Performance of Tear Osmolarity Compared to Previous Diagnostic Tests for Dry Eye Diseases

On tear film breakup (TBU): dynamics and imaging

We report the results of some recent experiments to visualize tear film dynamics. We then study a mathematical model for tear film thinning and tear film breakup (TBU), a term from the ocular surface literature. The thinning is driven by an imposed tear film thinning rate which is input from in vivo measurements. Solutes representing osmolarity and fluorescein are included in the model. Osmolarity causes osmosis from the model ocular surface, and the fluorescein is used to compute the intensity corresponding closely to in vivo observations. The imposed thinning can be either one-dimensional or axisymmetric, leading to streaks or spots of TBU, respectively. For a spatially-uniform (flat) film, osmosis would cease thinning and balance mass lost due to evaporation; for these space-dependent evaporation profiles TBU does occur because osmolarity diffuses out of the TBU into the surrounding tear film, in agreement with previous results. The intensity pattern predicted based on the fluorescein concentration is compared with the computed thickness profiles; this comparison is important for interpreting in vivo observations. The non-dimensionalization introduced leads to insight about the relative importance of the competing processes; it leads to a classification of large vs small TBU regions in which different physical effects are dominant. Many regions of TBU may be considered small, revealing that the flow inside the film has an appreciable influence on fluorescence imaging of the tear film.

Computed flow and fluorescence over the ocular surface

Fluorescein is perhaps the most commonly used substance to visualize tear film thickness and dynamics; better understanding of this process aids understanding of dry eye syndrome which afflicts millions of people. We study a mathematical model for tear film flow, evaporation, solutal transport and fluorescence over the exposed ocular surface during the interblink. Transport of the fluorescein ion by fluid flow in the tear film affects the intensity of fluorescence via changes in concentration and tear film thickness. Evaporation causes increased osmolarity and potential irritation over the ocular surface; it also alters fluorescein concentration and thus fluorescence. Using thinning rates from in vivo measurements together with thin film equations for flow and transport of multiple solutes, we compute dynamic results for tear film quantities of interest. We compare our computed fluorescent intensity distributions with in vivo observations. A number of experimental features are recovered by the model.

Tear Osmolarity and Correlation With Ocular Surface Parameters in Patients With Dry Eye

PURPOSE

To analyze the distribution of tear film osmolarity in patients with dry eye and its association with other ocular surface parameters.

METHODS

Tear osmolarity and other quantitative dry eye parameters were obtained from patients with 1) clinically significant dry eye (significant symptoms and ocular surface staining, n = 131), 2) symptoms-only dry eye (significant symptoms but no significant ocular surface staining, n = 52), and 3) controls (no significant symptoms or staining, n = 42).

RESULTS

Tear osmolarity varied significantly across groups (P = 0.01), with patients with clinically significant dry eye having the highest tear osmolarity (312.0 ± 16.9 mOsm/L), control patients having the lowest tear osmolarity (305.6 ± 9.7 mOsm/L), and patients with symptoms-only dry eye falling in between (307.4 ± 5.6 mOsm/L). Patients with clinically significant dry eye also tended to have a greater intereye difference in osmolarity (12.0 ± 13.4) than did the individuals with symptoms-only dry eye (9.1 ± 12.4) and controls (9.0 ± 7.4) (P = 0.06). In multivariable regression models, higher tear osmolarity was associated with higher Ocular Surface Disease Index, discomfort subscore (P = 0.02), and higher corneal and conjunctival staining scores (P < 0.01 for both). Worse eye tear osmolarity was not correlated with the corresponding tear film breakup time or Schirmer test (P > 0.05 for both).

CONCLUSIONS

Individuals with symptomatic dry eye that is not yet clinically significant seem to have higher and more variable osmolarity measurements than controls, potentially indicating that changes in osmolarity precede clinical findings.

Physical forces modulate cell differentiation and proliferation processes

Currently, the predominant hypothesis explains cellular differentiation and behaviour as an essentially genetically driven intracellular process, suggesting a gene-centrism paradigm. However, although many living species genetic has now been described, there is still a large gap between the genetic information interpretation and cell behaviour prediction. Indeed, the physical mechanisms underlying the cell differentiation and proliferation, which are now known or suspected to guide such as the flow of energy through cells and tissues, have been often overlooked. We thus here propose a complementary conceptual framework towards the development of an energy-oriented classification of cell properties, that is, a mitochondria-centrism hypothesis based on physical forces-driven principles. A literature review on the physical-biological interactions in a number of various biological processes is analysed from the point of view of the fluid and solid mechanics, electricity and thermodynamics. There is consistent evidence that physical forces control cell proliferation and differentiation. We propose that physical forces interfere with the cell metabolism mostly at the level of the mitochondria, which in turn control gene expression. The present perspective points towards a paradigm shift complement in biology.

Analysis of basal and reflex human tear osmolarity in normal subjects: assessment of tear osmolarity

PURPOSE

The aim of this study is to evaluate the difference between reflex and basal tear osmolarity among healthy normal subjects.

METHOD

The right eyes of 20 healthy normal male subjects aged 20 to 40 years were recruited for this study. The inclusion criteria for the subjects were the Ocular Surface Disease Index questionnaire score of less than 12 and wetting length of the phenol red thread of more than 10 mm. Tear film osmolarity was assessed using TearLab osmometer. Basic tear osmolarity was measured normally without inducing any irritation to the eye. In order to stimulate reflex tear, subjects were asked to open their eye as long as they can till they feel ocular surface irritation (minimum 20 s).

