Impact of time between collection and collection method on human tear fluid osmolarity

A Comprehensive Study on Tear Meniscus Height Inter-Eye Differences in Aqueous Deficient Dry Eye Diagnosis

(1) Background: Dry eye disease (DED) is a chronic ocular surface condition that requires precise diagnostic tools. The present study aimed to investigate the diagnostic potential of the absolute inter-eye difference (|OD-OS|) in tear meniscus height (TMH) for the detection of the presence of aqueous deficient dry eye (ADDE). (2) Methods: A sample of 260 participants with dry eye complaints underwent ocular surface examinations thorough diagnostic assessments based on the Tear Film and Ocular Surface Society guidelines (TFOS DEWS II). Participants were subsequently categorized as No ADDE and ADDE based on TMH. Statistical analyses to determine the optimal TMH|OD-OS| cut-off value in a randomly selected study group (200 participants) were performed, while a separate validation analysis of the cut-off value obtained in a random cross-validation group (60 participants) was also performed. (3) Results: The significant diagnostic capability of TMH|OD-OS| (area under the curve = 0.719 ± 0.036, p < 0.001) was found. The identified cut-off value of 0.033 mm demonstrated reliable specificity (77.6%) and moderate sensitivity (59.1%). Cross-validation confirmed the cut-off value's association with the TFOS DEWS II diagnostic criterion (Cramer's V = 0.354, p = 0.006). (4) Conclusions: The present study provides evidence for the diagnostic potential of TMH|OD-OS| in identifying ADDE. The identified cut-off value enhances the specificity and offers moderate sensitivity, providing an objective tool for clinical decision making.

Quality of vision and tear film osmolarity

SIGNIFICANCE

We evaluate the relationship between tear film osmolarity measurements and quality of vision in patients presenting for routine eye clinic appointments. We found that the hyperosmolar group (>316 mOsm/L) had a worse quality-of-vision score than the normal osmolarity group, with glare being the most problematic symptom.

PURPOSE

Quality of vision is a perception and measure of real-world vision, which is not measured routinely in a clinical setting. This study aimed to evaluate the relationship between tear film osmolarity measurements and quality of vision in patients presenting for routine eye clinic appointments.

METHODS

This was an observational nonrandomized study. The participants were placed in groups based on tear film osmolarity (normal, ≤316 mOsm/L; hyperosmolar, >316 mOsm/L; or a difference of >8 mOsm/L between each eye). Thirty-three participants were enrolled in the study, of whom 22 were deemed to have a hyperosmolar tear film. A 30-item questionnaire including 10 symptoms rated on scales of frequency, severity, and bothersomeness was administered to participants in both groups. The quality-of-vision score ranged from 25 to 100 points, with lower scores indicating better quality of vision.

RESULTS

The hyperosmolar group had a significantly worse quality-of-vision score than the normal osmolarity group across all three scales; mean differences for frequency, severity, and bothersomeness were 12.66 ± 9.75 (p=0.003), 9.44 ± 7.45 (p=0.003), and 11.90 ± 11.14 (p=0.008), respectively. Of the 10 symptoms that were included in the questionnaire, glare was the most problematic in the hyperosmolar group.

CONCLUSIONS

In this study, we demonstrated a significant relationship between tear film hyperosmolarity and quality of vision, as patients with hyperosmolar tear films had worse quality of vision.

Comparison of Two Topical Lubricants on the Corneal Surface Recovery and Patient Discomfort After Photorefractive Keratectomy

INTRODUCTION

This study aimed to compare the effect of two preservative-free (PF) artificial tears, one containing carboxymethylcellulose (CMC) (control group) vs another containing hyaluronic acid and hydroxypropyl guar (HA + HP-guar) (study group), on the healing of the corneal epithelium and the ocular discomfort after bilateral photorefractive keratectomy (PRK) surgery.

METHODS

A total of 68 patients that were scheduled to have PRK to correct myopia were randomized into two groups: 34 patients (68 eyes) in the study group and 34 patients (68 eyes) in the control group. Ocular examinations were performed on postoperative days 1, 4, 7, 30, and 90, evaluating the diameter of the de-epithelized cornea, the fluorescein staining using the Oxford scale, the tear film osmolarity and stability (tear breakup time), and the pain using visual analog scale (VAS).

RESULTS

On postoperative day 4, 97% of the study eyes vs 84.4% of the control eyes were completely re-epithelized (p = 0.01). Less ocular pain was observed on postoperative day 3 in the study group (5.0 (3.0-6.0) vs 6.0 (3.5-7.0), p = 0.03). No differences were observed beyond postoperative day 7 in the healing of the corneal epithelium, non-invasive Keratograph breakup time (NIKBUT), and the self-perceived ocular discomfort between the two groups.

CONCLUSION

The current study shows faster healing of the corneal epithelium and less ocular pain and discomfort in the first days after PRK with the use of topical lubricants containing HA + HP-guar compared to conventional CMC artificial tears, probably due to the different trophic effect of the aforementioned tears on the corneal epithelial cells.

TRIAL REGISTRATION

EudraCT No. 2020-003488-25.

Capability of the Inter-Eye Differences in Osmolarity, Break-Up Time and Corneal Staining on the Diagnostic of Dry Eye

PURPOSE

Inter-eye variability is a recognized characteristic of Dry Eye Disease (DED) and has been proposed as a diagnostic indicator in clinical practice. This study aimed to assess the diagnostic potential of the absolute difference between eyes in three key diagnostic tests recommended by the Tear Film and Ocular Surface Society Dry Eye Workshop II (TFOS DEWS II) Diagnostic Methodology report: tear film osmolarity, Fluorescein Break-Up Time (FBUT), and ocular surface staining.

METHODS

A total of 180 participants were included in a cross-sectional study. Before a dry eye examination, participants completed an online self-administered OSDI questionnaire. The TFOS DEWS II diagnostic criteria for DED assessment were used: along with OSDI, osmolarity, FBUT and ocular surface staining were measured in all participants in both eyes following standardized methodology. Based on signs and symptoms, participants were diagnosed as having No DED or DED. After diagnosis, the parameters were computed as the right and left eyes' absolute inter-eye difference (|OD-OS|).

RESULTS

Receiver Operating Characteristics analyses for computed parameters were used based on the previous diagnosis. ROC analyses showed that Osmolarity|OD-OS| have a diagnostic capability to differentiate between No DED and DED participants with a cut-off value of 9.5 mOsm/L (AUC = 0.745 ± 0.052, p < 0.003), whereas FBUT|OD-OS| and Corneal Stainning|OD-OS| have not (AUC, both p ≥ 0.160).

CONCLUSION

The present study found that the Osmolarity|OD-OS| parameter could be used as a diagnostic indicator for DED assessment, while the FBUT|OD-OS| and the Corneal Staining|OD-OS| parameters do not have this capability.

Efficacy of Interleukin-1β Inhibitor on Dry Eye Disease in Patients with Degenerative Arthritis

Purpose

To evaluate diacerein (interleukin-1β inhibitor) efficacy on ocular surface disease (OSD).

