Tear Film Components Research Articles

In vitro Assay to Examine the Function of Tears on Corneal Epithelial Cells.

Tears contain numerous secreted factors, enzymes, and proteins that help in maintaining the homeostatic condition of the eye and also protect it from the external environment. However, alterations to these enzymes and/or proteins during pathologies such as mechanical injury and viral or fungal infections can disrupt the normal ocular homeostasis, further contributing to disease development. Several tear film components have a significant role in curbing disease progression and promoting corneal regeneration. Additionally, several factors related to disease progression are secreted into the tear film, thereby serving as a valuable reservoir of biomarkers. Tears are readily available and can be collected via non-invasive techniques or simply from contact lenses. Tears can thus serve as a valuable and easy source for studying disease-specific biomarkers. Significant advancements have been made in recent years in the field of tear film proteomics, lipidomics, and transcriptomics to allow a better understanding of how tears can be utilized to gain insight into the etiology of diseases. These advancements have enabled us to study the pathophysiology of various disease states using tear samples. However, the mechanisms by which tears help to maintain corneal homeostasis and how they are able to form the first line of defense against pathogens remain poorly understood and warrant detailed in vitro studies. Herein, we have developed an in vitro assay to characterize the functional importance of patient isolated tears and their components on corneal epithelial cells. This novel approach closely mimics real physiological conditions and could help the researchers gain insight into the underlying mechanisms of ocular pathologies and develop new treatments. Key features • This method provides a new technique for analyzing the effect of tear components on human corneal epithelial cells. • The components of the tears that are altered in response to diseases can be used as a biomarker for detecting ocular complications. • This procedure can be further employed as an in vitro model for assessing the efficacy of drugs and discover potential therapeutic interventions.

Avaliação da porção aquosa da lágrima em Shih-Tzu: comparação do teste lacrimal de Schirmer 1 com a altura do menisco lacrimal

ABSTRACT The aqueous portion of the tear film has been characterized as an essential structure for ocular surface health. Among various assessment tests, some measure the aqueous portion, such as Schirmer Tear Test 1, Meniscometry using a strip, and the test to determine Tear Meniscus Height (TMH). Conversely, few studies have specifically evaluated tear meniscus height, especially those utilizing ocular surface analyzers. Therefore, the aim of this study was to comparatively evaluate the results obtained from employing Tear Meniscus Height (TMH) using an Ocular Surface Analyzer and Schirmer Tear Test 1 (STT-1) in Shih Tzu dogs. To achieve this, the eyes of 18 brachycephalic Shih Tzu dogs of both sexes and varying ages were assessed and compared. The results revealed that the TMH for the right eye was 0.59±0.29mm, and for the left eye was 0.88±0.27mm; p=0.0135. For STT-1, it was found that the right eye had a value of 19.06±4.87mm/min, and the left eye had a value of 23.11±4.80mm/min; p=0.0238. Furthermore, the Pearson correlation test applied between TMH and STT-1 yielded the following results for the right eye (r=0.601; p=0.008) and the left eye (r=-0.032; p=0.8979). The TMH shows potential as an alternative to STT-1 for evaluating the aqueous component of tear film in a similar manner. However, further research is warranted, particularly for establishing reference values for TMH and conducting a comprehensive comparison between STT-1 and TMH. This research is especially important for gathering information that can contribute to the understanding of ophthalmic and systemic conditions that directly influence the physiological composition of tears. Critical for establishing the values obtained when measuring the canine lacrimal meniscus using different techniques is the consideration of associated functional factors.

Canine distichiasis cryoepilation using a liquid nitrogen‐cooled, closed probe transconjunctival triple‐freeze technique: Outcomes in 125 dogs (234 eyes)

