Tear Evaporation Rate Research Articles

Protecting Tear-Film Stability under Adverse Environmental Conditions Using a Mucomimetic with a Non-Newtonian Viscosity Agent.

Background and Objectives: Tamarind-seed polysaccharide (TSP) and hyaluronic acid (HA) have mucoadhesive properties that improve drug absorption and delay in drug elimination from the ocular surface. We aimed to evaluate TSP/HA-containing formulation for its efficiency in dry-eye symptoms induced by adverse environments and the interaction between mucomimic polymer and tear-film parameters. Materials and Methods: The participants were exposed to 5% relative humidity (RH) in a Controlled Environment Chamber (CEC) under constant room temperature (21 °C). Tear-film parameters were assessed at 40% RH and 5% RH. Rohto Dry Eye Relief drops were used in the two treatment modalities, protection (drops instilled before exposure to the dry environment) and relief (drops instilled after exposure to the dry environment). The HIRCAL grid, Servomed EP3 Evaporimeter, and Keeler's TearScope-Plus were used to screen for non-invasive tear break-up time (NITBUT), tear evaporation rate, and lipid-layer thickness (LLT) using protection and relief treatment methodology. Results: LLT was found to be significantly thinner at 5% RH compared with at 40% RH (p = 0.007). The median LLT dropped from 50-70 nm (grade 3) at 40% RH to 10-50 nm (grade 2) at 5% RH. TSP/HA eye drops significantly augment LLT in both treatment modalities, protection (p = 0.01) and relief (p = 0.004) at 5% RH. The mean evaporation rate doubled from 40.93 at 40% RH to 82.42 g/m2/h after exposure to 5% RH. In protection mode, the TSP/HA allowed the average evaporation rate to be much lower than when no TSP/HA was used at 5% RH (p < 0.008). No alteration in evaporation rate was recorded when the TSP/HA drop was used after exposure (relief). The mean NITBUT was reduced from 13 s in normal conditions to 6 s in the dry environment. Instillation of TSP/HA eye drops resulted in significant improvement (p = 0.006) in tear stability, where the NITBUT increased to 8 s in both protection (before exposure) and relief (after exposure) (p = 0.001). Although improved, these values were still significantly lower than NITBUT observed at 40% RH. Conclusions: Significant protection of tear-film parameters was recorded post instillation of TSP/HA eye drop under a desiccating environment. Both treatment methods (protection and relief) were shown to be effective. The presence of TSP/HA enhances the effectiveness of teardrops in protecting the tear-film parameters when exposed to adverse environments.

Evaluation of Therapeutic Capability of Emustil Drops against Tear Film Complications under Dry Environmental Conditions in Healthy Individuals.

Background and Objectives: Dry eye disease (DED) is a multifactorial ailment of the tears and ocular surface. The purpose of this study was to assess the tear film physiology under controlled dry environmental conditions and compare the efficacy of oil-in-water emulsion drops on tear film parameters in protection and relief treatment modalities under low-humidity conditions. Emustil eye drops were used after exposure to a low-humidity environment in the relief method, whereas, in the protection method, the drops were applied before exposure to low humidity. Materials and Methods: 12 normal male subjects (mean age 34.0 ± 7.0 years) were exposed to ultra-dry environmental conditions. A number of tear film measurements were carried out under desiccating environmental conditions in a controlled environment chamber (CEC), where the chamber temperature sat at 21 °C with a relative humidity (RH) of 5%. Keeler's TearScope Plus and an HIRCAL grid were used to assess the tear break-up time and lipid layer thickness (LLT), and the evaporation rate was evaluated using a Servomed EP3 Evaporimeter. Results: LLT measurements showed that the dry environment affected LLT significantly (p = 0.031). The median grade of LLT dropped from grade 3 (50-70 nm) at 40% RH to grade 2 (13-50 nm) at 5% RH. A significant increase in LLT was seen after both modes of treatment, with a median LLT grade of 3 when the Emustil was used for both protection (p = 0.004) and relief (p = 0.016). The mean tear evaporation rate in normal environmental conditions (40%) was 40.46 ± 11.80 g/m2/h (0.11 µL/min) and increased sharply to 83.77 ± 20.37 g/m2/h (0.25 µL/min) after exposure to the dry environment. A minimal decrease in tear film evaporation rate was seen in relief; however, statistical tests showed that the decrease in tear film evaporation rate was not significant. Mean NITBUT dropped from 13.6 s at 40% RH to 6.6 s at 5% RH (p = 0.002). All NITBUT measurements at 5% RH (with or without the instillation of Emustil) were significantly lower than those at 40%. The instillation of Emustil at 5% RH resulted in a significant improvement in NITBUT for protection (p = 0.016) but this was not the case for relief (p = 0.0.56). Conclusions: A control environmental chamber (CEC) enables the analysis of tear film parameters comparable to those found in dry eye patients. This enables us to examine the capability of oil in emulsion drops to manage tear film disruption in healthy individuals. This study suggests that using Emustil oil-in-water emulsion before exposure to a dry environment should be advocated for people who work in dry environments.