Patients and Methods

This prospective observational study included patients who received diacerein for osteoarthritis and had dry eye (DE). The primary outcome was corneal staining score. Secondary outcomes were ocular surface disease index (OSDI) score, tear breakup time (TBUT), tear osmolarity (Osm), Schirmer's test results, interleukin-1α (IL-1α), interleukin-1β (IL-1β), and interleukin-1 receptor antagonist (IL-1Ra) levels in tears. All measurements were done at baseline and 2-month follow-up visits. Linear mixed models were used to examine the effect of all parameters, and log-transformed models were used for IL-1α, IL-1β, and IL-1Ra analyses.

Results

Thirty-four patients (31 females and 3 males) were enrolled. The corneal staining score improved by 1.29 points (P=0.022, 95% confidence interval [95% CI] 0.19 to 2.40) after 2 months, and the OSDI score improved by 17.2 points (P<0.001, 95% CI 10.82 to 23.58) but TUBT decreased by 0.66 seconds (P=0.021, 95% CI 0.10 to 1.22). No significant differences were observed in the tear Osm and Schirmer's test. IL-1Ra demonstrated no statistical difference, IL-1α was significantly increased by 80% (P=0.260), and IL-1β was significantly decreased by 99.21% (P<0.001).

Conclusion

Diacerein can improve corneal staining and decrease IL-1β levels in tears, which reflects better DE symptoms. Diacerein may be a promising alternative treatment for patients with OSD and osteoarthritis.

Diagnostic Performance of the Tear Meniscus Osmolarity Measurement for Dry Eye Disease in Rheumatoid Arthritis Patients

BACKGROUND

The aim of our study was to evaluate the diagnostic capacity of the tear meniscus osmolarity measurement for dry eye disease (DED) in patients with rheumatoid arthritis (RA), using a portable osmometer based on electrical impedance and an integrated circuit technology (TearLab® (Escondido, CA, USA)).

METHODS

We included 101 RA patients, 81 patients with DED and 20 without DED (controls). We measured tear osmolarity and assessed other clinical diagnostic tests as suggested by the TFOS DEWS II composite reference standard diagnostic criteria for DED using Ocular Surface Disease Index (OSDI), Five-item Dry Eye Questionnaire (DEQ-5), fluorescein tear break-up time (F-TUBT), ocular surface staining (SICCA score), and other clinical parameters to classify DED subtypes. We analyzed the agreement between osmolarity and the TFOS DEWS II composite reference standard for DED diagnosis. We conducted receiver operating characteristic (ROC) curve analyses using the DED variable and its subtypes as dependent variables and the continuous variable for osmolarity or the inter-eye difference in osmolarity as independent variable. Sensitivity, specificity, and area under the curve for all potential cut-off points were obtained and reported from ROC curves.

RESULTS

We found that tear meniscus osmolarity had a low diagnostic capacity for DED (AUC = 0.57). Tear meniscus osmolarity measurement had a sensitivity of 35% and a specificity of 80% with a kappa level of agreement of 0.08 compared to the TFOS DEWS II composite reference standard. The low diagnostic capacity of the tear meniscus osmolarity was similar for aqueous-deficient DED and for evaporative DED, being only fair for severe DED with a 57% sensitivity and 80% specificity and a kappa level of agreement of 0.36.

CONCLUSIONS

Our findings suggest that in patients with RA, tear meniscus osmolarity measured by the TearLab® showed low sensitivity, low specificity, and limited agreement with the TFOS DEWS II composite reference standard for DED diagnosis.

Ocular Surface Allostasis-When Homeostasis Is Lost: Challenging Coping Potential, Stress Tolerance, and Resilience

The loss of ocular surface (OS) homeostasis characterizes the onset of dry eye disease. Resilience defines the ability to withstand this threat, reflecting the ability of the ocular surface to cope with and bounce back after challenging events. The coping capacity of the OS defines the ability to successfully manage cellular stress. Cellular stress, which is central to the outcome of the pathophysiology of dry eye disease, is characterized by intensity, continuity, and receptivity, which lead to the loss of homeostasis, resulting in a phase of autocatalytic dysregulation, an event that is not well-defined. To better define this event, here, we present a model providing a potential approach when homeostasis is challenged and the coping capacities have reached their limits, resulting in the stage of heterostasis, in which the dysregulated cellular stress mechanisms take over, leading to dry eye disease. The main feature of the proposed model is the concept that, prior to the initiation of the events leading to cellular stress, there is a period of intense activation of all available coping mechanisms preventing the imminent dysregulation of ocular surface homeostasis. When the remaining coping mechanisms and resilience potential have been maximally exploited and have, finally, been exceeded, there will be a transition to manifest disease with all the well-known signs and symptoms, with a shift to allostasis, reflecting the establishment of another state of balance. The intention of this review was to show that it is possibly the phase of heterostasis preceding the establishment of allostasis that offers a better chance for therapeutic intervention and optimized recovery. Once allostasis has been established, as a new steady-state of balance at a higher level of constant cell stress and inflammation, treatment may be far more difficult, and the potential for reversal is drastically decreased. Homeostasis, once lost, can possibly not be fully recovered. The processes established during heterostasis and allostasis require different approaches and treatments for their control, indicating that the current treatment options for homeostasis need to be adapted to a more-demanding situation. The loss of homeostasis necessarily implies the establishment of a new balance; here, we refer to such a state as allostasis.

How Can We Best Diagnose Severity Levels of Dry Eye Disease: Current Perspectives

Dry eye disease (DED) is a common ocular condition, but the diagnosis relative to other ocular conditions and the evaluation of severity of the condition has often been difficult. This challenge can be due to clinical signs and symptoms not always correlating with each other. An understanding of the various components which create the condition, as well as the diagnostic measures used to evaluate these components, is useful to the clinician working with DED patients. This review paper will discuss traditional diagnostic options, diagnostic imaging, and Advanced Point of Care testing capabilities to determine the severity level of dry eye disease more adequately.

The Significance of Inter-Eye Osmolarity Difference in Dry Eye Diagnostics

Purpose

The purpose of this study was to evaluate the diagnostic value of inter-eye osmolarity differences in relation to dry eye symptoms and other non-osmolar signs of dry eye disease.

Patients and Methods

One hundred ninety one participants who attended a larger interventional study of dry eye disease prior to and after cataract surgery were analyzed for dry eye disease (DED). Dry eye diagnostics were performed for all subjects according to the DEWS II criteria: tear osmolarity was collected from both eyes with the TearLab system, non-invasive Tear film break up time (NIKBUT) was obtained on the test eye with Keratograph and ocular surface staining (OSS) was evaluated using the Oxford schema. The Ocular Surface Disease Index (OSDI) questionnaire was used to assess symptoms. Inter-eye osmolarity greater than 8, which is considered as a sign of DED according to the TearLab user manual, was evaluated and compared with other non-osmolar signs of DED.

