The pathology of dry eye: the interaction between the ocular surface and lacrimal glands

Investigation of the relationship between ocular sarcoidosis and dry eye

A relationship between ocular sarcoidosis (OcSar) and dry eye (DE) has previously been reported. Here we investigated the tear function in OcSar, and the other uveitis, Vogt–Koyanagi–Harada disease (VKH), to elucidate the association between OcSar and DE. This study involved 27 eyes of 27 female OcSar patients [mean age: 67.3 ± 13.5 (SD) years], 18 eyes of 18 female VKH patients (53.1 ± 14.1 years), and 17 eyes of 17 female healthy control subjects (59.7 ± 9.6 years). In all examined eyes, tear meniscus height (TMH, mm), fluorescein breakup time (FBUT, s), scoring of keratoconjunctival epithelial damage (ED), and the Schirmer 1 test (ST1, mm/5 min) were analyzed. In the OcSar patients, VKH patients, and control subjects, the respective TMH, FBUT, ED, and ST1 values (mean ± SD) were 0.26 ± 0.10, 0.24 ± 0.09, and 0.24 ± 0.08, 4.3 ± 2.5, 7.3 ± 2.9, and 6.3 ± 3.1, 1.1 ± 1.1, 0.7 ± 0.8, and 0.1 ± 0.3, and 12.9 ± 10.5, 21.5 ± 12.1, and 24.3 ± 10.5. Statistically, the ST1 values were significantly lower in the OcSar patients than in the VKH patients (P = 0.004) and control subjects (P = 0.001). ST1 findings revealed that the neural reflex arc and lacrimal gland system, which attenuate the vicious cycle between the tear film and ocular surface epithelium in DE, are significantly impaired in OcSar cases, thus indicating a possible association between OcSar and DE.

Influence of Cytokines on Inflammatory Eye Diseases: A Citation Network Study

Background: The main objective of this study was to use citation networks to analyze the relationship between different publications on the impact of cytokines at an ocular level and their authors. Furthermore, the different research areas will be identified, and the most cited publications determined. Methods: A search was performed in the Web of Science (WoS) database using the following keywords: “cytokine”, “inflammatory”, and “eye disease” for the period from 1990 to October 2021. The Citation Network Explorer and the CiteSpace software were then used to analyze the different publications. Results: 3127 publications with 8955 citations generated on the web were found. The largest number of publications on this topic emerged in 2018 and the authors with the largest number of publications addressing this area of research were Peizeng Yang (1.4%), Aize Kijlstra (1.3%), and Stephen C. Pflugfelder (1.2%). Conclusions: the citation network has provided a comprehensive and objective analysis of the main studies on the influence of cytokines in ocular inflammatory diseases.

Ocular Autonomic Nervous System: An Update from Anatomy to Physiological Functions

The autonomic nervous system (ANS) confers neural control of the entire body, mainly through the sympathetic and parasympathetic nerves. Several studies have observed that the physiological functions of the eye (pupil size, lens accommodation, ocular circulation, and intraocular pressure regulation) are precisely regulated by the ANS. Almost all parts of the eye have autonomic innervation for the regulation of local homeostasis through synergy and antagonism. With the advent of new research methods, novel anatomical characteristics and numerous physiological processes have been elucidated. Herein, we summarize the anatomical and physiological functions of the ANS in the eye within the context of its intrinsic connections. This review provides novel insights into ocular studies.

Identification of tear-based protein and non-protein biomarkers: Its application in diagnosis of human diseases using biosensors

Discovery of robust, selective and specific biomarkers are important for early diagnosis and monitor progression of human diseases. Eye being a common target for several human diseases, vision impediment and complications are often associated with systemic and ocular diseases. Tears are bodily fluids that are closest to eye and are rich in protein content and other metabolites. As a biomarker repository, it advantages over other bodily fluids due to the ability to collect it non-invasively. In this review, we highlight some recent advancements in identification of tear-based protein biomarkers like lacryglobin and cystatin SA for cancer; interleukin-6 and immunoglobulin-A antibody for COVID-19; tau, amyloid-β-42 and lysozyme-C for Alzheimer's disease; peroxiredoxin-6 and α-synuclein for Parkinson's disease; kallikrein, angiotensin converting enzyme and lipocalin-1 for glaucoma; lactotransferrin and lipophilin-A for diabetic retinopathy and zinc-alpha-2 glycoprotein-1, prolactin and calcium binding protein-A4 for eye thyroid disease. We also discussed identification of tear based non-protein biomarkers like lysophospholipids and acetylcarnitine for glaucoma, 8-hydroxy-2'-deoxyquanosine and malondialdehyde for thyroid eye disease. We elucidate technological advancement in developing tear-based biosensors for diagnosis and monitoring diseases such as diabetes, diabetic retinopathy and Alzheimer's disease. Altogether, the study of tears as potential biomarkers for early diagnosis of human diseases is promising.

Looking deeper into ocular surface health: an introduction to clinical tear proteomics analysis

Ocular surface diseases are becoming more prevalent worldwide. Reasons for this include the ongoing population ageing and increasing use of digital displays, although ophthalmologists have a wide selection of tools, which can be implemented in the evaluation of the ocular surface health, methods, which enable the in-depth study of biological functions are gaining more interest. These new approaches are needed, since the individual responses to ocular surface diseases and treatments can vary from person to person, and the correlations between clinical signs and symptoms are often low. Modern mass spectrometry (MS) methods can produce information on hundreds of tear proteins, which in turn can provide valuable information on the biological effects occurring on the ocular surface. In this review article, we will provide an overview of the different aspects, which are part of a successful tear proteomics study design and equip readers with a better understanding of the methods most suited for their MS-based tear proteomics study in the field of ophthalmology and ocular surface.

Stimulating Tear Production: Spotlight on Neurostimulation

Dry eye disease (DED) affects up to one-third of the global population. Traditional therapies, including topical lubricants, have been employed with variable success in the treatment of DED. Recently, neurostimulation of the lacrimal functional unit (LFU) has emerged as a promising alternative therapy for DED. In this review, we describe the neuroanatomical and pathophysiological considerations of DED and the LFU that make neurostimulation a viable therapeutic alternative. We further detail the various neurostimulatory approaches taken thus far-from implanted stimulators to external devices to chemical neurostimulation. Existing studies reveal the strengths of the neurostimulatory approach in increasing tear volume and improving dry eye symptoms, but further studies are needed to elucidate its true potential in treatment of DED.

The Role of Neuropeptides in Pathogenesis of Dry Dye

Neuropeptides are known as important mediators between the nervous and immune systems. Recently, the role of the corneal nerve in the pathogenesis of various ocular surface diseases, including dry eye disease, has been highlighted. Neuropeptides are thought to be important factors in the pathogenesis of dry eye disease, as suggested by the well-known role between the nervous and immune systems, and several recently published studies have elucidated the previously unknown pathogenic mechanisms involved in the role of the neuropeptides secreted from the corneal nerves in dry eye disease. Here, we reviewed the emerging concept of neurogenic inflammation as one of the pathogenic mechanisms of dry eye disease, the recent results of related studies, and the direction of future research.

New Indicator of Children's Excessive Electronic Screen Use and Factors in Meibomian Gland Atrophy

PURPOSE

To evaluate the association of children's daily electronic screen use with severe meibomian gland atrophy (MGA).

DESIGN

Retrospective cross-sectional study.