Tear Fluid Biomarkers and Quality of Life in People with Type 2 Diabetes and Dry Eye Disease.

Dry eye disease (DED) can be extremely distressing and is common in type 2 diabetes (T2D). To investigate potential biomarkers of DED in T2D, panels of proteins in tears, alongside clinical signs and symptoms of DED, were assessed. Patients were classified into four groups: T2D + DED (n = 47), T2D-only (n = 41), DED-only (n = 17) and healthy controls (n = 17). All patients underwent the Ocular Surface Disease Index (OSDI) and Dry Eye-Related Quality of Life (DEQS) questionnaires, tear evaporation rate (TER), fluorescein tear break-up time (fTBUT), corneal fluorescein staining (CFS) and Schirmer 1 test assessments. Six metabolic proteins and 14 inflammatory cytokines were analyzed with multiplex bead analysis. Interleukin (IL)-6 and IL-8 concentrations in tears were significantly higher in the T2D + DED group, and these biomarkers were positively correlated with CFS. In addition, tear IL-6 was negatively correlated with fTBUT in the T2D + DED group. Clinical signs of DED in the T2D + DED group were similar to the DED-only group. The T2D + DED group had more patients with moderate and severe DED (versus the DED-only group), suggesting a different pathogenesis for DED in T2D versus DED-only. Therefore, IL-6 and IL-8 could potentially be diagnostic biomarkers of DED in T2D.

Evaluation of different treatment modalities on the efficacy of hydroxypropyl Guar (HP-Guar) formulation on tear film stability (TFS) in subjects exposed to adverse environmental conditions

The study aimed to assess the efficacy of hydroxypropyl guar (HP) formulation (Systane) to protect tear film parameters under desiccating environment using protection and relief treatment modalities. The subjects were exposed to adverse environmental conditions using a Controlled Environment Chamber (CEC) where the relative humidity (RH) was 5% and the ambient temperature was 21 °C and screened for Tear break-up time (TBUT), Tear film evaporation rate (TFER) and lipid layer thickness (LLT) using the HIRCAL grid, Servomed EP3 Evaporimeter and Keeler’s TearScope-Plus respectively. Significant improvement in LLT was noticed in the protection modality. The mean tear film evaporation rate doubled after exposure to the humidity of 5% to a value of 105.37 g/m2/h (0.29 µl/min). All subjects displayed a significant reduction in non-invasive tear break-up time (NITBUT) with a mean NITBUT of 7.7 s after exposure to a desiccating environment for 15 min. A significant increase in NITBUT after the instillation of the drops was recorded in both methods. The results obtained from this study showed that a solution containing HP-Guar significantly improves tear film parameters under a desiccating environment. Apart from the tear evaporation rate, all tear parameters showed improvement after the use of HP-Guar eye drops. It is evident that tear film parameters respond differently to the management modalities and using CEC has the potential to provide researchers with a readily available method to evaluate the efficiency of tear supplementation.

