Increase in tear film lipid layer thickness after instillation of 3% diquafosol ophthalmic solution in healthy human eyes

Applications of Diquafosol Sodium in Ophthalmology: A Comprehensive Review of Therapeutic Utility

Diquafosol sodium is a purinergic P2Y2 receptor agonist that is garnering much interest for its potential therapeutic benefits in ocular surface management. This review provides a comprehensive analysis of diquafosol's pharmacology, clinical effectiveness, and role in the evolving landscape of ocular surface management. Future research should focus on optimising formulations, treatment duration, and exploring potential combination therapies to maximise therapeutic outcomes. By targeting underlying pathophysiological mechanisms, diquafosol represents a significant advancement in ocular surface management and a valuable addition to existing therapies.

An update on emerging pharmacological treatments for meibomian gland dysfunction

INTRODUCTION

Meibomian Gland Dysfunction (MGD) represents the most common cause of dry eye disease (DED). Traditional treatments mainly rely on heating and liquifying the meibum to favor its expression. However, recent knowledge advances have led to the development of novel therapies specifically designed for patients with MGD.

AREAS COVERED

Literature search was conducted on current and novel treatments for MGD. Conventional treatment strategies, non-pharmacological approved device-based therapies, approved dry eye therapies and both recently approved and emerging pharmacological treatments specifically designed to address MGD are discussed.

EXPERT OPINION

The better understanding of MGD and DED pathophysiology has allowed to develop drugs able to target the primary mechanisms of the disease. Miebo has been the first FDA approved drug for patients with DED associated with MGD and its ability to reduce the tear film layer evaporation rate and the minimal impact on the quality of vision are important innovations. Great expectations also accompany the phase 3 study of AZR-MD-001, understood to be a keratolytic and lipogenic agent able to improve meibum quantity and quality. The chance to specifically target MGD represents an important step forward and will allow more tailored treatment for each type of ocular surface disease.

Targeting purine metabolism-related enzymes for therapeutic intervention: A review from molecular mechanism to therapeutic breakthrough

Purines are ancient metabolites with established and emerging metabolic and non-metabolic signaling attributes. The expression of purine metabolism-related genes is frequently activated in human malignancies, correlating with increased cancer aggressiveness and chemoresistance. Importantly, under certain stimulating conditions, the purine biosynthetic enzymes can assemble into a metabolon called "purinosomes" to enhance purine flux. Current evidence suggests that purine flux is regulated by a complex circuit that encompasses transcriptional, post-translational, metabolic, and association-dependent regulatory mechanisms. Furthermore, purines within the tumor microenvironment modulate cancer immunity through signaling mediated by purinergic receptors. The deregulation of purine metabolism has significant metabolic consequences, particularly hyperuricemia. Herbal-based therapeutics have emerged as valuable pharmacological interventions for the treatment of hyperuricemia by inhibiting the activity of hepatic XOD, modulating the expression of renal urate transporters, and suppressing inflammatory responses. This review summarizes recent advancements in the understanding of purine metabolism in clinically relevant malignancies and metabolic disorders. Additionally, we discuss the role of herbal interventions and the interaction between the host and gut microbiota in the regulation of purine homeostasis. This information will fuel the innovation of therapeutic strategies that target the disease-associated rewiring of purine metabolism for therapeutic applications.

Tolerability of Diquas LX on tear film and meibomian glands findings in a real clinical scenario

Long-acting diquafosol ophthalmic solution (DQS-LX) has significant advantages regarding patient adherence owing to the reduced frequency of required eye drops; however, some patients prefer conventional diquafosol ophthalmic solution (DQS) over DQS-LX. Herein, to clarify the characteristics of patients according to their preference for ophthalmic solutions, dry eye (DE) and meibomian gland (MG) findings were retrospectively investigated. This study enrolled 341 patients with DE (mean age, 62.1 ± 11.7 years) treated at the Itoh Clinic between November 8, 2022, and July 31, 2023, who switched from DQS to DQS-LX. Patients were divided into two groups: those who continued DQS-LX administration (DQS-LX group) and those who wished to revert to conventional DQS (DQS group). Data regarding subjective symptoms assessed using the Standard Patient Evaluation of Eye Dryness (SPEED) questionnaire, tear film breakup time (BUT), tear meniscus height (TMH), corneal and conjunctival fluorescein staining (CFS), conjunctival hyperemia/papilla, meiboscore, plugging, vascularity, meibum grade, and Schirmer's score at the time of DQS-LX switch were evaluated. Of the 341 patients, 31 (9.1%) wished to revert to conventional DQS. In total, 16 eyes of 16 patients in the DQS group and 32 eyes of 32 patients in the DQS-LX group-for whom complete data were available-were included in the analysis. The DQS-LX group had higher SPEED scores, lower TMHs (P < 0.001, respectively), shorter FBUTs, greater CFS findings, larger meibum grades, lower Schirmer scores, and more pluggings compared with the DQS group (P = 0.005, 0.001, 0.001, 0.046, 0.003, respectively). Meiboscores and vascularity did not differ significantly between the two groups (P = 0.73 and 0.39, respectively). In conclusion, patients with low tear film volume and DE complicated by moderate or severe meibomian gland dysfunction (MGD) preferred DQS-LX, while those with allergic findings preferred conventional DQS.

