The ocular microbiome and microbiota and their effects on ocular surface pathophysiology and disorders

Ocular surface microbiome: Influences of physiological, environmental, and lifestyle factors

PURPOSE

The ocular surface (OS) microbiome is influenced by various factors and impacts on ocular health. Understanding its composition and dynamics is crucial for developing targeted interventions for ocular diseases. This study aims to identify host variables, including physiological, environmental, and lifestyle (PEL) factors, that influence the ocular microbiome composition and establish valid associations between the ocular microbiome and health outcomes.

METHODS

The 16S rRNA gene sequencing was performed on OS samples collected from 135 healthy individuals using eSwab. DNA was extracted, libraries prepared, and PCR products purified and analyzed. PEL confounding factors were identified, and a cross-validation strategy using various bioinformatics methods including Machine learning was used to identify features that classify microbial profiles.

RESULTS

Nationality, allergy, sport practice, and eyeglasses usage are significant PEL confounding factors influencing the eye microbiome. Alpha-diversity analysis revealed significant differences between Spanish and Italian subjects (p-value < 0.001), with a median Shannon index of 1.05 for Spanish subjects and 0.59 for Italian subjects. Additionally, 8 microbial genera were significantly associated with eyeglass usage. Beta-diversity analysis indicated significant differences in microbial community composition based on nationality, age, sport, and eyeglasses usage. Differential abundance analysis identified several microbial genera associated with these PEL factors. The Support Vector Machine (SVM) model for Nationality achieved an accuracy of 100%, with an AUC-ROC score of 1.0, indicating excellent performance in classifying microbial profiles.

CONCLUSION

This study underscores the importance of considering PEL factors when studying the ocular microbiome. Our findings highlight the complex interplay between environmental, lifestyle, and demographic factors in shaping the OS microbiome. Future research should further explore these interactions to develop personalized approaches for managing ocular health.

Restorative Effects of Short-Chain Fatty Acids on Corneal Homeostasis Disrupted by Antibiotic-Induced Gut Dysbiosis

The gut microbiota plays a crucial regulatory role in various physiological processes, yet its impact on corneal homeostasis remains insufficiently understood. Here, the effects of antibiotic-induced gut dysbiosis (AIGD) and germ-free conditions were investigated on circadian gene expression, barrier integrity, nerve density, and immune cell activity in the corneas of mice. Both AIGD and germ-free conditions significantly disrupted the overall transcriptomic profile and circadian transcriptomic oscillations in the cornea, as indicated by RNA sequencing. These molecular disturbances were accompanied by a reduction in corneal epithelial thickness, nerve density, corneal sensitivity, and compromised barrier function. Notably, supplementation with short-chain fatty acids (SCFAs) significantly restored corneal integrity in AIGD mice. Further single-cell sequencing revealed that SCFA receptors G-protein-coupled receptor 109A (Hcar2), olfactory receptor 78 (Olfr78), and G-protein-coupled receptor 43 (Ffar2) are expressed in corneal epithelial basal cells, embryonically derived macrophages, perivascular cells, and γδ T cells, respectively. In conclusion, this study demonstrated that the gut microbiota plays a critical role in corneal physiology by regulating circadian gene expression and maintaining barrier function. These findings enhance our understanding of the gut-eye axis, highlighting the cornea as a target for microbiota-derived metabolic signals and underlining the potential therapeutic value of SCFAs in treating corneal dysfunction.

Systems biology of dry eye: Unraveling molecular mechanisms through multi-omics integration

Dry eye disease (DED) is a multifactorial condition with complex and incompletely understood molecular mechanisms. Advances in multi-omics technologies, including genomics, transcriptomics, proteomics, metabolomics, and microbiomics, have provided new insights into the pathophysiology of DED. Genomic analyses have identified key genetic variants linked to immune regulation and lacrimal gland function. Transcriptomic studies reveal upregulated inflammatory pathways in ocular surface tissues, implicating these as core drivers of chronic inflammation. Proteomic research highlights significant alterations in tear protein composition, especially proteins involved in inflammation and tissue repair. Metabolomics studies focus on disrupted lipid metabolism and oxidative stress, which are crucial in maintaining tear film stability. Furthermore, microbiome research has demonstrated reduced microbial diversity and increased pathogenic bacteria, exacerbating inflammatory responses. The integration of multi-omics data allows for the identification of novel biomarkers and therapeutic targets, enabling precision diagnostics and personalized treatments. Therefore, this review highlights the critical importance of multi-omics approaches in deepening our understanding of DED's complex molecular mechanisms and their potential to transform clinical management and therapeutic innovations in this challenging field.

Microbiota transplantation and administration of live biotherapeutic products for the treatment of dysbiosis-associated diseases

INTRODUCTION

The microbiota composition in humans varies according to the anatomical site and is crucial for maintaining homeostasis and an overall healthy state. Several gastrointestinal, vaginal, respiratory, and skin diseases are associated with dysbiosis. Alternative therapies such as microbiota transplantation can help restore microbiota normal composition and can be implemented to treat clinically relevant diseases.

AREAS COVERED

Current microbiota transplantation therapies conducted in clinical trials were included in this review (after searching on MEDLINE database from years 2017 to 2025) such as fecal microbiota transplantation (FMT) against recurrent Clostridioides difficile infection (rCDI) and vaginal microbiota transplantation (VMT) against bacterial vaginosis. Washed microbiota transplantation (WMT) and live biotherapeutic products (LBPs) were also reviewed.

EXPERT OPINION

In microbiota-based transplantation therapy, selecting optimal donors is a limitation. A stool or a vaginal microbiota bank should be implemented to overcome the time-consuming and expensive process of donor recruitment. Microbiota-based LBPs are also promising treatment alternatives for rCDI and other dysbiosis-associated diseases. Specific LBPs could be engineered out of donor fluids-derived strains to achieve the selection of specific beneficial microorganisms for the treatment of specific dysbiosis-associated diseases. Personalized microbiota-based treatments are promising solutions for dysbiosis-associated diseases, which remains an important necessity in clinical practice.

Potential Role of Malassezia restricta in Pterygium Development

Pterygium is a condition affecting the ocular surface, marked by a triangular-shaped growth of fibrotic tissue extending from the nasal conjunctiva toward the corneal center, potentially causing visual impairment. While ultraviolet (UV )light exposure is the primary risk factor for pterygium, its underlying cause remains unclear. In order to better understand the true genesis of pterygium development, we investigated pterygium tissue and compared it with healthy conjunctiva controls. Given the eye's direct environmental exposure, we analyzed the microbiota composition using metagenomic sequencing of pterygium tissue to identify microbes potentially associated with this condition. Metagenomic sequencing revealed a higher prevalence of the fungus Malassezia restricta in five pterygium samples, confirmed by in situ hybridization. The CHIT1 gene, which plays a role in antifungal defenses, displayed the highest expression in five pterygium tissue samples compared to healthy conjunctiva controls, suggesting the potential involvement of Malassezia restricta in pterygium development. Gene expression profiling of pterygium highlighted an IL-33 and IL-4 gene expression signature, along with an increased presence of M2 macrophages, emphasizing their role in promoting fibrosis-a hallmark feature of pterygium. The detection of Malassezia restricta in the pterygium samples and associated molecular changes provides novel insights into the ocular microbiome and raises the possibility of Malassezia's involvement in pterygium pathology.

Deciphering the Transformed bacterial ocular surface microbiome in diabetic mice and its Consequential influence on corneal wound healing restoration

To obtain a profound understanding of microbiome variations and their associations with diabetic cornea wound healing, a type 1 diabetic mouse model and a corneal epithelial wound healing model were established. Corneal tissues from diabetic mice and healthy controls were collected. The 2bRAD sequencing for microbiome (2bRAD-M)technique was used to analyze the ocular microbiome profiles. Fifty-five distinct bacterial species were identified through alignment against the 2bRAD-M database. Among all the species identified on the corneal wound, 17 (30.91 %) unique species were discovered on the diabetic epithelium side, 13 (23.64 %) on the non-diabetic epithelium side, and 25 (45.45 %) species were common to both. The top five most abundant bacterial species on the non-diabetic side were Exiguobacterium sibiricum (26.50 %), Enterobacter hormaechei (13.37 %), Brevibacillus agri (6.24 %), Ralstonia sp. UNC404CL21Col (6.11 %), and Cupriavidus pauculus (5.71 %). On the diabetic side, the predominant five species were Methylobacterium sp. MB200 (38.73 %), Exiguobacterium sibiricum (11.58 %), Acinetobacter johnsonii (9.80 %), Corynebacterium glutamicum (6.46 %), and Corynebacterium stationis (5.71 %). Increased levels of gram-negative bacilli, such as Methylobacterium, in the diabetic ocular surface microbiota may be involved in the delayed healing of corneal wounds. Gatifloxacin eye drops with antibacterial activity against gram-negative bacteria were applied to the ocular surface. The corneal epithelium of diabetic mice healed more rapidly after the application of gatifloxacin eye drops. The changes in the ocular surface microbiota of diabetic corneal wounds may be related to delayed healing of the corneal epithelium in diabetic mice, providing a new research target for the investigation of this pathology.