Effect of wearing a face mask on microclimate around the eyes and the tear film

Eye discomfort is a major complaint reported in indoor spaces and has been suggested to be exacerbated by environmental conditions such as low humidity and high air velocity. Wearing face masks, which has become essential in our daily lives during the COVID-19 pandemic, can also cause eye discomfort by affecting the microclimate around the eyes. We conducted a pilot study to evaluate the effect of wearing masks on eye discomfort by measuring the physical environment around the eyes and short-term physiological and psychological responses and comparing them with and without surgical face masks. The results showed that when the participant wore a mask, exhaled air flowed out through the gap at the top edge of the mask, resulting in a higher air velocity and absolute humidity around the eyes than when the mask was not worn. No significant differences were found in subjective discomfort, tear-film stability, ocular surface temperature or blink frequency. However, the tear evaporation rate, estimated based on physical measurements, was greater when wearing a mask than when not wearing it. This study revealed that wearing face masks can negatively affect the environment around the eyes in terms of tear-film health.

Features and influences on the normal tear evaporation rate.

Tear evaporation is a normal physiological phenomenon that has an important role in regulating blink activity and tear production. An altered tear evaporation rate (TER) is a defining characteristic of evaporative dry eye disease (DED), and the measurement of tear evaporation is a useful clinical test for diagnosis. Reported values for a normal TER cover a broad range, which may be due to the influence of ocular, environmental, and systemic factors. For improved disease diagnosis, a fuller understanding of the normal TER range is essential. This paper reports on a literature review of the current knowledge of these normal influences on TER.

Diurnal variation on tear stability and correlation with tear cytokine concentration

PurposeTo investigate the effect of time of day on tear evaporation rate (TER) and tear break-up time, and its possible relationship with the concentration of inflammatory tear molecules (cytokines) in healthy subjects. MethodsParticipants with healthy ocular surfaces attended 3 visits, including the screening visit (V0), the 2nd visit (V1) and the 3rd visit (V2). There were 7-day intervals between visits. Participants with Dry Eye Disease (DED) were excluded by using appropriate clinical tests during V0. Clinical evaluation (TER and Non-Invasive Tear Break-Up Time (NITBUT)) and tear collection were performed during V1 and V2, between 9 and 10AM and 3-4PM. The relative humidity and temperature of the examination room were also measured. The tear fluid concentrations of 15 cytokines were measured by multiplex bead analysis. ResultsSeven men and 10 women (mean age ± S.D; 25.1 ± 6.63 years old) participated in the study. There were no differences in neither the TER and NITBUT outcomes, nor humidity and temperature among times or visits. Eleven out of the 15 cytokines measured were detectable in tear fluids in > 50% of the participants. In the tear levels, no significant (p > 0.05) inter- and/or intra-day differences were detected for EGF, fractalkine, IL-1RA, IL-1β and IP-10. However, significant inter-day differences were found in the tear levels of IL-10 (p = 0.027), IFN-γ (p = 0.035) and TNF-α(p = 0.04) and intra-day differences in the tear levels of IL-8/CXCL8 (p = 0.034) and MCP-1 (p = 0.002). A significant correlation between TER and IL1-β, IL-2, and Fractalkine (p = 0.03, p = 0.03 and p = 0.046, respectively) was found at V1. ConclusionsNITBUT and TER values had no significant variability over the course of a day (AM versus PM), or on different days in healthy participants when humidity and temperature were constant. However, some tear molecule levels did show inter- and intra-day variability, having an inconsistent and moderate correlation with TER diurnal variation.

