Cross-Linked Hyaluronic Acid as Tear Film Substitute

Recommendations for nutritional supplements for dry eye disease: current advances

Dry eye disease (DED) represents a prevalent ocular surface disease. The development of effective nutritional management strategies for DED is crucial due to its association with various factors such as inflammation, oxidative stress, deficiencies in polyunsaturated fatty acids (PUFAs), imbalanced PUFA ratios, and vitamin insufficiencies. Extensive research has explored the impact of oral nutritional supplements, varying in composition and dosage, on the symptoms of DED. The main components of these supplements include fish oils (Omega-3 fatty acids), vitamins, trace elements, and phytochemical extracts. Beyond these well-known nutrients, it is necessary to explore whether novel nutrients might contribute to more effective DED management. This review provides a comprehensive update on the therapeutic potential of nutrients and presents new perspectives for combination supplements in DED treatment.

Dry Eye Disease in the Middle East and Northern Africa: A Position Paper on the Current State and Unmet Needs

In the Middle East and Northern Africa (MENA), dry eye disease (DED) is often misdiagnosed or overlooked. This review summarizes a series of conversations with ophthalmologists in the region around a variety of climatic, lifestyle, and iatrogenic factors that contribute to specific features of DED in the MENA region. These considerations are further classified by patient lifestyle and surgical choices. All statements are based on discussions and formal voting to achieve consensus over three meetings. Overall, a deeper understanding of the disease characteristics of DED specific to MENA can better guide local eyecare practitioners on appropriate management and follow-up care. Additionally, population-based studies and patient and physician education on ocular surface diseases, together with the use of culturally appropriate and language-specific questionnaires can help ease the public health burden of DED in this region.

A comparison between hyaluronic acid and other single ingredient eye drops for dry eye, a review

Dry eye disease (DED) is a highly prevalent and debilitating condition. Hyaluronic acid (HA) is a naturally occurring glycosaminoglycan that has a long history as a safe and effective DED treatment. HA is frequently used as a comparator when assessing other topical DED treatments. This study aims to summarise and critically evaluate the literature describing all isolated active ingredients that have been directly compared with HA in the treatment of DED. A literature search was conducted in Embase using Ovid on the 24th of August 2021 and in PubMed including MEDLINE on the 20th of September 2021. Twenty-three studies met the inclusion criteria, 21 of which were randomised controlled trials. Seventeen different ingredients representing six treatment categories were compared with HA treatment. Most measures showed no significant difference between treatments, suggesting either equivalency of treatments or that studies were underpowered. Only two ingredients were represented in more than two studies; carboxymethyl cellulose treatment appears equivalent to HA treatment, while Diquafosol treatment appears superior to HA treatment. Drop-frequency varied from one to eight drops daily. No single study explained the choice of drop frequency. Nine studies used a HA concentration of 0.1% which may be below therapeutic levels. Nine studies reported using preserved formulations, six of them with differences in preservatives between the compared groups. Thirteen studies were financially linked to industry. No major complications were reported. Studies were not designed to find differences in treatment effects for different types or severities of DED. HA is a good comparator treatment when assessing other DED treatments, although consensus after decades of use is still lacking for best choice of concentration, molecular weight and drop tonicity. Well-designed studies are needed to determine an evidence-based standard for HA treatment to be used as comparator.

Safe and Effective Management of Dry Eye Symptoms with Hydroxypropyl Guar and Hyaluronic Acid Dual-Polymer Lubricating Eye Drops: A Review of Preclinical and Clinical Studies

