Efficacy of different dry eye treatments with artificial tears or ocular lubricants: a systematic review

Post-refractive Surgery Dry Eye: A Systematic Review Exploring Pathophysiology, Risk Factors, and Novel Management Strategies

Dry eye disease frequently manifests following corneal refractive procedures, significantly impacting patients' quality of life. This review systematically synthesizes current evidence on the pathophysiological mechanisms, risk factors, and therapeutic interventions for post-refractive surgery dry eye. Following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines, a systematic review of literature published until August 2023 was conducted, focusing on post-refractive surgery dry eye. Eighteen relevant studies were identified through screening and eligibility assessment. A qualitative synthesis of outcomes was performed using narrative and thematic analysis methods. Surgically induced neurotrophic deficiency, stemming from nerve transection, triggers a cascade of events including apoptosis, inflammation, and lacrimal dysfunction, ultimately leading to tear film instability. Risk factors such as female gender, thyroid eye disease, meibomian gland dysfunction, higher ablation depths, and the use of LASIK over surface ablation exacerbate the condition. While conventional treatments like artificial tears provide temporary relief, emerging interventions such as nerve growth factors, matrix metalloproteinase inhibitors, serum eye drops, and specialized contact lenses show promise in promoting nerve regeneration and epithelial healing. Strategies such as customized ablation profiles, smaller optical zones, and nerve-sparing techniques like small incision lenticule extraction demonstrate potential advantages. A multifaceted therapeutic approach targeting neuroprotection, anti-inflammatory mechanisms, and tear film stabilization is imperative for effectively managing post-refractive surgery dry eye. Future research should focus on evaluating prognostic biomarkers, exploring precision medicine approaches, and investigating neuroprotective adjuvants to further enhance treatment outcomes.

Solving STODS-Surgical Temporary Ocular Discomfort Syndrome

The term STODS (Surgical Temporary Ocular Discomfort Syndrome) has been coined to describe the ocular surface perturbations induced by surgery. As one of the most important refractive elements of the eye, Guided Ocular Surface and Lid Disease (GOLD) optimization is fundamental to success in achieving refractive outcomes and mitigating STODS. Effective GOLD optimization and the prevention/treatment of STODS requires an understanding of the molecular, cellular, and anatomic factors that influence ocular surface microenvironment and the associated perturbations induced by surgical intervention. By reviewing the current understanding of STODS etiologies, we will attempt to outline a rationale for a tailored GOLD optimization depending on the ocular surgical insult. With a bench-to-bedside approach, we will highlight clinical examples of effective GOLD perioperative optimization that can mitigate STODS' deleterious effect on preoperative imaging and postoperative healing.

Recent advances in ocular graft-versus-host disease

Ocular graft-versus-host-disease (GVHD) remains a significant clinical complication after allogeneic hematopoietic stem cell transplantation. Impaired visual function, pain, and other symptoms severely affect affected individuals' quality of life. However, the diagnosis of and therapy for ocular GVHD involve a multidisciplinary approach and remain challenging for both hematologists and ophthalmologists, as there are no unified international criteria. Through an exploration of the complex pathogenesis of ocular GVHD, this review comprehensively summarizes the pathogenic mechanism, related tear biomarkers, and clinical characteristics of this disease. Novel therapies based on the mechanisms are also discussed to provide insights into the ocular GVHD treatment.

Hyaluronic acid in the treatment of dry eye disease

Dry eye disease (DED) is a highly prevalent and debilitating condition affecting several hundred million people worldwide. Hyaluronic acid (HA) is a naturally occurring glycosaminoglycan commonly used in the treatment of DED. This review aims to critically evaluate the literature on the safety and efficacy of artificial tears containing HA used in DED treatment. Literature searches were conducted in PubMed, including MEDLINE, and in Embase via Ovid with the search term: "(hyaluronic acid OR hyaluronan OR hyaluronate) AND (dry eye OR sicca)". A total of 53 clinical trials are included in this review, including eight placebo-controlled trials. Hyaluronic acid concentrations ranged from 0.1% to 0.4%. Studies lasted up to 3 months. A broad spectrum of DED types and severities was represented in the reviewed literature. No major complications or adverse events were reported. Artificial tears containing 0.1% to 0.4% HA were effective at improving both signs and symptoms of DED. Two major gaps in the literature have been identified: 1. no study investigated the ideal drop frequency for HA-containing eyedrops, and 2. insufficient evidence was presented to recommend any specific HA formulation over another. Future investigations assessing the optimal drop frequency for different concentrations and molecular weights of HA, different drop formulations, including tonicity, and accounting for DED severity and aetiology are essential for an evidence-based, individualized approach to DED treatment.

Short-term Efficacy and Safety of Biological Tear Substitutes and Topical Secretagogues for Dry Eye Disease: A Systematic Review and Network Meta-analysis

PURPOSE

The purpose of this study was to assess short-term efficacy and safety of tear promotion eye drops (biological tear substitutes and topical secretagogues) for treating dry eye disease.

METHODS

Randomized controlled trials comparing short-term effects of biological tear substitutes or topical secretagogues versus placebo or other topical dry eye treatments in adults with dry eye disease were identified from the MEDLINE, Embase, Scopus, ClinicalTrials.gov , and World Health Organization International Clinical Trials Registry Platform databases. Pairwise meta-analysis and network meta-analysis were performed. Outcomes were ocular symptoms, ocular surface staining, tear break-up time, Schirmer test, and adverse events. The certainty of evidence was evaluated using the Grading of Recommendations, Assessment, Development, and Evaluations approach.

RESULTS

Thirty-nine randomized controlled trials (3693 patients) were eligible. Using artificial tears as a reference, autologous platelet lysate was the most effective treatment for lowering ocular surface disease index (unstandardized mean difference [USMD] -31.85; 95% confidence interval [CI]: -43.19 to -20.51) and platelet rich plasma showed the most reduction in corneal fluorescein staining scores (standardized mean difference -2.52; 95% CI: -3.23 to -1.82). Cord blood serum was the most effective treatment for increasing tear break-up time (USMD 2.67; 95% CI: 0.53-4.82), and eledoisin was superior to others in improving Schirmer scores (USMD 2.28; 95% CI: 0.14-4.42). Most interventions did not significantly increase ocular adverse events compared with artificial tears.

CONCLUSIONS

Biological tear substitutes, including autologous serum, autologous platelet lysate, platelet rich plasma, and cord blood serum, might be the most effective treatment among tear promotion eye drops in relieving dry eye symptoms without increasing adverse events. However, there remains uncertainty around these findings because of low/very low certainty of evidence.

Artificial Tears: Biological Role of Their Ingredients in the Management of Dry Eye Disease

Dry eye disease (DED) is the most common ocular surface disease, characterized by insufficient production and/or instability of the tear film. Tear substitutes are usually the first line of treatment for patients with DED. Despite the large variety of tear substitutes available on the market, few studies have been performed to compare their performance. There is a need to better understand the specific mechanical and pharmacological roles of each ingredient composing the different formulations. In this review, we describe the main categories of ingredients composing tear substitutes (e.g., viscosity-enhancing agents, electrolytes, osmo-protectants, antioxidants, lipids, surfactants and preservatives) as well as their effects on the ocular surface, and we provide insight into how certain components of tear substitutes may promote corneal wound healing, and/or counteract inflammation. Based on these considerations, we propose an approach to select the most appropriate tear substitute formulations according to the predominant etiological causes of DED.