METHODS

Children (aged 6-17years) presenting at clinical practice December 2016 - October 2017 were evaluated for ≥grade 2 MGA vs age-matched controls with insignificant atrophy (<grade 1 atrophy). Questionnaires assessed dry eye symptoms, daily electronic screen use hours, diet, and outdoor time. Meibography imaging assessed for severe meibomian gland atrophy (≥grade 2 atrophy; ≥1 eyelid on validated, 4-point, ImageJ scale: 0 [normal] - 3 [severe]). Autoimmune disease biomarker positivity was assessed in 16 severe meibomian gland atrophy cases after being found relevant in firstcase.

RESULTS

A total of 172 children were evaluated. Patients with known meibomian gland atrophy causes or poor-quality meibographies were excluded. Forty-one met inclusion criteria (mean age, 11 years; 49% female): 17 cases had severe meibomian gland atrophy; 24 controls had insignificant gland atrophy. All severe meibomian gland atrophy cases had ocular symptoms/signs of dry eye disease including corneal neovascularization (29%), best-corrected visual acuity loss (41%), and central corneal neovascularization (14%). No controls had significant dry eye symptoms/signs. Controls had lower/"better" meibogrades vs cases (P < .01). In severe meibomian gland atrophy cases, 86% reported ≥4 hours of daily electronic screen use; 50% reported ≥8 hours. No controls exceeded 2 hours. Increased electronic screen use was positively associated with increased/"worse" meibogrades (odds ratio: 2.74; 95% confidence interval, 1.39-5.41). In 16 severe meibomian gland atrophy cases, 62.5% tested positive for autoimmune biomarker(s), though none had systemic symptoms: 18.8% rheumatoid factor; 6.25% SS-A/SS-B; 31.3% early Sjögren syndrome biomarkers; 6.25% ANA-positive/RF-negative. Autoimmune disease biomarker positivity was not significantly associated with severe meibomian gland atrophy vs controls (P = .34, right-eye; P = .71, left-eye).

CONCLUSIONS

Children's excessive electronic screen use is associated with severe meibomian gland atrophy. Further research is needed to establish formal electronic screen use limits based on meibography grade and evaluate correlation of autoimmune disease biomarker positivity in children with severe meibomian gland-atrophy.

Efficacy of Switching from Cyclosporine A 0.05% Anionic Emulsion to Cyclosporine A 0.1% Cationic Emulsion in Patients with Dry Eye Associated with Sjögren's Syndrome

Purpose: To evaluate the clinical efficacy of switching from cyclosporine A (CsA) 0.05% anionic emulsion (CsA AE) to CsA 0.1% cationic emulsion (CsA CE) in patients with dry eye (DE) associated with Sjögren's syndrome (SS). Methods: Forty patients with SS-associated DE who were unresponsive to CsA AE for 6 months were enrolled. After baseline measurements, the CsA AE was switched to CsA CE. The ocular surface disease index (OSDI), Sjögren's International Collaborative Clinical Alliance (SICCA), and Schirmer's test scores and tear film breakup time (TBUT) were evaluated at baseline and 1 and 3 months after switching. Results: Two patients dropped out, and 38 were analyzed. OSDI and SICCA ocular staining scores were significantly reduced at 1 and 3 months after switching, compared with the baseline scores (all P < 0.01). Although no significant changes were noted in the corneal staining scores (CSSs), patients with higher baseline CSS (≥4) showed an improvement in the scores at 1 month (P = 0.03) and 3 months (P = 0.01) after switching. There were no significant changes in TBUT and Schirmer's test scores during the follow-up periods. Conclusions: In patients with SS-associated DE, switching from CsA AE to CsA CE was effective in improving ocular symptoms and conjunctival staining. In addition, corneal staining was decreased in patients with severe keratitis.

Benzalkonium chloride-induced myofibroblastic transdifferentiation of Tenon's capsule fibroblasts is inhibited by coculture with corneal epithelial cells or by interleukin-10

Benzalkonium chloride (BAC) is used as a preservative in eyedrops but induces subconjunctival fibrosis that can result in failure of glaucoma surgery. Tenon's capsule fibroblasts in subconjunctival tissue interact with the corneal epithelium through tear fluid. With the use of a coculture system, we have now investigated the effect of human corneal epithelial (HCE) cells on myofibroblastic transdifferentiation of human Tenon fibroblasts (HTFs) induced by BAC (5 × 10^-6%). Immunofluorescence and immunoblot analyses revealed that the BAC-induced expression of α smooth muscle actin (αSMA) in HTFs was suppressed by coculture of these cells with HCE cells (p < 0.01). The concentration of interleukin-10 (IL-10) in culture supernatants of BAC-treated HTFs was increased by coculture with HCE cells (17.26-fold, vs. coculure, p < 0.001). Immunofluorescence and immunoblot analyses also showed that exogenous IL-10 (300 pg/ml) suppressed the BAC-induced expression of αSMA by 43.65% (p < 0.05) as well as the nuclear translocation of myocardin-related transcription factor-A (MRTF-A) by 39.32% (p < 0.01) in HTFs cultured alone. Our findings suggest that corneal epithelial cells may protect against subconjunctival fibrosis by maintaining IL-10 levels and preventing the MRTF-A-dependent transdifferentiation of HTFs into myofibroblasts.

Is the Conjunctiva a Potential Target for Advanced Therapy Medicinal Products?

The conjunctiva is a complex ocular tissue that provides mechanical, sensory, and immune protection for the ocular surface. It is affected by many diseases through different pathological mechanisms. If a disease is not treated and conjunctival function is not fully restored, the whole ocular surface and, therefore, sight is at risk. Different therapeutic approaches have been proposed, but there are still unsolved conjunctival alterations that require more sophisticated therapeutic options. Advanced therapy medicinal products (ATMPs) comprise a wide range of products that includes cell therapy, tissue engineering, and gene therapy. To the best of our knowledge, there is no commercialized ATMP specifically for conjunctival treatment yet. However, the conjunctiva can be a potential target for ATMPs for different reasons. In this review, we provide an overview of the advances in experimental phases of potential ATMPs that primarily target the conjunctiva. Important advances have been achieved through the techniques of cell therapy and tissue engineering, whereas the use of gene therapy in the conjunctiva is still marginal. Undoubtedly, future research in this field will lead to achieving commercially available ATMPs for the conjunctiva, which may provide better treatments for patients.

The two-faced effects of nerves and neuropeptides in corneal diseases

Corneal nerves are instrumental to maintain cornea integrity through regulation of key physiological functions such as tear secretion, blink reflex, and neuropeptide turnover. Corneal nerve injury/stimulation can follow many insults including mechanical/chemical trauma, infections and surgeries. Nerve disruption initiates a process named neurogenic inflammation which leads to edema, pain, and recruitment and activation of leukocytes. Interestingly, leukocyte influx in the cornea can further damage nerves by releasing inflammatory mediators-including neuropeptides. The clinical outcome of neuroinflammation can be beneficial or detrimental to corneal integrity. On one side, it ensures prompt wound healing and prevents infections. On the other, prolonged and/or deranged neuroinflammation can permanently disrupt corneal integrity and impair vision. The cornea is an ideal site to study peripheral neuroinflammation and neurogenic inflammation since it receives the highest density of sensory nerves of the entire body. We will review the corneal nerve anatomy and neurochemistry, discuss the beneficial and detrimental effects of neurogenic inflammation in corneal wound healing, inflammatory processes, and pain. We will also examine the emerging remote impact of corneal nerve disruption on the trigeminal ganglion and the brain, highlighting the key role of neuropeptide Substance P. Finally, we will discuss the clinical relevance of such neuroinflammatory network in the context of severe and highly prevalent ocular diseases, including potential treatments.