Ocular Surface Temperature in DED under Natural Non-Controlled Blinking Conditions

Infrared (IR) thermography is a tool to non-invasively assess the tear film temperature. The aim was to analyze ocular surface temperature (OST) variations in dry eye disease (DED) and control eyes under natural non-controlled blinking conditions. Imaging was performed with a thermal camera (FLIR Systems Inc.) at 30 Hz framerate in 79 participants (39 DED (62.5% women, average age 48 ± 20 years) and 40 control (46.2 % women, average age 38 ± 13 years)) using non-contact IR thermography camera. Data acquisitions were performed in natural blinking conditions for 40 s. IR images were analyzed using a custom algorithm that calculates the OST indexes: mean OST, OST at the start and at the end, minimum and maximum OST, and tear evaporation rate (TER). No significant differences were found between groups in any thermal parameter analyzed (paired comparisons t-test, p &gt; 0.05). In conclusion, the findings of this study did not reveal significant differences between DED and control eyes under natural non-controlled blinking conditions. However, the presence of clinical signs in the control group may affect the results, highlighting the role of DED diagnosis criteria.

Evaluation of Tear Evaporation Rate in Subjects with a High Body Mass Index.

This study evaluated the tear evaporation rate (TER) in subjects with a high body mass index (BMI) and tested the correlation between BMI and dry eye. Thirty male subjects aged 18 - 38 years (26.4 ± 4.0years) with a high BMI (26.4 - 47.0 kg/m2) were enrolled in the study. In addition, a control group of 30 males aged 20 - 36 years (24.0 ± 3.6 years) with a normal BMI (< 25 kg/m2) participated in the study for comparison. Each subject completed the ocular surface disease index (OSDI), followed by the TER measurement using a handheld VapoMeter. Significant differences (Wilcoxon test; p = 0.002 and 0.001) were found between the median scores of the OSDI (10.3 [3.7] vs. 5.9 [7.2]) and TER (35.5 [13.1] vs. 15.5 [12.8] g/m2 h) in the study and control groups, respectively. The OSDI indicated dry eye in 60.0% of subjects in the study group (n = 18). The TER measurements showed that 76.7% of subjects in the study group (n = 23) had dry eyes. A medium correlation (r = 0.569; p = 0.001) was found between the OSDI scores and TER measurements. The means of the tear evaporation rate and the ocular surface disease index scores are significantly higher in subjects with a high BMI compared with the control group. Therefore, a high BMI is considered a risk factor for dry eye. The measurement of the tear evaporation rate using a handheld VapoMeter is a simple and rapid method to detect dry eyes in combination with other tools.

Comparative study of tear film evaluation among healthy pregnant women and gestational diabetes: a cross-sectional study

Background: Diabetes mellitus (DM) is one of the risk factors for dry eye. This study aimed to estimate the characteristics of tear film by measuring the tear secretion, tear evaporation rate, conjunctival impression cytology and also ocular surface disease index (OSDI) scoring through a questionnaire for gestational diabetes mellitus (GDM) and healthy pregnant women (HPW).Methods: Total of 40 subjects which included 20 subjects who were HPW in group-1 and 20 subjects who were GDM in group-2. After examining their ocular status, the subjects were initially administered with OSDI questionnaire followed by dry eye evaluation procedures such as non-invasive tear breakup time (NIBUT), Schirmer’s 1 and 2, tear film break up time (TBUT) and conjunctival impression cytology (CIC).Results: The gathered data was checked for normality. Mean and standard deviation was compiled for each parameter for their respective groups. A statistical comparison with independent t test was performed between the groups which compared OSDI scores, NIBUT, Schirmer’s 1 and 2, TBUT and CIC for both HPW and GDM group women. Statistically significant difference (p&lt;0.01) was observed with OSDI scores, Schirmer's test 2, TBUT and NIBUT whereas Schirmer's test 1 and CIC were not statistically significant (p&gt;0.01). OSDI scores represented mild symptoms for GDM women.Conclusions: Tear film of GDM women was affected more than HPW suggesting evaporative dry eye. Assessing tear film as a part of routine eye examination for women with GDM is essential to avoid the occurrence of complications due to tear film abnormalities.