Results

The 191 subjects were divided into three groups according to osmolarity measurements. Sixty-five subjects had normal osmolarity (below 308 mOsmol/L in both eyes and less than 9 mOsmol/L difference between the eyes), 107 had high osmolarity (308 mOsmol/L or higher in one of the eyes) and 19 had an inter-eye difference >8 mOsmol/L or higher, with neither eye having osmolarity higher than 307 mOsmol/L. Signs and symptoms in this last group were not correlated with the high osmolarity group or the normal group, though they appeared more similar to the normal group.

Conclusion

The diagnostic value of inter-eye osmolarity difference in predicting symptoms or other non-osmolar signs of dry eyes appears weak. Our study suggests that the criterion of an inter-eye difference of 8 mOsmol/L is not a useful cut-off for diagnosing dry eyes based on osmolarity.

Intense Pulse Light Combined With Low-Level Light Therapy in Dry Eye Disease: A Systematic Review

OBJECTIVES

To evaluate the improvement in symptoms and signs associated with intense pulse light (IPL) combined with low-level light therapy (LLLT) in the treatment of dry eye disease (DED).

METHODS

A systematic review of full-length original studies reporting the effects of IPL combined with LLLT for DED in two databases, PubMed and Scopus, was performed according to the PRISMA statement. The quality assessment tool for case series studies from the National Heart, Lung, and Blood Institute was used to analyze the quality of the studies selected.

RESULTS

The search provided a total of 393 articles, of which six were included. Significant decreases in the Ocular Surface Disease Index (OSDI) score, meibomian gland dysfunction (MGD) score, MGD grade, and meiboscore and increases in tear film stability, lipid layer thickness, and loss area of the meibomian gland have been reported. Concerning tear volume, tear meniscus height, and Schirmer test remained unchanged. In relation to tear osmolarity and corneal fluorescein staining, contradictory outcomes were found.

CONCLUSIONS

Intense pulse light combined with LLLT for the treatment of dry eye improves OSDI, tear film stability, and meibomian gland function; thus, this treatment may be recommended for DED patients due to MGD.

Categorization of the Aqueous Deficient Dry Eye by a Cut-Off Criterion of TMH Measured with Tearscope

A decrease of the Tear Meniscus Height (TMH) has been proposed as a useful indicator for Aqueous Deficient Dry Eye (ADDE) categorization. The present study aimed to calculate a TMH cut-off criterion for the categorization or severity assessment of ADDE with the Tearscope. 200 participants with a previous Dry Eye Disease (DED) diagnosis according to TFOS DEWS-II criteria were recruited. TMH by slit-lamp illumination and Lipid Layer Pattern (LLP) with Tearscope were assessed to categorise the participants into the ADDE or the Evaporative Dry Eye (EDE) group. The ADDE group was also subdivided into Mild-moderate ADDE and Moderate-severe ADDE based on TMH with slit-lamp. Additionally, the TMH was measured by Tearscope (TMH-Tc). Receiver Operating Characteristics showed that the TMH-Tc have a diagnostic capability to differentiate between ADDE and EDE participants, and between Mild-moderate or Moderate-severe ADDE, with a cut-off value of 0.159 mm (AUC = 0.843 ± 0.035, p < 0.001; sensitivity: 86.4%; specificity: 75.4%) and 0.105 mm (AUC = 0.953 ± 0.025, p < 0.001; sensitivity: 98.1%; specificity: 80.0%), respectively. The present study proposed a cut-off criterion to differentiate between ADDE and EDE participants, or between ADDE severities through TMH assessed by Tearscope.

Diurnal variations of tear film osmolarity on the ocular surface

The measurement of tear film osmolarity has been suggested as a gold standard in the diagnosis of dry eye. Many tear film physiological variables oscillate during the day. This review summarises current clinical knowledge regarding diurnal osmolarity variation in the tear film. A critical analysis is presented in respect of of sample size and characteristics, differences in the diurnal osmolarity variation on healthy versus altered tear film conditions or environment, and time of day and number of measurements undertaken. A comparison of 21 studies was made for studies in which one of the main objectives was to analyse the variance of tear film osmolarity at different time-points in a day on human cohorts. Tear film osmolarity appeard to be somewhat influenced by the time of day in healthy subjects and patients with ocular surface disease, or altered by environmental conditions. Both healthy and non-physiological tear film cohorts showed variations in results depending on the study: no variations during the day or statistically different values at some point in the day. These differences could be in the middle of the day or between the beginning and the end of the day, with higher values in the morning than in the afternoon, or even the opposite situation. The possibility of diurnal variations in tear film osmolarity should be considered by the clinician since the time of day when the tear film measurements are made can be critical in making the right diagnosis. Future studies in the diurnal variation field may have to use a well-established range of measurement time-points and a larger group of healthy subjects and and subjects who have a tear film altered by pathological or environmental conditions.

Dry eye signs and symptoms in patients on aromatase inhibitor therapy

PURPOSE

The study aimed to test whether symptomatic dry eye in aromatase inhibitor (AI) patients is associated with the clinical features of evaporative dry eye.

METHODS

A cross-sectional, observational study of postmenopausal women treated with AI was conducted. Clinical information was gathered from their treating clinician. Ocular and treatment symptoms were assessed using validated questionnaires. Clinical assessments were performed to assess for dry eye. The primary outcome measure for this study was dry eye symptoms measured via questionnaire. The secondary outcome measures were clinical signs of dry eye and hormone levels.

RESULTS

A total of 25 women on AI were recruited. 64% of women reported symptoms of dry eye (ocular surface disease index ≥ 13). Higher tear osmolarity (323 vs 307 mOsm/L, p = 0.002) and increased meibomian gland dropout (4 vs 1, p = 0.002) were observed in patients with symptomatic dry eye when compared to asymptomatic patients. Multivariate logistic regression identified that longer duration of AI use and higher tear osmolarity increased the likelihood of a patient experiencing dry eye symptoms.

CONCLUSION

Our study found increased tear osmolarity and meibomian gland drop out in women on AI with symptomatic dry eye. Longer duration of AI therapy and higher tear osmolarity may increase the risk of developing dry eye.

Assessment of tear film osmolarity using the IPen® Vet osmometer in Pug and Shih-Tzu dogs with and without keratoconjunctivitis sicca

OBJECTIVE

To establish tear film osmolarity (TFO) values in Pugs and Shih-Tzus, with and without keratoconjunctivitis sicca (KCS).

ANIMALS STUDIED

A total of 82 adult dogs were evaluated.

PROCEDURE

The inclusion criteria for the healthy group was a Schirmer tear test (STT-1) ≥15 mm/min with no clinical signs of KCS, whereas those with KCS had clinical signs and a STT-1 ≤10 mm/min. All animals underwent complete ophthalmological evaluation prior to STT-1 and TFO. Student's t tests were used to compare STT-1 and TFO in KCS and healthy eyes as well as possible differences in TFO between breeds. In addition, a linear regression to model the relationship between the two variables (STT-1 and TFO) was performed. A P-value ≤ 0.05 was considered statistically significant.

