Tear Film Lipid Layer Research Articles

Assessment of meibomian gland morphology and tear-film lipid layer using noncontact infrared meibography and meibometry, respectively, and tear-film osmolarity in healthy dogs.

To further investigate quantitative and qualitative tear-film dynamics through tear-film osmolarity, meibometry, meibography, and non-invasive tear-film break-up time and to describe a survey of parameters in normal eyes of healthy non-brachycephalic dogs. Thirty-two veterinary hospital staff and student owned dogs between 1 and 7 years with no known comorbidities or ocular disease. Complete ophthalmic examination, tear-film osmolarity (I-PEN® VET), meibometry (Meibometer MB560), meibography, and non-invasive tear-film break-up time (handheld Ocular Surface Analyzer) were performed. Significance threshold was 0.05. Q-Q plots and histograms were used to assess normality of measurements. Data were summarized descriptively with mean, standard deviation, median, and interquartile range (IQR). Pearson and Spearman's correlations were used to test for correlations between diagnostics with each other and tear-film break-up times. Thirty-two dogs (64 eyes) met the inclusion criteria. Mean tear-film osmolarity level was 293.6 ± 14.1 mOsm/L (IQR 282.5-302.3). Median meibomian lipid level was 30.4 Meibometry Units (MU) (IQR 11.5-59.1). Median percent loss of meibomian glands in the upper eyelids was 25.3% (IQR 13.5-26.8). Median percent loss of meibomian glands in the lower eyelids was 26.0% (IQR 13.5-52.3). Automatic assessment of meibomian gland loss showed that grade 0 was present in 4/128 (3.1%) eyelids, grade 1 in 78/128 (60.9%) eyelids, grade 2 in 30/128 (23.4%) eyelids, and grade 3 in 16/128 (12.5%) eyelids. Tear-film osmolarity, meibometry, meibography, and non-invasive tear break-up time can easily be incorporated into routine ophthalmic examinations to provide clinical information about meibomian gland morphology and function.

Decipher 'Em All: A Profiling Study on the Effects of Acyl Groups in O-Acyl-ω-hydroxy Fatty Acids.

The O-acyl-ω-hydroxy fatty acids (OAHFAs) are an intriguing class of surface-active lipids which can be found in the human tear film lipid layer (TFLL). Recent studies have suggested that OAHFAs exist in the polar lipid layer and play a central role in TFLL function. Surprisingly, biophysical profiling studies have only shed light on the properties of OAHFAs bearing an oleate acyl group and insights on species with other acyl groups are scarce. Herein, we seek to address this issue through (1) focusing on the synthesis and characterization of a representative library of OAHFA analogues bearing a palmitate, palmitoleate, stearate, and linoleate acyl group, and (2) performing an in-depth mapping of their biophysical properties. Our results indicate that NMR-spectroscopic techniques can be utilized for rough estimation of the amounts of distinct acyl groups in a sample and more importantly, how the subtle variations in both parent chains and acyl groups influence the core properties of the OAHFAs. We reach the conclusion that the correlation between melting points and film properties is not as clear-cut as previously thought. Nevertheless, grouping of OAHFA species into three separate categories which display distinct behavior seems to be possible utilizing the melting points as a guiding parameter. Altogether, our study suggests that the properties of OAHFAs need to be assessed from a viewpoint which combines both the parent chain and acyl group instead of independent analysis based on either fragment alone.

Immediate sequential changes in the tear film lipid layer following eyelid massage in dry eye syndrome: A comparative control study

