Influence of Ophthalmic Solutions on Tear Components

Tear secretion by Diquafosol suppresses the excitability of trigeminal brainstem nuclear complex neurons by reducing excessive P2Y2 expression in the trigeminal ganglion in dry eye rats

The P2Y₂ receptor agonist, diquafosol sodium, is commonly used to treat the signs and symptoms of dry eye disease (DE) patients. Although diquafosol improves tear film stability, the neural mechanisms underlying the reduction in ocular pain are not well defined. This study determined if repeated application of diquafosol reduces the sensitization of nociceptive neurons in the lower trigeminal brainstem nuclear complex (TBNC) via peripheral P2Y₂ mechanisms in a rat model for DE. Diquafosol was applied to the ocular surface daily for 28 days, starting at day 0 or day 14, after exorbital gland removal. The number of eyeblinks, P2Y₂-immunoreactive neurons in the trigeminal ganglion (TG), and correlates of TBNC neural excitability (i.e., cFos protein and phosphorylated extracellular signal-regulated kinase (pERK) expression) were assessed in male rats. Diquafosol increased spontaneous tear volume and reduced the number of ocular surface-evoked eyeblinks in DE rats. Fluorogold-labeled TG neurons that supply the cornea expressed P2Y₂. The number of P2Y₂-immunoreactive neurons was increased in DE rats and suppressed by diquafosol. Diquafosol also reduced the number of cFos- and pERK-immunoreactive neurons in the TBNC in DE rats. These findings suggest that diquafosol, regardless of late-phase treatment, relieves ocular nociception in DE by reducing peripheral P2Y₂ expression.

The Relationship between Subjective Symptoms and Quality of Life in Conjunctivochalasis Patients

The purpose of this study was to evaluate the differences in subjective symptoms between patients with conjunctivochalasis (CCh) and dry eye (DE), and examine the relationship between subjective symptoms and quality of life (QOL). In 75 eyes of 75 CCh patients and 122 eyes of 122 DE patients, 12 subjective symptoms classified into four groups depending on the mechanisms associated with symptoms (ITF: instability of tear film, IF: increased friction, R: reflex, and DTC: delayed tear clearance) were evaluated by use of a visual analogue scale (VAS). Fifteen items related to DE symptoms and their influence on daily life were evaluated by use of the dry eye-related quality-of-life score (DEQS) questionnaire, with overall degree of QOL impairment calculated as a QOL score. The correlation between the Total VAS score and QOL score were evaluated. Between the CCh and DE patients, significant differences in subjective symptoms were found in eye dryness, pain, tearing sensitivity to light, and heavy eyelids, while tearing was higher in CCh. A significant strong correlation was found between QOL score and Total VAS score, ITF, and IF in CCh patients. The QOL of CCh patients is strongly determined by decreased tear-film stability and increased friction during blinking.

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.

Tear Film-Oriented Diagnosis and Tear Film-Oriented Therapy for Dry Eye Based on Tear Film Dynamics

In December 2010 and January 2012, 3% diquafosol sodium ophthalmic solution and 2% rebamipide ophthalmic suspension, respectively, appeared first in Japan as prescription drugs for the treatment of dry eye (DE). Since then, not only the diagnosis and treatment but also the understanding of the pathophysiology of DE have greatly advanced, and a new concept of layer-by-layer diagnosis and treatment for DE, respectively termed "tear-film-oriented diagnosis" (TFOD) and "tear-film-oriented therapy" (TFOT) was born. This new concept is currently in the process of expanding from Japan to other Asian countries. TFOD is the method used for the differential diagnosis of DE, which includes aqueous-deficiency DE (ADDE), decreased wettability DE (DWDE), and increased evaporation DE (IEDE), through the dynamics of tear film (TF) and breakup patterns (BUPs) after the eye is opened. BUPs and/or each diagnosed DE subtype are/is able to distinguish the insufficient components of the ocular surface that are responsible for each BUP in a layer-by-layer fashion. Aqueous fluid, membrane-associated mucins (especially MUC16), and the lipid layer and/or secretory mucins must be insufficient in ADDE, DWDE, and IEDE, respectively, and this allows for a layer-by-layer treatment to be proposed for each BUP via the supplementation of the insufficient components, using the topical therapy currently available. In Japan, TF breakup is regarded as a visible core mechanism for DE, and an abnormal breakup time (i.e., ≤5 seconds) and symptoms are currently used for the diagnosis of DE. Therefore, TFOD and TFOT could be an ideal and practical pathway for clinicians to manage DE.

