Quantitative analysis of lacrimal gland function, apoptotic figures, Fas and Fas ligand expression of lacrimal glands in dry eye patients

Maximal tear secretion evoked by controlled stimulation of corneal sensory nerves in healthy individuals and dry eye subjects

PURPOSE

To measure, the tear flow changes evoked in healthy subjects and dry eye disease (DED) patients by controlled sensory stimulation of the eye surface with i-Onion™, a new stimulation device.

METHODS

Sensory corneal nerves were stimulated with an instrument (i-Onion™) that ejects puffs of CO₂ gas (99.9%) at 200 ml·min^-1 for 3s, delivered 5 mm from the cornea. Using Schirmer test strips, tear volumes were measured over 3 min in the cornea of one eye before (basal tear volume -BTV) and in the other eye after stimulation of the sensory nerves with CO₂ (stimulated tear volume -STV). These measurements were obtained from a control group of adults of either sex (17 students aged 20-30 and 29 subjects without signs of dry eye aged 25-61), a cohort of DED patients (aged 34-75) that included 12 asymptomatic, suspected DED subjects (Schirmer <7 mm and/or TBUT <10s), and 30 Sjögren's syndrome (SS) patients.

RESULTS

CO₂ stimulation significantly increased the tear volume (BTV = 14.6 ± 1.0 mm, STV = 19.0 ± 1.1 mm: n = 46) in 78% of control subjects, reflecting a mean tear reserve volume (TRV = STV-BTV) of 4.4 ± 0.8 mm. Individual differences were wide, and while no increase in reflex tearing was evoked in 30% of subjects with a BTV >10 mm, the remaining 70% responded vigorously to stimulation, even those with a BTV >18 mm. Asymptomatic DED subjects displayed weaker responses to CO₂ stimulation, with lower STVs. Both the BTV and STV of SS patients were low, significantly below those of the healthy controls.

CONCLUSIONS

Measuring the rise in reflex tearing volume evoked by controlled corneal stimulation provides objective information about the tear glands' secretory capacity in health and disease.

Defining Dry Eye from a Clinical Perspective

Over the past decades, the number of patients with dry eye disease (DED) has increased dramatically. The incidence of DED is higher in Asia than in Europe and North America, suggesting the involvement of cultural or racial factors in DED etiology. Although many definitions of DED have been used, discrepancies exist between the various definitions of dry eye disease (DED) used across the globe. This article presents a clinical consensus on the definition of DED, as formulated in four meetings with global DED experts. The proposed new definition is as follows: “Dry eye is a multifactorial disease characterized by a persistently unstable and/or deficient tear film (TF) causing discomfort and/or visual impairment, accompanied by variable degrees of ocular surface epitheliopathy, inflammation and neurosensory abnormalities.” The key criteria for the diagnosis of DED are unstable TF, inflammation, ocular discomfort and visual impairment. This definition also recommends the assessment of ocular surface epitheliopathy and neurosensory abnormalities in each patient with suspected DED. It is easily applicable in clinical practice and should help practitioners diagnose DED consistently. This consensus definition of DED should also help to guide research and clinical trials that, to date, have been hampered by the lack of an established surrogate endpoint.

LFA-1/ICAM-1 Interaction as a Therapeutic Target in Dry Eye Disease

Dry eye disease (DED) is a common ocular disorder associated with inflammation of the lacrimal gland and ocular surface. The interaction of the integrin lymphocyte function-associated antigen-1 (LFA-1) with its cognate ligand intercellular adhesion molecule-1 (ICAM-1) is known to have important roles in the interaction of a variety of cells involved in immune responses and inflammation, including those prominent in ocular surface inflammation. Lifitegrast, an LFA-1 antagonist that blocks binding of ICAM-1 to LFA-1, has recently been approved in the United States for the treatment of signs and symptoms of DED. In this review, we evaluate research findings to explore the potential role of LFA-1/ICAM-1 interaction in the pathophysiology of DED, and the evidence supporting LFA-1/ICAM-1 interaction as a rational therapeutic target in DED. The results of our review suggest that LFA-1/ICAM-1 interaction may play important roles in the cell-mediated immune response and inflammation associated with DED, including facilitating the homing of dendritic cells to the lymph nodes, interaction of dendritic cells with T cells and subsequent T cell activation/differentiation, migration of activated CD4⁺ T cells from the lymph nodes to the ocular surface, reactivation of T cells by resident antigen-presenting cells at the ocular surface, and recruitment and retention of LFA-1-expressing T cells in the conjunctival epithelium. Based on the available evidence, inhibition of LFA-1/ICAM-1 interaction represents a rational targeted approach in treating DED. Notably, inhibition of LFA-1/ICAM-1 binding with lifitegrast offers a novel approach to reducing ocular surface inflammation in this condition.