Acute Inhibitory Effects of Antidepressants on Lacrimal Gland Secretion in the Anesthetized Rat

Purpose

Patients that medicate with antidepressants commonly report dryness of eyes. The cause is often attributed to the anticholinergic properties of the drugs. However, regulation of tear production includes a substantial reflex-evoked component and is regulated via distinct centers in the brain. Further, the anticholinergic component varies greatly among antidepressants with different mechanisms of action. In the current study it was wondered if acute administration of antidepressants can disturb production of tears by affecting the afferent and/or central pathway.

Methods

Tear production was examined in vivo in anesthetized rats in the presence or absence of the tricyclic antidepressant (TCA) clomipramine or the selective serotonin reuptake inhibitor (SSRI) escitalopram. The reflex-evoked production of tears was measured by challenging the surface of the eye with menthol (0.1 mM) and cholinergic regulation was examined by intravenous injection with the nonselective muscarinic agonist methacholine (1–5 µg/kg).

Results

Acute administration of clomipramine significantly attenuated both reflex-evoked and methacholine-induced tear production. However, escitalopram only attenuated reflex-evoked tear production, while methacholine-induced production of tears remained unaffected.

Conclusions

This study shows that antidepressants with different mechanisms of action can impair tear production by attenuating reflex-evoked signaling. Further, antimuscarinic actions are verified as a likely cause of lacrimal gland hyposecretion in regard to clomipramine but not escitalopram. Future studies on antidepressants with different selectivity profiles and mechanisms of action are required to further elucidate the mechanisms by which antidepressants affect tear production.

The ocular surface immune system through the eyes of aging

Since the last century, advances in healthcare, housing, and education have led to an increase in life expectancy. Longevity is accompanied by a higher prevalence of age-related diseases, such as cancer, autoimmunity, diabetes, and infection, and part of this increase in disease incidence relates to the significant changes that aging brings about in the immune system. The eye is not spared by aging either, presenting with age-related disorders of its own, and interestingly, many of these diseases have immune pathophysiology. Being delicate organs that must be exposed to the environment in order to capture light, the eyes are endowed with a mucosal environment that protects them, the so-called ocular surface. As in other mucosal sites, immune responses at the ocular surface need to be swift and potent to eliminate threats but are at the same time tightly controlled to prevent excessive inflammation and bystander damage. This review will detail how aging affects the mucosal immune response of the ocular surface as a whole and how this process relates to the higher incidence of ocular surface disease in the elderly.

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.

In the eye of the storm: SARS-CoV-2 infection and replication at the ocular surface?

Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) first emerged in December 2019 and spread quickly causing the coronavirus disease 2019 (COVID‐19) pandemic. Recent single cell RNA‐Seq analyses have shown the presence of SARS‐CoV‐2 entry factors in the human corneal, limbal, and conjunctival superficial epithelium, leading to suggestions that the human ocular surface may serve as an additional entry gateway and infection hub for SARS‐CoV‐2. In this article, we review the ocular clinical presentations of COVID‐19 and the features of the ocular surface that may underline the overall low ocular SARS‐CoV‐2 infection. We critically evaluate the studies performed in nonhuman primates, ex vivo organ culture ocular models, stem cell derived eye organoids and the differences in infection efficiency observed in different parts of human ocular surface epithelium. Finally, we highlight the additional work that needs to be carried out to understand the immune response of the ocular surface to SARS‐CoV‐2 infection, which can be translated into prophylactic treatments that may be applied to other organ systems.

Applying a dual-Scheimpflug camera to measure tear film thickness

PURPOSE

To assess the tear film thickness in healthy individuals by using a dual-Scheimpflug camera and topical 0.1% fluorescein.

METHODS

A prospective study on healthy individuals who underwent a bilateral tomography examination using the GALILEI dual-Scheimpflug with assessments of the thinnest and central corneal thickness (TCT and CCT, respectively), at baseline and 1 min after applying 2 and 4 µl of 0.1% fluorescein (30 min apart) under topical anesthesia with Oxybuprocaine 0.4%. Inclusion criteria were lack of dry eye disease symptoms and exclusion criteria were contact lens usage, eye drops usage, previous refractive surgery or any ocular surgery. All individuals scored zero on the ocular surface disease index (OSDI) questionnaire.

RESULTS

A total of 62 eyes of 31 participants were included in this study. The mean age was 35.3 ± 10.88 (range 18-62). The mean TCT in was 549.16 µm in the right eye (RE) and 547.84 µm in the left eye (LE). After instillation of 2 µl of 0.1% fluorescein mean TCT increase by 27.84 µm in the RE and by 26.35 µm in the LE. CCT change was 27.58 µm increase in RE and 27.23 µm increase in LE. After instillation of 4 µl of 0.1% fluorescein the mean increase in TCT and CCT were 30.09 and 30.26 µm for OD and 28.33 and 30.15 µm for OS respectively. Comparison between the post instillation of 2 and 4 µl measurements showed no significant differences.

CONCLUSION

Combining a dual-Scheimpflug camera and 0.1% fluorescein may serve as a method to assess the pre-corneal tear film.

Circadian clock regulates tear secretion in the lacrimal gland

Although diurnal variations have been observed in tear film parameters in various species, the molecular mechanisms that control circadian tear secretion remain unclear. The aim of our study was to evaluate the role of clock genes in the lacrimal gland (LG) in regulation of tear secretion. Tear volume was measured by cotton thread test in core clock genes deficient (Cry1^-/-Cry2^-/--) mice which are behaviorally arrhythmic. Real-time quantitative RT-PCR was used to examine expression profiles of core clock genes in the LG including Per1, Per2, Per3, Clock, Bmal1. All experiments were performed under a 12 h of light and 12 h of darkness (LD) and constant dark (DD) conditions. Under both LD and DD conditions, diurnal and circadian rhythms were observed in tear secretion of wild-type mice with tear volume increased in the objective and subjective night while disruption in diurnal and circadian variations of tear secretion were found in Cry1^-/-Cry2^-/--mice. In wild-type mice, the expression level of major clock genes in the LG showed oscillatory patterns under both LD and DD conditions. In contrast, expression clock genes in the lacrimal gland of Cry1^-/-Cry2^-/-- mice showed complete loss of oscillation regardless of environmental light conditions. These findings confirmed the presence of diurnal and circadian rhythms of tear secretion and provided evidences supporting a critical role for the clock in the control of tear secretion.

Can lacrimal punctum size links to the severity of dry eye disease?

To investigate if larger punctum size links to the severity of dry eye disease (DED) and perhaps, punctum size inspection can be adopted to become one of the DED evaluations for practitioners. The records of 200 eyes of 114 patients that had temporary collagen punctum plugs due to severe DED (Level 2 to Level 4) from January 1, 2017, to July 31, 2018, were reviewed for the size of the plugs. Lacrimal punctum size of those eyes was approximated according to the size of vertical canalicular soft collagen plug (from 0.3 to 0.5 mm diameter, Oasis, Lacrimedics, Glendora, CA, USA). The dry eye severity grading from the International Dry Eye WorkShop was used to grade the level of the severity of DED. Those eyes classified as Level 2 and above were considered as severe due to the presentation of moderate-to-diffuse corneal staining and symptomatic. To assess if there is a correlation between punctum size and the severity of DED, the Spearman's rank correlation coefficient was calculated. Of the 200 Level 2 and above eyes, 131 (66%) eyes had a large punctum (≥0.5 mm). Punctum size larger than 0.4 mm was 95%. The estimated Spearman's ρ was 0.16. This indicates a statistical significant positive correlation (P = 0.02) between larger punctum size and higher level of DED. The larger size of lacrimal punctum may link to the severity of DED. Punctum inspection may be adopted to become one parameter for DED evaluation for practitioners.

Comparison of Treatment Effect and Tolerance of the Topical Application of Mizoribine and Cyclosporine A in a Mouse Dry Eye Model

Purpose

To compare the treatment effects and tolerability of a topical application of mizoribine (MZR) and cyclosporine A (CsA) eye drops (Restasis; Allergan, Inc., Irvine, CA, USA) in a mouse dry eye model.