Background/PurposeMeibomian glands are sebaceous glands that release meibum onto the ocular surface; enhancing the quality and quantity of meibum secretions has been proven to improve signs and symptoms of evaporative dry eye (EDE) and meibomian gland dysfunction (MGD). This study aimed to evaluate and compare the efficacy of a heated eye mask (HEM) and eyelid massage device EyePeace (EP) in alleviating signs and symptoms of evaporative dry eye. MethodsForty dry eye participants were recruited in a prospective, contralateral-eye trial study. After undergoing 10 min of HEM therapy, eyelid massage therapy was applied to one eye by the device. The efficiency was assessed at four time points: baseline (0 min), 5 min (5 min), 15 min (15 min), and 30 min (30 min). Non-invasive breakup time (NITBUT), redness score (RS Score), tear meniscus height (TMH), tear-film lipid layer (TFLL), endothelial cell count (ECC), meibomian gland expressibility (MGEx), meibomian gland quality (MGQ), conjunctivocorneal staining (CS), ocular surface temperature (OST), best corrected visual acuity (BCVA), intraocular pressure (IOP), central corneal thickness (CCT) flat-axis keratometry value (K1), and steep-axis keratometry value (K2), were examined. ResultsBaseline clinical measurements did not have statistically significant differences between the groups (all p > 0.05). After 30 min, a comparison was made between the HEM group and EP + HEM group, revealing significant changes only in the primary outcomes, TFLL (2.18 ± 0.45 versus 2.40 ± 0.50; p < 0.05), and MGEx grades (0.68 ± 0.53 versus 0.98 ± 0.70; p < 0.05). Improvements in NITBUT and TMH were sustained until 5 min and 15 min after using EP + HEM. No significant changes were observed in RS Score, MGQ, OST, CFS, BCVA, IOP, ECC, K1, K2, and CCT (all p > 0.05) at all test time points. ConclusionThe application of a heated eye mask followed by a gentle massage using EyePeace on the eyelids can have a sustained improvement in the tear film lipid layer and meibomian gland expressivity score but not clinically significant, and does not pose any significant immediate impact on the cornea.Trial registration number: NCT06158997.

Aqueous-Deficient Dry Eye Increases Lipid Layer Thickness Measured by Dynamic Tear Interferometry.

To investigate the impact of aqueous deficiency on lipid layer thickness (LLT) measurement in dry eye disease before and after treatment of aqueous-deficient dry eye (ADDE) using dynamic tear interferometry. This prospective comparative study included 230 eyes from 230 patients with ADDE. The treatment group with punctal plug insertion was compared with the control group. The average LLT (LLTave) was measured with a LipiView II tear interferometer at baseline and after 1 month. Correlation analyses were performed with the indices of the dynamics of the tear film lipid layer (TFLL). Baseline LLTave values were 116.1 ± 26.7 and 112.3 ± 27.6 nm in the treatment group (n = 121) and the control group (n = 109), respectively. At 1 month, LLTave significantly decreased in the treatment group (difference -41.8 [95% confidence interval (CI) -47.2 to -36.3], P = 0.003). The values of tear meniscus height (TMH) at baseline and 1-month follow-up were negatively correlated with LLTave (both P < 0.001). Spreading time of TFLL to equilibrium and the deviation of TFLL were positively correlated with LLTave (all P < 0.001) and negatively correlated with TMH (P < 0.001 and 0.009). In multivariate analysis (adjusted R2 = 0.411, P < 0.001), LLTave was associated with TMH (B = -1.068; P < 0.001), adjusting for age, sex, and meibomian gland expressibility. In ADDE, the TFLL was measured to be thicker than the normal range of 60 to 99 nm and became thinner with treatment. LLT was affected by not only meibum secretion but also aqueous status due to changes in the dynamics of TFLL.

Effect of low-level light therapy in individuals with dry eye disease.

