Correlation Between Signs and Symptoms of Ocular Surface Dysfunction and Tear Osmolarity With Ambient Levels of Air Pollution in a Large Metropolitan Area

The effect of airborne particulate matter 2.5 (PM2.5) on meibomian gland

Exposure to particulate matters in air pollution of 2.5 μm or less (PM2.5) was associated with loss of meibomian glands. The aim of this study was to verify that PM2.5 could directly impact meibomian gland epithelial cells and damage their function. To investigate the impact of PM2.5 on meibomian gland, immortalized human meibomian gland epithelial cells were treated with various concentrations of PM2.5in vitro. Meibomian gland cell microstructure, cell viability, expression of proliferating cell nuclear antigen and IL-1β, and intracellular accumulation of acidic vesicles were measured by transmission electron microscopy, cell counting, Western blot and LysoTracker staining, respectively. To further study the effect of PM2.5in vivo, male C57BL/6J mice were treated with 5 mg/ml PM2.5 or vehicle for 3 months. Corneal fluorescein staining and ocular examinations were done before and after the treatment. Eyelids tissues were processed for morphological studies, immunostaining and Oil Red O staining. Our data suggest that exposure to PM2.5 caused significant meibomian gland dropout, clogged gland orifice and increased corneal fluorescein staining that were consistent with the clinical presentations of meibomian gland dysfunction. Prominent changes in the morphology and ultrastructure of meibomian glands was observed with PM2.5 treatment. PM2.5 promoted ductal keratinization, inhibited cell proliferation, induced cell apoptosis and increased Interleukin-1β production in meibomian gland epithelial cells. This study may explain the association between PM2.5 exposure and meibomian gland dropout observed in clinic. PM2.5 resuspension instillation could be used to induce a meibomian gland dysfunction animal model.

Consequences of exposure to particulate matter on the ocular surface: Mechanistic insights from cellular mechanisms to epidemiological findings

Exposure to air pollutants, especially in the case of particulate matter (PM), poses significant health risks throughout the body. The ocular surface is directly exposed to atmospheric PM making it challenging to avoid. This constant exposure makes the ocular surface a valuable model for investigating the impact of air pollutants on the eyes. This comprehensive review assembles evidence from across the spectrum, from in vitro and in vivo investigations to clinical studies and epidemiological studies, offering a thorough understanding of how PM10 and PM2.5 affect the health of the ocular surface. PM has been primarily found to induce inflammatory responses, allergic reactions, oxidative stress, DNA damage, mitochondrial impairment, and inhibit the proliferation and migration of ocular surface cells. In toto these effects ultimately lead to impaired wound healing and ocular surface damage. In addition, PM can alter tear composition. These events contribute to ocular diseases such as dry eye disease, blepharitis, conjunctivitis, keratitis, limbal stem cell deficiency and pterygium. Importantly, preexisting ocular conditions such as dry eye, allergic conjunctivitis, and infectious keratitis can be worsened by PM exposure. Adaptive responses may partially alleviate the mentioned insults, resulting in morphological and physiological changes that could be different between periods of short-term and long-term exposure. Particle size is not the only determinant of the ocular effect of PM, the composition and solubility of PM also play critical roles. Increasing awareness of how PM affects the ocular surface is crucial in the field of public health, and mechanistic insights of these adverse effects may provide guidelines for preventive and therapeutic strategies in dealing with a polluted environment.

Time-series analysis of the association between air pollution exposure and outpatient visits for dry eye disease: a case study in Zhengzhou, China

Background

Dry eye disease (DED) is a prevalent ocular surface disease that significantly impacts patients' quality of life. The association between air pollution and the risk of dry eye disease remains uncertain.

Methods

Data on outdoor air pollutants, meteorological information, and outpatient visits for DED were collected from July 1, 2014, to December 31, 2019. The relationship between ambient air pollutants and DED outpatient visits was analyzed using a generalized additive model with a Poisson distribution.

Results

Among the 5,204 DED patients included in the study, 63.76% were female and 36.24% were male. The single-pollutant model revealed a significant association between a 10 μg/m3 increase in concentrations of fine-particulate matter with a median aerometric diameter of less than 10 μm (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), and carbon monoxide (CO) and outpatient visits for DED. Fine-particulate matter with a median aerometric diameter of less than 2.5 μm (PM2.5) showed a significant association with DED outpatient visits in males and the 19-59 years age group. The strongest associations between air pollutants and outpatient visits were observed in male patients and during the cold season.

Conclusion

The noteworthy correlation between air pollutants and DED outpatient visits can offer evidence for policy makers and underscore the significance of reinforcing environmental protection.

The Efficacy and Safety of Chinese Eye Exercise of Acupoints in Dry Eye Patients: A Randomized Controlled Trial

INTRODUCTION

Dry eye disorder (DED) is a growing global issue linked to excessive digital screen time. Chinese eye exercise of acupoint (CEA), a set of self-massages on shared Chinese acupuncture (CA), has been used to reduce visual-related ocular symptoms and possibly as an alternative treatment for DED. This study aimed to assess the efficacy and safety of CEA.

METHODS

A single-blind randomized controlled trial was conducted at Thammasat University Hospital in Thailand, recruiting 56 participants aged 20-60 years, equally divided into two groups: the treatment group with CEA and the control group with standard lid hygiene treatment (STD). The intervention program lasted 12 weeks.

MAIN OUTCOME MEASURES

Ocular Surface Disease Index (OSDI), tear break-up time (TBUT), Schirmer-I test (SIT), corneal surface staining (CSS), and self-recorded forms for safety and adverse effects were measured at baseline, week 4, and week 12. An independent sample t test, paired t test, and repeated measures (ANOVA) were used to compare results between both groups, study visits, and primary and secondary outcome measurements, respectively. The p values <0.05 were considered statistically significant.

RESULTS

The characteristics were not statistically different between both groups at the baseline. The mean OSDI scores were significantly reduced in both groups at week 4 and week 12 compared to baseline (p value <0.05). Additionally, both CEA and STD showed significant improvement in TBUT and SIT (p value <0.05). CSS was significantly improved only in the CEA groups (p value <0.05). No significant differences were observed between the study groups, except for SIT at week 12 (p value <0.05). For the safety, there were no adverse side effects in either group.

CONCLUSION

CEA seemed to be as effective as STD in improving the OSDI, TBUT, and SIT of DED without causing any side effects.

Einleitung

Das Trockene Auge (Dry eye disorder, DED) ist weltweit ein zunehmendes Problem, das mit übermässiger Bildschirmarbeit zusammenhängt. Die chinesische Augenübung der Akupunkturpunkte (Chinese eye exercise of acupoint, CEA), eine Reihe von Selbstmassagen an gemeinsamen CA-Akupunkturpunkten, wird zur Linderung visusbezogener Augensymptome und als mögliche alternative Behandlung für DED eingesetzt. Mit dieser Studie sollte die Wirksamkeit und Sicherheit von CEA bewertet werden.

Methoden

Am Thammasat-Universitätsklinikum in Thailand wurde eine einfach verblindete, randomisierte, kontrollierte Studie mit 56 Teilnehmern im Alter von 20 bis 60 Jahren durchgeführt, die zu gleichen Teilen zwei Gruppen zugewiesen wurden: die Behandlungsgruppe mit CEA und die Kontrollgruppe, die die Standard-Lidhygienebehandlung erhielt (STD). Das Interventionsprogramm dauerte 12 Wochen. Die Haupt-Zielkriterien, der Ocular Surface Disease Index (OSDI), die Tränenfilmaufreisszeit (tear break-up time, TBUT), der Schirmer-I-Test (SIT), das Corneal Surface Staining (CSS) und Selbstauskunftsformulare zur Sicherheit und zu unerwünschten Wirkungen wurden zu Beginn der Behandlung, in Woche 4 und in Woche 12 ermittelt. Für den Vergleich der Ergebnisse zwischen den beiden Gruppen, den Studienvisiten bzw. den primären und sekundären Zielkriterien wurden ein t Test für unabhängige Stichproben, ein t Test für paarige Stichproben und eine ANOVA mit Messwiederholungen verwendet. p-Werte <0,05 galten als statistisch signifikant.

Ergebnisse

Hinsichtlich der Merkmale bestand zwischen den beiden Gruppen kein statistischer Unterschied bei Studienbeginn. In beiden Gruppen fielen die mittleren OSDI-Scores in Woche 4 und Woche 12 im Vergleich zum Ausgangswert signifikant geringer aus (p-Wert <0,05). Darüber hinaus zeigten sowohl die CEA- als auch die STD-Gruppe eine signifikante Verbesserung der TBUT- und SIT-Werte (p-Wert <0,05). Das CSS verbesserte sich nur in der CEA-Gruppe signifikant (p-Wert <0,05). Zwischen den Studiengruppen waren keine signifikanten Unterschiede zu beobachten, ausser beim SIT in Woche 12 (p-Wert <0,05). Was die Sicherheit betrifft, so traten in beiden Gruppen keine unerwünschten Nebenwirkungen auf.

Schlussfolgerung

Die CEA schien die OSDI-, TBUT- und SIT-Werte bei DED ebenso wirksam zu verbessern wie die Standardbehandlung, ohne Nebenwirkungen zu verursachen.

Air Pollution and Chronic Eye Disease in Adults: A Scoping Review

PURPOSE

We conducted a scoping review of studies examining ambient air pollution as a risk factor for chronic eye disease influencing the lens, retina, and intraocular pressure in adults.

