Comparing meibomian gland visibility on optical coherence tomography and Keratograph 5M images using objective and subjective grading methods

PURPOSE

To investigate if there is a visible difference in meibomian gland (MG) length between images captured with the Visante optical coherence tomography (OCT; wavelength = 1,310 nm) and the OCULUS Keratograph 5M (K5M; wavelength = 880 nm).

METHODS

Adults between 18 and 40 years were recruited. Baseline dry eye disease was evaluated with the Standard Patient Evaluation of Eye Dryness (SPEED) and tear meniscus height and tear breakup time with the K5M. Right upper and lower eyelid MGs were imaged with the K5M and Visante OCT. Each image was graded with the 0 to 3 meiboscore scale. The central 5 MGs were evaluated with ImageJ for percent gland length visibility.

RESULTS

Thirty participants were analyzed with a median (interquartile range [IQR]) age of 23.0 (5.0) years (53.3 % female). Overall, participants were asymptomatic and had normal tear films. Meiboscores based on K5M and Visante OCT was significantly different for the lower eyelid (0[1] vs 1[2]; p = 0.007) but not the upper eyelid (0[1] vs 0[1]; p = 1.00). The mean percent gland visibility of the upper eyelid (82.7[9.6] vs 75.2[13.5]; p < 0.001) and the lower eyelid (81.2[12.7] vs 64.1[17.6]; p < 0.001) were significantly greater on the Visante OCT than the K5M images, respectively.

CONCLUSION

OCT images had significantly greater percent visible MG lengths than the K5M images. This suggests viable segments of the MGs may be missed with typical imaging, which may explain how it is possible that studies have found less post-treatment MG atrophy.

Models for Meibomian gland dysfunction: In vivo and in vitro

Meibomian gland dysfunction (MGD) is a chronic abnormality of the Meibomian glands (MGs) that is recognized as the leading cause of evaporative dry eye worldwide. Despite its prevalence, however, the pathophysiology of MGD remains elusive, and effective disease management continues to be a challenge. In the past 50 years, different models have been developed to illustrate the pathophysiological nature of MGD and the underlying disease mechanisms. An understanding of these models is crucial if researchers are to select an appropriate model to address specific questions related to MGD and to develop new treatments. Here, we summarize the various models of MGD, discuss their applications and limitations, and provide perspectives for future studies in the field.

Morphological and functional characteristics of the meibomian gland in pediatric patients with epiblepharon

BACKGROUND

To observe morphologic and functional changes in meibomian glands in pediatric patients with and without lower eyelid epiblepharon.

METHODS

In this prospective observation study, 55 eyes of 55 patients( 24 males, 31 females; mean age ± SD,9.82 ± 2.59 years; range 6-14 years) and 60 eyes of 60 controls ( 32 males, 28 females; mean age ± SD,10.57 ± 2.75 years; range 6-14 years) were included. The following tests were performed: eyelid margin abnormality by slit-lamp examination, measurement of noninvasive keratographic break-up time (NIKBUT), grading of absence of meibomian gland (meibography score) assessed with noncontact meibography, morphologic changes of meibomian glands (thinning, dilatation and distortion), tear production by the Schirmer 1 test, and grading of meibum quality and meibomian gland expressibility.

RESULTS

The morphologic changes in meibomian glands were more common in the epiblepharon group (56.36%) than in the control group (28.33%) (p = 0.002). The meibum quality was worse in the epiblepharon group than in the control group (p = 0.009), and the NIKBUT was significantly shorter in the epiblepharon group than in the control group (p = 0.012). There was no significant difference in the Schirmer 1 test, meibomian gland expressibility, eyelid margin abnormality score or total meibography score between the two groups. Morphologic changes in the meibomian glands in the upper eyelids (38.18%) were more common than those in the lower eyelids (20%) (p = 0.036) in the epiblepharon group, and the meibography score was higher in the upper eyelids than in the lower eyelids (p = 0.001).

CONCLUSION

There are morphological and functional changes in meibomian glands in pediatric patients with lower eyelid epiblepharon. Although the inverted eyelashes were located in the lower eyelid, morphological changes in the meibomian glands were more common in the upper eyelid.

Factors affecting long-term changes of meibomian gland in MGD patients

PURPOSE

To explore the long-term course of patients with meibomian gland dysfunction (MGD), and to analyse potential factors affecting the recovery of meibomian gland (MG) dropout.

METHODS

Seventy-nine MGD patients (79 eyes) aged 36.03±15.78 years old who underwent more than one year of follow-up were enrolled in this retrospective study. Corneal fluorescein staining (CFS), tear meniscus height (TMH), noninvasive breakup time (NIBUT), and noncontact meibography at baseline and last visit were collected and analysed. Then an automatic MG analyzer was used to measure the morphological and functional parameters of MGs, including their area ratio (AR), tortuosity index (TI), and signal index (SI). The patients whose AR increased by more than 5% were defined as MG improvement, and AR decreased by more than 5% was MG worsening.

RESULTS

A total of 79 patients (79 eyes) were assessed with at least 1-year of follow-up. More than 1/3 of MGD patients (27 eyes, 34.2%) underwent MG improvement, and 30.4% of MGs became worsened. Age (P=0.002), gender (P<0.001), IPL treatment (P=0.013), the change of CFS (P=0.0015), and the recovery of SI (P=0.035) showed significant differences among different recovery groups. Age(P<0.001), female sex (P=0.003), ΔCFS (P<0.001), AR at baseline (P<0.001) were negative correlation with AR recovery, and the change of SI (P=0.003) and IPL treatment (P=0.003) had a positive correlation with it. Among them, age (P=0.038), the change of CFS (P=0.004), and AR at baseline (P=0.007) were confirmed as negatively correlated factors predicting the long-term change of the MG.

CONCLUSION

Although the MGD treatment has continued for more than 1 year, only 34.2% of MGD patients were observed to undergo MG improvement. Younger patients and patients with better CFS recovery seem to have more opportunities to improve their MGs.

Histopathologic alterations in the eyelid after Hughes tarsoconjunctival flap: loss of Meibomian glands with preservation of accessory lacrimal glands

A 71-year-old female with invasive squamous cell carcinoma of the lower eyelid involving the ocular surface underwent surgical excision with negative margins and a subsequent reconstruction. The posterior lamellar defect was reconstructed with a Hughes tarsoconjunctival flap, and the anterior lamellar defect was reconstructed by advancing the lower eyelid skin. Three years later, the patient presented with signs suspicious for recurrence involving the tarsoconjunctival graft: a nodule along the mucocutaneus junction, symblepharon, and forniceal shortening. Repeat scouting biopsies showed variable degrees of moderate to severe squamous dysplasia so the patient underwent a staged full thickness excision of the lower eyelid and involved conjunctiva followed by reconstruction. Direct immunofluorescence was not diagnostic for ocular cicatrcial pemphigoid. Permanent histopathologic sections did not show any carcinoma, but the full thickness excisions involving the prior Hughes tarsoconjunctival flap highlighted two notable alterations: the Meibomian glands were absent and the accessory lacrimal glands of Wolfring were transposed to the mucocutaneous junction of the reconstructed lower eyelid.

Age related changes in hyaluronan expression leads to Meibomian gland dysfunction

The prevalence of dry eye disease (DED) ranges from ∼5 to 50 % and its associated symptoms decrease productivity and reduce the quality of life. Approximately 85 % of all DED cases are caused by Meibomian gland dysfunction (MGD). As humans and mice age, their Meibomian glands (MGs) undergo age-related changes resulting in age related-MGD (ARMGD). The precise cause of ARMGD remains elusive, which makes developing therapies extremely challenging. We previously demonstrated that a hyaluronan (HA)-rich matrix exists surrounding the MG, regulating MG morphogenesis and homeostasis. Herein, we investigated whether changes to the HA matrix in the MG throughout life contributes towards ARMGD, and whether altering this HA matrix can prevent ARMGD. For such, HA synthase (Has) knockout mice were aged and compared to age matched wild type (wt) mice. MG morphology, lipid production, PPARγ expression, basal cell proliferation, stem cells, presence of atrophic glands and MG dropout were analyzed at 8 weeks, 6 months, 1 year and 2 years of age and correlated with the composition of the HA matrix. We found that as mice age, there is a loss of HA expression in and surrounding the MGs of wt mice, while, in contrast, Has1-/-Has3-/- mice present a significant increase in HA expression through Has2 upregulation. At 1 year, Has1-/-Has3-/- mice present significantly enlarged MGs, compared to age-matched wt mice and compared to all adult mice. Thus, Has1-/-Has3-/- mice continue to develop new glandular tissue as they age, instead of suffering MG atrophy. At 2 years, Has1-/-Has3-/- mice continue to present significantly larger MGs compared to age-matched wt mice. Has1-/-Has3-/- mice present increased lipid production, increased PPARγ expression and an increase in the number of proliferating cells when compared to wt mice at all-time points analyzed. Taken together, our data shows that a loss of the HA matrix surrounding the MG as mice age contributes towards ARMGD, and increasing Has2 expression, and consequently HA levels, prevents ARMGD in mice.

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.