Low-level light therapy (LLLT) or photobiomodulation, the application of red light to the eye, is used for the treatment of dry eye. Limited studies have investigated the efficacy of LLLT as a stand-alone treatment. The investigation aimed to evaluate the effect of LLLT on signs and symptoms of dry eye. Participants with mild to moderate dry eye were recruited for this three-visit study. Visits were 7 (±3) days apart and all participants received 633 nm LLLT (eye-light®) for 15 min at each visit. Clinical measures including first and average non-invasive keratograph tear break-up time (NIKBUT), tear meniscus height (TMH), meibomian gland (MG) loss for upper and lower eyelids, ocular surface disease index (OSDI) score, tear film lipid layer thickness, meibum quality score, Schirmer's test, corneal fluorescein staining and eyelid temperature for external upper (EUL) and external lower (ELL) eyelids were measured from the right eye of participants before and after treatment. Thirty participants (mean [SD] age: 31.1 [9.5] years) completed the study. Treatment with LLLT resulted in significant differences in first and average NIKBUT, TMH, tear film lipid layer thickness, OSDI score, Schirmer's test, meibum quality score and eyelid temperature over time (all p < 0.05). Compared to baseline, TMH, tear film lipid layer thickness and eyelid temperature significantly increased by 0.06 mm (95% CI: 0.01-0.11), 12.9 nm (95% CI: 1.18-24.55), and 7.0°C, respectively,for both EUL (95% CI: 6.17-7.84) and ELL (95% CI: 6.17-7.73). The respective decrease in the OSDI score and Schirmer's test was 10.2 (95% CI: -15.15 to -5.26) and 4.4 mm (95% CI: -7.31 to -1.42; all p < 0.05). There was no significant difference in corneal fluorescein staining and MG loss after LLLT. Low-level light therapy treatment significantly improved signs and symptoms of dry eye in the early phases of treatment, suggesting its efficacy for dry eye management.

Spaceflight associated dry eye syndrome (SADES): Radiation, stressors, and ocular surface health

Crewed spaceflight missions require careful scrutinization of the health risks including alterations to the tear film lipid layer in astronauts. We review the current literature and prior published work on tear film lipid layer biophysics and secondary spaceflight-associated dry eye syndrome (SADES). We define the term spaceflight-associated dry eye syndrome to describe the collection of ocular surface signs and symptoms experienced by astronauts during spaceflight. Our review covers the ocular surface and lipidomics in the spaceflight environment. From our literature review, we extrapolate biophysical principles governing the tear film layer to determine the changes that may arise from the harsh conditions of spaceflight and microgravity. Our findings provide vital information for future long-duration spaceflight, including a return to the Moon and potential missions to Mars.

High Resolution Images of Human Meibum Spread on Saline.

Understanding of the role of the tear film lipid layer (TFLL) in evaporative dry eye requires knowledge of its structure. X-ray studies show 11.1-nm thick lamellae in meibum at tear film temperature (approximately 35°C), whereas below 30°C, 4.88-nm thick lamellae predominate. Here, high resolution microscopy of meibum spread on saline is studied as a function of temperature, to compare with x-ray results. A purpose-built high resolution color microscope, previously used to study the TFLL, was used to study meibum from 10 subjects. It was spread on buffered saline at near 40°C, and allowed to cool to room temperature. Analytical methods from previous studies were applied to measure meibum and lamellar thickness. Initially, an irregular "island" was formed, surrounded by a "background layer" of 7.8 ± 0.3 nm thickness. Dewetting of the meibum layer always occurred, leading to the formation of lens-shaped droplets. Below 30°C, the lenses start to emit "tails" having a multilamellar structure containing up to about 49 lamellae superimposed on the background layer, each lamella being 4.82 ± 0.13 nm thick. Below 30°C, meibum spread on saline shows a multilamellar structure like the 4.88 nm thickness in x-ray studies, demonstrating the ability to observe and measure tightly stacked lamellae. In contrast, above 30°C, the 11.1 nm lamellae were not observed as in x-ray studies, indicating that these lamellae were not tightly stacked but may be separated by disordered lipid. The role of these findings in evaporative dry eye is discussed.

Tear film assessment before and after phacoemulsification in patients with age-related cataracts