Air exposure induced characteristics of dry eye in conjunctival tissue culture

There are several animal models illustrating dry eye pathophysiology. Current study would like to establish an ex vivo tissue culture model for characterizing dry eye. Human conjunctival explants were cultured under airlift or submerged conditions for up to 2 weeks, and only airlifted conjunctival cultures underwent increased epithelial stratification. Starting on day 4, the suprabasal cells displayed decreased K19 expression whereas K10 keratin became evident in airlift group. Pax6 nuclear expression attenuated already at 2 days, while its perinuclear and cytoplasmic expression gradually increased. MUC5AC and MUC19 expression dramatically decreased whereas the full thickness MUC4 and MUC16 expression pattern disappeared soon after initiating the airlift condition. Real time PCR showed K16, K10 and MUC16 gene up-regulated while K19, MUC5AC, MUC19 and MUC4 down-regulated on day 8 and day 14. On day 2 was the appearance of apoptotic epithelial and stromal cells appeared. The Wnt signaling pathway was transiently activated from day 2 to day 10. The inflammatory mediators IL-1β, TNF-α, and MMP-9 were detected in the conditioned media after 6 to 8 days. In conclusion, airlifted conjunctival tissue cultures demonstrated Wnt signaling pathway activation, coupled with squamous metaplasia, mucin pattern alteration, apoptosis and upregulation of proinflammatory cytokine expression. These changes mimic the pathohistological alterations described in dry eye. This correspondence suggests that insight into the pathophysiology of dry eye may be aided through the use of airlifted conjunctival tissue cultures.

Type I IFN signature in primary Sjögren's syndrome patients

Primary Sjögren's syndrome (pSS) is a systemic autoimmune disease characterized by lymphocytic infiltrates in salivary and lacrimal glands. Clinical manifestations range from ocular and oral dryness to vasculitis and severe fatigue. pSS is a disease with heterogeneous symptoms and a variable response to the available treatment. Recently, a key role for Interferon (IFN) type I has been implicated in the pathogenesis of pSS. As type I IFN consists of 17 different subtypes, it cannot be easily assessed using a conventional ELISA. Therefore the expression of type I IFN inducible genes--the so-called type I IFN signature--is assessed in salivary gland tissue and blood from patients as a readout for type I IFN activity. In this review we discuss the potential of type I IFN as a novel biomarker for disease activity, subclassification of patients, prediction of therapy response and most importantly as a target for therapeutic intervention.

Role of epithelial-mesenchymal transition in repair of the lacrimal gland after experimentally induced injury

PURPOSE

Ongoing studies demonstrate that the murine lacrimal gland is capable of repair after experimentally induced injury. It was recently reported that repair of the lacrimal gland involved the mobilization of mesenchymal stem cells (MSCs). These cells expressed the type VI intermediate filament protein nestin whose expression was upregulated during the repair phase. The aim of the present study was to investigate the roles of vimentin, a type III intermediate filament protein and a marker of epithelial-mesenchymal transition (EMT) in repair of the lacrimal gland.

METHODS

Injury was induced by direct injection of interleukin (IL)-1 into the exorbital lacrimal gland. MSCs were prepared from injured glands using tissue explants. Expression of vimentin and the transcription factor Snai1, a master regulator of EMT, was determined by RT-PCR, Western blotting analysis, and immunofluorescence.

RESULTS

These data show that vimentin expression, at both the mRNA and the protein levels, was upregulated during the repair phase (2-3 days postinjury) and returned to the control level when repair ended. Temporal expression of Snai1 mirrored that of vimentin and was localized in cell nuclei. Cultured MSCs isolated from injured lacrimal glands expressed Snai1 and vimentin alongside nestin and alpha smooth muscle actin (another biomarker of EMT). There was a strong positive correlation between Snai1 expression and vimentin expression.