Potential Risks of Ocular Molecular and Cellular Changes in Spaceflight

PURPOSE

Many fundamental cellular and molecular changes are known to occur in biological systems during spaceflight, including oxidative stress, DNA damage, mitochondrial damage, epigenetic factors, telomere lengthening, and microbial shifts. We can apply the consequences of these molecular changes in ocular cells, such as the retinal ganglion cells and corneal epithelium, to identify ophthalmologic risks during spaceflight. This review aims to discuss the potential molecular changes in greater detail and apply the principles to ocular cells and ophthalmic disease risk in astronauts.

METHODS

A targeted, relevant search of the literature on the topic and related topics of ocular surface and spaceflight was conducted with scholarly databases PubMed, Web of Science, and Embase from inception to July2024 with search terms "oxidative stress"; "DNA damage"; "Mitochondrial Dysfunction"; "Epigenetics"; "Telomeres"; "Microbiome"; "ocular cells"; "spaceflight"; "microgravity"; "radiation."

RESULTS

A total of 115 articles were included following screening and eligibility assessment. Key findings include molecular changes and their contributions to ophthalmic diseases like cataracts, spaceflight-associated neuro-ocular syndrome, and dry eye syndrome.

CONCLUSION

This review provides a comprehensive overview of risks to vision associated with long-duration spaceflight missions beyond low Earth orbit (LEO). Further investigation into targeted countermeasures is imperative to mitigate vision-threatening sequelae in astronauts undertaking deep-space exploration.

Antibacterial Lecithin/Chitosan Nanoparticles for the Sustained Release of Ciprofloxacin to Treat Ocular Bacterial Infections

Ocular drug-delivery is one of the most challenging areas owing to nature of ocular tissues. Various nanoformulations have been designed and investigated for drug-delivery to achieve high drug bioavailability. The major focus of these preparations available in market is to utilize nanomaterial as drug-carrier only, with less focus on developing functional-nanomaterials, which is a key knowledge gap in the field. To address this, we developed a nanoparticulate system from bioactive-polymers, having intrinsic antimicrobial and mucoadhesiveness, loaded with ciprofloxacin (cipro) to treat ocular bacterial infections. Cipro-loaded lecithin/chitosan nanoparticles were prepared and characterized for their physiochemical properties. They exhibited good drug loading efficiency and showed sustained drug-release for 72 h, with slow release for first 4 h followed by a burst release in phosphate buffered saline and simulated tear fluid. Cipro-loaded nanoparticles were assessed for their antibacterial potential against Staphylococcus aureus (96 %) and Pseudomonas aeruginosa (72 %) using optical density, disc-diffusion method, live-dead assay, and demonstrated promising antibacterial properties. The drug-loaded nanoparticles showed good cytocompatibility (~90 %) towards murine fibroblasts and rabbit corneal cells. Being amphiphilic in nature, the nanoparticles exhibited mucoadhesiveness, hemocompatibility (<4 %) and, thus, proving to be a promising candidate for treating ocular infections. This approach ensures efficient drug delivery and synergic/additive therapeutic effects.

Antibiotic-Induced dysbiosis of the ocular microbiome affects corneal circadian rhythmic activity in mice

The ocular surface microbiota plays a critical role in maintaining corneal homeostasis, but its disruption and subsequent effects on corneal functions remain poorly understood. This study investigates how antibiotic-induced microbial depletion affects the corneal circadian transcriptome in C57BL/6J mice. Dysbiosis was induced using a topical antibiotic cocktail, and RNA sequencing was employed to analyze gene expression across eight time points over 24 h. Antibiotic treatment disrupted corneal circadian rhythms, eliminating rhythmicity in 1,812 genes and introducing rhythmicity in 1,928 previously arrhythmic genes. Furthermore, epithelial adhesion was impaired, inflammation was elevated, and neural sensitivity was reduced. More than 50 % of ocular microbial genera exhibited daily oscillations, with six genera showing significant correlations with corneal rhythmic transcripts. Additionally, the administration of TLR agonists restored circadian gene expression patterns, with partial recovery of corneal barrier function and immune homeostasis, further highlighting the potential of microbiota-targeted therapies in treating ocular surface disorders. These findings underscore the critical role of the ocular microbiota in regulating corneal health and suggest that restoring microbial balance via TLR activation may offer new therapeutic avenues for eye diseases.

Characterization of Conjunctival Microflora and Antibiotic Sensitivity Patterns in Patients Undergoing Cataract Surgery

This study aims to characterize the conjunctival flora of patients scheduled for cataract surgery and determine the susceptibility profile of isolated bacteria to several commonly used topical antibiotics. Conjunctival swabs were taken from 44 consecutive patients (25 males, 19 females; mean age of 75.0 ± 12.6 years) who were scheduled for senile cataract surgery at two Italian centers before starting any prophylactic preoperative treatment. Swabs were processed for the detection of the microbial growth and for species identification. Selective culture media were used, and bacteria were identified using the MicroScan Specialty ID Panels (Beckman Coulter®, Brea, CA, USA). Antimicrobial susceptibility for the following antibiotics (netilmicin, tobramycin, ofloxacin, oxacillin, levofloxacin, moxifloxacin, chloramphenicol, cefuroxime, and azithromycin) were assessed using the Kirby-Bauer disk diffusion method. Susceptibility for oxacillin was useful to identify methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE). Among the swabs analyzed, 61.4% showed only saprophytic flora, 30.7% showed only potential pathogenic flora, and 8.0% showed mixed flora. S. epidermidis (20.5%), S. intermedius (18.2%), and S. aureus (14.8%) were the most frequent isolates; MRSA and MRSE accounted for 8.0% and 6.8% of isolates. Less frequently (9%), Gram-negative bacteria such as Pseudomonas fluorescent, Serratia marcescens, Moraxella lacunata, Morganella morgani, and Stenotrophomonas maltophila were detected. All isolated organisms showed an excellent sensitivity to moxifloxacin and chloramphenicol (range 83-100%, range 67-100%, Gram-positive sensitivity for moxifloxacin and chloramphenicol, respectively; 100% Gram-negative sensitivity for both). A significant percentage of the eyes of candidates for surgery presented potential pathogenic flora alone or in association with saprophytic organisms. Staphylococci were the most frequently isolated bacteria. Tobramycin and Ofloxacin, widely used in the ophthalmic field, are confirmed to have a reduced sensitivity in vitro.

Multi-cohort analysis identifying core ocular surface microbiome and bacterial alterations in eye diseases

PURPOSE

Inconsistency exists among reported studies on the composition of human ocular surface microbiome (OSM). The roles of OSM in ocular diseases remain uncertain. In this study, we aimed to determine the composition of OSM and to evaluate its potential roles and functions from multiple cohorts.

METHODS

Raw 16 s sequencing data were obtainable from publicly available repositories, sourced from 17 published studies. Employing a standardized method, we processed the data and conducted a cross-cohort analysis. Through bioinformatics pipelines QIIME2 and PICRUSt2, we processed a total of 1875 ocular surface samples. Core microbiome analyses, genera comparisons, and MetaCyc pathway analyses were performed within each cohort independently. The results were then combined to identify shared patterns across different datasets.

RESULTS

The core OSM comprised seven genera: Corynebacterium, Staphylococcus, Acinetobacter, Streptococcus, Pseudomonas, Cutibacterium and Bacillus. Corynebacterium and Staphylococcus are the most abundant genera on ocular surface. Most ocular diseases showed OSM alterations and eight genera demonstrated a non-specific, shared response among two or more ocular diseases. Moreover, changes in various metabolic pathways were predicted following OSM alteration, indicating potential roles of OSM in biological processes.

CONCLUSION

We refined the core OSM candidates combining multiple cohorts. The common pattern shared by different cohorts is worth further investigation. Changes in metabolic pathways based on bioinformatic analysis indicated a role of OSM on ocular diseases. Our results help extend the knowledge and encourage further investigations on the associations between OSM and ocular diseases.