Analysis of urgent follow up visits and complications after intravitreal injections: a retrospective cohort study

BACKGROUND

Intravitreal injections (IVIs), a common treatment in ophthalmology, result in acute complications and urgent follow-up visits causing significant burden to both patient and physician. We evaluated the incidence of acute complications following IVIs which occurred within seven days of injection.

METHODS

A retrospective cohort study conducted at a private retinal practice, in Cleveland, Ohio. Using the practice management software database, we examined 73,286 injections of patients with unscheduled or urgent visits within 7 days of an injection from August 1st,2018 to August 1st,2020. Data collected included: age, gender, eye, medication injected, diagnosis, reason for urgent follow-up, time between injection and urgent follow-up, and type of anesthesia administered. Data was analyzed using SPSS v.28 (SPSS Inc., Chicago IL).

RESULTS

Study included 73,286 injections, with 441 injections (n = 441) resulting in urgent follow-up visits (0.60%). Mean patient age was 72.1 (± 30.4) years, with 187 male (42.4%) and 254 female (57.6%) patients. IVI medications included: aflibercept (60.3%), ranibizumab (22.4%), bevacizumab (13.4%), dexamethasone intravitreal implant (2%), triamcinolone acetonide (1.6%) brolucizumab (1.59%), fluocinolone acetonide intravitreal implant 0.19 mg (0.2%), and fluocinolone acetonide intravitreal implant 0.18 mg (0.03%) (Table 1). Medications associated with urgent visits included: aflibercept (42.9%), bevacizumab (37.4%), ranibizumab (7.9%), dexamethasone intravitreal implant (6.8%), brolucizumab (2.7%), and triamcinolone acetonide (2.3%) (Table 2). Days between injection and urgent follow-up was on average 3.96 ± 2.14 days. Urgent follow-ups included blurred vision in 164 patients (37.2% of urgent visits), flashes, floaters or posterior vitreous detachment (PVD) in 55 (12.5%), pain in 42 (9.5%), 43 (9.8%) corneal abrasions, 33 (7.5%) subconjunctival hemorrhages, corneal dryness or foreign body sensation in 30 (6.6%), endophthalmitis in 20 (4.5%), 18 (4.1%)vitreous hemorrhages, iritis or uveitis in 11 (2.5%), miscellaneous complications in 9 (2.0%), 7 (1.6%) elevated intraocular pressures, choroidal neovascular membrane in 4 (0.9%), 4 (0.9%) retinal detachments or tears, and 2 (0.45%) traumatic cataracts (Table 3).

CONCLUSION

IVIs resulted in 0.60% urgent/unscheduled follow-up visits within 7 days of injection. Most common causes were blurred vision and symptoms of PVD.

Effects of Eye Drops Containing Hyaluronic Acid-Nimesulide Conjugates in a Benzalkonium Chloride-Induced Experimental Dry Eye Rabbit Model

Dry eye syndrome (DES) is a common ocular disease worldwide. Currently, anti-inflammatory agents and immunosuppressive drugs, such as cyclosporine A, have been widely used to treat this chronic condition. However, the multifactorial etiology of DES, poor tolerance, low bioavailability, and prolonged treatment to response time have limited their usage. In this study, nimesulide, a cyclooxygenase (COX)-2 selective inhibitor, was conjugated with hyaluronic acid (HA), and the HA-nimesulide conjugates were expected to increase the solubility and biocompatibility for alleviating the DES in the benzalkonium chloride (BAC)-induced goblet cell-loss dry eye model. The therapeutic efficacy of HA-nimesulide was assessed using fluorescein staining, goblet cell density by conjunctival impression cytology, and histology and immunohistochemistry of corneal tissues. Compared to commercial artificial tears and Restasis®, the HA-nimesulide conjugates could promote goblet cell recovery and enhance the regeneration of the corneal epithelium. Importantly, immunofluorescent staining studies demonstrated that the HA-nimesulide conjugates could decrease the number of infiltrating CD11b-positive cells after two weeks of topical application. In the anti-inflammatory test, the HA-nimesulide conjugates could inhibit the production of pro-inflammatory cytokines and prostaglandin E2 (PGE2) in the lipopolysaccharide (LPS)-stimulated Raw 264.7 cell model. In conclusion, we demonstrated that HA-nimesulide conjugates had anti-inflammatory activity, and promoted goblet cell recovery and corneal epithelium regeneration when used as topical eye drops; accordingly, the HA-nimesulide conjugates could potentially be effective for the treatment of DES.

Lipid artificial tears at a mimetic ocular interface

We studied the behaviour of three lipid tear products, commercialised by the same brand, as Langmuir films at the air/liquid interface to simulate the ocular environment. No significant differences were observed in the surface behaviour of two of them disclosing the same composition, but commercialised for different applications. The interaction of several subphases, namely sodium chloride, glucose, albumin and lysozyme present in the natural tear, with the lipid films was assessed at room temperature and the temperature of human tear using surface pressure-area isotherms and elastic modulus plots. There is a notable influence of sodium chloride and the proteins albumin and lysozyme on the surface pressure-area isotherm of the lipid Langmuir films. Albumin shifted this isotherm to lower areas while an opposite shift was caused by lysozyme. These studies could be useful for the formulation of new lipid-containing artificial tears, and for increasing the confidence of the customers in commercial eye care formulations.

Involvement of ocular surface in graft-versus-host disease: An update from immunopathogenesis to treatment

Graft-versus-host disease is a common complication of hematopoietic stem cell transplantation and the ocular surface is a main target of inflammatory reaction.

Investigating the Synergistic Interactions of Surface Immobilized and Free Natural Ocular Lubricants for Contact Lens Applications: A Comparative Study between Hyaluronic Acid and Proteoglycan 4 (Lubricin)

The main reasons for the discontinuation of contact lens wear are ocular dryness and discomfort. Proteoglycan 4 (PRG4), a mucinous glycoprotein, and hyaluronic acid (HA), a nonsulfated linear glycosaminoglycan, are naturally present in the eye and contribute to ocular hydration and lubrication. This study aimed to investigate the impact of the structure of the recombinant human PRG4 (rhPRG4)/HA complex on contact lens properties, when one agent is grafted and the counterpart is physisorbed on the surface of model conventional or silicone contact lens materials. Investigation of the wettability, water retention, antifouling, and boundary lubricant properties of the prepared hydrogels showed that the rhPRG4/HA interactions varied with the rhPRG/HA configuration on the hydrogel surface as well as the composition of the underlying substrate used. The rhPRG4-physisorbed/HA-grafted sample was characterized by better antifouling and boundary lubricant properties on the model conventional hydrogels, while the HA-physisorbed/rhPRG4-grafted sample exhibited improved surface wettability, antifouling, and water-retentive properties on the model silicone hydrogels. The results of this study contribute to the design of biomimetic contact lens surfaces that work synergistically with ocular fluid-phase biological agents to enhance compatibility between the contact lens and the ocular environment, alleviating dry eye symptoms and improving comfort.

