[Revisiting meibomian gland dysfunction]

Early Dry Eye Disease Onset in a NOD.H-2h4 Mouse Model of Sjögren's Syndrome

Purpose

To develop a mouse model of human dry eye disease (DED) for investigation of sex differences in autoimmune-associated dry eye pathology.

Methods

Ocular surface disease was assessed by quantifying corneal epithelial damage with lissamine green stain in the NOD.H-2^h4,IFNγ^−/−,CD28^−/− (NOD.H-2^h4 DKO) mouse model of Sjögren's syndrome (SS). Lacrimal gland function was assessed by tear volume quantification with phenol red thread and lacrimal gland inflammation (i.e., dacryoadenitis) was assessed by quantification of immune cell foci, flow cytometric analysis of immune cell composition, and expression of proinflammatory markers.

Results

The NOD.H-2^h4 DKO mouse model of SS exhibits greater age-dependent increases in corneal damage than in NOD.H-2^h4 parental mice and demonstrates an earlier disease onset in females compared to males. The severity of ocular surface disease correlates with loss of goblet cell density, increased conjunctivitis, and dacryoadenitis that is more pronounced in NOD.H-2^h4 DKO than NOD.H-2^h4 mice. B cells dominate lacrimal infiltrates in 16-week-old NOD.H-2^h4 and NOD.H-2^h4 DKO mice, but T helper cells and macrophages are also present. Lacrimal gland expression of proinflammatory genes, including the P2X7 and P2Y₂ purinergic receptors, is greater in NOD.H-2^h4 DKO than NOD.H-2^h4 mice and correlates with dacryoadenitis.

Conclusions

Our results demonstrate for the first time that autoimmune dry eye disease occurs in both sexes of NOD.H-2^h4 DKO and NOD.H-2^h4 mice, with earlier onset in female NOD.H-2^h4 DKO mice when compared to males of the same strain. This study demonstrates that both NOD.H-2^h4 and NOD.H-2^h4 DKO mice are novel models that closely resemble SS-related and sex-dependent DED.

Corneal haze post photorefractive keratectomy

Corneal haze represents subepithelial corneal fibrosis, a manifestation of a pathological healing process. It occurs as a result of an epithelial-stromal lesion involving a break in the epithelial barrier. It is an inflammatory response that involves the migration, multiplication and differentiation of keratocytes into mature myofibroblasts, causing loss of corneal transparency. Although it is a transient phenomenon, this complication is feared following refractive photokeratectomy (PRK), because it can cause alterations in the quality of vision, refractive regression and decreased visual acuity. The severity of these symptoms is correlated with the severity of the corneal haze, which can be assessed clinically or by objective means such as corneal densitometry measurement. The frequency and severity of corneal haze increase with the depth of photoablation in PRK and are therefore increased during the treatment of severe ametropia. Considering that no consensus exists, the application of mitomycin C (MMC) intraoperatively and topical corticosteroids postoperatively are conventionally used to inhibit collagen synthesis, sometimes in combination with various protocols depending on the center or surgeon. This review of the literature reports the current knowledge on corneal haze, in order to better understand it and optimise its prevention in the context of a decreased MMC supply, which has occurred in the past and could recur in the future.

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.

Cataract surgery and dry eye disease: A review

AIM

To review published literature concerning cataract surgery and dry eye disease (DED).

METHODS

A search was undertaken using the following: PubMed (all years), Web of Science (all years), Ovid MEDLINE(R) (1946 to 12 December 2019), Ovid MEDLINE(R) Daily Update 10 December 2019, MEDLINE and MEDLINE non-indexed items, Embase (1974-2019, week 49), Ovid MEDLINE (R) and Epub Ahead of Print, In-Process and Other Non-Indexed Citations and Daily (1946 to 12 December 2019), CENTRAL (including Cochrane Eyes and Vision Trials Register; Cochrane Library: Issue 12 of 12 December 2019), metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrial.gov) and WHO International Clinical Trials Registry Platform (www.who.int/ictrp/search/en). Search terms included 'cataract surgery', 'phacoemulsification' and 'cataract extraction', combined with 'dry eyes' and 'ocular surface'. Relevant in-article references not returned in our searches were also considered.

