Biological functions of tear film

Rodent models for dry eye syndrome (DES)

Dry eye syndrome (DES) is a range of ophthalmic conditions characterized by compromised tear film homeostasis, resulting from various pathological factors and primarily manifesting as ocular discomfort and impaired ocular surface integrity. With the rise in screen time due to modern lifestyles, the prevalence of DES is increasing annually, posing a significant global public health challenge. Pathophysiologically, DES involves damage to the lacrimal functional unit (LFU), including the lacrimal glands, meibomian glands, and corneoconjunctival epithelium, highlighting its multifactorial etiology. Current treatments mainly focus on artificial tears for moisture replacement and anti-inflammatory therapies, but both are limited. Consequently, animal models are crucial for understanding the complex pathological mechanisms of DES and identifying potential therapeutic agents. Rodent eyes, with their structural and physiological similarities to human eyes and cost-effectiveness, have become widely used in DES research. This manuscript reviews the current understanding of DES pathogenesis and rodent models, discussing their strengths, weaknesses, and relevant genetic models. The aim is to furnish critical insights and provide a scholarly resource to propel future investigative endeavors into the pathogenesis of and therapy for DES.

Modeling diabetic epitheliopathy using 3D-Organotypic corneal epithelium

Diabetic keratopathy (DK) is a degenerative corneal disease occurring in more than 50 % of diabetic patients. DK is correlated with the hyperglycemic state causing morphological and functional changes in corneal layers. Currently, most studies on the cornea are performed on two-dimensional (2D) cultures in vitro or animal models. Although 2D culture models can provide large amounts of data at low cost, they poorly represent the complex pathophysiology of the human cornea and hardly predict in vivo responses that can be achieved with animal model studies. However, the use of the latter presents ethical problems. Therefore, it is necessary to identify new strategies and models that can integrate the information validly and effectively, to reduce the number of animals used. Here, we used human corneal epithelial cells (hCECs) derived from donor cornea differentiated into three-dimensional (3D)-organotypic air-liquid interface (ALI), which resemble the features of the corneal epithelium. The 3D-organotypic ALI corneal epithelium was subjected to high-glucose conditions to generate a model of diabetic epitheliopathy. Our model showed well-established molecular and cellular characteristics of this pathology, such as epithelial defects and inflammation, with increased expression of IL-1β, TNF-α, p-NF-kB, COX-2, MMP-2 and MMP-9. The data provided highlight the utility of 3D-organotypic corneal epithelium in modeling diabetic epitheliopathy, offering new avenues in drug screening, as well as in precision and personalized medicine.

MicroRNAs in Corneal Diseases: Emerging Roles as Biomarkers, Regulators, and Therapeutics

MicroRNAs (miRNAs) are conserved, short, non-coding RNAs that play a crucial role in regulating gene expression. Emerging evidence suggests that miRNAs are closely involved in the pathophysiology of various corneal diseases, particularly in regulating corneal wound healing, inflammation and neovascularization. In this review, we summarized the recent progress of miRNAs in corneal diseases, especially focused on their application as diagnostic biomarkers, regulators of cell biology, and therapeutic targets. Recent advances in miRNA detection technology have made it possible to analyze minimal miRNAs in samples such as tears or exosomes, further enhancing the ability to identify disease-specific miRNA profiles and providing potential objective indicators for the early diagnosis of disease. Meanwhile, we summarized the mechanisms and pathways of multiple miRNAs in regulating various biological processes of corneal cells, as well as the advantages of studying miRNA compared to proteins or genes. Furthermore, we explore the potential of miRNAs-based therapies, especially introduce various miRNA delivery systems and challenges associated with clinical translation. This review highlights the need for further research to harness the full potential of miRNAs in treating various corneal diseases.

Evaluating the initial and end-of-day wettability of contemporary daily disposable contact lenses using various in vitro methods

SIGNIFICANCE

Contact lens wettability is potentially correlated with friction, which is linked to lens comfort. However, measuring wettability can be highly variable. This study assessed wettability using three techniques for a more accurate profile.

PURPOSE

To evaluate the wettability of contemporary daily disposable contact lenses after 16 hours on an in vitro model using the sessile drop, captive bubble, and a novel in vitro noninvasive keratograph breakup time (NIKBUT) method.

METHODS

The wettability of six contemporary silicone hydrogel contact lens materials (verofilcon A, delefilcon A, senofilcon A, kalifilcon A, stenfilcon A, and somofilcon A) and two conventional hydrogel materials (nesofilcon A and etafilcon A) were evaluated using an in vitro blink model at t = 0 and 16 hours. The blink rates of the eye model were 20 blinks per minute. Sessile drop and captive bubble angles were analyzed using the Optical Contact Analyzer. NIKBUT was assessed on a blink model in combination with the OCULUS Keratograph 5M.

RESULTS

There were no significant differences in wettability for any lens types between 0 and 16 hours when assessed using the captive bubble or NIKBUT methods (p>0.05). For the sessile drop method, verofilcon A had the lowest contact angle values (36.5 ± 2.9°), and all lenses except for etafilcon A had similar wettability after 16 hours. All the lenses had similar wettability when assessed using the captive bubble method, suggesting that they had similar wettability under optimal wetting conditions. For NIKBUT, delefilcon A had the longest NIKBUT values (9.0 ± 1.0 s) after 16 hours.

CONCLUSIONS

The sessile drop technique produced the most measurable differences in wettability between different lens types, whereas the captive bubble technique was not able to provide any measurable differences between lenses. NIKBUT measurements may provide a better measure of on-eye wettability, but variability in the results using the current eye model still needs to be addressed in future studies for improved repeatability. Although the contact lenses showed different contact angles and NIKBUT results, their in vitro wettability did not significantly change over the 16 hours of simulated wear in terms of the captive bubble or NIKBUT values.

Thioflavin T Lasing Probe for Mucin Detection in Simulated Tears as a Targeting Strategy for Brain Tumors

A novel optical approach for a noninvasive detection of mucins in tear fluid is proposed, aiming at the early diagnosis of brain tumors such as glioblastoma. Utilizing Thioflavin T (ThT) as a fluorescent probe, our study demonstrates that ThT selectively binds to mucins (modeled by MUC3) in DEMI water, artificial tears, and simulated tears. Steady-state and time-resolved fluorescence spectroscopy reveal that mucin binding induces a significant enhancement in ThT fluorescence and prolonged emission lifetime, indicative of restricted intramolecular rotation. Importantly, the application of Fabry-Pérot cavity lasing spectroscopy enabled the resolution of distinct spectral signatures of the ThT-mucin complex, including the emergence of dual lasing peaks and an increased lasing threshold in mucin-rich samples compared to controls. These optical fingerprints provide compelling evidence of specific ThT-mucin interactions that are not discernible with conventional fluorescence techniques. Our findings highlight the potential of the ThT probe and lasing method as a sensitive, noninvasive platform for detecting mucins in tears, offering a promising strategy for the early detection of glioblastoma.

Evaluation of the tear film and meibomian glands before and after cataract surgery by the ocular surface analyzer

PURPOSE

The aim of this study was to assess the tear film and meibomian gland function before and after cataract surgery using the Lacrydiag ocular surface analyzer.

METHODS

This was an observational prospective study including 34 eyes that underwent phacoemulsification at the Ophthalmology Department of Menoufia University Hospital from October 2023 to January 2024. The patients were evaluated pre-operatively as well as 1 week, 1 month, and 3 months postoperatively. Dry eye symptoms were assessed using the Ocular Surface Disease Index (OSDI) questionnaire. Traditional tear break up time (TBUT) was performed as well as Schirmer I test. The Lacrydiag Ocular Surface Analyzer was used for assessment of the tear film and meibomian glands.

RESULTS

Ocular surface analyzer evaluations revealed statistically significant changes at 1 week, 1 month, and 3 months after surgery in comparison to the values before surgery. Significant reductions were observed in non-invasive tear break-up time (NITBUT) and tear meniscus height, as well as in Schirmer's test without anesthesia, and fluorescein break-up time at each postoperative interval. Some improvements were observed at 1 month and 3 months, however, measurements did not return to the initial preoperative levels. Ocular Surface Disease Index (OSDI) scores significantly increased after 1 week, 1 month, and 3 months post-surgery compared to preoperative levels. The proportion of meibomian gland area loss did not significantly increase after surgery (no structural alterations were noted).

CONCLUSION

The study shows that phacoemulsification impacts both tear quantity and quality, affecting overall tear film stability and ocular surface health.

Mucus and mucin: changes in the mucus barrier in disease states

In this review we discuss mucus, the viscoelastic secretion from goblet or mucous producing cells that covers and protects all non-keratinized wet epithelial surfaces. In addition to the surface of organs directly contacting with the external environment such as the eyes, this layer provides protection to the underlying gastrointestinal, respiratory and female reproductive tracts by trapping pathogens, irritants, environmental fine particles and potentially harmful foreign substances. Mucins, the primary structural components of mucus, form structurally different mucus layers at different sites in a process regulated by a variety of factors. Currently, more and more studies have shown that the mucus barrier is not only closely related to various intestinal mucus diseases, but also involved in the occurrence and development of various airway diseases and mucus-related diseases, thus it may become a new target for the treatment of various related diseases in the future. Since the dysfunction of the mucous layer is closely related to various pathological processes, in-depth understanding of its molecular mechanism and physiological role is of great theoretical and practical significance for disease prevention and treatment. Here, we discuss different aspects of the mucus layer by focusing on its chemical composition, synthetic pathways, and some of the characteristics of the mucus layer in physiological and pathological situations.