RESULTS

STT-1 results were significantly lower (p = 0.0001) in the KCS group (4.46 ± 1.74) compared with the control group (18.80 ± 2.02). Mean TFO results were significantly higher in the KCS group (353.02 ± 16.58 mOsm/L) (p < 0.0001) compared with the control group (315.27 ± 6.15 mOsm/L). The formula Y = 365.059-2.625 * X significantly predicts (p < 0.001) the value of the variable Y (TFO mOsm/L) as a function of the variable X (STT-1 mm/min), with a coefficient of determination of 0.71.

CONCLUSIONS

The results revealed differences in TFO and STT-1 between KCS and healthy dogs. Additionally, STT-1 and TFO values were correlated with the aim to use STT-1 values to predict TFO values in brachycephalic breeds.

Prevalence of Tear Film Hyperosmolarity in 1150 patients presenting for refractive surgery assessment

PURPOSE

To present an analysis of tear film hyperosmolarity in a large, consecutive population and evaluate the correlation of ocular and systemic conditions with tear film osmolarity.

SETTING

Private practice Sydney, Australia.

DESIGN

Single-centre, retrospective, consecutive cohort.

METHOD

1404 patients (n=1357 standard, n=47 post-refractive) undergoing screening for laser refractive surgery from October 2017 to October 2020 were reviewed. Routine examination included tear film osmolarity (TFO) and Ocular Surface Disease Index questionnaire). TFO was conducted prior to further tests and patients refrained from topical eye drops minimum two hours before the appointment.

RESULTS

Mean highest TFO in the standard population was 299.12±11.94mOsm/L with 82.3% of eyes <308mOsm/L indicating normal tear film homeostasis. The mean inter-eye TFO difference was 8.17±8.60mOsm/L with 65.2% of eyes <=8mOsm/L. Mean highest TFO in the post-refractive subgroup was 299.72±11.00mOsm/L with a mean inter-eye difference of 9.02±6.92mOsm/L. Post-refractive surgery patients indicated higher mean OSDI values of 15.28±14.46 compared to the remainder of the population 9.69±10.56 (p=0.012). Significant correlation was demonstrated between TFO scores and OSDI normal classification in the standard population only (p=0.005, r=0.077). The use of contact lens correlated inversely with TFO and OSDI scores (p=0.000, r=-0.136 and p=0.000, r=-0.152 respectively).

CONCLUSION

Our study represents the largest available cohort of TFO scores in a standard population presenting for refractive surgery. We found that although the majority of patients can be expected to fall within normal ranges, a reasonable percentage will be diagnosed with tear hyperosmolarity and therefore at risk of dry eye disease.

Sex Hormones Related Ocular Dryness in Breast Cancer Women

Background: Dry eye syndrome (DES) is strictly connected to systemic and topical sex hormones. Breast cancer treatment, the subsequent hormonal therapy, the subsequent hyperandrogenism and the early sudden menopause, may be responsible for ocular surface system failure and its clinical manifestation as dry eye disease. This local dryness is part of the breast cancer iatrogenic dryness, which affects overall mucosal tissue in the fragile population of those with breast cancer. Methods: A literature review regarding the role of sex hormone changes and systemic hormonal replacement treatments (SHRT) in DES available on PubMed and Web of Science was made without any restriction of language. Results: Androgens exert their role on the ocular surface supporting meibomian gland function and exerting a pro-sebaceous effect. Estrogen seems to show a pro/inflammatory role on the ocular surface, while SHRT effects on dry eye are still not well defined, determining apparently contradictory consequences on the ocular surface homeostasis. The role of sex hormones on dry eye pathogenesis is most likely the result of a strict crosstalk between the protective androgens effects and the androgen-modulating effects of estrogens on the meibomian glands. Conclusions: Patients with a pathological or iatrogenic hormonal imbalance, such as in the case of breast cancer, should be assessed for dry eye disease, as well as systemic dryness, in order to restore their social and personal quality of life.

Evaluation of dry eye disease in children with blepharokeratoconjunctivitis

OBJECTIVE

To evaluate the symptoms and signs of dry eye disease (DED) in children diagnosed with blepharokeratoconjunctivitis (BKC).

DESIGN

Prospective case-controlled study PARTICIPANTS: Consecutive patients with BKC and normal controls.

METHODS

All participants underwent a comprehensive dry eye assessment including the Canadian Dry Eye Assessment (CDEA) questionnaire, tear film osmolarity test, Schirmer's test without anesthesia, slit lamp examination, tear film break-up time, corneal fluorescein staining (CFS), and lissamine green conjunctival staining (LGCS), according to the Sjögren's International Collaborative Clinical Alliance ocular staining score. For each test the result of the more severe eye was included in the statistical analysis.

RESULTS

Twenty-five patients were recruited-11 with BKC and 14 healthy controls. No difference in symptoms was found between children with BKC (CDEA score 6.1 ± 5.5) and normal controls (CDEA score 3.6 ± 3.2; p = 0.16). Children with BKC had significantly higher mean CFS (1.1 ± 1.6 vs 0.1 ± 0.4; p = 0.04) but similar mean LGCS (1.4 ± 1.8 vs 1.5 ± 2.1; p = 0.81) than normal controls. No statistically significant differences were observed in other tests between the 2 groups. CDEA scores were significantly correlated to CFS in normal controls (r = 0.59, p = 0.03), and approached significance in children with BKC (r = 0.56, p = 0.07).

CONCLUSIONS

The only test that can distinguish DED in patients with BKC from children without BKC is the CFS score. This should guide management and monitoring of this unique patient population with DED symptoms and signs.

Tear Osmolarity in the Diagnosis of Systemic Dehydration and Dry Eye Disease

Systemic dehydration due to inadequate water intake or excessive water loss, is common in the elderly and results in a high morbidity and significant mortality. Diagnosis is often overlooked and there is a need for a simple, bedside diagnostic test in at-risk populations. Body hydration is highly regulated with plasma osmolality (pOsm) being tightly controlled over a wide range of physiological conditions. By contrast, normal tear osmolarity (tOsm) is more variable since the tear film is exposed to evaporation from the open eye. While plasma hyperosmolality is a diagnostic feature of systemic dehydration, tear hyperosmolality, with other clinical features, is diagnostic of dry eye. Studies in young adults subjected to exercise and water-deprivation, have shown that tOsm may provide an index of pOsm, with the inference that it may provide a simple measure to diagnose systemic dehydration. However, since the prevalence of both dry eye and systemic dehydration increases with age, the finding of a raised tOsm in the elderly could imply the presence of either condition. This diagnostic difficulty can be overcome by measuring tear osmolality after a period of evaporative suppression (e.g., a 45 min period of lid closure) which drives tOsm osmolality down to a basal level, close to that of the pOsm. The arguments supporting the use of this basal tear osmolarity (BTO) in the diagnosis of systemic dehydration are reviewed here. Further studies are needed to confirm that the BTO can act as a surrogate for pOsm in both normally hydrated subjects and in patients with systemic dehydration and to determine the minimum period of lid closure required for a simple, "point-of-care" test.

Osmolality and pH of commercially available contact lens care solutions and eye drops

PURPOSE

The physical properties of contact lens care solutions and Eye Drops (ED) may affect initial comfort and dry eye symptomatology in contact lens wearers, although these properties are not always provided by manufacturers. The present study aimed to measure and compare the osmolality and pH of commercially available contact lens care solutions and ED.