The Effect of Topical Rebamipide 2% in Managing Dry Eye Following Cataract Surgery

Purpose: To evaluate the potential advantages of using topical rebamipide 2% to manage dry eye following cataract surgery.Methods: Patients who underwent cataract surgery (phacoemulsification and intraocular lens insertion) were evaluated for dry eye 1 week postoperatively. Randomly selected patients were divided into the rebamipide group, who received 2% rebamipide eye drops, and the control group, who did not receive rebamipide. Various dry eye-related tests, including Schirmer’s test, the tear break-up time (TBUT), ocular surface staining, tear film osmolarity, tear lipid layer thickness, and the ocular surface disease index (OSDI) were performed in both groups 1 week, and 1 and 2 months postoperatively.Results: In the rebamipide group, we observed significant improvement in TBUT, the ocular surface staining score, and OSDI at 2 months postoperatively, as compared to 1 week (<i>p</i> = 0.002, 0.014, and 0.013, respectively). Schirmer’s test, tear film osmolarity, and tear lipid layer thickness remained unchanged in the rebamipide group. Throughout the entire follow-up period, the rebamipide group had a significantly prolonged TBUT (1 month: <i>p</i> = 0.007, 2 months: <i>p</i> = 0.000), and lower ocular surface staining score (1 month: <i>p</i> = 0.000, 2 months: <i>p</i> = 0.000), as compared to the control.Conclusions: Following cataract surgery, the use of rebamipide eye drops produced improvements in TBUT, ocular surface staining scores, and OSDI. This suggests that rebamipide offers benefits in managing dry eye that can occur after cataract surgery.

Comparing two mucin secretagogues for the treatment of dry eye disease: a prospective randomized crossover trial

This study aimed to compare the clinical efficacy and investigate patients' preferences for two mucin secretagogues in the treatment of dry eye disease (DED). Thirty patients with DED were randomly treated with either 3% diquafosol or 2% rebamipide ophthalmic solution for 4 weeks, followed by an additional 4-week treatment using the other eye drop after a 2-week washout period. Objective and subjective assessments, including the corneal and conjunctival staining score, tear breakup time (TBUT), Schirmer 1 test, tear osmolarity, tear matrix metalloproteinase-9 (MMP-9), lipid layer thickness (LLT) and ocular surface disease index (OSDI), were performed at baseline, 4 weeks, 6 weeks, and 10 weeks. Patient preferences were assessed based on four categories (comfort, efficacy, convenience, willingness to continue) using a questionnaire and the overall subjective satisfaction score for each drug was obtained at the end of the trial. In total, 28 eyes from 28 patients were included in the analysis. Both diquafosol and rebamipide significantly improved the OSDI (p = 0.033 and 0.034, respectively), TBUT (p < 0.001 and 0.026, respectively), and corneal (p < 0.001 and 0.001, respectively) and conjunctival (p = 0.017 and 0.042, respectively) staining after 4 weeks of treatment. An increase in Schirmer test scores was observed only after rebamipide treatment (p = 0.007). No significant changes were detected in tear osmolarity, MMP-9, and LLT following both treatments. The patients' preference was slightly greater for diquafosol (46.4%) than rebamipide (36.7%), presumably due to rebamipide's bitter taste. The self-efficacy of both drugs and overall satisfaction scores were comparable. These findings indicate that two mucin secretagogues showed comparable effects in ameliorating symptoms and improving signs (TBUT, corneal and conjunctival staining) in patients with DED.

Treatment of Dry Eye Disease (DED) in Asia: Strategies for Short Tear Film Breakup Time-Type DED

Dry eye disease (DED) is a multifactorial disorder in which tear fluid homeostasis is lost, resulting in increased tear film osmolarity and ocular surface irritation. In Asia, the short tear film breakup time-type DED, which has become a global problem in recent years, is common. While the mainstay of DED treatment in the West is the suppression of inflammation, the first goal of treatment is the stabilization of the tear film in Asia. To date, artificial tears and steroid eye drops have been the main treatment for DED. However, artificial tears require frequent administration of eye drops and thus pose adherence problems, while steroids have problems with side-effects (cataracts, increased intraocular pressure). This review evaluates the new generation therapies in Asia based on what is known about them and demonstrates that they are more effective for DED than traditional therapies such as artificial tears and steroids. Based on considerations, it is proposed that the optimal treatment for the short tear film breakup time-type DED is the initial application of mucin-secretion-enhancing eye drops (long-acting diquafosol) and oral supplements; and if additional treatment is needed, cyclosporine eye drops and the adjunctive therapies presented in this review are added.

Efficacy of a 0.05% cyclosporine a topical nanoemulsion in dry eyes with obstructive meibomian gland dysfunction

PURPOSE

To evaluate the efficacy of topical cyclosporin A (CsA) in obstructive meibomian gland dysfunction (MGD).

STUDY DESIGN

Prospective, randomized, single-blinded, controlled clinical study.

