Cornea

McKay TB, Serjersen H, Hjortdal J, Zieske JD, Karamichos D. Characterization of Tear Immunoglobulins in a Small-Cohort of Keratoconus Patients. Sci Rep 2020;10(1):9426.Abstract
Keratoconus (KC) is classically considered a non-inflammatory condition caused by central corneal thinning that leads to astigmatism and reduced visual acuity. Previous studies have identified increased systemic levels of pro-inflammatory factors, including interleukin-6, tumor necrosis factor-α, and matrix metalloproteinase-9, suggesting that KC may have an inflammatory component in at least a subset of patients. In this study, we evaluated the levels of different immunoglobulins (light and heavy chains) based on Ig α, Ig λ, Ig κ, Ig µ, and Ig heavy chain subunits in non-KC tears (n = 7 control individuals) and KC tears (n = 7 KC patients) using tandem-liquid chromatography mass spectrometry. The most abundant Ig heavy chains detected in both control individuals and KC patients were Ig α-1 and Ig α-2 likely correlating to the higher IgA levels reported in human tears. We identified significant differences in immunoglobulin κ-chain V-II levels in KC patients compared to control individuals with no significant difference in Ig κ/Ig λ ratios or heavy chain levels. Our study supports previous findings suggesting that KC possesses a systemic component that may contribute to the KC pathology. Further studies are required to define causality and establish a role for systemic immune system-dependent factors and pro-inflammatory processes in KC development or progression.
Singh RB, Blanco T, Mittal SK, Taketani Y, Chauhan SK, Chen Y, Dana R. Pigment Epithelium-derived Factor secreted by corneal epithelial cells regulates dendritic cell maturation in dry eye disease. Ocul Surf 2020;18(3):460-469.Abstract
PURPOSE: In this study, we quantify Pigment Epithelium-derived Factor (PEDF) secreted by corneal epithelial cells and evaluate its immunomodulatory functions in a murine model of dry eye disease (DED). METHODS: We induced DED in female C57BL/6 mice using a controlled environment chamber for 14 days. We quantified mRNA expression of Serpinf1 gene and PEDF protein synthesis by corneal epithelial cells (CEpCs) using RT-PCR and ELISA. CEpCs from normal or DED mice were cultured with IFNγ-stimulated-dendritic cells (DCs) for 24 h, and expression of MHC-II and CD86 by DCs was determined using flow cytometry. Next, we either added recombinant PEDF (rPEDF) or anti-PEDF antibody to co-culture, and DC expression of the above maturation markers was quantified. Lastly, we treated DED mice with either topical rPEDF, anti-PEDF Ab or murine serum albumin (MSA), and DC maturation, expression of pro-inflammatory cytokines, and DED severity were investigated. RESULTS: Serpinf1 mRNA expression and PEDF protein production levels by CEpCs were upregulated in DED. CEpCs from DED mice exhibited an enhanced suppressive effect on the expression of MHC-II and CD86 by DCs, compared to normal mice. This effect was abolished by blocking endogenous PEDF with anti-PEDF Ab or enhanced by supplementing with rPEDF. Treatment with anti-PEDF antibody blocked the effect of endogenous-PEDF and increased DC maturation, expression of pro-inflammatory cytokines in conjunctivae, and exacerbated disease severity in DED mice. Conversely, topical rPEDF enhanced the suppressive effect of endogenous PEDF on DC maturation, decreased expression of pro-inflammatory cytokines in conjunctivae, and reduced disease severity. CONCLUSIONS: The results from our study elucidate the role of PEDF in impeding DC maturation, and suppression of ocular surface inflammation, explicating a promising therapeutic potential of PEDF in limiting the corneal epitheliopathy as a consequence of DED.
