The Diurnal Secretory Characteristics of Individual Meibomian Glands

Treatment of Meibomian Gland Dysfunction by Classical Eyelid Hygiene Measures With and Without Additional Lipid Substitution for Tear Film Stabilization

OBJECTIVE

This study aimed to document the treatment success of eyelid hygiene with liposomal suspension using new diagnostic tools and to determine whether additional lipid substitution provided measurable benefits in meibomian gland dysfunction.

METHODS

A single-center controlled, partially single masked study was conducted. Group A used eyelid hygiene only, whereas group B additionally applied a liposomal eye spray. Subjective perception using the Ocular Surface Disease Index (OSDI) questionnaire, measurement of tear film osmolarity, noninvasive tear film break-up time, assessment of the lipid layer, meibography, inspection of lid margins, assessment of the meibomian glands, and measurement of matrix-metallopeptidase-9 were collected at baseline and after 12 weeks.

RESULTS

Eighty-two patients were included and randomized into two groups. Both groups showed a decrease in OSDI score ( P <0.001), an increase in lipid layer thickness ( P <0.001), significant improvement in the degree of loss of meibomian glands ( P <0.001), in the damage pattern of the eyelid margins ( P <0.001), in the quality of meibomian gland secretion, and in matrix-metallopeptidase-9 after 12 weeks.

CONCLUSIONS

Our study confirms the success of treatment with eyelid hygiene measures using a liposomal suspension. The additional benefit of lipid substitution was not significant after 12 weeks of treatment.

A Novel Rabbit Model of Meibomian Gland Dysfunction-Induced Dry Eye

Purpose

The objective of this three-phase study was to develop a model of mild to moderate evaporative dry eye to be used to evaluate tear film stability endpoints during product development.

Methods

Rabbits were sedated prior to ophthalmic cautery of meibomian gland orifices. The orifices of eyelid meibomian glands were half-cauterized (to yield obstruction of every other meibomian gland orifices), fully cauterized (to yield obstruction of all meibomian gland orifices), or untreated. The primary outcome measures were model repeatability, tear film break-up time (TBUT), non-invasive tear break-up time (NIBUT), and model confirmation with daily artificial tears. Other examinations included Draize score, tear production, fluorescein staining, eschar, and histopathology.

Results

Cauterization was well tolerated in all phases. In phase I, TBUT was significantly decreased compared to baseline on days 14, 21, 28, and 35 in fully cauterized meibomian gland orifices but not in half-cauterized meibomian gland orifices. In phase II, both NIBUT and TBUT were similarly and significantly reduced in the fully cauterized meibomian gland orifices compared to the control eyes on days 7, 9, 14, and 28. In the confirmation phase, the administration of eye drops significantly improved NIBUT over the course of the study.

Conclusions

A rabbit model of dry eye was successfully and safely created through the obstruction of meibomian gland orifices by cautery, which yielded a significant reduction in tear film stability. A quantifiable benefit of artificial tears relative to untreated control was demonstrated within the model.

Translational Relevance

When the model is deployed, the utility and efficacy of therapeutic formulations can be evaluated.

Refrigeration reduces instillation discomfort of a 0.09% cyclosporine A solution

SIGNIFICANCE

Topical cyclosporine A (CsA) for the treatment of dry eye disease is often associated with instillation discomfort, which may negatively influence patient adherence to therapy. This study found that refrigerating topical CsA reduced instillation discomfort compared with instillation of warm CsA. Thus, refrigerating CsA prior to instillation may improve patient experience when using CsA to manage dry eye disease.

PURPOSE

This study aimed to quantify instillation discomfort associated with cold or warm instillation of a 0.09% CsA.

METHODS

Forty participants with symptomatic aqueous deficient dry eye were enrolled. A drop of cold (4°C) CsA was instilled in one eye, and a drop of warm (23°C) CsA was instilled in the other eye. The order and eye receiving the cold drop were randomized. Participants rated the discomfort of each eye (0, no discomfort; 10, maximal discomfort) prior to drop instillation, immediately post-instillation, and at each subsequent minute for 10 minutes. Area under the curve was used to quantify cumulative discomfort.

RESULTS

Forty participants (39.6 ± 18.9 years old, 82% female) completed the study. A majority of participants (n = 24, 60%) experienced reduced cumulative discomfort with cold CsA, whereas the remainder experienced minimal difference (n = 10, 25%) or increased cumulative discomfort (n = 6, 15%). For those with reduced discomfort (n = 24), cumulative discomfort associated with cold instillation (median, 11.5 [2.2, 20.0]) was significantly lower (p<0.01) than cumulative discomfort associated with warm instillation (median, 17.5 [11.2, 32.2]). Cold instillation was associated with a median reduction of 1 discomfort point immediately post-instillation and at all subsequent time points (all p≤0.04, but not significant at t = 10), compared with warm instillation.