METHODS

Forty-four solutions were tested (17 lens care solutions and 27 ED) and classified by the presence and/or combination of the viscosity/lubrication-enhancing ingredients. Solution osmolality was obtained with the Fiske 110 osmometer and pH was measured with a micro-pH 2000. Each measurement was taken ten times, following the manufacturer's instructions, while controlling for room temperature and humidity. Differences between the values of the physical properties of the solutions were analysed by type and viscosity/lubrication-enhancing agent subclassification.

RESULTS

Osmolality ranged from 192.6 ± 2.17 to 364.6 ± 2.88 mOsm/Kg, while pH ranged from 6.35 [6.35-6.26] to 7.99 [7.99-8.00]. A significant difference in the osmolality and pH values of contact lens care solutions and ED was found when classified by type or viscosity/lubrication-enhancing agent (ANOVA and Kruskal-Wallis respectively, both p < 0.001).

CONCLUSIONS

The physical properties of some contact lens care solutions and ED are not readily available. The osmolality and pH values of various commercially available lens care solutions and ED vary significantly both by type and viscosity/lubrication-enhancing ingredients.

Aquaporin 1 (AQP1) Expression in Healthy Dog Tears

Simple Summary

The characterisation of tear proteins is very important for scientists and clinicians, as it enhances their understanding of ocular physiological phenomena that sometimes evolve into diseases. Recently, ophthalmic research has been focused on aquaporins (AQPs), a family of water channel proteins that are largely ubiquitous in body tissues and are known for their role in water and small solute transport across cell membranes. Based on AQPs’ presumable role in the eye, the aim of the present study was to investigate the expression of aquaporin-1 (AQP1) by Western blot analysis in canine eye tears. To this end, we collected tears from both eyes of 15 healthy dogs by employing two tear collection methods: Schirmer tear strips (STS) and ophthalmic sponges (OS). Moreover, ocular parameters such as Schirmer tear test 1 (STT 1), intraocular pressure (IOP), and tear film break up time (BUT) were measured, and fluorescein and lissamine green staining were performed to uncover possible correlations among the aforementioned parameters. Our results showed that the expression of AQP1 in tears collected by both methods and expressed as multiple bands (measured by densitometry) was higher for the tears collected by OS than for those collected by STS. This work forms the basis of future studies aiming to understand and establish the involvement of AQPs in the production and secretion of tears.

Abstract

Aquaporins (AQPs) are a family of thirteen membrane proteins that play an essential role in the transport of fluids across the cell plasma membrane. Recently, the expression of AQPs in different ocular tissues and their involvement in the pathophysiology of eye diseases, have garnered attention. Considering that literature on AQP expression in the lacrimal glands and their secretion is scarce, we aimed to characterise AQP1 expression in the tears of healthy dogs using two tear collection methods (Schirmer tear strips (STS) and ophthalmic sponges (OS)). Fifteen healthy dogs, free of ophthalmic diseases, were included in the study. Tear collection was performed by using STS in one eye and OS in the other. After the extraction of proteins from the tears, the expression of AQP1 was analysed by Western blotting. AQP1 was expressed as a band of 28 kDa. In addition, differences were observed in the expression of AQP1 and in the correlation between tear volume and protein concentration, in tears collected by the two different methods. Our results suggest that AQP1 has a specific role in tear secretion; further research is required to assess its particular role in the function of the ocular surface in eye physiology and pathology.

Prospective randomized study to evaluate the efficacy and tolerability of Ectoin® containing Eye Spray (EES09) and comparison to the liposomal Eye Spray Tears Again® (TA) in the treatment of dry eye disease

PURPOSE

To subjectively and objectively evaluate the efficacy and tolerability of preservative-free Ectoin ® Eye Spray - Colloidal (EES09) and Tears Again ® Eye Spray (TA) in subjects with mild-moderate dry eye disease (DED), and to compare efficacy of these two eye sprays with each other.

METHODS

Thirty-six volunteers (average age 32.3 ± 16.1 years; 26 females) were successfully recruited for this prospective double-blind study with between-subject design and randomly divided into two groups (gender and age balanced): Group A received EES09 and Group B received TA during the treatment phase. Inclusioncriteria were a minimum age of 18 years, a score of 18.0 or higher on the OSDI questionnaire, and a non-invasive tear break up time (NIKBUT, Oculus Keratograph M5, Oculus, Germany) of no more than 10s in at least one eye. The objective variables NIKBUT, conjunctival redness, lipid layer and osmolarity (TearLab Cooperation, USA) were assessed at baseline, 10 min. after spray application and after a treatment phase of 10±3 days (3x applications daily). Symptoms, tolerance and handling were evaluated with the OSDI and VAS questionnaires.

RESULTS

A statistically significant increase in NIKBUT and improvement in DED symptoms were obtained for the overall group (mean NIKBUT 7.7 ± 1.7s vs. 11.6 ± 4.6s, p<0.001; mean OSDI score: 36.1 ± 12.7 vs. 20. 7± 12.7, p<0.001) during course of treatment. No statistically significant effect was established for the variables lipid layer (p = 0.406), conjunctival redness (p = 0.766) and osmolarity (p = 0.378). No statistically significant differences were observed between the groups, for any variable. The noninferioritycriterion for EES09 towards TA could be shown for the scores of the dry eye symptoms via VAS questionnaire and the variable NIKBUT.

CONCLUSIONS

A beneficial treatment effect was confirmed for both, symptoms of DED and the objective variable NIKBUT. Both eye sprays were rated favourably in view of perceived tolerability and handling of the spray bottle.

A Novel Gel-Forming Solution Based on PEG-DSPE/Solutol HS 15 Mixed Micelles and Gellan Gum for Ophthalmic Delivery of Curcumin

Curcumin (Cur) is a naturally hydrophobic polyphenol with potential pharmacological properties. However, the poor aqueous solubility and low bioavailability of curcumin limits its ocular administration. Thus, the aim of this study was to prepare a mixed micelle in situ gelling system of curcumin (Cur-MM-ISG) for ophthalmic drug delivery. The curcumin mixed micelles (Cur-MMs) were prepared via the solvent evaporation method, after which they were incorporated into gellan gum gels. Characterization tests showed that Cur-MMs were small in size and spherical in shape, with a low critical micelle concentration. Compared with free curcumin, Cur-MMs improved the solubility and stability of curcumin significantly. The ex vivo penetration study revealed that Cur-MMs could penetrate the rabbit cornea more efficiently than the free curcumin. After dispersing the micelles in the gellan gum solution at a ratio of 1:1 (v/v), a transparent Cur-MM-ISG with the characteristics of a pseudoplastic fluid was formed. No obvious irritations were observed in the rabbit eyes after ocular instillation of Cur-MM-ISG. Moreover, Cur-MM-ISG showed a longer retention time on the corneal surface when compared to Cur-MMs using the fluorescein sodium labeling method. These findings indicate that biocompatible Cur-MM-ISG has great potential in ophthalmic drug therapy.