METHODS

Fifty-one patients with obstructive MGD were randomly assigned to one of two groups. The CsA group received 0.05% CsA topical nanoemulsion (Cyporin N®; Taejoon Pharm) twice daily, 0.15% hyaluronic acid eye drops four times daily, and 10 min of warm compress placement on the eyelids twice daily. In the control group, 0.15% hyaluronic acid eye drops were administered six times daily and warm compress was conducted twice daily for 10 min. The ocular surface disease index (OSDI), Schirmer 1 test, tear film break-up time (TBUT), corneal and conjunctival surface staining using fluorescein, eyelid debris and eyelid redness/swelling, upper and lower meibomian gland (MG) secretion scores, and upper and lower MG loss were assessed at the three-month visits.

RESULTS

There were no significant differences in observed parameters between the two groups at baseline. At the three-month evaluation, the CsA group showed significantly better improvements in the TBUT, eyelid debris, eyelid redness/swelling, and lower MG secretion score (P < 0.001, P < 0.001, P < 0.001, and P < 0.001, respectively). There was no improvement in upper or lower MG loss in either group.

CONCLUSION

Treatment with 0.05% CsA nanoemulsion in combination with warm compress twice daily alleviated signs of dry eyes with obstructive MGD. However, although MG secretion was improved, glandular loss could not be restored with three months of CsA nanoemulsion treatment.

Impact of Diquafosol Ophthalmic Solution on Tear Film and Dry Eye Symptom in Type 2 Diabetic Dry Eye: A Pilot Study

Background: Diquafosol ophthalmic solution (DQS) stimulates P2Y2 receptors on the ocular surface, which enhances mucin secretion from goblet cells. Therefore, tear film stability and hydration of the ocular surface can be achieved independent from lacrimal gland function. Methods: This prospective, open-label pilot study included 60 eyes of 30 diabetic patients diagnosed with dry eye disease (DED) and were randomly assigned to either DQS (n = 30 eyes) or hyaluronate (HA) group (n = 30 eyes). Participants in the DQS group received 3% diquafosol ophthalmic solution, whereas HA group received 0.1% sodium HA preservative-free artificial tears. The dosage for both drugs was 1 drop, 6 times per day for 4 weeks. Tear film lipid layer (TFLL), noninvasive breakup time (NITBUT), corneoconjunctival staining (CS) score, meibomian gland (MG), conjunctival hyperemia [redness score (RS)], ocular surface disease index (OSDI) was assessed and compared at baseline, day 14, and day 28. Results: Comparing baseline and day 28 measurements revealed that both groups found significant improvements in NITBUT, CS, MG quality, MG expressibility, and OSDI scores significantly (P < 0.05), in addition TFLL improvements were only found in the DQS group. At day 28, the magnitude of change in mean NITBUT was 1.74 (DQS) versus 0.31 (HA), 1.16 (DQS) versus 0.37 (HA) point grade reduction in corneoconjunctival staining score and 9.80 (DQS) versus 4.80 (HA) point grade in mean OSDI score. Conclusion: Three percent diquafosol ophthalmic solution treatment demonstrated the ability to improve the tear film dry eye parameters and clinically reduced sign and symptoms of DED in diabetic dry eye patients. Clinical Trials.gov ID: NCT04980144.

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.

From purines to purinergic signalling: molecular functions and human diseases

Purines and their derivatives, most notably adenosine and ATP, are the key molecules controlling intracellular energy homoeostasis and nucleotide synthesis. Besides, these purines support, as chemical messengers, purinergic transmission throughout tissues and species. Purines act as endogenous ligands that bind to and activate plasmalemmal purinoceptors, which mediate extracellular communication referred to as "purinergic signalling". Purinergic signalling is cross-linked with other transmitter networks to coordinate numerous aspects of cell behaviour such as proliferation, differentiation, migration, apoptosis and other physiological processes critical for the proper function of organisms. Pathological deregulation of purinergic signalling contributes to various diseases including neurodegeneration, rheumatic immune diseases, inflammation, and cancer. Particularly, gout is one of the most prevalent purine-related disease caused by purine metabolism disorder and consequent hyperuricemia. Compelling evidence indicates that purinoceptors are potential therapeutic targets, with specific purinergic agonists and antagonists demonstrating prominent therapeutic potential. Furthermore, dietary and herbal interventions help to restore and balance purine metabolism, thus addressing the importance of a healthy lifestyle in the prevention and relief of human disorders. Profound understanding of molecular mechanisms of purinergic signalling provides new and exciting insights into the treatment of human diseases.

Diquafosol tetrasodium elicits total cholesterol release from rabbit meibomian gland cells via P2Y2 purinergic receptor signalling

Diquafosol tetrasodium (DQS), a purinergic P2Y₂ receptor agonist, stimulates secretion of both water and mucins from the conjunctiva into tears. Hence, DQS-containing eye drops have been approved as a therapeutic option for dry eye disease in some Asian countries, including Japan. Recent clinical reports state that instilling DQS-containing eye drops significantly increases the lipid layer thickness in tears. Therefore, we examined this compound's direct actions on holocrine lipid-secreting meibomian gland cells and their function. Isolated meibomian gland cells (meibocytes) were procured from rabbits and cultivated in serum-free culture medium. Differentiated meibocytes with pioglitazone were used for the subsequent experiments. Intracellular Ca²⁺ signalling of the cells was dramatically elevated with DQS addition in a dose-dependent manner. This DQS-induced elevation was almost completely cancelled by the coexistence of the selective P2Y₂ receptor antagonist AR-C118925XX. DQS treatment also facilitated total cholesterol (TC) release from cells into the medium. This effect of DQS on TC was suppressed significantly by the intracellular Ca²⁺ chelator BAPTA-AM as well as by AR-C118925XX. DNA fragmentation analysis revealed that DQS may have enhanced the apoptotic DNA fragmentation caused spontaneously by cells. Thus, DQS could stimulate meibocytes to release lipids through the P2Y₂ receptor and possibly facilitate holocrine cell maturation.