Tear-film-oriented diagnosis for dry eye

Tear-film (TF) stability protects the ocular surface epithelium from desiccation and is ensured via cooperation between the ocular surface components including constituents of the TF and ocular surface epithelium. Thus, when those components are insufficient or impaired, the TF breakup that initiates dry eye occurs. Recently, new, commercially available eye drops have appeared in Japan that enable TF stabilization via targeted supplementation of deficient ocular surface components. Hence, a new layer-by-layer diagnosis and treatment concept for dry eye, termed tear-film-oriented diagnosis and tear-film-oriented therapy (TFOD and TFOT, respectively), have emerged and become widely accepted in Asian countries and beyond. TFOD is a diagnostic method for dry eye based on the TF dynamics and breakup patterns (BUPs), through which dry-eye subtypes, including aqueous-deficient dry eye, decreased-wettability dry eye, and increased-evaporation dry eye, are diagnosed. BUPs and/or each diagnosed dry-eye subtype can, in a layer-by-layer fashion, reveal the insufficient ocular surface components responsible for the TF breakup. Using these data, the optimal topical TFOT to treat dry eye can be proposed by addressing the TF breakup via the supplementation of the insufficient components. In Japan, TF breakup is now regarded as a visible core mechanism of dry eye, and abnormal breakup time (ie, ≤ 5 seconds) and symptoms are currently considered part of the diagnostic criteria for dry eye. In this review, the importance of TF instability as a core manifestation of dry eye, the molecular mechanism of TF breakup, the concept of TFOD, and the methods for implementing TFOD for TFOT are introduced.

Clinical subtypes of dry eye in youthful clinical sample in Ghana

PURPOSE

To evaluate in a cohort of patients with dry eye disease (DED) the distribution of patients with asymptomatic and symptomatic dry eye involving aqueous deficient or the evaporative subtype of DED.

METHODS

This was a clinic-based cross-sectional study of consecutive patients visiting the University of Cape Coast eye clinic for a comprehensive eye examination. Eligible participants completed the Ocular Surface Disease Index (OSDI), ocular surface staining and tear break up time. Subjects with dry eye (symptomatic or asymptomatic) underwent clinical examination comprising lid margin assessments, meibomian gland expressibility and quality assessments, and Schirmer 1 test.

RESULTS

A total of 172 patients were included in the study. The mean age of the eligible participants was 22.7 (±3.7) years, with a range of 17-35 years. There were 83 males and 89 females in the sample. There was an association between the form of the dry eye whether symptomatic or asymptomatic and sex, (X² = 6.51 df = 1 p = 0.011). The frequency of symptomatic aqueous-deficient dry eye was 9(5.2%) whiles that of the symptomatic evaporative dry eye was 20(11.6%). The frequencies of the asymptomatic aqueous-deficient dry eye and asymptomatic evaporative dry eye were 9(5.2%) and 12(7.0%) respectively. The frequency of symptomatic mixed dry eye was 30(17.4%) and the asymptomatic mixed dry eye was 8(4.7%). The distribution of unclassifiable dry eye among the symptomatic dry eye group was 41(23.8%) and 43(25%) among the asymptomatic dry eye group.

CONCLUSION

The number of patients exhibiting signs of the evaporative dry eye resulting from meibomian gland dysfunction far outnumbers those of aqueous deficient dry eye but there remains a high unclassifiable group with an unknown etiology. Further, studies are needed to explore the other etiology or etiologies of dry eye apart from meibomian gland dysfunction and reduced aqueous production.

Tear instability importance, mechanisms, validity and reliability of assessment

PURPOSE

To examine the factors which contribute to tear stability and the validity and reliability of methods used for assessing tear break up time which is a core part of an examination of tear stability in dry eye patients.

METHODS

A review of publications which are relevant to tear stability and its assessment.

RESULTS

Tear break up time may be more invasive than intended if difficulty avoiding blinking during assessment results in reflex tearing. Notwithstanding control of instilled volume and concentration of fluorescein, on-eye dilution is highly variable according to resident tear volume. Blinking to evenly distribute fluorescein may improve tear and lipid layer thickness so habitual tear function is not assessed. Emphasis on a role for Meibomian gland dysfunction as a cause of tear instability may be appropriate in many cases but ignores the roles for other sources of tear lipid and other non-lipid contributions to tear instability such as aqueous or mucus deficiency, desiccated epitheliopathy or anomalous blinking. Objective less-invasive methods eliminate problems of inter-observer variability and can reliably 'maintain vigilance' over wide areas of the tear layer. However less-invasive results to date include mean tear break up findings which are both shorter and longer than expected for normal controls.

CONCLUSIONS

Fluorescein tear break up time assessments cannot be standardised and less-invasive methods are not yet standardised. Objective less-invasive and subjective fluorescein break up time tests do not appear to be measuring the same tear phenomena although both should be performed before other invasive procedures.

Yeast Surface Display of Antheraea pernyi Lysozyme Revealed α-Helical Antibacterial Peptides in Its N-Terminal Domain

The present study investigated a novel lysozyme ApLyz from the Chinese oak silkmoth, Antheraea pernyi, for its active expression with N- or C-terminus fused to the yeast cell surface, and the antimicrobial activities of the corresponding expressed lysozymes were evaluated. The bactericidal activity of C-terminal fusion of ApLyz surpassed that of the N-terminal fusion, which revealed the implication of an N-terminal stretch of ApLyz in the bactericidal function based on the structural mobility of this region. Two N-terminal peptides of ApLyz (residues 1-15 and 1-32), which primarily consist of amphiphilic α-helices, exerted similar bactericidal efficacy and had a strong preference for the Gram-negative strains. Further investigation revealed that the N-terminal peptides are membrane-targeting peptides causing cell permeabilization and also possess nonmembrane disturbing bactericidal mechanism. Overall, in addition to the key findings of novel bactericidal peptides from silkmoth lysozyme, this work laid the foundation for future improvement of ApLyz by protein engineering.