CONCLUSIONS

It was found that EMT is induced during repair of the lacrimal gland to generate MSCs to initiate repair, and that mesenchymal-epithelial transition is then activated to form acinar and ductal epithelial cells.

Dry eye disease: an immune-mediated ocular surface disorder

Dry eye disease is a multifactorial disorder of the tears and ocular surface characterized by symptoms of dryness and irritation. Although the pathogenesis of dry eye disease is not fully understood, it is recognized that inflammation has a prominent role in the development and propagation of this debilitating condition. Factors that adversely affect tear film stability and osmolarity can induce ocular surface damage and initiate an inflammatory cascade that generates innate and adaptive immune responses. These immunoinflammatory responses lead to further ocular surface damage and the development of a self-perpetuating inflammatory cycle. Herein, we review the fundamental links between inflammation and dry eye disease and discuss the clinical implications of inflammation in disease management.

Influence of sex hormones and genetic predisposition in Sjögren's syndrome: a new clue to the immunopathogenesis of dry eye disease

Sjögren's syndrome (SS) is a chronic autoimmune disease characterized by lymphocytic infiltration, destruction of lacrimal and salivary glands and the presence of serum autoantibodies. Most women that suffer from SS are post-menopausal however, not all post-menopausal women develop SS, suggesting that other factors, in addition to the decrease in ovarian hormones, are necessary for the development of SS. The purposes of this study were to investigate a) the time course of lymphocytic infiltration and apoptosis in the lacrimal gland after ovariectomy, b) if a predisposed genetic background for SS aggravates the effects of decreasing levels of sex hormones in the lacrimal glands and c) if physiological doses of estrogen or androgen prevent the effects observed after ovariectomy. Six weeks old mice that are genetically predisposed to SS (NOD.B10.H2(b)) and control (C57BL/10) mice were either sham operated, ovariectomized (OVX), OVX + 17β estradiol (E(2)) or OVX + Dihydrotestosterone (DHT). Lacrimal glands were collected at 3, 7, 21 or 30 days after surgery and processed for immunohistochemistry to measure CD4(+), CD8(+) T cells, B220(+) B cells, nuclear DNA degradation and cleaved caspase-3 activity. Quantification of the staining was done by light microscopy and Image Pro Plus software. The results of our study show that lymphocytic infiltration preceded lacrimal gland apoptosis after ovariectomy. Moreover, removal of ovarian sex hormones accelerated these effects in the genetically predisposed animal and these effects were more severe and persistent compared to control animals. In addition, sex hormone replacement at physiological levels prevented these symptoms. The mechanisms by which decreased levels of sex hormones caused lymphocytic infiltration and apoptosis and the interaction of lack of sex hormones with the genetic elements remain to be elucidated.

Autoantibody and biopsy grading are associated with expression of ICAM-1, MMP-3, and TRAIL in salivary gland mononuclear cells of Chinese patients with Sjogren's syndrome

OBJECTIVE

Sjögren's syndrome (SS) is an inflammatory autoimmune disease. We investigated important factors associated with the expression of inflammation-related molecules in minor salivary gland (MSG) mononuclear cells in patients with SS.

METHODS

Thirty-four patients with SS with a MSG biopsy grading of either grade III (10 patients) or grade IV (24 patients) were enrolled. The age, sex, autoantibodies, cell infiltration, and intercellular adhesion molecule-1 (ICAM-1), matrix metalloproteinase-3 (MMP-3), tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), or CXCR3 expression were also analyzed.

RESULTS

Ten of the 34 patients with SS were diagnosed with secondary SS; in these patients, the diagnosis of rheumatoid arthritis was confirmed in 8 and systemic lupus erythematosus in 2. TRAIL and ICAM-1 were overexpressed in patients with antinuclear antibodies (ANA) > 1:160, compared to those with titer < 1:160 (45.1 +/- 4.4 vs 41.2 +/- 3.9, p = 0.021, and 15.2 +/- 5.7 vs 10.8 +/- 3.3, p = 0.018, respectively). Higher erythrocyte sedimentation rate (ESR; >OR= 20) was associated with higher TRAIL expression and CD20 cell infiltration in contrast to lower ESR (< 20; p < 0.05). ICAM-1, TRAIL, and MMP-3 were expressed more predominantly in anti-SSA-positive than in anti-SSA-negative patients with SS. There was a significant difference in CD20 cell infiltration and MMP-3 expression between primary SS and secondary SS. Biopsy of a grade IV showed a significantly increased expression of TRAIL (44.9 +/- 4.5 vs 40.8 +/- 3.6, p = 0.013) and MMP-3 (62.7 +/- 6.3 vs 54.4 +/- 7.3, p = 0.003) in mononuclear cells as compared to those of grade III.