Diquafosol tetrasodium elicits total cholesterol release from rabbit meibomian gland cells via P2Y2 purinergic receptor signalling

Diquafosol tetrasodium (DQS), a purinergic P2Y₂ receptor agonist, stimulates secretion of both water and mucins from the conjunctiva into tears. Hence, DQS-containing eye drops have been approved as a therapeutic option for dry eye disease in some Asian countries, including Japan. Recent clinical reports state that instilling DQS-containing eye drops significantly increases the lipid layer thickness in tears. Therefore, we examined this compound’s direct actions on holocrine lipid-secreting meibomian gland cells and their function. Isolated meibomian gland cells (meibocytes) were procured from rabbits and cultivated in serum-free culture medium. Differentiated meibocytes with pioglitazone were used for the subsequent experiments. Intracellular Ca²⁺ signalling of the cells was dramatically elevated with DQS addition in a dose-dependent manner. This DQS-induced elevation was almost completely cancelled by the coexistence of the selective P2Y₂ receptor antagonist AR-C118925XX. DQS treatment also facilitated total cholesterol (TC) release from cells into the medium. This effect of DQS on TC was suppressed significantly by the intracellular Ca²⁺ chelator BAPTA-AM as well as by AR-C118925XX. DNA fragmentation analysis revealed that DQS may have enhanced the apoptotic DNA fragmentation caused spontaneously by cells. Thus, DQS could stimulate meibocytes to release lipids through the P2Y₂ receptor and possibly facilitate holocrine cell maturation.

Interactions of Meibum and Tears with Mucomimetic Polymers: A Hint towards the Interplay between the Layers of the Tear Film

Recent clinical findings suggest that mucomimetic polymers (MMP) can alter not only the texture of the aqueous tear but also the spreading and structure of the tear film (TF) lipid layer, thereby allowing for their synchronized performance in vivo. Thus, we aimed to evaluate in vitro (i) the capability of pharmaceutically applicable MMP to ensure the formation of post-evaporative ferning patterns (a characteristic feature of the “healthy” tear colloid) and (ii) the MMP interactions with human meibum films accessed in the course of blink-like deformations via Langmuir surface balance and Brewster angle microscopy (BAM). Four MMP were used- hyaluronic acid (HA), cross-linked hyaluronic acid (CHA), carboxymethyl cellulose (CMC) and gellan gum (GG)- at the concentrations of 0.0001%, 0.001%, 0.01%, 0.05% and 0.1%. Significant differences were observed in the MMP fern formation capability: CHA (≥0.001%) > HA (≥0.01%) = CMC (≥0.01%) > GG (≥0.05%). All MMP affected the spreading of meibum, with BAM micrographs revealing thickening of the films. CHA was particularly efficient, showing concentration-dependent enhancement of tear ferning and of meibomian layer structure, surfactant properties and viscoelasticity. Thus, endogenous and exogenous MMP may play key roles for the concerted action of the TF layers at the ocular surface, revealing novel routes for TF-oriented therapeutic applications.

A multicenter cross-sectional survey of dry eye clinical characteristics and practice patterns in Korea: the DECS-K study

PURPOSE

To compare the proportions of patients satisfying Korean dry eye guidelines and Asia Dry Eye Society (ADES) diagnostic criteria and to describe the clinical characteristics and practice patterns of dry eye patients in Korea.

STUDY DESIGN

Prospective observational study.

METHODS

This study enrolled 160 patients, with 158 patients analyzed. ADES guidelines were applied to dry eye patients satisfying the Korean dry eye guidelines. Risk factors for dry eye (e.g. visual display terminal [VDT] use) were evaluated. Dry eye subtypes were categorized as aqueous-deficient or evaporative. Objective signs (e.g. corneal and keratoconjunctival staining scores, tear break-up time [TBUT], and Schirmer test) and symptoms (Dry Eye-Related Quality of Life Score [DEQS] and Ocular Surface Disease Index [OSDI] questionnaire) were evaluated. Treatment patterns were also recorded.

RESULTS

Patients (mean age 43.1 years) were mainly women (85.4%), with a high proportion (77.2%) of VDT users. Concordance between Korean and ADES guidelines was high (94.3%), with most patients (94.3%) having tear film instability (TBUT ≤ 5 s). Evaporative dry eye occurred in 60.1% and aqueous-deficient in 39.9% of cases. Objective signs were significantly better in evaporative than in aqueous-deficient dry eye. The DEQS bothersome ocular symptoms' score was significantly higher in VDT users than in non-users. OSDI symptom severity and DEQS were significantly correlated (p < 0.001). The most common treatments were hyaluronic acid (33.5%) and diquafosol (15.2%), the latter used mainly for mild and evaporative dry eye.

