Human meibum and tear film derived cholesteryl and wax esters in meibomian gland dysfunction and tear film structure

Impact of Hyperglycemia on Tear Film and Meibomian Gland Dysfunction: A Cross-Sectional Study

Purpose

Elevated blood glucose levels may disrupt tear film and meibomian gland function, contributing to dry eye disease (DED) and meibomian gland dysfunction (MGD). This study aimed to explore the relationship between hyperglycemia and DED parameters.

Methods

A cross-sectional study at Chifeng Chaoju Eye Hospital (June-August 2024) included 56 participants with DED symptoms. Tear meniscus height (TMH), non-invasive tear film breakup time (FNIBUT, ANIBUT), bulbar redness, and meibomian gland atrophy (U-LAMG, L-LAMG) were assessed using a non-invasive ocular surface analyzer. Fasting blood glucose levels stratified patients into high (≥7 mmol/l) and normal (<7 mmol/l) groups, and their association with DED parameters was analyzed.

Results

Among 56 patients (mean age 52.5 ± 18.0 years), those with elevated glucose levels (n=28) had more severe DED symptoms (OSDI, p = 0.046), lower TMH, FNIBUT, ANIBUT, and higher bulbar redness scores (all p < 0.05). In contrast, lower glucose levels were associated with greater U-LAMG and L-LAMG atrophy (p < 0.05). Glucose positively correlated with intraocular pressure (IOP), redness, U-LAMG, and L-LAMG but negatively correlated with TMH, FNIBUT, and ANIBUT (all p < 0.05).

Conclusion

Hyperglycemia is linked to impaired tear film stability, meibomian gland function, and DED symptoms. Ocular surface disorders in individuals with diabetes may be prevented by effective glycemic control.

Exploring the Effects of Gracilaria lemaneiformis Polysaccharides on the Fecal Microbiota and Fecal Metabolites of Fattening Pigs Based on 16S rDNA and Metabolome Sequencing

Sixty Duroc × (Landrace × Yorkshire) castrated male finishing pigs were randomly divided into negative control (NC) and gracilaria lemaneiformis polysaccharides (GLP) groups to study the effects of GLP on the fecal microbiota and fecal metabolites of fattening pigs. The NC group was fed a basic diet, and the GLP group was fed a basic diet supplemented with 0.1% GLP. The diversity of the species and the fecal metabolites were analyzed using 16S rDNA sequencing and metabolome sequencing, respectively. The serum immune and antioxidant indices were analyzed using the ELISA assay. The abundances of hazardous bacteria such as Proteobacteria at the phylum level and Shigella at the genus level were extremely significantly decreased (p < 0.01) and those of beneficial bacteria such as Firmicutes at the phylum level (p < 0.01), Clostridium at the genus level (p < 0.01), and Lactobacillus at the genus level (p < 0.05) were significantly increased in the GLP group compared with the NC group. A total of 41 differentially expressed metabolites were identified. The expression of anti-inflammatory and antioxidant active substances, such as methyl cinnamate, protopanaxatriol, and isovanillic acid, was elevated in the GLP group. The ELISA assay showed increased GSH-Px activity (p < 0.01), T-AOC (p < 0.01), IgG (p < 0.01), IgA (p < 0.05), and IgM (p < 0.05) in the GLP group. These results indicate that dietary GLP supplementation can improve the antioxidant ability, anti-inflammatory ability, and immune level of fattening pigs by regulating fecal flora and metabolites and could be used as a functional feed additive.