CONCLUSION

In our study, pathologic grading with a higher grade (grade IV) and the presence of SSA or a higher titer of ANA were significantly associated with the overexpression of TRAIL, MMP-3, or ICAM-1 in the salivary gland mononuclear cells in patients with SS.

Amplifying factors in ocular surface diseases: apoptosis

Apoptosis is a major cell death mechanism that occurs widely in normal tissues and is overstimulated in ocular surface diseases. Apoptosis has been studied specifically in regard to refractive surgery, contact lens wear, and dry eye syndrome. It appears to be closely related to inflammation, as many inflammatory cytokines may promote both inflammation and apoptosis, and their receptors trigger both pathways. A major mediator would play a key role in ocular surface diseases, both at the pro-apoptotic and pro-inflammatory levels, e.g., tumor necrosis factor alpha. This cytokine and its main receptors are, therefore, overexpressed in ocular surface diseases, which makes it a possible target for future therapeutic approaches.

Research in Dry Eye: Report of the Research Subcommittee of the International Dry Eye WorkShop (2007)

Members of the DEWS Research Subcommittee reviewed research into the basic mechanisms underlying dry eye disease. Evidence was evaluated concerning the tear film, lacrimal gland and accessory lacrimal glands, ocular surface epithelia (including cornea and conjunctiva), meibomian glands, lacrimal duct system and the immune system. Consideration was given to both animal and human research data. Results are presented as a series of information matrices, identifying what is known and providing supporting references. An attempt is made to identify areas for further investigation.

Sjögren's syndrome: why autoimmune epithelitis?

The expression 'autoimmune epithelitis' has been proposed as an alternative for Sjögren's syndrome (SS) based on data pointing out the central role of the epithelial cell in the pathogenesis of the syndrome. Clinically, apart from exocrine glands that are the main target, the epithelial component of the other organs such as kidneys, liver, lungs or thyroid is commonly affected resulting in various extraglandular manifestations. On the other hand, at the molecular and cellular level, the epithelial cell plays a major role in the initiation and perpetuation of the autoimmune lesion. Mechanisms such as antigen presentation, apoptosis, chemokine production or germinal center formation lie in the center of SS pathogenesis and the epithelial cell has a very important role. Herein, we present both aspects, review the data that support the proposed terminology and finally, suggest a unifying theory for the pathogenesis of SS.

Loss of parasympathetic innervation leads to sustained expression of pro-inflammatory genes in the rat lacrimal gland

It has been shown that removal of parasympathetic innervation to the lacrimal gland (LG) leads to rapid reduction in tear flow. Additionally, removal of the neural input resulted in disorganization of LG structure and changes in the expression of genes associated with the secretory pathway and inflammation. The goal of this study was to investigate the change in pro-inflammatory and pro-apoptotic gene expression in the rat LG following parasympathetic denervation. Male Long-Evans rats underwent unilateral sectioning of the greater superficial petrosal nerve and were sacrificed 7 days or 2.5 months later. cDNA was synthesized from LG RNA from the contralateral control (Ctla) and parasympathectomized (Px) glands and comparative real-time PCR was performed. Mean threshold cycles (MC(T)) for the Ctla and Px LG genes were normalized to 18S rRNA MC(T) values, and the relative fold change was calculated for each gene using the 2(-DeltaDeltaC)(T) method. The expression of nuclear factor kappa B1, caspase 1, eotaxin, leukocyte antigen MRC-OX44, allograft inflammatory factor-1, MHC class II molecules RT.1B and RT.1D, IgG receptor FcRn, and macrophage metalloelastase was increased and remained elevated in the Px LG, compared with the Ctla LG. Increased expression of the initiator of apoptosis gene, caspase 2, was confirmed, but expression of the executor gene, caspase 6, was not elevated in the Px LG. Reduced expression of genes associated with post-translational protein processing-furin convertase, protein disulfide isomerase, and UDP-gal transporter isozyme 1-was noted in the Px LG. No significant changes in the expression of genes associated with lysosomal and non-lysosomal-mediated protein degradation were found. Removal of parasympathetic input may lead to decreased capacity for protein synthesis and elevated immune responses in the Px LG. These changes occur without increases in expression of the muscarinic acetylcholine receptor subtype 3, and may suggest the early changes in LG acinar cells and the pathophysiology of autoimmune responses.