The ocular surface tear film as a biomarker for systemic health

The tear film is a complex structure with rich interactions with the human body. A growing body of evidence suggests that measuring changes in protein, lipid, or other metabolite concentration in the tear film can be used to help detect disease. Particularly in the era of precision medicine, the tear film serves as a promising source of non-invasive insights into systemic health for early diagnosis and treatment. This paper analyzes the latest research in tear film biomarkers for systemic diseases. The review was conducted through PubMed and Embase databases using the PRISMA protocol and includes 54 articles. This paper first reviews the anatomy and physiology of tear film, as well as the latest proteomic analysis techniques on the tear film. We then provide a disease-by-disease review on the tear film as a biomarker including 5 articles related to Alzheimer's Disease, 10 articles related to Cancers, 1 article related to Cystic Fibrosis, 1 article related to Migraines, 4 articles related to Multiple Sclerosis, 15 articles related to Parkinson's Disease, 7 articles related to Rheumatoid Arthritis, and 11 articles related to Thyroid Disease. This paper highlights the promising results of these studies yet also reviews the challenges with limited sample sizes, reproducibility, and biological understanding of biomarkers. We conclude this paper with insights for future work to ensure clinical validity and generalizability. Ultimately, the tear film is a clinically accessible, complex structure that provides a wealth of information that may contribute to a more comprehensive understanding of systemic health.

Identification of a translatable animal model for dry eye disease using comparative analysis of tear proteins across species

PURPOSE

This study aimed to assess the similarity of tear proteins between experimental animals and humans to identify the most translational animal model for dry eye disease (DED).

METHODS

Eleven species were selected for a structural and physicochemical comparison of healthy human tear fluid proteins involved in DED. Amino acid sequences were compared using BLAST. Protein primary structure, isoelectric point (pI) and grand average of hydropathicity (GRAVY) were determined using ExPASy and compared with humans.

RESULTS

Among non-primate mammals, the cat (69.7 %) and pig (68.7 %) showed the highest protein sequence similarity to humans. The ruminants and cat showed amino acid content changes for the highest number of proteins (≥3/15). The pig, rabbit, dog and rodents had the closest global pI values to humans, while the cat showed the highest protein number (9/15) with pI values far from humans. GRAVY values for the pig and dog were the closest to humans. Tear-soluble factor study revealed that the pig was the only species with high similarity for all proteins (>60 %). Amino acid content was similar for most species compared to humans, except mouse for IL-6 and rodents and pig for IL-8. The pI and GRAVY values varied across species, though the pig and sheep were the only ones with similar pI to humans for four out of five factors.

CONCLUSION

The pig exhibited the highest similarity to humans in tear protein analysis among non-primate mammals, suggesting that the porcine model may be the most translational for DED research.

Delayed effects of the relative humidity on the outpatient visits of dry eye disease in Shanghai, China: effect modification by green and blue space

Background

Few studies have examined the influence of relative humidity (RH) on dry eye disease (DED), particularly in the context of the urban environment. The objective of this study was to investigate the influence of RH on the frequency of outpatient visits for DED among patients residing in diverse urban settings.

Methods

Data pertaining to outpatient visits, together with data on the DED, meteorological factors and air pollutants in Shanghai for the period 2019-2023, were retrieved. To analyse the nonlinear connection and lag impact between RH and outpatient visits for DED patients, a distributed lag nonlinear model (DLNM) was fitted.

Results

A total of 159 832 cases were utilised for the investigation. The results of the single-day lag pattern demonstrated a significant correlation between elevated RH exposure and DED. Lower RH was a substantial risk factor for DED on the basis of the cumulative-day effect pattern. Male were more susceptible to DED, and patients aged 0-18 years presented more stable performance in response to RH influences. In the cumulative-day lag pattern, the green space groups, the RR of the >60 years subgroup was greater than that of the other subgroups, and in the blue space groups, the RR of the 19-60 subgroup of blue space low was higher than that of the blue space high.

Conclusions

Reduced RH increases the relative risk of DED outpatient visits and suggests that a specific disease burden is associated with low RH exposure. Additionally, green and blue spaces in urban areas influence RH, which in turn affects the outpatient visits of DED at different ages.

Impact of signs and symptoms of dry eye disease on health-related quality of life: a cross-sectional population study among older adults

PURPOSE

To assess the relationship between quality of life (QoL) and ocular surface health within a Finnish population-based cohort.

METHODS

A cross-sectional study involved 601 individuals born between the years 1933-1956. Ocular surface health and dry eye disease (DED) were clinically evaluated using several diagnostic tests. Participants completed the Ocular Surface Disease Index (OSDI), QoL assessment with the 15D and Medical Outcomes Study 36-Item Short Form Health Survey (SF-36), and the Beck's Depression Inventory (BDI-II) questionnaires. Various statistical methods were employed to explore the associations between QoL, ocular surface health, and sex disparities.

RESULTS

DED had negative impact on QoL in all participants, and especially in women. Adjusted for comorbidities, DED doubled the odds of worse health-related QoL (15D: OR = 2.31 [95% CI: 1.24-4.31, p < 0.01]) and mental health (SF-36 MCS and BDI-II: OR = 2.08 [95% CI: 1.04-4.16, p < 0.05]). Noninvasive tear break-up time (NIBUT) correlated with all QoL scores. In women, the most significant clinical signs correlating with low QoL were NIBUT (15D: r = 0.20, p = 0.002; SF-36 MCS: r = 0.18, p = 0.026), and conjunctival staining (15D: r=-0.19, p = 0.004; BDI-II: r = 0.27, p < 0.001), whereas in men, blepharitis correlated with depression score (BDI-II: r = 0.20, p = 0.036). High OSDI was associated with worse QoL in women, but not in men.

CONCLUSION

This first population-based study assessing general QoL data with objective clinical measures of DED indicated that among elderly population, both symptoms and signs of DED independently impacted different aspects of QoL. In addition, significant sex-differences in these associations were observed and should be considered both in research settings and when assessing and treating people with DED.

Stability of BTI Devices for Plasma Rich in Growth Factors (PRGF) Eye Drop Delivery Under Varying Storage and Handling Conditions

Purpose: To evaluate the sterility and biological functionality of platelet lysate eye drops stored in BTI ophthalmic devices for PRGF delivery under different storage conditions and simulated use scenarios. Methods: Eye drops were prepared using platelet lysate and stored in BTI tubes under three different conditions: ≤-15 °C, 2-8 °C, and room temperature (RT) for 72 h. Simulated use was performed for 72 h with controlled drop dispensing. Bacterial contamination was assessed according to European Pharmacopoeia sterility testing principles. The biological activity of the eye drops was assessed using in vitro proliferation assays with primary human keratocytes (HKs) and human corneal epithelial cells (HCEs). Statistical analyses were performed to compare the effects of different storage conditions and application scenarios. Results: No bacterial contamination was detected in platelet lysate eye drops stored under any of the conditions tested, regardless of simulated use. Proliferation assays showed that eye drops enhanced the growth of HK and HCE cells compared to the control medium. No significant differences in proliferation were observed between storage conditions. Conclusions: Platelet lysate eye drops maintain sterility and biological functionality when stored in BTI ophthalmic devices at ≤-15 °C, 2-8 °C and RT for up to 72 h of simulated use. These results support the feasibility of using BTI eye drop devices in clinical settings while ensuring safety and efficacy.

A comprehensive scoping review of methodological approaches and clinical applications of tear fluid biomarkers

Tear fluid is an emerging source of disease biomarkers, drawing attention due to its quick, inexpensive, and non-invasive collection. The advancements in detection techniques enable the measurement of ultra-low biomarker levels from small sample volumes typical of tear fluid. The lack of standardized protocols for collection, processing, and analysis of tear fluid remains a significant challenge. To address this, we convened the Tear Research Network Review Taskforce in 2022 to review protocols from the past three decades, providing a comprehensive overview of the methodologies used in tear fluid biomarker research. A total of 1484 articles published from January 1974 to May 2024 from two electronic databases, Embase and Ovid MEDLINE, were reviewed. An exponential increase in the number of articles on tear fluid biomarkers was observed from 2015 onwards. The two most commonly reported collection methods were; glass capillaries (45.2%), and Schirmer's strips (25%), with glass capillary tube collection remaining the most frequent method until 2019, when Schirmer's strips became the leading method. Most articles analyzed tear fluid proteins (65%) and focused on a single analyte (32.3%). In recent years, an increase was observed in the type and number of examined analytes. The differences in the reported methodologies and protocols underscore the need for standardization and harmonization within the field of tear fluid biomarkers to minimize methodological differences and reduce variability in clinical outcomes. Consistent and detailed reporting is essential for improving the reproducibility and validity of tear fluid studies, in order to advance their potential clinical applications.