A Comparative Metabolomics Study of the Potential Marker Compounds in Feces from Different Hybrid Offspring of Huainan Pigs

As a notable native Chinese genetic population, the Huainan pig has an exceptional meat quality but a low percentage of lean meat and subpar genetic performance. To better exploit the superior genetic traits of the Huainan pig and address knowledge gaps regarding the optimization of its hybrid offspring, this study used Huainan pigs as the maternal line and bred them with Yorkshire, Landrace, and Berkshire sires. This approach produced three hybrid combinations: Yorkshire × Huainan (YH), Landrace × Huainan (LH), and Berkshire × Huainan (BH). The body size, fat ratio, and average backfat thickness of these hybrid progeny were evaluated under the same feeding management and nutritional circumstances. The results revealed that the average backfat thickness of YH was significantly lower than that of LH and BH. In order to better understand the causes of these variations, fecal samples were taken from three pigs in each group for metabolomic analysis. A total of 2291 metabolites were identified, including benzene derivatives (16.6%), amino acids and their metabolites (14.5%), and organic acids (13.4%), with pyruvaldehyde and norethindrone acetate elevated in YH compared to LH and BH. In addition, the three hybrid pig groups commonly exhibited differences in the "glycerophospholipid metabolism" pathway. This variation may also contribute to differences in their fat ratio and backfat thickness. Our findings provide a novel perspective on the role of hybrid vigor in advancing the genetic population of Huainan pigs, while also revealing the unique metabolic characteristics of the YH with regard to fat deposition. This study is expected to enhance the conservation and effective utilization of genetic resources within the Huainan pig population.

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.

Meibomian gland lipid alterations and ocular surface sequela in Awat2 knockout murine model of meibomian gland dysfunction and evaporative dry eye disease

PURPOSE

There is an urgent need for animal models of meibomian gland dysfunction (MGD) and evaporative dry eye disease (EDED) to understand their pathophysiology and investigate novel therapeutics. This study sought to further define the acyl-CoA: wax alcohol acyltransferase 2 knockout (Awat2 KO) mouse as a model of EDED using a combination of novel clinical, biochemical, and biophysical endpoints.

METHODS

Wildtype and Awat2 KO mice between 1 and 18 months of age were used. Ocular examinations and advanced imaging were performed. The lipidomic composition and in situ melting temperature of meibum were determined. qPCR was performed to define ocular surface gene and pro-inflammatory transcript expression. Dynamic contact angle goniometry was performed to assess the adherence capability of the ocular surface.

RESULTS

Awat2 KO mice have mild, white, hyperreflective corneal opacities of the anterior stroma and significantly enlarged apical epithelial cells (P = 0.0004). In Awat2 KO meibum, wax esters were 9-10 times lower than in wildtype meibum. Additionally, meibum melting temperature increased from 32° to 47 °C (P < 0.0001), leading to impaired meibum secretion and dilation of the central duct. Awat2 KO corneal epithelia had significantly decreased mucin expression (Muc1 and Muc4, P = 0.0043) and increased interferon-γ production (P = 0.0303). Awat2 KO globes have a significantly shortened time of droplet adherence to their ocular surface (P = 0.0053), indicating a decreased tear film adherence capacity. Wildtype corneal epithelia does not express Awat2, indicating that the EDED phenotype is secondary to the loss of Awat2 from the meibomian glands.

CONCLUSIONS

Awat2 KO mice recapitulate many of features of human MGD and EDED, representing a model to test novel therapeutics.

Nanomedicines for Dry Eye Syndrome: Targeting Oxidative Stress with Modern Nanomaterial Strategies

Dry eye syndrome (DES) is a dynamic, chronic disease of the ocular surface and ocular appendages caused by inflammation. The most common symptoms include redness, itching, and blurred vision, resulting from dysfunction of the meibomian glands and impaired tear-film production. Factors contributing to the development of DES include environmental elements, such as UV radiation, and internal elements, such as hormonal imbalances. These factors increase oxidative stress, which exacerbates inflammation on the surface of the eye and accelerates the development of DES. In recent years, the incidence of DES has risen, leading to a greater need to develop effective treatments. Current treatments for dry eye are limited and primarily focus on alleviating individual symptoms, such as reducing inflammation of the ocular surface. However, it is crucial to understand the pathomechanism of the disease and tailor treatment to address the underlying causes to achieve the best possible therapeutic outcomes. Therefore, in this review, we analyzed the impact of oxidative stress on the development of DES to gain a better understanding of its pathomechanism and examined recently developed nanosystems that allow drugs to be delivered directly to the disease site.