AbstractPurposeTo describe a simple cryosurgical technique for treating canine distichiasis, its success rate and any associated complications.MethodsClinical records from canine patients undergoing treatment for distichiasis using a specific cryotherapy technique were retrospectively reviewed. The technique employed a triple freeze–thaw cycle via a transconjunctivally applied, liquid nitrogen‐cooled, 2‐mm diameter closed cryoprobe.ResultsThe cryotherapy technique was employed in 125 dogs with distichiasis over a period of 13 years, with 109 (87%) bilaterally and 16 (13%) unilaterally affected, totaling 234 eyes. The mean age at diagnosis was 1.9 years (4 months to 7.5 years), with Staffordshire bull terriers the most common breed (31%). Treatment was deemed successful if clinical signs related to distichiasis resolved, including blepharospasm, conjunctival hyperemia and excess lacrimation. A single triple‐freeze cryotherapy treatment eliminated distichiae in 195/234 (83%) eyes at a mean follow‐up of 4 months (2 weeks to 10 years). Minor recurrence of distichiae in previously treated regions was observed in 39/234 (17%) eyes. Repeat cryotherapy was required in 25/234 (11%) eyes, with the remaining eyes asymptomatic. The two most common postoperative complications were mild to moderate eyelid swelling in all eyes immediately following surgery and eyelid margin depigmentation in 59/234 eyes (25%) between two and 4 weeks postoperatively, both of which were temporary.ConclusionThis cryotherapy technique for treating canine distichiasis is relatively simple and safe to perform, has a high success rate and a low recorded complication rate, but would benefit from further assessment of any potential detrimental effects on qualitative tear film components.

Long-term effects of tear film component deposition on the surface and optical properties of two different orthokeratology lenses

PurposeTo understand the effects of long-term deposition of tear film components on the surface and optical properties of orthokeratology (ortho-k) lenses, two different lenses, Brighten 22 and Optimum Extra, were tested here. MethodsOrtho-k lenses were immersed in artificial tears and cleaned with a commercial care solution repeatedly for up to 90 days. Both the daily and accumulated lysozyme deposition amounts using an Enzyme-Linked ImmunoSorbent Assay were then analyzed. The base curve, central thickness, power, and transmission of visible light, ultraviolet A, and ultraviolet B were analyzed before and after repeated tear film component deposition procedures. The surface roughness using atomic force microscopy was observed and an energy dispersive spectrometer was used to analyze the composition of the deposits. ResultsThe highest levels of lysozyme were adsorbed on both lens materials during the first four days of the procedure and became saturated by day 6. For both lens materials, contamination on the lenses was easily observed by day 30, and the degree of surface roughness was higher. The transmission levels of different light spectrums were reduced showing that the optical characteristics of both lenses were also affected. ConclusionsThe results provide in vitro evidence that lysozyme could not be completely removed from orthokeratology lenses. Both surface and optical properties were affected by the deposition of tear film components. However, only one commercial multipurpose care solution was used to clean the lens in this study when the main ingredient was a surfactant, and the results might be different when other care regimens with other key ingredients are used. In addition, whether tear film component deposition might result in increased risks of infection or corneal abrasion will require further investigation.

Lacrimal and meibomian gland evaluation in dry eye disease: A mini-review.

Lacrimal and meibomian glands contribute to the aqueous and lipid components of tear film, respectively. Their evaluation remains central to diagnosing and managing dry eye disease (DED). The review discusses the differences and reliability of various diagnostic tests and commercially available devices used for DED diagnosis. Slit-lamp-based techniques are direct palpebral lobe and tear flow assessment, Schirmer test, meibum quality and expressibility, and evaluation of tear meniscus height. Non-invasive tear meniscus height (TMH), tear break-up time (TBUT), lipid layer thickness (LLT), and meibography are machine-based diagnostic tests. The structure-function correlation of the tear-producing glands gives more comprehensive details than either information alone. Many devices are available in the market, which make DED diagnosis an easy feat, but the tests should be interpreted keeping in mind the intra-observer and inter-observer repeatability. Also, the tear film displays a huge variability as per the environmental conditions and impact of blinking. Hence, the examiner should be well versed with the techniques and repeat the test two to three times to obtain an average reading, which is more reliable. The recommended sequence of tests for diagnosing DED is a dry eye questionnaire, TMH, LLT, NIBUT (FBUT if non-invasive test is unavailable but should be performed after osmolarity), tear osmolarity, meibography, and ocular surface staining. Invasive tests such as Schirmer should be performed after the non-invasive tear film diagnostic testing.

Ayurvedic Management of Shushkakshipaka w. s. r. to Dry Eye SyndromeA Review.

The windows to the soul are the eyes. Since the Vedic and Samhita times, Ayurvedic ancient writings have discussed the eye and its disorders, demonstrating the significance of the eye and ways to protect it. Because of this, eye care has always been a top priority. Clinical characteristics of Dry eye are frequently observed in Suskaksipakain Ayurveda. It's common to equate dry eyes to shushkakshipaka.However, a closer examination of the dry eye symptoms reveals two Ayurvedic terms that are closely related to the illness. The first stage of vartma roga(disease of the lid), which is defined as vata prakopaover the surface structures of the eye due to a lack of snigdha bhava, either in the form of abnormal aqueous or lipid component of tear film, which in turn creates difficulty in opening the lids, pricking pain, and a gritty feeling, is known as Krichronmeela. Shushkakshipaka, a sarvakshidisease, appears when pita becomes engaged in the pathophysiology and samprapti deepens into the dhatus over the surface structures of the eye, such as the conjunctiva and cornea.