RESULTS

The mean score on the Ocular Surface Disease Index questionnaire was 5.5 ± 3. The mean value obtained from the phenol red thread was 21 ± 4.5 mm. There were no statistically significant differences between the osmolarity readings of basal and reflex tear osmolarity (p > 0.05). The mean value was 308 ± 12 and 306 ± 9 mOsm/l for basic and reflex tear osmolarity, respectively.

CONCLUSION

This study found that the osmolarity of the basal and reflex tears fell within the same range. The values found in this study are in agreement with published results for normal subjects.

Contact lens to measure individual ion concentrations in tears and applications to dry eye disease

Dry eye disease (DED) affects millions of individuals in the United States and worldwide, and the incidence is increasing with an aging population. There is widespread agreement that the measurement of total tear osmolarity is the most reliable test, but this procedure provides only the total ionic strength and does not provide the concentration of each ionic species in tears. Here, we describe an approach to determine the individual ion concentrations in tears using modern silicone hydrogel (SiHG) contact lenses. We made pH (or H₃O⁺, hydronium cation,/OH^-, hydroxyl ion) and chloride ion (two of the important electrolytes in tear fluid) sensitive SiHG contact lenses. We attached hydrophobic C18 chains to water-soluble fluorescent probes for pH and chloride. The resulting hydrophobic ion sensitive fluorophores (H-ISF) bind strongly to SiHG lenses and could not be washed out with aqueous solutions. Both H-ISFs provide measurements which are independent of total intensity by use of wavelength-ratiometric measurements for pH or lifetime-based sensing for chloride. Our approach can be extended to fabricate a contact lens which provides measurements of the six dominant ionic species in tears. This capability will be valuable for research into the biochemical processes causing DED, which may improve the ability to diagnose the various types of DED.

Comparison of the clinical efficacy of preserved and preservative-free hydroxypropyl methylcellulose-dextran-containing eyedrops

PURPOSE

This study aimed to compare the efficacy of two sustained-release formulation of artificial tear drops.

PATIENTS AND METHODS

This is a randomized patient-masked clinical trial, a total 88 patients into two group A (n=41; with single dose of artificial tear, containing dextran 70, 1mg/ml and hypromellose, 3mg/ml hydroxypropyl methylcellulose (HPMC) and group B (n=47; with multidose of artificial tear, containing 0.3g HPMC and 0.1g of dextran 70, with 0.01% benzalkonium chloride (BAK) as preservative) were completed the study. The ocular surface disease index (OSDI) questionnaire, tear break up time (TBUT), corneal and conjunctival staining and Schirmer test, were performed. Repeated measures ANOVA was used to assess the differences among the two products. A p-value less than 0.05 was considered significant.

RESULTS

The mean of age of the participants in the Group A and B was 44.08±6.29 (range, 33-58 years) years and 45.83±8.42 (31-60 years), respectively. In comparing two groups before the intervention, the OSDI scores, the TBUT scores, the conjunctival and corneal staining scores and the Schirmer scores did not show statistically significant differences (p=0.339, p=0.640, p=0.334, p=0.807 and p=0.676, respectively). After 4 weeks, the OSDI scores, conjunctival and corneal staining scores showed improvement in compare to those before the intervention (p<0.001). But, the differences for the Schirmer test score and TBUT score was not significant (p=0.115, p=0.013, respectively).

CONCLUSION

Our outcomes indicated that improvement occurred with use of both products but there was no statistically significant difference between them.

Impact of Smoking on the Ocular Surface, Tear Function, and Tear Osmolarity

PURPOSE

This study evaluated the effects of cigarette smoking on the ocular surface, tear function, and tear osmolarity.

MATERIALS AND METHODS

A total of 50 smokers with at least 5 years of heavy smoking (defined as 1 pack/day) and 51 nonsmoking, healthy individuals were enrolled. Tear osmolarity was measured with an osmometer (TearLab^™ Osmolarity System). Ocular surface examinations involved corneal fluorescein staining, measurement of the tear film breakup time (TBUT), the Schirmer 1 test, measurement of corneal sensitivity with a Cochet-Bonnet esthesiometer, and conjunctival impression cytology. Dry eye symptoms were scored using the Ocular Surface Disease Index (OSDI) questionnaire. The results were compared with those from an age and sex-matched control group. The Chi-squared and independent sample t-tests were used for statistical analyses.

RESULTS

The smokers had significantly higher tear osmolarity values (305.38 ± 9.81 vs. 301.14 ± 7.04 mOsm/L; p = 0.014) and OSDI scores (34.13 ± 16.58 vs. 18.09 ± 9.61; p < 0.001) than the healthy controls. However, the TBUT, corneal sensitivity, and goblet cell density were significantly lower in smokers compared to healthy controls, but the fluorescein staining and Schirmer 1 test results were not statistically different between the smokers and controls.

CONCLUSION

Smoking results in increased osmolarity of the tear film, which can damage the ocular surface and tear function.

Interdisciplinary, Comprehensive Oral and Ocular Evaluation of Patients with Primary Sjögren's Syndrome

A comprehensive evaluation of oral and ocular symptoms and findings in primary Sjögren’s syndrome (pSS) patients may provide valuable information for management. Medical history was obtained from female pSS patients, and sex- and age-matched non-SS patients with sicca symptoms (non-SS sicca controls) as well as healthy subjects without sicca complaints (healthy controls). Oral (Summated Xerostomia Inventory, SXI) and ocular (McMonnies Dry Eye questionnaire, MDEIS, and Ocular Surface Disease Index, OSDI) subjective complaints were recorded. Objective findings including clinical oral dryness scores (CODS), unstimulated and stimulated saliva secretion rates (UWS/SWS), Schirmer I test, tear osmolarity, tear film break-up time (TFBUT), and ocular surface staining (OSS) were determined. The pSS and non-SS sicca controls were extensively troubled by subjective dryness, while the pSS group had higher CODS, significantly lower saliva and tear secretion, shorter TFBUT and higher OSS than both control groups. Furthermore, candida counts were significantly higher in the pSS patients. In the pSS group, subjective oral dryness significantly correlated with ocular dryness (MDEIS: r = 0.5, OSDI: r = 0.413) and SWS was significantly correlated with Schirmer I (r = 0.419). The findings imply that interdisciplinary subjective and objective evaluation of patients with xerostomia and xerophthalmia not only have implications for patient care, but also may guide clinicians in differentiating between pSS and non-SS sicca patients.