BackgroundThe study aims to assess the tear film before and after phacoemulsification in patients with age-related cataracts.MethodsA prospective observational study of 41 age-related cataract patients undergoing phacoemulsification procedure. Tear Film Break-Up Time (TBUT), Tear Film Meniscus Height (TMH), Meibomian glands (MG), and Lipid Layer Thickness (LLT) were assessed by a non-invasive Dry Eye Diagnostic System. All measurements were taken preoperatively, one week, one month, and three months postoperatively. The Marginal homogeneity and The Cochran Q tests were used in the statistical analysis.ResultsThe value of Non-Invasive Break-Up Time (NITBUT) was statistically significantly lower at one week (7.15 ± 3.31), one month (7.61 ± 3.41), and three months (7.66 ± 3.36) postoperatively than preoperatively (10.71 ± 2.71), p < 0.001. The Non- Invasive Tear Meniscus Height (NITMH) was significantly lower at one week (0.18 ± 0.0), one month (0.20 ± 0.09), and three months (0.20 ± 0.09) postoperatively than preoperatively (0.30 ± 0.113) p < 0.001. By the first month, both (NITBUT) and (NITMH) improved significantly compared to the first post-operative week. There was no statistically significant difference between one month and three months. The (NITMH) improved to a healthy level of ≥ 0.2 mm by the first month through the third month. Both (NITBUT) and (NITMH) did not reach the baseline by the third month. The meibomian glands and the lipid layer thickness had the same preoperative grade distribution without changes.ConclusionPhacoemulsification surgery can cause post-operative deterioration in the tear film, which starts within a week of the procedure, followed by gradual recovery over the next weeks and months. The phacoemulsification procedure mainly affects the tear break-up time and tear meniscus height. Both the lipid layer and meibomian glands are not affected.

Management of Glaucoma-Related Dry Eye Disease with Intense Pulsed Light: A Randomized Control Study.

The objective of this study was to assess the effectiveness of intense pulsed light (IPL) therapy in individuals diagnosed with glaucoma and dry eye disease (DED). This randomized control study recruited 22 individuals diagnosed with glaucoma, ranging in age from 33 to 82 years. These participants were undergoing treatment with hypotensive eyedrops and had clinical indications and subjective complaints associated with dry eye. Each patient underwent three sessions of IPL therapy in one eye, while the contralateral eye served as the control eye (CT). The following parameters were assessed at three time points: baseline, week-2, and week-4. These parameters include non-invasive breakup time (NITBUT), tear meniscus height (TMH), conjunctivocorneal epithelial staining score (CS), tear film lipid layer (TFLL), meibomian gland expressibility score (MGEx), Schirmer I test, ocular bulbar redness score (OBRS), and ocular surface disease index (OSDI). Intraocular pressure (IOP), best-corrected visual acuity (BCVA), and corneal endothelial cell count (ECC) were assessed for safety. The clinical trial was registered on 25/12/2023 at ClinicalTrials.gov website (NCT06158984). Comparing baseline and 4-week measurements revealed that the IPL group found significant improvements in NITBUT (IPL: 8.74±2.60 sec. vs CT: 5.76±1.75 sec. p<0.01), TMH (IPL: 0.23±0.05mm vs CT: 0.19±0.06mm, p=0.011), C.S. (IPL: 1.14±0.56 vs CT: 1.95±1.17, p=0.005), TFLL (IPL: 2.91±2.91 vs CT:3.36±0.58, p=0.047), MGEx score (IPL: 1.14±0.35 vs CT: 1.45±0.51, p=0.020) and OSDI scores (IPL: 31.77±15.59 vs 50.59±21.55, p=0.002) significantly improved. Conversely, other parameters showed no significant improvements (p>0.05). The progression of ocular surface disease in individuals using topical anti-glaucoma medication may worsen if the condition is not addressed. Nevertheless, IPL therapy has the potential to result in significant improvements in both objective and subjective measures of dry eye. Best-corrected visual acuity, endothelial cell count, and intraocular pressure were determined to be within the permitted limits. No adverse events were reported during the course of the study.

Smartphone-Based Interferometry for Non-Invasive Assessment of Tear Film Lipid Layer Kinetics

Smartphone-Based Interferometry for Non-Invasive Assessment of Tear Film Lipid Layer Kinetics

Meibum Lipidomic Analysis in Evaporative Dry Eye Subjects.