Sphingolipidomics of Bovine Pink Eye: A Pilot Study.

Simple SummaryThe liquid tear film, which protects the eye from the environment, is a dynamic fluid containing a large number of complex lipids. Disruptions of these lipids by infections can result in damage to the eye and ultimately blindness. In this study we characterized various lipid subfamilies present in the tear film of the eye and the effect of pink eye infections in cattle. Our findings demonstrate that the pink eye infections dramatically decrease the levels of lipids in the tear film covering the eye and suggest that this is a major factor in the development of blindness in infected cattle.Sphingolipids are essential structural components of tear film that protect the surface of the eye from dehydration. A detailed analysis of the effects of pink eye infections on the sphingolipidome in cattle has not previously been undertaken. We recently published a new assay utilizing high-resolution mass spectrometric monitoring of the chloride adducts of sphingolipids that provides enhanced sensitivity and specificity. Utilizing this assay, we monitored decreases in the levels of tear film ceramides with short-chain fatty acids, hydroxy-ceramides, phytoceramides, and hydroxy-phytoceramides. Dihydroceramide levels were unaltered and increased levels of ceramides with long-chain fatty acids (24:0 and 24:1) were monitored in cattle with pink eye. The data from this pilot study (n = 8 controls and 8 pink eye) demonstrate a major disruption of the lipid tear film layer in pink eye disease, that can result in severe eye irritation and damage.

Lysozyme Deposition on Contact Lenses in an In Vitro Blink-Simulation Eye Model Versus a Static Vial Deposition Model.

To evaluate active lysozyme deposition on daily disposable (DD) contact lenses (CL) using a novel in vitro blink model. Three conventional hydrogel DD CL materials (etafilcon A, omafilcon A, nelfilcon A) and three silicone hydrogel DD CL materials (delefilcon A, senofilcon A, somofilcon A) were tested. The device blink rate was set to 6 blinks/min with a tear flow rate of 1 μL/min using an artificial tear solution (ATS) containing lysozyme and other typical tear film components. After incubation at 2, 4, or 8 hr, lenses were removed, and lysozyme activity was measured. A separate experiment was conducted with lenses incubated in a static vial containing 480 μL of ATS. Etafilcon A deposited significantly higher amounts of active lysozyme (402±102 μg/lens) than other lens materials after 8 hr (P<0.0001). Etafilcon A had a higher amount of active lysozyme using the blink model compared with the static vial (P=0.0435), whereas somofilcon A (P=0.0076) and senofilcon A (P=0.0019) had a higher amount of lysozyme activity in the vial compared with the blink model. The blink model can be tuned to provide quantitative data that closely mimics ex vivo studies and can be used to model deposition of lysozyme on CL materials.

Extracts of different pollen species and their effect on human tear fluid and an epithelial cell line

Purpose Hazelnut and birch pollen are known to destroy tear film components and attack ocular surface cells. We investigated further pollen species from different plant families, whether they show similar effects on human tear fluid and an epithelial cell line in vitro, to provide a broad basis for further research on pollen reactions affecting the tear film and ocular surface. Materials and methods Regional pollen species from different plant families (Adoxaceae, Betulaceae, Fagaceae, Juglandaceae, Malvaceae, Oleaceae, Pinaceae, Plantaginaceae, Poaceae, Salicaceae, Sapindaceae) were collected. Their proteolytic activity was evaluated by Zymography. Human tear fluid and cells of an epithelial cell line were incubated with pollen extracts. Tear fluid was analyzed by Polyacrylamide gel electrophoresis (PAGE). Cytomorphology was assessed microscopically and cell viability by proliferation (MTS), water-soluble tetrazolium (WST-1) assay and the impedance-based xCELLigence real-time analysis (RTCA). Results Zymography revealed significant protease activity and PAGE showed the degradation of tear proteins by different pollen species. Cells incubated with pollen extracts presented dose- and time-dependent cytomorphological changes. MTS, WST-1, and RTCA revealed cytostatic as well as cytotoxic effects of pollen extracts. Conclusions Pollen species from different plant families exert proteolytic activity and degrade human tear fluid as well as epithelial cells, which may play a crucial role in the pathogenesis of allergic and non-allergic reactions affecting the ocular surface.

