Fluorophotometric Analysis of the Ocular Surface Glycocalyx in Soft Contact Lens Wearers

Destruction of vascular endothelial glycocalyx during formation of pre-metastatic niches

A special microenvironment called the "pre-metastatic niche" is thought to help primary tumor cells migrate to new tissues and invade them, in part because the normal barrier function of the vascular endothelium is compromised. While the primary tumor itself can promote the creation of such niches by secreting pro-metastatic factors, the underlying molecular mechanisms are still poorly understood. Here, we show that the injection of primary tumor-secreted pro-metastatic factors from B16F10 melanoma or 4T1 breast cancer cells into healthy mice can induce the destruction of the vascular endothelial glycocalyx, which is a polysaccharide coating on the vascular endothelial lumen that normally inhibits tumor cell passage into and out of the circulation. However, when human umbilical vein endothelial cultures were treated in vitro with these secreted pro-metastatic factors, no significant destruction of the glycocalyx was observed, implying that this destruction requires a complex in vivo microenvironment. The tissue section analysis revealed that secreted pro-metastatic factors could clearly upregulate macrophage-related molecules such as CD11b and tumor necrosis factor-α (TNF-α) in the heart, liver, spleen, lung, and kidney, which is associated with the upregulation and activation of heparanase. In addition, macrophage depletion significantly attenuated the degradation of the vascular endothelial glycocalyx induced by secreted pro-metastatic factors. This indicates that the secreted pro-metastatic factors that destroy the vascular endothelial glycocalyx rely primarily on macrophages. Our findings suggest that the formation of pre-metastatic niches involves degradation of the vascular endothelial glycocalyx, which may hence be a useful target for developing therapies to inhibit cancer metastasis.

Diabetes-Associated Hyperglycemia Causes Rapid-Onset Ocular Surface Damage

Purpose

The metabolic alterations due to chronic hyperglycemia are well-known to cause diabetes-associated complications. Short-term hyperglycemia has also been shown to cause many acute changes, including hemodynamic alterations and osmotic, oxidative, and inflammatory stress. The present study was designed to investigate whether diabetes-associated hyperglycemia can cause rapid-onset detrimental effects on the tear film, goblet cells, and glycocalyx and can lead to activation of an inflammatory cascade or cellular stress response in the cornea.

Methods

Mouse models of type 1 and type 2 diabetes were used. Tear film volume, goblet cell number, and corneal glycocalyx area were measured on days 7, 14, and 28 after the onset of hyperglycemia. Transcriptome analysis was performed to quantify changes in 248 transcripts of genes involved in inflammatory, apoptotic, and stress response pathways.

Results

Our data demonstrate that type 1 and type 2 diabetes-associated hyperglycemia caused a significant decrease in the tear film volume, goblet cell number, and corneal glycocalyx area. The decrease in tear film and goblet cell number was noted as early as 7 days after onset of hyperglycemia. The severity of ocular surface injury was significantly more in type 1 compared to type 2 diabetes. Diabetes mellitus also caused an increase in transcripts of genes involved in the inflammatory, apoptotic, and cellular stress response pathways.

Conclusions

The results of the present study demonstrate that diabetes-associated hyperglycemia causes rapid-onset damage to the ocular surface. Thus, short-term hyperglycemia in patients with diabetes mellitus may also play an important role in causing ocular surface injury and dry eye.

The protective role of conjunctival goblet cell mucin sialylation

Gel-forming mucins secreted by conjunctival goblet cells have been implicated in the clearance of allergens, pathogens, and debris. However, their roles remain incompletely understood. Here we show that human and mouse conjunctival goblet cell mucins have Alcian blue-detectable sialic acids, but not sulfates in the steady state. Interestingly, Balb/c mouse strain lacks this sialylation due to a point mutation in a sialyltransferase gene, St6galnac1, which is responsible for sialyl-Tn synthesis. Introduction of intact St6galnac1 to Balb/c restores the sialylation of conjunctival goblet cell mucus. Sialylated mucus efficiently captures and encapsulates the allergen particles in an impenetrable layer, leading to the protection of mice from the development of allergic conjunctivitis. Expression of ST6GALNAC1 and sialyl-Tn is upregulated in humans under conditions with chronic stimuli. These results indicate that the sialylated glycans on the ocular mucins play an essential role in maintaining the conjunctival mucosa by protecting from the incoming foreign bodies such as allergen particles.