Recent advances in age-related meibomian gland dysfunction (ARMGD)

Meibomian glands (MGs), located within the tarsal plate of the eyelid, secrete meibum which is the lipid-rich secretion necessary for stabilizing the tear film and preventing tear evaporation. Changes in the quality and quantity of meibum produced causes MG dysfunction (MGD), the leading cause of evaporative dry eye disease (EDED). MGD is an underdiagnosed disease and it is estimated that, in the US, approximately 70 % of the population over 60 have MGD. Three forms of MGD occur based on their meibum secretion: hyposecretory, obstructive, and hypersecretory MGD. The pathophysiology of MGD remains poorly understood, however aging is the primary risk factor. With age, MGs undergo various age-related changes, including decreased acinar basal cell proliferation, hyperkeratinization, MG atrophy, and eventual MG drop-out, leading to age-related MGD (ARMGD). Additionally, studies have suggested that MGs can suffer inflammatory cell infiltration and changes innervation patterns with aging, which could also contribute towards ARMGD. This review focuses on how the aging process affects the MG, and more importantly, how age-related changes to the MG can lead to MG atrophy and MG drop-out, ultimately leading to ARMGD. This review also highlights the most recent developments in potential therapeutic interventions for ARMGD.

Organotypic culture model of mouse meibomian gland as a screening platform for risk factors related to meibomian gland dysfunction

PURPOSE

Meibomian glands (MGs) are crucial for maintaining tear film stability and ocular surface health. Here, we aim to establish a novel organotypic culture model of MGs and explore the risk factors of MG dysfunction (MGD).

METHODS

We developed a novel organotypic culture model for MGs at the air-liquid interface. The viability and cell proliferation of MGs were assessed using CCK-8, immunofluorescence, and qPCR. Lipid accumulation was evaluated by Nile red staining and microscopic examination. Protein expression levels were evaluated by immunofluorescence and Western blot assay. EdU assay was employed to track the proliferation of acinar cells. The validity of the model was confirmed through culturing MGs from mice of different ages and incorporating certain drugs (Dex) into the culture system.

RESULTS

Utilizing the novel culture model, the MG tissue exhibited sustained viability, cellular division, and continuous production of lipids for a duration of 7 days. Lipid droplets formed were directly visualized using light field microscopy. Through the cultivation of aged mice's MGs, it was discovered that aging resulted in diminished proliferation and lipid synthesis, along with an aberrant increase in Krt10 expression. Further application of this model showed that Dex treatment diminished MG's proliferation and lipid synthesis. Finally, an in vivo study was conducted to provide additional confirmation of the phenomenon of Dex-induced abnormalities.

CONCLUSIONS

In this study, a stable organotypic culture model of the MGs was established. The organotypic culture model offers a valuable tool to investigate the pathophysiological mechanisms and facilitate drug screening for MG-related diseases.

Culture of primary human meibomian gland cells from surgically excised eyelid tissue

Meibomian gland dysfunction is one of the most common ocular diseases, with therapeutic treatment being primarily palliative due to our incomplete understanding of meibomian gland (MG) pathophysiology. To progress in vitro studies of human MG, this study describes a comprehensive protocol, with detailed troubleshooting, for the successful isolation, cultivation and cryopreservation of primary MG cells using biopsy-size segments of human eyelid tissue that would otherwise be discarded during surgery. MG acini were isolated and used to establish and propagate lipid-producing primary human MG cells. The primary cell viability during culture procedure was maintained through the application of Rho-associated coiled-coil containing protein kinase inhibitor (Y-27632, 10 μM) and collagen I from rat tails. Transcriptomic analysis of differentiated primary human MG cells confirmed cell origin and revealed high-level expression of many lipogenesis-related genes such as stearoyl-CoA desaturase (SCD), ELOVL Fatty Acid Elongase 1 (ELOVL1) and fatty acid synthase (FASN). Primary tarsal plate fibroblasts were also successfully isolated, cultured and cryopreserved. Established primary human MG cells and tarsal plate fibroblasts presented in this study have potential for applications in 3D models and bioengineered tissue that facilitate research in understanding of MG biology and pathophysiology.

Dysregulation of Lipid Metabolism in Aging Meibomian Glands and Its Molecular Markers

The main function of exocrine Meibomian glands (MGs) is to produce a lipid-rich secretion called meibum which plays a critical role in maintaining the ocular surface homeostasis of humans and most mammals. The chemical composition of meibum, and its quantity produced by MGs, largely determine whether it can fulfill its role successfully. Aging was frequently associated with the onset of various MG-related pathologies. The goal of this study was to determine how aging affects the chemical composition and quantity of meibum in mice, and identify possible molecular markers of aging. Unbiased, untargeted and targeted lipidomic evaluation of mouse MG lipids was conducted using liquid chromatography-high-resolution mass spectrometry, and the results were analyzed using Principal Component, Orthogonal Projections to Latent Structures Discriminant, and Partial Least Square Discriminant Analyses. We found that aging leads to dysregulation of lipid metabolism in MGs, changing the ratios of major classes of MG lipids (such as wax esters, triacylglycerols, and phospholipids) in a progressive manner. Several lipid species that belong to these groups of MG lipids are proposed as clear markers of aging in a mouse model.

The Effect of Oral Isotretinoin Therapy on Meibomian Gland Characteristics in Patients with Acne Vulgaris

INTRODUCTION

The aim of the study was to determine the effect of oral isotretinoin therapy on the functional and morphological condition of the anterior segment of the eye, with particular emphasis on the meibomian glands.

METHODS

Twenty-four patients (48 eyes) with a diagnosis of acne vulgaris were involved in the survey. All patients underwent a thorough ophthalmological examination at three time points: before therapy, 3 months after the start of therapy, and 1 month after the completion of isotretinoin therapy. The physical examination included the following elements: blink rate, analysis of the lid margin abnormality score (LAS), tear film break-up time (TFBUT) and Schirmer's test, meibomian gland loss (MGL), and the evaluation of the meibum quality score (MQS) and meibum expressibility score (MES). Additionally, the total score of an ocular surface disease index (OSDI) questionnaire was analysed.

RESULTS

In comparison with pretreatment values, significant increases in OSDI during and after the treatment (p = 0.003 and p = 0.004, respectively) were observed. Substantial deterioration during the treatment was observed for MGL (p < 0.0001), MQS (p < 0.001) and LAS (p < 0.0001), while an improvement in those parameters after isotretinoin cessation was observed (p = 0.006, p = 0.02 and p = 0.0003, respectively). The frequency of using artificial eye drops was positively associated with MGL during (Spearman's rank correlation coefficient (Rs) =  + 0.31; p = 0.03) and after the cessation of the therapy (Rs =  + 0.28; p = 0.04). Meibomian gland atrophy correlated significantly with MQS during (Rs =  + 0.29; p = 0.04) and after treatment (Rs =  + 0.38; p = 0.008). The decrease in TFBUT values correlated with increased LAS (Rs = - 0.31; p = 0.03) during the course of isotretinoin usage. We found no changes in Schirmer's test or blink rates.

CONCLUSION

Isotretinoin therapy leads to increased ocular complaints related to lipid tear film component dysfunction. This is due to reversible changes in meibomian gland morphology and function observed during drug usage.

Meibomian gland stem/progenitor cells: The hunt for gland renewal

Meibomian glands (MGs) secrete lipid (meibum) onto the ocular surface to form the outermost layer of the tear film. Proper meibum secretion is essential for stabilizing the tear film, reducing aqueous tear evaporation, and maintaining the homeostasis of the ocular surface. Atrophy of MG as occurs with aging, leads to reduction of meibum secretion, loss of ocular surface homeostasis and evaporative dry eye disease (EDED). Since MGs are holocrine glands, secretion of meibum requires continuous self-renewal of lipid-secreting acinar meibocytes by stem/progenitor cells, whose proliferative potential is dramatically reduced with age leading to MG atrophy and an age-related meibomian gland dysfunction (ARMGD). Understanding the cellular and molecular mechanisms regulating meibocyte stem/progenitor cell maintenance and renewal may provide novel approaches to regenerating MG and treating EDED. Towards that end, recent label retaining cell and lineage-tracing experiments as well as knock-out transgenic mouse studies have begun to identify the location and identities of meibocyte progenitor cells and potential growth and transcription factors that may regulate meibocyte renewal. In addition, recent reports have shown that ARMGD may be reversed by novel therapeutics in mice. Herein, we discuss our current understanding of meibocyte stem/progenitor cells and the hunt for gland renewal.

Meibomian gland development: Where, when and how?

The Meibomian gland (MG) is an indispensable adnexal structure of eye that produces meibum, an important defensive component for maintaining ocular homeostasis. Normal development and maintenance of the MGs is required for ocular health since atrophic MGs and disturbances in composition and/or secretion of meibum result in major ocular pathologies, collectively termed as Meibomian gland dysfunction (MGD). Currently available therapies for MGD merely provide symptomatic relief and do not treat the underlying deficiency of the MGs. Hence, a thorough understanding of the timeline of MG development, maturation and aging is required for regenerative purposes along with signaling molecules & pathways controlling proper differentiation of MG lineage in mammalian eye. Understanding the factors that contribute to the development of MGs, developmental abnormalities of MGs, and changes in the quality & quantity of meibum with developing phases of MGs are essential for developing potential treatments for MGD. In this review, we compiled a timeline of events and the factors involved in the structural and functional development of MGs and the associated developmental defects of MGs during development, maturation and aging.