High-Frequency Application of Cationic Agents Containing Lubricant Eye Drops Causes Cumulative Corneal Toxicity in an Ex Vivo Eye Irritation Test Model

Purpose: High-frequency applied cetalkonium chloride (CAC) and benzalkonium chloride (BAC) 0.02% did not hamper corneal healing in a living rabbit model of induced corneal erosion. In contrast, the ex vivo eye irritation test (EVEIT) shows inhibition of healing for these substances. In a systematic ex vivo reproduction of the in vivo experiments, we discuss the background of these differences. Methods: Excised rabbit corneas (n = 5 per group) were cultured in artificial anterior chambers (EVEIT). Four erosions were induced for each cornea before starting regular 21 installations/day over 3 days of (1) CAC containing eye drops (Cationorm^®), (2) 0.02% BAC. Corneal fluorescein staining, quantification of glucose-/lactate consumption, and histology were performed. Results: BAC 0.02% treated corneas showed increased epithelial lesions from 10.13 ± 0.65 mm² to 10 ± 0.8 mm² on day 0, to 86.82 ± 5.18 mm² (P < 0.0001) by day 3. After a trend toward smaller lesions for CAC on day 1, erosion sizes increased significantly by day 3 from 9.82 ± 0.30 mm² to 29.51 ± 16.87 mm² (P < 0.05). For 1 cornea, corneal erosions nearly disappeared on day 3 (0.89 mm²). Corneal lactate increased significantly for BAC and CAC, whereas glucose concentrations were unchanged. Histology revealed disintegration of the corneal structures for both compounds. Conclusions: The data underline the EVEIT as a predictive toxicity test to show side effects in a time-compressed manner. The consistency of these predictions was previously demonstrated by the EVEIT for BAC, phosphate buffer, and others. The EVEIT is suited for a chronic application prediction of tolerability and toxic side effects of eye drops in particular, and other chemicals in general.

Dry eye in rheumatoid arthritis patients under TNF-inhibitors: conjunctival goblet cell as an early ocular biomarker

Dry eye disease (DED) is common in Rheumatoid Arthritis (RA) patients. The application of conjunctival goblet cell count as a clinical biomarker to diagnose and respond to treatment can take place in rheumatoid arthritis patients under TNF-inhibitors (TNFi) therapy. This study aimed to investigate the ocular surface parameters and the long-term effects of TNFi therapy on ocular surface features and goblet cell count of rheumatoid arthritis patients. At baseline, rheumatoid arthritis patients eligible to TNFi were compared to healthy controls (similar age/gender), regarding Ocular Surface Disease Index (OSDI) questionnaire, Schirmer I test, tear break-up time test, vital dye staining of the ocular surface, and conjunctival impression cytology. DED severity grade, impression cytology score, and goblet cell count were analyzed. Rheumatoid arthritis patients were followed after three (3 M) and 12 months (12 M), during TNFi treatment. Sixteen rheumatoid arthritis patients and 24 controls were compared: a higher frequency of abnormal OSDI (68.8% vs. 16.7%, p = 0.002), Schirmer's test < 10 mm (37.5% vs. 8.3%, p = 0.042), meibomian gland dysfunction (50% vs. 8.3%, p = 0.007), abnormal impression cytology (75% vs. 8.3%, p < 0.001), and mild to moderate DED (81.3% vs. 4.2%, p < 0.001) were observed in rheumatoid arthritis patients, who also had lower goblet cell count [325 (274-707) cells/mm² vs. 742 (562-863) cells/mm², p = 0.004]. The presence of Meibomian gland dysfunction was associated with higher disease activity scores (p < 0.05). The prospective early observation of these patients at 3 M showed an increase improvement in tear production by Schirmer's test [13 (7.5-17.5) vs. 23.5 (16-35); p = 0.001], and an improvement in impression cytology score [1 (0.5-2) vs. 1 (0-1), p = 0.031] and in goblet cell count [325 (274-707) vs. 931 (656-1,244), p < 0.001]. Eight RA responders to TNFi were also re-evaluated at 12 M with further improvement in goblet cell count [393 (275-827) vs. 872 (502-1,185) vs. 1,079 (867-1,244), p = 0.047]. Multifactorial DED is frequent in RA patients, comprising aqueous, lipid, and mucin components. TNFi prompt improves tear production and recovers the goblet cells, which can be a biomarker of the pathological process and response to therapy in this population.

Reliability of the Evidence Addressing Treatment of Corneal Diseases: A Summary of Systematic Reviews

Importance

Patient care should be informed by clinical practice guidelines, which in turn should be informed by evidence from reliable systematic reviews. The American Academy of Ophthalmology is updating its Preferred Practice Patterns (PPPs) for the management of the following 6 corneal diseases: bacterial keratitis, blepharitis, conjunctivitis, corneal ectasia, corneal edema and opacification, and dry eye syndrome.

Objective

To summarize the reliability of the existing systematic reviews addressing interventions for corneal diseases.

Data Source

The Cochrane Eyes and Vision US Satellite database.

Study Selection

In this study of published systematic reviews from 1997 to 2017 (median, 2014), the Cochrane Eyes and Vision US Satellite database was searched for systematic reviews evaluating interventions for the management of any corneal disease, combining eyes and vision keywords and controlled vocabulary terms with a validated search filter.

Data Extraction and Synthesis

The study classified systematic reviews as reliable when each of the following 5 criteria were met: the systematic review specified eligibility criteria for inclusion of studies, conducted a comprehensive literature search for studies, assessed risk of bias of the individual included studies, used appropriate methods for quantitative syntheses (meta-analysis) (only assessed if meta-analysis was performed), and had conclusions that were supported by the results of the systematic review. They were classified as unreliable if at least 1 criterion was not met.

Main Outcomes and Measures

The proportion of systematic reviews that were reliable and the reasons for unreliability.

Results

This study identified 98 systematic reviews that addressed interventions for 15 corneal diseases. Thirty-three of 98 systematic reviews (34%) were classified as unreliable. The most frequent reasons for unreliability were that the systematic review did not conduct a comprehensive literature search for studies (22 of 33 [67%]), did not assess risk of bias of the individual included studies (13 of 33 [39%]), and did not use appropriate methods for quantitative syntheses (meta-analysis) (12 of 17 systematic reviews that conducted a quantitative synthesis [71%]). Sixty-five of 98 systematic reviews (66%) were classified as reliable. Forty-two of the 65 reliable systematic reviews (65%) addressed corneal diseases relevant to the 2018 American Academy of Ophthalmology PPPs; 33 of these 42 systematic reviews (79%) are cited in the 2018 PPPs.

Conclusions and Relevance

One in 3 systematic reviews addressing interventions for corneal diseases are unreliable and thus were not used to inform PPP recommendations. Careful adherence by systematic reviewers and journal editors to well-established best practices regarding systematic review conduct and reporting might help make future systematic reviews in eyes and vision more reliable.