Effects of long-term soft contact lens wear on corneal epithelial thickness after small incision lenticule extraction

The present study investigated changes in corneal epithelial thickness after small incision lenticule extraction (SMILE) in patients with long-term preoperative soft contact lens (SCL) wear, the impact of SCL wear on the efficacy of surgical outcomes and the effects of long-term SCL wear on postoperative corneal aberrations. Patients were assigned to three groups according to the duration of SCL wear: Group A, the non-SCL-wearing group; group B, those with SCL wear ≤1 year; and group C, those with SCL wear >1 year. Epithelial thickness was recorded in nine zones by anterior segment optical coherence tomography across a 5-mm diameter before surgery and at 1 week, and 1, 3 and 6 months post-surgery. Corneal epithelial thickness and corneal aberrations among the three groups were compared, as well as the effects of changes in corneal epithelial thickness on postoperative visual acuity and manifest refraction. No significant differences were noted with regard to age or preoperative spherical equivalent among groups A (22 eyes), B (17 eyes) and C (18 eyes). Preoperative corneal epithelial thickness in the inferonasal, inferior and inferotemporal zones was thinner in group B compared with that in group A, and corneal epithelial thickness was thinner in all nine zones in group C compared with that in group A (P<0.05). At all follow-up time points, in the central, nasal, inferonasal, inferior, inferotemporal and temporal areas, the epithelial thickness was thinner in group C compared with that in group A (P<0.05). At 3 months postoperatively, the epithelial thickness was thinner in the inferonasal and inferior sectors in group C compared with that in group B (P<0.05), and at 6 months postoperatively, the epithelial thickness in the inferior region was thinner in group C compared with that in group B (P<0.05). There were no significant differences in visual acuity or manifest refraction among the three groups at all postoperative time points. The total higher-order aberrations were greater in group C compared with those in group A for all time points (P<0.05) and were greater in group C at 1 and 3 months postoperatively compared with those in group B (P<0.05). The spherical aberrations at 3 and 6 months postoperatively were greater in group C compared with those in group A (P<0.05). The coma aberrations were greater in group C compared with those in groups A and B for all time points (P<0.05). In conclusion, long-term SCL wear will result in corneal epithelial thinning, which does not impact visual acuity or manifest refraction after SMILE.

Piperazine ferulate prevents high-glucose-induced filtration barrier injury of glomerular endothelial cells

Filtration barrier injury induced by high glucose (HG) levels leads to the development of diabetic nephropathy. The endothelial glycocalyx plays a critical role in glomerular barrier function. In the present study, the effects of piperazine ferulate (PF) on HG-induced filtration barrier injury of glomerular endothelial cells (GEnCs) were investigated and the underlying mechanism was assessed. Immunofluorescence was used to observe the distribution of the glycocalyx as well as the expression levels of syndecan-1 and Zonula occludens-1 (ZO-1). Endothelial permeability assays were performed to assess the effects of PF on the integrity of the filtration barrier. Protein and mRNA expression levels were measured by western blotting and reverse transcription-quantitative PCR analyses, respectively. In vitro experiments revealed that adenosine monophosphate-activated protein kinase (AMPK) mediated HG-induced glycocalyx degradation and endothelial barrier injury. PF inhibited the HG-induced endothelial barrier injury and restored the expression levels of heparanase-1 (Hpa-1), ZO-1 and occludin-1 by AMPK. In vivo assays demonstrated that PF reduced the expression levels of Hpa-1, increased the expression levels of ZO-1 and attenuated glycocalyx degradation in the glomerulus. These data suggested that PF attenuated HG-induced filtration barrier injury of GEnC by regulating AMPK expression.