CONCLUSION

The study showed high concordance between Korean and ADES diagnostic guidelines, with most patients having tear film instability.

Multicenter Study of Intense Pulsed Light for Patients with Refractory Aqueous-Deficient Dry Eye Accompanied by Mild Meibomian Gland Dysfunction

Aqueous-deficient dry eye (ADDE) and meibomian gland dysfunction (MGD) can be refractory to therapy. Intense pulsed light (IPL) was recently introduced as an effective treatment for MGD. We here evaluated the efficacy of IPL combined with MG expression (MGX) compared with MGX alone (n = 23 and 20, respectively) for patients with refractory ADDE with mild MGD at three sites. Symptom score, visual acuity (VA), noninvasive breakup time (NIBUT) and lipid layer thickness (LLT) of the tear film, lid margin abnormalities, fluorescein BUT (FBUT), fluorescein staining, tear meniscus height (TMH), meibum grade, meiboscore, and Schirmer's test value were assessed at baseline and 1 and 3 months after treatment. LLT, plugging, vascularity, FBUT and NIBUT were improved only in the IPL-MGX group at three months compared with baseline. All parameters with the exception of VA, meiboscore, TMH, Schirmer's test value were also improved in the IPL-MGX group compared with the control group at three months, as was VA in patients with central corneal epitheliopathy. Although IPL-MGX does not affect aqueous layer, the induced improvement in quality and quantity of the lipid layer may increase tear film stability and ameliorate symptoms not only for evaporative dry eye but for ADDE.

Novel Approaches for Imaging-Based Diagnosis of Ocular Surface Disease

Imaging has become indispensable in the diagnosis and management of diseases in the posterior part of the eye. In recent years, imaging techniques for the anterior segment are also gaining importance and are nowadays routinely used in clinical practice. Ocular surface disease is often synonymous with dry eye disease, but also refers to other conditions of the ocular surface, such as Meibomian gland dysfunction or keratitis and conjunctivitis with different underlying causes, i.e., allergies or infections. Therefore, correct differential diagnosis and treatment of ocular surface diseases is crucial, for which imaging can be a helpful tool. A variety of imaging techniques have been introduced to study the ocular surface, such as anterior segment optical coherence tomography, in vivo confocal microscopy, or non-contact meibography. The present review provides an overview on how these techniques can be used in the diagnosis and management of ocular surface disease and compares them to clinical standard methods such as slit lamp examination or staining of the cornea or conjunctiva. Although being more cost-intensive in the short term, in the long term, the use of ocular imaging can lead to more individualized diagnoses and treatment decisions, which in turn are beneficial for affected patients as well as for the healthcare system. In addition, imaging is more objective and provides good documentation, leading to an improvement in patient follow-up and education.

An eye on the dog as the scientist's best friend for translational research in ophthalmology: Focus on the ocular surface

Preclinical animal studies provide valuable opportunities to better understand human diseases and contribute to major advances in medicine. This review provides a comprehensive overview of ocular parameters in humans and selected animals, with a focus on the ocular surface, detailing species differences in ocular surface anatomy, physiology, tear film dynamics and tear film composition. We describe major pitfalls that tremendously limit the translational potential of traditional laboratory animals (i.e., rabbits, mice, and rats) in ophthalmic research, and highlight the benefits of integrating companion dogs with clinical analogues to human diseases into preclinical pharmacology studies. This One Health approach can help accelerate and improve the framework in which ophthalmic research is translated to the human clinic. Studies can be conducted in canine subjects with naturally occurring or noninvasively induced ocular surface disorders (e.g., dry eye disease, conjunctivitis), reviewed herein, and tear fluid can be easily retrieved from canine eyes for various bioanalytical purposes. In this review, we discuss common tear collection methods, including capillary tubes and Schirmer tear strips, and provide guidelines for tear sampling and extraction to improve the reliability of analyte quantification (drugs, proteins, others).

The protective effect of 3% diquafosol on meibomian gland morphology in glaucoma patients treated with prostaglandin analogs: a 12-month follow-up study

Background

To determine if 3% diquafosol (DQS) can preserve the meibomian gland morphology in glaucoma patients treated with prostaglandin analogs (PGA) for a 12-month follow-up period.

Methods

This study included 84 eyes of 46 normal tension glaucoma (NTG) patients who were treated with either preservative-containing PGA (PC-PGA; 16 patients, 28 eyes), preservative-free PGA (PF-PGA; 21 patients, 39 eyes), or a combination of PC-PGA and 3% DQS (PC-PGA + DQS; 9 patients, 17 eyes). The meibography of the upper eyelid was acquired using Keratograph® 5 M at baseline and at each follow-up (1, 3, 6, 9, and 12 months). Meibomian gland loss (MGL) was quantitatively analyzed by using ImageJ software.