METHODS

Terms related to air pollution and eye disease outcomes were used to search for publications on Embase, Web of Science Core Collection, Global Health, PubMed, and the Cochrane Central Register of Controlled Trials from January 1, 2010, through April 11, 2022.

RESULTS

We identified 27 articles, focusing on the following non-mutually exclusive outcomes: cataract (n = 9), presbyopia (n = 1), retinal vein occlusion or central retinal arteriolar and venular equivalents (n = 5), intraocular pressure (IOP) (n = 3), glaucoma (n = 5), age-related macular degeneration (AMD) (n = 5), diabetic retinopathy (n = 2), and measures of retinal morphology (n = 3). Study designs included cross-sectional (n = 16), case-control (n = 4), and longitudinal (n = 7). Air pollutants were measured in 50% and 95% of the studies on lens and retina or IOP, respectively, and these exposures were assigned to geographic locations. Most research was conducted in global regions with high exposure to air pollution. Consistent associations suggested a possibly increased risk of cataract and retina-associated chronic eye disease with increasing exposure to particulate matter (PM2.5-PM10), NO2, NOx, and SO2. Associations with O3 were less consistent.

CONCLUSIONS

Accumulating research suggests air pollution may be a modifiable risk factor for chronic eye diseases of the lens and retina. The number of studies on each specific lens- or retina-related outcome is limited. Guidelines regarding the role of air pollution in chronic eye disease do not exist.

Particulate Matter Induced Adverse Effects on Eye Development in Zebrafish (Danio rerio) Embryos

Particulate matter (PM) can cause human diseases, particularly respiratory diseases. Since eyes are directly exposed to the air, they might be directly adversely affected by PM. Therefore, we determined the toxicity caused to eye development by PM using zebrafish (Danio rerio) embryos. The PM-induced embryo toxicity was dependent on dose and time and caused significant morphological defects, reducing the total body length and the total eye area. Reactive oxygen species (ROS) overproduction was confirmed in the PM treatment group, and antioxidant genes (cat and sod2), photoreceptor cell development, pigmentation genes (atoh8, vsx1, and rho), eye-embryogenesis genes (pax6a and pax6b), and eye-lens-development genes (cryaa) were downregulated, while eye-development genes (crybb1) were upregulated. In conclusion, PM had a direct adverse effect on the eyes, and zebrafish embryos can be used as a model to evaluate PM-induced eye toxicity in vivo.

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 Report: Impact of environmental conditions on the ocular surface

Environmental risk factors that have an impact on the ocular surface were reviewed and associations with age and sex, race/ethnicity, geographical area, seasonality, prevalence and possible interactions between risk factors are reviewed. Environmental factors can be (a) climate-related: temperature, humidity, wind speed, altitude, dew point, ultraviolet light, and allergen or (b) outdoor and indoor pollution: gases, particulate matter, and other sources of airborne pollutants. Temperature affects ocular surface homeostasis directly and indirectly, precipitating ocular surface diseases and/or symptoms, including trachoma. Humidity is negatively associated with dry eye disease. There is little data on wind speed and dewpoint. High altitude and ultraviolet light exposure are associated with pterygium, ocular surface degenerations and neoplastic disease. Pollution is associated with dry eye disease and conjunctivitis. Primary Sjögren syndrome is associated with exposure to chemical solvents. Living within a potential zone of active volcanic eruption is associated with eye irritation. Indoor pollution, "sick" building or house can also be associated with eye irritation. Most ocular surface conditions are multifactorial, and several environmental factors may contribute to specific diseases. A systematic review was conducted to answer the following research question: "What are the associations between outdoor environment pollution and signs or symptoms of dry eye disease in humans?" Dry eye disease is associated with air pollution (from NO2) and soil pollution (from chromium), but not from air pollution from CO or PM10. Future research should adequately account for confounders, follow up over time, and report results separately for ocular surface findings, including signs and symptoms.

Correlation Between Air Quality Index and Tear Film Lipid Layer Thickness: Comparison Between Patients with Sjogren's Syndrome and with Meibomian Gland Dysfunction

Purpose: To evaluate the effect of air pollution on the tear film stability by analyzing the correlation between Air Quality Index (AQI) and Lipid Layer thickness (LLT) in Xuzhou.Methods: As a prospective descriptive observational study, 284 patients with meibomian gland dysfunction (MGD), 157 patients with Sjögren's syndrome (SS), and 264 healthy volunteers were included. The tear film lipid layer thickness of the three groups of subjects was measured weekly and compared with the air quality index to analyze the correlation between the two indicators. Logistic regression analysis and linear regression analysis were used to analyze the effect of AQI on the thickness of the tear film lipid layer. The change of LLT with air pollution at different AQI levels was also analyzed.Results: There are obvious seasonal differences in the changes of air pollution index in Xuzhou. Significant differences could be observed in the thickness of the lipid layer of the tear film among the three groups. LLT in the MGD group and SS group decreased with the aggravation of air pollution, while remained unchanged in the control group. There was strong evidence of correlation between LLT of the MGD group (F = 353.494, p < 0.01, adjusted R2 = 0.695) and the SS group (F = 502.404, p < 0.01, adjusted R2 = 0.764) with AQI, while there was minor correlation between LLT with AQI in control group (F = 8.525, p < 0.01, adjusted R2 = 0.046).Conclusions: Air pollution can cause a decrease in the thickness of the tear film lipid layer, thereby affecting tear film stability, leading to the occurrence of dry eye.

Size-specific particulate matter and outpatient visits for allergic conjunctivitis in children: a time-stratified case-crossover study in Guangzhou, China

This time-stratified case-crossover study aims to quantify the risk of allergic conjunctivitis (AC) associated with short-term exposure to PMs (i.e., PM₁, PM_2.5, PM_c, and PM₁₀) among children in Guangzhou, China. We collected data on children's daily AC outpatient visits from the Guangzhou Women and Children Medical Center during February 20, 2016 to December 31, 2018, and also extracted air pollution and meteorological data in the same time frame. We used conditional logistic regression model to estimate the associations between PMs and AC outpatient visits, and conducted subgroup analyses stratified by sex, age, and season. During the study period, we recorded 39,330 children's outpatient visits for AC, including 27,638 boys and 11,692 girls. The associations between PMs and AC were general linear with no clear threshold, which were largest at the current days but remained positive for lag 1 to 3 days. For every 10 μg/m³ increase in daily PM₁, PM_2.5, PM_c, and PM₁₀ concentrations, the estimated risks of AC outpatient visits at the current days increased by 2.5% (OR = 1.025, 95% CI: 1.011-1.039), 1.8% (OR = 1.018, 95% CI: 1.009-1.027), 2.1% (OR = 1.021, 95% CI: 1.004-1.039), and 1.3% (OR = 1.013, 95% CI: 1.007-1.020), respectively. In addition, our stratified analyses revealed that girls and children aged 1 to 6 years were more sensitive to PM exposure, and the PM-associated risks for AC were more apparent in autumn and winter. Our study suggests that short-term exposure to PMs may induce AC in children.

Associations between conjunctivitis and ambient PM2.5 and physical activity: A nationwide prospective cohort study

BACKGROUND

Currently, there is no evidence of fine particulate matter pollution (PM_2.5) altering the relationship between physical activity (PA) and the risk of conjunctivitis.

METHODS

Based on the UK Biobank study, we included 308,507 participants aged 40-69 years at baseline (2006 to 2010) and prospectively followed up for conjunctivitis diagnosis till 2020. Annual concentrations of PM_2.5 in 2010 were estimated for each participant using Land Use Regression models. PA levels during work and leisure time were reported via the International Physical Activity Questionnaire at baseline. We used Cox proportional hazards models to examine the associations of PM_2.5 and PA with incident conjunctivitis, as well as their interaction at both multiplicative and additive scales.

RESULTS

During the 11.6 years of follow up, we identified 4002 incident conjunctivitis cases. High-PA (≥3000 metabolic equivalent of task [MET]-mins/week) was associated with lower risk of conjunctivitis (hazard ratio [HR]: 0.79, 95% confidence interval [CI]: 0.73-0.86) compared to low-PA (0 to <600 MET-mins/week), while every 1 μg/m³ increment in PM_2.5 was associated with a 16% higher risk of conjunctivitis (HR = 1.16, 95% CI: 1.09-1.23). We did not observe statistically significant interactions between PM_2.5 and PA on their associations with conjunctivitis.

CONCLUSION

Habitual PA and PM_2.5 exposure were oppositely related to incident conjunctivitis. The benefits of PA remain in people irrespective of exposure to air pollution.

Seasonal variations in presenting symptoms and signs of dry eye disease in Norway

The study investigated the seasonal variations of presenting symptoms and signs of dry eye disease (DED) in Norway. 652 consecutive DED patients examined between August 2012 and May 2015 in Oslo, Norway, were included. Presenting symptoms and signs were related to the season according to when each patient was examined. Weather report data from the examination day were compared with the presenting symptoms and signs. Oslo's mean seasonal temperatures during spring, summer, fall, and winter were 6.4 °C, 15.6 °C, 9.3 °C, and - 2.1 °C, respectively. Dry eye severity level and self-reported symptoms measured by the Ocular surface disease index questionnaire did not differ between seasons. Schirmer I was lower during summer than in other seasons (P < 0.01). The percentage of patients with a pathological tear meniscus height (< 0.2 mm) was higher during fall (P < 0.01) and lower during winter (P < 0.05) compared to the other seasons. Signs and symptoms of DED generally did not correlate with weather report data, although intraocular pressure was weakly associated with mean daily air temperature (r = - 0.22; P < 0.001). Neither dry eye severity level nor dry eye symptoms differ between seasons in Oslo, Norway. However, some parameters for assessing DED show seasonal variations (Schirmer I and tear meniscus height), which are essential to consider when examining patients with DED.