CONCLUSIONS

Up to 60% of participants found that cold instillation of CsA solution induced less discomfort than warm instillation, lasting up to 9 minutes post-instillation. In contrast, although 15% of participants found reduced discomfort with warm instillation, the magnitude of discomfort associated with warm instillation was not significantly different than cold instillation.

Temporal variations in meibomian gland structure-A pilot study

PURPOSE

To investigate whether there is a measurable change in meibomian gland morphological characteristics over the course of a day (12 h) and over a month.

METHODS

The study enrolled 15 participants who attended a total of 11 study visits spanning a 5-week period. To assess diurnal changes in meibomian glands, seven visits were conducted on a single day, each 2 h apart. For monthly assessment, participants attended an additional visit at the same time of the day every week for three consecutive weeks. Meibography using the LipiView® II system was performed at each visit, and meibomian gland morphological parameters were calculated using custom semi-automated software. Specifically, six central glands were analysed for gland length ratio, gland width, gland area, gland intensity and gland tortuosity.

RESULTS

The average meibomian gland morphological metrics did not exhibit significant changes during the course of a day or over a month. Nonetheless, certain individual gland metrics demonstrated notable variation over time, both diurnally and monthly. Specifically, meibomian gland length ratio, area, width and tortuosity exhibited significant changes both diurnally and monthly when assessed on a gland-by-gland basis.

CONCLUSIONS

Meibomian glands demonstrated measurable structural change over short periods of time (hours and days). These results have implications for innovation in gland imaging and for developing precision monitoring of gland structure to assess meibomian gland health more accurately.

Evaluation of Meibomian gland structure and appearance after therapeutic Meibomian gland expression

CLINICAL RELEVANCE

Evaluating how Meibomian glands can change in appearance has the potential to advance the understanding of Meibomian gland health and may lead to enhanced diagnosis and therapy.

BACKGROUND

This work aimed to investigate Meibomian gland appearance after therapeutic Meibomian gland expression.

METHODS

Fifteen subjects attended three study visits over a two-week period. Meibography was performed before and after therapeutic Meibomian gland expression, the following day, and 2 weeks after expression. Six central glands were used to calculate Meibomian gland morphological parameters such as gland length ratio, gland width, gland area, gland tortuosity, and gland contrast. A custom semi-automated image analysis software was used to calculate Meibomian gland metrics. Furthermore, a high-resolution imaging system was developed to capture clear images of the Meibomian glands, free of any artefacts, which were used for precise calculations of Meibomian gland contrast.

RESULTS

The expression procedure had a significant impact on Meibomian gland contrast and length ratio immediately afterwards. The least square mean difference (95% CI) from baseline for Michelson contrast was -0.006 (-0.010, -0.001) and -1.048 (-2.063, -0.033) for simple contrast. The least square mean ratio of the gland length ratio immediately after the expression to baseline was 0.758 (0.618, 0.931).

CONCLUSIONS

Following therapeutic expression, Meibomian glands exhibit reduced brightness and length. However, within 24 h, they appear to recover and return to their baseline state, indicating a relatively short recovery time. This sheds light on whether meibography is solely focused on capturing gland structure or if it also captures acinar activity. The hyperreflective properties of lipids suggest that the decrease in contrast observed after expression could be attributed to a reduction in the visualisation of acini activity. A decrease in Meibomian gland length ratio implies that the loss of gland structure following treatment may be indicative of a temporary structural alteration.

Efficacy and safety of AZR-MD-001 selenium sulfide ophthalmic ointment in adults with meibomian gland dysfunction: A vehicle-controlled, randomized clinical trial

PURPOSE

Meibomian gland dysfunction (MGD) is a chronic progressive disease with downstream effects on ocular signs and symptoms. AZR-MD-001 is a selenium sulfide ophthalmic ointment that was investigated as a potential treatment option for patients with MGD.