Diversity and composition of ocular microbiota in contact lens wearers: Efficacy of liposomal ozonated oil

PURPOSE

To characterize the ocular surface microbiota in regular contact lens wearers with dry eyes and assess the effectiveness of reducing bacterial load using a liposomal ozonated oil solution.

METHODS

This prospective, longitudinal, controlled study randomized subjects into two groups. Group A (45 subjects) received hydroxypropylmethylcellulose (HPMC, Artific®), while Group B (41 subjects) received ozonated sunflower seed oil with soybean phospholipids (OSSO, Ozonest®). Microbial communities were analyzed via DNA metabarcoding of the 16S rRNA gene, and statistical analyses (alpha and beta diversity) were performed in R.

RESULTS

Both groups predominantly harbored Staphylococcus caprae, Streptococcus oralis, and Corynebacterium spp., with OSSO and HPMC users showing distinct bacterial profiles. Alpha diversity showed no significant differences, but beta diversity revealed differences in bacterial composition between the groups.

CONCLUSIONS

The results seem to indicate that the use of ozonized oil reduces the bacterial load compared to the solution used as a control.

[Lacrimal duct infections]

In addition to being a drainage system, the lacrimal ducts actively defend the eye through the action of the lacrimal pump, the presence of resident flora (lacriome) and the mucosa-associated immune tissue. Infection occurs when mucosal immune functions are overwhelmed. Lacrimal infection is a vicious circle, in which infection leads to inflammation and post-inflammatory sequelae, themselves a source of occlusion and stagnation, which in turn encourages infection. Whatever the initial trigger - post-traumatic occlusion, inflammation (e.g. allergic) or infestation by a virulent germ, the management of lacrimal duct infection must take account of this vicious circle. When infection sets in, changes in the mucosa can range from submucosal inflammatory infiltrates to pseudocysts, and in the most severe cases to metaplasia, dysplasia and squamous cell carcinoma. Histological sampling is therefore imperative in the case of surgery on a chronically infected mucosa. Clinical assessment, aided if necessary by a dacryoscan, must be able to detect differential diagnoses (lacrimal sac carcinoma, dacryocystocele in children) and serious forms (gonococcal ophthalmia neonatorum, peridacryocystitis), look for signs of dacryoliths, and differentiate between acute and chronic infection. Antibiotic treatment should be adapted to the identified or presumed organism involved or used sparingly in cases of chronic infection. Dacryoliths can be removed by curettage in the case of canaliculitis with concretions, but surgery is required for larger dacryoliths (canaliculotomy, or dacryocystorhinostomy in the case of lacrimal sac dacryoliths). Antibiotic prophylaxis for lacrimal surgery is recommended only in cases with associated rhinosinusitis, inflammation of the lacrimal sac, or a history of infected mucocele or dacryocystitis.

[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.

A Comparative Analysis of the Ocular Microbiome: Insights into Healthy Eyes and Anophthalmic Sockets

The purpose of this study is to characterize the ocular surface microbiota of patients with an anophthalmic cavity. An eNAT with 1 mL of Liquid Amies Medium was used to collect samples. Microbial DNA from anophthalmic socket and healthy fellow control eye samples was isolated and sequenced. Raw reads were analyzed with GAIA (v 2.02). The richness and Shannon alpha diversity metrics, as well as Bray-Curtis beta diversity and Wilcoxon signed-rank test values, were computed with R packages such as phyloseq, mia, or DESeq2 to allow for microbiome analysis. Principal coordinate analysis (PCoA) was performed using the function plotReducedDim from the R package scater. The different taxonomic profiles were described under the concept of eye community state type (ECST). The microbiomes of both eyes from 25 patients with an anophthalmic cavity were analyzed in this study. While the microbial communities of paired eyes from the same patients showed notable dissimilarity, no consistent patterns emerged when comparing healthy eyes to anophthalmic sockets. Alpha diversity values did not significantly differ between healthy eyes and anophthalmic socket samples, though there was considerable variability within each group. Notably, anophthalmic socket samples generally exhibited lower abundances of genera such as Staphylococcus, Enterococcus, Paenibacillus, and Sediminibacterium compared to their healthy counterparts. Microbial variability between healthy eyes and anophthalmic sockets may be due to anatomical differences. Further research is needed to determine whether patients without anophthalmic sockets exhibit similar microbiome patterns in both eyes.

The Ocular Microbiome: Micro-Steps Towards Macro-Shift in Targeted Treatment? A Comprehensive Review

A healthy ocular surface is inhabited by microorganisms that constitute the ocular microbiome. The core of the ocular microbiome is still a subject of debate. Numerous culture-dependent and gene sequencing studies have revealed the composition of the ocular microbiome. There was a confirmed correlation between the ocular microbiome and ocular surface homeostasis as well as between ocular dysbiosis and pathologies such as blepharitis, microbial keratitis, and conjunctivitis. However, the role of the ocular microbiome in the pathogenesis and treatment of ocular surface diseases remains unclear. This article reviews available data on the ocular microbiome and microbiota, their role in maintaining ocular homeostasis, and the impact of dysbiosis on several ophthalmic disorders. Moreover, we aimed to discuss potential treatment targets within the ocular microbiota.

Liposomal Ozonated Oil Ensures a Further Reduction in the Microbial Load Before Intravitreal Injection: the "OPERA" Study

INTRODUCTION

This was a prospective study to investigate the antimicrobial efficacy of a novel ophthalmic solution comprising ozonated sunflower oil in liposomes plus hypromellose in conjunction with liposomal foam (BlefOX), in patients undergoing intravitreal injection, in comparison to povidone iodine 5%.

METHODS

The study employed a paired-eye design with n = 195 patients and a total of n = 390 eyes divided into two groups. Conjunctival swabs were collected from both eyes of each patient at baseline (T0-3 days before the injection). The study group underwent home therapy, which included instilling two drops of an isotonic ophthalmic solution containing 0.5% ozonated sunflower oil in liposomes plus hypromellose (Ozodrop) four times daily and applying liposomal foam twice daily to the eye undergoing intravitreal injections. In contrast, the control group (contralateral eyes) received treatment with povidone iodine 5%. This treatment regimen was maintained for 3 days. At T1 (10 min before injection), all patients instilled one drop of a topical solution of povidone iodine 5% into the conjunctival sac of both eyes. After 30 seconds had elapsed, a conjunctival swab was obtained for each eye in both study groups.

RESULTS

The results, derived from conjunctival swabs, exhibited a significant reduction in the microbial load of the study group on both chocolate agar and blood agar (p ≤ 0.007). The study demonstrated that the combination of povidone iodine 5% + Ozodrop + BlefOX provides a greater reduction in microbial load than povidone iodine 5% alone on both chocolate agar (141 [72.31%] vs. 98 [50.26%], p < 0.0001) and blood agar (130 [66.67%] vs. 97 [49.74%], p = 0.0007). The combination of povidone iodine 5% + Ozodrop + BlefOX resulted in the killing of approximately 41% to 49% of bacteria compared to povidone iodine 5% alone on the chocolate agar and blood agar, respectively.

CONCLUSIONS

Liposomal ozonated oil treatment, coupled with liposomal foam, in patients undergoing intravitreal injection led to a substantial reduction in conjunctival microbial load compared to eyes treated solely with povidone iodine 5%.

Therapeutic application of decellularized porcine small intestinal submucosa scaffold in conjunctiva reconstruction

The objective of this study was to investigate the biological feasibility and surgical applicability of decellularized porcine small intestinal submucosa (DSIS) in conjunctiva reconstruction. A total of 52 Balb/c mice were included in the study. We obtained the DSIS by decellularization, evaluated the physical and biological properties of DSIS in vitro, and further evaluated the effect of surgical transplantation of DSIS scaffold in vivo. The histopathology and ultrastructural analysis results showed that the scaffold retained the integrity of the fibrous morphology while removing cells. Biomechanical analysis showed that the elongation at break of the DSIS (239.00 ± 12.51%) were better than that of natural mouse conjunctiva (170.70 ± 9.41%, P < 0.05). Moreover, in vivo experiments confirmed the excellent biocompatibility of the decellularized scaffolds. In the DSIS group, partial epithelialization occurred at day-3 after operation, and the conjunctival injury healed at day-7, which was significantly faster than that in human amniotic membrane (AM) and sham surgery (SHAM) group (P < 0.05). The number and distribution of goblet cells of transplanted DSIS were significantly better than those of the AM and SHAM groups. Consequently, the DSIS scaffold shows excellent biological characteristics and surgical applicability in the mouse conjunctival defect model, and DSIS is expected to be an alternative scaffold for conjunctival reconstruction.