The influence of overnight orthokeratology and soft contact lens on the meibomian gland evaluated using an artificial intelligence analytic system

PURPOSE

To test the changes of meibomian gland (MG) morphology using an artificial intelligence (AI) analytic system in asymptomatic children wearing overnight orthokeratology (OOK) and soft contact lens (SCL).

METHODS

A retrospective study was conducted including 89 participants treated with OOK and 70 participants with SCL. Tear meniscus height (TMH), noninvasive tear breakup time (NIBUT), and meibography were obtained using Keratograph 5 M. MG tortuosity, height, width, density, and vagueness value were measured using an artificial intelligence (AI) analytic system.

RESULTS

In an average of 20.80 ± 10.83 months follow-up, MG width of the upper eyelid significantly increased and MG vagueness value significantly decreased after OOK and SCL treatment (all P < 0.05). MG tortuosity of the upper eyelid significantly increased after OOK treatment (P < 0.05). TMH and NIBUT did not differ significantly pre- and post- OOK and SCL treatment (all P > 0.05). The results from the GEE model demonstrated that OOK treatment positively affected MG tortuosity of both upper and lower eyelids (P < 0.001; P = 0.041, respectively) and MG width of the upper eyelid (P = 0.038), while it negatively affected MG density of the upper eyelid (P = 0.036) and MG vagueness value of both upper and lower eyelids (P < 0.001; P < 0.001, respectively). SCL treatment positively affected MG width of both upper and lower eyelids (P < 0.001; P = 0.049, respectively) as well as MG height of the lower eyelid (P = 0.009) and tortuosity of the upper eyelid, (P = 0.034) while it negatively affected MG vagueness value of both upper and lower eyelids (P < 0.001; P < 0.001, respectively). However, no significant relationship was found between the treatment duration and TMH, NIBUT, MG morphological parameters in OOK group. SCL treatment duration negatively affected MG height of the lower eyelid (P = 0.002).

CONCLUSIONS

OOK and SCL treatment in asymptomatic children can influence MG morphology. The AI analytic system may be an effective method to facilitate the quantitative detection of MG morphological changes.

Influence of overnight orthokeratology on tear film and meibomian glands in myopic children: a prospective study

BACKGROUND

Orthokeratology lenses, which are worn overnight, are recommended for reducing myopia progression. They lie on the cornea and can influence the ocular surface by temporarily reshaping the corneal surface through a reverse geometry design. This study investigated the effect of overnight orthokeratology lenses on tear film stability and meibomian gland status in children aged 8-15 years.

METHODS

This prospective, self-controlled study included 33 children with monocular myopia who were prescribed orthokeratology lenses for at least one year. The experimental group (ortho-k group) comprised 33 myopic eyes. The control group comprised the emmetropic eyes of the same participants. Tear film stability and meibomian gland status were measured using a Keratograph 5M (Oculus, Wetzlar, Germany). Paired t-tests and Wilcoxon signed-rank tests were used to compare the data between the two groups.

RESULTS

At the one-year visit, the non-invasive first tear film break-up time (NIBUTf) values were 6.15 ± 2.56 s and 6.18 ± 2.61 s in the experimental and control groups, respectively. The lower tear meniscus height was 18.74 ± 0.05 μm and 18.65 ± 0.04 μm in these groups, respectively. No significant difference was observed in loss of meibomian glands or non-invasive average tear film break-up time between the experimental and control groups using Wilcoxon signed-rank tests.

CONCLUSIONS

The stability of the tear film and meibomian gland status were not significantly affected by wearing orthokeratology lenses overnight, indicating that continuous use of orthokeratology lenses for 12 months has a minimal effect on the ocular surface. This finding can help guide the clinical management of tear film quality with respect to the use of orthokeratology contact lenses.

Probing dietary triacylglycerol metabolism and meibogenesis in mice: A stable isotope-labeled tracer LC-MS/MS study

Exocrine Meibomian glands (MGs) play a central role in the ocular physiology and biochemistry by producing in situ and, mostly, de novo, a secretion (meibum), which is composed of a complex mixture of homologous lipids of various classes, in a metabolic pathway termed meibogenesis. Recent in vivo experiments with a number of mouse models demonstrated that inactivation of any of the major genes of meibogenesis led to alterations in the lipid composition of meibum and severe ocular and MG abnormalities that replicated various human ocular pathologies. However, the role of dietary lipids in meibogenesis, and in the onset and/or alleviation of these diseases, remains controversial. To uncover the role of dietary lipids, the metabolic transformations of a dietary lipid tracer - stable isotope-labeled glyceryl tri(oleate-1,2,3,7,8-¹³C₅) (¹³C₁₅-TO) - were investigated using LC-high-resolution TOF-MS/MS. We demonstrated that major metabolic transformations of the tracer occurred in the stomach and small intestines where ¹³C₁₅-TO underwent immediate and extensive transesterification into ¹³C₅- and ¹³C₁₀-substituted triacylglycerols of various lengths, giving a mixture of ¹³C-labeled compounds that remain virtually unchanged in the mouse plasma, liver, and white adipose tissue, but were almost undetectable in the feces. Importantly, the tracer and its metabolites were virtually undetectable in MGs, even after 4 weeks of daily supplementation. Notably, unbiased Principal Component Analysis of the data revealed no measurable changes in the overall chemical composition of meibum after the treatment, which implies no direct effect of dietary triacylglycerols on meibogenesis, and left their systemic effects as the most likely mechanism.

Is histogram manipulation always beneficial when trying to improve model performance across devices? Experiments using a Meibomian gland segmentation model

Meibomian gland dysfunction (MGD) is caused by abnormalities of the meibomian glands (MG) and is one of the causes of evaporative dry eye (DED). Precise MG segmentation is crucial for MGD-related DED diagnosis because the morphological parameters of MG are of importance. Deep learning has achieved state-of-the-art performance in medical image segmentation tasks, especially when training and test data come from the same distribution. But in practice, MG images can be acquired from different devices or hospitals. When testing image data from different distributions, deep learning models that have been trained on a specific distribution are prone to poor performance. Histogram specification (HS) has been reported as an effective method for contrast enhancement and improving model performance on images of different modalities. Additionally, contrast limited adaptive histogram equalization (CLAHE) will be used as a preprocessing method to enhance the contrast of MG images. In this study, we developed and evaluated the automatic segmentation method of the eyelid area and the MG area based on CNN and automatically calculated MG loss rate. This method is evaluated in the internal and external testing sets from two meibography devices. In addition, to assess whether HS and CLAHE improve segmentation results, we trained the network model using images from one device (internal testing set) and tested on images from another device (external testing set). High DSC (0.84 for MG region, 0.92 for eyelid region) for the internal test set was obtained, while for the external testing set, lower DSC (0.69-0.71 for MG region, 0.89-0.91 for eyelid region) was obtained. Also, HS and CLAHE were reported to have no statistical improvement in the segmentation results of MG in this experiment.

Spontaneous acinar and ductal regrowth after meibomian gland atrophy induced by deletion of FGFR2 in a mouse model

PURPOSE

We have demonstrated that deletion of fibroblast growth factor receptor 2 gene (Fgfr2) leads to Meibomian gland (MG) atrophy in an inducible conditional knockout mouse model, referred as Fgfr2^CKO. Herein, we investigated whether MG spontaneously recovers after atrophy in this model.

METHODS

Two months old Fgfr2^CKO mice were injected peritoneally once or twice of doxycycline (Dox) at 80 μg/gm of body weight to induce MG atrophy of various severities via Fgfr2 deletion. Recovery of acinar and ductal tissues was monitored by meibography, lipid staining and immunofluorescence against keratin-6a in MG whole-mount. Biomarkers for acinar and ductal differentiation and proliferation were also examined by immunostaining.

RESULTS

Single Dox injection in Fgfr2^CKO mice caused severe acinar and moderate ductal atrophy. Severe ductal shortening or loss occurred after second Dox injection, presumably related to the reported slower cycling of the ductal epithelia. Spontaneous acinar regrowth after atrophy was observed over a period of 60 days in both injection regimens. However, less robust acinar recovery was associated with more disrupted ductal structures in twice injected Fgfr2^CKO mice.

CONCLUSIONS

Our current findings further substantiate the role of FGFR2 in MG homeostasis, and suggest that FGFR2-signaling may provide a potential strategy for regenerating acini from age-related MG dysfunction in humans. Our data demonstrated that spontaneous MG recovery depends on the extent of ductal atrophy, suggesting that ductal epithelia may provide the progenitor cells for acinar regeneration. Nonetheless, the role of ductal tissue as the source of acinar progenitors awaits further investigation.