METHODS

A Phase 2, multi-center, double-masked, parallel group study was conducted across 29 sites, with 245 patients randomized 1:1:1 to AZR-MD-001 0.5%, AZR-MD-001 1.0% or vehicle applied to the lower eyelid, twice weekly. Patients were eligible for the trial if they presented with signs and symptoms of MGD. Co-primary efficacy endpoints were the changes from baseline in number of open glands (Meibomian Glands Yielding Liquid Secretion [MGYLS] score) and patient-reported ocular surface symptoms (Ocular Surface Disease Index [OSDI] total score) at Month 3. Efficacy outcomes were captured at Day 14, Month 1.5 and Month 3. Safety and tolerability were assessed for treatment-emergent adverse events (TEAEs).

RESULTS

AZR-MD-001 0.5% (n = 82 patients) treatment resulted in significant improvements in MGYLS score, with patients experiencing an average increase from baseline of 4.2 and 2.4 open glands secreting meibum for the drug and vehicle, respectively (p < 0.001) and from baseline a mean OSDI total score improvement of 7.3 and 3.8 for the drug and vehicle, respectively (p < 0.05). Most TEAEs were mild and transient, with 3 serious adverse events (SAEs) reported with AZR-MD-001 (none related to study drug).

CONCLUSIONS

Co-primary endpoints were met for AZR-MD-001 0.5% at Month 3, with a statistically significant improvement in the signs and symptoms of MGD. AZR-MD-001 was safe and well tolerated.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03652051, ANZCTR Registration Number: AZ201801.

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

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

High-fat intake reshapes the circadian transcriptome profile and metabolism in murine meibomian glands

Background

Nutritional and food components reshape the peripheral clock and metabolism. However, whether food challenges affect the circadian clock and metabolism of meibomian glands (MGs) has not been fully explored. This study was designed to analyze alterations in the rhythmic transcriptome and metabolism of MGs of murine fed a balanced diet or a high-fat diet (HFD).

Methods

Male C57BL/6J mice were maintained on a 12/12 h light/dark cycle and fed ad libitum on normal chow (NC) or HFD for 4 weeks. MGs were collected from sacrificed animals at 3-h intervals throughout a 24-h circadian cycle. The circadian transcriptome of MGs was analyzed via bioinformatics approaches using high-throughput RNA sequencing (RNA-seq). In addition, circadian oscillations of lipid components in MGs were analyzed.

Results

Meibomian glands displayed robust transcriptome rhythmicity. HFD feeding significantly altered the circadian transcriptome profile of MGs-including composition and phase-and spatiotemporally affected the enriched signaling pathways. In addition, HFD feeding significantly altered the normal rhythmic oscillations of lipid components in MGs.

Conclusion

Our data show that HFD significantly affects MGs' rhythmicity, which reveals a high sensitivity of MGs' clocks to lipid composition in food.

Evaluation of meibomian gland dysfunction in type 2 diabetes with dry eye disease: a non-randomized controlled trial

BACKGROUND

The purpose of this investigation was to evaluate the morphology and physiological function of the meibomian glands between type 2 diabetics with dry eye disease (DED) and control subjects. Doing so will help to better reveal the pathologic mechanisms of meibomian gland dysfunction (MGD) and DED in type 2 diabetes mellitus (T2DM).

METHODS

Ninety subjects were divided into the following four groups: DM-DED group: T2DM patients with DED (n = 30); DM control group: DM patients without DED (n = 18); DED group: DED patients without DM (n = 26); and normal control group: normal subjects (n = 16). All participants administered the ocular surface disease index (OSDI) questionnaire, tear meniscus height (TMH), noninvasive Keratograph tear film break-up time (NIKBUT), Schirmer I test (SIT), corneal fluorescein staining (CFS), eyelid margin abnormality examinations, meibum quality and meibomian gland (MG) dropout evaluations.

RESULTS

The percentage of MG dropout in the upper and lower lids was significantly higher in the DM-DED group than the DED group (P < 0.05 or P < 0.01). However, there was no significant difference in other MG parameters between these two groups. Oppositely, Significant difference was observed in all of MG parameters except MG dropout in the lower lids comparing DM group with normal controls (P < 0.05 or P < 0.01). While the SIT values decreased in the DM-DED group compared to the DED group (P < 0.05), no significant differences were found in the values of other tear parameters.

CONCLUSIONS

The higher prevalence and increased severity of MGD was found in patients with both T2DM and DED compared to those only with DED.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR1800019939, date of registration December 9, 2018, prospectively registered.