The relationship between dry eye disease and human microbiota: A review of the science

A complex relationship exists between human microbiota and the risk for ophthalmic disease. While the homeostatic composition of human microbiota is still being established, including what defines dysbiosis (i.e. changes in diversity and abundance), pilot research has begun to identify the potential influence of demographics, geography, and co-morbidities on the microbiota and describe their impact on ocular health. This review specifically focuses on the scientific relationships of the human oral and gut microbiota to dry eye disease (DED), a set of conditions impacting the tear film and ocular surface. Although data are sparse and often conflict across studies, the literature generally supports associations between microbial imbalance (dysbiosis) and DED and alterations in microbial diversity and abundance to specific aspects of DED. This review examines the relevant science and mechanistic relationships linking gut and oral dysbiosis and DED. Various physiochemical factors and therapeutic approaches that alter microbiota, including medications and fecal transplants are examined in relation to DED.

Exploring the role of the ocular surface in the lung-eye axis: Insights into respiratory disease pathogenesis

Chronic respiratory diseases (CRDs) represent a significant proportion of global health burden, with a wide spectrum of varying, heterogenic conditions largely affecting the pulmonary system. Recent advances in immunology and respiratory biology have highlighted the systemic impact of these diseases, notably through the elucidation of the lung-eye axis. The current review focusses on understanding the pivotal role of the lung-eye axis in the pathogenesis and progression of chronic respiratory infections and diseases. Existing literature published on the immunological crosstalk between the eye and the lung has been reviewed. The various roles of the ocular microbiome in lung health are also explored, examining the eye as a gateway for respiratory virus transmission, and assessing the impact of environmental irritants on both ocular and respiratory systems. This novel concept emphasizes a bidirectional relationship between respiratory and ocular health, suggesting that respiratory diseases may influence ocular conditions and vice versa, whereby this conception provides a comprehensive framework for understanding the intricate axis connecting both respiratory and ocular health. These aspects underscore the need for an integrative approach in the management of chronic respiratory diseases. Future research should further elucidate the in-depth molecular mechanisms affecting this axis which would pave the path for novel diagnostics and effective therapeutic strategies.

Microbiological screening of corneas stored in organ culture medium at Lions Eye Bank of Western Australia from 2011 to 2022

PURPOSE

The purpose of this study was to analyse the contamination rate of corneal samples stored in OCM at Lions Eye Bank of Western Australia over a 12-year period.

METHODS

All OCM samples used to preserve corneas from 2011 to 2022 (inclusive) underwent microbiological testing. Samples were collected into aerobic and anaerobic culture bottles on day 3-5 of corneal preservation and 24 h after transfer to thinning medium. Samples were tested for 7 days using the BACTEC FX system. Corneas remained in quarantine until clearance was obtained.

RESULTS

From 2011 to 2022, 3009 corneas were retrieved and 2756 corneas were stored in OCM. Thirty one (1.1%) positive samples were reported, with 20 growths of bacterial origin and 11 fungal. Microbial contamination was mostly identified on day 1 of culture (77.5%). Donors of contaminated samples had a mean age of 55 years, with 17 male and 14 female donors. The highest incidence of contamination came from donors whose cause of death was cancer. Death to enucleation times of contaminated samples ranged from 3.5 to 25.5 h (mean = 13.5 ± 7.3) and death to preservation time ranged from 4.1 to 27.5 h (mean = 14.8 ± 7.2). These did not significantly differ from the average time from death to enucleation (mean = 13.9 ± 3) and death to preservation (mean = 16.3 ± 4.2) of non-contaminated samples.

CONCLUSION

Microbiological screening of corneas stored in OCM at LEBWA showed a very low rate of positive cultures with no predictive donor characteristics.

Antimicrobials and antiseptics: Lowering effect on ocular surface bacterial flora - A systematic review

Topical antimicrobials and antiseptics are used perioperatively to reduce the ocular surface bacteria flora (OSBF) that are involved in the development of post-operative infectious complications. However, their effectiveness is still a controversial topic. This systematic review, performed according to the PRISMA guidelines and registered in PROSPERO, aims to provide an overview of the efficacy of the agents currently used in peri-cataract surgery and -intravitreal injections (IVI) in lowering the OSBF. Although effective in lowering OSBF, perioperative topical antimicrobials are associated with the risk of resistance development, with no obvious additional benefit compared with topical antisepsis. Conversely, the effectiveness of topical antiseptics before cataract surgery and IVI is strongly supported. Based on the available evidence, perioperative antimicrobials are not recommended, whereas the perioperative use of antiseptics is strongly recommended as prophylactic treatment for lowering the infection due to OSBF. Post-operative antimicrobials may be considered in eyes at higher risk for infection.

How gut microbiota may impact ocular surface homeostasis and related disorders

Changes in the bacterial flora in the gut, also described as gut microbiota, are readily acknowledged to be associated with several systemic diseases, especially those with an inflammatory, neuronal, psychological or hormonal factor involved in the pathogenesis and/or the perception of the disease. Maintaining ocular surface homeostasis is also based on all these four factors, and there is accumulating evidence in the literature on the relationship between gut microbiota and ocular surface diseases. The mechanisms involved are mostly interconnected due to the interaction of central and peripheral neuronal networks, inflammatory effectors and the hormonal system. A better understanding of the influence of the gut microbiota on the maintenance of ocular surface homeostasis, and on the onset or persistence of ocular surface disorders could bring new insights and help elucidate the epidemiology and pathology of ocular surface dynamics in health and disease. Revealing the exact nature of these associations could be of paramount importance for developing a holistic approach using highly promising new therapeutic strategies targeting ocular surface diseases.

Culture- and non-culture-based approaches reveal unique features of the ocular microbiome in dry eye patients

PURPOSE

The purpose of this study was to investigate the ocular microbiome in individuals with dry eye disease and to identify features of their ocular microbiome of possible health and diagnostic significance.

METHODS

Conjunctival samples were collected from both eyes in duplicate from 91 individuals (61 dry eye, 30 healthy) and used for both culture-dependent and culture-independent analyses. Samples were either analysed using next generation sequencing (V3-V4 16S rDNA) or inoculated on a wide range of agar types and grown under a broad range of conditions to maximize recovery. Isolates were identified by partial sequencing of the 16S rDNA and rpoB genes and tested for antibiotic susceptibility. We applied a L2-regularized logistic regression model on the next generation sequencing data to investigate any potential association between severe dry eye disease and the ocular microbiome.

RESULTS

Culture-dependent analysis showed the highest number of colony forming units in healthy individuals. The majority of isolates recovered from the samples were Corynebacterium, Micrococcus sp., Staphylococcus epidermidis, and Cutibacterium acnes. Culture independent analysis revealed 24 phyla, of which Actinobacteria, Firmicutes and Proteobacteria were the most abundant. Over 405 genera were detected of which Corynebacterium was the most dominant, followed by Staphylococcus and Cutibacterium. The L2-regularized logistic regression model indicated that Blautia and Corynebacterium sp. may be associated with severe DED.

CONCLUSIONS

Our study indicates that the ocular microbiome has characteristic features in severe DED patients. Certain Corynebacterium species and Blautia are of particular interest for future studies.

Novel treatments for dry eye syndrome

Dry eye syndrome (DES) is a prevalent and multifactorial disease that leads to a self-perpetuating cycle of inflammation and damage to the ocular surface. This results in symptoms such as redness, burning, and blurred vision, which can negatively affect a patient's quality of life. While treatments are available to manage DES, they only temporarily relieve symptoms. Furthermore, long-term use of certain medications can cause harm to the ocular surface. Therefore, there is a need for safer and effective treatments for DES. This review highlights the latest advancements in DES therapy, providing valuable insights into ongoing efforts to improve patient outcomes.

Levofloxacin susceptibility of Staphylococci from conjunctiva in patients with atopic dermatitis

PURPOSE

The ocular surface in patients with atopic dermatitis (AD) is known to harbor an abundance of gram-positive cocci, particularly Staphylococcus aureus (S. aureus). This study reviewed the results of microbial cultures from the conjunctiva in AD patients, with special attention to the levofloxacin susceptibility of Staphylococci.

STUDY DESIGN

Retrospective, single-center study.