Dry eye disease (DED) is a chronic ocular surface disorder often characterized by decreased tear production and rapid tear evaporation that affect tear film stability and homeostasis. The common symptoms of DED include ocular discomfort, visual disturbances, dryness, and itching. Artificial tears are the mainstay of DED management and supplement one or more layers of the tear film. Artificial tear drops are available as a combination of viscosity-enhancing agents (demulcents/lubricants), humectants, and buffers either with or without preservatives. Artificial tears, as a combination of components (polymers/demulcents/viscosity-enhancing agents), can provide synergistic action compared with a single component for the management of multifactorial signs and symptoms of DED. This review describes the formulation components, physicochemical properties, mechanism of action, and summary of preclinical and clinical evidence on the hydroxypropyl guar-hyaluronic acid (HPG-HA) dual-polymer lubricant eye drops (SYSTANE™ HYDRATION). The dual-polymer eye drops consist of dual demulcents (propylene glycol and polyethylene glycol 400) and the polymers hydroxypropyl guar (HPG) and hyaluronic acid (HA). When instilled on the ocular surface, HPG forms a cross-linked gel matrix with borate ions that prolongs the retention of demulcents, thus providing long-lasting lubrication and ocular surface protection. Additionally, HA stabilizes the tear film, increases corneal wettability, and reduces friction during blinks due to its hygroscopic and viscoelastic properties. Preclinical evidence demonstrates that HPG HA dual-polymer lubricant eye drops provide protection against desiccation by cell hydration and surface retention, cell barrier protection, prolonged lubrication, and promotion of corneal re-epithelialization. Clinical scientific evidence demonstrates that HPG HA dual-polymer lubricant eye drops are safe and effective in the management of DED. Specifically, they reduce the signs and symptoms of DED, reduce dry eye symptoms post-cataract surgery, and improve tear film quality in healthy eyes.

Recent Advances in Hydrogels for the Diagnosis and Treatment of Dry Eye Disease

Dry eye disease (DED) is the most common clinical ocular surface disease. Given its multifactorial etiology, no consensus has been reached on the diagnosis criteria for dry eye disease. Topical drug administration remains the mainstay of treatment but is limited to the rapid clearance from the eye surface. To address these problems, hydrogel-based materials were designed to detect biomarkers or act as drug delivery systems by taking advantage of their good biocompatibility, excellent physical and mechanical properties, and long-term implant stability. Biosensors prepared using biocompatible hydrogels can be sensitive in diagnosing DED, and the designed hydrogels can also improve the drug bioavailability and retention time for more effective and long-term treatment. This review summarizes recent advances in the use of hydrogels for diagnosing and treating dry eye, aiming to provide a novel reference for the eventual clinical translation of hydrogels in the context of dry eye disease.

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.

Clinical Efficacy, Tolerability and Safety of a New Multiple-Action Eyedrop in Subjects with Moderate to Severe Dry Eye

Background: To assess the clinical efficacy, tolerability and safety of a new-generation ophthalmic solution containing cross-linked hyaluronic acid 0.15% trehalose 3%, liposomes 1% and sterylamine 0.25% (Trimix® Off Health Italia, Firenze, Italy) (CXHAL) versus trehalose 3% (Thealoz®, Thea Pharmaceuticals, Clermont-Ferrand, France) (TRS) in subjects with moderate to severe dry eye disease (DED). Patients and methods: In this prospective, observational cohort study, 41 subjects with moderate to severe dry eye were enrolled and divided into two age- and sex-matched groups. Group 1 was treated with CXHA eye drops, and group 2 was treated with TRS eye drops four times daily for 2 months. All subjects were evaluated at baseline (V0) and at day 60 ± 3 (V1). The examination comprised Best Corrected Visual Acuity (BCVA) and Symptom Assessment in Dry Eye (SANDE). Tear osmolarity was evaluated using the TearLab Osmolarity System®; Keratograph 5M (Oculus, Wetzlar, Germany) was performed to assess tear meniscus height (TMH), fluorescein tear break-up time (TBUT) and corneal and conjunctival fluorescein staining and meibography; furthermore, slit lamp evaluation was performed for eyelid erythema and edema, conjunctival chemosis and hyperemia and Meibomian gland secretion quality. Results: All patients completed the treatment. BCVA remained stable in both groups, and no adverse events were reported. After 2 months, both groups showed statistically significant improvements for SANDE (p = 0.001 and p = 0.012, respectively), TBUT values (p < 0.001 and p < 0.001, respectively) and staining (p = 0.004 and p = 0.001, respectively) as compared to baseline values. Group 1 showed a statistically significant improvement in SANDE frequency and tear osmolarity (p = 0.02 and p = 0.001, respectively), whereas chemosis was significantly reduced in group 2. The amount of TBUT improvement was statistically higher in group 1 compared to that in group 2 (p = 0.041). Conclusion: A new-generation multiple-action ophthalmic solution was safe and clinically effective in the treatment of moderate and severe dry eye, with significant improvements in the main ocular surface parameters.