RESULTS

Publications identified included systematic reviews, meta-analysis, randomized controlled trials, cohort studies, case series and laboratory-based studies. Published data highlighting the burden of DED both prior and following cataract surgery were reviewed as well as studies highlighting the effects of cataract surgery on the ocular surface, intra-operative measures to reduce deleterious effects on the ocular surface and current evidence on the management options of post-operative DED.

CONCLUSIONS

DED is common and can be exacerbated by cataract surgery. Ophthalmologists need to assess for pre-existing DED and instigate treatment before surgery; be aware of reduced accuracy of measurements for surgical planning in the presence of DED; limit intra-operative surgical factors damaging to the ocular surface; and consider management to reduce DED post-operatively.

[In vivo Meibomian gland imaging techniques: A review of the literature (French translation of the article)]

Meibomian gland dysfunction (MGD) encompasses a group of complex pathologies of the ocular surface. They represent one of the main etiologies of dry eye but also one of the leading causes of consultation in ophthalmology. Conventional clinical tests (dry eye symptoms, tear film rupture time, glandular expressiveness assessment, or Schirmer's test) allow only an indirect assessment of Meibomian gland function and physiology. Various in vivo investigation methods have therefore been developed to image the meibomian glands such as meibography, optical coherence tomography, ultrasound or in vivo confocal microscopy. Some are accessible in clinical practice, while others remain in the field of clinical research. All these techniques aim to develop a direct structural analysis of the Meibomian glands to help in the diagnosis of DGM but also to better understand the pathophysiology of Meibomian glands. This review of the literature aims to provide an overview of existing imaging modalities and their interest in the evaluation of Meibomian glands and MGD.

In vivo Meibomian gland imaging techniques: A review of the literature

Meibomian gland dysfunction (MGD) includes a group of complex disorders of the ocular surface. It represents one of the main etiologies of dry eye as well as one of the main reasons for patient visits to the ophthalmologist. Classic clinical tests (dry eye symptoms, tear film break-up time, evaluation of gland expressibility or Schirmer's testing) only provide an indirect assessment of the function of the Meibomian glands and the meibum. Various in vivo testing methods have therefore been developed to image the Meibomian glands, such as Meibography, optical coherence tomography, ultrasound, or even in vivo confocal microscopy. Some are accessible in clinical practice, while others are limited to the realm of clinical research. All of these techniques aim to develop a direct structural analysis of the Meibomian glands so as to assist in the diagnosis of MGD as well as to better understand the pathophysiology of the Meibomian glands. This review of the literature hopes to provide an overview of the current imaging modalities and their role in the evaluation of the Meibomian glands and MGD.

The Role of Meibography in the Diagnosis of Meibomian Gland Dysfunction in Ocular Surface Diseases

Purpose

To evaluate dysfunction in various ocular surface diseases (OSDs) including primary meibomian gland disease (MGD), perennial allergic conjunctivitis, and primary and secondary Sjögren syndromes.

Methods

A retrospective analysis of 146 patients (111 women and 35 men) with symptomatic OSDs was performed. Patients were divided into two groups: the non-MGD group (55 patients) and the MGD group (91 patients). All patients had an evaluation of ocular surface symptoms and clinical tests, including tear film breakup time (BUT), the first and the mean noninvasive breakup time (NIKBUTf and NIKBUTavg, respectively). The meibomian gland loss of the lower eyelid was quantified using meibography and the meiboscale.