Meibomian Glands (MG) are sebaceous glands responsible for the production of meibum, the main component of the Tear Film Lipid Layer (TFLL). The TFLL facilitates the spread of the tear film over the ocular surface, provides stability and reduces tear evaporation. Alterations in meibum composition lead to different ocular alterations like Meibomian Gland Dysfunction (MGD) and subsequent Evaporative Dry Eye (EDE). The aim of the present study was to investigate the composition and abundance of meibum lipids and their relationship with eyelid margin abnormalities, lipid layer patterns and MG status. The study utilizes a lipidomic approach to identify and quantify lipids in meibum samples using an Elute UHPLC system. This system considered all four dimensions (mass/charge, retention time, ion mobility and intensity) to provide the accurate identification of lipid species. Samples were categorized as healthy or low/no signs of alteration (group 1) or severe signs of alteration or EDE/MGD (group 2). The current investigation found differences in Variable Importance in Projection lipid abundance between both groups for the MGD signs studied. Changes in meibum composition occur and are related to higher scores in eyelid margin hyperaemia, eyelid margin irregularity, MG orifice plugging, MG loss and lipid layer pattern.

Another Brick in the Wall of Tear Film Insights Added Through the Total Synthesis and Biophysical Profiling of anteiso-Branched Wax and Cholesteryl Esters.

The tear film lipid layer (TFLL) plays a vital part in maintenance of ocular health and represents a unique biological barrier comprising unusual and specialized lipid classes and species. The wax and cholesteryl esters (WEs and CEs) constitute roughly 80-90% of the TFLL. The majority of species in these lipid classes are branched and it is therefore surprising that the synthesis and properties of the second largest category of species, i.e., the anteiso-branched species, remain poorly characterized. In this study, we have developed a total synthesis route and completed a detailed NMR spectroscopic characterization of two common anteiso-branched species, namely: (22S)-22-methyltetracosanyl oleate and cholesteryl (22'S)-22'-methyltetracosanoate. In addition, we have studied their structural properties in the bulk state by wide-angle and small-angle X-ray scattering and their behavior at the aqueous interface using Langmuir monolayer techniques. A comparison to the properties displayed by iso-branched and straight-chain analogues indicate that branching patterns lead to distinct properties in the CE and WE lipid classes. Overall, this study complements the previous work in the field and adds another important brick in the tear film insights wall.

Comparison of non-pharmaceutical treatments for evaporative dry eye: a randomised controlled study protocol

IntroductionThe lipid layer of the tear film is critical to maintaining the integrity of the tear film and absence in the tear film lipid layer (TFLL) is one of the...

Evaluation of tear film in patients with AIDS without opportunistic ocular infections in the era of COVID-19: A case-control study.

The assessment of tear film and ocular surface conditions in patients with acquired immunodeficiency syndrome (AIDS) has been poorly studied thus far. We aim to assess tear film parameters, ocular surface characteristics, and dry eye disease (DED) symptoms of patients with AIDS who did not undergo highly active antiretroviral treatment (HAART). This case-control study included 154 age-, sex-, and ethnicity-matched healthy controls and patients with AIDS. All participants underwent comprehensive ocular surface assessment and subjective DED symptomology evaluation. Data were collected between March 2022 and July 2022. HAART-naïve patients with AIDS had a shorter noninvasive tear film breakup time (median 3.76 vs. 8.54 s), thinner tear film lipid layer thickness (median 73.00 vs. 91.00 nm), and lower Schirmer I test values (median 5.00 mm/5 min vs. 12.00 mm/5 min) (all P < 0.001). Moreover, higher corneal fluorescein staining scores (median 1.00 vs. 0.00) and higher upper, lower, and total meibomian gland grades were observed in AIDS patients (all P < 0.05). Negative correlations between the blood viral load and the Ocular Surface Disease Index score ( r = -3.50, P = 0.027) and the Schirmer I test score ( r = -0.374, P = 0.017) were detected in patients with AIDS. Altered tear film status was observed in individuals with HAART-naïve AIDS, even when there were no other ocular symptoms present. Therefore, patients with AIDS should be encouraged to undergo comprehensive ocular surface examinations to detect any subclinical tear film alterations occurring.

New Insights into the Molecular Structure of Tear Film Lipids Revealed by Surface X-ray Scattering.