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.

Efficacy of meibomian gland expression combined with Home-Based therapy in the management of dry eye Disease: A systematic review and Meta-Analysis

PURPOSE

To compare the effectiveness of meibomian gland expression (MGX) combined with home-based therapy versus home-based therapy alone for the treatment of dry eye disease (DED) caused by meibomian gland dysfunction (MGD).

METHODS

A systematic review of randomized controlled studies (RCTs), reporting the effects of MGX combined with home-based therapy in 2 databases, PubMed and Web of Science, was performed according to the PRISMA statement. The search period was until August 20, 2023. According to the heterogeneity, a random or fixed effects model was performed in the meta-analysis. The standardized mean difference (SMD) was calculated to analyze dry eye symptoms (DES) score, tear film break-up time (TBUT), total corneal fluorescein staining (tCFS) and meibomian glands expressibility (MGE). All analyses were performed by RevMan Web, version 5.7. The Cochrane risk of bias tool was used to analyze the quality of the studies selected.

RESULTS

Two RCTs with a total of 99 patients were included. The studies reported that MGX combined with home-based therapy improves DES score, TBUT, tCFS and MGE compared to the home-based therapy. However, the meta-analysis indicated that MGX combined with home-based therapy only seems to be beneficial in reducing DES score (SMD -0.49; 95 % CI: -0.89 to -0.08; P = 0.02; I2 = 0 %). In addition, although TBUT, tCFS and MGE reported a slight trend in favor of MGX combined with home-based therapy, it was non-significant.

CONCLUSIONS

While MGX combined with home-based therapy seem to show some evidence of alleviating dry eye symptoms, there is insufficient evidence to conclude the effects of this treatment definitively particularly in improving dry eye signs caused by MGD, such as TBUT, tCFS and MGE. Therefore, further RCTs are needed to elucidate these results.

Relationship Between Human Meibum Lipid Composition and the Severity of Meibomian Gland Dysfunction: A Spectroscopic Analysis

Purpose

Information on the relationship between meibum lipid composition and severity of meibomian gland dysfunction (MGD) is limited. The purpose of this study was to analyze the molecular components of meibum collected from individuals with no MGD, mild-to-moderate MGD, and severe MGD.

Methods

Adults with and without MGD were enrolled in a prospective, multicenter, exploratory clinical trial (ClinicalTrials.gov Identifier: NCT01979887). Molar ratios of cholesteryl ester to wax ester (RCE/WE) and aldehyde to wax ester (Rald/WE) in meibum samples were measured with 1H-NMR spectroscopy. Results were evaluated for participants grouped by MGD disease status and severity (non-MGD, mild-to-moderate MGD, and severe MGD), as defined by maximum meibum quality scores, Schirmer test results, and Subject Ocular Symptom Questionnaire responses.

Results

Sixty-nine meibum samples from 69 individuals were included in the analysis: 24 non-MGD, 24 mild-to-moderate MGD, and 21 severe MGD. Mean RCE/WE was 0.29 in non-MGD, 0.14 in mild-to-moderate MGD (P = 0.038 vs. non-MGD, 51% lower), and 0.07 in severe MGD (P = 0.16 vs. mild-to-moderate MGD, 52% lower; P = 0.002 vs. non-MGD, 76% lower). Mean Rald/WE was 0.00022 in non-MGD, 0.00083 in mild-to-moderate MGD (P = 0.07 vs. non-MGD, 277% higher), and 0.0024 in severe MGD (P = 0.003 vs. mild-to-moderate MGD, 190% higher; P < 0.001 vs. non-MGD, 992% higher).

Conclusions

RCE/WE was lowest and Rald/WE was highest in the severe MGD cohort, suggesting that these meibum constituent molar ratios may result from the pathophysiology associated with MGD and can impact ocular surface lipid and tear film homeostasis. These findings may potentially help identify targets for MGD treatment.