Effects of PPAR-γ and RXR-α on mouse meibomian gland epithelial cells during inflammation induced by latanoprost

The purpose of this study is to investigate the effects of latanoprost on the secretion of cytokines and chemokines from meibomian gland epithelial cells, and to evaluate the modulation of peroxisome proliferator-activated receptor γ (PPAR-γ) and retinoid X receptor α (RXR-α) during latanoprost-induced inflammation. Mouse meibomian gland epithelial cells were cultured in proliferation and differentiation medium, respectively. Cells were exposed to latanoprost, rosiglitazone (PPAR-γ agonist), or LG100268 (RXR-α agonist), respectively. The expression of IL-6, IL-1β, TNF-α, MMP-9, MCP-1, and CCL-5 were detected by real-time PCR and ELISA. The effect of latanoprost, rosiglitazone, LG100268, and inflammatory cytokines on the differentiation of meibocyte were evaluated by related gene expression and lipid staining. The expression of Keratin-1, 6, 17 protein was detected by western immunoblotting. The results showed that the above cytokines could be induced by latanoprost in meibomian gland epithelial cells. LG100268 and rosiglitazone could inhibit the production of IL-6 and TNF-α induced by latanoprost, respectively. Latanoprost suppressed the expression of differentiation-related mRNA through a positive feedback loop by enhancement of COX-2 expression via FP receptor-activated ERK signaling. The expression of Keratin-17 was upregulated by rosiglitazone and suppressed by LG100268. The application of IL-6 and TNF-α showed negative effects on lipid accumulation in meibomian gland epithelial cells. These results demonstrated that latanoprost could induce inflammation and suppress differentiation of mouse meibomian gland epithelial cells. The activation of PPAR-γ and RXR-α showed an anti-inflammatory effect, showing a potential role to antagonize the effect of latanoprost eyedrops on meibomian gland epithelial cells.

Immuno Tomography (IT) and Imaging Mass Cytometry (IMC) for constructing spatially resolved, multiplexed 3D IMC data sets

PURPOSE

We have previously used Immuno Tomography (IT) to identify label-retaining stem cell populations in the cornea and meibomian gland. While this method provides the unique ability to quantify stem cell populations comprised of 1-4 cells, the number of antigens that can be sequentially used to characterize these unique cells is limited by antigen stability after antibody stripping and re-probing. To address this deficiency, we have evaluated the capability of Imaging Mass Cytometry™ (IMC™) to generate multiplexed images using metal-conjugated antibodies to label IT plastic sections and generate 3-dimensional IMC data sets (3D IMC).

METHODS

K5-H2B-GFP mice, 56 days after doxycycline chase, were sacrificed and eyelid tissue processed for IT. A total of 400 serial, plastic sections, 2 μm thick, were then probed using metal-tagged antibodies specific for sox 9, collagen type I, E-cadherin, Ki67, GFP, αSMA, vimentin, and DNA intercalator. Multiplexed images were then generated using an Imaging Mass Cytometry system (Fluidigm®), and 3D reconstructions were assembled.

RESULTS

All 8 metal-labeled tags were detected and their images were successfully assembled into 3D IMC data sets. GFP-labeled nuclei were identified within the meibomian glands in comparable numbers to those previously reported for slow-cycling meibomian gland stem cells.

CONCLUSIONS

These findings demonstrate that IMC can be used on plastic sections to generate multiplexed, 3D data sets that can be reconstructed to show the spatial localization of meibomian gland stem cells. We propose that 3D IMC might prove valuable in more fully characterizing stem cell populations in different tissues.

Impact of aging on the pathophysiology of dry eye disease: A systematic review and meta-analysis

PURPOSE

Dry eye disease (DED) is a common age-related ocular surface disease. However, it is unknown how aging influences the ocular surface microenvironment. This systematic review aims to investigate how the aging process changes the ocular surface microenvironment and impacts the development of DED.

METHODS

An article search was performed in PubMed, EMBASE, and Web of Science. 44 studies reporting on age-related ocular changes and 14 large epidemiological studies involving the prevalence of DED were identified. 8 out of 14 epidemiological studies were further analyzed with meta-analysis. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) reporting guidelines were followed. Study-specific estimates (impact of aging on the prevalence of DED) were combined using one-group meta-analysis in a random-effects model.

RESULTS

Meta-analysis revealed the prevalence of DED in the elderly aged 60 years old or older was 5519 of 60107 (9.2%) and the odds ratio of aging compared to younger age was 1.313 (95% confidence interval [CI]; 1.107, 1.557). With increasing age, the integrity of the ocular surface and tear film stability decreased. Various inflammatory cells, including senescent-associated T-cells, infiltrated the ocular surface epithelium, lacrimal gland, and meibomian gland, accompanied by senescence-related changes, including accumulation of 8-OHdG and lipofuscin-like inclusions, increased expression of p53 and apoptosis-related genes, and decreased Ki67 positive cells.

CONCLUSIONS

The aging process greatly impacts the ocular surface microenvironment, consequently leading to DED.

Safety and efficacy of a low-level radiofrequency thermal treatment in an animal model of obstructive meibomian gland dysfunction

This study aimed to evaluate the safety and efficacy of a low-level radiofrequency thermal treatment in an obstructive MGD rabbit model. Meibomian gland orifices of the central two-thirds of the upper and lower eyelid margins were coagulated twice at 2-week intervals using a 5-MHz high-frequency electrosurgical unit. Sixteen eyes of eight rabbits were treated with one session of radiofrequency thermal treatment (radiofrequency group) and eight eyes of four rabbits were followed up without treatment (control group). Lid margin abnormality and corneal staining scores, histologic examination of the eyelids and meibombian gland, and meibography imaging were evaluated just before and 4 weeks after meibomian gland orifice closure and 4 weeks after radiofrequency thermal treatment. Lid margin abnormality score improved significantly for the upper and lower eyelids after radiofrequency thermal treatment (P < 0.001 for both eyelids). Corneal staining score remained unchanged in the radiofrequency group; however, the control group saw an increase at final follow-up. There was a significant improvement to almost baseline levels in the mean area of secretory acini in the radiofrequency group (P = 0.004). Additionally, meibography indicated an improvement in meibomian gland loss rate in the radiofrequency group. Low-level radiofrequency thermal treatment heating the inner and outer eyelid surfaces is safe and effective to treat obstructive MGD in a rabbit animal model of MGD.

The impact of contact lenses on meibomian gland morphology

Despite years of experience with contact lenses, controversy remains as to whether contact lenses adversely impact the meibomian glands (MG). This review summarizes the present body of evidence, showing that contact lens wear is associated with alterations in MG morphology (up to 80% higher gland atrophy compared to non-wearers) and qualitative changes in MG secretion. Key factors such as duration of contact lens wear, contact lens type (e.g., soft vs. rigid), edge design, and material modulus of elasticity are discussed in relation to the extent of MG morphological changes, the quality of MG secretion and other ocular surface parameters. Longitudinal studies of sufficient statistical power are needed to better understand how contact lens wear affects the MG, risk factors, and the clinical sequelae of these changes.

Analysis of Ocular Surface Characteristics and Incidence of Dry Eye Disease in Systemic Lupus Erythematosus Patients Without Secondary Sjögren's Syndrome

Objective

To investigate the differences in ocular surface characteristics, tear film quality, and the incidence of dry eye disease (DED) between Systemic Lupus Erythematosus (SLE) patients and healthy populations.

Methods

This age and gender-matched cross-sectional study included 96 SLE patients without secondary Sjögren's syndrome (SS) and 72 healthy subjects. The Ocular Surface Disease Index (OSDI), tear meniscus height (TMH), non-invasive tear film breakup time (NIKBUT), meibography, and tear film lipid layer grade were assessed. A receiver operative characteristic (ROC) curve was constructed to evaluate the predictive value of risk factors.

Results

Compared with the control subjects, a significantly greater proportion of SLE patients met the TFOS DEWS II DED diagnostic criteria (34.3 vs. 18.1%, P = 0.019). SLE patients without SS had higher OSDI scores [10.0 (4.5,18.0) vs. 5.0 (2.5,11.9), P < 0.001], and shorter NIKBUT [9.6 (6.6,15.0) vs. 12.3 (8.4, 15.8), P = 0.035]. Furthermore, TMH, Tear film lipid layer grade, and Meibomian gland (MG) dropout in SLE patients were worse than those in control subjects (all P < 0.05). For ROC analysis, the area under curve (AUC), sensitivity and specificity of prediction were 0.915, 75.8 and 92.1% for the combination of SLE disease activity index (SLEDAI), age and NIKBUT.

Conclusions

SLE patients without SS exhibited a higher risk for DED than healthy subjects, and the poorer Meibomian gland function in SLE patients may potentially contribute to the development of DED. The combined parameters of SLEDAI, age and NIKBUT showed a high efficiency for the diagnosis of DED in SLE patients, with practical clinical applications.

Evaluation of the meibomian glands using the tear interferometer wearing orthokeratology lenses

Background

To investigate the impact of orthokeratology wear on meibomian glands in Korean pediatric population using the tear interferometer.

Methods

Fifty-three orthokeratology wearers and 79 non-lens wearers were evaluated using the LipiView® II ocular surface interferometer which shows incomplete blink rate, average lipid layer thickness, and meiboscores.

Results

No significant differences in the incomplete blink rate and meiboscores for upper eyelids, but the lipid layer thickness and meiboscores for lower eyelids were significantly higher in the Ortho-K group than in the control group (p = 0.024 and 0.007, respectively). Correlation analysis showed no significant correlation between the duration of orthokeratology wear and the parameters measured by LipiView® (p > 0.05 for all). Among subgroups based on average duration of lens wear, the longer duration (≥ 24 months) subgroup showed higher meiboscores of lower eyelids (p = 0.011), but no other significant differences.

Conclusions

Ortho-K wearers showed no significant differences in the incomplete blink rate and meiboscores of upper eyelids, but they were associated with increased LLT and higher meiboscores of lower eyelids. Thorough examination and close monitoring of orthokeratology wearers is necessary. Prospective and observational studies are needed to further elucidate the relationship between Orthokeratology and meibomian glands.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02365-3.