The tear film lipid layer (TFLL) is a unique biological membrane that serves a pivotal role in the maintenance of ocular surface health. Reaching an overarching understanding of the functional principle of the TFLL has been hampered by a lack of insights into the structural and functional roles played by individual lipid classes. To bridge this knowledge gap, we herein focus on studying films formed by principal lipid classes by surface scattering methods. Through grazing incidence X-ray diffraction and X-ray reflectivity studies, we reveal quantitative data about the lattice distances, molecular tilt angles, and mono/multilayer thickness and density profiles for central TFLL lipid classes under close to simulated physiological conditions. In addition, we discuss the correlation of the results to those obtained previously with the natural lipid composition of meibum.

Применение нового комбинированного препарата, содержащего среднецепочечные триглицериды, в лечении синдрома «сухого глаза»

Background: the outer layer of the tear film is composed of nonpolar lipids, including free fatty acid esters, triglycerides (TG), and cholesterol esters. Alterations in their qualitative and quantitative composition can result in evaporative dry eye, which requires pathogenic treatment. Somatic comorbidities, particularly type 2 diabetes (T2D), may act as a potential etiological factor. Aim: to assess the efficacy of a new complex medication containing medium chain TGs for the treatment of dry eye. Patients and Methods: a single-center, observational, single-stage, controlled single-sample, non-randomized study was conducted. Twenty-seven patients (mean age 52.5±0.5 years) were included in the study. Group 1 included 12 patients with dry eye and T2D. Group 2 included 15 patients with dry eye but no T2D. Patients received a complex medication containing medium chain TGs and carbomer for one month. In addition to standard and additional eye examinations, tearscopy and low-resolution mass spectrometry using LCQ Fleet (Thermo Scientific, Germany) were performed. Results: a reduction in the levels of TG and cholesterol was demonstrated in both groups. The reduction was more significant in group 1. A complex medication containing medium chain TGs and carbomer for one month improved functional indices in group 1 patients compared with baseline (p &lt;0.05). Corneal staining grade 1 was reported in 94% of group 1 patients. In group 2, corneal staining did not change significantly. Tearscopy revealed a significant improvement in the tear film lipid layer in group 1 (an increase in the lipid distribution coefficient and lipid thickness by 0.2 and 0.03, respectively) in comparison to group 2 (an increase by 0.1 and 0.02). Conclusions: decreased levels of TGs and cholesterol in T2D induce cellular dysfunction and inflammation in meibomian glands, thereby triggering dry eye development and/or worsening its course. In light of these considerations, complex medications containing TGs are necessary and reasonable. KEYWORDS: medium chain triglycerides, carbomer, meibomian gland dysfunction, dry eye, mass spectrometry, diabetes. FOR CITATION: Safonova T.N., Zaytseva G.V., Kravets K.Yu., Polyakov N.B. Novel complex medication containing medium chain triglycerides for the treatment of dry eye. Russian Journal of Clinical Ophthalmology. 2024;24(2):64–68 (in Russ.). DOI: 10.32364/2311- 7729-2024-24-2-4.

Novel anti‐evaporative lipid‐based formulation for dry eye disease treatment

Purpose: The majority of dry eye disease (DED) patients suffer from the tear film lipid layer (TFLL) instability issues associated with increased evaporation of water from the ocular surface. Therefore, we developed a liposomal formulation based on selected TFLL lipid classes that would restore the tear film stability and retard the evaporation of the aqueous tear fluid.Methods: The liposomal formulation was prepared by the thin film hydration method and subsequently characterized intermittently by standard techniques for at least 6 months. The mitochondrial metabolic activity (MTT) assay with human corneal epithelial (HCE) cells was utilized to assess the formulation toxicity in vitro. The evaporation resistance properties of the formulation were determined in vitro by the Langmuir trough methods, while a DED cellular model engendered by exposing the HCE cells to benzalkonium chloride (BAC) enabled additional assessment of the in vitro efficacy. In vivo safety was evaluated in rats and rabbits in one‐week studies. The conditions of the animal eyes were assessed by a non‐invasive biomicroscope, an optical coherence tomography, and histological staining of the dissected eyes.Results: The lipid‐based formulation with favourable pharmaceutical and functional properties (e.g., the evaporation resistance, and the promotion of HCE cell recovery after damage) was developed successfully, while also the physical stability of the formulation was found promising. No evidence of toxicity was observed during in vitro and in vivo experiments.Conclusions: The results suggest that the developed formulation is well‐tolerated and possesses properties and a safety profile compatible with ocular administration. Utilized in vitro efficacy models imply that the developed formulation is a promising candidate towards more efficient DED treatment. In vivo efficacy remains to be clarified in future studies.