Dry Eye Disease Associated with Meibomian Gland Dysfunction: Focus on Tear Film Characteristics and the Therapeutic Landscape

Meibomian gland dysfunction (MGD) is highly prevalent and is the leading cause of evaporative dry eye disease (DED). MGD is characterized by a reduction in meibum secretion and/or a change in meibum composition that results in the disruption of the tear film lipid layer and an increase in the tear film evaporation rate. Excessive evaporation causes tear film instability, desiccation, tear hyperosmolarity, inflammation, and apoptosis of ocular surface cells, resulting in a continuous cycle of DED. The primary treatment goal for DED associated with MGD is to restore the tear film lipid layer and decrease evaporation, thereby reducing ocular signs and symptoms. The management of MGD includes home care options (eyelid hygiene, warming eye masks, ocular lubricants) and office-based treatments (manual expression, microblepharoexfoliation, thermal pulsation, intense pulsed light, intraductal probing). Topical ophthalmic prescription medications attempt to alter various factors that may contribute to DED (e.g., inflammation, bacterial growth, inadequate tear production). In this review, clinical evidence regarding available treatments and emerging therapies from randomized studies in patients with DED associated with MGD is summarized. Although some treatment modalities have been evaluated specifically for DED patients with MGD, large-scale randomized controlled trials are needed to confirm efficacy and safety in this patient population. Currently, there are no approved prescription pharmacologic treatments specifically indicated for DED associated with MGD, and those medications approved for the treatment of DED do not target the key driver of the disease (i.e., excessive evaporation). NOV03 (perfluorohexyloctane; under review with the US Food and Drug Administration) is the most advanced emerging therapy for DED associated with MGD and has demonstrated statistically significant improvements in both signs and symptoms in randomized controlled trials. Development of novel pharmacotherapies will improve therapeutic options and allow for a more individualized approach for patients with DED associated with MGD.

Topical Review: Optometry in Nepal-Clinical Practice, Research Advances, and Challenges

SIGNIFICANCE

This article reviews educational standard, clinical practice, research advances, and challenges associated with optometry in Nepal and provides critical considerations for contemporary and new optometry programs in countries with similar socioeconomic status and health care systems.Optometry education started in Nepal in 1998 with the primary objective of addressing the unmet needs of eye health and vision care in the country. Over the last two decades, this program has made significant contributions to facilitating and improving the delivery of quality eye care and establishing the nation's eye health system as an exemplary model in South Asia. Despite the positive impact in a short time, optometry education and the profession continue to face several challenges, including a shortage of training resources and facilities, poor quality control and regulation of practice standards, lack of professional recognition, limited pathways for entry to governmental jobs via the national public service commission, and limited clinical and academic opportunities in existing eye care programs. This article reviews current education and clinical practice standards, highlights research advances, and discusses present and future challenges in sustaining and improving the quality of education and advancing the scope of practice of optometry in Nepal. Given the limited access to primary eye care services in Nepal, appropriate professional recognition and integration into the national health system, and initiatives targeted at improving the delivery of optometry education in alignment with successful international models may provide a long-sought solution to making eye care services accessible to all and lowering the burden of visual impairment in the country.

Urea and ocular surface: Synthesis, secretion and its role in tear film homeostasis

Urea has been detected in the tear film, aqueous humor, and vitreous of the eye. While most of the urea in the aqueous humor and vitreous is considered to be an ultrafiltrate from the blood vessels, the presence of urea transporters and urea-synthesizing enzymes in the lacrimal gland, meibomian glands, conjunctiva, and cornea suggests ureagenesis occurring at the ocular surface. This review summarizes the distribution and function of urea transporters, urea and its synthesizing enzymes at the ocular surface to analyze their role in the tear film homeostasis. Urea transporters (UT)-A- and UT-B-as well as the enzymes arginase I, II, and agmatinase are located at the ocular surface. Urea concentration on the ocular surface is influenced by blood urea concentration, the amount of urea released by the tear fluid, tear evaporation, and arginase concentration in the tears. There are conflicting reports on the relationship between tear and plasma urea levels though a linear correlation exists between their levels. Urea protects the ocular surface from osmotic stress and is thought to maintain a lipid-water interface in the lamellar phase of the tear film. The reduction of urea levels in the tears of patients with evaporative dry eye suggests its possible role in tear film stability. Other than mitigating osmotic stress, urea has hydrating properties as well. Animal studies have demonstrated the healing effects of urea on the corneal epithelium. Future studies examining the variations in urea content in tears from different ocular surfaces, at different times of day, and under different environmental conditions would further solidify the role of urea in tear film stability.