The Lowly Chalazion

Chalazia are localized cysts of chronic lipogranulomatous inflammation arising from the obstruction of sebaceous glands of the eyelid tarsal plate, including the Meibomian gland (deep chalazion) or Zeis gland (superficial chalazion). This disease entity is differentiated from the hordeolum (stye), an acute purulent localized swelling of the eyelid often associated with an eyelash follicle, Zeis gland, or Moll gland obstruction and infection. Ambiguously, the chalazion, hordeolum, and blepharitis are commonly categorized and described on a continuum in the literature. While it is one of the most common eyelid disorders across all age demographics, the chalazion remains largely understudied and pathophysiological, epidemiological, and therapeutic findings exist fragmented in the literature. We discuss current understandings of the chalazion and provide current best practice guidelines supported by clinical anecdotal evidence.

Topographical Distribution and Phenotype of Resident Meibomian Gland Orifice Immune Cells (MOICs) in Mice and the Effects of Topical Benzalkonium Chloride (BAK)

Meibomian gland orifices (MGOs) are located along the eyelid margin and secrete meibum into the tear film. The profile of resident innate immune cells (ICs) at this site is not well understood. The distribution and phenotype of resident ICs around MGOs in mice was investigated and herein defined as MGO-associated immune cells (MOICs). The effect of topical 0.1% benzalkonium chloride (BAK) on MOICs was also assessed. Eyelids from healthy CD11ceYFP and Cx3cr1gfp/gfp mice aged three or seven months were compared. ICs were identified as CD11c+, Cx3cr1+, and MHC-II+ using four-colour immunostaining and confocal microscopy. MOIC density was variable but clustered around MGOs. There were more CD11c+ MOICs in three-month-old compared with seven-month-old mice (three-month-old: 893 ± 449 cells/mm2 vs. seven-month-old: 593 ± 493 cells/mm2, p = 0.004). Along the eyelid margin, there was a decreasing gradient of CD11c+ MOIC density in three-month-old mice (nasal: 1003 ± 369 cells/mm2, vs. central: 946 ± 574 cells/mm2, vs. temporal: 731 ± 353 cells/mm2, p = 0.044). Cx3cr1-deficient mice had two-fold fewer MHC-II+ MOICs, suggesting a role for Cx3cr1 receptor signaling in meibomian gland surveillance. CD11c+ MOIC density was lower in BAK-exposed eyes compared to saline-treated controls, suggesting a change in homeostasis. This study provides novel insight into resident ICs located at MGOs, and their contribution to MG homeostasis.

Quantitative analysis of morphological and functional features in Meibography for Meibomian Gland Dysfunction: Diagnosis and Grading

BACKGROUND

To explore the performance of quantitative morphological and functional analysis in meibography images by an automatic meibomian glands (MGs) analyser in diagnosis and grading Meibomian Gland Dysfunction (MGD).

METHODS

A cross-sectional study collected 256 subjects with symptoms related to dry eye and 56 healthy volunteers who underwent complete ocular surface examination was conducted between January 1, 2019, and December 31, 2020. The 256 symptomatic subjects were classified into MGD group (n = 195) and symptomatic non-MGD group (n = 61). An automatic MGs analyser was used to obtained multi-parametric measurements in meibography images including the MGs area ratio (GA), MGs diameter deformation index (DI), MGs tortuosity index (TI), and MGs signal index (SI). Adjusted odds ratios (ORs) of the multi-parametric measurements of MGs for MGD, and the area under the receiver operating characteristic (AUC-ROC) curves of multi-parametric measurements for MGD diagnosing and grading were conducted.

FINDINGS

When consider age, sex, ocular surface condition together, the estimated ORs for DI was 1.62 (95% CI, 1.29-2.56), low-level SI was 24.34 (95% CI, 2.73-217.3), TI was 0.76(95% CI, 0.54-0.90), and GA was 0.86 (95% CI, 0.74-0.92) for MGD. The combination of DI-TI-GA-SI showed an AUC = 0.82 (P < 0.001) for discriminating MGD from symptomatic subjects. The DI had a higher AUC in identifying early-stage MGD (grade 1-2), while TI and GA had higher AUCs in moderate and advanced stages (grade 3-5). Merging DI-TI-GA showed the highest AUCs in distinguish MGD severities.

INTERPRETATION

The MGs area ratio, diameter deformation, tortuosity and signal intensity could be considered promising biomarkers for MGD diagnosis and objective grading.

FUNDING

This work was supported by the Key-Area Research and Development Program of Guangdong Province (No. 2019B010152001), the National Natural Science Foundation of China under Grant (81901788) and Guangzhou Science and Technology Program (202002030412).

Profiling of non-polar lipids in tears of contact lens wearers during the day

PURPOSE

This study explored whether the non-polar lipids in the human tear fluid lipidome show diurnal variation with and without contact lens wear. It also addressed the relationship between changes in ocular comfort during the day with the level of non-polar lipids.