METHODS

This study involved 131 eyes of 112 Japanese patients with AD (87 men and 25 women, mean age: 40.4 ± 12.2 years) who underwent ocular surgery at Kyorin University Hospital. Bacterial isolates were collected from the conjunctival sacs in the preoperative period. Drug resistance to methicillin and levofloxacin was judged using the minimal inhibitory concentrations of oxacillin and levofloxacin determined by the broth dilution method.

RESULTS

One hundred and fifty-seven strains were identified in 103 of the 131 eyes examined. S. aureus was isolated from 74 eyes (56.5%), followed by Staphylococcus epidermidis (S. epidermidis). In S. aureus, 11 strains (14.9%) were methicillin-resistant, and 18 (24.3%) were levofloxacin-resistant. In S. epidermidis, 15 strains (26.8%) were methicillin-resistant, and 17 (30.4%) were levofloxacin-resistant. No significant differences were observed in levofloxacin susceptibility with age, sex, previous ocular surgery, or duration of previous surgery. However, logistic multivariate analysis revealed that levofloxacin-resistant Staphylococci were concurrently resistant to methicillin, suggesting multidrug resistance.

CONCLUSION

Distinctive bacterial distribution and drug resistance need consideration in the managing of ocular disorders among patients with AD.

Effects of dietary imbalances of micro- and macronutrients on the ocular microbiome and its implications in dry eye disease

Dry eye disease (DED) is a complex and multifactorial ocular surface disease affecting a large proportion of the population. There is emerging evidence of the impact of the microbiomes of the ocular surface and gut on the symptoms of DED, with many parallels being drawn to inflammatory diseases of other organ systems. A key factor involved in the promotion of healthy microbiomes, and which has been associated with ocular surface disease, is micro- and macronutrient deficiency. A comprehensive review of how these deficiencies can contribute to DED is absent from the literature. This review reports the composition of healthy ocular and gut microbiomes, and how nutrient deficiencies may impact these floral populations, with linkage to the subsequent impact on ocular health. The review highlights that vitamin B1 and iron are linked to reduced levels of butyrate, a fatty acid implicated in inflammatory conditions such as ulcerative colitis which itself is a condition known to be associated with ocular surface diseases. Vitamin B12 has been shown to have a role in maintaining gut microbial eubiosis and has been linked to the severity of dry eye symptoms. Similar beneficial effects of gut microbial eubiosis were noted with vitamin A and omega-3 polyunsaturated fatty acids. Selenium and calcium have complex interactions with the gut microbiome and have both been implicated in the development of thyroid orbitopathy. Further, diabetes mellitus is associated with ocular surface diseases and changes in the ocular microbiome. A better understanding of how changes in both the gut and eye microbiome impact DED could allow for an improved understanding of DED pathophysiology and the development of new, effective treatment strategies.

The Use of Venous Catheter and Irrigation with Povidone-Iodine 0.6% in Patients with Punctal and Proximal Canalicular Stenosis: Preliminary Report

Background: This study aimed to evaluate the safety and efficacy of povidone-iodine 0.6% (PVI) irrigation for preventing recurrence of stenosis after punctoplasty in patients with punctal and proximal canalicular stenosis treated using a venous catheter as a stent. Methods: Twenty patients were enrolled and divided into two groups. Group 1 received irrigation of 1 mL 0.6% PVI, while Group 2 received 1 mL of balanced salt solution (BSS). The patients underwent baseline, 15-, 30-, and 90-day assessments using the Ocular Surface Disease Index (OSDI) questionnaire, Symptoms Assessment in Dry Eye (SANDE), Schirmer I test, tear meniscus height (TMH), bulbar redness, meibography, and non-invasive breakup time (NIKBUT) through Keratograph 5M (Oculus, Germany). Results: At three months, both groups demonstrated statistically significant improvements in symptoms and ocular surface parameters. However, Group 1 showed statistically significant improvements in OSDI, SANDE scores, bulbar redness, and NIKBUT compared to Group 2. Additionally, no patients in Group 1 presented a recurrence of stenosis, while three patients in Group 2 demonstrated stenosis relapse at the end of the follow-up period. Conclusions: The application of a venous catheter and PVI 0.6% irrigations proved to be effective in treating proximal lacrimal duct stenosis, reducing the risk of recurrence and improving tear film stability, ocular discomfort symptoms, and ocular surface parameters.

Classical and Innovative Evidence for Therapeutic Strategies in Retinal Dysfunctions

The human retina is a complex anatomical structure that has no regenerative capacity. The pathogenesis of most retinopathies can be attributed to inflammation, with the activation of the inflammasome protein platform, and to the impact of oxidative stress on the regulation of apoptosis and autophagy/mitophagy in retinal cells. In recent years, new therapeutic approaches to treat retinopathies have been investigated. Experimental data suggest that the secretome of mesenchymal cells could reduce oxidative stress, autophagy, and the apoptosis of retinal cells, and in turn, the secretome of the latter could induce changes in mesenchymal cells. Other studies have evidenced that noncoding (nc)RNAs might be new targets for retinopathy treatment and novel disease biomarkers since a correlation has been found between ncRNA levels and retinopathies. A new field to explore is the interaction observed between the ocular and intestinal microbiota; indeed, recent findings have shown that the alteration of gut microbiota seems to be linked to ocular diseases, suggesting a gut-eye axis. To explore new therapeutical strategies for retinopathies, it is important to use proper models that can mimic the complexity of the retina. In this context, retinal organoids represent a good model for the study of the pathophysiology of the retina.

Protective Effect of Probiotics against Pseudomonas aeruginosa Infection of Human Corneal Epithelial Cells

Probiotic therapy needs consideration as an alternative strategy to prevent and possibly treat corneal infection. This study aimed to assess the preventive effect of Lactobacillus reuteri and Bifidobacterium longum subsp. infantis on reducing the infection of human corneal epithelial (HCE) cells caused by Pseudomonas aeruginosa. The probiotics' preventive effect against infection was evaluated in cell monolayers pretreated with each probiotic 1 h and 24 h prior to P. aeruginosa challenge followed by 1 h and 24 h of growth in combination. Cell adhesion, cytotoxicity, anti-inflammatory, and antinitrosative activities were evaluated. L. reuteri and B. longum adhered to HCE cells, preserved occludin tight junctions' integrity, and increased mucin production on a SkinEthicTM HCE model. Pretreatment with L. reuteri or B. longum significantly protected HCE cells from infection at 24 h, increasing cell viability at 110% (110.51 ± 5.15; p ≤ 0.05) and 137% (137.55 ± 11.97; p ≤ 0.05), respectively. Each probiotic showed anti-inflammatory and antinitrosative activities, reducing TNF-α level (p ≤ 0.001) and NOx amount (p ≤ 0.001) and reestablishing IL-10 level (p ≤ 0.001). In conclusion, this study demonstrated that L. reuteri and B. longum exert protective effects in the context of corneal infection caused by P. aeruginosa by restoring cell viability and modulating inflammatory cytokine release.

Progress in the Application of Microneedles in Eye Disorders and the Proposal of the Upgraded Microneedle with Spinule

PURPOSE

In the local administration methods for treating eye diseases, the application of microneedles has great potential due to the shortcomings of low efficacy and significant side effects of local administration preparations. This article provides ideas for the research on the application of ophthalmic microneedle in the treatment of eye diseases.

RESULTS

This article analyzes the physiological structures of the eyes, ocular diseases and its existing ocular preparations in sequence. Finally, this article reviews the development and trends of ocular microneedles in recent years, and summarizes and discusses the drugs of ocular microneedles as well as the future directions of development. At the same time, according to the inspiration of previous work, the concept of "microneedle with spinule" is proposed for the first time, and its advantages and limitations are discussed in the article.

CONCLUSIONS

At present, the application of ocular microneedles still faces multiple challenges. The aspects of auxiliary devices, appearance, the properties of the matrix materials, and preparation technology of ophthalmic microneedle are crucial for their application in the treatment of eye diseases.

Ocular mucosal homeostasis of teleost fish provides insight into the coevolution between microbiome and mucosal immunity

BACKGROUND

The visual organ plays a crucial role in sensing environmental information. However, its mucosal surfaces are constantly exposed to selective pressures from aquatic or airborne pathogens and microbial communities. Although few studies have characterized the conjunctival-associated lymphoid tissue (CALT) in the ocular mucosa (OM) of birds and mammals, little is known regarding the evolutionary origins and functions of immune defense and microbiota homeostasis of the OM in the early vertebrates.