Yang J, LeBlanc ME, Cano I, Saez-Torres KL, Saint-Geniez M, Ng Y-S, D'Amore PA. ADAM10 and ADAM17 proteases mediate proinflammatory cytokine-induced and constitutive cleavage of endomucin from the endothelial surface. J Biol Chem 2020;295(19):6641-6651.Abstract
Contact between inflammatory cells and endothelial cells (ECs) is a crucial step in vascular inflammation. Recently, we demonstrated that the cell-surface level of endomucin (EMCN), a heavily -glycosylated single-transmembrane sialomucin, interferes with the interactions between inflammatory cells and ECs. We have also shown that, in response to an inflammatory stimulus, EMCN is cleared from the cell surface by an unknown mechanism. In this study, using adenovirus-mediated overexpression of a tagged EMCN in human umbilical vein ECs, we found that treatment with tumor necrosis factor α (TNF-α) or the strong oxidant pervanadate leads to loss of cell-surface EMCN and increases the levels of the C-terminal fragment of EMCN 3- to 4-fold. Furthermore, treatment with the broad-spectrum matrix metalloproteinase inhibitor batimastat (BB94) or inhibition of ADAM metallopeptidase domain 10 (ADAM10) and ADAM17 with two small-molecule inhibitors, GW280264X and GI254023X, or with siRNA significantly reduced basal and TNFα-induced cell-surface EMCN cleavage. Release of the C-terminal fragment of EMCN by TNF-α treatment was blocked by chemical inhibition of ADAM10 alone or in combination with ADAM17. These results indicate that cell-surface EMCN undergoes constitutive cleavage and that TNF-α treatment dramatically increases this cleavage, which is mediated predominantly by ADAM10 and ADAM17. As endothelial cell-surface EMCN attenuates leukocyte-EC interactions during inflammation, we propose that EMCN is a potential therapeutic target to manage vascular inflammation.
Hall LN, Shanbhag SS, Rashad R, Chodosh J, Saeed HN. The effects of systemic cyclosporine in acute Stevens-Johnson syndrome/toxic epidermal necrolysis on ocular disease. Ocul Surf 2020;Abstract
PURPOSE: To evaluate the effect of systemic cyclosporine (CsA) on ocular disease in Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) patients. METHODS: In this retrospective, comparative cohort study at a single center, patients with a diagnosis of SJS/TEN and with at least 3 months of follow up were divided into two groups: those who received systemic CsA and those who did not receive systemic CsA. Best-corrected visual acuity (BCVA) and chronic ocular surface complications score (COCS) at final follow-up were compared between the two groups. RESULTS: The median age and follow-up period of patients was 29 years (range, 1.5-71 years) and 16.8 months (range, 3.67-91.58 months), respectively. BCVA, COCS, meibomian gland dysfunction, limbal stem cell deficiency, and the need for mucous membrane grafting and scleral lenses were not significantly different between patients who received systemic CsA as compared to patients who did not receive systemic CsA. CONCLUSIONS: In this small cohort of patients with SJS/TEN, we could identify no association between the use of systemic CsA as a component of their initial therapy and chronic ocular complications.
Koulouri I, Hellwinkel O, Altenähr S, Spitzer M, Fritz S, Feuerstacke J, Filev F. A new storage solution for the hypothermic preservation of corneal grafts: an experimental study. Cell Tissue Bank 2020;21(3):507-521.Abstract
In this experimental study we used for the first time Tiprotec as a solution for corneal preservation and cold storage. We compared the resultant endothelial cell morphology and viability with this obtained after preservation of the ex-vivo corneas with both usual standard techniques: conventional cold storage (using Eusol-C) and organ culture. This prospective, in vitro, 3-armed parallel study was performed with the use of 90 porcine corneas (examined for their endothelial quality and transparency) randomly selected for preservation in three storage methods (each 30 corneas): organ culture, standard cold storage (Eusol-C) and experimental cold storage (Tiprotec) Endothelium cell quantity and quality as well as corneal opacification were assessed. The degree of endothelial transparency was significantly reduced over time with all preservation media, without any significant difference among the three groups at any point of time. A reduction in endothelial cell density was also observed with all three preservation media after 30 days of storage without statistically significant differences between groups. The number of hexagonal and pentagonal endothelium cells was significantly reduced overtime in all media with significantly more hexagonal and pentagonal in the organ culture group compared to the cold storage groups. We could show that the cryopreservation medium Tiprotec, used until now for the preservation of vascular grafts, was of similar quality compared to the medium Eusol-C for the hypothermic storage of corneal tissue for an extended period of time up to 30 days. In comparison to organic culture with culture medium KII, both Tiprotec and Eusol-C were found less effective in preserving endothelial cell quality, as assessed by the morphometric analysis, and viability, as assessed by the degree of vacuolization at least up to the 30th day of storage. However, both, Tiprotec- and Eusol-C-preserved corneas demonstrated a certain capacity to recover after their submission in organ culture.