Validation of an Automated Cell Counter Method for HLA-DR and CD3 Expression in Cells Obtained from Low Volume Human Tears

Background/Objectives: Tears are a promising source of biomarkers reflecting both ocular and systemic conditions. However, small sample volumes and low cell yields pose technical challenges in analytical workflows. This study aimed to evaluate the feasibility of quantifying total cell counts and characterizing HLA-DR and CD3 expression in tear-derived cells using an automated cell counter with fluorescence detection (Countess 3 FL). Methods: Tears were collected from 31 patients, centrifuged and the resulting pellet was incubated with HLA-DR and CD3 antibodies, markers of inflammation and T lymphocytes, respectively. Data obtained from Countess 3 FL were compared with conventional flow cytometry and immunofluorescence. For technical performance analysis, precision and reproducibility of cell count and staining were measured. For method validation, an in vitro model of hyperosmolar stress was assessed by culturing conjunctival epithelial cells (CCL20.2) with 350 or 450 mOsm NaCl. Results: The total cell yield in each tear sample correlated with the tear surnatant volume, in a range of 1-40μL (mean total cell number: 1.3 ± 1.1 × 104, correlation analysis with tear volume: r = 0.47, p < 0.05). HLA-DR and CD3 were detected in all samples, with a mean value, respectively, of 43.6% (±21.0) and 25.0% (±15.0) intensity. Data were comparable to those obtained from standard flow cytometry analysis.HLA-DR increase in CCL20.2 exposed to hyperosmolar stress was recorded using Countess 3FL reading, confirming the detection capacity of the proposed method. Conclusions: The automated cell counter can provide HLA-DR and CD3 quantification in tear cell samples, despite the high variability and the low volume availability of tear samples. Method standardization and technical improvements are necessary to strengthen this application in the clinical setting.

A first-in-human, prospective pilot trial of umbilical cord-derived mesenchymal stem cell eye drops therapy for patients with refractory non-Sjögren's and Sjögren's syndrome dry eye disease

BACKGROUND

Patients with refractory dry eye disease (DED) often face the threat of diminished visual quality and have limited responses to existing treatments. Ocular injection of Mesenchymal stem cells (MSCs) has recently emerged as a promising new therapeutic strategy for DED. Topical eye drops are the clinical favorable choice for drug administration in DED. To date, the clinical use of MSC eye drops has not been reported in settings. This clinical trial represents a groundbreaking exploration into the preliminary therapeutic potential and safety of umbilical cord MSC eye drops for patients with refractory DED, including both non-Sjögren's dry eye (NSDE) and Sjögren's syndrome dry eye (SSDE). The study also aimed to investigate the possible underlying mechanisms.

METHODS

In this open-label, prospective, single-arm, self-controlled trial, 11 NSDE and 5 SSDE patients received twice-daily MSC eye drops for two weeks, subsequent follow-up visits were scheduled at 4 weeks and 12 months after treatment. The primary efficacy was evaluated using the ocular surface disease index (OSDI) score, tear meniscus height (TMH), non-invasive break-up time (NIBUT), Schirmer I test (SIT), and corneal fluorescein staining (CFS) score. Secondary assessments focused on the evaluation of lipid layer, meibomian gland function, and bulbar conjunctival redness. Safety was monitored by recording adverse events (AEs) throughout the study. Changes in tear levels of interleukin-6 (IL-6), IL-17A, Mucin 5AC (MUC5AC), C-C chemokine ligand 20 (CCL20) and IL-23, along with proteomic alterations, were compared between baseline and T-week2.

RESULTS

Significant clinical improvements were observed in most symptoms and signs following MSC eye drops treatment in both NSDE and SSDE patients, particularly in tear production as measured by SIT and TMH, and the alleviation of meibomian gland blockage. The therapeutic effect on OSDI, NIBUT, and the lipid layer was more pronounced in NSDE patients compared to SSDE. No serious AEs were reported during the treatment and follow-up period. Post-treatment reductions in tear levels of IL-6 and IL-17A, along with an increase in MUC5AC, further confirmed the efficacy. Tear proteomic analysis indicated that the efficacy of MSC eye drops is associated with the inhibition of inflammation caused by T helper 17 (Th17) cells in both NSDE and SSDE groups.

CONCLUSIONS

In this prospective exploratory clinical study, we have demonstrated that MSC eye drops might offer clinical efficacy and manageable safety in treating refractory DED for the first time, potentially bringing a new perspective on the treatment of such patients. Our research represents a preliminary exploratory endeavor, paving the way for future large-scale randomized positive-controlled trials.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT05784519. Registered 28 February 2023, https://clinicaltrials.gov/study/NCT05784519 .

Sex Differences in the Lacrimal Gland: Implications for Dry Eye Disease

Sexual dimorphism significantly impacts the lacrimal gland's structure, function, and ageing processes, playing an important role in dry eye disease (DED) pathophysiology. This multifactorial disorder, characterised by tear film instability, inflammation, and visual impairment, disproportionately affects women, especially after menopause. It highlights the interplay between sex steroid hormones, lacrimal gland function, and environmental factors. Systemic and local androgens are vital for maintaining lacrimal gland health and tear production, while the role of oestrogens remains less clear. Evidence suggests dose and context-dependent effects on inflammation and glandular function. Histopathological and molecular studies reveal significant sex differences in the lacrimal gland, with women exhibiting more pronounced age-related degenerative changes, including fibrosis and acinar atrophy, contributing to their increased susceptibility to DED. Despite these findings, the underlying mechanisms connecting sex steroid hormones, receptor expression, and local tissue regulation to these disparities remain poorly understood, highlighting the need for further research. This review synthesises the current knowledge of sex-specific differences in the lacrimal gland, emphasising the importance of integrating systemic and local biomarkers, histological data, and molecular insights into personalised therapeutic strategies. By tailoring treatments to patients' unique hormonal and molecular profiles, personalised medicine has the potential to transform DED management, addressing unmet clinical needs and improving outcomes.

A pilot study of morphological features of the eyelid margin with conjunctival goblet cells and MUC5AC in tear film of dry eye

PURPOSE

This study aimed to investigate the morphological features of eyelid margin in dry eye patients and determine their correlations with conjunctival goblet cells, MUC5AC secretion, and clinical tests of tear film.

METHODS

Patients diagnosed with dry eye disease (DED) were asked to complete the evaluations of symptoms and signs of dry eye, including Ocular Surface Disease Index (OSDI) questionnaire, Lipid layer thickness (LLT), partial blinking (PB) rate, tear-film breakup time (TBUT), Schirmer's I test (SIt), and meiboscore. Marx line (ML), lid wiper epitheliopathy (LWE), and meibomian orifices (MOs) were used as indicators of morphological features of the eyelid margin. PAS staining of conjunctival goblet cells and MUC5AC measurement of the tear samples were also performed.

RESULTS

A total of 30 patients diagnosed with DED were included. The ML score was correlated with the SIt. The MOs showed a significant negative correlation with the TBUT and LLT. The LWE was corrected to TBUT and meiboscore, and also associated with decreased conjunctival goblet cell density and MUC5AC concentration in the tear film rather than ML and MOs in the eyelid margin of dry eye patients. The tear MUC5AC concentration had a significant positive correlation with conjunctival goblet cell density.

CONCLUSION

The eyelid margin is crucial for maintaining the integrity of tear film and ocular surface. Attracting more attention to the eyelid margin is beneficial to routine clinical practice, and lid wipers could be used to evaluate the secretion of MUC5AC in the tear film secreted by conjunctival goblet cells.

Immediate Effects of Light Mode and Dark Mode Features on Visual Fatigue in Tablet Users

Background: Prolonged tablet use can cause visual fatigue, dry eye, and changes in critical flicker frequency, affecting visual comfort and performance. While the light and dark mode features aim to reduce eye strain, their immediate effects on these issues remain unclear. Objective: To compare the immediate effects of light and dark mode features on visual fatigue in tablet users. Methods: This experimental study involved 30 female tablet users. The participants were randomly assigned using a block randomization method to use both light and dark mode features. Visual fatigue, critical flicker frequency, and dry eye symptoms were measured before and after exposure to each mode. Results: No statistically significant difference in visual fatigue was observed between the two modes (p > 0.05). However, a statistically significant difference was found in critical flicker frequency (p < 0.05) and dry eye symptoms (p < 0.05) between the two modes. Furthermore, visual fatigue, critical flicker frequency, and dry eye symptoms significantly increased after tablet use in both modes (p < 0.05). Conclusions: Both light and dark mode features impact visual fatigue, critical flicker frequency, and dry eye symptoms. However, the dark mode may help reduce the risk of eye fatigue compared to the light mode. Further studies are recommended to explore the long-term effects and optimize screen settings for visual comfort.

[Cellular models used to study the pathogenesis associated with ocular inflammation in the anterior part of the eye]

Several multifactorial pathologies in ophthalmology that affect the anterior segment of the eye are partly inflammatory. To better understand the role and impact of inflammation in dry eye and corneal healing, many research teams have used in vitro models to mimic different aspects of these diseases. Several in vitro models have been developed to elucidate the signaling cascades involved in pathogenesis. They also offer the experimental flexibility to adjust environmental parameters, facilitating the validation of innovative therapies and the identification of new pharmacological targets. This review focuses on two-dimensional in vitro models, but also highlights the progress made in 3D models obtained by tissue engineering, which mimic inflammation in these ocular pathologies. The origin of the cells (human or animal), their tissue source, the type of cells (epithelial, endothelial, vascular, conjunctival), as well as the various experimental conditions used to mimic an inflammatory aspect according to the stages of progression of these pathologies, are thoroughly reported in this review of the literature.