RESULTS

Our study characterized the structure of the OM microbial ecosystem in rainbow trout (Oncorhynchus mykiss) and confirmed for the first time the presence of a diffuse mucosal-associated lymphoid tissue (MALT) in fish OM. Moreover, the microbial communities residing on the ocular mucosal surface contribute to shaping its immune environment. Interestingly, following IHNV infection, we observed robust immune responses, significant tissue damage, and microbial dysbiosis in the trout OM, particularly in the fornix conjunctiva (FC), which is characterized by the increase of pathobionts and a reduction of beneficial taxa in the relative abundance in OM. Critically, we identified a significant correlation between viral-induced immune responses and microbiome homeostasis in the OM, underscoring its key role in mucosal immunity and microbiota homeostasis.

CONCLUSIONS

Our findings suggest that immune defense and microbiota homeostasis in OM occurred concurrently in early vertebrate species, shedding light on the coevolution between microbiota and mucosal immunity. Video Abstract.

Persistent Neutrophil Infiltration and Unique Ocular Surface Microbiome Typify Dupilumab-Associated Conjunctivitis in Patients with Atopic Dermatitis

Objective

To elucidate the pathogenesis of dupilumab (Dupixent®)-associated ocular surface disease (DAOSD).

Design

Prospective single-center cohort study.

Subjects

Twenty patients with moderate-to-severe atopic dermatitis (AD) who received dupilumab and 10 age- and sex-matched healthy controls were enrolled in the study.

Methods

The study cohort underwent a thorough slit-lamp and entire-body dermatologic examination. Conjunctival swabs and smears were collected at baseline, 4 and 16 weeks after treatment initiation, and during the conjunctivitis episode. To analyse the ocular surface microbiome, 16S ribosomal RNA sequencing was performed, smears were hematoxylin and eosin stained, and serum cytokines were measured by using a multiplex immunobead assay.

Main Outcome Measures

Composition of ocular surface microbiome and cellular component as well as serum cytokine levels.

Results

Six of the 20 patients with AD developed DAOSD after dupilumab initiation; these patients responded after a delay to treatment as quantified by Eczema Area and Severity Index and Investigator's Global Assessment score. Conjunctival smears showed massive neutrophilic infiltration and serum analysis revealed increased systemic levels of neutrophil-priming proinflammatory cytokines, in particular interleukin-1β and tumor necrosis factor α, in patients with DAOSD compared with those without it. The ocular surface microbiome of patients with DAOSD was characterized by a diverse and persistent microbial colonization, particularly by Acetobacter aceti. In contrast, microbial diversity decreased in patients with AD without DAOSD after the initiation of dupilumab treatment, especially the abundance of Staphylococcus aureus. In vitro experiments substantiated the potential role of the microbiome, showing increased growth of A. aceti and decreased growth of S. aureus in presence of dupilumab.

Conclusions

Persistent neutrophilic infiltration and a unique microbial landscape on the ocular surface associated with elevated levels of systemic proinflammatory cytokines typify DAOSD.

Financial Disclosures

Proprietary or commercial disclosure may be found after the references.

[Methods for assessing the microbiological diversity of the ocular surface]

This review compares data from scientific studies on the microbial community of the ocular surface (OS) in conditionally healthy individuals using cultural methods (including culture-dependent diagnostic tests), microscopic and molecular genetic methods, and assesses the influence of research methods and sample preparation on the results. Concordance and discordance of the sets of identified microorganisms were analyzed using overlapping and non-overlapping methods of studying the microbial community of a healthy OS. The article presents tables showing the names of microorganisms that were identified in different sources. Cross-verification in taxa of different ranks helped confirm the following most frequently found microorganisms on healthy OS: coccomorphic microorganisms of the genera Staphylococcus, Micrococcus, Kocuria, Streptococcus, Enterococcus; gram-positive spore-forming bacilli of the genera Bacillus and Paenibacillus; gram-positive non-spore-forming rod-shaped bacteria, including Corynebacterium, but excluding Propionibacterium and Microbacterium; gram-negative non-spore-forming rod-shaped microorganisms of the genera Moraxella and Serratia. The study also assessed the effect of wearing soft contact lenses on the composition of the microbial community of the OS.

Alterations of conjunctival microbiota associated with orthokeratology lens wearing in myopic children

BACKGROUND

Orthokeratology (OK) lens wear increases the risk of bacterial infection, but little is known about the microbiota of the conjunctival sac in myopic children wearing OK lenses. This study aimed to investigate the changes of conjunctival microbiota in children after treatment with OK lenses using 16 S rDNA sequencing.

METHODS

Twenty-eight myopic children who had been continuously wearing OK lenses for 12 to 13 months were enrolled in this prospective study. Twenty-two gender- and age-matched myopic children who had not worn OK lenses or discontinued OK lens wear at least 1 year ago were recruited as controls. Conjunctival swabs from each participant were collected for exploration of the microbiota profiles, targeting the V3-V4 regions of the 16 S rRNA gene by MiSeq sequencing. The differences in the microbial community structure and diversity were also compared between groups.

RESULTS

The bacterial alpha diversity indices in the OK lens group were not different from those in the non-wearer group (P > 0.05, Wilcoxon test), while beta diversity examined using principle coordinate analysis of unweighted UniFrac divided the two groups into different clusters. Proteobacteria, Bacteroidetes, and Firmicutes were the abundant phyla in the conjunctival sac microbiota in both groups (P < 0.05, Mann-Whitney U test). Among children in the OK lens group, the Linear discriminant analysis Effect Size identified the compositional changes in OK lens-associated bacteria. Key functional genera such as Blautia, Parasutterella, and Muribaculum were enriched, whereas Brevundimonas, Acinetobacter, Proteus, and Agathobacter decreased significantly (P < 0.05, Mann-Whitney U test). Phylogenetic investigation of communities by reconstruction of unobserved states also showed altered bacterial metabolic pathways in OK lens-associated microbiota. Moreover, using receiver operating characteristic curves, Brevundimonas, Acinetobacter, Proteus, and Agathobacter alone (the area under the curve was all > 0.7500) or in combination (the area under the curve was 0.9058) were revealed to discriminate OK lens wearers from controls.

CONCLUSIONS

The relative abundance of the microbial community in the conjunctival sac of myopic children can alter after OK lens wear. Brevundimonas, Acinetobacter, Proteus, and Agathobacter may be candidate biomarkers to distinguish between OK lens wearers and non-wearers.

Alterations to the bovine bacterial ocular surface microbiome in the context of infectious bovine keratoconjunctivitis

BACKGROUND

Infectious bovine keratoconjunctivitis (IBK) is a common cause of morbidity in cattle, resulting in significant economic losses. This study aimed to characterize the bovine bacterial ocular surface microbiome (OSM) through conjunctival swab samples from Normal eyes and eyes with naturally acquired, active IBK across populations of cattle using a three-part approach, including bacterial culture, relative abundance (RA, 16 S rRNA gene sequencing), and semi-quantitative random forest modeling (real-time polymerase chain reaction (RT-PCR)).

RESULTS

Conjunctival swab samples were obtained from eyes individually classified as Normal (n = 376) or IBK (n = 228) based on clinical signs. Cattle unaffected by IBK and the unaffected eye in cattle with contralateral IBK were used to obtain Normal eye samples. Moraxella bovis was cultured from similar proportions of IBK (7/228, 3.07%) and Normal eyes (1/159, 0.63%) (p = 0.1481). Moraxella bovoculi was cultured more frequently (p < 0.0001) in IBK (59/228, 25.88%) than Normal (7/159, 4.40%) eyes. RA (via 16 S rRNA gene sequencing) of Actinobacteriota was significantly higher in Normal eyes (p = 0.0045). Corynebacterium variabile and Corynebacterium stationis (Actinobacteriota) were detected at significantly higher RA (p = 0.0008, p = 0.0025 respectively) in Normal eyes. Rothia nasimurium (Actinobacteriota) was detected at significantly higher RA in IBK eyes (p < 0.0001). Alpha-diversity index was not significantly different between IBK and Normal eyes (p > 0.05). Alpha-diversity indices for geographic location (p < 0.001), age (p < 0.0001), sex (p < 0.05) and breed (p < 0.01) and beta-diversity indices for geographic location (p < 0.001), disease status (p < 0.01), age (p < 0.001), sex (p < 0.001) and breed (p < 0.001) were significantly different between groups. Modeling of RT-PCR values reliably categorized the microbiome of IBK and Normal eyes; primers for Moraxella bovoculi, Moraxella bovis, and Staphylococcus spp. were consistently the most significant canonical variables in these models.