Effect of inflammation on lacrimal gland function

The lacrimal gland is the main contributor to the aqueous layer of the tear film. It secretes proteins, electrolytes and water, which helps to nourish and protect the ocular surface. Lacrimal gland secretion is primarily under neural control, which is achieved through a neural reflex arc. Stimuli to the ocular surface activate afferent sensory nerves in the cornea and conjunctiva. This in turn activates efferent parasympathetic and sympathetic nerves in the lacrimal gland to stimulate secretion. Sex steroid hormones are also important regulators of lacrimal gland functions. A decrease or lack of lacrimal gland secretion is the leading cause of aqueous tear deficient dry eye syndrome (DES). It has been suggested that DES is an inflammatory disorder that affects the ocular surface and the lacrimal gland. In several pathological instances, the lacrimal gland can become a target of the immune system and show signs of inflammation. This can result from autoimmune diseases (Sjögren's syndrome), organ transplantation (graft versus host disease), or simply as a result of aging. The hallmarks of lacrimal gland inflammation are the presence of focal lymphocytic infiltrates and increased production of proinflammatory cytokines. The mechanisms leading to lacrimal gland dysfunction are still poorly understood. Apoptosis, production of autoantibodies, hormonal imbalance, alterations in signaling molecules, neural dysfunction, and increased levels of proinflammatory cytokines have been proposed as possible mediators of lacrimal gland insufficiency in disease states.

Diffusion-weighted MR microimaging of the lacrimal glands in patients with Sjogren's syndrome

OBJECTIVE

The purpose of this study was to detect quantitative diffusion-weighted abnormalities in the lacrimal glands of patients with Sjogren's syndrome.

MATERIALS AND METHODS

Diffusion-weighted MRI was performed on 31 healthy volunteers and 11 Sjogren's syndrome patients with impaired lacrimal function. The volunteers and patients underwent MRI with a single-shot spin-echo echo-planar technique using a 47-mm microscopy coil. The apparent diffusion coefficient (ADC) of the lacrimal and parotid glands was obtained with b factors of 500 and 1,000 sec/mm(2). T1-weighted and fat-suppressed T2-weighted MR microscopic images were also obtained to evaluate the gland morphology and signals.

RESULTS

MR microscopy provided high-resolution images of the lacrimal glands that enabled ADC measurements. The ADCs of the normal lacrimal glands showed no significant sex- or age-related changes. The ADCs for the lacrimal glands were significantly higher than those of the parotid glands in the same subjects (mean +/- SD, 891 +/- 103 vs 703 +/- 84 x 10(-6) mm(2)/sec, respectively; p < 0.0001, Mann-Whitney U test). We found that ADCs of the lacrimal glands in Sjogren's syndrome patients were significantly lower than those from the normal glands of age-matched healthy volunteers (736 +/- 34 vs 923 +/- 84 x 10(-6) mm(2)/sec; p < 0.0001, Mann-Whitney U test).

CONCLUSION

These findings suggest that the measurement of ADCs may be a useful tool to assess abnormalities of the lacrimal glands in patients with Sjogren's syndrome.

ICAM-1 expression predisposes ocular tissues to immune-based inflammation in dry eye patients and Sjögrens syndrome-like MRL/lpr mice

PURPOSE

We previously reported that immune-based inflammation occurs on the ocular surface of humans as well as canines with keratoconjunctivitis sicca (KCS). Intercellular adhesion molecule-1 (ICAM-1) was found to be upregulated on lymphocytes and/or vascular endothelial cells resulting in lymphocytic diapedesis to the lacrimal and conjunctival tissues. The purpose of the current study was to demonstrate the role of ICAM-1 in (1) resident epithelial cell response during ocular inflammation, (2) local and/or peripheral lymphocyte activation or accumulation in the ocular tissues, and (3) whether anti-ICAM-1 is effective to attenuate immune-mediated ocular inflammation.