Measurements of Tear Evaporation Rate in Subjects with Refractive Errors Using a Portable Evaporimeter.

Dry eye symptoms are associated with refractive errors. We aimed to measure the tear evaporation rate (TER) in subjects with refractive errors (RE) using a portable evaporimeter. This nonrandomized, case–control, and observational study included 75 subjects, including 25 subjects aged 18–38 years (28.8 ± 6.8 years) with myopia (−0.75 to −3.75 D) and 25 subjects aged 18–39 years (27.7 ± 5.5 years) with hyperopia (+0.50 to +3.75 D). In addition, a control group of 25 subjects with emmetropic eyes aged 20–30 years (23.6 ± 2.6 years) was recruited. The ocular surface disease index (OSDI) was completed, followed by the TER measurements using a portable evaporimeter. The OSDI score and TER measurements showed dry eye symptoms in 36% and 48% of myopic subjects, respectively. For hyperopic participants, dry eye was observed in 24% and 56% of the subjects based on the OSDI and TER scores, respectively. Significant differences (Mann-Whitney U test; p < 0.001) were found among the OSDI and TER scores recorded within the study (myopic and hyperopic subjects) and control groups. Significant strong positive correlations were detected between the OSDI and TER scores in both myopic (p = 0.004; r = 0.559) and hyperopic (p = 0.001; r = 0.619) subjects. The TER scores were significantly higher in subjects with RE (myopic and hyperopic) as compared with individuals with normal eyes.

Assessment of Meibomian Gland (MD) Impairment Among Seasonal Allergic Conjunctivitis (SAC) Patients.

BackgroundAllergic conjunctivitis, one of the frequently occurring ocular surface diseases, can cause mucus discharge, itchy sensation, conjunctival hyperemia, and papillary formation. Seasonal allergic conjunctivitis (SAC) is associated with xerophthalmia and instability of tear film. Meibomian gland (MG) can secrete lipids to avoid xerophthalmia. However, there have been few reports on MG morphological alterations of SAC patients. This study aimed to examine the morphological alterations of MG among SAC patients.Material/MethodsOur study included 89 eyes from 89 patients with SAC and 112 eyes of healthy volunteers. The symptoms were assessed by ocular surface disease index (OSDI) questionnaire. Then, the tests shown below were carried out, including tear evaporation rate from the ocular surface (TEROS), slit-lamp examination, break-up time (BUT) of tear film, Schirmer test I, vital staining, meibography, and meibum expression grading. MG was examined with laser scanning confocal microscopy (LSCM).ResultsRelative to the control group, the OSDI was significantly higher in the SAC group. TEROS values, BUT, vital staining, MG expression, MG distortion rates, and MG dropout grades were significantly worse in the SAC group compared with the control group. As suggested by LSCM, SAC patients had markedly worse averages of parameters compared with controls.ConclusionsThe patients with SAC have more significant morphological and cytological changes in the MG. The Keratograph 5M system and LSCM are effective methods for evaluating MG status and ocular surface diseases.

Evaluation of Tear Evaporation Rate in Patients with Diabetes Using a Hand-Held Evaporimeter.