2D Photonic Crystal Hydrogel Sensor for Tear Glucose Monitoring

Photonic crystal (PC) materials have huge potentials as sensors for noninvasive and real-time monitoring glucose in tears. We developed a glucose-sensitive PC material based on monolayered colloidal crystals (MCCs). Polystyrene nanoparticles were first self-assembled into a highly ordered MCC, and this two-dimensional (2D) template was then coated by a 4-boronobenzaldehyde-functionalized poly(vinyl alcohol) hydrogel. Such a sensor efficiently diffracts visible light, whose structural color could change from red through yellow to green, as the glucose concentration altered from 0 to 20 mM, covering both tears' and bloods' physiological ranges. The sensor also represents a rapid response within 180 s at each titration of glucose, combining the characteristics of high accuracy and sensitivity in detecting the glucose concentration in tears, and this intelligent sensing material presents certain possibility for the frontier point-of-care glucose monitoring.

The effect of rebamipide ophthalmic suspension on ocular surface mucins in soft contact lens wearers

PURPOSE

To evaluate the changes in ocular surface mucins with 2%rebamipide ophthalmic suspension treatment in soft contact lens (SCL) wearers. Rebamipide suspension is a mucin secretagogue approved for the treatment of dry eye syndrome in Japan. In this study, the fluorescence intensity of wheat germ agglutinin conjugate of fluorescein (F-WGA) was used as a marker of membrane-associated mucins, and sialic acid concentration in tear fluids as a marker of secreted mucins.

METHODS

Thirty-two eyes of 16 SCL wearers with discomfort were treated with rebamipide suspension at a dose of one drop in each eye four times daily for two weeks. The parameters of clinical efficacy were tear break-up time, fluorescein staining scores for the cornea and conjunctiva, and Schirmer test values. Fluorescence intensities in the central cornea were measured by fluorophotometry after the application of 5% F-WGA solution. Tears collected by Schirmer test strips were analyzed by high-performance liquid chromatography, and the concentrations of sialic acid, total protein, and the four major tear proteins, namely secretory IgA, lactoferrin, lipocalin-1, and lysozyme were measured.

RESULTS

Significant increases in F-WGA fluorescence intensities (p < 0.005) were seen in the corneal surfaces. Sialic acid concentrations increased over time; however, the differences were not statistically significant. Except for a slight increase in kerato-conjunctival staining scores (p < 0.05) and secretory IgA (p < 0.05), no other significant differences were seen among clinical parameters or tear proteins.

CONCLUSIONS

Topical application of rebamipide suspension significantly increased F-WGA intensity, a marker of membrane-associated mucins in SCL wearers.

Classification of Fluorescein Breakup Patterns: A Novel Method of Differential Diagnosis for Dry Eye

PURPOSE

To investigate the relationship between fluorescein breakup patterns (FBUPs) and clinical manifestations in dry eye cases.

DESIGN

Cross-sectional study.

METHODS

In 106 eyes of 106 subjects (19 male, 87 female; mean age: 64.2 years), FBUPs were categorized into 1 of the following 5 break (B) types: area (AB, n = 19); spot (SB, n = 22); line (LB, n = 24); dimple (DB, n = 19); random (RB, n = 22 eyes); and dry eye-related symptoms using the visual analog scale (VAS, 100 mm = maximum), tear meniscus radius (TMR, mm), tear film lipid layer interference grade (IG) (grades 1-5; 1 = best) and spread grade (SG) (grades 1-4; 1 = best), tear film noninvasive breakup time (NIBUT, seconds), fluorescein breakup time (FBUT, seconds), corneal-epithelial damage (CED) score (15 points = maximum), ocular surface epithelial damage (OSED) score (9 points = maximum), and the Schirmer 1 test (ST1, mm) were examined and compared between each FBUP.

RESULTS

In each FBUP, eye dryness and fatigue were the severest symptoms. Characteristic symptoms were sensitivity to light, heavy eyelids, pain, foreign body sensation, difficulty opening the eye, and discharge for AB, heavy eyelids for SB, and foreign-body sensation for LB. Statistically significant differences were found in TMR (AB-SB, -DB, and -RB; LB-RB), IG (AB-all other FBUP; LB-SB and -DB), and SG (AB-all other FBUPs), FBUT (AB-LB, -DB, and -RB; SB-DB and -RB; LB-RB; DB-RB), and NIBUT (AB-all other FBUPs; SB-DB and-RB, and LB-RB), CED (AB-all other FBUPs; LB-SB, -DB, and -RB) and OSED (AB-SB, -LB, and -DB; LB-SB, -DB, and -RB), and ST1 (AB-SB, -DB, and -LB) (P < .05 in each comparison).

CONCLUSIONS

The 5 different FBUPs constituted different groups, reflecting different pathophysi-ologies.