Липидный анализ слезной жидкости в диагностике дисфункции мейбомиевых желез

The tear film lipid layer plays a crucial role in maintaining ocular surface homeostasis by preventing excessive evaporation of the aqueous layer and reducing heat transfer from the corneal and conjunctival surface. The lipid composition of the tear film is unique and consists of two main layers: the outer (nonpolar lipids) and the inner (polar lipids). The thick outer layer of the tear film is composed of non-polar lipids that lack internal distributed charge, while the thin inner layer is formed by polar lipids with positive and negative charges at the ends of the molecule. Both types of lipids are synthesized in the meibomian glands (MG) and contribute to tear film stability. Meibomian gland dysfunction (MGD) alters the composition and physical properties of lipids, leading to pathological changes in both the MG and tear film. In meibomian gland dysfunction (MGD), the meibum thickens and acquires a higher melting point than normal. This leads to a decrease in the amount of nonpolar and amphiphilic lipids in the meibomian gland secretion and tear film. Consequently, the protective effect of the tear lipid layer is impaired, and its stability is compromised. Lipid mapping analyzes the lipid composition of biological samples, such as tear fluid, to study the mechanisms of the development and progression of various ocular surface diseases, including dry eye syndrome, MGD, and recurrent blepharoconjunctivitis. This method provides fundamental data on the properties of the tear film in various ocular surface diseases. It has the potential to establish hallmarks of disease course and develop personalized treatment approaches for specific clinical cases. KEYWORDS: tear, tear film lipids, ocular surface, meibomian gland dysfunction, lipid analysis. FOR CITATION: Takhauova L.R., Guseva A.A., Krylova A.A., Krivosheina O.I. Lipid analysis of tear fluid as a diagnostic tool for meibomian gland dysfunction. Russian Journal of Clinical Ophthalmology. 2024;24(2):83–87 (in Russ.). DOI: 10.32364/2311-7729-2024-24-2-7.

Dysfunkcja gruczołów Meiboma jako przyczyna stanów zapalnych powierzchni oka

Meibomian glands dysfunction is described as one of the most common ophthalmic diseases in the world. Meibomian glands dysfunction is the most common cause of posterior blepharitis. Meibomian glands are the only ones responsible for the production of the tear film lipid layer. There are many diseases which induce Meibomian glands dysfunction, even leading to their disappearance. It is concluded that Meibomian glands dysfunction can both cause and result from dry eye syndrome through a process of events involving inflammation of the ocular surface. Accurate diagnosis becomes a great challenge, and it is of key importance in selecting the optimal form of treatment. This article provides an overview of the current understanding of Meibomian gland dysfunction and its therapeutic outlook.

Using machine learning model explanations to identify proteins related to severity of meibomian gland dysfunction

Meibomian gland dysfunction is the most common cause of dry eye disease and leads to significantly reduced quality of life and social burdens. Because meibomian gland dysfunction results in impaired function of the tear film lipid layer, studying the expression of tear proteins might increase the understanding of the etiology of the condition. Machine learning is able to detect patterns in complex data. This study applied machine learning to classify levels of meibomian gland dysfunction from tear proteins. The aim was to investigate proteomic changes between groups with different severity levels of meibomian gland dysfunction, as opposed to only separating patients with and without this condition. An established feature importance method was used to identify the most important proteins for the resulting models. Moreover, a new method that can take the uncertainty of the models into account when creating explanations was proposed. By examining the identified proteins, potential biomarkers for meibomian gland dysfunction were discovered. The overall findings are largely confirmatory, indicating that the presented machine learning approaches are promising for detecting clinically relevant proteins. While this study provides valuable insights into proteomic changes associated with varying severity levels of meibomian gland dysfunction, it should be noted that it was conducted without a healthy control group. Future research could benefit from including such a comparison to further validate and extend the findings presented here.