being the most common fungus and showing a significant increase in incidence in the post-COVID group.

CONCLUSIONS

Despite a stable incidence of microbial keratitis, this study highlights a concerning trend in antibiotic resistance. Although some pathogens became less common, those that persisted have become increasingly difficult to treat. Understanding the clinical and microbiological profiles of microbial keratitis and antimicrobial resistance patterns before and after the COVID-19 pandemic is crucial for informed treatment decisions.

A Tear-Based Approach for Rapid Identification of Bacterial Pathogens in Corneal Ulcers Using Nanopore Sequencing

Purpose

Corneal ulcers pose a significant threat to vision, with the need for prompt and precise pathogen identification being critical to effective treatment. This study assesses the efficacy of using next-generation portable sequencing (Nanopore Technology) to detect and identify bacterial pathogens directly from tear samples, providing a non-invasive alternative to traditional corneal scraping and culture, which are limited by high false-negative rates.

Design

Prospective observational study.

Participants

Ten participants diagnosed with corneal ulcers.

Methods

Tear samples were collected from the ocular surface using Schirmer strips. Corneal scrapings and cultures were performed as medically indicated. The 16S rRNA gene was amplified directly from the tear samples using polymerase chain reaction (PCR), and Nanopore sequencing was used for bacterial species identification and taxonomic classification. Comparative analysis was conducted to evaluate the concordance between Nanopore sequencing results and traditional culture methods.

Main Outcome Measures

Comparison of bacterial species detected via Nanopore sequencing with those identified through traditional culture methods.

Results

Bacterial DNA was identified in 8 of the 10 samples analyzed using the tear-based sequencing method. Notably, Nanopore sequencing accurately identified the causative bacteria in all 4 samples that exhibited bacterial growth on culture. Additionally, it detected bacterial pathogens in 2 of the 4 ulcers that did not show bacterial growth on culture. In 2 cases where cultures could not be obtained due to the small size of the ulcer, tear sequencing successfully identified bacterial species, highlighting potentially overlooked pathogens in corneal ulcers.

Conclusions

PCR amplification of 16S RNA directly from tears followed by Nanopore sequencing is an effective, non-invasive method to identify bacterial pathogens in corneal ulcers, offering non-inferior results to traditional culture methods. This technique not only allows for the detection of traditionally hard-to-culture organisms, providing immediate diagnostic value to guide treatment, but also enhances our understanding of the microbiological landscape of corneal ulcers, thereby informing more effective treatment strategies.