Vitamin D Replacement Improves Tear Osmolarity in Patients with Vitamin D Deficiency

BACKGROUND

Vitamin D deficiency is a common health problem worldwide. Many parts of the human eye, including the epithelium of the cornea, lens, ciliary body, and retinal pigment epithelium, as well as the corneal endothelium, ganglion cell layer, and retinal photoreceptors, contain vitamin D receptor (VDR). Dry eye is also a common health problem. An adequate tear film is required for maintaining health and function of the eye. Tear hyperosmolarity is considered to be the cause of ocular surface inflammation, symptoms, and tissue damage. It is well-documented that vitamin D has an anti-inflammatory action. We aimed to investigate the effect of vitamin D replacement on tear osmolarity in patients with vitamin D deficiency.

METHODS

A total of 44 patients (38 females, six males, mean age:43.5 ± 12.8 years) with vitamin D deficiency currently managed by the Endocrinology and Metabolism Department of Diskapi Training and Research Hospital in Turkey were enrolled in the study. Patients were given 50,000 units of 25(OH)D₃ intramuscularly, once weekly, over a period of eight weeks. All of the patients underwent tear function osmolarity (TFO) measurement initially and eight weeks after vitamin D replacement. Demographic, anthropometric, and biochemistry data of patients were recorded.

RESULTS

The mean TFO was significantly decreased (313.7 ± 17.3 mOsm/L; 302.7 ± 14.2 mOsm/L, p<0.001) at the end of the second month; 25(OH)D₃ concentrations increased from 8.3 ± 3.5 ng/mL to 68.8 ± 22.3 ng/mL (p<0.001). The mean levels of hsCRP, FPG, P were 2.5 ± 2.5 mg/L, 5.09 ± 0.48 mmol/L, 1.06 ± 0.16 mmol/L initially, and 3.8 ± 5.9 mg/L, 5.11 ± 0.68 mg/dL, 1.09 ± 0.16 mmol/L after vitamin D replacement, respectively (p>0.05). The mean Ca level was 2.37 ± 0.07 mmol/L initially and 2.35 ± 0.07 mmol/L after vitamin D replacement (p<0.05). The change of TFO was negatively correlated with the variation of 25(OH)D₃ before and after replacement in patients with dry eye disease (r=-0.390, p=0.049).

CONCLUSIONS

As a consequence of the presence of VDR and 1α-hydroxylase in different parts of the eye, vitamin D replacement improves tear hyperosmolarity that is considered to be induced by ocular surface inflammation.

The effect of intravitreal injections on dry eye, and proposed management strategies

Intravitreal injection of anti-vascular endothelial growth factor (anti-VEGF) agents has become a commonly used treatment method for a number of ophthalmic conditions, including age-related macular degeneration. Although anti-VEGF therapy has shown promising results for many patients, there are several aspects of its application that have not been thoroughly investigated. One of these is the development and/or escalation of concurrent dry eye syndrome. Many patients undergoing treatment are already predisposed to dry eye disease due to their age and overall ocular health. As dry eye can have a substantial impact on quality of life, it has become increasingly apparent that the clinical signs and symptoms should be closely monitored and aggressively managed. This will allow for the optimization of patient comfort and visual potential. Here, we discuss the reasons why dry eye may develop during the course of repeated ocular anti-VEGF therapy, highlighting the key concerns about current practices and proposing possible solutions to improve the outcome for the patients.

Lack of Agreement among Electrical Impedance and Freezing-Point Osmometers

PURPOSE

To assess the interchangeability of tear osmolarity measurements between electrical impedance and freezing-point depression osmometers and to analyze inter-eye tear osmolarity variability measured with these osmometers in healthy subjects.

METHODS

Tear osmolarity was measured using the TearLab osmometer (OcuSense Inc., San Diego, CA) and the Fiske 210 microsample osmometer (Advanced Instruments Inc., Norwood, MA). We randomly selected one eye in 50 subjects (29 women, 21 men; mean age, 33.16 ± 6.11 years) to analyze whether osmolarity measurements by these osmometers were interchangeable. Both eyes of 25 patients (15 women, 10 men; mean age, 34.32 ± 6.37 years) were included to analyze inter-eye osmolarity variability.

RESULTS

The mean tear osmolarity values measured with the TearLab osmometer were higher (305.22 ± 16.06 mOsm/L) than those with the Fiske 210 osmometer (293.40 ± 12.22 mOsm/L), with the intraclass correlation coefficient being 0.23 (p = 0.051). A Bland-Altman plot showed that the systems were not interchangeable because there was a systematic difference, with the limits of agreement being -17.93 to 41.57 mOsm/L. There were no statistically significant differences (p = 0.5006 and p = 0.6533, respectively) between an individual's eyes measured with either osmometer.

CONCLUSIONS

Because the TearLab tear osmolarity measurements were higher than those of the Fiske 210 measurements and the limits of agreement were too wide, the two osmolarity values cannot be used interchangeably. In healthy subjects, there is no difference in tear osmolarity between right and left eyes of the same individual measured with both instruments.