The impact of the first United Kingdom COVID-19 lockdown on environmental air pollution, digital display device use and ocular surface disease symptomatology amongst shielding patients

Worldwide lockdown reduced air pollution during the first phase of the COVID-19 pandemic. The relationship between exposure to ambient air pollution, digital display device use and dry eye symptoms amongst patients with severe ocular surface disease (OSD) were considered. Symptoms and air pollutant concentrations for three different time periods (pre, during and post COVID-19 lockdown) were analysed in 35 OSD patients who achieved an immunosuppression risk-stratification score > 3 fulfilling the UK Government criteria for 12-week shielding. OSDI symptoms questionnaire, residential postcode air pollution data obtained from the Defra Automated Urban and Rural monitoring network for concentrations of nitrogen dioxide (NO₂), nitrogen oxides (NOx), particulate matter (PM) with diameters below 10 µm and 2.5 µm, and English Indices of Deprivation were analysed. Significant reductions in NO₂ and NOx concentrations were observed between pre- and during-lockdown periods, followed by a reversal in the post-lockdown period. Changes were linked to the Living Environment outdoor decile. A 12% increase (p = 0.381) in symptomatology during-lockdown was observed that reversed post-lockdown by 19% (p = 0.144). OSDI scores were significantly correlated with hours spent on digital devices (r² = 0.243) but not with air pollutant concentrations. Lockdown measures reduced ambient air pollutants whilst OSD symptomatology persisted. Environmental factors such as increased time indoors and use of bluescreen digital devices may have partly played a role.

Concentration-dependent increase in symptoms due to diesel exhaust in a controlled human exposure study

Background

Traffic-related air pollution (TRAP) exposure causes adverse effects on wellbeing and quality of life, which can be studied non-invasively using self-reported symptoms. However, little is known about the effects of different TRAP concentrations on symptoms following controlled exposures, where acute responses can be studied with limited confounding. We investigated the concentration–response relationship between diesel exhaust (DE) exposure, as a model TRAP, and self-reported symptoms.

Methods

We recruited 17 healthy non-smokers into a double-blind crossover study where they were exposed to filtered air (FA) and DE standardized to 20, 50, 150 µg/m3 PM2.5 for 4 h, with a ≥ 4-week washout between exposures. Immediately before, and at 4 h and 24 h from the beginning of the exposure, we administered visual analog scale (VAS) questionnaires and grouped responses into chest, constitutional, eye, neurological, and nasal categories. Additionally, we assessed how the symptom response was related to exposure perception and airway function.

Results

An increase in DE concentration raised total (β ± standard error = 0.05 ± 0.03, P = 0.04), constitutional (0.01 ± 0.01, P = 0.03) and eye (0.02 ± 0.01, P = 0.05) symptoms at 4 h, modified by perception of temperature, noise, and anxiety. These symptoms were also correlated with airway inflammation. Compared to FA, symptoms were significantly increased at 150 µg/m3 for the total (8.45 ± 3.92, P = 0.04) and eye (3.18 ± 1.55, P = 0.05) categories, with trends towards higher values in the constitutional (1.49 ± 0.86, P = 0.09) and nasal (1.71 ± 0.96, P = 0.08) categories.

Conclusion

DE exposure induced a concentration-dependent increase in symptoms, primarily in the eyes and body, that was modified by environmental perception. These observations emphasize the inflammatory and sensory effects of TRAP, with a potential threshold below 150 µg/m3 PM2.5. We demonstrate VAS questionnaires as a useful tool for health monitoring and provide insight into the TRAP concentration–response at exposure levels relevant to public health policy.

Evidence of air pollution-related ocular signs and altered inflammatory cytokine profile of the ocular surface in Beijing

We evaluated how different degrees of air pollution affect the ocular surface of a cohort of human subjects in Beijing by correlating in-patient test outcomes with tear cytokines. A cross-sectional study involving 221 volunteers was carried out in different districts of Beijing. Air pollution indices were recorded for 7 d (including the visit day). The indices recorded were the air quality index (AQI), which is a dimensionless measure that quantitatively describes the state of air quality, concentrations of particulate matter smaller than 2.5 μm (PM2.5) and 10 μm (PM10), sulfur dioxide (SO₂), ozone (O₃), and nitrogen dioxide (NO₂). The Ocular Symptom Disease Index (OSDI) questionnaire provided. Subsequently, subjects underwent slit-lamp examination, which included meibomian gland examination, conjunctival congestion score, conjunctivochalasis grade, tear meniscus height (TMH), tear breakup time (TBUT), corneal fluorescein staining (CFS), Schirmer I test, and conjunctival impression cytology. The concentrations of vascular endothelial growth factor (VEGF), interleukins (IL)-1β, IL-6 and IL-8 in tears were measured by microsphere-based immunoassay analysis. According to the value of the AQI, participants are divided into a slightly polluted (SP) group (n = 103) which the AQI value is less than or equal to 100 and a heavily polluted (HP) group (n = 118) whose AQI value is more than 100. Air pollution is related to ocular discomfort based on tear cytokine concentrations. PM2.5, PM10 and NO₂ were positively correlated with OSDI, MG expressibility, meibum score, meiboscore, conjunctival congestion score, Schirmer I test value, TMH, goblet-cell density, concentrations of IL-6, and VEGF were negatively correlated with TBUT. PM2.5 and PM10 appear to be the major risk factors to the ocular surface, with NO₂ being another important risk factor based on this study. The symptoms and signs of eye discomfort in the SP group were significantly less severe than those in the HP group, and tear cytokine concentrations (IL-6 and VEGF) were lower. Air pollution degrees were significantly correlated with tear cytokine concentrations, indicating an alteration of cytokine balance at the ocular surface under different degrees of air pollution.

Smoke and the eyes: A review of the harmful effects of wildfire smoke and air pollution on the ocular surface

Wildfires are occurring worldwide with greater frequency and intensity. Wildfires, as well as other sources of air pollution including environmental tobacco smoke, household biomass combustion, agricultural burning, and vehicular emissions, release large amounts of toxic substances into the atmosphere. The ocular surface is constantly exposed to the ambient air and is hence vulnerable to damage from air pollutants. This review describes the detrimental effects of wildfire smoke and air pollution on the ocular surface and resultant signs and symptoms. The latest relevant evidence is synthesised and critically evaluated. A mechanism for the pathophysiology of ocular surface damage will be proposed considering the existing literature on respiratory effects of air pollution. Current strategies to reduce human exposure to air pollutants are discussed and specific possible approaches to protect the ocular surface and manage air pollution induced ocular surface damage are suggested. Further avenues of research are suggested to understand how acute and chronic air pollution exposure affects the ocular surface including the short and long-term implications.

Particulate matter 2.5 promotes inflammation and cellular dysfunction via reactive oxygen species/p38 MAPK pathway in primary rat corneal epithelial cells

PURPOSE

Numerous studies have linked particulate matter 2.5 (PM_2.5) to ocular surface diseases, but few studies have been conducted on the biological effect of PM_2.5 on the cornea. The objective of the present study was to evaluate the harmful effect of PM2.5 on primary rat corneal epithelial cells (RCECs) in vitro and identify the toxic mechanism involved.

MATERIALS AND METHODS

Primary cultured RCECs were characterized by pan-cytokeratin (CK) staining. In PM2.5-exposed RCECs, cell viability, microarray gene expression, inflammatory cytokine levels, mitochondrial damage, DNA double-strand break and signaling pathway were investigated.

RESULTS

Exposure to PM_2.5 induced cytotoxicity and morphological changes in RCECs. In addition, PM_2.5 markedly up-regulated pro-inflammatory mediators but down-regulated the wound healing-related transforming growth factor-β. Furthermore, PM_2.5 promoted mitochondrial reactive oxygen species (ROS) production and mediated cellular damage to mitochondria and DNA, whereas these cellular alterations induced by PM_2.5 were markedly suppressed by a potential ROS scavenger. Noteworthy, removal of ROS selectively down-regulated the phosphorylation of p38 mitogen-activated protein kinase (MAPK) and the activation of the nuclear factor-κB (NF-κB) p65 in PM_2.5-stimulated cells. Additionally, SB203580, a p38 MAPK inhibitor, markedly suppressed these PM_2.5-mediated cellular dysfunctions.

CONCLUSIONS

Taken together, our findings show that PM_2.5 can promote the ROS/p38 MAPK/NF-κB signaling pathway and lead to mitochondrial damage and DNA double-strand break, which is ultimately caused inflammation and cytotoxicity in RCECs. These findings indicate that the ROS/p38 MAPK/NF-κB signaling pathway is one mechanism involved in PM_2.5-induced ocular surface disorders.

SIRT1 Protects Against Particulate Matter-Induced Oxidative Stress in Human Corneal and Conjunctival Epithelial Cells

Purpose

Sirtuin1 (SIRT1) as a hot therapeutic target for oxidative stress–associated diseases that has been extensively studied. This study aimed to determine the changes in SIRT1 expression in particulate matter (PM)–induced corneal and conjunctival epithelial cell damage and explore potential drugs to reduce PM-associated ocular surface injury.