Results

In the PC-PGA group, MGL increased significantly from baseline to month 9 and month 12, whereas no significant changes were observed in the PF-PGA and PC-PGA + DQS groups during the entire 12 months. All groups showed similar MGL at each follow-up time from baseline to six months. However, MGL in the PC-PGA group was significantly higher than those in the PF-PGA and PC-PGA + DQS groups at the 9 and 12 months.

Conclusions

Combining 3% DQS with PC-PGA was as effective as PF-PGA in preserving the meibomian gland morphology for at least 12 months. Our results suggest that 3% DQS may be a promising strategy for managing glaucoma patients with a high risk of developing meibomian gland dysfunction due to preservative-containing topical medications.

Determination of Tear Lipid Film Thickness Based on a Reflected Placido Disk Tear Film Analyzer

This study aims at determining the thickness of the tear lipid layer (LL) observed from a placido-disc-based tear film analyzer. We prospectively collected reflections of placido-disk LL images using a tear film analyzer (Keratograph® 5M, Oculus) from subjects with dry eye symptoms. The LL thickness (LLT) over the inferior half of the cornea was estimated with the use of interference color analysis and the preprocessing of images with and without ring segmentation were obtained and analyzed. Moreover, LLTs before and after 1 h of applying topical ointment (Duratears, Alcon) were compared to validate the estimation of LLT. Our results suggested that the tear LLT can be assessed using a placido-disk-based tear film analyzer and interference color analysis. We verified a high correlation between non-segmented and segmented LL images and estimated LLT increase after applying ointment. In addition, we concluded that LLT can be evaluated by direct interference analysis without segmentation preprocessing.

Contribution of Mucins towards the Physical Properties of the Tear Film: A Modern Update

Instability of the tear film (TF) protecting the ocular surface results in dry eye syndrome (DES), the most prevalent public health ophthalmic disease affecting the quality of life of 10 to 30% of the human population worldwide. Although the impact of the tear film lipid layer (TFLL) and of the aqueous tears (AT) to the TF stability is extensively studied, in contrast the contribution of the secretory mucins (SM) and of the membrane-associated mucins (MAM), i.e., one of the most abundant molecular classes in AT and in the corneal epithelium respectively, remains poorly defined. However, it is well known that in DES both types of mucins are quantitatively or qualitatively deficient. Numerous studies since the 1990s until now have proposed direct involvement of SM and MAM in the material properties (viscoelasticity, hydration, and protection of the ocular surface; synergistic cooperation with the rest of the TF layers; etc.) and stability of TF. These theories will be reviewed here in the context of the classical and modern in vitro and in vivo results that allow their reappraisal and in view of the novel mucin secretion enhancing pharmaceuticals, which have opened innovative routes for the therapy of DES.

Changes of tear film lipid layer thickness by 3% diquafosol ophthalmic solutions in patients with dry eye syndrome

AIM

To evaluate the quantitatively changes in lipid layer thickness (LLT) when 3% diquafosol eye drop is used for dry eye patients using the tear film interferometer.

METHODS

A total 124 participants (32 males, 92 females; mean age, 28.9y) diagnosed with dry eye disease (DED) received topical instillation of 4 ophthalmic solutions in one eye: diquafosol, normal saline, 0.1% sodium hyaluronate and 0.3% gatifloxacin, in a masked manner. LLT was measured using an interferometer at baseline and 20min after the instillation of each ophthalmic solutions.

RESULTS

Changes of LLT after instillation (nm, mean± standard error) were as follows: 12.6±2.0 for diquafosol (P<0.001), 1.2±2.2 for normal saline (P=0.301), 1.5±2.0 for hyaluronate (P=0.495), and 0.5±3.2 for gatifloxacin (P=0.884).

CONCLUSION

Topical instillation of diquafosol increases tear film LLT in DED patients. Diquafosol 3% eye drop might be effective treatment option of evaporative DED with meibomian gland dysfunction.

Effects of Preservative-free 3% Diquafosol in Patients with Pre-existing Dry Eye Disease after Cataract Surgery: A Randomized Clinical Trial

Dry eye disease (DED) after cataract surgery has become a critical concern, and various therapeutic options have been developed. Recently, preservative-free diquafosol ophthalmic solution has been introduced; however, its therapeutic effect on DED after cataract surgery has not been reported. We investigated the efficacy of preservative-free diquafosol in patients with pre-existing DED after cataract surgery. We divided subjects who were diagnosed with DED and scheduled to undergo cataract surgery, into 3 groups (preservative-free diquafosol, group 1; preservative-containing diquafosol, group 2; preservative-free hyaluronate, group 3), and each eye drops was administered 6 times daily after surgery. Tear break up time (TBUT), Ocular Surface Disease Index (OSDI), corneal staining score, lid margin abnormality, and meibum quality improved over time in group 1. Groups 1 and 2 had significantly superior TBUT, meibomian gland dysfunction grade, and meibomian gland expressibility throughout the study period than group 3. Meibum quality of group 1 was significantly better than group 2 at 1 and 3 months after surgery. Preservative-free diquafosol showed better efficacy in treating DED after cataract surgery than preservative-containing diquafosol or preservative-free hyaluronate. Preservative-free diquafosol may serve as a reliable option for the management of patients with pre-existing DED after phacoemulsification.