The role of sphingolipids in meibomian gland dysfunction and ocular surface inflammation

Inflammation occurs in response to tissue injury and invasion of microorganisms and is carried out by the innate and adaptive immune systems, which are regulated by numerous chemokines, cytokines, and lipid mediators. There are four major families of bioactive lipid mediators that play an integral role in inflammation - eicosanoids, sphingolipids (SPL), specialized pro-resolving mediators (SPM), and endocannabinoids. SPL have been historically recognized as important structural components of cellular membranes; their roles as bioactive lipids and inflammatory mediators are recent additions. Major SPL metabolites, including sphingomyelin, ceramide, ceramide 1-phosphate (C1P), sphingosine, sphingosine 1-phosphate (S1P), and their respective enzymes have been studied extensively, primarily in cell-culture and animal models, for their roles in cellular signaling and regulating inflammation and apoptosis. Less focus has been given to the involvement of SPL in eye diseases. As such, the aim of this review was to examine relationships between the SPL family and ocular surface diseases, focusing on their role in disease pathophysiology and discussing the potential of therapeutics that disrupt SPL pathways.

Lipid metabolism disorders contribute to hepatotoxicity of ICR mice induced by nitrosamines exposure

Health risks caused by crucial environmental carcinogens N-nitrosamines triggered ubiquitous attention. As the liver exerted vital function through metabolic process, lipid metabolism disorders have been confirmed as potential drivers for toxicological effects, and the mechanisms of lipid regulation related to hepatotoxicity induced by N-nitrosamines remained largely unclear. In this study, we comprehensively explored the disturbance of hepatic lipid homeostasis in mice induced by nitrosamines. The results implied that nitrosamines exposure induced hepatotoxicity accompanied by liver injury, inflammatory infiltration, and hepatic edema. Lipidomics profiling analysis indicated the decreased levels of phosphatidic acids (PA), phosphatidylcholines (PC), phosphatidylethanolamines (PE), lyso-phosphatidylcholines (LPC), lyso-phosphatidylethanolamines (LPE), diacylglycerols (DAG) and triacylglycerols (TAG), the elevation of ceramides (Cer) and decomposition of free fatty acids (FFA) in high-dose nitrosamines exposure group. Importantly, nitrosamines exposure promoted fatty acid oxidation (FAO) by facilitating fatty acid uptake and decomposition, together with the upregulation of genes associated with FAO accompanied by the activation of inflammatory cytokines TNF-α, IL-1β and NLRP3. Furthermore, fatty acid translocase CD36-mediated fatty acid oxidation was correlated with the enhancement of oxidative stress in the liver caused by nitrosamines exposure. Overall, our results contributed to the new strategies to interpret the early toxic effects of nitrosamines exposure.

Relationships between ocular surface sphingomyelinases, Meibum and Tear Sphingolipids, and clinical parameters of meibomian gland dysfunction

PURPOSE

Sphingolipids (SPL) are a class of lipid molecules that play important functional and structural roles in our body and are a component of meibum. Sphingomyelinases (SMases) are key enzymes in sphingolipid metabolism that hydrolyze sphingomyelin (SM) and generate ceramide (Cer). The purpose of this study was to examine relationships between ocular surface SMases, SPL composition, and parameters of Meibomian gland dysfunction (MGD).

METHODS

Individuals were grouped by meibum quality (n = 25 with poor-quality, MGD, and n = 25 with good-quality, control). Meibum and tears were analyzed with LC-MS to quantify SPL classes: Cer, Hexosyl-Ceramide (Hex-Cer), SM, Sphingosine (Sph), and sphingosine 1-phosphate (S1P). SMase activity in tears were quantified using a commercially available 'SMase assay'. Statistical analysis included multiple linear regression analyses to assess the impact of SMase activity on lipid composition, as well as ocular surface symptoms and signs of MGD.