Methods

C57BL/6 mice subjected to desiccating stress (DS) were treated with 0.05% MZR in phosphate-buffered saline (PBS) or Restasis eye drops four times a day for 5 days. Untreated mice served as control. Tear secretion, Oregon green dextran staining, and the conjunctival goblet cell quantity were evaluated. The apoptosis and matrix metalloproteinase 9 (MMP-9) in the ocular surface, conjunctival CD4, and T helper–related cytokines were verified. The ocular tolerance of these two drugs was evaluated by observing the mice's behavioral changes.

Results

Topical administrations of MZR or Restasis both increased tear production, maintained goblet cell density, and improved corneal barrier function. Both MZR and Restasis suppressed the expression of MMP-9 and apoptosis in the ocular surface. Meanwhile, both MZR and Restasis decreased the infiltration of CD4⁺ T cells, reversed the production of interferon-γ, interleukin (IL)–17A, and IL-13 in conjunctiva under DS. The abovementioned efficacies between these two eye drops were not statistically significant. However, the number of scratching and wiping behaviors in the MZR-treated group was significantly less than in the Restasis-treated group.

Conclusions

MZR (0.05% in PBS) could be a good competitive product for Restasis because of the comparable treatment effect in dry eye diseases and better ocular tolerability in ocular itch and pain.

Translational Relevance

This study provided an immunosuppressive agent comparable to Restasis for the treatment of dry eye disease.

Efficacy and Safety of Sodium Hyaluronate/chondroitin Sulfate Preservative-free Ophthalmic Solution in the Treatment of Dry Eye: A Clinical Trial

Purpose: To evaluate the efficacy of a preservative free sodium hyaluronate/chondroitin sulfate ophthalmic solution (SH/CS-PF) in patients with dry eye disease (DED).Methods: This was a randomized phase IV, multicentric, prospective, double-blind clinical trial. Intent-to-treat (ITT) and per-protocol (PP) analyses were performed. Patients were assigned to receive either SH/CS-PF, Systane® Ultra (PEG/PG) or Systane® Ultra PF (PEG/PG-PF) for 90 days. A total of 326 patients were included in the ITT, and 217 in the PP analysis. Efficacy endpoints were goblet cell density, Nelson's grades (conjunctival impression cytology), tear break-up time (TBUT), Ocular Surface Disease Index (OSDI), and Schirmer's test. Other parameters included were tolerability, measured by the ocular symptomatology; and safety, measured through corneal staining, intraocular pressure, visual acuity and adverse events.Results: In the ITT, there was a significant increase in mean goblet cell density in all treatments compared with their baseline (28.4% vs 21.4% and 30.8%), without difference between arms (p = .159). Eyes exposed to SH/CS-PF, PEG/PG and PEG/PG-PF showed Grade 0-I squamous metaplasia (85.5%, 87.9% and 93.2%, respectively). Similar improvements were observed for TBUT (1.24 ± 2.3s vs 1.27 ± 2.4s and 1.39 ± 2.3s) and OSDI scores at day 90 (-8.81 ± 8.6 vs -7.95 ± 9.2 and -8.78 ± 9.8), although no significant intergroup difference was found. Schirmer's test also presented improvement compared to baseline (1.38 ± 4.9 vs 1.50 ± 4.7 and 2.63 ± 5.9), with a significantly higher variation for PEG/PG-PF. There were no significant differences between treatments for any tolerability and safety parameter, nor between ITT and PP analyses for any outcome.Conclusions: The topical application of SH/CS-PF is as effective, safe and well tolerated as that of PEG/PG or PEG/PG-PF. The results suggest that SH/CS-PF may lead to normalization of clinical parameters and symptom alleviation in patients treated for DED.

Impact of corneal refractive surgery on the precorneal tear film

Corneal refractive surgeries are one of the commonly performed procedures for correction of refractive errors. Tear film abnormality is the most common postoperative complication of corneal refractive surgeries. Consequently, these procedures represent a clinically significant cause of dry eye disease. The mechanisms which lead to dry eye disease include corneal sensory nerve dysfunction, ocular surface desiccation, glandular apoptosis and ocular surface inflammation. Although transient tear film abnormalities occur in almost all patients following surgery, patients with pre-existing dry eye symptoms or dry eye disease are at significant risk of developing more severe or long-term ocular surface disease. As such, careful patient selection and preoperative evaluation is essential to ensuring successful surgical outcomes. This is particularly important with LASIK which has the strongest association with dry eye disease. Appropriate surface lubrication and anti-inflammatory therapy remains the cornerstone treatment. Timely and effective management is important to facilitate visual rehabilitation and reduce the risk of secondary complications. In this review we describe the causes, pathophysiology, risk factors, manifestations, and management of tear film dysfunction and dry eye disease following corneal refractive surgery.

Mouse Models of Sjögren's Syndrome with Ocular Surface Disease

Sjögren’s syndrome (SS) is a systemic rheumatic disease that predominantly affects salivary and lacrimal glands resulting in oral and ocular dryness, respectively, referred to as sicca symptoms. The clinical presentation of ocular dryness includes keratoconjunctivitis sicca (KCS), resulting from the inflammatory damage to the ocular surface tissues of cornea and conjunctiva. The diagnostic evaluation of KCS is a critical component of the classification criteria used by clinicians worldwide to confirm SS diagnosis. Therapeutic management of SS requires both topical and systemic treatments. Several mouse models of SS have contributed to our current understanding of immunopathologic mechanisms underlying the disease. This information also helps develop novel therapeutic interventions. Although these models address glandular aspects of SS pathology, their impact on ocular surface tissues is addressed only in a few models such as thrombospondin (TSP)-1 deficient, C57BL/6.NOD.Aec1Aec2, NOD.H2^b, NOD.Aire KO, and IL-2Rα (CD25) KO mice. While corneal and/or conjunctival damage is reported in most of these models, the characteristic SS specific autoantibodies are only reported in the TSP-1 deficient mouse model, which is also validated as a preclinical model. This review summarizes valuable insights provided by investigations on the ocular spectrum of the SS pathology in these models.

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.

Integration of paper microfluidic sensors into contact lenses for tear fluid analysis

In this article, using the integration of paper microfluidics within laser-inscribed commercial contact lenses, we demonstrate the multiplexed detection of clinically relevant analytes including hydrogen ions, proteins, glucose, nitrites and l-ascorbic acid, all sampled directly from model tears. In vitro measurements involved the optimization of colorimetric assays, with readouts collected, stored and analyzed using a bespoke Tears Diagnostics smartphone application prototype. We demonstrate the potential of the device to perform discrete measurements either for medical diagnosis or disease screening in the clinic or at the point-of-care (PoC), with future applications including monitoring of ocular infections, uveitis, diabetes, keratopathies and assessing oxidative stress.

Role of diurnal variation of corneal sensory processing in contact lens discomfort

PURPOSE

To examine the diurnal variation of corneal threshold and suprathreshold sensory processing, symptoms, and tear secretion in symptomatic and asymptomatic contact lens (CL) wearers and controls.

METHODS

26 symptomatic and 25 asymptomatic CL wearers and 15 asymptomatic non-CL wearing controls participated. Cooling thresholds, symptoms and tear meniscus height (TMH) were measured on each of 3 measurement days (random order) on the following schedules; Day-1 within 1 h of awakening (Baseline) and 3, 6 and 9 h later, Day-2 baseline and 9 h later (CLs worn in CL group) and Day-3 baseline and 9 h later. Magnitudes estimates for threshold-scaled suprathreshold stimuli were also estimated on Day-3. Data were analyzed using mixed models and repeated measures ANOVA.