Hialid®/Hyalein® (sodium hyaluronate) ophthalmic solution in dry eye syndrome: a profile of its use

Hialid®/Hyalein® (also known as Sanlein®) is an effective and well tolerated ophthalmic solution for the treatment of keratoconjunctival epithelial disorder associated with dry eye syndrome. Hialid®/Hyalein® contains the active ingredient sodium hyaluronate, a natural component of tear film, which has high water retention ability, increases tear film stability and accelerates corneal wound healing. One drop in each eye 5–6 times daily improves the symptoms of dry eye, as well as objective measures of corneal staining. The efficacy of the solution is noninferior to that of ciclosporin 0.05% anionic emulsion eye drops in this patient population.

Imaging Approaches for Contact Lens Deposition.

Deposition on contact lenses (CLs) starts quickly after their application to the ocular surface. Deposits may be composed of tear film components or other extraneous substances. These deposits have been related to various adverse conditions of the eye, leading to reduced biocompatibility between the CLs and the ocular surface. Analysis of these deposits is essential to better elucidate the relationship between these deposits and their adverse reactions so that better methods of increasing biocompatibility can be developed. Although methods such as enzymatic assays are available for quantitative analysis, they do not provide a complete picture of the deposition (e.g., lack of morphological details), and therefore, the use of imaging methods that can provide both qualitative and quantitative information about the deposits may be more preferable. Therefore, a search of the peer-reviewed literature that focused on imaging methods in the analysis of deposits on CLs was conducted. Various methods of imaging deposits in-vitro, in-vivo, or ex-vivo have been described along with the associated results. Imaging methods using fluorescence-based techniques and scanning electron microscopy appear to be the most frequently used methods. Some of the described methods not only provided morphologies but also identified the types of various deposits that were attached to the CLs. Various CL materials possessed different deposition morphologies and different quantities of the attached deposits. Further imaging studies performed in conjunction with other methods that could identify and quantify the deposits at a molecular level are recommended.

Biological and Clinical Implications of Lysozyme Deposition on Soft Contact Lenses.

ABSTRACTWithin a few minutes of wear, contact lenses become rapidly coated with a variety of tear film components, including proteins, lipids, and mucins. Tears have a rich and complex composition, allowing a wide range of interactions and competitive processes, with the first event observed at the interface between a contact lens and tear fluid being protein adsorption. Protein adsorption on hydrogel contact lenses is a complex process involving a variety of factors relating to both the protein in question and the lens material. Among tear proteins, lysozyme is a major protein that has both antibacterial and anti-inflammatory functions. Contact lens materials that have high ionicity and high water content have an increased affinity to accumulate lysozyme during wear, when compared with other soft lens materials, notably silicone hydrogel lenses. This review provides an overview of tear film proteins, with a specific focus on lysozyme, and examines various factors that influence protein deposition on contact lenses. In addition, the impact of lysozyme deposition on various ocular physiological responses and bacterial adhesion to lenses and the interaction of lysozyme with other tear proteins are reviewed. This comprehensive review suggests that deposition of lysozyme on contact lens materials may provide a number of beneficial effects during contact lens wear.

Study of dehydration and water states in new and worn soft contact lens materials

The purpose of this study was to examine the in vitro dehydration characteristics of new and worn conventional and silicone-hydrogel contact lenses. Four contact lens materials were investigated: three conventional hydrogels (etafilcon, nelfilcon, omafilcon) and one silicone-hydrogel (narafilcon). Gravimetric data were obtained with analytical balance with 1 min intervals. Quantitative parameters of water content and dehydration rate were calculated allowing quantitative description of dehydration process. Differential scanning calorimetry was used to monitor changes in water states in samples studied. As expected, dehydration behavior of each material is different in terms of mean dehydration rate values and phases of dehydration. Gravimetric data allowed us to distinguish three phases of dehydration. Interestingly, the effect of the osmolality of storing solutions on dehydration was found – lenses stored in hyperosmotic solutions needed more time to achieve equilibrium with the environment. Effect of wearing on dehydration patterns and water properties was confirmed. In worn samples, a decrease in water content was observed. Additionally, there was a change in water structure after 6 h of wearing in all lenses studied. This behavior may be ascribed to tear film components deposition and changes in surface wettability that appear during wearing.