Methods

Immortalized human corneal epithelial cells (HCECs) and human conjunctival epithelial cells (HCjECs) were exposed to an ambient PM sample. Cytotoxicity was evaluated by water-soluble tetrazolium salt–8 assay. SIRT1 expression was measured by Western blot analysis. Reactive oxygen species (ROS) production, cell apoptosis, mitochondrial function, and cell senescence were assessed by using 2ʹ,7ʹ-dichlorofluorescein diacetate assay, annexin V apoptosis assay, tetramethylrhodamine ethyl ester assay, and senescence β-galactosidase staining, respectively.

Results

PM-induced cytotoxicity of HCECs and HCjECs occurred in a dose-dependent manner. Increased ROS production, as well as decreased SIRT1 expression, were observed in HCECs and HCjECs after 200 µg/mL PM exposure. In addition, PM induced oxidative stress-mediated cellular damage, including cell apoptosis, mitochondrial damage, and cell senescence. Interestingly, SRT1720, a SIRT1 activator, increased SIRT1 expression and decreased ROS production and attenuated PM-induced cell damage in HCECs and HCjECs.

Conclusions

This study determined that SIRT1 was involved in PM-induced oxidative stress in HCECs and HCjECs and found that ROS overproduction may a key factor in PM-induced SIRT1 downregulation. The SIRT1 activator, SRT1720, can effectively upregulate SIRT1 expression and inhibit ROS production, thereby reversing PM-induced cell damage. This study provides a new potential target for clinical treatment of PM-associated ocular surface diseases.

Impact of Air Pollution on the Ocular Surface and Tear Cytokine Levels: A Multicenter Prospective Cohort Study

Purpose

To assess air pollution-induced changes on ocular surface and tear cytokine levels.

Methods

As a prospective multicenter cohort study, 387 dry eye disease (DED) participants were recruited from five provinces in China and underwent measurements of ocular surface disease index (OSDI), Schirmer’s I test (ST), tear meniscus height (TMH), tear film break-up time (TBUT), corneal fluorescein staining (CFS), meibomian gland (MG) function, and tear cytokines. The associations between ocular surface parameters and exposure to particulate matter (PM), ozone (O₃), nitrogen dioxide (NO₂), and sulfur dioxide (SO₂) for 1 day, 1 week, and 1 month before the examination were analyzed in single- and multi-pollutant models adjusted for confounding factors.

Results

In the multi-pollutant model, the OSDI score was positively correlated with PM with diameter ≤2.5 μm (PM_2.5), O₃, and SO₂ exposure [PM_2.5: β (1 week/month) = 0.229 (95% confidence interval (CI): 0.035–0.424)/0.211 (95% CI: 0.160–0.583); O₃: β (1 day/week/month) = 0.403 (95% CI: 0.229–0.523)/0.471 (95% CI: 0.252–0.693)/0.468 (95% CI: 0.215–0.732); SO₂: β (1 day/week) = 0.437 (95% CI: 0.193–0.680)/0.470 (95% CI: 0.040–0.901)]. Tear secretion was negatively correlated with O₃ and NO₂ exposures but positively correlated with PM_2.5 levels. Air pollutants were negatively correlated with TBUT and positively related with CFS score. Besides SO₂, all other pollutants were associated with aggravated MG dysfunction (MG expression, secretion, and loss) and tear cytokines increasement, such as PM_2.5 and interleukin-8 (IL-8) [β (1 day) = 0.016 (95% CI: 0.003–0.029)], PM with diameter ≤10 μm (PM₁₀) and IL-6 [β (1 day) = 0.019 (95% CI: 0.006–0.033)], NO₂ and IL-6 [β (1 month) = 0.045 (95% CI: 0.018–0.072)], among others. The effects of air pollutants on DED symptoms/signs, MG functions and tear cytokines peaked within 1 week, 1 month, and 1 day, respectively.

Conclusion

Increased PM_2.5, O₃, and SO₂ exposures caused ocular discomfort and damage with tear film instability. PM₁₀ exposure led to tear film instability and ocular injury. PM, O₃, and NO₂ exposures aggravated MG dysfunction and upregulated tear cytokine levels. Therefore, each air pollutant may influence DED via different mechanisms within different time windows.

The effects of short-term and long-term air pollution exposure on meibomian gland dysfunction

We aim to assess the effects of different air pollutants on meibomian gland dysfunction (MGD). As a prospective multicenter study, 864 patients were recruited from four different regions (i.e., coal, oil, steel, and living). The oil region had a significantly lower temperature and higher O₃ and SO₂ concentrations than other regions. Notably, participants in oil region presented with more frequent and serious MGD signs and higher cytokine levels (median interleukin 6 [IL-6] in oil: 2.66, steel: 0.96, coal: 0.38, living: 0.56; IL-8 in oil: 117.52, steel: 46.94, coal: 26.89, living: 33; vascular endothelial growth factor [VEGF] in oil: 25.09, steel: 14.02, coal: 14.02, living: 28.47). The short-term fluctuations of cytokine levels were associated with the changes in gas levels (PM_2.5 and IL-8: β = 0.016 [0.004–0.029]; O₃ and IL-6: β = 0.576 [0.386–0.702]; O₃ and IL-8: β = 0.479 [0.369–0.890]; SO₂ and VEGF: β = 0.021 [0.001–0.047]). After long-term exposure, lid margin neovascularization (r = 0.402), meibomian gland (MG) expression (r = 0.377), MG secretion (r = 0.303), MG loss (r = 0.404), and tear meniscus height (r = − 0.345) were moderately correlated with air quality index (AQI). Individuals in oil region had more serious MGD signs and higher cytokine levels. MGD is susceptible to long-term exposure to high AQI.

Diurnal variations of tear film osmolarity on the ocular surface

The measurement of tear film osmolarity has been suggested as a gold standard in the diagnosis of dry eye. Many tear film physiological variables oscillate during the day. This review summarises current clinical knowledge regarding diurnal osmolarity variation in the tear film. A critical analysis is presented in respect of of sample size and characteristics, differences in the diurnal osmolarity variation on healthy versus altered tear film conditions or environment, and time of day and number of measurements undertaken. A comparison of 21 studies was made for studies in which one of the main objectives was to analyse the variance of tear film osmolarity at different time-points in a day on human cohorts. Tear film osmolarity appeard to be somewhat influenced by the time of day in healthy subjects and patients with ocular surface disease, or altered by environmental conditions. Both healthy and non-physiological tear film cohorts showed variations in results depending on the study: no variations during the day or statistically different values at some point in the day. These differences could be in the middle of the day or between the beginning and the end of the day, with higher values in the morning than in the afternoon, or even the opposite situation. The possibility of diurnal variations in tear film osmolarity should be considered by the clinician since the time of day when the tear film measurements are made can be critical in making the right diagnosis. Future studies in the diurnal variation field may have to use a well-established range of measurement time-points and a larger group of healthy subjects and and subjects who have a tear film altered by pathological or environmental conditions.

Association between air pollution and emergency room visits for eye diseases and effect modification by temperature in Beijing, China

The growing burden of eye disease worldwide has aroused increasing concern upon its environmental etiology. This study aims to evaluate the associations of air pollutants with emergency room visits for eye diseases and the effect modification by temperature. Based on 24,389 cases from a general hospital during 2014-2019 in Beijing, China, this study used generalized additive models to examine the associations of air pollutants and emergency room visits for total eye diseases (ICD10: H00-H59) and conjunctivitis (ICD10: H10). Short-term exposures to PM2.5, PM10, CO, and NO2 were associated with increased visits for total eye diseases and conjunctivitis, and stronger effect estimates were observed in high (>75th) temperature group for PM2.5, PM10, CO, and NO2 and low (<75th) temperature group for CO and NO2. For instance, a 10 μg/m3 increase in PM2.5 at lag0-1 were associated with a 0.73% (95% CI: 0.23%, 1.24%) increase in total eye disease visits and a 1.34% (95% CI: 0.55%, 2.13%) increase in conjunctivitis visits, respectively. Meanwhile, a 10 μg/m3 increase in PM2.5 was associated with a 1.57% (95% CI: 0.49%, 2.64%) change in high temperature group and a 0.48% (95% CI: -0.24%, 1.19%) change in medium temperature group (P for interaction = 0.04) in total eye disease visits. Our study emphasizes the importance of controlling the potential hazards of air pollutants on eyes, especially on days with relatively higher or colder temperature.

Low ambient temperature correlates with the severity of dry eye symptoms

PURPOSE:

The symptoms of dry eye disease (DED) are influenced by environmental factors, but the effect of ambient temperature is less certain. Our purpose was to investigate the relationship between the severity of DED symptoms and the ambient temperature.

MATERIALS AND METHODS:

This retrospective study reviewed the symptom scores, including ocular surface disease index (OSDI) and standardized patient evaluation of eye dryness (SPEED), as well as tear film parameters of first-time DED patients between June 2018 and June 2019. The contribution of tear film parameters and environmental factors, including ambient temperature, humidity, wind speed, and the concentration of air pollutants, to the severity of dry eye symptoms was evaluated by univariate and multivariate linear regression analyses.

RESULTS:

There were 351 patients included aged 52.8 ± 13.6 years, and 257 (73.2%) were female. The average tear film break-up time, Schirmer test value, and lipid layer thickness were 2.6 ± 0.7 s, 5.5 ± 4.3 mm, and 64.1 ± 6.0 μm, respectively. The average OSDI and SPEED were 41.8 ± 19.8 and 12.1 ± 5.1, respectively. In winter, the patients reported higher OSDI and SPEED. Both scores were significantly correlated with low ambient temperature. Regression analysis showed that low ambient temperature and Schirmer test value contributed to higher OSDI, while low ambient temperature and younger age contributed to higher SPEED.