Han X, Yang S, Kam WR, Sullivan DA, Liu Y. The Carbonic Anhydrase Inhibitor Dorzolamide Stimulates the Differentiation of Human Meibomian Gland Epithelial Cells. Curr Eye Res 2020;45(12):1604-1610.Abstract
PURPOSE: Clinical studies have indicated that the long-term use of topical antiglaucoma drugs, such as carbonic anhydrase inhibitors (CAIs), may lead to meibomian gland dysfunction (MGD). We hypothesize that these adverse effects involve a direct influence on human MG epithelial cells (HMGECs). The purpose our present investigation was to test our hypothesis and determine whether exposure to dorzolamide, a CAI, impacts the proliferation, intracellular signaling and differentiation of HMGECs. MATERIALS AND METHODS: We cultured immortalized (i) HMGECs with vehicle or various concentrations of dorzolamide for 6 days. Cells were enumerated with a hemocytometer, and examined for their morphology, Akt signaling activity, accumulation of neutral lipids, phospholipids and lysosomes, and the expression of protein biomarkers for lipogenesis regulation, lysosomes and autophagosomes. RESULTS: Our results show that a high, 500 µg/ml concentration of dorzolamide causes a significant decrease in Akt signaling and the proliferation of iHMGECs. However, the high dose of dorzolamide also promotes the differentiation of iHMGECs. This response features increases in the number of lysosomes, the accumulation of phospholipids, and the expression of the light chain 3A biomarker for autophagosomes. In contrast, the therapeutic amount (50 µg/ml) of dorzolamide has no impact on the proliferative or differentiative abilities of iHMGECs. CONCLUSIONS: Our results support our hypothesis and demonstrate that the CAI dorzolamide does exert a direct influence on the proliferation and differentiation of iHMGECs. However, this effect is elicited only by a high, and not a therapeutic, amount of dorzolamide. AKT: phosphoinositide 3-kinase-protein kinase B; BPE: bovine pituitary extract; CAD: cationic amphiphilic drug; DED: dry eye disease; DMEM/F12: 1:1 mixture of Dulbecco's modified Eagle's medium and Ham's F-12; EGF: epidermal growth factor; FBS: fetal bovine serum; iHMGECs: immortalized human meibomian gland epithelial cells; KSFM: keratinocyte serum-free medium; LAMP-1: lysosomal-associated membrane protein 1; LC3A: light chain 3A; MGD: meibomian gland dysfunction; SREBP-1: sterol regulatory element-binding protein 1.
Wang J, Liu Y, Kam WR, Li Y, Sullivan DA. Toxicity of the cosmetic preservatives parabens, phenoxyethanol and chlorphenesin on human meibomian gland epithelial cells. Exp Eye Res 2020;196:108057.Abstract
Recently, we discovered that the cosmetic preservatives, benzalkonium chloride and formaldehyde, are especially toxic to human meibomian gland epithelial cells (HMGECs). Exposure to these agents, at concentrations approved for human use, leads within hours to cellular atrophy and death. We hypothesize that these effects are not unique, and that other cosmetic preservatives also exert adverse effects on HMGECs. Such compounds include parabens, phenoxyethanol and chlorphenesin, which have been reported to be toxic to corneal and conjunctival epithelial cells, the liver and kidney, as well as to irritate the eye. To test our hypothesis, we examined the influence of parabens, phenoxyethanol and chlorphenesin on the morphology, signaling, survival, proliferation and lipid expression of immortalized (I) HMGECs. These cells were cultured under proliferating or differentiating conditions with varying concentrations of methylparaben, ethylparaben, phenoxyethanol and chlorphenesin for up to 5 days. We monitored the signaling ability, appearance, number and neutral lipid content of the IHMGECs, as well as their lysosome accumulation. Our findings show that a 30-min exposure of IHMGECs to these preservatives results in a significant reduction in the activity of the Akt pathway. This effect is dose-dependent and occurs at concentrations equal to (chlorphenesin) and less than (all others) those dosages approved for human use. Further, a 24-h treatment of the IHMGECs with concentrations of methylparaben, ethylparaben, phenoxyethanol and chlorphenesin close to, or at, the approved human dose induces cellular atrophy and death. At all concentrations tested, no preservative stimulated IHMGEC proliferation. Of particular interest, it was not possible to evaluate the influence of these preservatives, at close to human approved dosages, on IHMGEC differentiation, because the cells did not survive the treatment. In summary, our results support our hypothesis and show that methylparaben, ethylparaben, phenoxyethanol and chlorphenesin are toxic to IHMGECs.