Refractory recurrent ocular graft versus host disease

Ocular graft-versus-host disease (GVHD) is one of the most frequent and long-term complications affecting patients after haematopoietic stem cell transplantation. It is associated with significant morbidity and a marked reduction in quality of life. Although common, currently there are no widely accepted guidelines available for its management, and no suggested regime of treatment that is completely satisfactory. So far, prophylactic treatment strategies for ocular GVHD have yet to be developed and treatment is normally initiated based on symptoms often after permanent ocular tissue changes and surface damage has occurred. Here we describe a case of recurrent ocular GVHD and its associated complications that was highly refractory to treatment.

Fabrication and characterization of cobalt hyaluronic acid nanostructure via gamma irradiation for improving biomedical applications

Aqueous dispersed cobalt hyaluronic acid nanostructure (CoHANs) was synthesized using cobalt ion (Co⁺²) as precursor and natural polysaccharide hyaluronic acid (HA) as stabilizing agent and gamma irradiation as reducing agent. The synthesized CoHANs are characterized by UV-Vis. spectroscopy, Dynamic light scattering (DLS), X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FT-IR). The morphology and surface appearance of CoHANs has been observed by SEM images. The particles size and shape of CoHANs were estimated by TEM images and was found to be 12.0 nm. XRD analysis of the CoHANs confirmed the formation of crystalline nanoparticles. The nucleation and growth mechanism of CoHANs was also discussed. The size of nanoparticles was found to be influenced by certain parameters such as the choice of stabilizer and cobalt ion concentration and the absorbed dose. The results indicated the CoHANs possesses high activity than cobalt ion and HA. The present study explored the positive role of CoHANs as an antitumor agent on different cell carcinoma in vitro. Excellent bactericidal spatially against pathogenic bacteria and fungicidal activity was shown by the CoHANs.

Ocular surface system alterations in ocular graft-versus-host disease: all the pieces of the complex puzzle

PURPOSE

Graft-versus-host disease (GVHD) is a major complication of allogeneic hematopoietic stem cells transplantation, occurring in about half of transplanted patients. This condition seems to be the result of a progressive immune-mediated damage that can involve various tissues, including the eyes. The ocular surface system is the ocular structure most frequently impaired, and dry eye disease is considered the hallmark of ocular GVHD. Given the increasing prevalence and the frequent severe involvement of the ocular surface with vision-threatening complications, ocular GVHD represents a current diagnostic and therapeutic challenge. The purpose of this literature review is to describe all the clinical manifestations occurring in the setting of ocular GVHD, and to further report the outcomes of conventional and novel therapies.

METHODS

A literature search about ocular GVHD was performed in PubMed, Scopus, Medline databases, and ClinicalTrials.gov as well as through the reference lists of identified publications until January 2019. We have included RCTs, prospective observational studies, prospective and retrospective cohort studies, pilot studies, and review articles.

RESULTS

Overall, 107 articles, 3 book chapters, and 6 ongoing registered clinical trials were collected and analyzed. Ocular GVHD can affect all the structures of the entire ocular surface system, including lacrimal and meibomian glands, cornea, conjunctiva, eyelids, nasolacrimal duct, and tears. Current medical treatment is mainly focused on lubrication and control of drainage, tear evaporation, and ocular surface inflammation. Surgical treatment may be necessary in severe, recalcitrant, or complicated cases. Amniotic membrane and tectonic keratoplasty can be valid options to restore the integrity of the cornea. Recently, conjunctival and limbal transplantation from the same living-related bone marrow donor has been proposed to manage both dry eye and limbal stem cell deficiency, without any risk of immunologic rejection.

CONCLUSION

This review provides an up-to-date analysis on clinical findings and current and future management of ocular GVHD. A correct and prompt diagnosis along with an appropriate and aggressive treatment are fundamental for avoiding the occurrence of vision-threatening complications.

A Bioelectronic Platform Modulates pH in Biologically Relevant Conditions

Bioelectronic devices that modulate pH can affect critical biological processes including enzymatic activity, oxidative phosphorylation, and neuronal excitability. A major challenge in controlling pH is the high buffering capacity of many biological media. To overcome this challenge, devices need to be able to store and deliver a large number of protons on demand. Here, a bioelectronic modulator that controls pH using palladium nanoparticles contacts with high surface area as a proton storage medium is developed. Reversible electronically triggered acidosis (low pH) and alkalosis (high pH) in physiologically relevant buffer conditions are achieved. As a proof of principle, this new platform is used to control the degradation and fluorescence of acid sensitive polymeric microparticles loaded with a pH sensitive fluorescent dye.

Surface modification of model hydrogel contact lenses with hyaluronic acid via thiol-ene "click" chemistry for enhancing surface characteristics

Discontinuation of contact lens wear as a result of ocular dryness and discomfort is extremely common; as many as 26% of contact lens wearers discontinue use within the first year. While patients are generally satisfied with conventional hydrogel lenses, improving on-eye comfort continues to remain a goal. Surface modification with a biomimetic, ocular friendly hydrophilic layer of a wetting agent is hypothesized to improve the interfacial interactions of the contact lens with the ocular surface. In this work, the synthesis and characterization of poly(2-hydroxyethyl methacrylate) surfaces grafted with a hydrophilic layer of hyaluronic acid are described. The immobilization reaction involved the covalent attachment of thiolated hyaluronic acid (20 kDa) on acrylated poly(2-hydroxyethyl methacrylate) via nucleophile-initiated Michael addition thiol-ene "click" chemistry. The surface chemistry of the modified surfaces was analyzed by Fourier transform infrared spectroscopy-attenuated total reflectance and X-ray photoelectron spectroscopy. The appearance of N (1s) and S (2p) peaks on the low resolution X-ray photoelectron spectroscopy spectra confirmed successful immobilization of hyaluronic acid. Grafting hyaluronic acid to the poly(2-hydroxyethyl methacrylate) surfaces decreased the contact angle, the dehydration rate, and the amount of nonspecific sorption of lysozyme and albumin in comparison to pristine hydrogel materials, suggesting the development of more wettable surfaces with improved water-retentive and antifouling properties, while maintaining optical transparency (>92%). In vitro testing also showed excellent viability of human corneal epithelial cells with the hyaluronic acid-grafted poly(2-hydroxyethyl methacrylate) surfaces. Hence, surface modification with hyaluronic acid via thiol-ene "click" chemistry could be useful in improving contact lens surface properties, potentially alleviating symptoms of contact lens related dryness and discomfort during wear.

Safety and Tolerability of Overdosed Artificial Tears by Abraded Rabbit Corneas

Purpose: Preservative-free cationic emulsion-based artificial tear (AT) is an innovative eye drop based on the Novasorb^® technology with cetalkonium chloride (CKC) as the cationic agent. The cationic emulsion Cationorm is designed for the management of mild-to-moderate dry eye disease (DED) patients that present cornea epithelium alterations. The aim of the present study was to evaluate the safety and tolerability of overdosed ATs by altered corneal epithelium in vivo and assess the usefulness of the ex vivo eye irritation test (EVEIT) as a predictive alternate toxicity test method.