Corneal Sensory Nerve Injury Disrupts Lacrimal Gland Function by Altering Circadian Rhythms in Mice

Purpose

To investigate the impact of corneal sensory nerve injury on lacrimal gland function, focusing on mechanisms involving the superior salivatory nucleus (SSN), circadian rhythm disruption, immune microenvironment alterations, and the potential for neural regeneration.

Methods

A murine model of corneal sensory nerve injury was used to assess lacrimal gland function, with tear secretion measured using the phenol red thread test. Transcriptomic analysis of lacrimal glands examined circadian rhythm and immune-related gene expression. Basic fibroblast growth factor (bFGF) was used to promote corneal nerve regeneration, and its effects on tear secretion and nerve repair were evaluated.

Results

Corneal nerve injury resulted in a 35% reduction in tear secretion and significantly impaired SSN activity, as evidenced by a 31% decrease in c-FOS-positive neurons in choline acetyltransferase (ChAT)-expressing neurons. Transcriptomic analysis revealed significant downregulation of immune-related pathways, including Toll-like receptor (TLR), NOD-like receptor (NLR), and T-cell receptor signaling. Circadian rhythm gene expression exhibited phase shifts, with a 2.13-hour delay in peak expression and a substantial change in the number and types of rhythmic genes, which were enriched in different signaling pathways. The bFGF treatment restored tear secretion by 22% and promoted nerve regeneration, although nerve fiber density remained 74% lower than that of controls.

Conclusions

Corneal sensory nerve injury disrupts both central and peripheral circadian clock functions in the lacrimal gland, leading to reduced tear secretion and immune dysregulation. These findings highlight the novel role of circadian rhythms and neural-immune interactions in lacrimal gland dysfunction. Neural regeneration strategies, such as bFGF, offer therapeutic potential for dry eye syndrome, providing new directions for clinical intervention.

The Human Cornea: Unraveling Its Structural, Chemical, and Biochemical Complexities

The cornea, the transparent part of the anterior eye, is vital for light refraction and vision. This review examines the intricate chemical and biochemical interactions essential for maintaining corneal transparency and highlights significant advancements in corneal biology. The cornea comprises five layers: the epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium, each contributing uniquely to its structure and function. The epithelium, maintained by limbal stem cells, serves as a barrier and interacts with the tear film to maintain ocular surface health. The stroma, abundant in organized collagen fibrils and regulated by proteoglycans, is crucial for corneal clarity and biomechanical integrity, whereas the endothelium regulates corneal hydration and nutrition. Recent imaging advances have improved visualization of these molecular structures, enhancing our understanding of collagen organization and cross-linking. Proteoglycans such as decorin and lumican regulate collagen spacing and hydration, directly influencing corneal clarity. Biochemical processes within the cornea involve signaling molecules, growth factors, and cytokines, which are essential for wound healing, inflammation, and injury response. Despite progress, questions remain regarding corneal wound healing mechanisms, the impact of oxidative stress, and the roles of microRNAs. This review synthesizes recent discoveries to advance our understanding of corneal physiology and biochemical functions.

Novel protocol for metabolomics data normalization and biomarker discovery in human tears

OBJECTIVES

Human tear analysis holds promise for biomarker discovery, but its clinical utility is hindered by the lack of standardized reference values, limiting interindividual comparisons. This study aimed at developing a protocol for normalizing metabolomic data from human tears, enhancing its potential for biomarker identification.

METHODS

Tear metabolomic profiling was conducted on 103 donors (64 females, 39 males, aged 18-82 years) without ocular pathology, using the AbsoluteIDQ™ p180 Kit for targeted metabolomics. A predictive normalization model incorporating age, sex, and fasting time was developed to correct for interindividual variability. Key metabolites from six compound families (amino acids, biogenic amines, acylcarnitines, lysophosphatidylcholines, phosphatidylcholines, and sphingomyelins) were identified as normalization references. The approach was validated using Linear Discriminant Analysis (LDA) to test its ability to classify donor sex based on metabolite concentrations.

RESULTS

Metabolite concentrations exhibited significant interindividual variability. The normalization model, which predicted metabolite concentrations based on a reference "concomitant" metabolite from each compound family, successfully reduced this variability. Using the ratio of observed-to-predicted concentrations, the model enabled robust comparisons across individuals. LDA classification of donor sex using acylcarnitine C4 achieved 78 % accuracy, correctly identifying 92 % of female donors. This approach outperformed traditional statistical and machine learning methods (Lasso logistic regression and Random Forest classification) in sex discrimination based on tear metabolomics.

CONCLUSIONS

This novel normalization protocol significantly improves the reliability of tear metabolomics by enabling standardized interindividual comparisons. The approach facilitates biomarker discovery by mitigating variability in metabolite concentrations and may be extended to other biological fluids, enhancing its applicability in precision medicine.

Absorption of Toxicants from the Ocular Surface: Potential Applications in Toxicology

In relation to the eye, the body can absorb substances from the ocular surface fluid (OSF) in a few ways: directly through the conjunctival sac, through the nasal mucosa as the fluid drains into the nose, or through ingestion. Regardless of the absorption method, fluid from the conjunctival sac should be used as a toxicological matrix, even though only small quantities are needed. Contemporary analytical techniques make it a suitable matrix for toxicological research. Analyzing small quantities of the matrix and nano-quantities of the analyte requires high-cost, sophisticated tools, which is particularly relevant in the high-throughput environment of new drug or cosmetics testing. Environmental toxicology also presents a challenge, as many pollutants can enter the system using the same ocular surface route. A review of the existing literature was conducted to assess potential applications in clinical and forensic toxicology related to the absorption of toxicants from the ocular surface. The selection of the studies used in this review aimed to identify new, more efficient, and cost-effective analytical technology and diagnostic methods.

A Bioengineered Model of the Human Cornea for Preclinical Assessment of Human Ocular Exposure to Environmental Toxicants

Here a bioengineered platform is introduced to investigate adverse effects of environmental materials on the human cornea. Using primary cells, this system is capable of reproducing the differentiated corneal epithelium and its underlying stroma in the human eye, which can then be treated with externally applied solid, liquid, or gaseous substances in a controlled manner and under physiologically relevant conditions. The proof-of-principle of how this system can be used to simulate human ocular exposure to different classes of environmental toxicants for direct visualization and quantitative analysis of their potential to induce acute corneal injury and inflammation is demonstrated. This model can also be further engineered to create an electromechanically actuated array of multiple human corneal tissues that can emulate spontaneous eye blinking. Using this advanced system, it is shown that blinking-like mechanical motions may play a protective role against adverse effects of environmental toxicants. This work yields an immediately deployable in vitro technology for screening ocular toxicity of existing and emerging environmental materials of various types and may enable the development of more realistic, human-relevant preclinical toxicology models complementary to traditional animal testing.

Lymphocyte Subpopulations in the Healthy Human Lacrimal Gland and Their Variations With Age and Sex, Systematic Review 1960-2023

BACKGROUND

Immunosenescence has been associated with an imbalance in the lacrimal functional unit and histopathological changes in exocrine glands, especially in women.

OBJECTIVE

To define the main lymphocyte subpopulations in the human lacrimal gland and their variations with age and sex, according to scientific articles published between 1960 and 2023.

METHODS

A systematic review was performed on PubMed, ScienceDirect, and Google Scholar. The PRISMA 2020 guidelines were applied for the search and selection of studies. The methodological quality was evaluated with the STROBE guidelines. A meta-analysis of three selected articles dichotomizing lymphocytic infiltrates according to age group was also performed.

RESULTS

We selected 20 observational studies, including 774 healthy individuals (722 cadavers). The articles evaluated the lymphocyte infiltration with hematoxylin and eosin staining, immunohistochemistry and immunofluorescence. There was high variability in the criteria to define the apparently human lacrimal and to quantify the lymphocytic infiltration. There was an underrepresentation of individuals younger than 40 years (12.6%), and female sex (38.9%). Three articles reported an association of age and sex with lymphocytic infiltration in the healthy lacrimal gland, while two articles did not. Plasma cells were the most abundant lymphocyte subpopulation in the healthy lacrimal gland, including IgA-containing plasma cells. B cells were reported to be very scarce in the LG in two articles. In the meta-analysis of three selected articles, no statistical difference in lymphocytic infiltration was found between individuals younger and older than 60.

CONCLUSION

There is the need of further observational studies, better defining the study design, with similar representation across sex and ages to ascertain what are the changes of lymphocytic composition in the lacrimal gland related to age and sex. Further studies are also needed to assess the dynamics of lymphocytic populations in a more detailed manner using cutting-edge methodologies such as single-cell sequencing or transcriptomics.

TRIAL REGISTRATION

PROSPERO 2023 CRD42023435653 Available from: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023435653.