Ocular surface alterations and changes of meibomian glands with meibography in type 1 diabetic children

PURPOSE

To observe the changes of the ocular surface and meibomian glands by non-contact meibography in patients with type 1 diabetic children.

METHODS

A total of forty-three patients with type 1 diabetic children and 43 age-matched healthy subjects were included in the study. The ocular surface disease index (OSDI) questionnaire, invasive tear film break-up time (TF-BUT), fluorescein staining of the ocular surface and Schirmer II test were performed for all participants. Ocular surface and lid margins were evaluated by slit lamp. Non-contact meibography was performed with the Phoenix-Meibography module in Sirius corneal topographic device.

RESULTS

Both groups consisted of 25 (58.1%) female and 18 (41.9%) male children and the mean age was 14.4 ± 2.5 years. In the T1DM group, the mean disease duration was 6.8 ± 3.1 years. The mean TF-BUT (p = 0.002) and Schirmer II test (p = 0.007) measurements were lower in the diabetic group than those of in controls. Total eyelid score (p = 0.027) and meibomian gland (MG) secretion score (p = 0.007) were significantly high in diabetic children. MG area loss was also significantly high in both lower and upper eyelid (p < 0.001). In morphological analyses of meibomian glands thinning, shortening and presence of ghost areas (p = 0.05, p = 0.027 and p = 0.000, respectively) were more common in the diabetic group. There was no correlation between both lower and upper eyelid meiboscores and disease duration (p = 0.51 and p = 0.61), BMI (p = 0.08 and p = 0.51), serum HbA1c level (p = 0.06 and p = 0.49) and IGF-1 SDS (p = 0.38 and p = 0.68).

CONCLUSION

The study revealed that the MG loss area increases and morphological alterations of meibomian glands occur in type 1 diabetic children. Disease duration and metabolic control of diabetes do not affect meibography measurements.

CLINICAL TRIALS REGISTRATION

The study was organized in accordance with the ethical standards settled by the Ethics Committee of Faculty of Medicine, Afyonkarahisar Health Sciences University.

TRIAL REGISTRATION NUMBER

2011-KAEK-2, 2021/106.

TRIAL REGISTRATION DATE

02.05.2021.

MicroRNA Therapy for Dry Eye Disease

Purpose: We tested the role of microRNA-328 in dry eye disease (DED). Benzalkonium chloride (BAC) has been used to induce DED in animal models. We first demonstrated that both BAC and hyperosmotic stress induced overexpression of miR-328 in corneal cells and then tested whether anti-miR-328 could be a new therapy. Methods: BAC was instilled to both eyes of 41 rabbits and 19 mice from day 0 to 21 to induce DED. Animals of each species were divided to receive topical instillation of saline or anti-miR-328 eye drops between day 8 and 21. The DED signs were assessed by corneal fluorescein staining, histological examination, apoptosis of corneal cells, and inflammatory cytokines in rabbit eyes. For mice, only corneal fluorescein staining was assessed for the therapeutic effects. The corneal fluorescein staining scores ranged from 0 of no staining to 4 of coalescent. Results: For the rabbits, the staining score was significantly reduced (P = 0.038) after the 14-day anti-miR-328 treatment (n = 42 eyes), but the score was not improved by saline treatment (n = 40 eyes). Furthermore, rabbit eyes treated with anti-miR-328 had thicker corneal epithelium (P = 9.4 × 10^-5), fewer apoptotic cells in corneal epithelium (P = 0.002), and stroma (P = 0.029) compared with the saline-treated eyes. Anti-miR-328 was more effective than saline to reduce the block of orifices of Meibomian glands, although such an effect was only marginally significant (P = 0.059). Similarly, anti-miR-328 was more effective than saline in reducing corneal staining in mouse eyes (P = 0.005). Conclusion: Overexpression of miR-328 may contribute to DED. Anti-miR-328 protects corneal cells and promotes re-epithelialization for DED treatment.

Evaluation of corneal, ocular surface, and meibomian gland changes in obstructive sleep apnea syndrome

PURPOSE

To evaluate the ocular surface, eyelid changes, meibomian gland morphology, corneal endothelial morphology, and corneal topographic measurements in patients with obstructive sleep apnea syndrome (OSAS).

METHODS

There were 47 patients diagnosed with OSAS and 47 healthy volunteers included in the study. Non-invasive tear break-up time (NITBUT), corneal topography, meibography, and specular microscopy were performed.

RESULTS

The mean ages of the study and control groups were 45.77±9.65 years and 44.26±8.54 years, respectively (P=0.229). The presence of floppy eye lid (17% vs. 0%; P=0.006) and lid margin abnormality score (1.09±0.8 vs. 0.21±0.51; P<0.001) were significantly different between the study and the control groups. There were insignificant differences between the groups in NITBUT and corneal topographic measurements, except for the ACT (556.96±42.4μm vs. 569±103μm, P=0.037). The mean endothelial cell density (CD) in the OSAS and control groups were 2609±259.96 and 2756±179 cells/mm², respectively (P=0.002). Meibomian gland loss in the lower and upper eyelids was significantly higher in the OSAS group (P<0.001 for both).

CONCLUSION

OSAS patients develop eyelid margin abnormalities, loss of meibomian glands, and morphological changes in the meibomian glands. A significant reduction in corneal endothelial CD indicates that systemic hypoxia in OSAS has an effect on the cornea.

A review of meibomian gland structure, function, and contact lens wear

PURPOSE

To provide a balanced literature review of the studies that have evaluated the effect of contact lenses on meibomian gland (MG) health.

METHODS

A PubMed.gov literature search was conducted on or before May 15, 2021. No other time constraints were applied. Search terms included the following: "meibomian gland(s)" plus "contact lens(es)" or "meibography" plus "contact lens(es)". Only full text articles written in English were considered. The reference lists of recovered papers were used to identify articles missed during the primary search. Included articles were required to discuss the impact of contact lenses on MG morphology or function and were graded according to the level of evidence presented.

RESULTS

The literature indicates that contact lenses impact MG function; however, the data are equivocal regarding contact lenses inducing MG structural changes. The literature likewise indicates that the mechanism(s) by which contact lenses impact the MGs are likely multifactorial. Recent data suggests that MGs may have some plasticity. Detected differences between studies likely stem from varied populations evaluated, study designs, and the duration of the evaluation periods.

CONCLUSIONS

With this literature review finding conflicting relationships between MG health and contact lens use, future longitudinal studies with standardized clinical MG assessments are needed to determine the true impact of contact lenses on MG health. Until these data are obtained, contact lens wearers should undergo a full MG evaluation, especially because recent data suggest that MG treatments may restore MG structure and function.

Expression of Acyl-CoA wax-alcohol acyltransferase 2 (AWAT2) by human and rabbit meibomian glands and meibocytes

PURPOSE

Previously, we showed that Acyl-CoA wax-alcohol acyltransferase 2 (AWAT2), an essential enzyme required for meibum wax ester synthesis, was not expressed by immortalized human meibomian gland epithelial cells (hMGEC) in culture. To begin to understand the mechanisms controlling AWAT2 expression, we have analyzed its expression in human and rabbit meibomian glands and cultured meibocytes.

METHODS

Rabbit meibocyte progenitor cells (rMPC) were first grown in Cnt-BM.1 basal medium (Cellntec) supplemented with rhEGF, FGF10, and ROCK inhibitor (Y-27632 dihydrochloride), and then passed at 70-80% confluency with Accutase. Differentiation of rMPC to meibocytes (rMC) was induced by removal of Y-27632 and addition of 1 mM calcium with and without PPARγ agonists. RNA from the tissue, primary, passaged rMPC and differentiated rMC were obtained for AWAT2 qPCR analysis. Proteins and cells were evaluated for western blotting and neutral lipid synthesis, respectively. For comparison, human meibomian glands were separated for RNA and protein analysis. hMGEC was cultured to collect RNA and protein.

RESULTS

Rabbit rMPCs were successfully grown, passaged, and differentiated, showing a significant increase in lipid droplet accumulation. AWAT2 RNA was highly expressed in tissue but showed a -16.9 log2 fold decrease in primary and passaged rMPCs and was not induced by differentiation to rMC. By comparison, human meibomian glands showed high expression of AWAT2, and hMGEC expressed non-detectable levels of AWAT2 transcripts or protein.

CONCLUSIONS

AWAT2 expression is lost in cultured rMPC and rMC suggesting that cells in culture do not undergo complete meibocyte differentiation and require yet to be identified culture conditions.

Eyelid blood vessel and meibomian gland changes in a sclerodermatous chronic GVHD mouse model

PURPOSE

To investigate pathological changes in blood vessels and meibomian glands (MGs) in the eyelids of sclerodermatous chronic graft-versus-host disease (cGVHD) model mice.

METHODS

We used an established major histocompatibility complex compatible, multiple minor histocompatibility antigen-mismatched sclerodermatous cGVHD mouse model. Blood vessels and MGs of eyelids from allogeneic bone marrow transplantation (allo-BMT) recipient mice and syngeneic bone marrow transplantation (syn-BMT) recipient mice were assessed by histopathology, immunohistochemistry and transmission electron microscopy. Peripheral blood samples from the recipients were examined by flow cytometry.