Alteration of Blinking and Sex Differences During Physical Exercise Affect Tear Osmolarity

Physical exertion leads to the rise in tear osmolarity. However, previous studies have been conducted mostly on males and did not consider sex differences and the possible alteration in blinking during physical exercise. Sixteen women and 18 men aged 25.09 ± 1.70 were divided into equal groups with eyes open and shut. Participants performed 8-min medium-intensity exercise and 5-min intense exercise on a cycloergometer. Tear osmolarity (in mOsm/L) was evaluated before ( T0), after medium-intensity (T1) and intense exercise (T2). The blinking rate was assessed in a group with eyes open. Tear brake up time was measured in T0 and T1. With tear osmolarity measuring 305.72 ± 1.22 and 313.56 ± 1.90 for men and women, respectively, we observed significant differences in T1. In T2, tear osmolarity in men was 303.3 ± 1.28 vs. 310.87 ± 1.36 in women. The blinking rate decreased from 14.24 ± 2.54/min in T0 to 9.41 ± 2.83/min in T1. There was a statistically significant change in tear osmolarity in both groups, that is, in the group with eyes shut from 300.53 ± 1.37 in T0 to 308.06 ± 1.55 in T1 to 304.88 ± 1.54 in T2. In the group with eyes open, tear osmolarity increased from 300.29 ± 1.37 in T0 to 310.76 ± 1.55 in T1 and then dropped to 308.88 ± 1.54 in T2. Tear brake up time measured in T0 was 14.7 ± 1.43 vs. 13.53 ±1.48 in the open eyes condition. Due to physical exercise, short-term changes in tear osmolarity are partially caused by altered blinking. Sex differences in tear osmolarity in response to exertion may confirm the relationship between total body water and tear osmolarity.

Dry eye is matched by increased intrasubject variability in tear osmolarity as confirmed by machine learning approach

OBJECTIVE

Because of high variability, tear film osmolarity measures have been questioned in dry eye assessment. Understanding the origin of such variability would aid data interpretation. This study aims to evaluate osmolarity variability in a clinical setting.

MATERIAL AND METHODS

Twenty dry eyes and 20 control patients were evaluated. Three consecutive osmolarity measurements per eye at 5min intervals were obtained. Variability was represented by the difference between both extreme readings per eye. Machine learning techniques were used to quantify discrimination capacity of tear osmolarity for dry eye.

RESULTS

Mean osmolarities in the control and dry eye groups were 295.1±7.3mOsm/L and 300.6±11.2mOsm/L, respectively (P=.004). Osmolarity variabilities were 7.5±3.6mOsm/L and 16.7±11.9mOsm/L, for the control and dry eye groups, respectively (P<.001). Based on osmolarity, a logistic classifier showed an 85% classification accuracy.

CONCLUSIONS

In the clinical setting, both mean osmolarity and osmolarity variability in the dry eye group were significantly higher than in the control group. Machine learning techniques showed good classification accuracy. It is concluded that higher variability of tear osmolarity is a dry eye feature.

[Tear film analysis and evaluation of optical quality: A review of the literature (French translation of the article)]

Dry eye is a complex multifactorial disease of the ocular surface and tears. It is associated with ocular surface symptoms and is one of the most common causes for ophthalmologic consultation. Despite their frequent use in clinical practice, the usual tests to evaluate dry eye and ocular surface disease-history of symptoms, tear break-up time (TBUT), Meibomian gland evaluation, corneal fluorescein staining, Schirmer test-have shown low reproducibility and reliability. In addition, subjective symptoms are often weakly or poorly correlated with objective signs. Since the tear film is the first system through which light must pass, the optical quality of the eye is highly dependent on the homogeneity of the tear film. Various investigative methods have been developed to evaluate both the structural and functional quality of the tear film, such as corneal topography, interferometry, tear meniscus measurement, evaporation rate, tear osmolarity and even aberrometry. Some are easily accessible to clinicians, while others remain in the field of clinical research. All of these tests provide a better understanding of the pathophysiology of the tear film. This review hopes to provide an overview of the existing tests and their role in evaluating the significance of the tear film in visual function.

Reproducibility in measuring tear samples using a freezing point depression osmometer

BACKGROUND

Hyperosmolarity of tear fluid has been recognised as a common feature of all types of dry eye disease. This study was designed to assess the inter-session reproducibility of a freezing point depression osmometer (Fiske 110) as the most common and precise way of measuring osmolality, by using two different volumes of tear samples on healthy subjects, and to determine the possible applications of this device in tear film research and clinical practice.

METHODS

Measurements were made by using the Fiske 110 osmometer under two different tear sample volumes (4 μl and 2 μl). In both cases, samples were diluted in purified water to obtain the 20 μl required by the device to perform the measurement (1:4 and 1:9 dilutions, respectively). Inter-session reproducibility was determined in two groups of 40 healthy subjects, in two sessions, one week apart. In each group, one of the two different tear sample volumes was used to determine the reproducibility of each technique.

RESULTS

No significant differences were detected between the measurements obtained in the two sessions using the 4 μl (paired t-test, p = 0.772; mean difference ± SD = -0.85 ± 18.77 mOsm/L; 95 per cent limits of agreement [LoAs] = -37.64/+35.94) or the 2 μl volume sample (paired t-test, p = 0.054; mean difference ± SD = 9.27 ± 29.44 mOsm/L; 95 per cent LoAs = -48.43/+66.97).

CONCLUSIONS

Whereas both techniques show an acceptable inter-session reproducibility, the bias range with the present protocol was higher using the 2 μl tear sample volume than the 4 μl one. Therefore, it seems that the diluted 4 μl sample was the only dilution that could be acceptable for use in routine clinical practice for tear film analysis.

Tear film analysis and evaluation of optical quality: A review of the literature

Dry eye is a complex multifactorial disease of the ocular surface and tears. It is associated with ocular surface symptoms and is one of the most common causes for ophthalmologic consultation. Despite their frequent use in clinical practice, the usual tests to evaluate dry eye and ocular surface disease-history of symptoms, tear break-up time (TBUT), Meibomian gland evaluation, corneal fluorescein staining, Schirmer test-have shown low reproducibility and reliability. In addition, subjective symptoms are often weakly or poorly correlated with objective signs. Since the tear film is the first system through which light must pass, the optical quality of the eye is highly dependent on the homogeneity of the tear film. Various investigative methods have been developed to evaluate both the structural and functional quality of the tear film, such as corneal topography, interferometry, tear meniscus measurement, evaporation rate, tear osmolarity and even aberrometry. Some are easily accessible to clinicians, while others remain in the field of clinical research. All of these tests provide a better understanding of the pathophysiology of the tear film. This review hopes to provide an overview of the existing tests and their role in evaluating the significance of the tear film in visual function.

Variability of Tear Osmolarity Measurements With a Point-of-Care System in Healthy Subjects-Systematic Review

PURPOSE

To assess the variability of osmolarity measured by the point-of-care TearLab system in healthy eyes.