Optimizing instilled drug delivery: a scoping review of microdrops in ophthalmology

Eyedrop instillation constitutes the most commonly used ocular drug delivery method that serves for both diagnostic and therapeutic purposes. Ocular disposition and bioavailability of instilled drugs depend on the anatomy and physiology of the ocular surface as well as the physicochemical properties of the active agent. Intraocular bioavailability is positively associated with the amount of drug available onto the ocular surface and the precorneal residence time. Concerns are raised regarding systemic absorption of the instilled drugs intraocularly, percutaneously, via the conjunctiva, through the nasolacrimal system, or through the nasal, oral, and gastrointestinal mucosa. Special considerations exist regarding the anatomical features and the limited pharmacokinetic data on the pediatric population that complicate further the efficacy and systemic toxicity of the instilled medications. Both preclinical and clinical studies propose the reduction of the instilled drop volume, in the form of microdrops, as a means to enhance intraocular bioavailability of topically applied drugs, while minimizing patient discomfort and systemic adverse events. We summarize existing data on the clinical application of microdrops in a wide age range, from preterm infants to elderly adults. Studies regarding microdrops of mydriatics and ocular hypotensives show promising results in optimizing the provided everyday care.

Tribology in Nature: Inspirations for Advanced Lubrication Materials

Friction-induced energy consumption is a significant global concern, driving researchers to explore advanced lubrication materials. In nature, lubrication is vital for the life cycle of animals, plants, and humans, playing key roles in movement, predation, and decomposition. After billions of years of evolution, natural lubrication exhibits remarkable professionalism, high efficiency, durability, and intelligence, offering valuable insights for designing advanced lubrication materials. This review focuses on the lubrication mechanisms of natural organisms and significant advancements in biomimetic soft matter lubrication materials. It begins by summarizing common biological lubrication behaviors and their underlying mechanisms, followed by current design strategies for biomimetic soft matter lubrication materials. The review then outlines the development and performance of these materials based on different mechanisms and strategies. Finally, it discusses potential research directions and prospects for soft matter lubrication materials. This review will be a valuable resource for advancing research in biomimetic lubrication materials.

Mucin1 N-domain variant contributes to dry eye syndrome in diabetes by increasing immature mucus secretory granules

BACKGROUND

Diabetes-associated dry eye syndrome (DMDES) affects 20-54 % of diabetes, leading to ocular irritation and blurry vision. Decreased conjunctival goblet cell mucus secretion is one of the major pathological processes of DMDES. This study aims to investigate the mechanism of mucus granule maturation and secretion disturbance in DMDES.

METHODS

Tear samples from diabetic patients with and without dry eye syndrome were analyzed by mass spectrometry to identify proteins associated with ocular mucous layer reduction. The N-terminal domain fragment of Mucin1 (MUC1-ND) was transfected into the mouse conjunctiva to investigate alterations in goblet cell mucus secretion. Protein localization and granule morphology were explored through transmission electron microscopy with colloidal gold labeling and immunohistochemistry. Immunofluorescence, co-immunoprecipitation, and integrative computational modeling of protein interactions were employed to explore protein-protein interactions.

RESULTS

Tear proteomic analysis revealed significantly elevated MUC1-ND levels in tears from DMDES patients, which correlated with reduced goblet cell mucus secretion and tear film instability. Upregulation of MUC1-ND in mice conjunctiva inhibited the maturation of secretory mucus granules, contributing to tear mucous layer reduction. Protein docking and co-immunoprecipitation analysis demonstrated that the binding of MUC1-ND and Syntaxin6 prevents granule fusion and maintains the immature state of secretory granules, which leads to reduced mucus secretion.

CONCLUSION

In DMDES, MUC1-ND binds with Syntaxin6 to disrupt the fusion and maturation of secretory mucus granules in conjunctival goblet cells, which provides a new insight into DMDES pathophysiology.

Mass spectrometric detection of keratins in tear fluid

PURPOSE

Keratin contamination is a common problem in mass spectrometry proteomic analyses, particularly in bottom-up mass spectrometry. The purpose of this study was to determine the protein contaminants introduced during the proteomic analysis of tear fluid.

METHODS

Human tear fluid samples were collected using Schirmer strips. Proteomic analyses were performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) on blank Schirmer strips and tear fluid samples, with empty vials serving as controls for assessing environmental contaminant proteins.

RESULTS

We detected 26 contaminant proteins (18 keratins and 8 non-keratins). 98.2% of the total protein contamination can be attributed to the 9 keratins, including KRT10 (23.6%), KRT1 (23.5%), KRT2 (15.7%), KRT14 (7.6%), KRT16 (7.0%), KRT5 (6.1%), KRT9 (5.9%), KRT6B (4.6%), and KRT6A (4.3%). A comparison to the proteomic profile of blank Schirmer strips and controls (empty vials) found a strong correlation (R2 = 0.9753), indicating that these proteins were not from the blank Schirmer strips but are environmental contaminants. On the other hand, several keratins including KRT19, KRT13, KRT4, KRT7, KRT15, KRT8 and KRT18 were present in tear fluid, but either not detected or were negligible in blank strips. Another set of keratins, including KRT5, KRT6A, KRT14, KRT16, and KRT17, were identified as components of tear fluid as well as environmental contaminants.

CONCLUSIONS

This study revealed nine major contaminant keratins in the mass spectrometry analysis. Several other keratins were identified as constituents of tear fluid. Background subtraction is necessary for the accurate analysis of tear fluid using mass spectrometry.

Dry eye post-cataract surgery: a systematic review and meta-analysis

SIGNIFICANCE

Cataract surgery is one of the most performed surgical procedures worldwide. As a potential complication following cataract surgery, dry eye has the potential to impact visual outcomes, lower patient satisfaction, and be detrimental to quality of life.

PURPOSE

To evaluate the effect of cataract surgery on dry eye outcomes postoperatively.

METHODS

We searched Ovid MEDLINE and Embase from 01/01/2010 to 16/08/2021 and included observational studies of participants ≥ 18 years old undergoing any cataract surgical procedure. We compared postoperative dry eye outcomes with baseline including Ocular Surface Disease Index (OSDI), tear break up time (TBUT), Schirmer's I test (ST1), and corneal fluorescein staining (CFS) at short-term (< 1 week) and medium-term (≥ 1 week to 3 months) follow-up.

RESULTS

Our search yielded 11,133 records. After title and abstract, and then full text screening, we included 20 studies with 1,694 eyes. There was some evidence indicating a decrease in the TBUT during the short-term (within 1 week) and medium-term (1 week up to 3 months) periods following cataract surgery. There was a considerable degree of heterogeneity between studies across other outcomes. At medium-term follow-up most studies that reported ST1 and CFS showed deterioration of these outcomes but there was conflicting evidence of the effect of cataract surgery on OSDI. The review is limited by variability in follow-up timeframes which were unable capture potential clinical course like peak occurrence and duration.

CONCLUSION

Dry eye may persist up to three months postoperatively following cataract surgery. Further studies are required to determine if dry eye outcomes return to baseline at longer term follow-up.

Wavelength-dependent DNA damage induced by single wavelengths of UV-C radiation (215 to 255 nm) in a human cornea model

Scientific bodies overseeing UV radiation protection recommend safety limits for exposure to ultraviolet radiation in the workplace based on published peer-reviewed data. To support this goal, a 3D model of the human cornea was used to assess the wavelength dependence of corneal damage induced by UV-C radiation. In the first set of experiments the models were exposed with or without simulated tears; at each wavelength (215-255 nm) cells with DNA dimers and their distribution within the epithelium were measured. Simulated tears reduced the fraction of damaged cells to an extent dependent on the wavelength and tissue layer. Subsequent experiments were performed with models exposed without simulated tears; yields of DNA-damaged cells and their distribution within the corneal epithelium were evaluated at each wavelength, together with other markers of cell and tissue integrity. Unlike relatively longer wavelengths, the range of wavelengths commonly referred to as far-UV-C (215-235 nm) only induced dimers in the uppermost layers of the epithelium and did not result in lasting damage or halt proliferation of the germinative cells. These results provide evidence for the recommended exposure limits for far-UV-C wavelengths, which have been proposed as a practical technology to reduce the risk of transmission of airborne diseases in occupied locations.

Applications and latest research progress of liposomes in the treatment of ocular diseases

The special structure of eyes and the existence of various physiological barriers make ocular drug delivery one of the most difficult problems in the pharmaceutical field. Considering the problems of patient compliance, local administration remains the preferred method of drug administration in the anterior part of eyes. However, local administration suffers from poor bioavailability, need for frequent administration, and systemic toxicity. Administration in the posterior part of the eye is more difficult, and intravitreal injection is often used. But intravitreal injection faces the problems of poor patient compliance and likely side effects after multiple injections. The development of nanocarrier technology provides an effective way to solve these problems. Among them, liposomes, as the most widely used carrier in clinical application, have the characteristics of amphiphilic nanostructure, easy surface modification, extended release time, good biocompatibility, etc. The liposomes are expected to overcome obstacles and effectively deliver drugs to the target site to improve ocular drug bioavailability. This review summarized the various controllable properties of liposomes for ocular delivery as well as the application and research progress of liposomes in various ocular diseases. In addition, we summarized the physiological barriers and routes of administration contained in eyes, as well as the prospects of liposomes in the treatment of ocular diseases.

Is a thermal pulsation system (LipiFlow) effective as a standalone treatment for meibomian gland dysfunction and dry eye? A systematic review and meta-analysis

Background

Dry eye disease is a common condition that causes symptoms such as dryness, irritation, and blurry vision. The pathophysiology of dry eye disease features both aqueous deficiency (loss of aqueous tear production) and increased evaporation (loss of the lipid layer), with the latter mechanism responsible for most of the disease presentation. Ocular surface disease (OSD) is a prevalent condition, often linked to meibomian gland dysfunction (MGD), characterized by tear film instability and symptoms like dryness and irritation. Thermal pulsation therapy, an FDA-approved treatment for MGD, uses heat and pressure to restore gland function, improving tear film stability and ocular health. Studies show its benefits last up to a year, enhancing Ocular Surface Disease Index (OSDI), tear break-up time (TBUT), and Meibomian Glands Yielding Secretion Score (MGYSS) scores. This systematic review evaluates LipiFlow compared to placebo, warm compresses, and other devices, focusing on safety, efficacy, and its impact on recovery and long-term outcomes.