Methods: The experimental procedure, treatment duration, and instillation frequency closely mimic in vivo the ex vivo protocol described by Pinheiro et al. and discussed in the Discussion and Conclusion section of this article. Two to 3-month-old female New Zealand white rabbits, n = 6 per group, were treated with ATs (21 instillations/day over 3 days) following corneal abrasion. Corneal fluorescein staining, in vivo confocal microscopy (IVCM), and slit lamp examinations were performed to assess corneal epithelium recovery and the ocular tolerability of the overdosed ATs.

Results: All abraded eyes experienced almost complete epithelium recovery within 3 days following treatments with Cationorm, Optive, Vismed, and Saline. Benzalkonium chloride (BAK, 0.02%) treatment resulted in 82.4% reepithelialization. IVCM data illustrated corneal epithelium normal recovery. Acute local tolerability of the overdosed ATs was confirmed using Draize and McDonald–Shadduck's test scales.

Conclusions: The different ATs were demonstrated to be well tolerated by abraded corneas in vivo, and the extreme overdosing regimen did not hamper the wound healing process of the rabbit eye in comparison to saline. These data did not confirm the ones obtained with the nonvalidated ex vivo eye irritation test.

Dry eye disease: when to treat and when to refer

Dry eye disease affects one in five adults and can significantly impair quality of life Most patients have mild disease

This condition is multifactorial with an inflammatory component which can markedly worsen the impact on the ocular surface Meibomian gland dysfunction is extremely common in dry eye disease and contributes to the inflammatory process

Management of mild disease includes identifying and removing precipitants and symptomatic treatment with artificial tear supplements

More advanced disease requires management of underlying ophthalmic and systemic conditions as well as more aggressive therapies to protect the ocular surface

Active agents, biomaterials, and technologies to improve biolubrication and strengthen soft tissues

Normal functioning of articulating tissues is required for many physiological processes occurring across length scales from the molecular to whole organism. Lubricating biopolymers are present natively on tissue surfaces at various sites of biological articulation, including eyelid, mouth, and synovial joints. The range of operating conditions at these disparate interfaces yields a variety of tribological mechanisms through which compressive and shear forces are dissipated to protect tissues from material wear and fatigue. This review focuses on recent advances in active agents and biomaterials for therapeutic augmentation of friction, lubrication, and wear in disease and injured states. Various small-molecule, biological, and gene delivery therapies are described, as are tribosupplementation with naturally-occurring and synthetic biolubricants and polymer reinforcements. While reintroduction of a diseased tissue's native lubricant received significant attention in the past, recent discoveries and pre-clinical research are capitalizing on concurrent advances in the molecular sciences and bioengineering fields, with an understanding of the underlying tissue structure and physiology, to afford a desired, and potentially patient-specific, tissue mechanical response for restoration of normal function. Small and large molecule drugs targeting recently elucidated pathways as well as synthetic and hybrid natural/synthetic biomaterials for restoring a desired tissue mechanical response are being investigated for treatment of, for example, keratoconjunctivitis sicca, xeroderma, and osteoarthritis.

Development of In Vitro Methodologies to Investigate Binding by Sodium Hyaluronate in Eye Drops to Corneal Surfaces

PURPOSE

To develop in vitro methods to assess binding by sodium hyaluronate in eye drops to corneal surfaces.

METHODS

Two different, complementary corneal binding set-ups were developed. In a dynamic in vitro model, confluent corneal epithelial cells (HCE-T) were assembled in chamber slides and a declining channel. A static model was constructed with ex vivo porcine corneas clamped in Franz cells. To test the predictive capacity of models, four different eye drops containing sodium hyaluronate were spiked with tritium-labeled sodium hyaluronate to standardize quantification. In both settings, eye drops were applied for 5 min and physiological conditions were mimicked by flushing with artificial tear fluid. Spreading experiments on HCE-T next to synthetic membranes were used for further characterization.

RESULTS

Binding was more pronounced in dynamic HCE-T model. Three of the four eye drops demonstrated sigmoidal elution of sodium hyaluronate, suggesting pronounced binding. One solution eluted distinctly faster, likewise the buffer control. The static method produced a similar ranking but at lower levels. When eye drops in which phosphate buffer was replaced by citrate buffer (i.e., to prevent calcification) were used, binding was not influenced. All eye drops spread immediately when placed on HCE-T and at the same order of magnitude on glass and polyethylene terephthalate surfaces.

CONCLUSION

Dynamic and static models performed on different corneal sources were used to determine sodium hyaluronate binding kinetics in solutions under physiological conditions. These methodologies resulted in a ranking of the capacity of sodium hyaluronate to bind in vitro to corneal surfaces.

Evaluation of artificial tears on cornea epithelium healing

AIM

To observe the efficacy of different artificial eye drops on corneal epithelium healing in rabbit.

METHODS

Thirty-five rabbits with 6 mm diameter central corneal epithelium removed were randomly assigned to six groups: 0.9% normal saline (NS) group, 0.1% hyaluronate (HA) group, 0.3% HA group, Tears Naturale Free^® (TNF) group, 0.4% polyethylene glycol (PEG) group, 0.5% carboxymethyl cellulose (CMC) group and blank control group. Treatments were administered topically four times daily. Corneal epithelium healing was evaluated by the percentage reduction in wound area at 24, 36, 48, 60, and 72h after removal of the corneal epithelium. Cornea re-epithelialization was also assessed by histological analysis and electron microscopy.

RESULTS

All corneal wounds completely re-epithelialized in less than 72h. The average re-epithelialization time was 47.61±4.25h in the 0.3% HA group and 49.72±1.05h in the 0.9% NS group, followed by 0.1% HA, TNF, 0.4% PEG, 0.5% CMC, and lastly by the control group. Compared to the control group, there were significant differences among 0.3% HA, 0.9% NS, PEG, and TNF (P<0.05) groups. At the first 24h, re-epithelialization at the 0.3% HA, TNF, and 0.9% NS treatment groups were significantly faster than the other groups. At 48h post-wounding, corneal epithelium is nearly completing re-epithelialization at 0.3% HA and 0.9% NS treatment groups. Electron microscopy revealed that there were a large number of vacuoles in the cells of the 0.9% NS group at 72h.

CONCLUSION

Artificial tears promote corneal re-epithelium varied in the efficacy. Obviously, all artificial eye drops better than blank group. In the process of corneal healing, corneal epithelium cells suffered from hypoxia caused by NS.

Ocular surface lubricants

PURPOSE OF REVIEW

The purpose of this article is to provide an overview of the ocular lubricants currently available, consider the components of the various formulations and highlight the status of preservative use in the treatment of anterior ocular surface diseases.

RECENT FINDINGS

The primary components of ocular surface lubrication have been, in the past, based on various cellulose formulations that increase hydration. Advances in lubrication have come from areas of the human body requiring lubrication such as the skeletal joints as well as examining the use of natural components of the tear fluid. These have resulted in novel modifications of existing tear components, for example, thiolated carboxymethyl hyaluronic acid which creates crosslinking to mechanically increase retention time for ocular surface hydration. Other proteoglycans such as lubricin, having one of the lowest coefficients of friction in nature, to a lipopolysaccharide derivative of tamarind seed, may provide a unique delivery system for lubricants and medications.