Results

There was no significant difference regarding age or sex ratio between the two groups. The meiboscale in the MGD group was significantly higher than that in the non-MGD group (P = 0.003). The non-MGD patients were more symptomatic than those in the MGD group (P = 0.043). There were no significant differences between MGD and non-MGD groups regarding a Schirmer test (P = 0.195), BUT (P = 0.719), NIKBUTf (P = 0.96), or NIKBUTavg (P = 0.70). In the whole population, there was a negative correlation between meiboscale and NIKBUT (r = -0.21, P = 0.02), but no other correlations were found.

Conclusions

Meibomian gland dysfunction was observed among different OSDs. Meibomian gland loss evaluated by meibography might help identify MGD in patients suffering from OSD.

Translation Relevance

Meibography provides a better understanding of MGD in several OSD. It may be useful to integrate this objective analysis to improve treatments of OSD associated to MGD.

In vivo confocal microscopy classification in the diagnosis of meibomian gland dysfunction

AIM

Meibomian gland dysfunction (MGD) is one of the most common disorders in ophthalmology. The aim of this study was to evaluate the use of this in vivo confocal microscopy (IVCM)-MGD description to classify patients affected by clinical MGD and measure the correlation with standard clinical criteria and subjective symptoms.

METHODS

One hundred eyes of 100 patients suffering from MGD and 15 eyes of normal subjects were included. A comprehensive evaluation with the ocular surface disease index (OSDI), Schirmer test, tear break-up time (TBUT), tear osmolarity, Oxford score, Meibomian gland expression, palpebral IVCM, and meibography was performed. Then each patient was classified using a new IVCM classification: type 0 for normality, type 1 for meibum obstruction, type 2 for inflammation, and type 3 for fibrosis.

RESULTS

The mean age of patients was 52 ± 20 years old, the OSDI was 38 ± 23, the BUT 5 ± 2.6 s, the Schirmer test 13 ± 7 mm, tear osmolarity 300 ± 11 osmol/L, the Oxford score 0.5 ± 0.6, the meibum expression score 1.7 ± 1.02, and the meibography score 1.3 ± 0.9. The IVCM MG classification of the 15 normal subjects was 0. For MGD patients, 29% were in type 1, 40% were type 2, and 31% were type 3. The patients in IVCM MG type 2 had a higher OSDI (p = 0.001) compared with the other types. There was a strong correlation between the IVCM score and the meibography score (r = 0.71 p < 0.0001).

CONCLUSION

This new IVCM classification provided a practical pathophysiological system for MGD. By giving objective criteria, this IVCM classification may help advance the understanding of patients' symptoms and enhance treatment effectiveness in MGD.

[Influence of cataract surgery on Meibomian gland dysfunction (French translation of the article)]

PURPOSE

To evaluate the influence of cataract surgery on meibomian gland dysfunction, in particular on postoperative functional symptoms.

PATIENTS AND METHODS

Thirty patients who underwent cataract surgery were included in the study. A clinical examination (OSDI questionnaire, measurement of tear break up time [TBUT], corneal staining, meibomian gland expressibility test) and a paraclinical evaluation (loss of Meibomius glands [LMG] measured using ImageJ on meibography, conjunctival redness and non-invasive tear break up time [NIK-BUT]) were performed preoperatively and at 1 month and 3 months after phacoemulsification.

RESULTS

TBUT and meibomian gland expressibility were worsened at 1 month and 3 months postoperatively (P<0.05). LMG was significantly more important for the upper eyelid and the mean at 1 month (33.1±15.2 P=0.02; 28.5±15.6 P=0.025, respectively) and 3 months postoperatively (36.5±17.4 P=0.0005; 31.2±17.4 P=0.0002, respectively) than preoperative values (29.4±15.3; 26±15, respectively). There was a significant correlation between LMG on the upper eyelid preoperatively and the OSDI score at 1 month postoperatively (R=0.37; P=0.05).

CONCLUSION

The meibomian gland loss in the upper eyelid is associated with an increased postoperative ocular discomfort score. Alterations in the meibomian gland expressibility and TBUT persist for up to 3 months postoperatively suggesting a direct role of cataract surgery by an obstructive mechanism.