Dry eye disease in patients with metabolic syndrome

OBJECTIVES

To evaluate dry eye disease (DED) in patients with metabolic syndrome (MetS) and compare with healthy individuals.

METHODS

The study was conducted in the Ophthalmology and Endocrinology Department of Bagcilar Education and Research Hospital, a tertiary care center in Istanbul, Turkey, between January and December 2015. In this prospective case-controlled study, dry eye disease tests were performed on 44 patients with MetS and 43 healthy controls. TearLab Osmolarity System, which is a lab-on-a-chip technology, was used to measure tear osmolarity. McMonnies & Ho symptoms questionnaire along with Schirmer I test and tear film break-up time (TFBUT) test were also performed. Statistical evaluation was performed by students' independent test.

RESULTS

There was no statistically significant difference in tear osmolarity, TFBUT, and McMonnies and Ho questionnaire scores between MetS and normal group. However, Schirmer I test was significantly higher in MetS group (14.8±9.4mm versus 20.4±9.4, p=0.007). In women subgroup, tear osmolarity was significantly higher in MetS group compared  to the normal group and over the cut-off score 308 mOsm/L (309.4±13.1 mOsm/L versus 301.2±8.7mOsm/L, p=0.012).

CONCLUSION

Patients with MetS present with lower tear volumes and a higher incidence of lacrimal gland hypofunction than age-matched controls. Especially women with MetS have higher tear osmolarities, which disrupt the normal functioning of the ocular surface and cause inflammation. Clinicians should be aware of higher DED incidence in patients with MetS for early treatment to prevent serious ocular complications.

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.

Long-term Effects of LASIK on Corneal Innervation and Tear Neuropeptides and the Associations With Dry Eye

PURPOSE

To investigate the associations between dry eye, corneal nerves, and tear neuroptides in dry eye after LASIK.

METHODS

A single visit cross-sectional study was performed. Twenty participants who had LASIK more than 12 months prior and 20 healthy participants were recruited. Ocular comfort, tear functions, ocular surface sensitivity, basal tear collection, and corneal nerve morphology assessments were conducted. Tear substance P and calcitonin gene-related peptide (CGRP) concentrations were determined using ELISAs. Differences in variables between groups were examined using an independent t test or Mann-Whitney U test, as appropriate. Associations between variables in the post-LASIK group were examined using a Spearman's correlation test. A P value of less than .05 was considered significant.

RESULTS

Central corneal nerve morphology parameters were all altered in the post-LASIK group (P < .05). Higher ocular discomfort (P = .01), tear CGRP concentration (P = .001), and conjunctival sensitivity (P < .009) were found in the post-LASIK group. There was a positive association between dry eye symptoms and superior corneal sensitivity (P = .51, P = .02) and tear substance P concentration (P = .52, P < .03).

CONCLUSIONS

This study provides evidence of the association between tear neuropeptides, conjunctival sensitivity, and symptoms in symptomatic patients after LASIK. The differences in nerve morphology, neuropeptide, and ocular surface sensitivity between symptomatic and asymptomatic patients after LASIK are required to better understand the mechanism of dry eye after LASIK. [J Refract Surg. 2016;32(8):518-524.].

Tear osmolarity and subjective dry eye symptoms in migraine sufferers

OBJECTIVE

Previous studies have suggested an association between dry eye and migraine. In a busy ophthalmologist clinic, quick identification of dry eye in migraine sufferers may improve their quality of life. Tear osmolarity is an objective and reliable tool for diagnosing dry eye. It has not been investigated in any population with migraine. Using tear osmolarity and questionnaires, we aimed to explore the relationship between dry eye and clinical symptoms in patients with migraine.

DESIGN

Prospective cross-sectional study.

PARTICIPANTS

Thirty-four adults with migraine sequentially recruited from a single neurologist's practice.

METHODS

Patients were assessed for subjective and objective signs of migraine and dry eye by using the Migraine Disability Assessment Score, the Ocular Surface Disease Index, and tear osmolarity (TearLab). Headache characteristics were compared by using χ², Fisher's exact, and Mann-Whitney U tests. Osmolarity scores were compared with scores for headache features.

RESULTS

Median age of patients was 38 years, and 76.5% were females. Severe migraine disability was reported in 75.6%, and 34.5% reported moderate to severe dry eye symptoms. Objectively, 49.5% had evidence of dry eye, significantly higher than the 20% recognized in the general population (p < 0.0001). Aura was found to occur more frequently with dry eye (43.8% vs 5.9%; p = 0.02). Those with daily headaches were also more likely to have higher tear osmolarity with marginal significance (median osmolarity 310 mOsm/L vs 299 mOsm/L; p = 0.08).

CONCLUSIONS

Patients with migraine, especially those with aura, appear more likely to have dry eye, as indicated by tear osmolarity. Tear osmolarity may also be greater in those who suffer from daily headaches.

Randomized comparison of in vivo performance of two point-of-care tear film osmometers

PURPOSE

To compare the in vivo precision of two commercially available point-of-care osmometers among normal subjects with no dry eye disease.

METHODS

Twenty healthy adults with healthy ocular surfaces were evaluated by licensed eye care practitioners. All subjects had low Ocular Surface Disease Index score (<5), normal tear breakup time (>10 seconds), and no evidence of corneal fluorescein staining. Five consecutive measurements of tear osmolarity were measured on each eye using each of the two osmometers: the TearLab Osmolarity System (TearLab) and the I-Med i-Pen (i-Pen), for a total of 200 measurements per device. Performance of the osmometers was determined by specificity, estimated by the percentage of osmolarity data at or below the clinical cutoff (308 mOsm/L) and precision, and represented by the standard deviation per subject. In addition, to assess analytical performance, on each day of patient testing, standardized osmolarity quality control solutions (338 mOsm/L) were tested on the TearLab per manufacturer instructions. i-Pen manufacturer instructions do not neither provide for, nor recommend quality control procedures.