Impact of tear film components on the conformational state of lysozyme deposited on contact lenses

To investigate the impact of lactoferrin and lipids on the kinetic denaturation of lysozyme deposited on silicone and conventional hydrogel lenses, using a complex artificial tear solution (ATS). Two silicone hydrogel lenses (AIR OPTIX AQUA; lotrafilcon B and ACUVUE OASYS; senofilcon A) and two conventional hydrogel lenses (ACUVUE 2; etafilcon A and PROCLEAR; omafilcon A) were incubated in four solutions: an ATS, ATS without lactoferrin, ATS without lipids, and ATS without lactoferrin and lipids. At various time points over a 28-day period, the percentage of active lysozyme per lens was determined using a fluorescence activity assay and an ELISA. After 28 days, the percentage of active lysozyme extracted from etafilcon A lenses in all solutions was significantly higher than all other lens materials (p < 0.001). For lotrafilcon B, senofilcon A, and omafilcon A lenses, lysozyme denaturation was greatest during the first week of incubation and before reaching a plateau (p > 0.05). The inclusion of lipids in the ATS significantly increased the lysozyme denaturation on both silicone hydrogel materials (p < 0.001), while in the presence of lactoferrin, lysozyme activity on senofilcon A lenses was significantly higher (p < 0.001). Lysozyme activity on both conventional lenses was not significantly affected by either lactoferrin or lipids (p > 0.05). Lactoferrin and lipids have an impact on the denaturation of lysozyme deposited onto silicone hydrogel contact lenses, while conventional hydrogel lenses were unaffected. Future in vitro studies should consider the impact of tear film components when investigating protein deposition and denaturation on contact lenses.

Dry Eye Syndrome An Ayurvedic Approach

The optical stability and normal function of the eye depend on an adequate supply of fluid covering its surface. The tear films components interact to form a stable structure composed of mucin aqueous solution and lipid that protects the ocular surface and provides a medium for delivery of supportive and protective proteins. Alteration of any one of the tear film components can destabilize the tear film and lead to the initiation of inflammatory process of ocular surface which in turn may leads to dry eye syndrome. In ayurveda the disease Shushkakashipaka is very similar to Dry eye syndrome in modem ophthalmology. All acharyas included Shushkakshipaka as a disease which is affecting all parts of eye ball because this condition can cause major problems to all parts of eye like Shukla Krishna. Drishti mandalas if not treated property The different acharyas opinions that vitiation of Vata. Pittha and Raktha Will play the major role in the disease pathology Narrowing of palpebral aperature Crusting of lids. Blurred vision Stuck eyelids.foreign body sensation Pnckling pain teanng pain mucoid discharge etc are the clinical features explained in ayurveda. Systemic and local Vata-Pittha shamana and Dhatuposhana treatment is highly recommended starting from the Snehapana.

The Impact of Tear Film Components on In Vitro Lipid Uptake

To analyze the influence of various tear film components on in vitro deposition of two lipids (cholesterol and phosphatidylcholine) on three contact lens materials. Etafilcon A, balafilcon A, and senofilcon A were incubated in four different incubation solutions for 3 or 14 days: an artificial tear solution containing lipids and proteins, a protein tear solution containing proteins and the lipid of interest, a lipid tear solution containing lipids and no proteins, and a single lipid tear solution containing the lipid of interest only. Each incubation solution contained one of the two radiolabeled lipids: C-cholesterol (C) or C-phosphatidylcholine (PC). After soaking, lenses were removed from the incubation solution, the lipids were extracted and quantified using a beta counter, and masses of lipid were calculated using standard calibration curves. This experiment examined several different parameters influencing lipid deposition on contact lenses, including lens material, length of incubation, and the composition of the incubation solution. Overall, lipid deposited differently on different lens materials (p < 0.0005), with the order of deposition most commonly being balafilcon > senofilcon > etafilcon. Incubation solution had a large impact on how much lipid was deposited (p < 0.00001), although cholesterol and phosphatidylcholine demonstrated different deposition patterns. Lipid deposition after 14 days of incubation was consistently greater than after 3 days (p < 0.02). This in vitro study demonstrates that C and PC deposition are cumulative over time and that silicone hydrogel materials deposit more lipid than group IV conventional hydrogel materials. It also clearly demonstrates that deposition of C and PC is influenced by the composition of the incubation solution and that in vitro models must use more physiologically relevant incubation solutions that mimic the natural tear film if in vitro data is to be extrapolated to the in vivo situation.