Fan N-W, Dohlman TH, Foulsham W, McSoley M, Singh RB, Chen Y, Dana R. The role of Th17 immunity in chronic ocular surface disorders. Ocul Surf 2020;Abstract
Th17 cells have been implicated in the pathogenesis of numerous inflammatory and autoimmune conditions. At the ocular surface, Th17 cells have been identified as key effector cells in chronic ocular surface disease. Evidence from murine studies indicates that following differentiation and expansion, Th17 cells migrate from the lymphoid tissues to the eye, where they release inflammatory cytokines including, but not limited to, their hallmark cytokine IL-17A. As the acute phase subsides, a population of long-lived memory Th17 cells persist, which predispose hosts both to chronic inflammation and severe exacerbations of disease; of great interest is the small subset of Th17/1 cells that secrete both IL-17A and IFN-γ in acute-on-chronic disease exacerbation. Over the past decade, substantial progress has been made in deciphering how Th17 cells interact with the immune and neuroimmune pathways that mediate chronic ocular surface disease. Here, we review (i) the evidence for Th17 immunity in chronic ocular surface disease, (ii) regulatory mechanisms that constrain the Th17 immune response, and (iii) novel therapeutic strategies targeting Th17 cells.
Chen D, Liu Y, Shu G, Chen C, Sullivan DA, Kam WR, Hann S, Fowler M, Warman ML. Ocular Manifestations of Chordin-like 1 Knockout Mice. Cornea 2020;39(9):1145-1150.Abstract
PURPOSE: In humans, loss-of-function mutations in the gene encoding Chordin-like 1 (CHRDL1) cause X-linked megalocornea (MGC1), characterized by bilateral corneal enlargement, decreased corneal thickness, and increased anterior chamber depth (ACD). We sought to determine whether Chrdl1 knockout (KO) mice would recapitulate the ocular findings found in patients with MGC1. METHODS: We generated mice with a Chrdl1 KO allele and confirmed that male Chrdl1 hemizygous KO mice do not express Chrdl1 mRNA. We examined the eyes of male mice that were hemizygous for either the wild-type (WT) or KO allele and measured corneal diameter, corneal area, corneal thickness, endothelial cell density, ACD, tear volume, and intraocular pressure. We also harvested retinas and counted retinal ganglion cell numbers. Eye segregation pattern in the dorsal lateral geniculate nucleus were also compared between male Chrdl1 KO and WT mice. RESULTS: Male Chrdl1 KO mice do not have larger cornea diameters than WT mice. KO mice have significantly thicker central corneas (116.5 ± 3.9 vs. 100.9 ± 4.2 μm, P = 0.013) and smaller ACD (325.7 ± 5.7 vs. 405.6 ± 6.3 μm, P < 0.001) than WT mice, which is the converse of what occurs in patients who lack CHRDL1. Retinal-thalamic projections and other ocular measurements did not significantly differ between KO and WT mice. CONCLUSIONS: Male Chrdl1 KO mice do not have the same anterior chamber abnormalities seen in humans with CHRDL1 mutations. Therefore, Chrdl1 KO mice do not recapitulate the human MGC1 phenotype. Nevertheless, Chrdl1 plays a role during mouse ocular development because corneas in KO mice differ from those in WT mice.