Influence of cataract surgery on Meibomian gland dysfunction

PURPOSE

To evaluate the influence of cataract surgery on Meibomian gland dysfunction, in particular on postoperative functional symptoms.

PATIENTS AND METHODS

Thirty patients who underwent cataract surgery were included in the study. A clinical examination (OSDI questionnaire, measurement of tear break-up time (TBUT), corneal staining, Meibomian gland expression test) and a paraclinical evaluation (Meibomian gland loss [MGL] measured using ImageJ on Meibography, conjunctival hyperemia and non-invasive keratograph break-up time [NIK-BUT]) were performed preoperatively and at 1month and 3months after phacoemulsification.

RESULTS

TBUT and Meibomian gland expressibility were worsened at 1month and 3months postoperatively (P<0.05). MGL was significantly higher for the upper eyelid and the mean at 1month (33.1±15.2, P=0.02; 28.5±15.6, P=0.025, respectively) and 3months postoperatively (36.5±17.4, P=0.0005; 31.2±17.4, P=0.0002, respectively) than preoperative values (29.4±15.3; 26±15, respectively). There was a significant correlation between MGL on the upper eyelid preoperatively and the OSDI score at 1month postoperatively (R=0.37; P=0.05).

CONCLUSION

Meibomian gland loss in the upper eyelid is associated with an increased early postoperative ocular discomfort score. Alterations in Meibomian gland expressibility and TBUT persist for up to 3months postoperatively, suggesting a direct role of cataract surgery by an obstructive mechanism.

Emerging strategies for the diagnosis and treatment of meibomian gland dysfunction: Proceedings of the OCEAN group meeting

Meibomian gland dysfunction (MGD) is a common and chronic disorder that has a significant adverse impact on patients' quality of life. It is a leading cause of evaporative dry eye disease (DED), as meibomian glands play an important role in providing lipids to the tear film, which helps to retard the evaporation of tears from the ocular surface. MGD is also often present in conjunction with primary aqueous-deficient DED. Obstructive MGD, the most commonly observed type of MGD, is the main focus of this article. MGD is probably caused by a combination of separate conditions: primary obstructive hyperkeratinization of the meibomian gland, abnormal meibomian gland secretion, eyelid inflammation, corneal inflammation and damage, microbiological changes, and DED. Furthermore, skin diseases such as rosacea may play a part in its pathology. Accurate diagnosis is challenging, as it is difficult to differentiate between ocular surface diseases, but is crucial when choosing treatment options. Ocular imaging has advanced in recent years, providing ophthalmologists with a better understanding of ocular diseases. This review presents a literature update on the 2011 MGD workshop and an optimized approach to accurate diagnosis of MGD using currently available methods and tests. It also outlines the emerging technologies of interferometry, non-contact meibography, keratography and in vivo confocal laser microscopy, which offer exciting possibilities for the future. Selected treatment options for MGD are also discussed.

Clinical evaluation of an oil-based lubricant eyedrop in dry eye patients with lipid deficiency

PURPOSE

To evaluate and compare the efficacy of a lipid-based lubricant eyedrop formulation (hydroxypropyl guar/propylene glycol/phospholipid [HPG/PG/PL]) with preservative-free saline for the treatment of dry eye.

METHODS

This was a prospective, multicenter, randomized, single-masked, parallel-group phase 4 clinical study. Patients ≥18 years diagnosed with dry eye received 1 drop of saline 4 times daily (QID) for 15 days during a run-in phase, followed by randomization. Patients then instilled HPG/PG/PL or saline QID through day 35 and as needed through day 90. Change in tear film break-up time (TFBUT), change in total ocular surface staining (TOSS) score, and Impact of Dry Eye on Everyday Life (IDEEL) were evaluated on day 35.