RESULTS

Allo-BMT samples showed dilating, tortuous and branching vessels and shrunk MGs in the eyelids; showed significantly higher expression of VEGFR2 (p = 0.029), CD133 (p = 0.016), GFP (p = 0.006), and α-SMA (p = 0.029) in the peripheral MG area; showed endothelial damage and activation, fibrotic change, and immune cell infiltration into MGs compared with syn-BMT samples. Fewer Ki-67⁺ cells were observed in allo- and syn-BMT samples than in wild-type samples (p = 0.030). Ultrastructural changes including endothelial injury and activation, fibroblast activation, granulocyte degranulation, immune cell infiltration into MGs, and necrosis, apoptosis of MG basal cells were found in allo-BMT samples compared with syn-BMT samples.

CONCLUSION

A series of our studies indicated that cGVHD can cause eyelid vessel and MGs changes, including endothelial injury and activation, neovascularization, early fibrotic changes, immune cell infiltration, MG basal cell necrosis and apoptosis, and resultant MG atrophy.

Alteration in meibum lipid composition and subjective symptoms due to aging and meibomian gland dysfunction

PURPOSE

To investigate the alteration in lipid composition of meibum, objective clinical signs, and subjective symptoms associated with aging and meibomian gland (MG) dysfunction (MGD).

METHODS

In 10 MGD patients [4 males/6 females, mean age: 65.6 ± 7.9 years (range: 50-79 years)] and 24 healthy volunteer subjects [young subjects: 6 males/6 females, mean age: 25.7 ± 3.8 years (range: 20-35 years), elderly subjects: 6 males/6 females, mean age: 58.4 ± 7.5 years (range: 50-79 years)], three objective clinical signs were evaluated: MG orifice obstruction, meibum score, and tear film lipid layer interference pattern. Subjective symptoms were analyzed via a 15-item questionnaire. After careful collection of meibum samples, comprehensive lipid analysis was performed via liquid chromatography-mass spectrometry. Data was analyzed via JMP® ver. 13 (SAS Institute, Inc., Cary, NC) statistical analysis software.

RESULTS

In the MGD patients and elderly subjects, there was a significant decrease in non-polar lipids such as cholesterol esters (ChEs), while a significant increase in polar lipids [cholesterol (Ch), (O-acyl)-ω-hydroxy fatty acid (OAHFA), and free fatty acid (FA)] in total lipids (Tukey-Kramer test: p < 0.05). Triglyceride was significantly increased only in MGD patients (p < 0.05). Symptom scores representative of vision quality (i.e., blurred vision/haziness) were significantly negatively-correlated with the ratio of the non-polar lipid ChE, while significantly positively correlated with the polar lipids Ch, OAHFA, and FA (Spearman's rank correlation coefficient: p < 0.05).

CONCLUSIONS

Our findings revealed that both MGD and aging affect the composition ratio of major meibum lipids, resulting in the appearance of subjective symptoms.

Change in rat meibomian gland structure with external pressure on the eyelid

PURPOSE

This study investigated structural changes in rat meibomian glands following repeated and sustained application of external pressure on the eyelids using a magnet and then subsequent removal of the external pressure.

METHODS

Twenty-eight Sprague-Dawley rats were used. The upper eyelid was externally compressed using a pair of magnets. One magnet was placed inside the upper eyelid, another was placed outside the eyelid, and varying periods of pressure were investigated. Untreated eyes were used as controls. Meibography was performed, and the transverse eyelid tissue sections were stained with hematoxylin and eosin and anti-cytokeratin 5 antibody at one hour, two and four weeks after removing the magnets.

RESULTS

Meibography showed increased meibomian gland loss (30.0 ± 5.0%), and tissue sections showed decreased area of secretory acini (0.04 ± 0.08 mm²) at one hour after applying external pressure using magnets versus in the control eyes (5.0 ± 5.0% and 0.08 ± 0.08 mm², respectively). On the other hand, there was no meibomian gland loss or reduction of the area of secretory acini at two and four weeks after removing the magnets in comparison with the control eyes.

CONCLUSIONS

Repeated and sustained application of external pressure on the eyelid could induce meibomian gland loss; however, this meibomian gland loss can be restored when the external pressure is removed. Therefore, the repeated application of external pressure on the eyelid is a safe treatment method for obstructive MGD.

Differential effects of dietary cholesterol and triglycerides on the lipid homeostasis in Meibomian glands

Exocrine Meibomian glands (MG) play a central role in the ocular surface physiology by producing meibum - a lipid secretion composed of cholesteryl esters (CE), cholesterol (Chl), triacylgycerols (TAG), waxes and other types of lipids. MG were previously shown to synthesize Meibomian lipids (ML) in situ via a complex array of reactions termed meibogenesis. However, questions remain about the role of dietary lipids in meibogenesis. To establish if dietary Chl (DC) and TAG (DT) can participate in meibogenesis, we studied mice whose diet was supplemented with trace amounts of deuterated Chl (2H-Chl) and 13C-labeled triolein (13C-TO), and the products of their biosynthetic transformations were analyzed using LC/MS. We demonstrated that 2H-Chl, but not 13C-TO, could be directly incorporated into meibum. Furthermore, 2H-Chl was esterified into MG-specific ultra long 2H-CE, which were vastly different from plasma CE and 2H-CE. The measured 2H-Chl/Chl and 2H-CE/CE ratios in meibum increased in a time-dependent manner reaching ∼5% and ∼1.2 %, respectively. The 2H-Chl/2H-CE ratio was about 3.5x higher than that for endogenous unlabeled Chl and CE, indicating accumulation of 2H-Chl in meibum. The elongation pattern of Meibomian 2H-CE closely replicated that of unlabeled CE. On the other hand, 13C-TO was not detected in any of the ML samples as an intact lipid or its metabolized/hydrolyzed products. We conclude that DC can be directly esterified into MG-specific CE, while DT undergo extensive catabolic transformations before reaching MG. These findings demonstrate that DC can have a direct impact on MG and ocular surface lipid homeostasis and pathophysiology.

Quantitative evaluation of lipid layer thickness and blinking in children with allergic conjunctivitis

Purpose

To quantitatively evaluate the lipid layer thickness (LLT) and blinking in children with or without allergic conjunctivitis (AC), and to compare those between the different types of AC.

Methods

For this case–control study, 81 children with symptomatic AC with an average age of 9.62 ± 2.67 years were enrolled and subdivided according to the subtypes of AC, including seasonal/perennial allergic conjunctivitis group and vernal keratoconjunctivitis (VKC)/atopic keratoconjunctivitis (AKC) group. Another 82 age-matched healthy children were enrolled as control group. All subjects underwent routine eye examination and measurements of LLT, the number of incomplete or total blinking, partial blinking rate by the LipiView interferometer over a 10-s period. Other ocular surface assessment included fluorescein tear breakup time (TBUT), lower tear meniscus height, meibomian gland loss (MGL), meibum expressibility and quality.

Results

Pediatric patients with AC had significant thinner LLT, shorter TBUT, decreased total blinking but increased partial blinking rate, especially in those with VKC/AKC (all P < 0.05). A significant deterioration of meibomian gland parameters was observed in AC group when compared with control subjects, demonstrated by severe upper and lower MGL, lid margin abnormalities, decreased meibum expressibility, and abnormal meibum quality, all of which were worse in the severe type of AC (all P < 0.05). Thinner LLT was significantly correlated with decreased TBUT (β = 3.666, P < 0.001) and severity of upper MGL (β =  − 7.701, P = 0.002).

Conclusion

Decreased LLT and blinking disorders in pediatric patients with AC may contribute to lipid layer deficiency in the long run, which should be considered and appropriately diagnosed for a more precise treatment.

Demographic and lifestyle risk factors of dry eye disease subtypes: A cross-sectional study

PURPOSE

To evaluate demographic and lifestyle factors associated with aqueous deficient and evaporative dry eye disease.

METHODS

A total of 1125 general public visitors (707 females, mean ± SD age, 33 ± 21, range 5-90 years) at the Royal Society Summer Science Exhibition were recruited in a cross-sectional study. A demographic and lifestyle factor questionnaire was administered, and dry eye symptomology (DEQ-5 score), ocular surface characteristics (conjunctival hyperaemia, and infrared meibography), and tear film parameters (tear meniscus height, non-invasive breakup time, and lipid layer grade) were evaluated for the left eye of each participant within a single session. The diagnostic criteria for dry eye disease subtypes were adapted from the rapid non-invasive dry eye assessment algorithm.

RESULTS

Overall, 428 (38%) participants fulfilled the diagnostic criteria for dry eye disease, 161 (14%) with aqueous deficient dry eye disease, and 339 (30%) with evaporative dry eye disease. Multivariate logistic regression demonstrated that advancing age, female sex, reduced sleep duration, higher psychological stress, and poorer self-perceived health status were independently associated with aqueous deficient dry eye disease (all p < 0.05). Significant risk factors for evaporative dry eye disease included advancing age, East and South Asian ethnicity, contact lens wear, increased digital device screen exposure, higher psychological stress, and poorer self-perceived health status (all p < 0.05).

CONCLUSIONS

Both subtypes of dry eye disease were associated with several unique and shared demographic and lifestyle factors. The findings of this study could inform future research design investigating the utility of targeted screening and risk factor modification for the prevention and management of dry eye disease.