METHODS

A systematic review was performed by searching MEDLINE, Scopus, and the Web of Science Databases until November 2016 and checking reference lists of included articles and reviews. The requirements for inclusion were the availability of TearLab results in healthy subjects and a minimum study sample of 20 eyes. Two reviewers assessed articles against the inclusion criteria, extracted relevant data, and examined the methodological quality. We computed the weighted mean osmolarity using the study size as the weighting factor and calculated the rate of subjects with osmolarity values >308 mOsm/L, the Dry Eye Workshop Report 2017 (DEWS) cut-off value for dry eye disease (DED). We repeated the analysis after excluding reports with a possible conflict of interest or missing description of subject selection.

RESULTS

Searches retrieved 105 nonduplicate articles, and we included 33 studies investigating 1362 eyes of healthy participants who were asymptomatic and showed no clinical signs of DED. Sixty-three percent were female, and mean age was 37.3 years (range: 21.5-69.0 yr). Weighted mean osmolarity was 298 mOsm/L (95% confidence interval, 282-321 mOsm/L). The result of the subgroup analysis was similar. Overall, 386 of 1362 eyes (28.3%) fulfilled the DEWS's definition of DED (>308 mOsm/L).

CONCLUSIONS

There is a high variability of osmolarity measurements with the TearLab system. A substantial number of healthy subjects fulfill the DEWS's definition of DED. We propose interpreting the TearLab osmolarity results cautiously and in the context of other established methods.

Relation Between Dietary Essential Fatty Acid Intake and Dry Eye Disease and Meibomian Gland Dysfunction in Postmenopausal Women

PURPOSE

To evaluate the relationship between omega-3 (n-3) and omega-6 (n-6) fatty acids with dry eye disease (DED) and meibomian gland dysfunction (MGD).

DESIGN

Cross-sectional study.

METHODS

Postmenopausal women (n = 439) underwent a clinical evaluation and completed the Vio Food Frequency Questionnaire to estimate their dietary intake of n-3s and n-6s. Subjects were categorized into 2 binary classifications based on whether or not they had (1) DED and (2) MGD. Mean intake of dietary fatty acids was compared with 2-sample t tests. Univariate logistic regression models were used to estimate the odds ratios for each condition associated with each quintile of n-3s, n-6s, and n-6:n-3 ratios.

RESULTS

For DED vs non-DED, there were no significant differences in n-3 intake (1.95 ± 1.47 g vs 1.92 ± 1.24 g, P = .86), n-6 intake (15.58 ± 11.56 g vs 15.44 ± 10.61 g, P = .91), and n-6:n-3 (8.30 ± 2.57 vs 8.30 ± 2.57, P = .99). For MGD vs non-MGD, there were no significant differences in n-3 intake (1.87 ± 1.35 vs 1.96 ± 1.39, P = .61), n-6 intake (15.26 ± 11.85 vs 15.62 ± 10.93, P = .80), and n-6:n-3 (8.35 ± 2.94 vs 8.28 ± 2.42, P = .84). The odds ratios (OR) for DED did not differ significantly from 1.0 for n-3, n-6, or n-6:n-3. High n-3 consumption (OR = 0.22 [0.06–0.78]) and moderate n-6 consumption (OR = 0.37 [0.15–0.91]) were associated with a decreased frequency of MGD.

CONCLUSIONS

Dietary consumption of n-3s and n-6s showed no association with DED, but high n-3 consumption and moderate n-6 consumption were protective against MGD in this large sample of postmenopausal women.

Influence of Nasal Tear Osmolarity on Ocular Symptoms Related to Dry Eye Disease

PURPOSE

To investigate relationships between local tear osmolarity and tear film characteristics and dry eye disease (DED) symptoms.

DESIGN

Prospective, cross-sectional, observational study.

METHODS

Nasal and temporal tear osmolarity were measured in subjects with DED. The difference between nasal and temporal tears (OSM difference) was then calculated. Ocular symptoms were evaluated and tear break-up time (TBUT), corneal fluorescein staining score (CFSS), eyelid hyperemia, and tear production were measured. Correlations between DED symptoms and nasal tear osmolarity, temporal tear osmolarity, OSM difference, and tear film characteristics were evaluated using Pearson correlation analyses. Subjects were divided into 3 groups based on OSM difference: the temporal group had a temporal osmolarity > nasal osmolarity, the nasal group had a temporal osmolarity < nasal osmolarity, and the equal group had an OSM difference < 10 mOsm/L.

RESULTS

Forty-eight eyes of 48 subjects were included. Eleven eyes were in the temporal group, 17 eyes were in the equal group, and 20 eyes were in the nasal group. Temporal osmolarity, nasal osmolarity, and OSM difference were not correlated with TBUT, CFSS, lid hyperemia, or tear production. Nasal tear osmolarity was correlated with cold sensitivity frequency (r = 0.298, P = .040), foreign body sensation severity (r = 0.293, P = .043), and light sensitivity severity (r = 0.293, P = .043). Additionally, OSM difference was correlated with daily symptom frequency (r = 0.339, P = .019).

CONCLUSIONS

Nasal tear osmolarity and OSM difference play an important role in DED symptoms. Lid hyperemia, TBUT, CFSS, and tear secretion volume are not significantly affected by tear osmolarity. It is important to measure both nasal and temporal tear osmolarity when evaluating patients with DED.

Basal Tear Osmolarity as a metric to estimate body hydration and dry eye severity

The osmolarities of various bodily fluids, including tears, saliva and urine, have been used as indices of plasma osmolality, a measure of body hydration, while tear osmolarity is used routinely in dry eye diagnosis, the degree of tear hyperosmolarity providing an index of disease severity. Systemic dehydration, due to inadequate water intake or excessive water loss is common in the elderly population, has a high morbidity and may cause loss of life. Its diagnosis is often overlooked and there is a need to develop a simple, bedside test to detect dehydration in this population. We hypothesize that, in the absence of tear evaporation and with continued secretion, mixing and drainage of tears, tear osmolarity falls to a basal level that is closer to that of the plasma than that of a tear sample taken in open eye conditions. We term this value the Basal Tear Osmolarity (BTO) and propose that it may be measured in tear samples immediately after a period of evaporative suppression. This value will be particular to an individual and since plasma osmolarity is controlled within narrow limits, it is predicted that it will be stable and have a small variance. It is proposed that the BTO, measured immediately after a defined period of eye closure, can provide a new metric in the diagnosis of systemic dehydration and a yardstick against which to gauge the severity of dry eye disease.

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.

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.

Relation of accommodative microfluctuation with dry eye symptoms in short tear break-up time dry eye

Purpose

To investigate accommodative microfluctuations (AMFs) and visual function in short tear break-up time (BUT)-type dry eye (DE) and non-DE subjects.

Methods

This prospective comparative study included 48 volunteers with DE symptoms (mean age 34.8 ± 5.5 years, age range 25–42 years) and 73 without DE symptoms (mean age 30.6 ± 4.7 years, age range 25–42 years). The eyes were divided into two groups: (1) DE group with DE symptoms and BUT ≤ 5 s and (2) non-DE group without DE symptoms and BUT > 5 s. We excluded eyes with Schirmer score ≤ 5 mm and positive keratoconjunctival epithelial damage. Tear evaluation, AMF, and functional visual acuity (VA) examinations were performed. AMF parameters included total high-frequency component (HFC), HFC with low accommodation for the task of staring into the distance (HFC1), and HFC with high accommodation for deskwork (HFC2). Functional VA parameters included starting VA, functional VA, visual maintenance ratio, and blink frequency.