Effects of Preservative-free 3% Diquafosol in Patients with Pre-existing Dry Eye Disease after Cataract Surgery: A Randomized Clinical Trial

Dry eye disease (DED) after cataract surgery has become a critical concern, and various therapeutic options have been developed. Recently, preservative-free diquafosol ophthalmic solution has been introduced; however, its therapeutic effect on DED after cataract surgery has not been reported. We investigated the efficacy of preservative-free diquafosol in patients with pre-existing DED after cataract surgery. We divided subjects who were diagnosed with DED and scheduled to undergo cataract surgery, into 3 groups (preservative-free diquafosol, group 1; preservative-containing diquafosol, group 2; preservative-free hyaluronate, group 3), and each eye drops was administered 6 times daily after surgery. Tear break up time (TBUT), Ocular Surface Disease Index (OSDI), corneal staining score, lid margin abnormality, and meibum quality improved over time in group 1. Groups 1 and 2 had significantly superior TBUT, meibomian gland dysfunction grade, and meibomian gland expressibility throughout the study period than group 3. Meibum quality of group 1 was significantly better than group 2 at 1 and 3 months after surgery. Preservative-free diquafosol showed better efficacy in treating DED after cataract surgery than preservative-containing diquafosol or preservative-free hyaluronate. Preservative-free diquafosol may serve as a reliable option for the management of patients with pre-existing DED after phacoemulsification.

Tear film lipid layer increase after diquafosol instillation in dry eye patients with meibomian gland dysfunction: a randomized clinical study

Diquafosol promotes secretion of tear fluid and mucin at the ocular surface and is administered for treatment of dry eye (DE). Tear film lipid layer is secreted from meibomian glands and stabilizes the tear film. We recently showed that diquafosol administration increased lipid layer thickness (LLT) for up to 60 min in normal human eyes. We here evaluated tear film lipid layer in DE patients (n = 47) with meibomian gland dysfunction (MGD) before as well as 30, 60, and 90 min after diquafosol administration. One drop of artificial tears or one drop of diquafosol was applied randomly to the eyes of each patient. Diquafosol significantly increased LLT at 30 (P < 0.001) and 60 (P = 0.042) min and noninvasive tear film breakup time for at least 90 min (P < 0.001 at each assessment point). Artificial tears had no such effect. Diquafosol significantly improved the tear interferometric pattern compared with artificial tears (P < 0.001 at each assessment point). A single topical administration of diquafosol thus improved LLT and tear film stability in DE patients with MGD, suggesting that diquafosol is a potential treatment not only for aqueous-deficient DE but also for evaporative DE associated with MGD.

Emerging targets of inflammation and tear secretion in dry eye disease

The underlying mechanisms of dry eye are thought to be part of a vicious circle involving a hyperosmolarity-triggered inflammatory cascade, resulting in loss of goblet cells and glycocalyx mucin and observed corneal and conjunctival epithelial cell damage. This damage leads to increased tear film instability, further hyperosmolarity and hence perpetuating of a vicious circle. The aim of dry eye management is to restore the homeostasis of the tear film and break the perpetuation of this vicious circle. Despite the plethora of treatment options available, many of these are largely palliative, short-lived and require repeated instillations. Two emerging areas in dry eye therapy aim to promote tear secretion and to safely manage dry eye-associated inflammation and are the focus of this review.

Multicenter Study of Intense Pulsed Light Therapy for Patients With Refractory Meibomian Gland Dysfunction

Purpose:

To evaluate the efficacy of intense pulsed light (IPL) therapy combined with meibomian gland expression (MGX) for refractory meibomian gland dysfunction (MGD) in a prospective study conducted at 3 sites in Japan.

Methods:

Patients with refractory obstructive MGD were enrolled and underwent 4 to 8 IPL-MGX treatment sessions at 3-week intervals. Clinical assessment included the Standard Patient Evaluation of Eye Dryness questionnaire; noninvasive breakup time of the tear film and interferometric fringe pattern as determined by tear interferometry; lid margin abnormalities, fluorescein breakup time of the tear film, corneal and conjunctival fluorescein staining (CFS), and meibum grade as evaluated with a slit-lamp microscope; meibomian gland morphology (meiboscore); and tear production as measured by the Schirmer test without anesthesia.

Results:

Sixty-two eyes of 31 patients (17 women, 14 men; mean age ± SD, 47.6 ± 16.8 years) were enrolled. The Standard Patient Evaluation of Eye Dryness score (P < 0.001), noninvasive breakup time (P < 0.001), and interferometric fringe pattern (P < 0.001) were significantly improved after therapy, with 74% of eyes showing a change in the interferometric fringe pattern from 1 characteristic of lipid deficiency to the normal condition. Meibum grade, lid margin abnormality scores, fluorescein breakup time, and CFS were also significantly improved (P < 0.001, P < 0.001, P < 0.001, and P = 0.002, respectively) after treatment, whereas the meiboscore and Schirmer test value remained unchanged.

Conclusions:

IPL-MGX ameliorated symptoms and improved the condition of the tear film in patients with refractory MGD and is therefore a promising treatment option for this disorder.