RESULTS

The mean age of the 20 subjects was 27±8 years (range: 19-48 years, 16 females, four males). Over 2 months of testing, the TearLab reported analytical performance on quality control solutions of 335.8±4.2 mOsm/L with a coefficient of variation of 1.3%. In the subject cohort, 90.9% of TearLab measurements were in the normal range ≤308 mOsm/L. The i-Pen reported 37.5% of all measurements in the normal range. The average intra-subject osmolarity of the TearLab was 295.4±8.6 mOsm/L, which was significantly lower and less variable than the i-Pen, which reported an average of 319.4±20.3 mOsm/L (P<0.001). When the measurements were grouped by subject, the TearLab accurately identified 100% of subjects as normal while the i-Pen accurately identified only 15% of subjects as normal.

CONCLUSION

In this randomized comparative study of two point-of-care osmometers among normal, healthy non-dry eye subjects, the TearLab Osmolarity System demonstrated accuracy, precision, and agreement with clinical interpretation in line with the manufacturer claims. The i-Pen lacked sufficient performance to delineate subjects with and without dry eye disease.

Effect of thermal pulsation treatment on tear film parameters in dry eye disease patients

PURPOSE

The goal of this study was to evaluate the effect of thermal pulsation treatment on tear film parameters, specifically osmolarity and matrix metalloproteinase-9 (MMP-9), in patients with meibomian gland dysfunction (MGD) and dry eye disease (DED).

METHODS

A single-center review of 189 eyes that underwent thermal pulsation treatment was performed. Data were collected on pre and posttreatment osmolarity, MMP-9, tear break-up time (TBUT), and ocular surface disease index (OSDI) score. Statistical analyses were performed to detect any significant differences after treatment.

RESULTS

Thermal pulsation treatment led to significant improvements in TBUT (mean increase from 4.5 to 8.5 seconds [P<0.001]), OSDI score (mean decrease from 50.5 to 41.6 [P=0.024]), and MMP-9 (50% positive rate pretreatment compared to 26% positive rate post treatment [P<0.0001]). In the subset of patients who had a baseline osmolarity >307 mOsm/L (ie, diagnostic for DED), there was a significant improvement in the mean tear osmolarity from 317.1 to 306.6 mOsms/L after treatment (P=0.002).

CONCLUSION

Treating MGD is an important component of caring for the DED patient. Thermal pulsation treatment can improve MMP-9 levels on the ocular surface of patients with MGD and DED, as well as improve osmolarity in those with abnormal initial values. The present study suggests that meibomian glands play an important role in tear film dynamics and, as such, effective therapy such as thermal pulsation treatment aimed at improving meibomian gland health, can aid the restoration of normal tear film parameters and decrease patient symptoms of DED and MGD.

Prospective evaluation of intense pulsed light and meibomian gland expression efficacy on relieving signs and symptoms of dry eye disease due to meibomian gland dysfunction

Purpose

The aim of this study was to estimate the efficacy of intense pulsed light (IPL), followed by meibomian gland expression (MGX), for reducing the number and severity of signs and symptoms of dry eye disease (DED) secondary to meibomian gland dysfunction (MGD).

Patients and methods

In a prospective study conducted in two sites, 40 subjects (80 eyes) with moderate to severe MGD were enrolled. Major inclusion criteria consisted of at least two of the following measures being compatible with DED in both eyes: tear breakup time (TBUT), meibomian gland score (MGS), corneal fluorescein staining (CFS), Standard Patient Evaluation of Eye Dryness (SPEED) questionnaire, and tear film osmolarity (TFO). Enrolled patients underwent four treatment sessions, 3 weeks apart. Each treatment included the administration of 10–15 pulses of IPL on the cheeks and nose, followed by MGX of the upper and lower eyelids. TBUT, MGS, CFS, SPEED, TFO, and lipid layer thickness (LLT) were measured at baseline (BL) and at 9, 12, and 15 weeks after BL.

Results

Due to different staining methods used for TBUT measurements, TBUT and CFS were analyzed separately for each site. From BL to the final follow-up, the number of signs compatible with DED decreased from 3.3±0.1 to 1.4±0.1. TBUT improved by +93% (n=38; P<0.0001) and +425% (n=42; P<0.0001) for sites 1 and 2, respectively. SPEED, MGS, and CFS improved by −55% (n=80; P<0.0001), −36% (n=80; P<0.0001), and −58% (n=38; P<0.0001), respectively. In 20 eyes with abnormally elevated TFO at BL, TFO improved by −7% (n=20; P<0.005). LLT did not change (n=38; P=0.88).

Conclusion

In subjects with moderate to severe MGD, IPL combined with MGX reduced the number and severity of symptoms and signs of DED. Except for LLT, all examined outcome measures significantly improved after 15 weeks. These results support the efficacy of IPL + MGX in relieving both signs and symptoms of DED secondary to MGD.

Sjogren's syndrome from the perspective of ophthalmology

Sjogren's syndrome (SS) is an autoimmune disease affecting the lacrimal glands resulting in dry eye disease (DED). Ophthalmologists may be the first line of detection of Sjogren's syndrome given the frequency of DED in SS and that dry eye is often the presenting symptom. Numerous symptom questionnaires and tests have been developed to help diagnose DED, but as of yet, there is no "gold standard." Minimally invasive objective metrics are needed for a reliable diagnosis of DED. Currently there is no single test to diagnose SS-associated DED. Although there are several approaches to treatment, none are specific for DED in SS, and, generally, several methods need to be tried to find what works best for a specific patient. Treatment for DED continues to be an unmet medical need, especially given that DED in SS is typically on the severe end of the spectrum.