METHODS

Tear samples were collected in the morning and evening with and without contact lenses using fine glass capillary tubes and were analysed by chip-based nano-electrospray ionization tandem mass spectrometric techniques. Tear levels of cholesteryl esters (CE), wax esters (WE) and triacylglycerides (TAG) were quantified.

RESULTS

TAG 48:0, 52:0 and WE 26:0/16:0, and 27:0/17:0 increased from morning to evening. TAG 52:2, WE 21:0/16:0, 21:0/18:1 and 28:0/18:1 decreased during the day when no lenses were worn. CE 21:0 was the only non-polar lipid that increased from morning to evening in contact lens wear. WE 21:0/16:0 and 27:0/17:0 were lower in the morning in contact lens wear compared to no lens wear (p ≤ 0.05). The level of non-polar lipids did not correlate with ocular comfort at the end of the day.

CONCLUSION

Even though the level of some of non-polar lipid species changed from morning to evening the total level of major tear non-polar lipids remained unchanged during the day with and without contact lens wear. The effect of change in the quantity and structure of lipid species on tear stability and ocular comfort warrants more investigation.

Effect of meibomian gland morphology on functionality with applied treatment

PURPOSE

To determine how Meibomian gland (MG) morphology affects MG function by means of gland expression with the effect of treatment.

METHODS

Fifteen patients (aged 31.6 ± 13.1 years) from a dry eye clinic diagnosed with MG dysfunction had their 365 lower lid MGs visualised with a slit-lamp biomicroscopy. Using infrared meibography (Oculus K5m), MG length, width and tortuosity were objectively measured. Each MG was expressed and the meibum graded (0=clear fluid, 1=cloudy fluid, 2= particulate fluid, 3=inspissated, or 4 = no expression) to determine its functionality. Participants had functionality repeated each time following a sequence of a warm compress, debridement, and forcible expression after 5 min.

RESULTS

Just over 10 % of complete length MGs gave clear expression, while about 5% did not express at all, with most expressed meibum being particulate in nature. In contrast, the majority of partial length glands gave inspissated expression (38 %), with 32 % not expressing at all. No MG of <10 % length expressed. MG gland length was correlated with gland expression (r=-0.507, p < 0.001) and MG tortuosity (r=-0.129, p < 0.001), but not MG width (r=-0.090, p = 0.167). Regardless of MG length, warm compress increased the quality of expression (p < 0.002). Debridement further improved expression in partial MGs (p = 0.003), but not forcible expression (p = 0.529).

CONCLUSIONS

Length is the key functional morphology metric of lower lid MGs. Warm compress and massage increase the quality of expression in all, but the shortest glands and patients with partial length glands also benefit from debridement.

Meibomian Gland Morphology Is a Sensitive Early Indicator of Meibomian Gland Dysfunction

PURPOSE

To investigate the relationship between meibomian gland (MG) morphology and clinical dry eye tests in patients with meibomian gland dysfunction (MGD).

DESIGN

Cross-sectional study.

SUBJECTS

Total 538 MGD patients and 21 healthy controls.

METHODS

MG loss on meibography images of upper (UL) and lower lids (LL) was graded on a scale of 0 (lowest degree of MG loss) to 3. MG length, thickness, and interglandular space in the UL were measured. Clinical tests included meibum expression and quality, tear film break-up time, ocular staining, osmolarity, Schirmer I, blink interval timing, and Ocular Surface Disease Index (OSDI) questionnaire.

RESULTS

Mean UL and LL meibogrades were significantly higher in MGD patients compared to controls (P < .001 for UL and LL). The sensitivity and specificity of the meibograde as a diagnostic parameter for MGD was 96.7% and 85%, respectively. Schirmer I was significantly increased in MGD patients with meibograde 1 compared to patients with meibograde 0, 2, and 3 in the UL (P < .05). MG thickness increased with higher meibograde (P < .001). MG morphology correlated significantly but weakly with several clinical parameters (P < .05). OSDI did not correlate with any MG morphologic parameter.

CONCLUSIONS

Grading of MG loss using meibograde effectively diagnoses MGD. Compensatory mechanisms such as increased aqueous tear production and dilation of MGs make early detection of MGD difficult by standard clinical measures of dry eye, whereas morphologic analysis of MGs reveals an early stage of MGD, and therefore represents a complementary clinical parameter with diagnostic potential.