Membrane-associated mucins of the human ocular surface in health and disease

Mucins are a family of high molecular weight, heavily-glycosylated proteins produced by wet epithelial tissues, including the ocular surface epithelia. Densely-packed O-linked glycan chains added post-translationally confer the biophysical properties of hydration, lubrication, anti-adhesion and repulsion. Membrane-associated mucins (MAMs) are the distinguishing components of the mucosal glycocalyx. At the ocular surface, MAMs maintain wetness, lubricate the blink, stabilize the tear film, and create a physical barrier to the outside world. In addition, it is increasingly appreciated that MAMs function as cell surface receptors that transduce information from the outside to the inside of the cell. Recently, our team published a comprehensive review/perspectives article for molecular scientists on ocular surface MAMs, including previously unpublished data and analyses on two new genes MUC21 and MUC22, as well as new MAM functions and biological roles, comparing human and mouse (PMID: 31493487). The current article is a refocus for the audience of The Ocular Surface. First, we update the gene and protein information in a more concise form, and include a new section on glycosylation. Next, we discuss biological roles, with some new sections and further updating from our previous review. Finally, we provide a new chapter on MAM involvement in ocular surface disease. We end this with discussion of an emerging mechanism responsible for damage to the epithelia and their mucosal glycocalyces: the unfolded protein response (UPR). The UPR offers a novel target for therapeutic intervention.

Differential Effect of Proinflammatory Cytokines on Corneal and Conjunctival Epithelial Cell Mucins and Glycocalyx

Purpose

Ocular surface mucins and glycocalyx are critical for providing ocular hydration as well lubrication and repelling pathogens or allergens. Elevated levels of tear proinflammatory cytokines in dry eye may have detrimental effect on mucins and glycocalyx. The present study tested the effect of proinflammatory cytokines IL-6, TNF-α, and IFN-γ on membrane-tethered mucins expression, glycocalyx, and viability of ocular surface epithelial cells.

Methods

Stratified cultures of human corneal and conjunctival epithelial cells were exposed to different concentrations of IL-6, TNF-α, and IFN-γ for 24 hours. The mucins gene and protein expressions were quantified by real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA). The glycocalyx was imaged using confocal microscopy after staining with Alexa 488-conjugated wheat germ agglutinin lectin. Apoptotic and necrotic cell death was quantified using flow cytometry.

Results

IL-6, TNF-α, and IFN-γ treatment resulted in a significant increase in mucins (MUC)1 and MUC4 gene and protein expression in human corneal epithelial cells but caused no significant changes in the levels of these mucins in conjunctival epithelial cells. Further, these cytokines decreased MUC16 expression in both corneal and conjunctival epithelial cells. Moreover, no notable change in glycocalyx or apoptotic cell death in corneal and conjunctival epithelial cells was noted with any of the tested cytokines, but IL-6 and TNF-α exposure increased necrotic cell death in corneal and conjunctival epithelial cells, respectively.

Conclusions

Our results demonstrate that proinflammatory cytokines have differential effects on human corneal and conjunctival epithelial cell mucins expression, but do not cause any damage to ocular surface epithelial cell glycocalyx.

A New Perspective on Dry Eye Classification: Proposal by the Asia Dry Eye Society

The 2017 consensus report of the Asia Dry Eye Society (ADES) on the definition and diagnosis of dry eyes described dry eye disease as "Dry eye is a multifactorial disease characterized by unstable tear film causing a variety of symptoms and/or visual impairment, potentially accompanied by ocular surface damage." The report emphasized the instability of tear film and the importance of visual dysfunction in association with dry eyes, highlighting the importance of the evaluation of tear film stability. This report also discussed the concept of tear film-oriented therapy, which stemmed from the definition, and which is centered on provision of insufficient components in each tear film layer and ocular surface epithelium. The current ADES report proposes a simple classification of dry eyes based on the concept of tear film-oriented diagnosis and suggests that there are three types of dry eye: aqueous-deficient, decreased wettability, and increased evaporation. It is suggested that these three types respectively coincide with the problems of each layer: aqueous, membrane-associated mucins, and lipid/secretory mucin. Although each component cannot be quantitatively evaluated with the current technology, a practical diagnosis based on the patterns of fluorescein breakup is recommended. The Asia Dry Eye Society classification report suggests that for a practical use of the definition, diagnostic criteria and classification system should be integrated and be simple to use. The classification system proposed by ADES is a straightforward tool and simple to use, only through use of fluorescein, which is available even to non-dry eye specialists, and which is believed to contribute to an effective diagnosis and treatment of dry eyes.