RESULTS

Cooling thresholds for the symptomatic group were lower and decreased over Day-1 (p < 0.008) and after 8 h of CL wear on Day-2 (p < 0.001) and were paralleled by increased symptoms (all p < 0.001), whereas minimal variations were found in the asymptomatic and control groups. Magnitude estimates for suprathreshold stimuli were higher (p ≤ 0.002) in the symptomatic group but did not differ significantly over the day. TMH varied little over time and was lower in the symptomatic group, but the difference was not statistically significant.

CONCLUSION

Corneal sensitivity and symptoms, but not TMH, increased diurnally irrespective of CL wear in symptomatic CL wearers. These results reveal the essential role of neurosensory abnormalities in CL discomfort and suggest involvement of a central mechanism in the diurnally increased symptoms of these patients.

Effect of Dry Eye Disease on the Kinetics of Lacrimal Gland Dendritic Cells as Visualized by Intravital Multi-Photon Microscopy

The lacrimal gland (LG) is the main source of the tear film aqueous layer and its dysfunction results in dry eye disease (DED), a chronic immune-mediated disorder of the ocular surface. The desiccating stress (DS) murine model that mimics human DED, results in LG dysfunction, immune cell infiltration, and consequently insufficient tear production. To date, the immune cell kinetics in DED are poorly understood. The purpose of this study was to develop a murine model of intravital multi-photon microscopy (IV-MPM) for the LG, and to investigate the migratory kinetics and 3D morphological properties of conventional dendritic cells (cDCs), the professional antigen presenting cells of the ocular surface, in DED. Mice were placed in a controlled environmental chamber with low humidity and increased airflow rate for 2 and 4 weeks to induce DED, while control naïve transgenic mice were housed under standard conditions. DED mice had significantly decreased tear secretion and increased fluorescein staining (p < 0.01) compared to naïve controls. Histological analysis of the LG exhibited infiltrating mononuclear and polymorphonuclear cells (p < 0.05), as well as increased LG swelling (p < 0.001) in DED mice compared to controls. Immunofluorescence staining revealed increased density of cDCs in DED mice (p < 0.001). IV-MPM of the LG demonstrated increased density of cDCs in the LGs of DED mice, compared with controls (p < 0.001). cDCs were more spherical in DED at both time points compared to controls (p < 0.001); however, differences in surface area were found at 2 weeks in DED compared with naïve controls (p < 0.001). Similarly, 3D cell volume was significantly lower at 2 weeks in DED vs. the naïve controls (p < 0.001). 3D instantaneous velocity and mean track speed were significantly higher in DED compared to naïve mice (p < 0.001). Finally, the meandering index, an index for directionality, was significant increased at 4 weeks after DED compared with controls and 2 weeks of DED (p < 0.001). Our IV-MPM study sheds light into the 3D morphological alterations and cDC kinetics in the LG during DED. While in naïve LGs, cDCs exhibit a more dendritic morphology and are less motile, they became more spherical with enhanced motility during DED. This study shows that IV-MPM represents a robust tool to study immune cell trafficking and kinetics in the LG, which might elucidate cellular alterations in immunological diseases, such as DED.

The Effect of 0.01% Atropine Eye Drops on the Ocular Surface in Children for the Control of Myopia-The Primary Results from a Six-Month Prospective Study

Purpose

To evaluate the effect of 0.01% atropine eye drops on the ocular surface in children for the control of myopia.

Methods

A total of 72 participants were recruited for this prospective study. Prior to and after 1, 3, and 6 months of 0.01% atropine administration, an ocular surface disease index (OSDI) questionnaire was obtained, Keratograph 5M was used for the measurement of the tear meniscus height (TMH), noninvasive keratographic tear film break-up time (NK-BUT, the first keratographic break-up time, [NK-BUT_first] and the average keratographic break-up time, [NK-BUT_ave]), bulbar redness (BR), meiboscore (MS), and anterior segment optical coherence tomography (AS-OCT) was used to calculate the inferior tear meniscus area (TMA).

Results

After using the 0.01% atropine eye drops for 1 month, 9 subjects complained of discomfort immediately after administration, but this quickly subsided, and 1 subject was temporarily dazzled. All the ocular surface symptoms were mild and occurred rarely. After 3 months, these complaints no longer occurred. Compared with the baseline values, the OSDI scores (0.08 ± 0.28), values of TMH (0.23 ± 0.04 mm), TMA (0.0420 ± 0.0444 mm²), NK-BUT_first (9.39 ± 5.25 s), NK-BUT_ave (10.49 ± 4.94 s), BR (0.63 ± 0.37), and MS (0.89 ± 0.70) did not change significantly after 6 months of 0.01% atropine eye drop administration (P > 0.05).

Conclusion

In this 6-month prospective study, no side effects were observed on the ocular surface after using 0.01% atropine in children.

Prevalence of symptomatic dry eye in breast cancer patients undergoing systemic adjuvant treatment: A cross-sectional study

Objectives

To investigate the prevalence of symptomatic dry eye (SDE) on women undergoing systemic adjuvant therapy for breast cancer and its association with treatment settings.

Methods

Woman undergoing breast cancer systemic adjuvant therapy were included in exposure group. An age-matched non-treatment control group was recruited. This cross-sectional questionnaire-based study utilised validated Ocular Surface Disease Index (OSDI) and NCCN-FACT-Breast Cancer Symptom Index (NFBSI-16) questionnaires to determine the presence of SDE and investigate other breast cancer treatment complications. Additionally, demographic data and medical histories were collected.

Results

Of 423 eligible participants, 200 in each of the control group and the exposure group were included in the final analysis. The prevalence of SDE was 59.0% in breast cancer patients with adjuvant treatment, statistically significantly higher than 25.5% in the control group (P < 0.01). Additionally, exposure group experienced higher prevalence of moderate and severe SDE, which were 20.0% and 19.5% respectively compared with 9.0% and 4.0% in the control group (P = 0.002, P < 0.001). There was a significantly high prevalence of SDE among patients who had received over four cycles of systemic therapy (71.0%, P < 0.001) and the application of targeted therapy (71.2%, P = 0.014). The severity of SDE positively correlated with the cycles of treatment administered.

Conclusion

SDE was significantly predominant in women with breast cancer undergoing systemic adjuvant treatment. Our findings suggest dry eye assessments among patients receiving more than four cycles of chemotherapy or targeted therapy, thus early revealing possible dry eye conditions to both patients and clinicians for further specialized examination and treatment.

•

Breast cancer patients undergoing systemic treatment have fairly high prevalence of symptomatic dry eye.

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Around 40% of them experienced from moderate to severe degree of dry eye.

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The severity of symptomatic dry eye in exposure group showed cycle-dependency.

THC Regulates Tearing via Cannabinoid CB1 Receptors

Purpose

Aqueous deficiency dry eye (ADDE) is a chronic condition affecting millions, with symptoms ranging from a dry itchiness to blurred vision and accompanied by an increased risk of eye infections. ADDE typically arises from disorders of the lacrimal gland that produces tears necessary for eye lubrication. Cannabis users frequently report dry eye, but the basis for this is unknown. If the effects occur via the endogenous cannabinoid signaling system, then this may represent a novel mechanism for the regulation of tearing.

Methods

We examined expression of cannabinoid CB1 receptors in the lacrimal gland using immunohistochemistry, Western blotting, and PCR and tested tetrahydrocannabinol (THC) regulation of tearing in wild-type and CB1-null mice.