Cysteamine Eye Drops in Hyaluronic Acid Packaged in Innovative Single-Dose Systems: Stability and Ocular Biopermanence

Cystinosis is a rare genetic disorder characterized by the accumulation of cystine crystals in different tissues and organs causing, among other symptoms, severe ocular manifestations. Cysteamine eye drops are prepared in hospital pharmacy departments to facilitate access to treatment, for which vehicles that provide adequate biopermanence, as well as adaptable containers that maintain its stability, are required. Difficulties related to cysteamine preparation, as well as its tendency to oxidize to cystamine, show the importance of conducting rigorous galenic characterization studies. This work aims to develop and characterize an ophthalmic compounded formulation of cysteamine prepared with hyaluronic acid and packaged in innovative single-dose systems. For this task, the effect of different storage temperatures and the presence/absence of nitrogen on the physicochemical stability of the formulation and its packaging was studied in a scaled manner, until reaching the optimal storage conditions. The results showed that 0.55% cysteamine, prepared with hyaluronic acid and packaged in single-dose containers, is stable for 30 days when stored at −20 °C. In addition, opening vials every 4 h at room temperature after 30 days of freezing maintains the stability of the cysteamine formulation for up to 16 h. Moreover, ocular biopermanence studies were conducted using molecular imaging, concluding that the biopermanence offered by the vehicle is not affected by the freezing process, where a half-life of 31.11 min for a hyaluronic acid formulation stored for 30 days at −20 °C was obtained, compared with 14.63 min for 0.9% sodium chloride eye drops.

Hyaluronic acid hydrogels crosslinked via blue light-induced thiol-ene reaction for the treatment of rat corneal alkali burn

To assess corneal inflammation from alkali chemical burns, we examined the therapeutic effects of in situ-forming hyaluronic acid (HA) hydrogels crosslinked via blue light-induced thiol-ene reaction on a rat corneal alkali burn model. Animals were divided into three groups (n = 7 rats per group): untreated, treated with 0.1% HA eye drops, and treated with crosslinked HA hydrogels. Crosslinking of HA hydrogel followed by the administration of HA eye drops and crosslinked HA hydrogels were carried out once a day from days 0–4. Corneal re-epithelialization, opacity, neovascularization, thickness, and histology were evaluated to compare the therapeutic effects of the three groups. Further investigation was conducted on the transparency of HA hydrogels to acquire the practical capabilities of hydrogel as a reservoir for drug delivery. Compared to untreated animals, animals treated with crosslinked HA hydrogels exhibited greater corneal re-epithelialization on days 1, 2, 4, and 7 post-injury (p = 0.004, p = 0.007, p = 0.008, and p = 0.034, respectively) and the least corneal neovascularization (p = 0.008). Histological analysis revealed lower infiltration of stromal inflammatory cells and compact collagen structure in crosslinked HA hydrogel-treated animals than in untreated animals. These findings corresponded with immunohistochemical analyses indicating that the expression of inflammatory markers such as α-SMA, MMP9, and IL1-β was lower in animals treated with crosslinked HA hydrogels than untreated animals and animals treated only with 0.1% HA eye drops. With beneficial pharmacological effects such as re-epithelization and anti-inflammation, in situ-forming hyaluronic acid (HA) hydrogels may be a promising approach to effective drug delivery in cases of corneal burn injuries.

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Corneal chemical injuries can induce corneal opacification, limbal ischemia, and loss of vision.

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Limitations for using topical eye drops includes maintaining the optimal concentration of the drug on the ocular surface.