Why Chain Length of Hyaluronan in Eye Drops Matters

The chain length of hyaluronan (HA) determines its physical as well as its physiological properties. Results of clinical research on HA eye drops are not comparable without this parameter. In this article methods for the assessment of the average molecular weight of HA in eye drops and a terminology for molecular weight ranges are proposed. The classification of HA eye drops according to their zero shear viscosity and viscosity at 1000 s-1 shear rate is presented. Based on the gradient of mucin MUC5AC concentration within the mucoaqueous layer of the tear film a hypothesis on the consequences of this gradient on the rheological properties of the tear film is provided. The mucoadhesive properties of HA and their dependence on chain length are explained. The ability of HA to bind to receptors on the ocular epithelial cells, and in particular the potential consequences of the interaction between HA and the receptor HARE, responsible for HA endocytosis by corneal epithelial cells is discussed. The physiological function of HA in the framework of ocular surface homeostasis and wound healing are outlined, and the influence of the chain length of HA on the clinical performance of HA eye drops is illustrated. The use of very high molecular weight HA (hylan A) eye drops as drug vehicle for the next generation of ophthalmic drugs with minimized side effects is proposed and its advantages elucidated. Consequences of the diagnosis and treatment of ocular surface disease are discussed.

Wheat germ agglutinin-conjugated fluorescent pH sensors for visualizing proton fluxes

Small-molecule fluorescent wheat germ agglutinin (WGA) conjugates are routinely used to demarcate mammalian plasma membranes, because they bind to the cell’s glycocalyx. Here, we describe the derivatization of WGA with a pH-sensitive rhodamine fluorophore (pHRho; pKa = 7) to detect proton channel fluxes and extracellular proton accumulation and depletion from primary cells. We found that WGA-pHRho labeling was uniform and did not appreciably alter the voltage gating of glycosylated ion channels, and the extracellular changes in pH correlated with proton channel activity. Using single-plane illumination techniques, WGA-pHRho was used to detect spatiotemporal differences in proton accumulation and depletion over the extracellular surface of cardiomyocytes, astrocytes, and neurons. Because WGA can be derivatized with any small-molecule fluorescent ion sensor, WGA conjugates should prove useful to visualize most electrogenic and nonelectrogenic events on the extracellular side of the plasma membrane.

Graft Versus Host Disease-Associated Dry Eye: Role of Ocular Surface Mucins and the Effect of Rebamipide, a Mucin Secretagogue

Purpose

The present study was designed to investigate the role of ocular surface glycocalyx and mucins in graft versus host disease (GVHD)-associated dry eye. The ameliorative effect of topical rebamipide, a mucin secretagogue, on GVHD-associated dry eye was also tested.

Methods

A mouse model of allogeneic transplantation was used to induce ocular GVHD with C57BL/6 as donors and B6D2F1 as recipient mice. Phenol red thread method and fluorescein staining was used to quantify tear secretion and corneal keratopathy. At 8 weeks after the allogeneic transplantation, corneas were harvested to perform glycocalyx staining and confocal microscopy. Goblet cell staining was performed using periodic acid Schiff's staining. Corneal and tear film levels of Mucin 1, 4, 16, 19, and 5AC were quantified using ELISA and real-time PCR. Rebamipide was applied topically twice daily to mice eyes.

Results

Allogeneic transplantation resulted in ocular GVHD-associated dry eye characterized by a significant decrease in tear film volume and the onset of corneal keratopathy. Ocular GVHD caused a significant decrease in the area and thickness of corneal glycocalyx. A significant decrease in the goblet cells was also noted. A significant decrease in mucin 4 and 5AC levels was also observed. Topical treatment with rebamipide partially attenuated ocular GVHD-mediated decrease in tear film volume and significantly reduced the severity of corneal keratopathy.

Conclusions

Ocular GVHD has detrimental impact on ocular surface glycocalyx and mucins. Rebamipide, a mucin secretagogue, partially prevents ocular GVHD-associated decrease in tear film and reduces the severity of corneal keratopathy.