Impact of Tear Film Components on Lysozyme Deposition to Contact Lenses

To investigate the impact of lactoferrin and lipids on the kinetic deposition of lysozyme on silicone and conventional hydrogel lenses, using a complex artificial tear solution (ATS). Two silicone hydrogel lenses (AIR OPTIX AQUA; lotrafilcon B and ACUVUE OASYS; senofilcon A) and two conventional hydrogel lenses (ACUVUE 2; etafilcon A and PROCLEAR; omafilcon A) were investigated. Lenses were incubated in four different solutions: a complex ATS consisting of various salts, lipids, proteins, and mucins, an ATS without lactoferrin (ATS w/o Lac), an ATS without lipids (ATS w/o Lip), and an ATS without lactoferrin and lipids (ATS w/o Lac & Lip), each containing 2% radiolabeled (125I) lysozyme (1.9 mg/ml). After each time point (4, 12 h and 1, 2, 3, 5, 7, 14, 21, 28 days), the amount of lysozyme per lens was quantified. After 28 days, lotrafilcon B lenses incubated in ATS deposited significantly less lysozyme (9.7 ± 1.4 μg) than when incubated in solutions not containing lactoferrin and lipids (more than 11.8 μg) (p < 0.001). Lysozyme uptake to senofilcon A lenses was higher in ATS w/o Lip (5.3 ± 0.1 μg) compared with other solutions (less than 3.9 μg) (p < 0.001). Etafilcon A lenses deposited the most lysozyme in all four solutions compared with the rest of the lens types (p < 0.001). For etafilcon A lenses, less lysozyme was deposited when incubated in ATS w/o Lip (588.6 ± 0.4 μg) compared with the other solutions (more than 642.6 μg) (p < 0.001). Omafilcon A lenses in ATS w/o Lac accumulated significantly less lysozyme (12.8 ± 1.0 μg) compared with the other solutions (more than 14.2 μg) (p < 0.001). An ATS containing lactoferrin and lipids impacts lysozyme deposition on both silicone and conventional hydrogel contact lenses. When performing in vitro experiments to study protein deposition on contact lenses, more complex models should be used to better mimic the human tear film.

Factors Affecting Evaporation Rates of Tear Film Components Measured In Vitro

With increasing age and in patients affected with dry-eye symptoms, the human tear film becomes more unstable and exhibits shorter tear break-up times. We examined whether the inclusion of proteins and lipids to water affected the evaporation rates measured in vitro and could account for the lower rates reported previously from in vivo measurements. The impact of temperature, air flow, and humidity on the evaporation rate of tears was measured in vitro. Lipid-protein interactions were measured using fluorescence spectroscopy and in vitro rates of evaporation were performed gravimetrically. Human reflex tears evaporated at a rate similar to that of water. A temperature increase from 25 degrees C to 34 degrees C caused a threefold increase in the evaporation rates of tears in still air. Further increases were observed under a current of dry air. Wax, mucin, lysozyme, or beta-lactoglobulin did not influence significantly the rates of evaporation measured in vitro. In contrast, lipid layered on the surface resulted in a 23% decrease in the rates. Environmental factors affect evaporation rates significantly and should be carefully controlled when performing in vivo measurements. The presence of a lipid layer lowers evaporation rates. The significantly lower rates of evaporation of tears measured in vivo suggest that with the lipid layer intact, the high reserve capacity of the lacrimal gland to provide both unstimulated and stimulated tear flow is more than enough to compensate for evaporative loss. However, with dry eye, increased rates of evaporation and decreased lacrimal tear flow could result in decreased break-up times.

Qualitative and quantitative tear film abnormalities in dogs

Tear film disorders in dogs can be classified into quantitative or qualitative abnormalities, or both, and are commonly observed in daily clinical practice. Inadequate production of one or more tear film components can lead to variable degrees of ocular disorders, called keratoconjunctivitis sicca. Keratoconjunctivitis sicca in dogs has several causes, but in most cases the disease is idiopathic, with T lymphocytes playing a role. In veterinary medicine, the diagnosis is made based on the results of the Schirmer tear test. In this article, we review aspects related to the etiopathogenesis and diagnosis of keratoconjunctivitis sicca in dogs and discuss new therapeutic modalities for this disease.

Current status of researches on ocular surface related mucins

Mucins comprise a family of highly glycosylated, high-molecular-weight glycoproteins. Ocular surface mucins are the major component of the tear film. They play important role in maintaining the ocular surface health. The alterations in the structure and expression pattern of mucins are related to the pathophysiology process of many ocular surface diseases. This paper reviewed recent researches on ocular surface related mucins that would provide bases to exploring the pathogenesis, diagnosis, and therapeutic tragedies of ocular surface diseases.