Diabetes is a very common disease and is considered a risk factor for many diseases such as dry eye. The aim of the current work was to evaluate the tear evaporation rate (TER) in patients with diabetes using a hand-held evaporimeter. This observational, case–control and non-randomized study included 30 male patients with diabetes (17 controlled and 13 uncontrolled) with a mean ± standard deviation (SD) of 33.1 ± 7.9 years. An age-matched (18–43 years; 32.2 ± 6.5 years) control group consisting of 30 male subjects was also enrolled for comparison. Subjects with thyroid gland disorder, a high body mass index, high blood cholesterol, or thalassemia, contact lens wearers, and smokers were excluded. The TER was measured after the completion of the ocular surface disease index (OSDI) by each participant. The OSDI and TER median scores were significantly (Wilcoxon test, p < 0.05) higher in patients with diabetes (median (interquartile range; IQR) = 12.0 (8.3) and 46.4 (36.7) g/m2h, respectively) compared to the subjects within the control group (5.6 (7.0) and 15.1 (11.9) g/m2h, respectively). The median scores for the OSDI and TER measurements were significantly (Wilcoxon test, p < 0.05) higher among uncontrolled diabetes patients (13.0 (11.5) and 53.4 (14.2) g/m2h, respectively) compared to those obtained for patients with controlled diabetes (11.0 (8.0) and 27.3 (32.6) g/m2h, respectively). The tear evaporation rate in patients with diabetes was significantly higher compared to those obtained in subjects without diabetes. Uncontrolled diabetes patients have a higher tear evaporation rate compared to controlled diabetes patients. Therefore, diabetes can lead to eye dryness, since these patients possibly suffer excessive tear evaporation.

Assessment of the Efficiency of HP-Guar and hyaluronic Acid Tear Supplements to Control Tear Film Evaporation Rate in Dry Eye Subjects

Background: The most common factor that could lead to dryness is the accelerated tear evaporation rate. Controlling the tear evaporation rate is increasingly used as a method to control dry eye complications. The present study explores the effects of different tear supplements formulations on tear film evaporation rate. Objective: This study aimed to evaluate the short-term effects of Systane ULTRA and Artelac Advanced eye drops on the tear film evaporation rate. Methods: Fifteen male dry eye subjects were enrolled in the current study. Tear film parameters were observed at several time points post installation (10, 20, 30, and 60 min). The tear film parameters observed in the current study were tear evaporation rate, noninvasive breakup time (NITBUT) and tear meniscus height (TMH). Two visits were required to conduct this study. One visit was conducted to assess the physiological tear film parameters with the use of Systane® ULTRA eye drop. The other visit was conducted to assess tear film parameters with the use of Artelac Advanced eye drop. Results: The mean tear evaporation rate at baseline was 52.58 ± 23.24 g/m2 h. A box plot of tear evaporation showed a reduction in tear film evaporation rate after instillation of Systane eye drop. A drop in tear film evaporation rate of 14% was observed at 20 and 60 min time point after instillation of Systane ULTRA eye drop. A significant increase in NITBUT was found after instillation of Systane ULTRA (P = 0.01) and Artelac Advanced (P = 0.02). Conclusion: The current study indicates a significant improvement in the tear film parameters using both HP-Guar and hyaluronic acid formulations. However, it was apparent that the use of HP-Guar was superior to hyaluronic acid in controlling the tear evaporation rate in dry eye subjects.

Meibomian Gland Dysfunction Causing Dry Eye Syndrome in Computer Users

Background: Meibomian glands are follicular glands that release lipid that shapes the tear film's superficial layer. A persistent, extensive terminal duct blockage and descriptive alterations in the secretory output indicate meibomian gland dysfunction. Digital eye strain is characterized by changes in ocular surface integrity, tear film function, blinking patterns, accommodation disorders, differences in fixation, dryness, weariness and discomfort while using digital gadgets. The COVID 19 pandemic have resulted in almost everything to be on digital platform.&#x0D; Objective: To conclude after reviewing various studies (between Jan 2016- Dec 2020) which were focused on how digital eye strain adversely affects the function of meibomian glands and adds to symptoms of dry eye in computer users.&#x0D; Study Design: Narrative review article&#x0D; Methodology: Various articles were reviewed which got published in between 2014-2020 in indexed journals. Meibomian gland dysfunction significantly affects the factors such as blink rate, tear break-up time (TBUT), tear evaporation rate, tear film composition as well as corneal staining, we will find its significant effect and relation to digital eye strain.&#x0D; Expected Results: Based on previous articles.&#x0D; Results: Digital eye strain significantly affects the function of meibomian gland, thus results in altered and poor tear film that finally results in dryness of eyes.&#x0D; Conclusion: Eyes with meibomian gland dysfunction, develop changes such as, reduced blink rate, shorter tear breakup time; altered tear film composition and disturbed ocular surface which adds on to symptoms of dry eye especially in chronic computer users.