RESULTS

Increase in TFBUT from baseline to day 35 was assessed during the interim and final analyses. Mean ± SE difference between the HPG/PG/PL (n = 110) and saline groups (n = 100) was 1.3 ± 0.4 seconds (interim analysis; 95% confidence interval [CI] 0.5-2.1 seconds; p = 0.0012) and 1.0 ± 0.3 seconds (final analysis; 95% CI 0.4-1.6 seconds; p = 0.0011), demonstrating the superiority of HPG/PG/PL. The mean ± SE difference between the HPG/PG/PL and saline groups for IDEEL treatment effectiveness scores was 16.0 ± 3.6 (95% CI 8.9-23.1; p<0.0001). No significant differences in TOSS scores or IDEEL inconvenience scores were observed between treatment groups.

CONCLUSIONS

Thirty-five days of QID HPG/PG/PL treatment resulted in a statistically significant improvement in TFBUT and IDEEL treatment effectiveness scores compared with saline but not in TOSS or IDEEL treatment inconvenience scores. HPG/PG/PL was well-tolerated by patients.

Revisiting the vicious circle of dry eye disease: a focus on the pathophysiology of meibomian gland dysfunction

Meibomian gland dysfunction (MGD) is the most frequent cause of dry eye disease (DED). Eyelid inflammation, microbial growth, associated skin disorders as well as potentially severe corneal complications culminate to make MGD a complex multifactorial disorder. It is probable that MGD is a heterogeneous condition arising from any combination of the following five separate pathophysiological mechanisms: eyelid inflammation, conjunctival inflammation, corneal damage, microbiological changes and DED resulting from tear film instability. The pathogenesis of both MGD and DED can be described in terms of a 'vicious circle': the underlying pathophysiological mechanisms of DED and MGD interact, resulting in a double vicious circle. The MGD vicious circle is self-stimulated by microbiological changes, which results in increased melting temperature of meibum and subsequent meibomian gland blockage, reinforcing the vicious circle of MGD. Meibomian gland blockage, dropout and inflammation directly link the two vicious circles. MGD-associated tear film instability provides an entry point into the vicious circle of DED and leads to hyperosmolarity and inflammation, which are both a cause and consequence of DED. Here we propose a new pathophysiological scheme for MGD in order to better identify the pathological mechanisms involved and to allow more efficient targeting of therapeutics. Through better understanding of this scheme, MGD may gain true disease status rather than being viewed as a mere dysfunction.

[A new classification for meibomian gland diseases with in vivo confocal microscopy]

INTRODUCTION

Meibomian gland dysfunction (MGD) is a frequent disorder often associated with dry eye disease. Slit-lamp examination with digital expression of the tarsal Meibomian glands allows examination of the contents of the distal Meibomian gland and the meatus. However, the Meibomian epithelium, interglandular space and proximal secretions cannot be clinically assessed. In vivo confocal microscopy (IVCM) is a rapid and non-invasive imaging technique that provides high-resolution images of the ocular surface and eyelids. The primary objective of the present study was to establish a classification of MGD with IVCM. Secondary objectives were to evaluate this scoring system by analyzing the correlation with OSDI, infrared (IR) meibography and Demodex infestation.

MATERIAL AND METHODS

Forty-six dry eye patients (Ocular Surface Disease Index [OSDI] >13) associated with MGD were enrolled. Ten healthy subjects without dry eye disease or blepharitis were also included as controls. An OSDI questionnaire, clinical examination, IVCM and infrared meibography of the lower lid were performed in all subjects by the same examiner.

RESULTS

A new MGD score was established based on IVCM findings: the first stage was Meibomian obstruction with a clear epithelium, the second stage was an inflammatory state with Meibomian gland obstruction, epithelial and interglandular inflammation, and the last stage was glandular fibrosis. This score was significantly correlated with the meiboscore obtained with infrared meibography (correlation coefficient 0.47, CI95% [0.22-0.66]).

CONCLUSION

IVCM of the Meibomian gland complex complements the clinical examination by determining the stage of dysfunction and may help clinicians evaluate and treat MGD.