Contact lens-related corneal infection: Intrinsic resistance and its compromise

Contact lenses represent a widely utilized form of vision correction with more than 140 million wearers worldwide. Although generally well-tolerated, contact lenses can cause corneal infection (microbial keratitis), with an approximate annualized incidence ranging from ~2 to ~20 cases per 10,000 wearers, and sometimes resulting in permanent vision loss. Research suggests that the pathogenesis of contact lens-associated microbial keratitis is complex and multifactorial, likely requiring multiple conspiring factors that compromise the intrinsic resistance of a healthy cornea to infection. Here, we outline our perspective of the mechanisms by which contact lens wear sometimes renders the cornea susceptible to infection, focusing primarily on our own research efforts during the past three decades. This has included studies of host factors underlying the constitutive barrier function of the healthy cornea, its response to bacterial challenge when intrinsic resistance is not compromised, pathogen virulence mechanisms, and the effects of contact lens wear that alter the outcome of host-microbe interactions. For almost all of this work, we have utilized the bacterium Pseudomonas aeruginosa because it is the leading cause of lens-related microbial keratitis. While not yet common among corneal isolates, clinical isolates of P. aeruginosa have emerged that are resistant to virtually all currently available antibiotics, leading the United States CDC (Centers for Disease Control) to add P. aeruginosa to its list of most serious threats. Compounding this concern, the development of advanced contact lenses for biosensing and augmented reality, together with the escalating incidence of myopia, could portent an epidemic of vision-threatening corneal infections in the future. Thankfully, technological advances in genomics, proteomics, metabolomics and imaging combined with emerging models of contact lens-associated P. aeruginosa infection hold promise for solving the problem - and possibly life-threatening infections impacting other tissues.

The impact of contact lens wear on ocular surface mucins using a novel clinical fluorescence imaging system

PURPOSE

Fluorescein-labelled wheat germ agglutinin (F-WGA) acts as a marker for ocular surface mucins. This clinical study sought to investigate whether the degree of F-WGA fluorescence observed at the ocular surface differed between symptomatic contact lens wearers, asymptomatic contact lens wearers and non-contact lens wearers, using a novel imaging system.

METHODS

Twenty-five participants (10 symptomatic contact lens wearers, 10 asymptomatic contact lens wearers and 5 non-contact lens wearers) attended a single study visit. Photographs of the cornea, bulbar and tarsal conjunctiva were captured following application of F-WGA solution.

RESULTS

The imaging system captured high-resolution images of F-WGA fluorescence at the ocular surface. The degree of fluorescence differed between the ocular surface regions (p < 0.001). A significant difference in fluorescence was observed between participant groups for the cornea (p = 0.01), with both the symptomatic and asymptomatic contact lens wearers showing lower fluorescence than the non-lens wearers. F-WGA associated fluorescence appeared diminished in the lid wiper region of the symptomatic lens wearers, compared to the asymptomatic group (p = 0.025).

CONCLUSION

The use of F-WGA as a clinical marker for ocular surface mucins allows an improved understanding of their distribution across the ocular surface. Contact lens wear appears to negatively impact mucin density across the ocular surface, with the most marked effect on the cornea. F-WGA fluorescence appeared diminished in the lid wiper region for the symptomatic contact lens wearing group, indicating that mechanical interaction in this region may play a role in the aetiology of contact lens discomfort. Given the ability of F-WGA to disclose mucin distribution across the ocular surface it is likely to be a key clinical tool in furthering our understanding of (i) the aetiology of contact lens related discomfort, (ii) contact lens designs/materials to minimise interaction with the ocular surface and (iii) dry eye disease and other ocular surface diseases.

Reconsidering the central role of mucins in dry eye and ocular surface diseases

Mucins are key actors in tear film quality and tear film stability. Alteration of membrane-bound mucin expression on corneal and conjunctival epithelial cells and/or gel-forming mucin secretion by goblet cells (GCs) promotes in ocular surface diseases and dry eye disease (DED). Changes in the mucin layer may lead to enhanced tear evaporation eventually contributing to tear hyperosmolarity which has been associated with ocular surface inflammation. Inflammatory mediators in turn may have a negative impact on GCs differentiation, proliferation, and mucin secretion. This sheds new light on the position of GCs in the vicious circle of DED. As contributor to ocular surface immune homeostasis, GC loss may contribute to impaired ocular surface immune tolerance observed in DED. In spite of this, there are no tools in routine clinical practice for exploring ocular surface mucin deficiency/dysregulation. Therefore, when selecting the most appropriate treatment options, there is a clear unmet need for a better understanding of the importance of mucins and options for their replacement. Here, we comprehensively revisited the current knowledge on ocular surface mucin biology, including functions, synthesis, and secretion as well as the available diagnostic tools and treatment options to improve mucin-associated homeostasis. In particular, we detailed the potential link between mucin dysfunction and inflammation as part of the uncontrolled chronic inflammation which perpetuates the vicious circle in DED.