METHODS

ICAM-1 levels in various ocular tissues of human with KCS and/or MRL/lpr mouse were evaluated by immunohistochemistry and in situ hybridization for protein and messenger RNA (mRNA) expression, respectively. Soluble ICAM-1 concentrations in MRL/lpr mouse plasma over the course of disease development were measured by ELISA. Cell proliferation within ocular tissues was assessed by bromodeoxyuridine (BrdU) incorporation and immunohistochemical detection. The level of T cell activation was determined by IL-2 receptor (CD25, a marker of T cell activation and proliferation) and CD69 (a marker of T cell activation) immunoreactivity using FACS analysis. To examine the effectiveness of anti-ICAM-1/LFA-1 in elimination of lacrimal gland inflammation, MRL/lpr mice were injected intraperitoneally (i.p.) with or without monoclonal antibodies against ICAM-1 and LFA-1 at three or eight weeks of age.

RESULTS

Increased endogenous ICAM-1 expression at the level of protein and mRNA was detected in the epithelial cells present in the conjunctival and accessory lacrimal tissues in dry eye patients. In MRL/lpr mice, ICAM-1 expression by lacrimal acinar epithelial cells and conjunctival epithelial cells were detected in addition to inflammatory infiltrates and vascular endothelial cells at 16 weeks of age. Soluble ICAM-1 levels were markedly increased concomitantly with disease progression over time as compared with the controls. No significant lymphocytic proliferation (a lack of BrdU and CD25 immunoreactivities) was detected within lacrimal glands of MRL/lpr mice at the disease onset. However, a population of the infiltrated T cells were CD69 positive, indicating the activation stage of a T cell subset. Treatment using monoclonal antibodies against murine ICAM-1 and LFA-1 resulted in a decrease in the number of inflammatory infiltrates in MRL/lpr mice.

CONCLUSIONS

Our findings suggest that ICAM-1 upregulation locally and systemically promote lymphocyte activation and migration to the ocular surface (OS). Ocular resident epithelium is an active component of ocular surface and is capable of interacting with invasive lymphocytes by ICAM-1 production in response to immune activation and inflammation. ICAM-1 synthesized by epithelial cells may serve as a signaling molecule for predisposition of ocular surface inflammation and facilitate potential antigen presentation by epithelial cells. Lymphocytic infiltrates in the lacrimal gland of the MRL/lpr mouse appeared to be the result of the accumulation, but not proliferation of circulating lymphocytes diapodesed from the vasculature that had migrated into the local ocular tissues. The potential use of anti-ICAM-1 therapy in treating immune-based inflammatory diseases such as dry eye deserves further investigation.

The role of the lacrimal functional unit in the pathophysiology of dry eye

The majority of dry eye symptoms are due to a chronic inflammation of the lacrimal functional unit resulting in a loss of tear film integrity and normal function. This leads to a reduction in the ability of the ocular surface to respond to environmental challenges. The underlying cause of tear film dysfunction is the alteration of tear aqueous, mucin, and lipid components. This may result from a systemic autoimmune disease or a local autoimmune event. A lack of systemic androgen support to the lacrimal gland has been shown to be a facilitative factor in the initiation of this type of pathophysiology. Tear secretion is controlled by the lacrimal functional unit consisting of the ocular surface (cornea, conjunctiva, accessory lacrimal glands, and meibomian glands), the main lacrimal gland and the interconnecting innervation. If any portion of this functional unit is compromised, lacrimal gland support to the ocular surface is impeded. Factors such as neurogenic inflammation and T cell involvement in the disease pathogenesis as well as newly developed animal models of ocular surface inflammation are discussed.

New Insights into the Diagnosis and Treatment of Dry Eye

Over the past decade, numerous advances have been made in relation to dry eye diagnostic markers, technologies, and treatment options. The mainstay of treatment of dry eye is the use of artificial tear solutions and punctum plugs. A goal is the development of agents that provide symptomatic treatment and, at the same time, improve ocular surface keratinization. It is the authors' opinion that the functional visual acuity tester and the new tear stability analysis system will be widely used to improve diagnosis and evaluate treatment outcomes in KCS. Advances in treatment will utilize anti-inflammatory agents, immune suppressants such as Cyclosporin A and FK-506, growth hormones, androgens, topical mucins and ocular surface stimulating drugs, like INS365. Although aqueous-deficient dry eye is most commonly not associated with Sjogren syndrome (SS), aqueous-deficient dry eye is often most severe in patients with SS; thus, this article focuses mainly on SS-associated dry eye.