Results

We now report that CB1 receptors are expressed in the axons of cholinergic neurons innervating the lacrimal gland. Little if any staining is seen in lacrimal gland epithelial cells (acinar and ductal) or myoepithelial cells (MECs). Activation of CB1 receptors by THC or the cannabinoid agonist CP55940 reduces tearing in male mice. In female mice, THC has no effect, but CP55940 increases tearing. In both sexes, the effect of CP55940 is absent in CB1 knockout mice. CB1 mRNA and protein levels are approximately four- to fivefold higher in males than females. In male knockouts, THC increases tearing, suggesting that THC also acts through different receptors.

Conclusions

Our results suggest a novel, albeit sex-dependent, physiologic basis for the dry eye symptoms experienced by cannabis users: activation of neuronal CB1 receptors in the lacrimal gland reduces tearing.

Intense pulsed light treatment in meibomian gland dysfunction: A concise review

PURPOSE

To review the published literature related to application of intense pulsed light (IPL) for treating meibomian gland dysfunction (MGD).

METHODS

The literature search included the PubMed database and used the keywords "Intense Pulsed Light and Meibomian Gland Dysfunction".

RESULTS

IPL is a new instrumental treatment modality for MGD. This treatment modality was originally developed for use in dermatology and was later adopted in ophthalmology for treating MGD. IPL therapy for MGD can improve tear film stability, meibomian gland functionality, as well as subjective feeling of ocular dryness. However, in the reviewed literature, there was great variability in patient selection, evaluation criteria, and treatment protocols and durations.

CONCLUSION

Numerous studies report that IPL is effective for treating MGD and a safe procedure. There is great potential for further improvements to the procedure, as large comparative studies employing different treatment modalities are lacking.

Local Ocular Surface Alterations in Children with Hashimoto's Thyroiditis

PURPOSE

To evaluate the ocular surface characteristics based on Schirmer's test, tear break-up time (TBUT), and conjunctival impression cytology (CIC) in children with Hashimoto's thyroiditis (HT).

METHODS

This study included 51 children with HT and 53 control subjects. The ocular surface characteristics of participants were assessed via Schirmer's test, TBUT, and CIC. Conjunctival samples were examined cytologically according to the Nelson grading system.

RESULTS

Schirmer's and TBUT results were significantly lower in HT group (p < .05). All samples in both the study and control groups were evaluated as grade 0 according to the Nelson classification (p = .841), however, goblet cell density (GCD) was significantly lower in HT group (p = .001). Schirmer test results were significantly associated with the duration of HT (p = .025, r = -0.311).

CONCLUSION

Hashimoto's thyroiditis without any ocular complaints may cause ocular surface changes with TBUT and Schirmer's. Although CIC analysis showed similar grading results, GCD was significantly decreased in HT group.

Biological functions of tear film

Tears have a vital function to protect and lubricate the ocular surface. Tear production, distribution and clearance is tightly regulated by the lacrimal functional unit (LFU) to meet ocular surface demands. The tear film consists of an aqueous-mucin layer, containing fluid and soluble factors produced by the lacrimal glands and mucin secreted by the goblet cells, that is covered by a lipid layer. The array of proteins, glycoproteins and lipids in tears function to maintain a stable, well-lubricated and smooth optical surface. Tear factors also promote wound healing, suppress inflammation, scavenge free radicals, and defend against microbial infection. Disease and dysfunction of the LFU leads to tear instability, increased evaporation, inflammation, and blurred and fluctuating vision. The function of tear components and the consequences of tear deficiency on the ocular surface are reviewed.

Risk Factors for Dry Eye After Refractive Surgery

PURPOSE

To determine the factors associated with clinically significant dry eye after keratorefractive surgery.

METHODS

This is a large database retrospective study that included consecutive cases of myopic laser in situ keratomileusis (LASIK) or photorefractive keratectomy performed between 2008 and 2016 at Care-Vision Laser Center, Israel. Patients were divided into 2 groups according to whether they developed clinically significant dry eye.

RESULTS

A total of 25,317 right eyes of 25,317 patients, with a mean age of 27.0 ± 8.3 years, were included. Postoperative dry eye developed in 1518 eyes (6.0%). The dry eye group was older (29.2 ± 9.0 vs. 27.6 ± 8.3 yrs, P < 0.001) and had a higher proportion of women (48.5% vs. 44.8%, P = 0.005), lower preoperative spherical equivalent (3.7 ± 2.0 vs. 4.0 ± 2.3D, P < 0.001), lower preoperative best-corrected visual acuity (0.019 ± 0.057 vs. 0.016 ± 0.064 Logarithm of the Minimum Angle of Resolution (LogMAR), P = 0.04), and lower proportion of preoperative soft contact lens wearers (40.6% vs. 45.5%, P < 0.001). In the postoperative dry eye group, a high proportion underwent LASIK (52.4% vs. 38.7%, P < 0.001) and were treated with a 7.0-mm (as opposed to 6.0 mm) optic zone (18.9% vs. 16.3%, P < 0.001). In multivariable analysis, older age [odds ratio (OR) 1.013, P < 0.001], female gender (OR 0.87, P = 0.009), lower preoperative refractive error (OR 1.05, P < 0.001), and LASIK (OR 0.67, P < 0.001) were associated with postoperative dry eye.

CONCLUSIONS

Patients who are of older age, are of female gender, and have a lower preoperative refractive error and those undergoing LASIK are more likely to develop dry eye disease after keratorefractive surgery.

Functional ectodermal organ regeneration as the next generation of organ replacement therapy

In this decade, substantial progress in the fields of developmental biology and stem cell biology has ushered in a new era for three-dimensional organ regenerative therapy. The emergence of novel three-dimensional cell manipulation technologies enables the effective mimicking of embryonic organ germ formation using the fate-determined organ-inductive potential of epithelial and mesenchymal stem cells. This advance shows great potential for the regeneration of functional organs with substitution of complete original function in situ. Organoids generated from multipotent stem cells or tissue stem cells via establishment of an organ-forming field can only partially recover original organ function owing to the size limitation; they are considered ‘mini-organs’. Nevertheless, they hold great promise to realize regenerative medicine. In particular, regeneration of a functional salivary gland and an integumentary organ system by orthotopic and heterotopic implantation of organoids clearly points to the future direction of organ regeneration research. In this review, we describe multiple strategies and recent progress in regenerating functional three-dimensional organs, focusing on ectodermal organs, and discuss their potential and future directions to achieve organ replacement therapy as a next-generation regenerative medicine.

Infrared meibography allows detection of dimensional changes in meibomian glands following intranasal neurostimulation

PURPOSE

Patients with dry eye disease (DED) may suffer from decreased tear break-up time due to meibomian gland (MG) dysfunction. Infrared meibography (IR Meibography) uses infrared wavelength light to visualize meibomian glands in vivo. We aimed to explore the feasibility of using serial IR Meibography imaging to assess morphological changes in MGs as an indirect measure of functionality, following intranasal neurostimulation (ITN).

METHODS

Fifteen DED subjects were prospectively enrolled in a single-center, single-arm study. Changes in MGs were captured using IR meibography (RTVUE-XR, Optovue, Inc. Fremont, CA, USA) on the lower eyelids before and after 3 min of ITN (TrueTear®, Allergan, Dublin, Ireland) use that delivers a microcurrent to sensory neurons of the nasal cavity. The same MGs were selected pre- and post-stimulation, and MG area and perimeter were analyzed by two masked observers.

RESULTS

Mean (±SD) pre- and post-stimulation MG areas were 2,187.60 ± 635.88 μm² and 1,933.20 ± 538.55 μm², respectively. The mean change in area, 254.49 μm², representing an 11.6% reduction following ITN use, was statistically significant (p = 0.001). Mean (±SD) pre- and post-stimulation MG perimeters were 235.9 ± 51.38 μm and 222.2 ± 47.72 μm, respectively. The mean change in perimeter, 13.7 μm, representing a 5.81% reduction following ITN use, was statistically significant (p = 0.012).