SUMMARY

The present state of ocular surface lubrication is slowly advancing from the routine use of cellulose-based solutions and gels to more advanced replacement with natural tear components. The advances that are occurring on other lubricating surfaces of the musculoskeletal system are also providing some insights into potential use on the ocular surface.

Effects of molecular weight of hyaluronic acid on its viscosity and enzymatic activities of lysozyme and peroxidase

OBJECTIVES

To investigate the effects of the molecular weight of hyaluronic acid on its viscosity and enzymatic activities of lysozyme and peroxidase in solution and on the hydroxyapatite surface.

DESIGN

Hyaluronic acids of four different molecular weights (10 kDa, 100 kDa, 1 MDa, and 2 MDa), hen egg-white lysozyme, bovine lactoperoxidase, and human whole saliva were used. Viscosity values of hyaluronic acids were measured using a cone-and-plate viscometer at six different concentrations (0.1-5.0 mg/mL). Enzymatic activities of lysozyme and peroxidase were examined by hydrolysis of fluorescein-labeled Micrococcus lysodeikticus and oxidation of fluorogenic 2',7'-dichlorofluorescein to fluorescing 2',7'-dichlorofluorescein, respectively.

RESULTS

In solution assays, only 2 MDa-hyaluronic acid significantly inhibited lysozyme activities in saliva. In surface assays, hyaluronic acids inhibited lysozyme and peroxidase activities; the inhibitory activities were more apparent with high-molecular-weight ones in saliva than in purified enzymes. The 100 kDa-hyaluronic acid at 5.0 mg/mL, 1 MDa-one at 0.5 mg/mL, and 2 MDa-one at 0.2 mg/mL showed viscosity values similar to those of human whole saliva at a shear rate range required for normal oral functions. The differences among the influences of the three conditions on the enzymatic activities were not statistically significant.

CONCLUSIONS

High-molecular-weight hyaluronic acids at low concentration and low-molecular-weight ones at high concentration showed viscosity values similar to those of human whole saliva. Inhibitory effects of hyaluronic acids on lysozyme and peroxidase activities were more significant with high-molecular-weight ones on the surface and in saliva compared with in solution and on purified enzymes.

A review of late complications of allogeneic hematopoietic stem cell transplantations

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an effective and curative treatment of different malignant and non-malignant diseases. Early transplant-related mortality after allo-HSCT has decreased with reduced-intensity conditioning regimens and effective anti-infectious treatments, but late transplant-related mortality is still a problem. Physicians are now paying more attention to late complications that may worsen the quality of life of many transplant recipients. Chronic graft versus host disease (cGVHD) is one of the major causes of late transplant-related mortality after allo-HSCT. This review discusses recent advances that have been made in clinical evaluation and treatment of late transplant-related complications including cGVHD. The different sites of involvement are organs, especially the skin and eye, and the gastrointestinal, endocrinologic, metabolic, renal, cardiologic, pulmonary, connective tissue, and neurological systems. In addition, this review includes infections and secondary malignancies in post-transplant settings that worsen quality of life in long-term follow-ups.

An Ilomastat-CD Eye Drop Formulation to Treat Ocular Scarring

Purpose

The purpose of this study was to develop a topical matrix metalloproteinase inhibitor preparation for antiscarring therapy.

Methods

The broad spectrum matrix metalloproteinase inhibitor ilomastat was formulated using 2-hydroxypropyl-β-cyclodextrin in aqueous solution. In vitro activity of ilomastat-cyclodextrin (ilomastat-CD) was examined using fibroblasts seeded in collagen. Permeation of ilomastat-CD eye drop through pig eye conjunctiva was confirmed using Franz diffusion cells. Ilomastat-CD eye drop was applied to rabbit eyes in vivo, and the distribution of ilomastat in ocular tissues and fluids was determined by liquid chromatography-mass spectroscopy.

Results

The aqueous solubility of ilomastat-CD was ∼1000 μg/mL in water and 1400 μg/mL in PBS (pH 7.4), which is greater than ilomastat alone (140 and 160 μg/mL in water and PBS, respectively). The in vitro activity of ilomastat-CD to inhibit collagen contraction in the presence of human Tenon fibroblast cells was unchanged compared to uncomplexed ilomastat. Topically administered ilomastat-CD in vivo to rabbit eyes resulted in a therapeutic concentration of ilomastat being present in the sclera and conjunctiva and within the aqueous humor.

Conclusions

Ilomastat-CD has the potential to be formulated as an eye drop for use as an antifibrotic, which may have implications for the prevention of scarring in many settings, for example glaucoma filtration surgery.

Efficacy and Safety of 0.2% Hyaluronic Acid in the Management of Dry Eye Disease

OBJECTIVES

To evaluate the safety and efficacy of a new artificial tear containing 0.2% hyaluronic acid, as compared with 0.9% saline solution, in mild dry eye patients after 1-month use in a crossover study design with washout periods.

METHODS

Overall, 16 mild dry eye patients were included. After a week of washout, every patient used the experimental product (Visaid 0.2%) and the control product (0.9% saline solution), each for a month (3-8 drops daily). Both products were preservative free. The percentage change for the following variables were calculated and analyzed: Ocular Surface Disease Index (OSDI) questionnaire, visual acuity, intraocular pressure, ophthalmoscopy evaluation, biomicroscopy findings, fluorescein corneal staining and lissamine green conjunctival staining, tear breakup time, contrast sensitivity, Schirmer's test, and subject satisfaction.

RESULTS

Patients reported an improvement (a significant decrease of -19.5%±27.5%) in OSDI scores after using Visaid 0.2% and a worsening (a significant increase of 19.2%±32.4%) after using 0.9% saline solution; the difference was significant (P=0.0087, Student's t test). Significant changes (P≤0.04, Wilcoxon's test) were found comparing Visaid 0.2% with saline solution for bulbar hyperemia (-39.1%±50.8% vs. 7.8%±12.0%, respectively), corneal staining (-26.0%±53.0% vs. 36.5%±73.3%), conjunctival staining (-54.7%±53.4% vs. -7.8%±47.2%), and subjective satisfaction (26.8%±28.5% vs. -13.3%±22.5%). There were no significant differences in the safety parameters for either solution.

CONCLUSION

This clinical trial demonstrates the safety of Visaid 0.2% and its clear benefit over 0.9% saline solution.

Assessment of ocular discomfort caused by 5 shampoos using the Slug Mucosal Irritation test

Assessment of ocular discomfort caused by veterinary care products is less legitimately regulated than that caused by human care products. The Slug Mucosal Irritation (SMI) assay was adapted to evaluate canine hygiene shampoos to predict ocular discomfort. Experiments were performed using four commercial canine shampoos, a baby care product, and two controls (ArtTear® and BAC1%). Groups of 3 slugs were tested with 5% dilution of the 7 test substances. The negative control (ArtTear®) was the best tolerated. The baby care product Mixa bébé as well as Douxo Entretien Démêlant and Phlox Shampooing Entretien were classified to cause mild ocular discomfort. Together with the positive control (BAC 1%), Shampooing Physiologique Virbac and Physiovet Shampooing were considered to cause severe ocular discomfort. Different intensities of ocular discomfort were measured for veterinary care products. The SMI model was considered as a reproducible and adaptable evaluation method for screening veterinary care products causing ocular discomfort.