CONCLUSION:

Low ambient temperature plays a significant role in DED symptom severity.

Research advances in pathogenic mechanisms underlying air pollution-induced ocular surface diseases

Background

The harmful effect of aerial fine particulate matter（PM2.5）has been a serious public health issue and has attracted worldwide attention, especially in developing countries.

Main Text

Numerous previous clinical and experimental studies have demonstrated that PM2.5 has a clear pathogenic effect on diseases related to the respiratory and cardiovascular systems. Recent researches have pointed out that PM2.5 plays a pivotal role in the occurrence and progression of ocular surface diseases. The current studies have shown that PM2.5 may promote the appearance of conjunctivitis, keratitis, blepharitis, dry eye, meibomian gland dysfunction（MGD） and other ocular surface diseases through regulating a series of mechanisms such as inflammation, immune reaction, oxidative stress, autophagy, cell migration, and epigenetics.

Conclusions

This review aims to summarize the current research progress on the pathogenic mechanism of PM2.5-related ocular surface diseases.

[Impact of the Lubrizol Rouen plant fire of September 26, 2019 on ophthalmic emergency room visits]

INTRODUCTION

A fire at the Lubrizol chemical factory in Rouen on September 26, 2019 generated a huge column of smoke directed northeast toward the city. As the eye might be particularly affected by the smoke and other toxic emissions from the fire, we assessed the impact of this industrial and ecological disaster on irritative eye surface disease in the week following the accident.

MATERIALS AND METHODS

We retrospectively collected the medical data of the patients who presented to the Ophthalmology Emergency Department (OED) of Rouen University Hospital (the only OED open during the days following the accident) during the week following the fire (W1). We compared these data with those of patients who presented during the week before the fire (W-1). We also collected data on patients presenting to the ED in general during W-1 and W1, including the number of visits directly related to the fire.

RESULTS

361 patients presented to the OED during W1 following the fire, compared with 384 in W-1. Of these patients, 83 (23%) had ocular surface disease in W1, versus 76 (20%) in W-1. Conjunctivitis was found in 54 patients in W1 (39 viral, 9 allergic, 6 undetermined) versus 44 in W-1 (27 viral, 12 allergic, 5 undetermined). A dry irritative syndrome was present in 29 patients in W1 versus 32 in W-1. Only 4 patients directly attributed their symptoms to the fire: 2 viral conjunctivitis, 1 allergic conjunctivitis and 1 worried patient (at D2, D5, D7 and D7 following the fire respectively).

DISCUSSION

The number of emergency eye consultations did not change in the week following the Lubrizol factory fire (except for a decrease the day of the accident, related to the lock-down). There was a higher number of consultations in W1 for conjunctivitis, mostly viral in appearance and probably not directly related to the fire. The number of consultations for dry irritative syndrome was comparable between the two periods. Despite major media coverage of the event at the national level and a very high level of concern among the population, the fire does not seem to have had an effect on OED activity at Rouen University Hospital, nor on general ED visits. The stay-at-home order on the first day may have had a protective effect, avoiding direct exposure to smoke. The long-term consequences of the soot deposits on the ground as the smoke cloud passed over remain undetermined and are under surveillance. A review of the literature on the ocular consequences of industrial accidents is presented.

CONCLUSION

The Ophthalmology Emergency Department did not record increased activity in the week following the Lubrizol Rouen fire, and ocular surface disease did not give rise to more consultations than the week before the fire. This suggests that there was no or minimal immediate ocular toxicity of the smoke from the fire.

Association Between PM2.5 Exposure Level and Primary Open-Angle Glaucoma in Taiwanese Adults: A Nested Case-Control Study

Primary open-angle glaucoma (POAG) is the most common type of glaucoma. However, little is known about POAG in adults and exposure to air pollution. The current study aims to investigate whether exposure to particulate matter with a mass median aerodynamic diameter of ≤2.5 μm (PM_2.5) is associated with POAG diagnosis. Patient data were obtained from the Longitudinal Health Insurance Database 2010 (LHID2010) of Taiwan for the 2008–2013 period. PM_2.5 concentration data, collected from the Ambient Air Quality Monitoring Network established by the Environmental Protection Administration of Taiwan, were categorized into four groups according to World Health Organization (WHO) exposure standards for PM_2.5. We estimated the odds ratios (ORs) and 95% CIs for risk factors for POAG with logistic regression. The OR of per WHO standard level increase was 1.193 (95% CI 1.050–1.356). Compared with the normal level, the OR of WHO 2.0 level was 1.668 (95% CI 1.045–2.663, P < 0.05). After excluding confounding risk factors for POAG in this study, we determined that increased PM_2.5 exposure is related to POAG risk (ORs > 1, P < 0.05). In this study, PM_2.5 was an independent factor associated with open-angle glaucoma. Further research is required to better understand the mechanisms connecting PM_2.5 and open-angle glaucoma.

Correlation between Keratoconus and Pollution

Introduction: Keratoconus is a corneal ectasia with multifactorial origin. Three risk factors for keratoconus are currently recognized: ultraviolet rays (UV), eye rubbing and atopy. In the current literature, other factors are evoked such as pollution, whose role in the physiopathology of keratoconus is unclear. The effects of particles matter (PM) 2.5 and 10 are the most studied and questioned in the scientific literature.Material and method: A correlation study was carried out to determine the influence of pollution on keratoconus. Fine particulate matter levels were measured according to available WHO data and were correlated with the prevalences of epidemiological studies. These measures were included in the study according to strict selection criteria.Results: The mean pollution rate of the selected studies was 29.1 ± 24.3 μg/m³ for PM_2.5 and 57.2 ± 56.2 μg/m³ for PM₁₀. The Pearson test shows a moderate correlation between the prevalence of keratoconus and the levels of PM_2.5 (R = 0.51; p = .022) and a strong correlation with the levels of PM₁₀ (R = 0.71; p < .001).Discussion: Fine particulate matter appears to be an emerging risk factor for keratoconus. They are thought to act indirectly by exacerbating known risk factors such as atopy and eye rubbing. And could have a direct action on the cornea by increasing the apoptosis of epithelial cells and interacting directly with the structure of collagen of the stroma.

Association of the Indoor Environment With Dry Eye Metrics

Importance

The ocular surface is continuously exposed to the environment. Although studies have focused on associations between outdoor environmental conditions and dry eye, information on associations between the indoor environment and dry eye is lacking.

Objective

To determine associations between the indoor environment and dry eye.

Design, Setting, and Participants

This prospective cross-sectional study sample of 97 veterans with a wide range of dry eye metrics was recruited from the Miami Veterans Affairs Healthcare eye clinic from October 19, 2017, to August 30, 2018. Dry eye metrics were first evaluated in the clinic, followed by indoor home environmental metrics within 1 week using a handheld particle counter. Data were analyzed from October 19, 2017, to August 30, 2018.

Main Outcomes and Measures

Symptoms of dry eye were assessed with standardized questionnaires. Dry eye signs were assessed via standard examination. Indoor environmental metrics included temperature, humidity, and particulate matter mass and count.

Results

Of the 97 participants included in the analysis, 81 (84%) were men, with a mean (SD) age of 58.2 (11.9) years. Dry eye symptoms were in the moderate range with a mean (SD) Ocular Surface Disease Index (OSDI) score of 31.2 (23.6). Humidity was associated with worse symptoms and signs, including OSDI score (r = 0.30 [95% CI, 0.07-0.49]; P = .01), inflammation (r = 0.32 [95% CI, 0.10-0.51]; P = .01), Schirmer score (r = -0.25 [95% CI, -0.45 to 0.02]; P = .03), eyelid vascularity (r = 0.27 [95% CI, 0.05-0.47]; P = .02), and meibomian gland dropout (r = 0.27 [95% CI, 0.05-0.47]; P = .02). In multivariate analyses, particulate matter of 2.5 μm or less (PM2.5) was associated with dry eye metrics when adjusted for demographic characteristics, comorbidities, medications, and interaction variables. For example, a 1-unit increase in instrumented PM2.5 level was associated with a 1.59 increase in the OSDI score (95% CI, 0.58-2.59; P = .002), a 0.39 reduction in Schirmer score (95% CI, -0.75 to -0.03; P = .04), a 0.07 increase in meibomian gland dropout (95% CI, 0.01-0.13; P = .02), and a 0.06 increase in inflammation (95% CI, 0.02-0.11; P = .009).

Conclusions and Relevance

When adjusting for humidity, this study found that increased particulate matter exposure was associated with worse dry eye metrics. Humidity was positively associated with dry eye metrics, potentially because higher humidity increases microbial growth and particulate matter size and mass.

Impact of Air Pollution and Weather on Dry Eye

Air pollution has broad effects on human health involving many organ systems. The ocular surface is an excellent model with which to study the effects of air pollution on human health as it is in constant contact with the environment, and it is directly accessible, facilitating disease monitoring. Effects of air pollutants on the ocular surface typically manifest as dry eye (DE) symptoms and signs. In this review, we break down air pollution into particulate matter (organic and inorganic) and gaseous compounds and summarize the literature regarding effects of various exposures on DE. Additionally, we examine the effects of weather (relative humidity, temperature) on DE symptoms and signs. To do so, we conducted a PubMed search using key terms to summarize the existing literature on the effects of air pollution and weather on DE. While we tried to focus on the effect of specific exposures on specific aspects of DE, environmental conditions are often studied concomitantly, and thus, there are unavoidable interactions between our variables of interest. Overall, we found that air pollution and weather conditions have differential adverse effects on DE symptoms and signs. We discuss these findings and potential mitigation strategies, such as air purifiers, air humidifiers, and plants, that may be instituted as treatments at an individual level to address environmental contributors to DE.