Aldosterone induces albuminuria via matrix metalloproteinase-dependent damage of the endothelial glycocalyx

Aldosterone contributes to end-organ damage in heart failure and chronic kidney disease. Mineralocorticoid-receptor inhibitors limit activation of the receptor by aldosterone and slow disease progression, but side effects, including hyperkalemia, limit their clinical use. Damage to the endothelial glycocalyx (a luminal biopolymer layer) has been implicated in the pathogenesis of endothelial dysfunction and albuminuria, but to date no one has investigated whether the glomerular endothelial glycocalyx is affected by aldosterone. In vitro, human glomerular endothelial cells exposed to 0.1 nM aldosterone and 145 mMol NaCl exhibited reduced cell surface glycocalyx components (heparan sulfate and syndecan-4) and disrupted shear sensing consistent with damage of the glycocalyx. In vivo, administration of 0.6 μg/g/d of aldosterone (subcutaneous minipump) and 1% NaCl drinking water increased glomerular matrix metalloproteinase 2 activity, reduced syndecan 4 expression, and caused albuminuria. Intravital multiphoton imaging confirmed that aldosterone caused damage of the glomerular endothelial glycocalyx and increased the glomerular sieving coefficient for albumin. Targeting matrix metalloproteinases 2 and 9 with a specific gelatinase inhibitor preserved the glycocalyx, blocked the rise in glomerular sieving coefficient, and prevented albuminuria. Together these data suggest that preservation of the glomerular endothelial glycocalyx may represent a novel strategy for limiting the pathological effects of aldosterone.

Quality of life measures and health utility values among dry eye subgroups

Background

To determine whether quality of life (QOL) and health utility are affected to the same extent among dry eye (DE) patients with short tear film break-up time dry eye (TBUT-DE) with minimal clinical signs were as severe as aqueous-deficient dry eye (ADDE).

Methods

A multicenter cross-sectional study was conducted among DE patients who visited one of 10 eye clinics in Japan. Among the 463 registered patients, this study involved 449 patients with DE who were aged 20 years or older. Ophthalmic examination findings were assessed, including tear film break-up time (TBUT), Schirmer I value, and keratoconjunctival staining score. QOL was evaluated with the Dry Eye-Related Quality-of-Life Score (DEQS; 0 [best], 100 [worst]) and health utility (1 [total health], 0 [worst]) with the Health Utilities Index Mark 3 (HUI-3); scores were stratified by DE subgroup.

Results

Median (interquartile range) of DEQS and HUI-3 scores across all participants were 21.7 (10.0–40.0) and 0.82 (0.69–0.91), respectively. Median (interquartile range) DEQS and HUI-3 scores in the ADDE group were 23.3 (10.0–40.0) and 0.79 (0.69–0.88), respectively; those in the short TBUT-DE group were 23.3 (13.3–38.3) and 0.82 (0.74–0.92), respectively. There were no significant between-group differences in questionnaire scores. Among the ophthalmic examination findings, a weak significant correlation between TBUT, corneal staining score and keratoconjunctival staining score to DEQS; TBUT and Schirmer test values to HUI-3, were seen.

Conclusions

The burden of short TBUT-DE on QOL as assessed by the DEQS and HUI-3 was as severe as that in ADDE. Our findings suggest that clinicians should be aware of the impact of short TBUT-DE on patients QOL and utility values.

Trial registration

University Hospital Medical Information Network (registration no. UMIN 000015890). Registered 10th December 2014, retrospectively registered.

The effect of rebamipide ophthalmic suspension on ocular surface mucins in soft contact lens wearers

PURPOSE

To evaluate the changes in ocular surface mucins with 2%rebamipide ophthalmic suspension treatment in soft contact lens (SCL) wearers. Rebamipide suspension is a mucin secretagogue approved for the treatment of dry eye syndrome in Japan. In this study, the fluorescence intensity of wheat germ agglutinin conjugate of fluorescein (F-WGA) was used as a marker of membrane-associated mucins, and sialic acid concentration in tear fluids as a marker of secreted mucins.

METHODS

Thirty-two eyes of 16 SCL wearers with discomfort were treated with rebamipide suspension at a dose of one drop in each eye four times daily for two weeks. The parameters of clinical efficacy were tear break-up time, fluorescein staining scores for the cornea and conjunctiva, and Schirmer test values. Fluorescence intensities in the central cornea were measured by fluorophotometry after the application of 5% F-WGA solution. Tears collected by Schirmer test strips were analyzed by high-performance liquid chromatography, and the concentrations of sialic acid, total protein, and the four major tear proteins, namely secretory IgA, lactoferrin, lipocalin-1, and lysozyme were measured.