RESULTS

Demographic characteristics were similar between the two groups. nSMase and aSMase levels were lower in the poor vs good quality group. aSMase activity in tears negatively correlated with SM in meibum and tears and positively with Sph in meibum and S1P in tears. Lower SMase activity were associated with signs of MGD, most notably Meibomian gland dropout.

CONCLUSION

This study suggests that individuals with MGD have reduced enzymatic activity of SMases in tears. Specifically, individuals with poor vs good meibum quality were noted to have alterations in SMase activity and SPL composition of meibum and tears which may reflect deviations from normal lipid metabolism in individuals with MGD.

Silicone hydrogel contact lenses retain and document ocular surface lipid mediator profiles

CLINICAL RELEVANCE

A leading reason for patients to abandon their contact lenses is discomfort. Mechanisms and biomarkers for lens discomfort remain to be elucidated.

BACKGROUND

Physical stress and tear film interaction are likely factors for lens discomfort. Lipid mediators are generated from polyunsaturated fatty acids. They regulate ocular surface physiology and pathophysiology, are constituents of human tears and may interact with contact lenses. This study set out to determine if hydrogel lenses and silicone hydrogel lenses interact with tear film polyunsaturated fatty acids and polyunsaturated fatty acids-derived mediators.

METHODS

In vitro incubations, rat experiments and analysis of worn human lenses assessed polyunsaturated fatty acids and lipid mediator interactions with lenses. Silicone hydrogel and hydrogel lenses were incubated with lipid mediators and polyunsaturated fatty acids up to 24 hours. Rats were fitted with custom silicone hydrogel lenses and basal tears collected. Silicone hydrogel lenses worn for 2 weeks were obtained from 57 human subjects. Tear and lens lipidomes were quantified by mass spectrometry.

RESULTS

Silicone hydrogel lenses retained polyunsaturated fatty acids and lipid mediators within 15 minutes in vitro. Lenses contained 90% of total polyunsaturated fatty acids and 83-89% of total monohydroxy fatty acids by 12 hours. Retention correlated with polarity of lipid mediators and lipophilic properties of silicone hydrogel lenses. Polyunsaturated fatty acids and lipid mediators such as lipoxygenase- and cyclooxygenase-derived eicosanoids were present in tears and worn lenses from rats. Worn silicone hydrogel lenses from human subjects established robust and lens-type specific lipidomes with high levels of polyunsaturated fatty acids, lipoxygenase-pathway markers and subject-specific differences in lipoxin A₄ and leukotriene B₄.

CONCLUSION

Worn silicone hydrogel lenses rapidly retain and accumulate tear polyunsaturated fatty acids and lipid mediators. Marked subject and lens type differences in the lipidome may document changes in ocular surface physiology, cell activation or infection that are associated with lens wear. If contact lens discomfort and adverse events induce specific tear and lens fatty acid and lipid mediator profiles warrants further studies.

Candidate Molecular Compounds as Potential Indicators for Meibomian Gland Dysfunction

Meibomian gland dysfunction (MGD) is the leading cause of dry eye disease throughout the world. Studies have shown that several molecules in meibum, including but not limited to interleukins, amino acids, cadherins, eicosanoids, carbohydrates, and proteins, are altered in meibomian gland dysfunction compared with healthy normal controls. Some of these molecules such as antileukoproteinase, phospholipase A2, and lactoperoxidase also show differences in concentrations in tears between meibomian gland dysfunction and dry eye disease, further boosting hopes as candidate biomarkers. MGD is a complex condition, making it difficult to distinguish patients using single biomarkers. Therefore, multiple biomarkers forming a multiplex panel may be required. This review aims to describe molecules comprising lipids, proteins, and carbohydrates with the potential of serving various capacities as monitoring, predictive, diagnostic, and risk biomarkers for meibomian gland dysfunction.