The effects of 3% diquafosol sodium eye drop application on meibomian gland and ocular surface alterations in the Cu, Zn-superoxide dismutase-1 (Sod1) knockout mice

PURPOSE

The purpose of the study is to investigate the effect of 3% diquafosol sodium eye drops on meibomian gland and ocular surface alterations in the superoxide dismutase-1 (Sod1 ^-/- ) mice in comparison to the wild-type mouse.

METHODS

Three percent diquafosol sodium eye drop was instilled to 20 eyes of 10 50-week-old male Sod1 ^-/- mice and 22 eyes of 11 C57BL/6 strain 50-week-old wild-type (WT) male mice six times a day for 2 weeks. Aqueous tear secretion quantity was measured with phenol red-impregnated cotton threads without anesthesia. Tear film stability and corneal epithelial damage were assessed by fluorescein and lissamine green staining. We also performed oil red O (ORO) lipid staining to evaluate the lipid changes in the meibomian glands. Meibomian gland specimens underwent hematoxylin and eosin staining to examine histopathological changes and meibomian gland acinar unit density after sacrifice. Immunohistochemistry staining was performed using cytokeratin 4, cytokeratin 13, and transglutaminase-1 antibodies. Quantitative real-time polymerase chain reaction for cytokeratin 4, cytokeratin 13, and transglutaminase-1 mRNA expression was also performed.

RESULTS

The aqueous tear quantity, the mean tear film breakup time, and the number of lipid droplets significantly improved in the Sod1 ^-/- mice with treatment. The mean meibomian acinar unit density did not change in the Sod1 ^-/- mice and WT mice after treatment. Application of 3% diquafosol sodium eye drop significantly decreased the corneal fluorescein and lissamine green staining scores in the Sod1 ^-/- mice after 2 weeks. We showed a notable increase in cytokeratin 4, cytokeratin 13 immunohistochemistry staining, and cytokeratin 4, cytokeratin 13 mRNA expressions with a marked decrease in immunohistochemistry staining and significant decline in mRNA expression of transglutaminase-1 after 3% diquafosol sodium treatment.

CONCLUSION

Topical application of 3% diquafosol sodium eye drop improved the number of lipid droplets, tear stability, and tear production which in turn appeared to have a favorable effect on the ocular surface epithelium. Three percent diquafosol sodium eye drop may be a potential treatment for age-related meibomian gland and dry eye disease based on the observations of the current study.

Therapeutic inhibitors for the treatment of dry eye syndrome

INTRODUCTION

Dry eye disease (DED), defined as a multifactorial disease of tears and ocular surface, results in symptoms of discomfort, ocular irritation, visual disturbance and tear film instability. This syndrome is accompanied of ocular surface inflammation and it is produced by a deficient activity of the lacrimal functional unit. In addition, it is associated with systemic autoimmune diseases such as Sjögren´s Syndrome, rheumatoid arthritis, systemic lupus erythematosus and some drug administration. The treatment of dry eye disease is based on the typical signs and symptoms of dry eye, which are associated with hyperosmolarity, ocular surface inflammation, discomfort, visual disturbance, and tear film instability. Areas covered: This review is focused on synthetic drugs currently used in clinical practice, from phase III development onwards to treat the ocular surface signs and symptoms of dry eye disease. Expert opinion: The multifactorial disease and the lack of correlation between signs and symptoms imply that not all the pharmacological approaches will be successful for dry eye. The correct design of the clinical trials, with appropriate endpoints, and the type of dry eye under study are complicated but mandatory. The anti-inflammatory and secretagogues drugs are both the main compounds to currently treat the dry eye disease.

Effect of topical 3% diquafosol sodium on eyes with dry eye disease and meibomian gland dysfunction

Purpose

To prospectively evaluate the effect of topical diquafosol sodium on eyes with dry eye disease (DED) and meibomian gland dysfunction (MGD).

Patients and methods

The subjects were consecutive patients diagnosed with both DED and MGD at Inouye Eye Hospital between March and September of 2016. The subjects were administered topical 3% diquafosol sodium ophthalmic solution six times a day for 3 months. At each study visit, subjects underwent slit-lamp examination and completed MGD symptoms and dry eye-related quality of life score (DEQS) questionnaires. Meibum quality (meibum score) and meibomian gland loss (meiboscore) were evaluated. Tear lipid layer thickness was measured in both eyes with an ocular surface interferometer immediately after clinic arrival and 20 minutes after instillation of one drop of topical diquafosol.

Results

Thirteen patients (3 men, 10 women) with a mean age of 69.5±8.3 years completed the 3-month study. The number of telangiectasia and plugged meibomian gland orifices significantly decreased from baseline after 1 month of diquafosol use. The meibum score and the meiboscore significantly decreased from baseline at 3 months. Also, the lipid layer thickness was greater after diquafosol administration than before administration at baseline and 1, 2, and 3 months by 12.2, 11.5, 9.5, and 17.0 nm, respectively, but this difference was only significant at 3 months (p=0.039). The DEQS ocular symptom (p=0.065) and MGD questionnaire (p=0.081) scores tended to be lower than baseline at 3 months.

Conclusion

Diquafosol sodium ophthalmic solution improves DED- and MGD-related signs in eyes with MGD.