Methods

A comprehensive search was performed across PubMed, MEDLINE, Embase, and Scopus until December 2024. Only randomized controlled trials (RCTs) evaluating LipiFlow were included. The primary outcomes assessed were OSDI and TBUT, with secondary outcomes including meibomian gland expression scores, corneal fluorescein staining (CFS), MGYSS, and lipid layer thickness (LLT). Meta-analyses were conducted using a random-effects model, and heterogeneity was assessed using I² statistics.

Results

Thirteen studies reported OSDI (Std diff -0.076, 95% CI -0.277 to 0.125, p = 0.255, I² = 71.21%). Twelve studies evaluated MGYSS, showing significant improvement (Std diff 0.449, 95% CI 0.173-0.725, p = 0.001, I² = 78.49%). TBUT results from twelve studies were not statistically significant (Std diff 0.211, 95% CI -0.017 to 0.440, p = 0.8350, I² = 0%). CFS showed significant improvement in six studies (Std diff -0.130, 95% CI -0.248 to -0.012, p = 0.031, I² = 0%). LLT changes were insignificant (Std diff -0.071, 95% CI -0.381 to 0.239, p = 0.653, I² = 0%).

Conclusion

LipiFlow effectively improves meibomian gland function, as indicated by TBUT, MGYSS, and CFS, but its impact on LLT and OSDI is not significant. The therapy is most beneficial for patients with severe baseline MGD. Further research is needed to establish long-term benefits and patient-specific outcomes.

Silk-Derived Protein-4 Versus Vehicle Control in Treating Patients With Moderate to Severe Dry Eye Disease: A Randomized Clinical Trial

PURPOSE

In this study the safety and efficacy of silk-derived protein 4 (SDP-4), also known as amlisimod, eye drops against a vehicle control formulation in patients with moderate to severe dry eye disease (DED) was assessed. SDP-4 is a novel, naturally derived, anti-inflammatory wetting agent that enhances coating on the ocular surface.

DESIGN

Exploratory Phase 2, 12- and 8-week, serial cohort, multicenter, double-masked, randomized, vehicle-controlled study.

METHODS

In the first cohort (N = 305), patients were randomized 1:1:1:1 to SDP-4 (0.1%, 1%, 3% wt./wt.) or vehicle control and dosed 2 times per day (BID), while in the second cohort patients were randomized 1:1 with 1% wt./wt. SDP-4, the best performing formulation from the first cohort, or vehicle control BID (N = 151). Diagnosed DED patients were treated in the United States between April 2019 and May 2021. The first cohort of subjects had moderate to severe baseline symptoms, while the second cohort had moderate baseline symptoms to study the impact of baseline symptoms on SDP-4 performance. Key sign and symptom end points were mean change from baseline in TBUT and total SANDE score (0-100 visual analog scale) throughout the study.

RESULTS

SDP-4 (1%) significantly increased TBUT vs the vehicle control (P < .05) at days 28 and 56 in the first cohort, and patient symptomatology from baseline was reduced by 46% based on subject reported SANDE VAS scores at day 84. Patients with more severe baseline DED symptoms experienced a significantly greater amount of relief than when compared to patients with moderate DED (P < .05). All treatment groups were well tolerated with a 2.6% total discontinuation rate.

CONCLUSIONS

To the best of our knowledge, this was the first-in-human use of SDP-4 in a clinical trial. SDP-4 is a first-in-class protein ingredient that offers a safe and multi-modal treatment approach for alleviating severe DED symptoms within a novel formulation.

Corneal Refractive Surgery Considerations in Patients with Anorexia Nervosa

Anorexia nervosa (AN) is a psychiatric eating disorder characterized by body mass index (BMI) ≤ 18.5, fear of gaining weight, and a distorted perception of body weight. With increasing rates of myopia, there is a population of patients who concurrently develop AN and may seek corneal refractive surgery. This study reviews the ophthalmic manifestations of AN and provides preliminary guidelines for patients with AN undergoing corneal refractive surgery. The literature search was conducted through the PubMed, Scopus, and Ovid databases through June 2, 2024, for publications detailing the ocular manifestations of AN. These findings were then considered in the context of potential complications after corneal refractive surgery, and preoperative guidelines for patients with AN were formulated. Twelve articles described a total of 114 patients with AN (227 eyes) with ophthalmic manifestations. Among the studied eyes, 14% had ocular surface abnormalities, 5% had cataracts/visual disturbances, 64% had posterior segment abnormalities, and 20% had orbital/neurological abnormalities. Various ophthalmic findings of AN may increase the risk of delayed corneal wound healing, ocular surface dryness, perioperative bleeding, flap-related complications, and poor visual outcomes after corneal refractive surgery. The BMI of patients suspected with AN must be assessed, and patients should be screened for diagnosis of AN. If mildly and moderately underweight patients with AN have normal ophthalmic and medical workups, they may proceed with a typical preoperative workup for corneal refractive surgery. Ultimately, the decision to recommend elective corneal refractive surgery for these patients rests with the surgeon. This study should be considered a foundation for future research, encouraging collaboration across medical disciplines to develop more comprehensive guidelines for managing this patient population.

Wavelength-Dependent DNA Damage Induced by Single Wavelengths of UVC Light (215 to 255 nm) in a Human Cornea Model

Scientific bodies overseeing UV radiation protection recommend safety limits for exposure to ultraviolet light in the workplace based on published peer-reviewed data. To support this goal, a 3D model of the human cornea was used to assess the wavelength dependence of corneal damage induced by UVC light. In the first set of experiments the models were exposed with or without simulated tears; at each wavelength (215-255 nm) cells with DNA dimers and their distribution within the epithelium were measured. Simulated tears reduced the fraction of damaged cells to an extent dependent on the wavelength and tissue layer. Another set of models were exposed without tears; yields of DNA-damaged cells and their distribution within the corneal epithelium were evaluated at each wavelength, together with other markers of cell and tissue integrity. Unlike relatively longer wavelengths, the range commonly referred to as far-UVC (215-235 nm) only induced dimers in the uppermost layers of the epithelium and did not result in lasting damage or halt proliferation of the germinative cells. These results provide evidence for the recommended exposure limits for far-UVC wavelengths, which have been proposed as a practical technology to reduce the risk of transmission of airborne diseases in occupied locations.

From Preformulative Design to In Vivo Tests: A Complex Path of Requisites and Studies for Nanoparticle Ocular Application. Part 1: Design, Characterization, and Preliminary In Vitro Studies

Ocular pathologies are widely diffused worldwide, and their effective treatment, combined with a high patient compliance, is sometimes challenging to achieve due to the barriers of the eye; in this context, the use of nanoparticles for topical ophthalmic application could represent a successful strategy. Aiming to develop nanoplatforms with potential clinical applications, great attention has to be paid to their features, in relation to the route of administration and to the pharmacopoeial requirements. This review (part 1) thus embraces the preliminary steps of nanoparticle development and characterization. At the beginning, the main barriers of the eye and the different administration routes are resumed, followed by a general description of the advantages of the employment of nanoparticles for ocular topical administration. Subsequently, the preformulative steps are discussed, deepening the choice of raw materials and determining the quantitative composition. Then, a detailed report of the physicochemical and technological characterization of nanoparticles is presented, analyzing the most relevant tests that should be performed on nanoparticles to verify their properties and the requisites (both mandatory and suggested) demanded by regulatory agencies. In conclusion, some preliminary noncellular in vitro evaluation methods are described. Studies from in vitro cellular assays to in vivo tests will be discussed in a separate (part 2) review paper. Hence, this overview aims to offer a comprehensive tool to guide researchers in the choice of the most relevant studies to develop a nanoplatform for ophthalmic drug administration.

From Preformulative Design to in Vivo Tests: A Complex Path of Requisites and Studies for Nanoparticle Ocular Application. Part 2: In Vitro, Ex Vivo, and In Vivo Studies

The incidence of ocular pathologies is constantly increasing, as is the interest of the researchers in developing new strategies to ameliorate the treatment of these conditions. Nowadays, drug delivery systems are considered among the most relevant approaches due to their applicability in the treatment of a great variety of inner and outer eye pathologies through painless topical administrations. The design of such nanocarriers requires a deep study of many aspects related to the administration route but also a consideration of the authorities and pharmacopeial requirements, in order to achieve a clinical outcome. On such bases, the scope of this review is to describe the path of the analyses that could be performed on nanoparticles, along with the assessment of their applicability for ophthalmic treatments. Preformulation studies, physicochemical and technological characterization, and preliminary noncellular in vitro studies have been described in part 1 of this review. Herein, first the in vitro cellular assays are described; subsequently, nonocular organotypic tests and ex vivo studies are reported, as to present the various analyses to which the formulations can be subjected before in vivo studies, described in the last part. In each step, the models that could be used are presented and compared, highlighting the pros and cons. Moreover, their reliability and eventual acceptance by regulatory agencies are discussed. Hence, this review provides an overview of the most relevant assays applicable for nanocarriers intended for ophthalmic administration to guide researchers in the experimental decision process.