Effect and underlying mechanisms of airborne particulate matter 2.5 (PM2.5) on cultured human corneal epithelial cells

Health problems caused by airborne particulate matter with a diameter less than 2.5 (PM2.5), especially in the respiratory system, have become a worldwide problem, but the influence and mechanisms of PM2.5 on the ocular surface have not been sufficiently elucidated. We investigated in vitro the onset and pathogenesis of corneal damage induced by PM2.5. Two types of PM2.5 samples originating from Beijing (designated #28) and the Gobi Desert (designated #30) were added to the culture medium of immortalized cultured human corneal epithelial cells (HCECs) to examine the effects on survival rates, autophagy, and proinflammatory cytokine production. Both types of PM2.5 significantly reduced the HCEC survival rate in a concentration-dependent manner by triggering autophagy. In particular, compared with #30, #28 induced much more severe damage in HCECs. Physical contact between PM2.5 and HCECs was not a primary contributor to PM2.5-induced HCEC damage. Among the 38 proinflammatory cytokines examined in this study, significant increases in the granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin-6 levels and a significant reduction in the interleukin-8 level were detected in culture medium of PM2.5-exposed HCECs. Simultaneous addition of a GM-CSF inhibitor, suramin, alleviated the HCEC impairment induced by PM2.5. In conclusion, PM2.5 induces HCEC death by triggering autophagy. Some cytokines that are released from HCECs, including GM-CSF, may be involved in HCEC damage caused by PM2.5 exposure.

The burden of acute conjunctivitis attributable to ambient particulate matter pollution in Singapore and its exacerbation during South-East Asian haze episodes

INTRODUCTION

Urban air quality in South-East Asia is influenced by local and transboundary sources of air pollutants. Research studies have well characterized the short-term effects of air pollution on cardiovascular and respiratory health but less so on ocular health. We investigated the relationship between air pollution and acute conjunctivitis in Singapore, a tropical city-state located in South-East Asia.

METHODS

Assuming a negative-binomial distribution, we examined the short-term associations between all-cause acute conjunctivitis reports from 2009 to 2018 and contemporaneous ambient air pollutant concentrations using a time-series analysis. In separate pollutant models for PM_2.5 and PM₁₀, we fitted fractional polynomials to investigate the linearity between air pollutant exposures and conjunctivitis, adjusting for long-term trend, seasonality, climate variability, public holidays, immediate and lagged exposure effects, and autocorrelation.

RESULTS

There were 261,959 acute conjunctivitis reports over the study period. Every 10 μg/m³ increase in PM_2.5 was associated with a 3.8% (Incidence Rate Ratio (IRR): 1.038, 95% Confidence Interval (CI): 1.029-1.046, p < 0.001) cumulative increase in risk of conjunctivitis over the present and subsequent week. Every 10 μg/m³ increase in PM₁₀ was associated with a 2.9% (Incidence Rate Ratio (IRR): 1.029, 95% Confidence Interval (CI): 1.022-1.036, p < 0.001) cumulative increase in risk of conjunctivitis over the present and subsequent week. Acute conjunctivitis reports exhibited an inverse dependence on ambient air temperature and relative humidity variability. Approximately 3% of all acute conjunctivitis reports were attributable to PM_2.5. Particulate matter attributed acute conjunctivitis was disproportionately higher during transboundary haze episodes.

CONCLUSION

Our study strengthens the evidence linking particulate matter exposure to an increased risk of conjunctival disease, with a disproportionately higher disease burden during South-East Asia transboundary haze episodes. Our findings underscore the importance of reducing the health impact of indigenous and transboundary sources of ambient particulate matter pollution.

Different adverse effects of air pollutants on dry eye disease: Ozone, PM2.5, and PM10

To date, there have been no well-organized clinical studies evaluating which air pollutants affect dry eye disease (DED). In this study, we investigated changes in the clinical parameters of DED according to exposure to outdoor air pollutants, including PM_2.5 (particulate matter with an aerodynamic diameter of less than 2.5 μm), PM₁₀ (less than 10 μm), and ozone. A prospective observational study was conducted on 43 DED patients who had used the same topical eye drop treatment between 2016 and 2018 in South Korea. Ocular surface discomfort index (OSDI) score, tear film break-up time (TBUT), corneal fluorescein staining score (CFSS), and tear secretion were measured during each visit. Air pollution data of ambient PM₁₀, PM_2.5, and ozone, based on the patients' address, were obtained, and mean concentrations were computed for one day, one week, and one month before the examination. The relationships between air pollutants and DED were analyzed in single- and multi-pollutant models adjusted for demographic and clinical factors. In the multi-pollutant model, the OSDI score was positively correlated with ozone and PM_2.5 exposure [ozone: β(exposure for 1 day/1 week) = 0.328 (95% CI: 0.161-0.494)/0.494 (0.286-0.702), p < 0.001/<0.001, per 1 ppb increase; PM_2.5: β(1 day/1 week) = 0.378 (0.055-0.699)/0.397 (0.092-0.703), p = 0.022/ = 0.011, per 1 μg/m³ increase], and tear secretion decreased with increased ozone exposure [ozone: β(1 week/1 month) = -0.144 (-0.238 to -0.049)/-0.164 (-0.298 to -0.029), p = 0.003/ = 0.017, per 1 ppb increase]. Interestingly, increased PM₁₀ exposure was only associated with decreased TBUT [β(1 day/1 week/1 month) = -0.028(-0.045 to -0.011)/-0.029(-0.046 to -0.012)/-0.023(-0.034 to -0.006), p = 0.001/ = 0.001/ = 0.018, per 1 μg/m³ increase]. Tear secretion and CFSS were not associated with PM₁₀ exposure. Increased ozone and PM_2.5 exposure led to aggravated ocular discomfort, and increased PM₁₀ concentration aggravated tear film stability in patients with DED. Thus, each air pollutant may aggravate DED via different mechanisms of action.

Perfluorooctanoic acid in indoor particulate matter triggers oxidative stress and inflammation in corneal and retinal cells

To investigate the particle size distribution of particulate matter and the concentration of specific perfluorinated compounds in indoor dust samples from several locations. Then, we used cell-based assays to investigate the effect of perfluorinated compounds on human corneal epithelial (HCEpiC), endothelial cells (HCEC) and retinal pigment epithelial cells (RPE). Indoor dust samples were collected at five different locations and PM_50–10, PM_10–2.5, and PM_2.5–1 were fractionized. The presence and levels of 8:2 fluorotelomer alcohol, 10:2 fluorotelomer alcohol, and perfluorooctanoic acid were detected by gas chromatography–mass spectrometry. The effect of perfluorooctanoic acid on the activation of reactive oxygen species, transepithelial resistance as well as the expression of interleukin (IL)-6 and IL-8 were determined. The basolateral media of human corneal epithelial or human corneal endothelial cells were used to treat human corneal endothelial or retinal pigment epithelial cells, respectively to indicate the potential of ocular surface inflammation may result in retinal inflammation. Among perfluorinated compounds, only perfluorooctanoic acid was detected in all indoor dust samples. Perfluorooctanoic acid had the highest concentration among all perfluorinated compounds in the samples. Exposure to perfluorooctanoic acid impaired tight junction sealing and increased the levels of reactive oxygen species in human corneal epithelial cells. In human corneal epithelial cells, secretion of IL-6 and IL-8 in both apical and basolateral media was promoted significantly by perfluorooctanoic acid treatment. Stimulation with the basolateral media from perfluorooctanoic acid-treated human corneal epithelial cells induced inflammation in human corneal endothelial cells. The treatment of retinal pigment epithelial cells with the basolateral media from stimulated human corneal endothelial cells also elicited the secretion of proinflammatory cytokines. The results indicate that perfluorooctanoic acid exposure impaired the tight junction of corneal cells and caused inflammatory reactions in the retina. Exposure of the cornea to perfluorooctanoic acid contained in particulate matter might induce oxidative stress and inflammation in the retina and represent a risk factor for age-related macular degeneration.

Prediction Model for Dry Eye Syndrome Incidence Rate Using Air Pollutants and Meteorological Factors in South Korea: Analysis of Sub-Region Deviations

Here, we develop a dry eye syndrome (DES) incidence rate prediction model using air pollutants (PM₁₀, NO₂, SO₂, O₃, and CO), meteorological factors (temperature, humidity, and wind speed), population rate, and clinical data for South Korea. The prediction model is well fitted to the incidence rate (R² = 0.9443 and 0.9388, p < 2.2 × 10⁻¹⁶). To analyze regional deviations, we classify outpatient data, air pollutant, and meteorological factors in 16 administrative districts (seven metropolitan areas and nine states). Our results confirm NO₂ and relative humidity are the factors impacting regional deviations in the prediction model.

Transcriptomic profiling of human corneal epithelial cells exposed to airborne fine particulate matter (PM2.5)

PURPOSE

To explore the molecular mechanisms of PM_2.5-induced dysfunction in human corneal epithelial cells (HCECs) and the potential role of the plasminogen activator inhibitor type-2 (PAI-2) in PM_2.5-induced autophagy in vitro and in vivo.