Hyaluronan as a promising excipient for ocular drug delivery

Hyaluronan (HA) is a naturally occurring polysaccharide and well known for its exceptional properties such as high biocompatibility and biodegradability, along with a low immunogenicity. Besides its use for various biomedical applications it recently came into focus as a favorable excipient for the formulation of various ocular therapeutics. This review article summarizes the ocular distribution of HA and its most heavily investigated binding protein "cluster of differentiation 44" (CD44) which is the rationale for the clinical use of HA, primarily as an additive in ocular applications ranging from eye drops to contact lenses. Moreover, examples will be given for using HA in various pre-clinical approaches to generate entirely new therapeutics, most notably in the field of nanotechnology.

Immediate Effect of 3% Diquafosol Ophthalmic Solution on Tear MUC5AC Concentration and Corneal Wetting Ability in Normal and Experimental Keratoconjunctivitis Sicca Rat Models

PURPOSE

To evaluate the immediate effect of 3% diquafosol ophthalmic solution on tear MUC5AC concentration, periodic acid-Schiff (PAS)-positive goblet cells, and tear film stability in normal and keratoconjunctivitis sicca (KCS) rat models.

METHODS

Rats were divided into normal and KCS groups. 3% of diquafosol solution was instilled into the right eye and normal saline into the left eye in both groups. To determine the peak time of tear MUC5AC concentration, tears were collected after 3% diquafosol instillation every 5 min up to 20 min. The tear film stability and the numbers of PAS-positive goblet cells were compared in both models.

RESULTS

After diquafosol instillation, tear MUC5AC concentration increased steadily for 15 min, at which point the MUC5AC concentration reached its peak. In both normal and KCS groups, the MUC5AC concentration at 15 min was higher after instillation of 3% diquafosol solution (17.77 ± 2.09 ng/ml in the normal group, 9.65 ± 3.51 ng/ml in the KCS group) than that after saline instillation (13.74 ± 2.87 ng/ml in the normal group, 8.19 ± 3.99 ng/ml in the KCS group) (p = 0.018 for both). The corneal wetting ability was significantly longer after instillation of 3% diquafosol solution compared with that after instillation of normal saline in the normal group (p = 0.018). The percentage of PAS-positive goblet cells after the instillation of 3% diquafosol solution was significantly lower than that after instillation of normal saline in both models (p = 0.018 for both).

CONCLUSIONS

Diquafosol ophthalmic solution was effective in stimulating mucin secretion in both normal and KCS rat models, and the peak time of tear MUC5AC concentration was 15 min after diquafosol instillation. The increased tear MUC5AC concentration was accompanied by improved tear film stability and a decreased percentage of PAS-positive goblet cells.

Long-term safety and efficacy of autologous platelet lysate drops for treatment of ocular GvHD

Current ocular GvHD (oGvHD) treatments are suboptimal. We investigated the safety and efficacy of long-term continuous treatment with autologous platelet lysate (PL) drops in patients with oGvHD Dry Eye Syndrome (DES) score 2-3 refractory to topical conventional therapy. Ophthalmic evaluation was performed at 6 month intervals. Symptoms were assessed using the Glaucoma Symptom Scale (GSS). Patients were defined 'responders' when showing a reduction at least one grade on National Institutes of Health Eye Score from baseline at the 6 month visit. Thirty-one patients were included, and 16 (51%) completed 36 months of follow-up (range 6.5-72.7). At 6 months all patients were classified as responders: median GSS symptom score decreased from 70 to 41 (33 at 36 months), median GSS function score reduced from 68 to 46 (33 at 36 months) (all P<0.001). Median Tear Break Up Time improved from 3 to 6 s after 6 months and was maintained over time. All signs improved at 6 and 36 months (clinical and statistical significance). No severe adverse events occurred. Long-term treatment with PL drops is secure and effective for oGvHD and can be an efficient therapy option from initial stages of oGvHD to prevent permanent ocular impairment and improving quality of life.

Synergistic Effect of Artificial Tears Containing Epigallocatechin Gallate and Hyaluronic Acid for the Treatment of Rabbits with Dry Eye Syndrome

Dry eye syndrome (DES) is a common eye disease. Artificial tears (AT) are used to treat DES, but they are not effective. In this study, we assessed the anti-inflammatory effect of AT containing epigallocatechin gallate (EGCG) and hyaluronic acid (HA) on DES. Human corneal epithelial cells (HCECs) were used in the WST-8 assay to determine the safe dose of EGCG. Lipopolysaccharide-stimulated HCECs showing inflammation were treated with EGCG/HA. The expression of IL-1ß, IL-6, IL-8, and TNF-α was assessed by real-time PCR and AT physical properties such as the viscosity, osmolarity, and pH were examined. AT containing EGCG and HA were topically administered in a rabbit DES model established by treatment with 0.1% benzalkonium chloride (BAC). Tear secretion was assessed and fluorescein, H&E, and TUNEL staining were performed. Inflammatory cytokine levels in the corneas were also examined. The non-toxic optimal concentration of EGCG used for the treatment of HCECs in vitro was 10 μg/mL. The expression of several inflammatory genes, including IL-1ß, IL-6, IL-8, and TNF-α, was significantly inhibited in inflamed HCECs treated with 10 μg/mL EGCG and 0.1% (w/v) HA (E10/HA) compared to that in inflamed HCECs treated with either EGCG or HA alone. AT containing E10/HA mimic human tears, with similar osmolarity and viscosity and a neutral pH. Fluorescence examination of the ocular surface of mouse eyes showed that HA increased drug retention on the ocular surface. Topical treatment of DES rabbits with AT plus E10/HA increased tear secretion, reduced corneal epithelial damage, and maintained the epithelial layers and stromal structure. Moreover, the corneas of the E10/HA-treated rabbits showed fewer apoptotic cells, lower inflammation, and decreased IL-6, IL-8, and TNF-α levels. In conclusion, we showed that AT plus E10/HA had anti-inflammatory and mucoadhesive properties when used as topical eye drops and were effective for treating DES in rabbits.

Comparison of the Anti-Inflammatory Effects of Artificial Tears in a Rat Model of Corneal Scraping

PURPOSE

Artificial tears (ATs) are used routinely to alleviate the symptoms of mild to moderate dry eye. Preservative-free cationic emulsions (eg, Cationorm(®)) are an innovative approach for the management of signs and symptoms of dry eye. The aim of the present exploratory experiment was to evaluate the efficacy of this cetalkonium chloride (CKC)-containing cationic emulsion on debrided cornea and to characterize its effects on scraping-induced inflammation.

METHODS

Four ATs were assessed in a rat model of corneal scraping. The upper part of the corneal epithelium was scraped before a 5-day treatment, followed by clinical evaluations and fluorescein staining to evaluate cornea recovery. The anti-inflammatory efficacy of the ATs was assessed in vivo and in vitro.