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Crosslinked HA hydrogels achieved rapid corneal re-epithelialization and low-grade neovascularization after chemical injury.

Management Strategies for Evaporative Dry Eye Disease and Future Perspective

Dry eye disease (DED) is a common disorder that remains challenging from a clinical perspective. Unstable or deficient tear film is a major factor contributing to DED and the inability to resolve the loss of tear film homeostasis that accompanies DED can result in a vicious circle of inflammation and treatment-refractory disease. Recently recognized as a multifactorial disease, the main etiological subtypes of DED are aqueous-deficient and evaporative which exist on a continuum, although evaporative dry eye (EDE) is the more frequent classification. Although attaining greater recognition in recent years, there is currently no consensus and no clear recommendation on how to manage EDE. Clarity on the early diagnosis and treatment of EDE may facilitate the avoidance of progression to chronic inflammation, permanent damage to the ocular surface, and treatment-refractory disease. The purpose of this review was to identify current best practice for management of EDE in order to help clinicians in providing accurate diagnosis and optimized treatment. We summarize recent literature considering the role of the lipid layer on tear film stability, the importance of its composition and of its dynamic behavior, and the link between its malfunction and the insurgence and maintenance of tear film-related diseases. We have provided an assessment of the best management of lipid-deficient EDE based upon an understanding of disease pathophysiology, while indicating the flow of current treatments and possible future evolution of treatment approaches. Lipid containing eye drops may be considered as a step closer to natural tears from artificial aqueous tears because they more closely mimic the aqueous and lipid layers and may be used in combination with other management approaches. As a next step, we recommend working with a wider expert group to develop full guidelines to enable patient-centered management of EDE. Key pointsDry eye is a multifactorial disease of variable presentation with the tendency to become a chronic disease for which it is essential to identify and treat the main pathogenic mechanisms involved and tailor the treatment to the individual patient.Early intervention is needed to prevent the vicious cycle of DED and may require a multi-faceted management approach.EDE is not just a problem of MGD but can be the result of anything affecting blinking, mucin spreading, aqueous layer volume and content.Lipid-containing eye drops may provide significant relief of symptoms by improving the lipid layer and its spreading ability and, as such, are an appropriate component of the overall management of lipid-deficient EDE; natural lipid-containing eye drops should be the preferred treatment.

Assessment of the Efficiency of HP-Guar and hyaluronic Acid Tear Supplements to Control Tear Film Evaporation Rate in Dry Eye Subjects

Background:

The most common factor that could lead to dryness is the accelerated tear evaporation rate. Controlling the tear evaporation rate is increasingly used as a method to control dry eye complications. The present study explores the effects of different tear supplements formulations on tear film evaporation rate.

Objective:

This study aimed to evaluate the short-term effects of Systane ULTRA and Artelac Advanced eye drops on the tear film evaporation rate.

Methods:

Fifteen male dry eye subjects were enrolled in the current study. Tear film parameters were observed at several time points post installation (10, 20, 30, and 60 min). The tear film parameters observed in the current study were tear evaporation rate, noninvasive breakup time (NITBUT) and tear meniscus height (TMH). Two visits were required to conduct this study. One visit was conducted to assess the physiological tear film parameters with the use of Systane® ULTRA eye drop. The other visit was conducted to assess tear film parameters with the use of Artelac Advanced eye drop.

Results:

The mean tear evaporation rate at baseline was 52.58 ± 23.24 g/m2 h. A box plot of tear evaporation showed a reduction in tear film evaporation rate after instillation of Systane eye drop. A drop in tear film evaporation rate of 14% was observed at 20 and 60 min time point after instillation of Systane ULTRA eye drop. A significant increase in NITBUT was found after instillation of Systane ULTRA (P = 0.01) and Artelac Advanced (P = 0.02).

Conclusion:

The current study indicates a significant improvement in the tear film parameters using both HP-Guar and hyaluronic acid formulations. However, it was apparent that the use of HP-Guar was superior to hyaluronic acid in controlling the tear evaporation rate in dry eye subjects.