The Growing Need for Validated Biomarkers and Endpoints for Dry Eye Clinical Research

Purpose

Biomarkers with minimally invasive and reproducible objective metrics provide the key to future paradigm shifts in understanding of the underlying causes of dry eye disease (DED) and approaches to treatment of DED. We review biomarkers and their validity in providing objective metrics for DED clinical research and patient care.

Methods

The English-language literature in PubMed primarily over the last decade was surveyed for studies related to identification of biomarkers of DED: (1) inflammation, (2) point-of-care, (3) ocular imaging, and (4) genetics. Relevant studies in each group were individually evaluated for (1) methodological and analytical details, (2) data and concordance with other similar studies, and (3) potential to serve as validated biomarkers with objective metrics.

Results

Significant work has been done to identify biomarkers for DED clinical trials and for patient care. Interstudy variation among studies dealing with the same biomarker type was high. This could be attributed to biologic variations and/or differences in processing, and data analysis. Correlation with other signs and symptoms of DED was not always clear or present.

Conclusions

Many of the biomarkers reviewed show the potential to serve as validated and objective metrics for clinical research and patient care in DED. Interstudy variation for a given biomarker emphasizes the need for detailed reporting of study methodology, including information on subject characteristics, quality control, processing, and analysis methods to optimize development of nonsubjective metrics. Biomarker development offers a rich opportunity to significantly move forward clinical research and patient care in DED.

Overview

DED is an unmet medical need - a chronic pain syndrome associated with variable vision that affects quality of life, is common with advancing age, interferes with the comfortable use of contact lenses, and can diminish results of eye surgeries, such as cataract extraction, LASIK, and glaucoma procedures. It is a worldwide medical challenge with a prevalence rate ranging from 8% to 50%. Many clinicians and researchers across the globe are searching for better answers to understand the mechanisms related to the development and chronicity of DED. Though there have been many clinical trials for DED, few new treatments have emerged over the last decade. Biomarkers may provide the needed breakthrough to propel our understanding of DED to the next level and the potential to realize our goal of truly personalized medicine based on scientific evidence. Clinical trials and research on DED have suffered from the lack of validated biomarkers and less than objective and reproducible endpoints. Current work on biomarkers has provided the groundwork to move forward. This review highlights primarily ocular biomarkers that have been investigated for use in DED, discusses the methodologic outcomes in providing objective metrics for clinical research, and suggests recommendations for further work.

Analysis of Th17-associated cytokines and clinical correlations in patients with dry eye disease

We aimed to investigate the expressions of three Th17-associated cytokines, interleukin (IL)-17A, IL-6 and IL-23, in protein and mRNA levels and their correlations with ocular surface parameters in patients with dry eye disease (DED) through a small sample size case control study. A total of 45 female subjects were divided into Sjögren's syndrome (SS) DED group, non-Sjögren's syndrome (non-SS) DED group and control group. Ocular surface disease index (OSDI) was self-answered and clinical tests including tear-film breakup time (BUT), Schirmer I test, cornea fluorescein staining (CFS) were performed. The conjunctival mRNA expressions of these cytokines were investigated by real-time polymerase chain reaction (PCR) and the levels of protein in tears were measured by mutiplex bead analysis. The correlations between cytokines and ocular surface parameters were analyzed. Results show that the expressions of IL-17A and IL-6 in protein and mRNA levels were both significantly increased in the DED group (P<0.05), and also higher in SS group comparing to the non-SS group (P<0.05). Moreover, IL-17A and IL-6 correlated well with ocular surface parameters (all P<0.05, R values range from 0.5-0.8). Despite the expression of IL-23 was significantly increased in the DED group (P<0.05), there was no significant difference found between the expressions of IL-23 in SS group and non-SS group (P>0.05) and no correlation found between the IL-23 and any ocular surface parameter (P>0.05). These findings indicates that the three Th17-associated cytokines, IL-17A, IL-6 and IL-23, play roles in the pathogenesis of DED and the expressions of IL-17A and IL-6 in tears have potential to be diagnostic biomarkers for DED.

Enhanced Tearing by Electrical Stimulation of the Anterior Ethmoid Nerve

Purpose

Electrical neurostimulation enhances tear secretion, and can be applied to treatment of dry eye disease. Using a chronic implant, we evaluate the effects of stimulating the anterior ethmoid nerve on the aqueous, lipid, and protein content of secreted tears.

Methods

Neurostimulators were implanted beneath the nasal mucosa in 13 New Zealand white rabbits. Stimulations (2.3-2.8 mA pulses of 75-875 μs in duration repeated at 30-100 Hz for 3 minutes) were performed daily, for 3 weeks to measure changes in tear volume (Schirmer test), osmolarity (TearLab osmometer), lipid (Oil-Red-O staining), and protein (BCA assay, mass spectrometry).

Results

Stimulation of the anterior ethmoid nerve in the frequency range of 30 to 90 Hz increased tear volume by 92% to 133% (P ≤ 0.01). Modulating the treatment with 50% duty cycle (3 seconds of stimulation repeated every 6 seconds) increased tear secretion an additional 23% above continuous stimulation (P ≤ 0.01). Tear secretion returned to baseline levels within 7 minutes after stimulation ended. Tear film osmolarity decreased by 7 mOsmol/L, tear lipid increased by 24% to 36% and protein concentration increased by 48% (P ≤ 0.05). Relative abundance of the lacrimal gland proteins remained the same, while several serum and corneal proteins decreased with stimulation (P ≤ 0.05).