Clinical relationship of meibometry with ocular symptoms and tear film stability

PURPOSE

To evaluate the relationship between meibometry with both ocular symptoms and tear film stability by: (1) to find out whether meibometry is able to differentiate between dry eye symptomatic and asymptomatic subjects classified by standardized dry eye questionnaires (OSDI and McMonnies), and (2) to assess the clinical relationship between meibometry with both tear break-up time (BUT) and maximum blink interval (MBI).

METHODS

140 Patients were recruited for the study. Using Meibometer MB550, five curves were generated for each patient. Subjects performed OSDI and McMonnies questionnaires and were stratified following a two- and a three-subgroup stratification for each questionnaire. BUT/MBI were repeated three times (by video recordings), and they were determined by counting their frames.

RESULTS

Subjects grouped by OSDI showed a trend to present lower meibometry values as the OSDI score were higher (ANOVA, p≤0.044). For McMonnies questionnaire this was only true for the two-subgroup stratification (ANOVA, p=0.04), but not for three-subgroup stratification (one-way ANOVA, p=0.30). On the other hand, meibometry values showed a statistical correlation with both BUT (r=0.305, p<0.001) and MBI (r=0.265, p<0.001). When the sample was divided in three groups regarding BUT value (≤5s, between 5 and 10s and≥10s), significant differences of meibometry values were found between BUT subgroups (p=0.008).

CONCLUSION

Meibometer MB550 can discriminate asymptomatic from dry eye symptomatic patients. Furthermore, there is a relationship between meibometry and the tear film stability.

TFOS DEWS II Tear Film Report

The members of the Tear Film Subcommittee reviewed the role of the tear film in dry eye disease (DED). The Subcommittee reviewed biophysical and biochemical aspects of tears and how these change in DED. Clinically, DED is characterized by loss of tear volume, more rapid breakup of the tear film and increased evaporation of tears from the ocular surface. The tear film is composed of many substances including lipids, proteins, mucins and electrolytes. All of these contribute to the integrity of the tear film but exactly how they interact is still an area of active research. Tear film osmolarity increases in DED. Changes to other components such as proteins and mucins can be used as biomarkers for DED. The Subcommittee recommended areas for future research to advance our understanding of the tear film and how this changes with DED. The final report was written after review by all Subcommittee members and the entire TFOS DEWS II membership.

Rethinking dry eye disease: a perspective on clinical implications

Publication of the DEWS report in 2007 established the state of the science of dry eye disease (DED). Since that time, new evidence suggests that a rethinking of traditional concepts of dry eye disease is in order. Specifically, new evidence on the epidemiology of the disease, as well as strategies for diagnosis, have changed the understanding of DED, which is a heterogeneous disease associated with considerable variability in presentation. These advances, along with implications for clinical care, are summarized herein. The most widely used signs of DED are poorly correlated with each other and with symptoms. While symptoms are thought to be characteristic of DED, recent studies have shown that less than 60% of subjects with other objective evidence of DED are symptomatic. Thus the use of symptoms alone in diagnosis will likely result in missing a significant percentage of DED patients, particularly with early/mild disease. This could have considerable impact in patients undergoing cataract or refractive surgery as patients with DED have less than optimal visual results. The most widely used objective signs for diagnosing DED all show greater variability between eyes and in the same eye over time compared with normal subjects. This variability is thought to be a manifestation of tear film instability which results in rapid breakup of the tearfilm between blinks and is an identifier of patients with DED. This feature emphasizes the bilateral nature of the disease in most subjects not suffering from unilateral lid or other unilateral destabilizing surface disorders. Instability of the composition of the tears also occurs in dry eye disease and shows the same variance between eyes. Finally, elevated tear osmolarity has been reported to be a global marker (present in both subtypes of the disease- aqueous-deficient dry eye and evaporative dry eye). Clinically, osmolarity has been shown to be the best single metric for diagnosis of DED and is directly related to increasing severity of disease. Clinical examination and other assessments differentiate which subtype of disease is present. With effective treatment, the tear osmolarity returns to normal, and its variability between eyes and with time disappears. Other promising markers include objective measures of visual deficits, proinflammatory molecular markers and other molecular markers, specific to each disease subtype, and panels of tear proteins. As yet, however, no single protein or panel of markers has been shown to discriminate between the major forms of DED. With the advent of new tests and technology, improved endpoints for clinical trials may be established, which in turn may allow new therapeutic agents to emerge in the foreseeable future. Accurate recognition of disease is now possible and successful management of DED appears to be within our grasp, for a majority of our patients.