RESULTS

In vivo confocal microscopy (IVCM) revealed a trend toward better corneal clinical signs (lower IVCM scores) for the animals treated with the unpreserved ATs. Benzalkonium chloride treatment decreased goblet cell count by 37.5%. While the soft-preserved Systane Balance(®) and Optive(®) and the preservative-free Vismed(®) had no effect on the goblet cell count, Cationorm increased this count by almost 40%. Interestingly, inflammatory cell infiltration in the stroma was at its lowest following treatment with the preservative-free Cationorm. Cationorm is also the only AT decreasing IL6- and IL8-stimulated secretion by 59% and 74%, respectively.

CONCLUSION

By restoring an adequately hydrated ocular surface environment, the different ATs promote corneal epithelium healing. These data position Cationorm as a promising AT for the management of signs and symptoms of dry eye in patients with mild to moderate dry eye disease presenting chronic subclinical levels of ocular inflammation.

Over the counter (OTC) artificial tear drops for dry eye syndrome

BACKGROUND

Over the counter (OTC) artificial tears historically have been the first line of treatment for dry eye syndrome and dry eye-related conditions like contact lens discomfort, yet currently we know little regarding the overall efficacy of individual, commercially available artificial tears. This review provides a much needed meta-analytical look at all randomized and quasi-randomized clinical trials that have analyzed head-to-head comparisons of OTC artificial tears.

OBJECTIVES

To evaluate the effectiveness and toxicity of OTC artificial tear applications in the treatment of dry eye syndrome compared with another class of OTC artificial tears, no treatment, or placebo.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register) (2015, Issue 12), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to December 2015), EMBASE (January 1980 to December 2015), Latin American and Caribbean Health Sciences (LILACS) (January 1982 to December 2015), the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov), the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en) and the US Food and Drugs Administration (FDA) website (www.fda.gov). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 4 December 2015. We searched reference lists of included trials for any additional trials not identified by the electronic searches.

SELECTION CRITERIA

This review includes randomized controlled trials with adult participants who were diagnosed with dry eye, regardless of race and gender. We included trials in which the age of participants was not reported, and clinical trials comparing OTC artificial tears with another class of OTC artificial tears, placebo, or no treatment. This review did not consider head-to-head comparisons of artificial tears with another type of dry-eye therapy.

DATA COLLECTION AND ANALYSIS

We followed the standard methodological procedures expected by Cochrane. Two authors independently screened the search results, reviewed full-text copies for eligibility, examined risk of bias, and extracted data. We performed meta-analysis for trials that compared similar interventions and reported comparable outcomes with sufficient data. We summarized all other included trial results in the text.

MAIN RESULTS

We included 43 randomized controlled trials (3497 participants with dry eye). Due to the heterogeneity of study characteristics among the included trials with respect to types of diagnostic criteria, interventions, comparisons, and measurements taken, our ability to perform meta-analyses was limited. The review found that, in general, there was uncertainty whether different OTC artificial tears provide similar relief of signs and symptoms when compared with each other or placebo. Nevertheless, we found that 0.2% polyacrylic acid-based artificial tears were consistently more effective at treating dry eye symptoms than 1.4% polyvinyl alcohol-based artificial tears in two trials assessing this comparison (175 participants). All other included artificial tears produced contradictory between-group results or found no between-group differences. Our review also found that OTC artificial tears may be generally safe, but not without adverse events. Overall, we assessed the quality of evidence as low due to high risks of bias among included trials and poor reporting of outcome measures which were insufficient for quantitative analysis. Furthermore, we identified an additional 18 potentially eligible trials that were reported only in clinical trial registers with no associated results or publications. These trials reportedly enrolled 2079 total participants for whom no data are available. Such lack of reporting of trial results represents a high risk of publication bias.

AUTHORS' CONCLUSIONS

OTC artificial tears may be safe and effective means for treating dry eye syndrome; the literature indicates that the majority of OTC artificial tears may have similar efficacies. This conclusion could be greatly skewed by the inconsistencies in study designs and inconsistencies in reporting trial results. Additional research is therefore needed before we can draw robust conclusions about the effectiveness of individual OTC artificial tear formulations.

Evaluation of a Novel Artificial Tear in the Prevention and Treatment of Dry Eye in an Animal Model

Purpose: To evaluate effects of a novel multi-ingredient artificial tear formulation containing carboxymethylcellulose (CMC) and hyaluronic acid (HA) in a murine dry eye model.

Methods: Dry eye was induced in mice (C57BL/6) using an intelligently controlled environmental system (ICES). CMC+HA (Optive Fusion™), CMC-only (Refresh Tears^®), and HA-only (Hycosan^®) artificial tears and control phosphate-buffered saline (PBS) were administered 4 times daily and compared with no treatment (n = 64 eyes per group). During regimen 1 (prevention regimen), mice were administered artificial tears or PBS for 14 days (starting day 0) while they were exposed to ICES, and assessed on days 0 and 14. During regimen 2 (treatment regimen), mice exposed to ICES for 14 days with no intervention were administered artificial tears or PBS for 14 days (starting day 14) while continuing exposure to ICES, and assessed on days 0, 14, and 28. Corneal fluorescein staining and conjunctival goblet cell density were measured.

Results: Artificial tear-treated mice had significantly better outcomes than control groups on corneal staining and goblet cell density (P < 0.01). Mice administered CMC+HA also showed significantly lower corneal fluorescein staining and higher goblet cell density, compared with CMC (P < 0.01) and HA (P < 0.05) in both regimens 1 and 2.

Conclusions: The artificial tear formulation containing CMC and HA was effective in preventing and treating environmentally induced dry eye. Improvements observed for corneal fluorescein staining and conjunctival goblet cell retention suggest that this combination may be a viable treatment option for dry eye disease.

Effect of hyaluronic acid on tear film thickness as assessed with ultra-high resolution optical coherence tomography

PURPOSE

The aim of this study was to assess the effect of a single drop of hyaluronic acid on tear film thickness (TFT) in healthy subjects.

METHODS

Sixteen healthy subjects (eight male/eight female) aged between 20 and 36 years were included in this randomized, double-masked placebo-controlled study. One eye received a single dose of hyaluronic acid (Olixia pure(®) ; Croma Pharma, Korneuburg, Austria) eye drops, and the fellow eye received physiologic saline solution as placebo control. The study eye was chosen randomly. TFT as measured with a custom-built Fourier-domain optical coherence tomography (FD-OCT) system was the main outcome variable and measured before and every 10 min until 1 hr after topical administration.

RESULTS

Baseline TFT was 4.8 ± 0.5 μm in the study eye and 5.0 ± 0.4 μm in the control eyes. Hyaluronic acid significantly increased TFT (p = 0.008 versus placebo) with a maximum effect 10 min after instillation (13.9 ± 11.9%). Post hoc analysis revealed that an increase in TFT was seen until 30 min after administration compared to placebo. Data in the placebo group show high reproducibility with an intraclass correlation coefficient of 0.93 and a coefficient of variation of 5.4 ± 3.3%.

CONCLUSION

The data of this study indicate that hyaluronic acid increases TFT for as long as 30 min in healthy subjects. In addition, our data provide evidence that our custom-built OCT system is capable of measuring residence time of lubricants on the ocular surface.