METHODS

RNA-Seq was performed to identify the differentially expressed genes (DEGs) in PM_2.5-exposed HCECs compared to unexposed condition, followed by validation via real-time PCR (qRT-PCR). Corneal fluorescein staining and tear secretion were assessed in the PM_2.5-exposed rat model. The expression of PAI-2 and autophagy-related markers were examined via immunoblotting, immunofluorescence staining and/or qRT-PCR in PM_2.5-exposed or unexposed HCECs and rat corneas. PAI-2-knockdown HCECs were generated to study PAI-2's role in the PM_2.5-induced autophagy in HCECs.

RESULTS

A total of 434 DEGs-240 up-regulated and 194 down-regulated-were identified in PM_2.5-exposed HCECs rather than unexposed HCECs. The expression of a few genes related to proliferation, inflammation, and aryl hydrocarbon stimulation were significantly altered by PM_2.5 exposure. PAI-2 expression was up-regulated in PM_2.5-exposed HCECs, sharing a similar fluctuation trend with autophagy-related markers LC3B II and BECN1 according to various exposure periods. Moreover, PAI-2 knockdown significantly suppressed the expression of LC3B and BECN1 in PM_2.5-exposed HCECs. The corneal fluorescein staining was enhanced and tear secretion was significantly reduced in PM_2.5-exposed rat eyes. PAI-2 expression was also increased in PM_2.5-exposed rat corneas, together with the up-regulation of several autophagy-related markers.

CONCLUSION

The present study identified the altered expression of hundreds of genes in PM_2.5-exposed HCECs, which suggests the importance of PM_2.5 for cornea health. The involvement of PAI-2 was discovered in the PM_2.5-induced autophagy in HCECs as well as likely in rat corneas, which implied that PAI-2 may become a potential target of clinical treatment of PM_2.5-associated ocular surface diseases.

Characterization of Meibomian Gland Atrophy and the Potential Risk Factors for Middle Aged to Elderly Patients With Cataracts

Purpose

To explore the characteristics of meibomian gland (MG) atrophy and its potential risk factors in the age-related cataract population.

Methods

Patients who underwent cataract surgery at age 40 or older were enrolled in this study. Preoperative clinical measurement records were obtained, including lipid layer thickness, tear meniscus height, noninvasive breakup time, and meiboscore. The meibomian gland atrophy ratio (MGAR) was measured by the ImageJ software. Univariate regression analysis and multivariate regression analysis were used to analyze the risk factors for MG atrophy.

Results

Female patients had less atrophy of the MG compared with male patients. The MGAR, meiboscore, tear meniscus height (TMH), and lipid layer thickness (LLT) gradually increased with age. However, the noninvasive breakup time decreased with age. The multivariate regression analysis indicated that dyslipidemia and increased triglyceride levels were identified as independent protective factors for MG atrophy. We further stratified the model by sex, and the following results showed only in the female patients with dyslipidemia and increased triglyceride had decreased MG atrophy. No significant correlation was observed between MG atrophy and tear film parameters including TMH, noninvasive breakup time, and LLT.

Conclusions

Our study suggests that age, sex, and diabetes are potential risk factors for MG atrophy. In addition, dyslipidemia and increased triglyceride levels are independent protective factors for MG atrophy in the elderly female population.

Translational Relevance

MG atrophy is the leading cause of meibomian gland dysfunction. To study the characteristics and risk factors of MG atrophy in cataract patients would be helpful to predict and prevent postoperative development of MGD.

A polymer-based technique to remove pollutants from soft contact lenses

PURPOSE

To demonstrate an alternative to the rinse and rub (RR) method for cleaning pollutants from the exterior surface of soft contact lenses. This proposed technique is termed Polymer on Polymer Pollutant Removal (PoPPR), which utilizes the elastic properties of polydimethylsiloxane (PDMS) to physically remove contaminants from contact lens surfaces through non-adhesive unpeeling.

METHODS

Three different ratios of setting agent to polymer PDMS (1:30, 1:40, and 1:50) were evaluated using the PoPPR method against the control method of RR with a commercial multi-purpose lens cleaning solution. Three simulated pollutants of different sizes: pollen (25-40 μm), microbeads (1-5 μm), and nanoparticles (5-10 nm), were used to test the effectiveness of both cleaning methods. The fraction of pollutants removed from each contact lens was recorded and evaluated for significance.

RESULTS

PDMS 1:40 was found to be the optimal ratio for lens cleaning using the PoPPR method. For larger particles (>10 μm), no difference was observed between conventional RR and proposed PoPPR method (p > 0.05). However, the new PoPPR technique was significantly better at removing small PM_2.5 particles (<2.5 μm) compared to the RR method, specifically for microbeads (p = 0.006) and nanoparticles (p < 0.001).

CONCLUSION

This proof-of-concept work demonstrates that the PoPPR method of cleaning contact lenses is as effective as the conventional cleaning method for larger particles such as pollen. The PoPPR method is more effective at removing extremely fine particulate pollutants, including microplastics and nanoparticles. This method offers a potentially more efficient cleaning protocol that could enhance the safety, health, and comfort of contact lens users, especially those living in regions with significant air pollution.

Exposure to Traffic-Related Particulate Matter 2.5 Triggers Th2-Dominant Ocular Immune Response in a Murine Model

Ambient particulate matter (PM), a major component of air pollution, aggravates ocular discomfort and inflammation, similarly to dry eye disease (DED) or allergies. However, the mechanism(s) by which PM induces the ocular inflammatory response is unknown. This study investigated the immunological response of traffic-related fine particulate matter (PM_2.5) on the ocular surface in a murine model. C57BL/6 mice were exposed by topical application to PM_2.5 or vehicle for 14 days to induce experimental environmental ocular disease. Corneal fluorescein staining and the number of ocular inflammatory cells were assessed in both groups. The expression of IL-1β, IL-6, tumor necrosis factor (TNF)-α, and mucin 5AC (MUC5AC) in the ocular surface were evaluated by real-time PCR. An immunohistochemical assay evaluated apoptosis and goblet cell density. ELISA was used to determine the levels of serum IgE and cytokines of Type 1 helper (Th1) and Type 2 helper (Th2) cells after in vitro stimulation of T cells in the draining lymph nodes (LNs). Exposure to traffic-related PM_2.5 significantly increased corneal fluorescein staining and cellular toxicity in the corneal epithelium compared with the vehicle control. A significant increase in the number of CD11b+ cells on the central cornea and mast cells in the conjunctiva was observed in the PM_2.5 group. Exposure to PM_2.5 was associated with a significant increase in the corneal or conjunctival expression of IL-1β, IL-6, TNF, and MUC5AC compared to the vehicle, and increased maturation of dendric cells (DCs) (MHC-II^highCD11c⁺) in draining LNs. In addition, PM_2.5 exposure increased the level of serum IgE and Th2 cytokine production in draining LNs on day 14. In conclusion, exposure to traffic-related PM_2.5 caused ocular surface damage and inflammation, which induced DC maturation and the Th2-cell-dominant allergic immune response in draining LNs.

Association of Ambient Particulate Matter Exposure with the Incidence of Glaucoma in Childhood

PURPOSE

We investigated whether exposure to air pollution, particularly to particles with a mass median aerodynamic diameter of ≤10 μm (PM₁₀), is associated with diagnosis of childhood glaucoma.

DESIGN

Retrospective cohort study.

METHODS

From the National Health Insurance Service-National Sample Cohort, a total of 9004 infants born between January 2002 and December 2002 were included and followed-up for an 11-year period (2003-2012). Patients with glaucoma were defined as International Classification of Diseases, 10th revision code H40. Exposure levels of PM₁₀ were extrapolated using geographic information systems, and individual exposure levels were assigned.

RESULTS

During the study period, glaucoma occurred in 85 patients (0.94%). The probability of developing childhood glaucoma increased with the increase in PM₁₀ quartiles. Increases in 1 μg/m³ of long-term PM₁₀ were significantly associated with increased hazard ratios (HRs) for childhood glaucoma (HR = 1.22 [95% confidence interval {CI} 1.15-1.28]). Compared with risk of the lowest PM₁₀ exposure group (quartile 1), the adjusted HRs for childhood glaucoma were significant in the highest PM₁₀ exposure group of quartile 4 (HR = 2.84 [95% CI 1.37-5.89]) in model 3. Regarding the long-term PM₁₀ exposure, the estimated hazard was considerably elevated in quartile 4 (HR = 6.61 [95% CI 2.96-14.75]).

CONCLUSIONS

Short-term and long-term exposure to PM₁₀ was associated with the incidence of childhood glaucoma. This finding confirms previous reports on the link between air pollution and ocular disease and suggests that PM₁₀ exposure may be a risk for childhood glaucoma.

Biomarkers of exposure, effect, and susceptibility in occupational exposure to traffic-related air pollution: A review

There is a well-recognized association between environmental air pollution exposure and several human diseases. However, the relationship between diseases related to occupational air pollution exposure on roads and high levels of traffic-related air pollutants (TRAPs) is less substantiated. Biomarkers are essential tools in environmental and occupational toxicology, and studies on new biomarkers are increasingly relevant due to the need to determine early biomarkers to be assessed in exposure conditions. This review aimed to investigate the main advances in the biomonitoring of subjects occupationally exposed to air pollution, as well as to summarize the biomarkers of exposure, effect, and susceptibility. Furthermore, we discuss how biomarkers could be used to complement the current application of methods used to assess occupational exposures to xenobiotics present in air pollution. The databases used in the preparation of this review were PubMed, Scopus, and Science Direct. Considering the significant deleterious effects on health associated with chronic occupational exposure to xenobiotics, this topic deserves attention. As it is difficult to avoid occupational exposure to TRAPs, biomonitoring should be applied as a strategy to reduce the toxic effects of workplace exposure.