Pathophysiology of Meibomian Glands - An Overview

Purpose: The meibomian glands are located in the tarsal plate of the upper and lower eyelid and are responsible for the production of a lipid-rich secretion, the meibum, which forms the outer component of the tear film. Meibomian gland dysfunction results in excessive evaporation of the tear film and is the leading cause of dry eye disease (DED). Despite the high prevalence of DED, the etiology of meibomian gland dysfunction is only basically understood. In addition, the molecular mechanisms of meibomian gland maturation and physiological function are currently the focus of research.Methods: A systematic literature search was performed using the main scientific databases, including all relevant published articles up to September 2020.Results: This article provides an overview of the current state of knowledge about meibomian gland stem cells, cell surface marker expression and PPARγ signaling, as well as the pathological causes of meibomian gland dysfunction.Conclusion: Androgen deficiency, hyperkeratinization, PPARγ signaling and inflammatory reactions including neutrophil extracellular traps (NETs) seem to be key factors within the pathological processes of the meibomian gland.

Triacylglycerol lipidome from human meibomian gland epithelial cells: Description, response to culture conditions, and perspective on function

Preliminary work has shown that select triacylglycerols (TAGs) are upregulated in a preclinical model of MGD, suggesting that TAGs may be an important outcome variable in research involving human meibomian gland epithelial cells (HMGECs). The purpose of this study was to explore the HMGEC TAG lipidome in culture conditions known to influence differentiation. HMGECs were differentiated in DMEM/F12 with 10 ng/ml EGF, FBS (2% or 10%), and rosiglitazone (0, 20, or 50 μM) for two or five days. Following culture, lipids were extracted, processed, and directly infused into a Triple TOF 5600 mass spectrometer (SCIEX, Framingham, MA) with electrospray ionization. MS and MS/MS^ALL spectra were acquired in the positive ion mode and performed with the SWATH technology. Only the TAGs that were present in all 48 samples were included in the analysis. Multiple regression techniques were utilized to assess the effects of each factor (FBS, rosiglitazone, and culture duration) on each expressed TAG. The HMGEC TAG lipidome consisted of 115 TAGs with 42-62 carbons and zero to 10 double bonds. Fatty acyl chains had 14 to 26 carbons and zero to five double bonds. C18:1 (oleic acid, 25/115, 21.7%) and C16:0 (palmitic acid, 16/115, 13.9%) were the most common fatty acids. FBS, rosiglitazone, and culture duration were significant predictors for 93 TAGs (80.9%) with R² values ranging from 0.20 to 0.77 (p < 0.05). FBS and rosiglitazone achieved significance (p < 0.05) for 80 (69.6%) and 67 TAGs (58.3%), respectively. Rosiglitazone demonstrated a selective upregulation of TAGs containing 16 or 18 carbons. Culture duration reached significance (p < 0.05) for only 36 TAGs (31.3%). When comparing the 10 most abundant C18:1-containing TAGs in meibum, FBS was a negative predictor for five TAGs (mean standardized coefficient [SC] = -0.58, p < 0.001), rosiglitazone was a positive predictor for six TAGs (mean SC = 0.41, p ≤ 0.03), and culture duration weakly influenced one TAG (SC = 0.27, p = 0.008). FBS and rosiglitazone, unlike culture duration, are powerful modulators of the TAG profile. Rosiglitazone induces changes that could be consistent with fatty acid synthesis, suggesting that quantifying the TAG lipidome could be an indirect measure of lipogenesis. Though both have been described as differentiating agents, FBS and rosiglitazone induce opposing effects on meibum-relevant TAGs. Culturing with rosiglitazone is associated with a TAG profile that is more consistent with the expected outcome of lipogenesis and with the profile observed in normal human meibum.

CLEAR - Anatomy and physiology of the anterior eye

A key element of contact lens practice involves clinical evaluation of anterior eye health, including the cornea and limbus, conjunctiva and sclera, eyelids and eyelashes, lacrimal system and tear film. This report reviews the fundamental anatomy and physiology of these structures, including the vascular supply, venous drainage, lymphatic drainage, sensory innervation, physiology and function. This is the foundation for considering the potential interactions with, and effects of, contact lens wear on the anterior eye. This information is not consistently published as academic research and this report provides a synthesis from all available sources. With respect to terminology, the report aims to promote the consistent use of nomenclature in the field, and generally adopts anatomical terms recommended by the Federative Committee for Anatomical Terminology. Techniques for the examination of the ocular surface are also discussed.

Depletion of Cholesteryl Esters Causes Meibomian Gland Dysfunction-Like Symptoms in a Soat1-Null Mouse Model

Previous studies on ablation of several key genes of meibogenesis related to fatty acid elongation, omega oxidation, and esterification into wax esters have demonstrated that inactivation of any of them led to predicted changes in the meibum lipid profiles and caused severe abnormalities in the ocular surface and Meibomian gland (MG) physiology and morphology. In this study, we evaluated the effects of Soat1 ablation that were expected to cause depletion of the second largest class of Meibomian lipids (ML)-cholesteryl esters (CE)-in a mouse model. ML of the Soat1-null mice were examined using liquid chromatography high-resolution mass spectrometry and compared with those of Soat1+/- and wild-type mice. Complete suppression of CE biosynthesis and simultaneous accumulation of free cholesterol (Chl) were observed in Soat1-null mice, while Soat1+/- mutants had normal Chl and CE profiles. The total arrest of the CE biosynthesis in response to Soat1 ablation transformed Chl into the dominant lipid in meibum accounting for at least 30% of all ML. The Soat1-null mice had clear manifestations of dry eye and MG dysfunction. Enrichment of meibum with Chl and depletion of CE caused plugging of MG orifices, increased meibum rigidity and melting temperature, and led to a massive accumulation of lipid deposits around the eyes of Soat1-null mice. These findings illustrate the role of Soat1/SOAT1 in the lipid homeostasis and pathophysiology of MG.

Comparative influence of differentiation and proliferation on gene expression in human meibomian gland epithelial cells

We recently discovered that by changing environmental signals, differentiated immortalized human meibomian gland epithelial cells (IHMGECs) de-differentiate into proliferating cells. We also discovered that following exposure to appropriate stimuli, these proliferative cells re-differentiate into differentiated IHMGECs. We hypothesize that this plasticity of differentiated and proliferative IHMGECs is paralleled by very significant alterations in cellular gene expression. To begin to test this hypothesis, we compared the gene expression patterns of IHMGECs during differentiation and proliferation. IHMGECs were cultured for four days in either differentiating or proliferating media. After four days of culture, cells were processed for the analysis of gene expression by using Illumina BeadChips and bioinformatic software. Our study identified significant differences in the expression of more than 9200 genes in differentiated and proliferative IHMGECs. Differentiation was associated with significant increases in the expression of specific genes (e.g. S100 calcium binding protein P; 7,194,386-fold upregulation) and numerous ontologies (e.g. 83 biological process [bp] ontologies with ≥100 genes were upregulated), such as those related to development, transport and lysosomes. Proliferation also led to a significant rise in specific gene expressions (e.g. cathelicidin antimicrobial peptide; 859,100-fold upregulation) and many ontologies (115 biological process [bp] ontologies with ≥100 genes were upregulated), with most of the highly significant ontologies related to cell cycle (z scores > 13.9). Our findings demonstrate that gene expression in differentiated and proliferative IHMGECs is extremely different. These results may have significant implications for the regeneration of HMGECs and the reversal of MG dropout in MG dysfunction.

Whole genome sequencing identified a 16 kilobase deletion on ECA13 associated with distichiasis in Friesian horses

BACKGROUND

Distichiasis, an ocular disorder in which aberrant cilia (eyelashes) grow from the opening of the Meibomian glands of the eyelid, has been reported in Friesian horses. These misplaced cilia can cause discomfort, chronic keratitis, and corneal ulceration, potentially impacting vision due to corneal fibrosis, or, if secondary infection occurs, may lead to loss of the eye. Friesian horses represent the vast majority of reported cases of equine distichiasis, and as the breed is known to be affected with inherited monogenic disorders, this condition was hypothesized to be a simply inherited Mendelian trait.

RESULTS

A genome wide association study (GWAS) was performed using the Axiom 670 k Equine Genotyping array (MNEc670k) utilizing 14 cases and 38 controls phenotyped for distichiasis. An additive single locus mixed linear model (EMMAX) approach identified a 1.83 Mb locus on ECA5 and a 1.34 Mb locus on ECA13 that reached genome-wide significance (pcorrected = 0.016 and 0.032, respectively). Only the locus on ECA13 withstood replication testing (p = 1.6 × 10- 5, cases: n = 5 and controls: n = 37). A 371 kb run of homozygosity (ROH) on ECA13 was found in 13 of the 14 cases, providing evidence for a recessive mode of inheritance. Haplotype analysis (hapQTL) narrowed the region of association on ECA13 to 163 kb. Whole-genome sequencing data from 3 cases and 2 controls identified a 16 kb deletion within the ECA13 associated haplotype (ECA13:g.178714_195130del). Functional annotation data supports a tissue-specific regulatory role of this locus. This deletion was associated with distichiasis, as 18 of the 19 cases were homozygous (p = 4.8 × 10- 13). Genotyping the deletion in 955 horses from 54 different breeds identified the deletion in only 11 non-Friesians, all of which were carriers, suggesting that this could be causal for this Friesian disorder.