Novel Formulation of Eye Drops Containing Choline Salicylate and Hyaluronic Acid: Stability, Permeability, and Cytotoxicity Studies Using Alternative Ex Vivo and In Vitro Models

This work investigated the potential of a novel formulation of eye drops containing a non-steroidal anti-inflammatory drug-choline salicylate (CS)-and hyaluronic acid (HA). Thus, these drops may exert both anti-inflammatory and regenerative activity. The experiment was conducted through the careful characterization of physicochemical properties, stability, and quality of eye drops. Moreover, microbiological analysis, as well as penetration and cytotoxic studies, were performed. The UV, HPLC-UV, and HPLC-MS/MS methods were used to determine the purity and stability of CS. The penetration rate of CS was assessed using a hydrophilic membrane and ex vivo porcine cornea model. Additionally, the cytotoxic effects were evaluated using the SIRC cell line. The interaction between HA and CS was tested using size-exclusion chromatography and IR spectrophotometry. As a result, HA increased the viscosity of the drops, which prolonged their contact with the ocular surface, thus ensuring more effective penetration of CS into the corneal structure. After long-term storage, an interaction in the pharmaceutical phase between CS and HA was observed. However, this interaction did not affect the viability of rabbit corneal cells. Our findings showed that eye drops with CS and HA, stored at 2-8 °C in light-protected conditions, met the criteria of stability and safety.

Applications of Hyaluronic Acid in Ophthalmology and Contact Lenses

Hyaluronic acid (HA) is a glycosaminoglycan that was first isolated and identified from the vitreous body of a bull’s eye. HA is ubiquitous in the soft connective tissues of animals and therefore has high tissue compatibility for use in medication. Because of HA’s biological safety and water retention properties, it has many ophthalmology-related applications, such as in intravitreal injection, dry eye treatment, and contact lenses. Due to its broad range of applications, the identification and quantification of HA is a critical topic. This review article discusses current methods for analyzing HA. Contact lenses have become a widely used medical device, with HA commonly used as an additive to their production material, surface coating, and multipurpose solution. HA molecules on contact lenses retain moisture and increase the wearer’s comfort. HA absorbed by contact lenses can also gradually release to the anterior segment of the eyes to treat dry eye. This review discusses applications of HA in ophthalmology.

Efficacy of 0.1% crosslinked hyaluronic acid, coenzyme Q10 and vitamin E in the management of dry eye disease in menopause patients receiving antidepressants

PURPOSE

The purpose of this study is to test non-inferiority of a lower dose of crosslinked hyaluronic acid (CLHA) to a higher dose of carmellose eye drop in menopause patients receiving antidepressant treatments.

METHODS

This prospective, double-blind, single-center study enrolled sixty female patients. Mean age was 63.25 ± 9.13 years. We examined patients with Schirmer I, breakup time (TBUT) and the ocular surface disease index (OSDI) at the first visit. Tear A eyedrops were formulated with crosslinked hyaluronic acid, coenzyme Q10 and vitamin E. Control tear B was formulated with carmellose sodium. Posology was two and five times, respectively.

RESULTS

After 2 months of treatment, the tear A obtained 14.12 ± 7.47 score points for OSDI (t = 11.74, p < 0.01), and tear B obtained 19.46 ± 10.03 score points (t = 7.59, p < 0.01). The tear A obtained 13.77 ± 7.78 score points for Schirmer test (t = 0.88, p > 0.05), and tear B obtained 14.20 ± 8.62 score points (t = 2.92, p < 0.01). The tear A obtained 8.30 ± 2.08 s for TBUT (t = 15.50, p < 0.01), and tear B obtained 7.23 ± 2.40 s (t = 8.79, p < 0.01).

CONCLUSION

Lower total daily dose of crosslinked hyaluronic acid eyedrops obtained similar efficacy results in terms of tear stability and subjective dry eye sensation than higher carmellose total daily dose. A lower total daily dose of crosslinked eyedrops was sufficient to achieve better dry eye disease management compared to carmellose.