Assessment of a Cationic Emulsion to Control the Tear Film Evaporation Rate.

PurposeTo investigate the effect of a single application of cationic emulsion in controlling tear film evaporation and improving tear quality and quantity.Materials a MethodsTwenty male subjects diagnosed with DE were enrolled in the study with an average age of 45.8 ± 6.37 years. The tear film parameters were observed at several time points post-instillation of the cationic emulsion (10, 20, 30, and 60 min). The tear evaporation rate (TER) was measured with a VapoMeter. Noninvasive tear break-up time and meniscus height were assessed using OCULUS Keratograph.ResultsTER decreased by more than 20% at 20, 30, and 60 minutes time points after instillation of single drop of cationic emulsion. Also, a significant improvement in tear film stability was found at all time points following the instillation of cationic emulsion eye drops. The mean tear break-up time increased from 5.55 ± 2.87 to 6.6 ± 4.2 sec at 60 minutes. The maximum increase in tear break-up time occurred at 30 minutes time point. The TMH was also significantly higher post-instillation of oil emulsion eye drops. There was a significant increase in the TMH post-therapy with oil drop at all time points.ConclusionThe overall study findings of this study illustrate that the single application of a cationic emulsion effectively controls tear film evaporation in patients with mild to moderate DEs. The cationic emulsion efficiently enhanced both the tear film stability and the tear meniscus volume.

Using a two-Dimensional Finite Element Model to Simulate Biothermal Transfer in the Human Eye) by Considering the Rate of Tear Evaporation and Radiation to the Eye Surface (

Thermal simulation of the human eyeball has been considered in recent years to investigate the effect of external heat sources as well as to predict ocular abnormalities and vital vision disorders. Due to the advances in the field of computing technologies, the use of computer simulation methods such as the use of simulation software and also the use of that software in areas such as medical sciences have received much attention, so that the results have been very helpful in diagnosing various eye diseases and inflammations in the medical community. In the present study, a two-dimensional finite element model has been used to simulate the transfer of biothermal heat in the human eye at steady state. In this study, COMSOL Multiphysics 4.4 software was used to simulate heat transfer in the human eye at steady state. The results of this modeling were compared by examining the effective parameters such as the effect of ambient temperature, blood temperature, lens conduction coefficient, blood transfer heat transfer coefficient, corneal surface diffusion coefficient and the effect of tear evaporation rate. Ocular inflammation is the strongest factor and also the impossibility of ignoring the amount of eye radiation with the environment and the effect of this factor on a significant increase or decrease in corneal surface temperature.

A Pilot Proteomic Study of Normal Human Tears: Leptin as a Potential Biomarker of Metabolic Disorders

The concentrations of insulin, leptin, active ghrelin, C-peptide and gastric inhibitory polypeptide (GIP) and their inter-day variations were examined in normal human tears. In addition, correlations between the concentrations of these metabolic proteins and ocular surface parameters were determined. Subjects with healthy ocular surfaces attended three visits, with 7-day intervals. Tear evaporation rate (TER) and non-invasive tear break-up time (NITBUT) were assessed, and a total of 2 µL tears were collected from all subjects. Tear fluid concentrations of insulin, leptin, active ghrelin, C-peptide and GIP were measured by multiplex bead analysis. Insulin was the most highly expressed metabolic protein, followed by leptin, C-peptide, active ghrelin and GIP. Of these, only active ghrelin had a significant inter-day variation (p &lt; 0.05). There was no inter-day variation in the mean concentrations of the other metabolic proteins. Leptin had a strong intra-class reproducibility. No correlation was detected between tear metabolic protein concentrations and ocular surface parameters. This pilot study shows, for the first time, that active ghrelin and GIP are detectable in healthy tears. The strong intra-class reproducibility for leptin shows that it could be used as a potential tear fluid biomarker and, possibly, in determining the effects of metabolic disorders on the ocular surface.