CONCLUSIONS

This study identified a 16 kb deletion on ECA13 in an intergenic region that was associated with distichiasis in Friesian horses. Further functional analysis in relevant tissues from cases and controls will help to clarify the precise role of this deletion in normal and abnormal eyelash development and investigate the hypothesis of incomplete penetrance.

Relationship between eyelid margin irregularity and meibomian gland dropout

PURPOSE

To examine the relationship between lid margin abnormalities and meibomian gland loss in infrared meibography.

METHODS

This study was a retrospective chart review of 170 patients with dry eye disease. A correlation analysis between eyelid margin abnormalities and meibomian gland dropout in infrared meibography was performed using data from 141 eyes. We graded the following eyelid margin abnormalities: irregular lid margin, vascular engorgement, plugging, anterior placement of the mucocutaneous junction, exposed terminal duct, and presence of tattoos. Multiple regression analyses were performed with meiboscore (meibomian gland dropout grade) as the dependent variable and age, sex, lid margin abnormality grades, and total grading score of lid margin abnormalities as the covariates. In addition, Meibomian glands structure were examined in those with eyelid margin dimpling using meibography in 25 eyes.

RESULTS

In the multiple regression analysis, an irregular lid margin in the upper eyelid was associated with a higher meiboscore after controlling for age and sex (coefficients B = 1.379, p = 0.025). Other lid margin abnormalities did not significantly affect the meiboscore. In the lower eyelids, irregular lid margin (coefficients B = 0.602, p = 0.009) and total grading score of lid margin abnormality were associated with higher meiboscores (coefficients B = 0.100, p = 0.022). Of the 25 eyes with dimples, 21 (84%) showed focal or complete meibomian gland loss at the site.

CONCLUSIONS

Lid margin abnormalities were found to be associated with meibomian gland dropout.

Saturation of cholesteryl esters produced by human meibomian gland epithelial cells after treatment with rosiglitazone

PURPOSE

The purpose of this study was to compare the cholesteryl ester (CE) profiles expressed from human meibomian gland epithelial cells (HMGECs) in response to rosiglitazone-induced differentiation to that of normal human meibum.

METHODS

HMGECs were cultured with rosiglitazone (vehicle control, 20 μM, or 50 μM) and fetal bovine serum (FBS, 2% or 10%) for 2 days or 5 days. Following culture, lipid extracts were processed and analyzed by ESI-MSMS^ALL in positive ion mode. CEs were identified using both LipidView 1.2 and PeakView 2.2 (SCIEX, Framingham, MA) and compared to literature reports of CEs in normal human meibum.

RESULTS

There were 34 CEs with carbon number ranging from 14 to 34 detected from HMGECs. Across all conditions, HMGECs provided a CE profile that was 14.0% saturated, 60.6% monounsaturated, and 25.4% polyunsaturated. Culturing with 50 μM rosiglitazone and 2% FBS for 2 days resulted in the greatest number of upregulated saturated and monounsaturated CEs and downregulated polyunsaturated CEs. Five CEs were identified as being the most responsive to 50 μM rosiglitazone: CE 24:1, CE 28:1, CE 26:1, CE 18:1, and CE 22:1.

CONCLUSION

Although differences in the CE profile exist between meibum and HMGECs, rosiglitazone promotes upregulation of highly expressed meibum-relevant CEs and shifts the saturation level toward a more meibum-like profile. The use of rosiglitazone as a differentiating agent is recommended in HMGEC research, and analysis by ESI-MSMS^ALL is encouraged to differentiate meibum-relevant CEs from other nonpolar distractors detected by vital stains.

Meibomian Gland Dysfunction: What Have Animal Models Taught Us?

Studies have estimated that currently 344 million people worldwide and 16.4 million adults in the US have some form of dry eye disease (DED). It is believed that approximately 70% of DED cases are due to some form of evaporative dry eye, for which Meibomian gland dysfunction (MGD) is the major cause. Unfortunately, currently there is no effective treatment for MGD, and solely palliative care is available. Given the importance of MGD in DED, there has been a growing interest in studying Meibomian gland development, homeostasis and pathology, and, also, in developing therapies for treating and/or preventing MGD. For such, animal models have shown to be a vital tool. Much of what is known today about the Meibomian gland and MGD was learnt from these important animal models. In particular, canine and rabbit models have been essential for studying the physiopathology and progression of DED, and the mouse model, which includes different knockout strains, has enabled the identification of specific pathways potentially involved in MGD. Herein, we provide a bibliographic review on the various animal models that have been used to study Meibomian gland development, Meibomian gland homeostasis and MGD, primarily focusing on publications between 2000 and 2020.

Investigation of the effect of the dual orexin receptor antagonist almorexant on ophthalmological, spermatogenic, and hormonal variables in healthy male subjects

BACKGROUND/AIMS

The aim of this single-center, double-blind study was to investigate the effect of a 4-week once daily administration of 200 mg almorexant on tear film break-up time, spermatogenesis, hormone levels, and pancreatic elastase in stool in healthy male subjects.

METHODS

Almorexant 200 mg or matching placebo was administered in the evening for 4 weeks once daily to 56 healthy male subjects. Changes in ophthalmological variables, sperm composition, hormone levels, and pancreatic elastase levels in stool were evaluated periodically up to 8 weeks after discontinuation of drug administration. Blood samples for pharmacokinetic measurements were taken after 4 weeks to confirm compliance to study drug intake.

RESULTS

The results of this study revealed no treatment effects of almorexant, neither on tear film break-up time nor on other ophthalmological variables investigated during this study. Furthermore, spermatogenesis, hormones of the hypothalamic-pituitary-adrenal and -gonadal axes, and endocrine pancreatic secretion were shown to be not affected by a 4-week once daily administration of almorexant.

CONCLUSION

Almorexant was well tolerated and had no effect on the spectrum of pharmacodynamic variables assessed. Ophthalmology and testicular findings detected in preclinical studies were not observed in this clinical study. Therefore, these preclinical findings appear not to be relevant for humans and do not prevent from conducting larger clinical trials with either healthy subjects or patients.

Production of branched-chain very-long-chain fatty acids by fatty acid elongases and their tissue distribution in mammals

Although most mammalian fatty acids (FAs) are straight-chain, there also exist branched-chain FAs such as iso- and anteiso-FAs, especially in the meibomian glands. Meibum lipids, which are secreted from the meibomian glands and are important for dry eye prevention, contain abundant branched-chain lipids, such as cholesteryl esters and wax esters with chain-lengths of ≥C21 (very-long-chain; VLC). However, the exact tissue distribution of branched-chain lipids or the enzymes involved in the production of branched-chain VLCFAs has remained poorly understood. Here, we revealed that FA elongases ELOVL1, ELOVL3, and ELOVL7, of the seven mammalian ELOVL isozymes, elongated saturated branched-chain acyl-CoAs. ELOVL3 was highly active toward iso-C17:0 and anteiso-C17:0 acyl-CoAs and elongated them up to iso-C23:0 and anteiso-C25:0 acyl-CoAs, respectively. ELOVL1 elongated both iso- and anteiso-C23:0 acyl-CoAs to C25:0 acyl-CoAs. By establishing a liquid chromatography-tandem mass spectrometry method capable of separating branched- and straight-chain lipids, we showed that essentially all of the cholesteryl esters and 88% of the wax esters in the mouse meibomian glands are branched. In Elovl1 mutant mice, the levels of ≥C24:0 branched-chain cholesteryl esters and ≥C25:0 branched-chain wax esters were decreased, indicating that ELOVL1 indeed elongates branched-chain VLC acyl-CoAs in vivo. In addition, substantial amounts of ceramides containing branched-chain FAs were present in the skin, meibomian glands, and liver. Our findings provide new insights into the molecular mechanisms that create FA and lipid diversity.

A novel transillumination meibography device for in vivo imaging of mouse meibomian glands

PURPOSE

While mouse models of dry eye disease (DED) have been developed, studies evaluating the role of the meibomian glands limited by the inability to temporally document changes. In this report we describe the development of a novel mouse transillumination meibography device and assess the ability of this device to detect age-related changes in the meibomian glands of young and old mice.

METHODS

The mouse meibography device was comprised of a 3 mm wide right angle prism attached to broad spectrum light source by an optical fiber. Eyelids were then pulled over the prism using double tooth forceps and imaged using a stereomicroscope and low light level camera. Meibomian glands from four young and four old male, BALB/c mice were then imaged and analyzed using ImageJ.

RESULTS

In young mice, meibography documented the presence of 7-8 meibomian glands appearing as black and distinct eyelid structures with the length shorter in the lower eyelid compared to the upper eyelids. Eyelids of old mice showed apparent dropout of meibomian glands along with smaller and more irregularly shaped acini. The mean acini area of one meibomian gland was 0.088 ± 0.025 mm² in young mice and 0.080 ± 0.020 mm² in old mice (p = 0.564), but the Meibomian gland density was significantly lower in older mice (41.7 ± 6.4%, 27.3 ± 4.2%) (p = 0.021).

CONCLUSION

We have developed an in vivo meibography device that may prove useful in sequentially documenting changes during development of meibomian gland dysfunction and following treatment.