CONCLUSIONS

Our study shows that IR meibography can be used to detect immediate changes in gland area and perimeter, an indirect measure of MG activity following intervention by ITN.

Tears - more to them than meets the eye: why tears are a good source of biomarkers in Parkinson's disease

Tears are a known source of biomarkers for both ocular and systemic diseases with particular advantages; specifically, the noninvasiveness of sample collection and a unique and increasingly better-defined protein composition. Here, we discuss our rationale for use of tears for discovery of biomarkers for Parkinson's disease (PD). These reasons include literature supporting changes in tear flow and composition in PD, and the interconnections between the ocular surface system and neurons affected in PD. We highlight recent data on the identification of tear biomarkers including oligomeric α-synuclein, associated with neuronal degeneration in PD, in tears of PD patients and discuss possible sources for its release into tears. Challenges and next steps for advancing such biomarkers to clinical usage are highlighted.

Scleral Lens Sensor for Ocular Electrolyte Analysis

The quantitative analysis of tear analytes in point-of-care settings can enable early diagnosis of ocular diseases. Here, a fluorescent scleral lens sensor is developed to quantitatively measure physiological levels of pH, Na⁺ , K⁺ , Ca²⁺ , Mg²⁺ , and Zn²⁺ ions. Benzenedicarboxylic acid, a pH probe, displays a sensitivity of 0.12 pH units within pH 7.0-8.0. Crown ether derivatives exhibit selectivity to Na⁺ and K⁺ ions within detection ranges of 0-100 and 0-50 mmol L^-1 , and selectivities of 15.6 and 8.1 mmol L^-1 , respectively. A 1,2 bis(o-aminophenoxy)ethane-N,N,-N',N'-tetraacetic-acid-based probe allows Ca²⁺ ion sensing with 0.02-0.05 mmol L^-1 sensitivity within 0.50-1.25 mmol L^-1 detection range. 5-Oxazolecarboxylic acid senses Mg²⁺ ions, exhibiting a sensitivity of 0.10-0.44 mmol L^-1 within the range of 0.5-0.8 mmol L^-1 . The N-(2-methoxyphenyl)iminodiacetate Zn²⁺ ion sensor has a sensitivity of 1 µmol L^-1 within the range of 10-20 µmol L^-1 . The fluorescent sensors are subsequently multiplexed in the concavities of an engraved scleral lens. A handheld ophthalmic readout device comprising light-emitting diodes (LEDs) and bandpass filters is fabricated to excite as well as read the scleral sensor. A smartphone camera application and an user interface are developed to deliver quantitative measurements with data deconvolution. The ophthalmic system enables the assessment of dry eye severity stages and the differentiation of its subtypes.

Histological and immunohistochemical characterization of the porcine ocular surface

The ocular surface of the white domestic pig (Sus scrofa domestica) is used as a helpful model of the human ocular surface; however, a complete histological description has yet to be published. In this work, we studied porcine eyeballs with intact eyelids to describe and characterize the different structures that form the ocular surface, including the cornea and conjunctiva that covers the bulbar sclera, tarsi, and the nictitating membrane. We determined the distribution of goblet cells of different types over the conjunctiva and analyzed the conjunctival-associated lymphoid tissue (CALT). Porcine eyeballs were obtained from a local slaughterhouse, fixed, processed, and embedded in paraffin blocks. Tissue sections (4 μm) were stained with hematoxylin/eosin, Alcian blue/Periodic Acid Schiff, and Giemsa. Slides were also stained with lectins from Arachis hypogaea (PNA) and Helix pomatia (HPA) agglutinins and immunostained with rabbit anti-CD3. We found that the porcine cornea was composed of 6–8 epithelial cell layers, stroma, Descemet’s membrane, and an endothelial monolayer. The total corneal thickness was 1131.0±87.5 μm (mean±standard error of the mean) in the center and increased to 1496.9±138.2 μm at the limbus. The goblet cell density was 71.25±12.29 cells/mm, ranging from the highest density (113.04±37.21 cells/mm) in the lower palpebral conjunctiva to the lowest density (12.69±4.29 cells/mm) in the bulbar conjunctiva. The CALT was distributed in the form of intraepithelial lymphocytes and subepithelial diffuse lymphoid tissue. Lenticular-shaped lymphoid follicles, about 8 per histological section, were also present within the conjunctival areas. In conclusion, we demonstrated that the analyzed porcine ocular structures are similar to those of humans, confirming the potential usefulness of pig eyes to study ocular surface physiology and pathophysiology.

Efficacy of Topical Cyclosporine Nanoemulsion 0.05% Compared with Topical Cyclosporine Emulsion 0.05% and Diquafosol 3% in Dry Eye

PURPOSE

To evaluate the efficacy and safety of cyclosporine nanoemulsion 0.05% compared to cyclosporine emulsion 0.05% and diquafosol sodium 3%.

METHODS

This was a multicenter, randomized, evaluator-masked, active control, parallel, phase IV study. A total of 227 patients were randomly allocated to instill cyclosporine nanoemulsion 0.05% (CN) twice daily, cyclosporine emulsion 0.05% (CE) twice daily, or diquafosol sodium 3% (DQ) six times daily. Non-inferiority of CN was analyzed by primary endpoint (cornea and conjunctival staining scores at week 12). The secondary endpoints were scores of corneal staining, conjunctival staining, tear break-up time, Schirmer test, and Ocular Surface Disease Index at weeks 4 and 12.

RESULTS

Primary endpoints showed statistically significant improvements in all groups. Primary endpoints were -6.60 for the CN group, -5.28 for the CE group, and -6.63 for the DQ group (National Eye Institute scale from 0 to 33), verifying the non-inferiority of CN compared to CE (95% confidence interval, -0.15 to 2.80, Δ>-2.88). In intergroup comparison between CN and CE groups, the CN group had significantly more decreased conjunctival staining score at week 12. Intergroup comparison between CN and DQ groups showed consistent statistically significant improvements in TBUT and Schirmer test in the CN group. In the DQ group, TBUT showed late statistically significant improvement at week 12 and Schirmer test showed relatively short-term statistically significant improvement at week 4.

CONCLUSIONS

Cyclosporine nanoemulsion 0.05% was equivalently efficient compared to cyclosporine emulsion 0.05% and diquafosol sodium 3%. In addition, CN showed significant improvements in several parameters for treatment of dry eyes.

Omega-3 and omega-6 polyunsaturated fatty acids for dry eye disease

BACKGROUND

Polyunsaturated fatty acid (PUFA) supplements, involving omega-3 and/or omega-6 components, have been proposed as a therapy for dry eye. Omega-3 PUFAs exist in both short- (alpha-linolenic acid [ALA]) and long-chain (eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]) forms, which largely derive from certain plant- and marine-based foods respectively. Omega-6 PUFAs are present in some vegetable oils, meats, and other animal products.

OBJECTIVES

To assess the effects of omega-3 and omega-6 polyunsaturated fatty acid (PUFA) supplements on dry eye signs and symptoms.

SEARCH METHODS

CENTRAL, Medline, Embase, two other databases and three trial registries were searched in February 2018, together with reference checking. A top-up search was conducted in October 2019, but the results have not yet been incorporated.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) involving dry eye participants, in which omega-3 and/or omega-6 supplements were compared with a placebo/control supplement, artificial tears, or no treatment. We included head-to-head trials comparing different forms or doses of PUFAs.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methods and assessed the certainty of the evidence using GRADE.