Lu X, Kugadas A, Smith-Page K, Lamb J, Lin T, Ru Y, Morley SC, Fichorova R, Mittal SK, Chauhan SK, Littleton S, Saban D, Gadjeva M. Neutrophil L-Plastin Controls Ocular Paucibacteriality and Susceptibility to Keratitis. Front Immunol 2020;11:547.Abstract
Why ocular mucosa is paucibacterial is unknown. Many different mechanisms have been suggested but the comprehensive experimental studies are sparse. We found that a deficiency in L-plastin (LCP1), an actin bundling protein, resulted in an ocular commensal overgrowth, characterized with increased presence of conjunctival spp. The commensal overgrowth correlated with susceptibility to -induced keratitis. L-plastin knock-out (KO) mice displayed elevated bacterial burden in the -infected corneas, altered inflammatory responses, and compromised bactericidal activity. Mice with ablation of LPL under the LysM Cre ( ) and S100A8 Cre ( ) promoters had a similar phenotype to the LPL KOs mice. In contrast, infected mice did not display elevated susceptibility to infection, implicating the myeloid L-plastin-sufficient cells (e.g., macrophages and neutrophils) in maintaining ocular homeostasis. Mechanistically, the elevated commensal burden and the susceptibility to infection were linked to defects in neutrophil frequencies at steady state and during infection and compromised bactericidal activities upon priming. Macrophage exposure to commensal organisms primed neutrophil responses to , augmenting PMN bactericidal capacity in an L-plastin dependent manner. Cumulatively, our data highlight the importance of neutrophils in controlling ocular paucibacteriality, reveal molecular and cellular events involved in the process, and suggest a link between commensal exposure and resistance to infection.
McColgan NM, Feeley MN, Woodward AM, Guindolet D, Argüeso P. The O-GlcNAc modification promotes terminal differentiation of human corneal epithelial cells. Glycobiology 2020;30(11):872-880.Abstract
Dynamic modification of nuclear and cytoplasmic proteins with O-linked β-N-acetylglucosamine (O-GlcNAc) plays an important role in orchestrating the transcriptional activity of eukaryotic cells. Here, we report that the O-GlcNAc modification contributes to maintaining ocular surface epithelial homeostasis by promoting mucin biosynthesis and barrier function. We found that induction of human corneal epithelial cell differentiation stimulated the global transfer of O-GlcNAc to both nuclear and cytosolic proteins. Inflammatory conditions, on the other hand, were associated with a reduction in the expression of O-GlcNAc transferase at the ocular surface epithelia. Loss- and gain-of-function studies using small interfering RNA targeting O-GlcNAc transferase, or Thiamet G, a selective inhibitor of O-GlcNAc hydrolase, respectively, revealed that the presence of O-GlcNAc was necessary to promote glycocalyx barrier function. Moreover, we found that Thiamet G triggered a correlative increase in both surface expression of MUC16 and apical epithelial cell area while reducing paracellular permeability. Collectively, these results identify intracellular protein O-glycosylation as a novel pathway responsible for promoting the terminal differentiation of human corneal epithelial cells.
Inomata T, Iwagami M, Nakamura M, Shiang T, Fujimoto K, Okumura Y, Iwata N, Fujio K, Hiratsuka Y, Hori S, Tsubota K, Dana R, Murakami A. Association between dry eye and depressive symptoms: Large-scale crowdsourced research using the DryEyeRhythm iPhone application. Ocul Surf 2020;18(2):312-319.Abstract
PURPOSE: Dry eye (DE) disease and depression are increasing in modern times. We investigated the association between DE and depressive symptoms using the iPhone application, DryEyeRhythm. METHODS: This large-scale crowdsourced observational study was conducted within iPhone users in Japan who downloaded DryEyeRhythm. Participants with a Zung Self-rating Depression Scale (SDS) score ≥ 40 were defined as having depressive symptoms, and those with an Ocular Surface Disease Index (OSDI) score ≥ 13 were defined as having DE symptoms (mild, 13-22; moderate, 23-32; and severe, 33-100). We compared SDS scores between participants with normal eye and mild, moderate, and severe OSDI-based DE symptoms. Logistic regression analyses were used to determine the association between DE severity and depressive symptoms after adjustment for demographic characteristics, medical history, and lifestyle habits. RESULTS: This study included 4454 participants (mean age, 27.9 ± 12.6 years; female, 66.7%). Participants with SDS scores ≥40 accounted for 58.2%, 70.9%, 79.4%, and 85.0% of normal controls and participants with mild, moderate, and severe DE symptoms, respectively (P trend < 0.001). The adjusted odds ratios (95% confidence interval) for depressive symptoms (SDS score of ≥40) were 1.62 (1.35-1.95) for mild, 2.39 (1.92-2.97) for moderate, and 3.29 (2.70-4.00) for severe DE symptoms. CONCLUSION: This large-scale crowdsourced clinical study using DryEyeRhythm suggests that depressive symptoms are more common in individuals with more severe DE symptoms. DryEyeRhythm could play a role in earlier prevention or future prospective interventions for depressive symptoms in individuals with DE symptoms.