Results

A total of 33 and 34 eyes were categorized in the DE and non-DE groups, respectively. Mean blink frequency and HFC1 values were significantly higher in the DE group than they were in the non-DE group.

Conclusions

DEs with symptoms showed abnormal AMF and visual function, which may be associated with DE symptoms.

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.

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.

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.

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.

Dysfunctional tear syndrome: dry eye disease and associated tear film disorders - new strategies for diagnosis and treatment

Dysfunctional tear syndrome (DTS) is a common and complex condition affecting the ocular surface. The health and normal functioning of the ocular surface is dependent on a stable and sufficient tear film. Clinician awareness of conditions affecting the ocular surface has increased in recent years because of expanded research and the publication of diagnosis and treatment guidelines pertaining to disorders resulting in DTS, including the Delphi panel treatment recommendations for DTS (2006), the International Dry Eye Workshop (DEWS) (2007), the Meibomian Gland Dysfunction (MGD) Workshop (2011), and the updated Preferred Practice Pattern guidelines from the American Academy of Ophthalmology pertaining to dry eye and blepharitis (2013). Since the publication of the existing guidelines, new diagnostic techniques and treatment options that provide an opportunity for better management of patients have become available. Clinicians are now able to access a wealth of information that can help them obtain a differential diagnosis and treatment approach for patients presenting with DTS. This review provides a practical and directed approach to the diagnosis and treatment of patients with DTS, emphasizing treatment that is tailored to the specific disease subtype as well as the severity of the condition.

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.

Effect of tear osmolarity on repeatability of keratometry for cataract surgery planning

PURPOSE

To evaluate the effects of tear osmolarity on the repeatability of keratometry (K) measurements in patients presenting for cataract surgery.

SETTING

Three clinical practices.

DESIGN

Observational prospective nonrandomized study.

METHODS

Subjects were prospectively recruited based on tear osmolarity (Tearlab Osmolarity System); that is, osmolarity more than 316 mOsm/L in at least 1 eye (hyperosmolar) and osmolarity less than 308 mOsm/L in both eyes (normal). The baseline K value was measured, and a second measurement was taken on the same instrument (IOLMaster) within 3 weeks of the first. Variability in average K, calculated corneal astigmatism using vector analysis, and intraocular lens (IOL) sphere power calculations were compared between groups.

RESULTS

The hyperosmolar group (50 subjects) had a statistically significantly higher variability in the average K reading (P = .05) than the normal group (25 subjects) and a statistically significantly higher percentage of eyes with a 1.0 diopter (D) or greater difference in the measured corneal astigmatism (P = .02). A statistically significantly higher percentage of eyes in the hyperosmolar group had an IOL power difference of more than 0.5 D (P = .02). No statistically significant differences were present when the subjects were grouped by self-reported dry eye.

CONCLUSIONS

Significantly more variability in average K and anterior corneal astigmatism was observed in the hyperosmolar group, with significant resultant differences in IOL power calculations. Variability was not significantly different when subjects were grouped by self-reported dry eye. Measurement of tear osmolarity at the time of cataract surgery planning can effectively identify patients with a higher likelihood of high unexpected refractive error resulting from inaccurate keratometry.

FINANCIAL DISCLOSURE

Drs. Epitropoulos, Matossian, Berdy, and Malhotra received compensation from Tearlab for participating in the study. No author has a financial or proprietary interest in any material or method mentioned.

Tear film osmolarity and dry eye disease: a review of the literature

Objective

To evaluate the evidence in the peer-reviewed literature regarding the use of tear osmolarity as a physiological marker to diagnose, grade severity, and track therapeutic response in dry eye disease (DED). In addition, to review the evidence for the role of tear osmolarity in the pathophysiology of DED and ocular surface disease.

Methods

A literature review of all publications after the year 2000, which included the keywords “tear osmolarity”, was conducted. Relevant articles were graded according to quality of evidence and research, using the University of Michigan Practice Guideline and the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) rating systems. Articles were further categorized by the nature of any reported financial support and by the overall impression they provided related to tear osmolarity.

Results

A total of 164 articles were identified as relevant to the search criteria, although some were editorials, and some were written in a foreign language. Of the total, it was possible to grade 159, and an overall impression was generated for 163. A positive impression of tear osmolarity in DED diagnosis was evident in 72% (117/163) of all articles, with a neutral impression in a further 21% (35/163); 7% had a negative impression. The percentage of positive impressions appeared independent of the quality of research; 73% (38/52) of articles graded high/moderate quality supported the use of tear film osmolarity measurement in DED diagnosis. Impressions were also independent of the source of financial support, with 72% (75/104) of independent studies positive.

Conclusion

The literature broadly supports the use of tear film osmolarity as an objective numerical measure for diagnosing, grading severity, and managing treatment of DED.

Relationships among Tear Film Stability, Osmolarity, and Dryness Symptoms

PURPOSE

To examine the relationships among tear osmolarity, tear film stability, and several measures of dry eye (DE) symptoms in a multivariable analysis.

METHODS

A cross-sectional study was conducted with 137 subjects (68 non-contact lens [CL] wearers and 69 soft CL wearers) recruited from a university campus. Tear breakup time (TBUT) was measured noninvasively (NITBUT) and with fluorescein (FTBUT). Tear osmolarity was measured by an osmometer. Dry eye symptoms were assessed using the Dry Eye Flow Chart and several different questionnaires.

RESULTS

Subjects ranged in age from 18 to 67 years, with a mean of 28 years. Subjects had a mean (SD) osmolarity of 293 (10) mOsm/L, NITBUT of 14.1 (10.9) seconds, and FTBUT of 14.8 (12.6) seconds. Shorter NITBUT and FTBUT were significantly associated with female sex (p = 0.001 and p = 0.027, respectively) and Asian ethnicity (p = 0.030 and p = 0.004, respectively). There were no clinically significant relationships between tear osmolarity and FTBUT, NITBUT, or DE symptoms. Higher Dry Eye Flow Chart score (i.e., worse symptoms) was associated with older age (p < 0.001), female sex (p = 0.014), CL wear (p < 0.001), shorter NITBUT (p < 0.001), and shorter FTBUT (p = 0.028). The sensitivities and specificities for using clinical measurements to diagnose moderate to severe DE were as follows: osmolarity, 0.67 and 0.46, respectively; NITBUT, 0.72 and 0.52, respectively; and FTBUT, 0.68 and 0.57, respectively.

CONCLUSIONS

In a population of asymptomatic, mild and moderate DE patients, increased tear osmolarity was not significantly associated with reported symptom severity and frequency. Tear osmolarity, NITBUT, and FTBUT exhibited similar sensitivities and specificities when used to diagnose moderate to severe DE.