The Early Effects of Alcohol Consumption on Functional Visual Acuity, Tear Functions, and the Ocular Surface.

We investigated the early effects of alcohol intake on tear functions and ocular surface health in this prospective controlled study. Forty-four eyes of 22 subjects (17 males, 5 females; mean age: 35.3 years) who drank 200 mL of 25% Japanese vodka and 44 eyes of age- and sex-matched 22 control subjects who drank water were investigated. Subjects were requested to refrain from alcohol consumption from the previous day and food ingestion 6 hr before the study. Each subject consumed exactly the same order prepared dinner and same quantity of alcohol over the same time frame. Subjects underwent breath alcohol level, tear evaporation and blink rate, tear lipid layer interferometry, tear film break-up time (BUT), fluorescein and Rose Bengal stainings, Schirmer test, and visual analog scale (VAS) evaluation of dry eye symptoms before, as well as 2 and 12 hr after alcohol intake. The mean breath alcohol level was significantly higher in the alcohol group compared to the water group at 2 and 12 hr (P<0.001). The mean tear evaporation increased significantly from 2.5×10-7 to 8.8×10-7 gr/cm2/sec 12 hr after alcohol intake (P<0.001). The mean BUT shortened significantly from 15.0±5.0 to 5.0±2.5 sec 12 hr after alcohol intake. Lipid layer interferometry showed signs of tear film thinning 12 hr after alcohol intake in all subjects of the alcohol intake group, which was not observed in the water group. The mean blink rates increased significantly from 10.6±1.5 blinks/min to 13.5±0.9 blinks/min and 15.1±1.2 blinks/min at 2 and 12 hr, respectively, in the alcohol group (P<0.001). The Schirmer test values decreased significantly 12 hr after alcohol intake (P<0.001). The mean VAS score for dryness increased from baseline significantly in the alcohol group at 12 hr (P<0.001). No significant time-wise changes in tear functions were observed in the water group. The tear film and ocular surface epithelia showed early and distinctive quantitative and qualitative changes associated with visual disturbances after alcohol intake.

Effect of Eyelid Treatments on Bacterial Load and Lipase Activity in Relation to Contact Lens Discomfort.

To evaluate the effect of microblepharon exfoliation on the number of eyelid bacteria and their lipase activity and the relationship of these to contact lens discomfort. Thirty experienced contact lens wearers had their eyelid margin physiology, tear properties, and comfort scores assessed. The number, type, and frequency of lower eyelid margin bacteria, and their lipase activity, were measured. Eyelids were treated with a foam cleanser or microblepharon exfoliation. Clinical and microbiological tests were repeated at each visit. Changes and correlations were examined. Symptomatic lens wearers had a higher ratio for the number and frequency of gram-positive rods and cocci. Microblepharon exfoliation reduced the number and ratio of gram-positive rods to cocci from baseline for symptomatic wearers that lasted 7 to 10 days after treatment (P<0.05). Numbers of bacteria, the ratio of rods to cocci, and lipase activity correlated with lash contamination (r≥0.385; P≤0.046) and anterior blepharitis (r≥0.359; P≤0.048). Bacterial lipase correlated with meibomian gland secretions (r=0.422; P=0.038) and the tear evaporation rate (r=0.479; P=0.022). Microblepharon exfoliation produced a significant reduction in CLDEQ-8 scores and converted 10 symptomatic into asymptomatic lens wearers. There was dysbiosis in the lid microbiome of symptomatic lens wearers. Microblepharon exfoliation reduced the number, frequency of isolation, and ratio of gram-positive rods and cocci. Bacterial numbers and their lipase production correlated with changes to clinical signs and symptoms. Symptomatic lens wearers could be converted to asymptomatic lens wearers after microblepharon exfoliation.