Conclusions

Electrical stimulation of the anterior ethmoid nerve increased aqueous tear volume, reduced tear osmolarity, added lipid, and increased the concentration of normal tear proteins. Human studies with an intranasal stimulator should verify these effects in patients with aqueous- and lipid-deficient forms of dry eye disease.

Effect of Oral Re-esterified Omega-3 Nutritional Supplementation on Dry Eyes

PURPOSE

To assess the effect of oral re-esterified omega-3 fatty acids on tear osmolarity, matrix metalloproteinase-9 (MMP-9), tear break-up time (TBUT), Ocular Surface Disease Index (OSDI), fluorescein corneal staining, Schirmer score, meibomian gland dysfunction (MGD) stage and omega-3 index in subjects with dry eyes and confirmed MGD.

METHODS

This was a multicenter, prospective, interventional, placebo-controlled, double-masked study. Subjects were randomized to receive 4 softgels containing a total of 1680 mg of eicosapentaenoic acid/560 mg of docosahexaenoic acid or a control of 3136 mg of linoleic acid, daily for 12 weeks. Subjects were measured at baseline, week 6, and week 12 for tear osmolarity, TBUT, OSDI, fluorescein corneal staining, and Schirmer test with anesthesia. MMP-9 testing and omega-3 index were done at baseline and at 12 weeks.

RESULTS

One hundred five subjects completed the study. They were randomized to omega-3 (n = 54) and control group (n = 51). Statistically significant reduction in tear osmolarity was observed in the omega-3 group versus control group at week 6 (-16.8 ± 2.6 vs. -9.0 ± 2.7 mOsm/L, P = 0.042) and week 12 (-19.4 ± 2.7 vs. -8.3 ± 2.8 mOsm/L, P = 0.004). At 12 weeks, a statistically significant increase in omega-3 index levels (P < 0.001) and TBUT (3.5 ± 0.5 s vs. 1.2 ± 0.5 s, P = 0.002) was also observed. Omega-3 group experienced a significant reduction in MMP-9 positivity versus control group (67.9% vs. 35.0%, P = 0.024) and OSDI scores decreased significantly in omega-3 (-17.0 ± 2.6) versus control group (-5.0 ± 2.7, P = 0.002).

CONCLUSIONS

Oral consumption of re-esterified omega-3 fatty acids is associated with statistically significant improvement in tear osmolarity, omega-3 index levels, TBUT, MMP-9, and OSDI symptom scores.

Paper-based microfluidic system for tear electrolyte analysis

The analysis of tear constituents at point-of-care settings has a potential for early diagnosis of ocular disorders such as dry eye disease, low-cost screening, and surveillance of at-risk subjects. However, current minimally-invasive rapid tear analysis systems for point-of-care settings have been limited to assessment of osmolarity or inflammatory markers and cannot differentiate between dry eye subclassifications. Here, we demonstrate a portable microfluidic system that allows quantitative analysis of electrolytes in the tear fluid that is suited for point-of-care settings. The microfluidic system consists of a capillary tube for sample collection, a reservoir for sample dilution, and a paper-based microfluidic device for electrolyte analysis. The sensing regions are functionalized with fluorescent crown ethers, o-acetanisidide, and seminaphtorhodafluor that are sensitive to mono- and divalent electrolytes, and their fluorescence outputs are measured with a smartphone readout device. The measured sensitivity values of Na⁺, K⁺, Ca²⁺ ions and pH in artificial tear fluid were matched with the known ion concentrations within the physiological range. The microfluidic system was tested with samples having different ionic concentrations, demonstrating the feasibility for the detection of early-stage dry eye, differential diagnosis of dry eye sub-types, and their severity staging.

The correlation between plasma osmolarity and tear osmolarity

PURPOSE

To the correlation between plasma osmolarity (Posm) and tear osmolarity (Tosm) in patients (54 patients, 88 eyes) who underwent cataract surgery was evaluated.

METHODS

Before cataract surgery, routine pre-operative biochemical tests were performed, and Posm was determined from blood samples. Also, Tosm was measured using the TearLab system, and objective signs including tear break-up time (BUT), fluorescein staining, lissamine green staining, and Schirmer's test were evaluated. Dry eye (DE) was diagnosed according to the Japanese criteria for DE.

RESULTS

Of the 88 eyes, 4 were diagnosed as definite DE, 70 as probable DE, and 14 as normal. Since the number of definite DE was small, the eyes were divided into two groups: normal group (n = 14) and DE group (n = 74), which included definite DE (n = 4) and probable DE (n = 70). There was no correlation between Posm and Tosm, though Posm (293.32 mOsm/L) was significantly higher than Tosm (288.48 mOsm/L; p < 0.001). There was no significant difference in Tosm between the normal group (288.29 mOsm/L) and the DE group (288.51 mOsm/L). No patients had a Tosm higher than 310 mOsm/L even in the DE group. Correlations between Posm/Tosm and each DE sign value were not found. Of 54 patients, 18 were diabetic. Posm was significantly higher in diabetic (295.78 mOsm/L) than in non-diabetic (292.36 mOsm/L; p = 0.014) patients, while there was no significant difference in Tosm between diabetic and non-diabetic patients.

CONCLUSIONS

The results suggest that Tosm is independent of Posm, and Tosm elevation in DE occurs by some local mechanisms.

Randomized, masked, in vitro comparison of three commercially available tear film osmometers

Purpose

The purpose of this study was to compare the precision and accuracy of commercially available tear film osmometers.