CONCLUSIONS

The results provide further evidence that multiple elements of the bovine bacterial OSM are altered in the context of IBK, indicating the involvement of a variety of bacteria in addition to Moraxella bovis, including Moraxella bovoculi and R. nasimurium, among others. Actinobacteriota RA is altered in IBK, providing possible opportunities for novel therapeutic interventions. While RT-PCR modeling provided limited further support for the involvement of Moraxella bovis in IBK, this was not overtly reflected in culture or RA results. Results also highlight the influence of geographic location and breed type (dairy or beef) on the bovine bacterial OSM. RT-PCR modeling reliably categorized samples as IBK or Normal.

Temporal dynamics and composition of ocular surface microbiota in C57BL/6J mice: uncovering a 12h ultradian rhythm

Purpose

This study aimed to investigate the presence of rhythmic fluctuations in the composition, abundance, and functions of commensal core bacteria on the ocular surface of C57BL/6J mice.

Methods

Male C57BL/6J mice, aged 12 weeks, were subjected to a 12-hour light/12-hour dark cycle. Ocular surface tissue samples were collected at four time points (ZT) over a 24-hour period at six-hour intervals. The core ocular surface microbiota's oscillation cycles and frequencies were assessed using 16S rRNA gene sequencing targeting the V3-V4 region, along with the JTK_CYCLE algorithm. Functional predictions of these bacteria were conducted using PICRUSt2.

Results

Deep sequencing of the ocular surface microbiota highlighted the high abundance of commensal bacteria, with Proteobacteria, Actinobacteriota, and Firmicutes collectively constituting over 90% of the total sample abundance. Among the 22 core bacterial genera, 11 exhibited robust 12-hour rhythms, including Halomonas, Pelagibacterium, Pseudomonas, Nesterenkonia, norank_f_Hyphomonadaceae, Stenotrophomonas, Anoxybacillus, Acinetobacter, Zoogloea, Brevibacillus, and Ralstonia. Further taxonomic analysis indicated significant intra-cluster similarities and inter-cluster differences at the order, family, and genus levels during ZT0/12 and ZT6/18. Community interaction networks and functional prediction analyses revealed synchronized 12-hour rhythmic oscillations in neural, immune, metabolic, and other pathways associated with symbiotic bacteria.

Conclusion

This study demonstrates the presence of ultradian rhythmic oscillations in commensal bacteria on the ocular surface of normal C57BL/6J mice, with a 12-hour cycle. These findings suggest a crucial role for ultradian rhythms in maintaining ocular surface homeostasis in the host.

The Microbiome, Ocular Surface, and Corneal Disorders

The ocular surface microbiome is an emerging field of study that seeks to understand how the community of microorganisms found on the ocular surface may help maintain homeostasis or can potentially lead to disease and dysbiosis. Initial questions include whether the organisms detected on the ocular surface inhabit that ecological niche and, if so, whether there exists a core microbiome found in most or all healthy eyes. Many questions have emerged around whether novel organisms and/or a redistribution of organisms play a role in disease pathogenesis, response to therapies, or convalescence. Although there is much enthusiasm about this topic, the ocular surface microbiome is a new field with many technical challenges. These challenges are discussed in this review as well as a need for standardization to adequately compare studies and advance the field. In addition, this review summarizes the current research on the microbiome of various ocular surface diseases and how these findings may impact treatments and clinical decision-making.

Ocular surface microbiota dysbiosis contributes to the high prevalence of dry eye disease in diabetic patients

People with diabetes mellitus (DM) are at an increased risk for developing dry eye disease (DED). However, the mechanisms underlying this phenomenon remain unclear. Recent studies have found that the ocular surface microbiota (OSM) differs significantly between patients with DED and healthy people, suggesting that OSM dysbiosis may contribute to the pathogenesis of DED. This hypothesis provides a new possible explanation for why diabetic patients have a higher prevalence of DED than healthy people. The high-glucose environment and the subsequent pathological changes on the ocular surface can cause OSM dysbiosis. The unbalanced microbiota then promotes ocular surface inflammation and alters tear composition, which disturbs the homeostasis of the ocular surface. This "high glucose-OSM dysbiosis" pathway in the pathogenesis of DED with DM (DM-DED) is discussed in this review.

Ocular Surface Microbiota in Naïve Keratoconus: A Multicenter Validation Study

In the field of Ophthalmology, the mNGS 16S rRNA sequencing method of studying the microbiota and ocular microbiome is gaining more and more weight in the scientific community. This study aims to characterize the ocular microbiota of patients diagnosed with keratoconus who have not undergone any prior surgical treatment using the mNGS 16S rRNA sequencing method. Samples of naïve keratoconus patients were collected with an eNAT with 1 mL of Liquid Amies Medium (Copan Brescia, Italy), and DNA was extracted and analyzed with 16S NGS. The microbiota analysis showed a relative abundance of microorganisms at the phylum level in each sample collected from 38 patients with KC and 167 healthy controls. A comparison between healthy control and keratoconus samples identified two genera unique to keratoconus, Pelomonas and Ralstonia. Our findings suggest that alterations in the microbiota may play a role in the complex scenario of KC development.

Contact lenses and ocular dysbiosis, from the transitory to the pathological

Normal ocular microbiota is composed of different Gram-negative and positive bacterial communities that act as commensals on the ocular surface. An imbalance in the homeostasis of the native species or dysbiosis triggers functional alterations that can eventually lead to ocular conditions, indicating the use of contact lenses as the most relevant predisposing factor. Through a bibliographic review that added scientific articles published between 2018 and 2022, the relationship between healthy ocular microbiota and dysbiosis associated with the use of contact lenses that trigger ocular conditions was analyzed. The ocular microbiota in healthy individuals is mainly composed of bacteria from the phyla: Proteobacteria, Actinobacteria and Firmicutes. These bacterial communities associated with the use of contact lenses develop dysbiosis, observing an increase in certain genera such as Staphylococcus spp. and Pseudomonas spp., which under normal conditions are commensals of the ocular surface, but as their abundance is increased, they condition the appearance of various ocular conditions such as corneal infiltrative events, bacterial keratitis and corneal ulcer. These pathologies tend to evolve rapidly, which, added to late detection and treatment, can lead to a poor visual prognosis. It is suggested that professionals in the ophthalmology area learn about the composition of the communities of microorganisms that make up this ocular microbiota, in order to correctly distinguish and identify the causative agent, thereby providing a adequate and effective treatment to the user.

Conjunctival microbiome changes in soft contact lens users and contact lens discomfort patients

INTRODUCTION

Contact lens discomfort (CLD) acts as a challenging problem, and the associated conjunctival microbiome changes were unclear.

MATERIAL AND METHODS

Conjunctival sac swab samples were collected from 12 eyes of nonwearers (NW), 12 eyes of asymptomatic contact lens (ACL) wearers, and 11 eyes of CLD. The V3-V4 region of the 16S rRNA gene sequencing was used to investigate differences among three groups.

RESULTS

No differences in alpha diversity were observed among the three groups. The beta diversity showed a distinct microbiome composition between ACL and CLD group (P = 0.018) with principal coordinate analysis. The relative abundance of Firmicutes was significantly higher in CLD (48.18%) than in ACL (13.21%) group (P = 0.018). The abundance of Bacillus in patients with ACL (0.05%) or with CLD (0.02%) were significantly lower than that in the NW (1.27%) group (P = 0.024, 0.028, respectively). Moreover, the abundance of Firmicutes was positively correlated with the OSDI scores in CLD patients (r = 0.817, P < 0. 01, Spearman).

DISCUSSIONS

Patients with CLD have various degrees of bacterial microbiota imbalance in the conjunctival sac, compared with NW and ACL groups.

CONCLUSION

Firmicutes may serve as a potential biomarker for the CLD patients.

Effects of Carboxymethylcellulose Artificial Tears on Ocular Surface Microbiome Diversity and Composition, A Randomized Controlled Trial

Purpose

Carboxymethylcellulose is an artificial tear ingredient known to decrease gut microbiome diversity when ingested. This study examines the effect of carboxymethylcellulose on ocular surface microbiome diversity and composition.