Evaluating the Efficacy of the Diluted Schirmer Method for Tear Collection in Dry Eye Syndrome Patients

PURPOSE

This study assesses the diluted Schirmer method's effectiveness in collecting tears from dry eye syndrome patients, aiming to identify the most suitable tear collection technique for them.

METHODS

A prospective study. Tear samples were collected from patients with dry eye syndrome and healthy individuals using two methods: (1) Direct Schirmer Method: Schirmer strips were directly inserted into the eye to collect tears. (2) Diluted Schirmer Method: After instilling physiological saline into the eye and waiting for 30 s to ensure thorough mixing with tears, Schirmer strips were used for collection. Tear samples from both groups were analyzed and compared for total protein and cytokine levels (IL-1β, IL-6, IL-8, TNF-α).

RESULTS

(1) The study included 32 participants: 16 with dry eye syndrome (4 males, 12 females, average age 34.92 ± 10.13 years) and 16 healthy controls (5 males, 11 females, average age 32.25 ± 9.87 years). (2) The diluted Schirmer method produced a significantly larger tear volume compared to the direct method (p < 0.05), with lower Visual Analogue Scale (VAS) scores indicating less discomfort (p < 0.05). (3) The average total protein content of the two groups was 51.70 ± 3.166 ng measured by Direct Schirmer method, and the average total protein content of the Diluted Schirmer method was 50.05 ± 3.263 ng. There was no statistical difference between the two groups. (t = 1.051, p = 0.3098) (4) The concentrations of total tear protein and various cytokines measured by both methods were higher in the dry eye group compared to the normal group, with statistically significant differences (p < 0.05). Both methods reflected consistent changes in tear protein profiles.

CONCLUSION

The diluted Schirmer method can comfortably collect an adequate volume of tear samples in a short time and consistently reflect changes in tear proteins, making it an effective method for tear collection in patients with dry eye syndrome.

Tear fluid reflects the altered protein expressions of Alzheimer's disease patients in proteins involved in protein repair and clearance system or the regulation of cytoskeleton

BACKGROUND

New biomarkers that improve diagnosis of Alzheimer's disease (AD) are warranted. Tear fluid (TF) containing variety of proteins that reflect pathophysiological changes of systemic diseases makes TF proteins potential biomarker candidates for AD.

OBJECTIVE

We investigated the expression levels of TF proteins in persons with mild AD and cognitively healthy controls (CO) to find out if altered proteins may link to the AD pathophysiology.

METHODS

We analyzed the data of the 53 study participants (34 COs, mean age 71 and Mini-Mental State Examination (MMSE) 28.9 ± 1.4 and 19 persons with AD, CDR 0.5-1, mean age 71 and MMSE 23.8 ± 2.8). All went through neurological status examination, cognitive tests, and ophthalmological examination. TF was collected using Schirmer strips. The TF protein content was evaluated via mass spectrometry-based proteomics and label-free quantification.

RESULTS

Eleven proteins having a role either in protein repair and clearance system, or regulation of cytoskeleton, showed altered expression in AD group compared to CO group. Seven of them were significantly (p ≤ 0.05) upregulated (Sti1, Twf1, Myl6, Otub1, Pls1 and Caza1) or, downregulated (HSP90) in AD group.

CONCLUSIONS

Altered expression of all these up- or downregulated proteins may be linked to AD pathophysiology. Thus, our results are encouraging for searching new biomarker candidates for AD. TF is potential biomarker candidate, because TF seems to reflect altered protein levels already in mild AD dementia.

Evaluation of ocular surface inflammation and systemic conditions in patients with systemic lupus erythematosus: a cross-sectional study

OBJECTIVE

The cross-sectional study was designed to evaluate the association of ocular surface inflammation with systemic conditions in patients with systemic lupus erythematosus (SLE).

METHODS

The study enrolled 30 SLE patients and 30 controls. Ocular symptoms were evaluated using the Ocular Surface Disease Index (OSDI) questionnaire. Tear samples from all participants were collected for tear multi-cytokine and chemokine concentration analysis. All participants were assessed for dry eye disease (DED), including Schirmer I test, tear break-up time (TBUT), corneal fluorescein staining (CFS), meibomian gland secretion (MGS), lid-parallel conjunctival folds (LIPCOF), corneal clarity, and symblepharon. Besides, all participants were also examined for conjunctival impression cytology to measure the density of conjunctival goblet cells (CGCs). The peripheral blood indicators from SLE patients were also collected to measure the SLE-associated autoantibody specificities and systemic inflammatory indicators. Pearson and Spearman's analysis were uesd to examine the correlation between tear cytokines, CGCs, DED-related indicators, and systemic conditions.

RESULTS

The two groups were matched for age and gender in this study. 36.67% of eyes (11 in 30) of SLE patients and 13.33% of eyes (4 in 30) of controls were diagnosed with DED. OSDI scores, abnormal TBUT percentages, CFS percentages, and DED grading were all higher in SLE patients than in control group, while density of CGCs was lower. There were no significant differences in Schirmer I test, MGS, LIPCOF, corneal clarity, and symblepharon between SLE patients and controls. The levels of tear chemokine (C-X-C motif) ligand 11 (CXCL11) and cytokine interleukin-7 (IL-7) in patients with SLE were significantly higher than those in control group. Moreover, among SLE patients, the severity of DED and the level of tear chemokine CXCL11 were significantly positively correlated with SLE-associated autoantibody specificities.

CONCLUSION

Dry eye and tear cytokines and chemokines-mediated ocular surface inflammation persist in SLE patients and are associated with systemic conditions. Therefore, it is necessary for patients with SLE to combine systemic and ocular assessments.

Influence of Lifestyle Factors on Ocular Surface Parameters in Relation to Age

PURPOSE

To evaluate how Video Display Terminal (VDT) use, Contact Lens (CL) wear, and eyedrop use affect ocular surface parameters in participants with ocular discomfort and how these factors may vary across different age groups.

METHODS

The current cross-sectional study initially involved a total of 252 participants who completed a self-administered survey to collect information about ocular discomfort and lifestyle factors. This online survey was composed of an Ocular Surface Disease Index (OSDI) questionnaire and three extra questions regarding lifestyle factors (VDT use, CL wear, and eyedrop use). Only 185 symptomatic participants, those with OSDI values > 12, were scheduled to undergo a comprehensive ocular examination that included tear film osmolarity, Fluorescein Break-Up Time (FBUT), Maximum Blink Interval (MBI), and corneal staining.

RESULTS

Differences in ocular parameters and lifestyle factors across age groups (<40 years, 40-60 years, >60 years) were analyzed, along with their correlations and regression. Significant age group differences were found in OSDI, osmolarity, FBUT, and MBI (One-way ANOVA, all p ≤ 0.029). Correlations were observed between CL wear and osmolarity and MBI (Pearson's correlation, both p ≤ 0.049). Multiple regression confirmed age associations with OSDI, osmolarity, FBUT, and MBI (Multiple linear regression, all p ≤ 0.040) and found links between VDT use and osmolarity and MBI (Multiple linear regression, both p ≤ 0.038) and between eyedrop use and OSDI (Multiple linear regression, p = 0.040).

CONCLUSION

Aging is a primary factor affecting ocular homeostasis, with older adults showing lower FBUT and MBI values and higher osmolarity. Prolonged use of VDTs exacerbates this effect, further contributing to ocular discomfort and destabilized tear film. No associations between CL wear and any of the ocular parameters were found. Eyedrop use shows varied effects on ocular comfort across age groups, emphasizing the need for age-specific ocular care. Overall, these findings confirm that aging and extended VDT use play a significant role in ocular surface discomfort.

C. elegans epicuticlins define specific compartments in the apical extracellular matrix and function in wound repair

The apical extracellular matrix (aECM) of external epithelia often contains lipid-rich outer layers that contribute to permeability barrier function. The external aECM of nematodes is known as the cuticle and contains an external lipid-rich layer - the epicuticle. Epicuticlins are a family of tandem repeat cuticle proteins of unknown function. Here, we analyze the localization and function of the three C. elegans epicuticlins (EPIC proteins). EPIC-1 and EPIC-2 localize to the surface of the cuticle near the outer lipid layer, as well as to interfacial cuticles and adult-specific struts. EPIC-3 is expressed in dauer larvae and localizes to interfacial aECM in the buccal cavity. Skin wounding in the adult induces epic-3 expression, and EPIC proteins localize to wound sites. Null mutants lacking EPIC proteins are viable with reduced permeability barrier function and normal epicuticle lipid mobility. Loss of function in EPIC genes modifies the skin blistering phenotypes of Bli mutants and reduces survival after skin wounding. Our results suggest EPIC proteins define specific cortical compartments of the aECM and promote wound repair.