RESULTS

Significant increases in F-WGA fluorescence intensities (p < 0.005) were seen in the corneal surfaces. Sialic acid concentrations increased over time; however, the differences were not statistically significant. Except for a slight increase in kerato-conjunctival staining scores (p < 0.05) and secretory IgA (p < 0.05), no other significant differences were seen among clinical parameters or tear proteins.

CONCLUSIONS

Topical application of rebamipide suspension significantly increased F-WGA intensity, a marker of membrane-associated mucins in SCL wearers.

Diquafosol for Soft Contact Lens Dryness: Clinical Evaluation and Tear Analysis

PURPOSE

To evaluate the efficacy of topical application of 3% diquafosol tetrasodium solution for the treatment of soft contact lens (SCL) wearers with dryness. In addition to clinical tests and subjective symptoms, we assessed the fluorescence intensity of wheat germ agglutinin conjugate of fluorescein (F-WGA) used as a marker of membrane-associated mucins and sialic acid concentration in tear fluids as a marker of secreted mucins.

METHODS

Twelve SCL wearers with dryness symptoms were treated with diquafosol for 4 weeks. Clinical tests included the tear film break-up time (BUT), corneal and conjunctival fluorescein staining scores, and Schirmer values. Subjective symptoms were evaluated by the Dry Eye-Related Quality-of-Life Score (DEQS). Fluorescence intensities in the central cornea were measured by fluorophotometry at 5 minutes after a 5% F-WGA solution was applied to the eye. The tears collected by the Schirmer test strips were analyzed by high-performance liquid chromatography (HPLC), and the concentrations of sialic acid; total protein; and the four major tear proteins secretory IgA, lactoferrin, lipocalin-1, and lysozyme proteins were measured.

RESULTS

Comparing the results before and after diquafosol treatment, BUT (p < 0.01), kerato-conjunctival staining score (p < 0.05), corneal staining score (p < 0.05), and DEQS score (p < 0.01) showed statistically significant improvements. The F-WGA fluorescence intensities (p < 0.0001) significantly increased after treatment, whereas the concentrations of sialic acid and tear proteins remained unchanged.

CONCLUSIONS

Topical application of diquafosol solution to the SCL wearers with dryness improved biomarker of membrane-associated mucins, BUT, staining of cornea and conjunctiva, and subjective symptoms.

TFOS DEWS II Tear Film Report

The members of the Tear Film Subcommittee reviewed the role of the tear film in dry eye disease (DED). The Subcommittee reviewed biophysical and biochemical aspects of tears and how these change in DED. Clinically, DED is characterized by loss of tear volume, more rapid breakup of the tear film and increased evaporation of tears from the ocular surface. The tear film is composed of many substances including lipids, proteins, mucins and electrolytes. All of these contribute to the integrity of the tear film but exactly how they interact is still an area of active research. Tear film osmolarity increases in DED. Changes to other components such as proteins and mucins can be used as biomarkers for DED. The Subcommittee recommended areas for future research to advance our understanding of the tear film and how this changes with DED. The final report was written after review by all Subcommittee members and the entire TFOS DEWS II membership.

Meibomian Gland Dysfunction and Contact Lens Discomfort

Meibomian glands are located in the eyelids and secrete meibum, which gives rise to the lipid layer of the tear film. Changes to these glands can lead to the development of meibomian gland dysfunction (MGD), which is associated with various ocular symptoms such as fatigue, dryness, burning sensation, and heavy sensation. The diagnosis of MGD thus relies on evaluation of ocular symptoms, meibum condition, and lid margin abnormalities. The recent development of noninvasive meibography and tear interferometry has provided important insight into meibomian gland structure and function, respectively. Wearers of contact lenses complain of ocular symptoms that are thought to be attributable to a variety of causes, such as a diminished aqueous or mucin layer of the tear film, changes in tear protein concentration, and altered meibomian gland structure or function. Many studies have examined the relation between contact lens wear and meibomian gland changes. Such studies have found that lens wear is associated with adverse changes in meibomian gland morphology and in the condition of the lid margin and meibum, suggesting that contact lenses negatively affect meibomian glands. Meibomian gland dysfunction-like changes in meibomian glands induced by contact lens wear may thus be responsible for at least some of the ocular symptoms in lens wearers.