Methods

Healthy adult participants without significant ophthalmic disease or concurrent carboxymethylcellulose artificial tear use were allocated randomly to take carboxymethylcellulose or control polyethylene glycol artificial tears for seven days. Conjunctival swabs were collected before and after artificial tear treatment. This trial is registered at clinicaltrials.gov (NCT05292755). Primary outcomes included abundance of bacterial taxa and microbiome diversity as measured by the Chao-1 richness estimate, Shannon's phylogenetic diversity index, and UniFrac analysis. Secondary outcomes included Ocular Surface Disease Index scores and artificial tear compliance.

Results

Of the 80 enrolled participants, 66 completed the trial. Neither intervention affected Chao-1 richness (analysis of variance [ANOVA], P = 0.231) or Shannon's diversity index (ANOVA, P = 0.224). Microbiome samples did not separate by time point (permutation multivariate analysis of variance [PERMANOVA], P = 0.223) or intervention group (PERMANOVA, P = 0.668). LEfSe taxonomic analysis revealed that carboxymethylcellulose depleted several taxa including Bacteroides and Lachnoclostridium, but enriched Enterobacteriaceae, Citrobacter, and Gordonia. Both interventions decreased OSDI scores (Wilcoxon signed rank test, P < 0.05), but there was no significant difference between interventions (Mann-Whitney U, P = 0.54).

Conclusions

Carboxymethylcellulose artificial tears increased Actinobacteriota but decreased Bacteroides and Firmicutes bacteria. Carboxymethylcellulose artificial tears do not affect ocular surface microbiome diversity and are not significantly more effective than polyethylene glycol artificial tears for dry eye treatment.

Translational Relevance

The 16S microbiome analysis has revealed small changes in the ocular surface microbiome associated with artificial tear use.

Impact of Exposomes on Ocular Surface Diseases

Ocular surface diseases (OSDs) are significant causes of ocular morbidity, and are often associated with chronic inflammation, redness, irritation, discomfort, and pain. In severe OSDs, loss of vision can result from ocular surface failure, characterised by limbal stem cell deficiencies, corneal vascularisation, corneal opacification, and surface keratinisation. External and internal exposomes are measures of environmental factors that individuals are exposed to, and have been increasingly studied for their impact on ocular surface diseases. External exposomes consist of external environmental factors such as dust, pollution, and stress; internal exposomes consist of the surface microbiome, gut microflora, and oxidative stress. Concerning internal exposomes, alterations in the commensal ocular surface microbiome of patients with OSDs are increasingly reported due to advancements in metagenomics using next-generation sequencing. Changes in the microbiome may be a consequence of the underlying disease processes or may have a role in the pathogenesis of OSDs. Understanding the changes in the ocular surface microbiome and the impact of various other exposomes may also help to establish the causative factors underlying ocular surface inflammation and scarring, the hallmarks of OSDs. This review provides a summary of the current evidence on exposomes in various OSDs.

TFOS Lifestyle: Impact of nutrition on the ocular surface

Nutrients, required by human bodies to perform life-sustaining functions, are obtained from the diet. They are broadly classified into macronutrients (carbohydrates, lipids, and proteins), micronutrients (vitamins and minerals) and water. All nutrients serve as a source of energy, provide structural support to the body and/or regulate the chemical processes of the body. Food and drinks also consist of non-nutrients that may be beneficial (e.g., antioxidants) or harmful (e.g., dyes or preservatives added to processed foods) to the body and the ocular surface. There is also a complex interplay between systemic disorders and an individual's nutritional status. Changes in the gut microbiome may lead to alterations at the ocular surface. Poor nutrition may exacerbate select systemic conditions. Similarly, certain systemic conditions may affect the uptake, processing and distribution of nutrients by the body. These disorders may lead to deficiencies in micro- and macro-nutrients that are important in maintaining ocular surface health. Medications used to treat these conditions may also cause ocular surface changes. The prevalence of nutrition-related chronic diseases is climbing worldwide. This report sought to review the evidence supporting the impact of nutrition on the ocular surface, either directly or as a consequence of the chronic diseases that result. To address a key question, a systematic review investigated the effects of intentional food restriction on ocular surface health; of the 25 included studies, most investigated Ramadan fasting (56%), followed by bariatric surgery (16%), anorexia nervosa (16%), but none were judged to be of high quality, with no randomized-controlled trials.

Cutibacterium (Formerly Propionibacterium ) acnes Keratitis: A Review

ABSTRACT

Infectious keratitis is a devastating cause of vision loss worldwide. Cutibacterium acnes ( C. acnes ), a commensal bacterium of the skin and ocular surface, is an underrecognized but important cause of bacterial keratitis. This review presents the most comprehensive and up-to-date information for clinicians regarding the risk factors, incidence, diagnosis, management, and prognosis of C. acnes keratitis (CAK). Risk factors are similar to those of general bacterial keratitis and include contact lens use, past ocular surgery, and trauma. The incidence of CAK may be approximately 10%, ranging from 5% to 25% in growth-positive cultures. Accurate diagnosis requires anaerobic blood agar and a long incubation period (≥7 days). Typical clinical presentation includes small (<2 mm) ulcerations with deep stromal infiltrate causing an anterior chamber cell reaction. Small, peripheral lesions are usually resolved, and patients recover a high visual acuity. Severe infections causing VA of 20/200 or worse are common and often do not significantly improve even after treatment. Vancomycin is considered the most potent antibiotic against CAK, although other antibiotics such as moxifloxacin and ceftazidime are more commonly used as first-line treatment.

Azelaic acid and guanosine in tears improve discrimination of proliferative from non-proliferative diabetic retinopathy in type-2 diabetes patients: A tear metabolomics study

Background

Diabetic retinopathy (DR) is the microvascular ocular complication of diabetes mellitus (DM), which can lead to irreversible blindness and visual impairment if not properly treated. Tears can be collected non-invasively, and the compositions of tears could be the potential biomarkers for ocular diseases. Here we aimed to delineate the metabolomics signature in tears collected from Chinese type-2 DM patients with DR.

Methods

The metabolomics profiles of tear samples from 41 Chinese type-2 DM patients with DR and 21 non-diabetic subjects were determined by the untargeted liquid chromatography-mass spectrometry. The associated pathways of the differentially abundant metabolites were delineated, and the receiver operating characteristic curve analysis was conducted to identify the metabolites differentiating non-proliferative DR (NPDR) from proliferative DR (PDR).

Results

Total 14 differentially abundant metabolites were identified between total DR and non-diabetic subjects, and 17 differentially abundant metabolites were found between the NPDR and PDR subjects. Moreover, total 18 differentially abundant metabolites were identified between the NPDR and PDR subjects with stratification in DR duration and blood glucose level. d-Glutamine and d-glutamate metabolism was significantly highlighted in the PDR group as compared to the non-diabetic group. For the predictive performance, azelaic acid combined with guanosine achieved the area under receiver operating characteristic curve of 0.855 in the comparison between NPDR and PDR groups.

Conclusion

This study revealed the metabolomics changes in tear samples of DR patients. The metabolites in tears could be the potential biomarkers in the DR analysis.

Comparison of Conjunctival Sac Microbiome between Low and High Myopic Eyes

Microbial communities played a vital role in maintaining homeostasis of ocular surface. However, no studies explored the myopia-associated conjunctiva microbiota changes until now. In this study, conjunctival sac swab specimens were collected from 12 eyes of low myopia (LM), and 14 eyes of high myopia (HM) patients. The V3-V4 region of the 16S rRNA gene was amplified and then sequenced. Statistical analysis was performed to investigate differences in the taxonomy and diversity between two groups. Compared to LM, higher Ocular Surface Disease Index (OSDI) scores were observed in HM group. The Shannon index of the HM was lower than that of the LM group (P = 0.017). Principle coordinate analysis and Partial Least Squares Discrimination Analysis showed distinct microbiome composition between two groups. At the phylum level, there were higher relative abundances of Proteobacteria (68.27% vs 38.51%) and lower abundances of Actinobacteria (3.71% vs 9.19%) in HM, compared to LM group (P = 0.031, 0.010, respectively). At the genus level, the abundances of Acinetobacter in HM (18.16%) were significantly higher than the LM (6.52%) group (P = 0.011). Actinobacteria levels were negatively correlated with the myopic spherical equivalent and OSDI scores. Moreover, positive correlations were found between Proteobacteria levels and OSDI scores, Acinetobacter levels were positively correlated with myopic spherical equivalent and OSDI scores. In conclusion, HM Patients have bacterial microbiota imbalance in the conjunctival sac, compared with LM patients. Proteobacteria, Actinobacteria, Acinetobacter may play roles in the HM associated ocular surface irritation.