MAIN RESULTS

We included 34 RCTs, involving 4314 adult participants from 13 countries with dry eye of variable severity and etiology. Follow-up ranged from one to 12 months. Nine (26.5%) studies had published protocols and/or were registered. Over half of studies had high risk of bias in one or more domains. Long-chain omega-3 (EPA and DHA) versus placebo or no treatment (10 RCTs) We found low certainty evidence that there may be little to no reduction in dry eye symptoms with long-chain omega-3 versus placebo (four studies, 677 participants; mean difference [MD] -2.47, 95% confidence interval [CI] -5.14 to 0.19 units). We found moderate certainty evidence for a probable benefit of long-chain omega-3 supplements in increasing aqueous tear production relative to placebo (six studies, 1704 participants; MD 0.68, 95% CI 0.26 to 1.09 mm/5 min using the Schirmer test), although we did not judge this difference to be clinically meaningful. We found low certainty evidence for a possible reduction in tear osmolarity (one study, 54 participants; MD -17.71, 95% CI -28.07 to -7.35 mOsmol/L). Heterogeneity was too substantial to pool data on tear break-up time (TBUT) and adverse effects. Combined omega-3 and omega-6 versus placebo (four RCTs) For symptoms (low certainty) and ocular surface staining (moderate certainty), data from the four included trials could not be meta-analyzed, and thus effects on these outcomes were unclear. For the Schirmer test, we found moderate certainty evidence that there was no intergroup difference (four studies, 455 participants; MD: 0.66, 95% CI -0.45 to 1.77 mm/5 min). There was moderate certainty for a probable improvement in TBUT with the PUFA intervention relative to placebo (four studies, 455 participants; MD 0.55, 95% CI 0.04 to 1.07 seconds). Effects on tear osmolarity and adverse events were unclear, with data only available from a single small study for each outcome. Omega-3 plus conventional therapy versus conventional therapy alone (two RCTs) For omega-3 plus conventional therapy versus conventional therapy alone, we found low certainty evidence suggesting an intergroup difference in symptoms favoring the omega-3 group (two studies, 70 participants; MD -7.16, 95% CI -13.97 to -0.34 OSDI units). Data could not be combined for all other outcomes. Long-chain omega-3 (EPA and DHA) versus omega-6 (five RCTs) For long-chain omega-3 versus omega-6 supplementation, we found moderate certainty evidence for a probable improvement in dry eye symptoms (two studies, 130 participants; MD -11.88, 95% CI -18.85 to -4.92 OSDI units). Meta-analysis was not possible for outcomes relating to ocular surface staining, Schirmer test or TBUT. We found low certainty evidence for a potential improvement in tear osmolarity (one study, 105 participants; MD -11.10, 95% CI -12.15 to -10.05 mOsmol/L). There was low level certainty regarding any potential effect on gastrointestinal side effects (two studies, 91 participants; RR 2.34, 95% CI 0.35 to 15.54).

AUTHORS' CONCLUSIONS

Overall, the findings in this review suggest a possible role for long-chain omega-3 supplementation in managing dry eye disease, although the evidence is uncertain and inconsistent. A core outcome set would work toward improving the consistency of reporting and the capacity to synthesize evidence.

Conjunctival Neuropathic and Inflammatory Pain-Related Gene Expression with Contact Lens Wear and Discomfort

Purpose: To identify alterations in neuropathic and inflammatory pain gene expression associated with contact lens (CL) wear and CL discomfort (CLD).Methods: Eight non-wearers, eight asymptomatic CL wearers (CLWs) and eight symptomatic CLWs were included. Conjunctival cells were collected by impression cytology and the mRNA expression levels of 85 genes were analyzed. Differentially expressed genes between non-wearers and CLWs and between asymptomatic and symptomatic CLWs were analyzed. An enrichment analysis was also performed.Results: Twelve genes were upregulated (including IL10, PDYN and PENK) and 28 downregulated (CCL2, IL1A, IL1B, IL2 and NGF) in CLWs (p ≤ 0.050). Eleven genes were upregulated (CCL2, IL1A, IL1B, IL2 and NGF) and nine downregulated (PDYN and PENK) in symptomatic CLWs (p ≤ 0.035). Enriched overrepresented terms were related to pain, neuronal transmission and inflammation.Conclusion: Contact lens wear might produce a desensitization-like mechanism responsible for comfortable CL wear. A malfunction of this mechanism might contribute to CLD.

Meibomian gland dysfunction (MGD), as diagnosed by non-contact infrared Meibography, in dogs with ocular surface disorders (OSD): a retrospective study

Background

Meibomian gland dysfunction (MGD) is one of the possible conditions underlying ocular surface disorders (OSD). Prevalence of MGD in dogs affected by OSD has not yet been reported. We aimed to evaluate the prevalence of MGD among OSD canine patients, which had been assessed by non-contact infrared meibography and interferometry, and to identify MGD associated factors that might guide its diagnosis. Medical records of canine patients examined for OSD between 2016 and 2019 were reviewed. The frequency of MGD was evaluated within different categories (skull conformation, gender, eye and STT-1). The putative MGD risk factors and frequency of MGD within grades of interferometry were evaluated in a regression analysis model and reported as odd ratios (ORs).

Results

One hundred fifty eyes from 81 dogs with OSD were included with median age 75 months (range 3–192) and female representation with 52%. MGD was present in 70% of the examined eyes. MGD risk was higher in males OR_adj = 3.015 (95% CI: 1.395–6.514) (P = 0.005) and older patients OR_adj = 1.207 (95% CI: 1.081–1.348) (P = 0.001). No significant differences were found between left and right eyes (P = 0.66) or between the two types of skull conformation (P = 0.477) and MGD presence. MGD was associated to the lowest lipid layer (LL) thickness, as assessed by interferometry (grade 0) OR = 16.00 (95% CI: 2.104–121.68) (P < 0.001). STT values were not significantly associated with the presence of MGD (P > 0.05).

Conclusions

MGD is a common underlying pathology in OSD. Being male and higher age are risk factors for MGD. An interferometry grade 0 may guide OSD diagnosis towards MGD.

Real-World Treatment Patterns Of Cyclosporine Ophthalmic Emulsion And Lifitegrast Ophthalmic Solution Among Patients With Dry Eye

Purpose

To assess adherence, non-persistence, discontinuation, and switching of topical cyclosporine ophthalmic emulsion 0.05% (CYC) and lifitegrast ophthalmic solution 5% (LIF) use in the real world among patients with dry eye disease (DED).

Design

Retrospective insurance claims study.

Methods

Adult patients with DED and ≥1 prescription claim for CYC or LIF (first claim = index date) in the IBM^® MarketScan^® databases from July 2016 to February 2018 were identified. Eligible patients had continuous medical and pharmacy benefits in the 12 months pre- and post-index periods, and no prior use of the index medication. The proportion of days covered (PDC), adherence, non-persistence, discontinuation, and switching were examined over the 12-month post-index period.

Results

This study included 6537 CYC and 3235 LIF patients. The adherence rate was 5.9% for CYC and 9.7% for LIF; the median PDC was 0.3 for both cohorts. Overall, 70.8% of CYC and 64.4% of LIF patients discontinued treatment with median days to discontinuation of 89 and 29, respectively. Non-persistence was 7.1% for CYC and 6.8% for LIF (median days to discontinuation: 89 and 105). In addition, 5.0% switched from CYC to LIF, and 9.6% switched from LIF to CYC over the post-index period.

Conclusion

Over 60% of DED patients discontinued treatment within 12 months of initiation; the median time to discontinuation was 3 months for CYC and 1 month for LIF. Although this analysis did not capture the reasons why patients discontinued treatment, the results demonstrate there likely exists a significant unmet need amongst DED patients.