Methods

Contrived tear solution target values representing the physiological range of tear osmolarity (normal eyes 297 mOsm/L, moderately dry eyes 342 mOsm/L, and severe dry eyes 383 mOsm/L) were constructed using a mix of mono- and divalent electrolytes, metabolites, serum albumin, and pH balanced to 7.4. Solution values were randomized and masked from the investigators during testing. Osmometers (Wescor 5520 Vapro Pressure Osmometer: device A, TearLab Osmolarity System: device B, and i-Med Pharma i-Pen: device C) were calibrated according to manufacturer instructions. Each level was tested 64× on each osmometer across two sites. Accuracy was reported as a correlation coefficient against expected linear dilutions, precision was calculated as percent coefficient of variation.

Results

Device A reported a correlation with known solutions of r²=0.98, with averages of 305.6±4.0, 352.2±5.5, and 389.8±4.0 mOsm/L, and coefficient of variations (CVs) of 1.3%, 1.6%, and 1.0%, respectively. Device B reported an r²=0.96, with averages of 300.6±3.7, 341.4±7.9, and 376.8±5.1 mOsm/L, and CVs of 1.2%, 2.3%, and 1.4%, respectively. Device C reported an r²=0.03, with averages of 336.4±21.5, 342.0±20.7, and 345.7±22.0 mOsm/L, and CVs of 6.4%, 6.1%, and 6.4%, respectively.

Conclusion

In this randomized, masked, in vitro study, device A and device B had significantly better accuracy and precision in measuring osmolarity of contrived tear solutions of known target values compared to device C. Device C showed insufficient performance to accurately and precisely delineate osmolarity levels in the physiological range. Furthermore, in vivo studies would be required to compare performance in human subjects.

Epidemiology of dry eye disease in Africa: The sparse information, gaps and opportunities

Dry eye disease (DED) is an increasingly significant clinical problem in developing countries and/or emerging economies. Existing studies on DED conducted in these areas have largely reported on associations between DED and infectious disease (trachoma) and malnutrition (hypovitaminosis A), but current trends of industrialization, urbanization, and modernization in these areas could result in a shift to other forms of DED. Herein, we review the epidemiology of DED in these geographic areas, highlighting potential causes and risk factors of DED while presenting information on diagnostic tools and algorithms and insight into some treatment modalities of DED that could prove useful to clinicians and investigators in these regions.

Measurement variability of the TearLab Osmolarity System

PURPOSE

To independently assess the measurement variability of TearLab System in a clinical setting of one visit and to estimate the minimum number of measurements required for reliable readings of tear osmolarity.

METHODS

Ten consecutive osmolarity measurements were taken from both eyes by the same examiner at one visit for fourteen subjects. The ocular surface disease index symptoms questionnaire and tear film break up time were also performed. Group average cumulative mean and cumulative coefficient of variation were calculated to assess the TearLab measurement variation. Repeated application of Thompson's tau method was performed to identify the outliers in tear osmolarity readings for each eye. Results from both eyes were analysed separately.

RESULTS

Up to two randomly occurring outlying values in 10 consecutive measurements were found in 19 out of 28 measured eyes. No statistically significant differences between the left and right eye were found for the group mean and group standard deviation (paired t-test, p=0.099 and p=0.068, respectively), however the cumulative coefficient of variation indicated higher measurement group variability on one eye. Estimated cumulative coefficient of variation indicated the minimum of three consecutive acquisitions required for the measurement to be reliable.

CONCLUSIONS

TearLab Osmolarity System required at least three consecutive measurements to be taken in order to provide clinically reliable tear osmolarity readings. Also, taking the maximum osmolarity value for detecting dry eye disease should be viewed with caution since outlying readings of tear osmolarity frequently occur.

Effects of osmoprotective eye drops on tear osmolarity in contact lens wearers

OBJECTIVE

To evaluate the impact of osmoprotective eye drops on tear osmolarity and patient comfort, and to compare its efficacy with a commercially available lubricant in contact lens (CL) wearers.

DESIGN

Prospective, cross-sectional study.

PARTICIPANTS

Forty eyes of 20 first-time CL wearers were included.

METHODS

Tear osmolarity measurements using TearLab osmolarity system were performed in each eye of subjects at 8 am, and 2, 4, and 8 h after that on the first and second days, and at 12:00 on the third day and eighth days. On the second day and afterward, all eyes were fitted Purevision 2 (Bausch & Lomb) soft CLs. Subjects instilled Optive (Allergan) osmoprotective eye drops into their 1 eye (group 1) and Refresh tears (Allergan) eye drops into their other eyes (group 2) after 2 hours of CL wear on the third day and afterward. Ocular comfort with eye drops was also assessed.

RESULTS

There were no significant differences between the tear osmolarity measurements of the groups on the first day. On the second day, osmolarity significantly increased from baseline after 4 h of CL wear (p < 0.05) but returned to baseline after 8 h of CL wear (p > 0.05) in both groups. Tear osmolarity measurements of group 1 were significantly lower than those of group 2 on the third and eighth days (both p < 0.05). The mean comfort scores were significantly higher in group 1.

CONCLUSIONS

Tear osmolarity increases within the first hours of CL wear, and instillation of osmoprotective eye drops prevents this increment in patients wearing CLs.

In pursuit of objective dry eye screening clinical techniques

Dry eye is a multifactorial, progressive, and chronic disease of the tears and ocular surface. The disease is multi-factorial and has intermittent symptoms. Discomfort, visual disturbance, tear film instability with potential damage to the ocular surface, and increased tear film osmolarity are known associates.

Dry eye is a common clinical problem for eye-care providers worldwide and there is a large number of clinical investigative techniques for the evaluation of dry eye. Despite this, however, there is no globally accepted guideline for dry eye diagnosis and none of the available tests may hold the title of the ‘gold standard’. The majority of the techniques involved in the diagnosis of the disease, particularly for its early stages, has a large degree of subjectivity.

The purpose of this article is to review existing dry eye investigative techniques and to present a new objective dry eye screening technique based on optical coherence tomography.