Foulsham W, Mittal SK, Taketani Y, Chen Y, Nakao T, Chauhan SK, Dana R. Aged Mice Exhibit Severe Exacerbations of Dry Eye Disease with an Amplified Memory Th17 Cell Response. Am J Pathol 2020;190(7):1474-1482.Abstract
The prevalence as well as the severity of dry eye disease increase with age. Memory T helper 17 (Th17) cells (CD4IL-17ACD44) drive the chronic and relapsing course of dry eye disease. Here, we investigated the contribution of memory Th17 cells to age-related dry eye disease, and evaluated memory Th17 cell depletion with anti-IL-15 antibody as a strategy to abrogate the severe exacerbations of dry eye disease observed in aged mice. After initial exposure to desiccating stress, aged mice maintained higher frequencies of memory Th17 cells in the draining lymph nodes relative to young mice. Upon secondary exposure to desiccating stress, aged mice developed more severe corneal epitheliopathy than young mice, which is associated with increased local frequencies of Th17 cells (CD4IL-17A). Treatment with anti-IL-15 antibody decreased the enlarged memory Th17 pool in aged mice to frequencies comparable with young mice. Furthermore, anti-IL-15-treated mice showed significantly reduced conjunctival infiltration of Th17 cells and lower corneal fluorescein staining scores compared with saline-treated control mice. Our data suggest that age-related increases in the memory Th17 compartment predispose aged mice toward the development of severe corneal epithelial disease after exposure to a dry environment. Selectively targeting memory Th17 cells may be a viable therapeutic approach in the treatment of age-related dry eye disease.
Hui P-C, Shtyrkova K, Zhou C, Chen X, Chodosh J, Dohlman CH, Paschalis EI. Implantable self-aligning fiber-optic optomechanical devices for in vivo intraocular pressure-sensing in artificial cornea. J Biophotonics 2020;13(7):e202000031.Abstract
Artificial cornea is an effective treatment of corneal blindness. Yet, intraocular pressure (IOP) measurements for glaucoma monitoring remain an urgent unmet need. Here, we present the integration of a fiber-optic Fabry-Perot pressure sensor with an FDA-approved keratoprosthesis for real-time IOP measurements using a novel strategy based on optical-path self-alignment with micromagnets. Additionally, an alternative noncontact sensor-interrogation approach is demonstrated using a bench-top optical coherence tomography system. We show stable pressure readings with low baseline drift (<2.8 mm Hg) for >4.5 years in vitro and efficacy in IOP interrogation in vivo using fiber-optic self-alignment, with good initial agreement with the actual IOP. Subsequently, IOP drift in vivo was due to retroprosthetic membrane (RPM) formation on the sensor secondary to surgical inflammation (more severe in the current pro-fibrotic rabbit model). This study paves the way for clinical adaptation of optical pressure sensors with ocular implants, highlighting the importance of controlling RPM in clinical adaptation.
Tashbayev B, Utheim TP, Utheim ØA, Ræder S, Jensen JL, Yazdani M, Lagali N, Vitelli V, Dartt DA, Chen X. Utility of Tear Osmolarity Measurement in Diagnosis of Dry Eye Disease. Sci Rep 2020;10(1):5542.Abstract
The prevalence of dry eye disease is high worldwide and poses a great burden on patients' daily lives. Accurate diagnosis of the disease is important, and it requires application of various methods. Hyperosmolarity is believed to be the disease marker and thus measuring it provides useful information. In this study we investigated utility of tear osmolarity measured with TearLab osmometer, along with other diagnostic tests (Ocular Surface Disease Index questionnaire, Tear film break-up time, Ocular Protection Index, Ocular Surface Staining, Schirmer I test, Meibomian gland functionality in 757 patients (1514 eyes) with dry eye disease and 29 healthy controls (58 eyes). Statistical differences between the patient group and the control group were observed for all the tests apart from tear osmolarity, regardless of cut-off value (>308 mOsm/L, >316 mOsm/L, and inter-eye difference >8 mOsm/L). Moreover, in the receiver operating characteristics curve analyses tear osmolarity measurement could not discriminate dry eye disease pathological scores. Therefore, our study suggests that tear osmolarity measured with TearLab osmometer cannot be used as a key indicator of DED.

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