Oxidation enhances the toxicity of polyethylene microplastics to mouse eye: Perspective from in vitro and in vivo

Microplastics (MPs) are ubiquitously dispersed in the environment, and undergoing the process of oxidation that alters their physical and chemical properties. Eyes, which directly interface with the external milieu, inevitably encounter MPs. Nonetheless, the ophthalmic toxicity of MPs towards organisms remains unclear. In this study, primary mouse corneal epithelial cells (MCECs), C57BL/6 mice, and CX3CrlGFP/+ mice were utilized to evaluate the toxicity and differences between oxidized low-density polyethylene MPs (modified-MPs) and low-density polyethylene MPs (virgin-MPs) on eyes. The results manifested that virgin-MPs and modified-MPs could be endocytosed by primary MCECs, resulting in a range of cellular damage. Furthermore, they could diminish tear secretion, increase intraocular pressure, and could be internalized into cornea and retina in mice, instigating a series of detrimental reactions. Importantly, modified-MPs exhibited heightened toxicity towards mouse eyes, seemingly due to oxidation enhances the interaction between virgin-MPs/modified-MPs and tissues/cells, and leading to the release of toxic substances increased. In conclusion, our discoveries demonstrate that oxidation exacerbates the harm of virgin-MPs to eyes, and are of great significance for evaluating the risk of MPs to ocular health.

Advancements in Ocular Therapy: A Review of Emerging Drug Delivery Approaches and Pharmaceutical Technologies

Eye disorders affect a substantial portion of the global population, yet the availability of efficacious ophthalmic drug products remains limited. This can be partly ascribed to a number of factors: (1) inadequate understanding of physiological barriers, treatment strategies, drug and polymer properties, and delivery systems; (2) challenges in effectively delivering drugs to the anterior and posterior segments of the eye due to anatomical and physiological constraints; and (3) manufacturing and regulatory hurdles in ocular drug product development. The present review discusses innovative ocular delivery and treatments, encompassing implants, liposomes, nanoparticles, nanomicelles, microparticles, iontophoresis, in situ gels, contact lenses, microneedles, hydrogels, bispecific antibodies, and gene delivery strategies. Furthermore, this review also introduces advanced manufacturing technologies such as 3D printing and hot-melt extrusion (HME), aimed at improving bioavailability, reducing therapeutic dosages and side effects, facilitating the design of personalized ophthalmic dosage forms, as well as enhancing patient compliance. This comprehensive review lastly offers insights into digital healthcare, market trends, and industry and regulatory perspectives pertaining to ocular product development.

Analysis of the heterogeneity and complexity of murine extraorbital lacrimal gland via single-cell RNA sequencing

PURPOSE

The lacrimal gland is essential for maintaining ocular surface health and avoiding external damage by secreting an aqueous layer of the tear film. However, a healthy lacrimal gland's inventory of cell types and heterogeneity remains understudied.

METHODS

Here, 10X Genome-based single-cell RNA sequencing was used to generate an unbiased classification of cellular diversity in the extraorbital lacrimal gland (ELG) of C57BL/6J mice. From 43,850 high-quality cells, we produced an atlas of cell heterogeneity and defined cell types using classic marker genes. The possible functions of these cells were analyzed through bioinformatics analysis. Additionally, the CellChat was employed for a preliminary analysis of the cell-cell communication network in the ELG.

RESULTS

Over 37 subclasses of cells were identified, including seven types of glandular epithelial cells, three types of fibroblasts, ten types of myeloid-derived immune cells, at least eleven types of lymphoid-derived immune cells, and five types of vascular-associated cell subsets. The cell-cell communication network analysis revealed that fibroblasts and immune cells play a pivotal role in the dense intercellular communication network within the mouse ELG.

CONCLUSIONS

This study provides a comprehensive transcriptome atlas and related database of the mouse ELG.

Detection of SARS-CoV-2 binding receptors and miscellaneous targets as well as mucosal surface area of the human lacrimal drainage system

PURPOSE

Our aim was to evaluate a potential role for the lacrimal drainage system (LDS) as a portal of entry and conduit for SARS-CoV-2 in human infection. We also investigate the mucosal surface area. The relatively long tear contact time in a closed system raises the possibility that this pathway may contribute to the initiation of systemic infection. We looked for expression of ACE2, the main receptor for SARS-CoV-2, as well as cofactors such as TMPRSS2 and other enzymes such as cathepsinB, CD147, elastase1, furin, neuropilin1, neuropilin2, TMPRSS11D and trypsin which also play a role in SARS-CoV-2 infection, in this system.

METHODS

Human tissue samples of the draining tear ducts from body donors were analyzed by RT-PCR, Western blot and immunohistochemistry. It is not known whether the respective body donors were Sars-Cov-2 positive at any time; they were negative when they entered the institute. Besides, the draining LDS of body donors were measured to determine the mucosal surface in the lacrimal system.

RESULTS

The expression of the main receptor studied, ACE2, cofactors such as TMPRSS2 and other enzymes such as cathepsinB, CD147, elastase1, furin, neuropilin1, neuropilin2, TMPRSS11D and trypsin were all detected at the gene and protein level. The average mucosal surface area of the lacrimal sac and nasolacrimal duct was calculated to be 110 mm2.

CONCLUSION

The results show the presence of all analyzed receptors in the efferent LDS. With an average tear passage time of 3 min and a relatively large mucosal surface area, the LDS could therefore be considered as a portal of entry and conduit for SARS-CoV-2. In addition, it represents a surface that should be taken into consideration in the administration of topically applied medication to the ocular surface.

A Review of the Tear Film Biomarkers Used to Diagnose Sjogren's Syndrome

This literature review looks at Sjogren's Syndrome (SS), a chronic autoimmune disorder affecting exocrine glands, particularly the lacrimal and salivary glands. SS manifests as ocular and oral dryness, with severe complications like visual dysfunction and corneal perforation, as well as systemic implications, such as interstitial lung disease and lymphoma. This review explores the use of tear film biomarkers to diagnose SS, emphasizing the significance of their identification in aiding clinical diagnosis and differentiation from other diseases. This study identified and analyzed 15 papers, encompassing 1142 patients and employing various tear sample collection methods. Tear biomarkers were categorized by function and explored in-depth. Categories include (1) antimicrobials, antivirals, and antifungals; (2) components of immune regulation; (3) components that regulate metabolic processes; and (4) inflammatory markers. Noteworthy findings include the potential diagnostic values of tear lysozyme, lactoferrin, dinucleoside polyphosphates, cathepsin, defensin, antibodies, epidermal fatty acid-binding protein, HLA-DR, ADAM10, aquaporin 5, and various miRNAs and mRNAs. Overall, our understanding of SS tear film composition is enhanced, providing valuable insights into the pathogenesis of SS and offering a foundation for future diagnostic and therapeutic advancements in autoimmune conditions affecting the ocular surface.

The involvement of aquaporin 5 in the inflammatory response of primary Sjogren's syndrome dry eye: potential therapeutic targets exploration

Sjogren's syndrome (SS) is a chronic autoimmune disease. Mainly due to the infiltration of lymphoplasmic cells into the exocrine glands, especially the salivary glands and lacrimal glands, resulting in reduced tear and saliva secretion. Reduced tear flow can trigger Sjogren's syndrome dry eye (SSDE). Although the pathophysiology of SSDE xerosis remains incompletely understood, recent advances have identified aquaporin-5 (AQP5) as a critical factor in dysregulation of the exocrine gland and epithelium, influencing the clinical presentation of SSDE through modulation of inflammatory microenvironment and tear secretion processes. This review aims to explore AQP5 regulatory mechanisms in SSDE and analyze its potential as a therapeutic target, providing new directions for SSDE treatment.

Tear levels of Transforming Growth Factor-β1 and Interleukin 1-β, and clinical correlations in new contact lens users

PURPOSE

To assess alterations in the tear Transforming Growth Factor (TGF)-β1 and Interleukin (IL1)-β concentration in new contact lens wearers; and explore correlations with tear film stability, and ocular physiological response.

METHODS

In this clinical setting, 12 neophytes (5 males), with an average age of 24.0 ± 5.0 years were fitted with delefilcon A contact lenses. Physiological responses (bulbar and limbal hyperemia), Pre-corneal (NIBUT), Pre-lens (PL-NIBUT) non-Invasive Break-Up Times, and tear samples were collected in the morning (before lens insertion; 9 - 10 a.m.) and afternoon (before lens removal; 7 - 8p.m.) of the same day. NIBUT and PL-NIBUT were measured using a tearscope. Tear samples were assayed for TGF-β1 and IL1-β concentrations using Enzyme-Linked Immunosorbent Assay kits. An 11-members control group (6 males) aged 25.0 ± 5.0, served to assess biomarker levels in non-contact lens wearers' tears.

RESULTS

Subjects wore lenses for an average of 7 h and 20 min (range: 6 to 9 h). Bulbar and limbal hyperemia increased significantly throughout the day (p < 0.001). PL-NIBUT were lower than NIBUT (4.7 ± 2.0 Vs. 12.2 ± 8.8 s; p < 0.001). The IL1-β levels were higher in neophytes than controls (3.2 ± 4.7 Vs. 0.1 ± 0.1 pg/ml; p = 0.05), correlating significantly with bulbar (r = 0.405, p = 0.008) and limbal hyperemia (r = 0.499, p = 0.027). No substantial changes were reported for TGF-β1.

CONCLUSION

The presence of TGF-β1 in tears does not appear significantly affected by lens wear. The association between physiological parameters and IL1-β levels suggests that lenses may disrupt ocular surface homeostasis by altering cytokine regulatory mechanisms. However, due to its low concentration, IL1-β's role in the subclinical inflammatory response to lens wear is limited.