Topical Application of Liriope platyphylla Extract Attenuates Dry Eye Syndrome Induced by Particulate Matter

Particulate matter (PM) is a type of air pollutant that poses a risk to human health. In the ocular system, PM causes or aggravates dry eye syndrome (DES) by damaging the corneal and conjunctival epithelia. Liriope platyphylla has been used traditionally as an expectorant, antitussive agent, and tonic in Korea. However, the effects of Liriope platyphylla extract (LPE) on PM-induced ocular damage have not been elucidated. In this study, we evaluated the in vivo protective effect of LPE against PM-induced DES in rats. Topical administration of LPE attenuated the PM-induced decrease in tear volume and reduced corneal epithelial irregularity and damage. LPE also protected against PM-induced disruption of the corneal mucin-4 layer and reduction in the conjunctival goblet cell density. These findings suggest that LPE has protective effects against PM-induced DES.

PM2.5 and NOx exposure promote myopia: clinical evidence and experimental proof

Myopia is caused by complex genetic and environmental factors. However, information regarding the effect of long-term exposure to air pollutants on the risk of development of myopia is lacking. We collected data from two linked databases: the Taiwan National Health Insurance Research Database (NHIRD) and the Taiwan Air Quality-Monitoring Database (TAQMD). A total of 15,822 children (16.3%) were diagnosed with myopia within the cohort. The incidence rate of myopia increased with exposure to increasing concentrations of particulate matter (PM2.5) and nitrogen oxides (NOx), increasing from 15.8 to 24.5 and from 13.7 to 34.4, per 1000 person-years, respectively. The adjusted hazard ratio for myopia increased with elevated PM2.5 and NOx exposure concentrations in Q4 to 1.57 and 2.60, respectively, compared to those exposed to the corresponding concentrations in Q1. In the animal experiments, PM2.5 induced myopia in hamsters by enhancing inflammation and was inhibited by resveratrol treatment compared to the control group. The change in axial length in the PM2.5 group was 0.386 ± 0.069 mm versus 0.287 ± 0.086 mm in the control group and 0.257 ± 0.059 mm in the PM2.5 + resveratrol group. We provide both clinical and experimental correlations that exposure to ambient air pollutants is associated with the pathogenesis of myopia.

A Murine Model of Acute Allergic Conjunctivitis Induced by Continuous Exposure to Particulate Matter 2.5

Purpose

Several pieces of epidemiologic evidence have indicated PM2.5 (particulate matter with a diameter of 2.5 μm or less) as a causing factor of allergic conjunctivitis, but without experimental elucidation of mechanism. In the present study, PM2.5 in solution was directly applied to the mouse ocular surface to elucidate whether PM2.5 might cause allergic conjunctivitis, and its underlying mechanisms were analyzed.

Methods

ICR mice were challenged for 18 consecutive days with eye drops containing PM2.5 at 3.2, 6.4, and 12.8 mg/mL in 0.9% NaCl saline, along with the controls prepared in parallel without PM2.5 and another control group treated with both PM2.5 at 12.8 mg/mL and artificial tears. On day 19, the whole eyes and meibomian glands were harvested for histopathological analyses and assessment of clinical scoring, tear volume, tear breakup time, and tear ferning. Furthermore, goblet cells by periodic acid Schiff stain and infiltrated eosinophils by Giemsa stain were quantified and compared among study groups.

Results

Clinical scoring showed more eyelid edema, tearing, and scratching behaviors, with longer tear breakup time under the influence of increased PM2.5 concentrations. Tear ferning assay showed less tear crystal formation and decreased crystal branches after exposure to PM2.5. In addition, higher goblet cell density in the upper palpebral conjunctiva and extensive eosinophil infiltration in the entire conjunctiva and in the meibomian glands were induced by PM2.5.

Conclusions

These results demonstrate that PM2.5 can induce symptoms similar to clinical allergic conjunctivitis and that the murine acute allergic conjunctivitis model can be induced by direct exposure to PM2.5.

Management Of Glaucoma In Developing Countries: Challenges And Opportunities For Improvement

Glaucoma is the leading cause of blindness in the developed and developing world. Not only is the clinical impact of this disease considerable, but associated economic and humanistic burdens - affecting patients, caregivers, and society - are substantial. Since glaucoma is an age-related disorder and populations in many developing countries are aging at a faster pace than in the developed world, increasing attention is being focused on ways to ameliorate the burdens of illness. In this paper, we examine the burdens of glaucoma with particular focus on developing countries, discuss some of the challenges that exist in delivering optimal glaucoma management within budget constraints, and bring into perspective how we could improve current healthcare systems, leverage technology, and strike an appropriate balance between cost and quality of care, thereby offering considerations to payors and policymakers in these countries that may result in longer-term cost savings, while concurrently striving to achieve the WHO Vision on the prevention of blindness and visual impairment.

Human Ocular Surface Particulate Composition in the Clinical Versus Home Environment

PURPOSE

Our eyes are chronically exposed to airborne particulate matter shown to adversely affect the ocular surface. This research examines size, type (organic vs. inorganic), and elemental composition of particles recovered from the ocular surface in 2 environments and their associations with dry eye (DE) metrics.

METHODS

Particles were recovered from the right eye using Schirmer strips obtained both in the clinic and home environments 9 ± 8 days apart. Particle size and elemental composition were assessed using scanning electron microscopy and energy dispersive spectroscopy. The paired t test was used to evaluate the differences in the size and types of ocular surface particles recovered from the clinic and home settings. Associations of particle size and type with home environmental conditions and DE measures were evaluated using correlation analyses.

RESULTS

The mean age of the 15 patients was 56 years, standard deviation (±) 12 years; 93% were men and 53% self-identified as white. Size, type, and elemental composition did not vary significantly between clinic and home. Particle surface area was marginally associated with home indoor temperature (25 °C ± 2, ρ=-0.53, P = 0.06) and significantly associated with the select DE signs: tear osmolality (304 mOsm/L ± 14, ρ= -0.60, P = 0.02), inflammation (0.7 ± 0.8, ρ = 0.53, P = 0.04), and tear breakup time (7 seconds ± 3, ρ = 0.56, P = 0.03).

CONCLUSIONS

Ocular surface particles were consistently detected across 2 different environments. Greater particle area detected on Schirmer strips correlated with some DE measures, suggesting that particles detected on the ocular surface may affect eye health.

Effects of fine particulate matter on the ocular surface: An in vitro and in vivo study

Exposure to ambient fine particulate matter (fine PM) pollution has been previously associated with ocular surface diseases. But, to the best of our knowledge, the in vivo long-term effects of fine PM on the ocular surface have not been investigated. We aimed to evaluate the effects of fine PM on cultured human corneal epithelial (HCE) cells and on the ocular surfaces of mice, with standard reference material of fine PM(SRM 2786). We applied fine PM suspension to the eyes of C57BL/6 mice for up to 6 months. In vivo examinations, including tear secretion, tear film break-up time (TBUT) and corneal fluorescein staining, were performed in the 3^rd and 6^th month. At the end of the in vivo study, the corneal histological changes and conjunctival goblet cells were examined by staining, and cytokines in tissue were also detected. In addition, HCE cells were treated with fine PM for 12 h and 24 h. Then, cell apoptosis and reactive oxygen species (ROS) formation was detected. We found that fine PM damages the mouse eye in a dose- and time-dependent manner. In mice, the tear secretion and tear film break-up time were significantly reduced, along with the development of corneal epithelial damage, apoptosis of conjunctival epithelial cells and hypoplasia of conjunctival goblet cells. In addition, IL-18, IL-22, IL-23 and MCP-1 were increased in both conjunctiva and cornea of the fine PM-treated animals. Furthermore, increased apoptosis and ROS production were observed in time- and dose-dependent manner in HCE cells after fine PM exposure for 12 h and 24 h. Our results indicate that fine PM is cytotoxic to both HCE cells and the ocular surface. Long-term topical application of fine PM suspension in mice results in ocular surface changes that are similar to those observed with dry eye.

Air pollutant particulate matter 2.5 induces dry eye syndrome in mice

In this study, we explored the effects of particulate matter 2.5 (PM_2.5) eye drops on the ocular surface structure and tear function in mice and established a novel animal model for dry eye research. We found that, following treatment with PM_2.5, the tear volume and, the tear film break-up time showed statistical differences at each time point (P < 0.05). The FL score of the PM_2.5-treated group was higher than that of others (P < 0.05). The average number of corneal epithelial layer cells in groups A and B was significantly lower than that in group C (P < 0.05). Scanning electron microscopy and transmission electron microscopy revealed that the number of corneal epithelial microvilli and corneal desmosomes was drastically reduced in group C. PM_2.5 induced apoptosis in the corneal superficial and basal epithelium and led to abnormal differentiation and proliferation of the ocular surface with higher expression levels of Ki67 and a reduced number of goblet cells in the conjunctival fornix in group C. PM_2.5 significantly increased the levels of TNF-α, NF-κB p65 (phospho S536), and NF-κB in the cornea. Thus, the topical administration of PM_2.5 in mice induces ocular surface changes that are similar to those of dry eye in humans, representing a novel model of dry eye.