Precorneal residence times of sodium hyaluronate solutions studied by quantitative gamma scintigraphy

Comparison of eye drop retention time using fluorophotometry in three commercially available lubricant eye drops

SIGNIFICANCE

This is the first study to evaluate the retention time of lubricating eye drops containing various concentrations of sodium hyaluronate using fluorophotometry in a symptomatic dry eye population. Information regarding eye drop retention may be useful for eye care practitioners to assist in the selection of more effective treatments for managing dry eye.

PURPOSE

This study aimed to use fluorophotometry to compare retention time on the ocular surface of three commercially available lubricating eye drops, each containing varying concentrations of sodium hyaluronic acid (HA), and their effects on tear film stability post-instillation in a population with symptoms of dry eye.

METHODS

Adults with symptoms of dry eye (Ocular Surface Disease Index score, >12) were enrolled in this prospective, double-masked comparison of eye drops containing 0.15% HA-hydroxypropyl guar (HPGuar), 0.2% HA, and 0.1% HA. Participants were randomized to the eye drop order and the study eye under evaluation. Each eye drop was admixed with a fluorescent tracer (70-kDa fluorescein isothiocyanate-dextran) at 10% wt/vol, and 10 μL volume was instilled for each evaluation. A fluorophotometer was used to measure the time for the tracer signal to return to baseline. Fluorescein tear breakup time was measured following fluorophotometry assessment.

RESULTS

Retention time for 0.15% HA-HPGuar and 0.2% HA was significantly longer compared with 0.1% HA (p=0.02 and p=0.03). Fluorescein tear breakup time was significantly longer for the 0.15% HA-HPGuar eye drop compared with both the 0.1% HA eye drop (p=0.01) and 0.2% HA eye drop (p=0.003).

CONCLUSIONS

Retention time on the ocular surface of the two eye drops containing higher concentrations of HA was longer than the eye drop with the lowest concentration of HA. The tear film was also more stable with the 0.15% HA-HPGuar eye drop compared with the eye drops containing HA alone, which may be attributable to the other components in the 0.15% HA-HPGuar eye drop.

A randomized controlled trial involving college student: Comparing 0.15% hyaluronic acid with 0.05% cyclosporine A and 3% diquafosol sodium in the Treatment of Dry Eye

BACKGROUND

To compare the efficacy of 0.15% hyaluronic acid (HA), 0.05% cyclosporine A (CsA) and 3% diquafosol sodium (DQS) ophthalmic solution for the treatment of moderate-to-severe dry eye disease (DED) in college students and the effect on inflammatory factors in tears.

METHODS

This was a prospective, randomized, multicenter trial. A total of 282 college students diagnosed with moderate-to-severe DED between October 2, 2022 and March 1, 2023 were included. A total of 282 patients were randomized to treatment in the group of 0.15% HA or 0.05% CsA or 3% DQS in a 1:1:1 assignment. There was a main end point which is the variations in the corneal staining score to determine non-inferiority of 0.15% HA. Secondary target end points were ocular surface disease index score, Schirmer test, tear meniscus height and tear film breakup time. In addition, the inflammatory factor levels of Interleukin-1β, Interleukin-6, transforming growth factor-β1 in tears were measured. Effectiveness was assessed at baseline, 4- and 12-weeks.

RESULTS

In our analysis, the average change from baseline in corneal staining score confirmed non-inferiority of 0.15% HA to 0.05% CsA and 3% DQS and manifested obvious improvement of all groups as well (P < .05). Values for ocular surface disease index score, Schirmer test, tear meniscus height and tear film breakup time showed obvious improvements in all groups (P < .05), however, the difference intergroup was not statistically significant. Value for inflammatory factor was significant improvement across all groups, although inflammatory factor scores in the 0.05% CsA group showed a clear trend of better improvement at 12 weeks compared with 0.15% HA groups (P < .01). No serious adverse reactions were observed.

CONCLUSIONS

College students taking 0.15% HA had clinically and statistically significant improvement in corneal staining score and other indicators, but it was inferior to 0.05% CsA in anti-inflammatory therapy for moderate to severe DED. However, 0.15% HA is still an effective, safe and well-tolerated treatment option that may offer additional benefits in terms of convenience and compliance.

Advancements in Nanogels for Enhanced Ocular Drug Delivery: Cutting-Edge Strategies to Overcome Eye Barriers

Nanomedicine in gel or particle formation holds considerable potential for enhancing passive and active targeting within ocular drug delivery systems. The complex barriers of the eye, exemplified by the intricate network of closely connected tissue structures, pose significant challenges for drug administration. Leveraging the capability of engineered nanomedicine offers a promising approach to enhance drug penetration, particularly through active targeting agents such as protein peptides and aptamers, which facilitate targeted release and heightened bioavailability. Simultaneously, DNA carriers have emerged as a cutting-edge class of active-targeting structures, connecting active targeting agents and illustrating their potential in ocular drug delivery applications. This review aims to consolidate recent findings regarding the optimization of various nanoparticles, i.e., hydrogel-based systems, incorporating both passive and active targeting agents for ocular drug delivery, thereby identifying novel mechanisms and strategies. Furthermore, the review delves into the potential application of DNA nanostructures, exploring their role in the development of targeted drug delivery approaches within the field of ocular therapy.

Precorneal retention time of ocular lubricants measured with fluorophotometry in healthy dogs

OBJECTIVE

Determine the precorneal retention time of five different ocular lubricants commonly used in dogs.

ANIMALS STUDIED

Six healthy Beagle dogs (n = 12 eyes).

PROCEDURES

Five ocular lubricants were studied: Artificial Tears Solution® (1.4% polyvinyl alcohol), I-Drop® Vet Plus (0.25% hyaluronate), Optixcare® Eye Lube Plus (0.25% hyaluronate), Systane® Ultra (0.4% polyethylene glycol 400 and 0.3% propylene glycol), and Artificial Tears Ointment® (mineral oil/white petrolatum). Each lubricant was mixed with 10% sodium fluorescein to achieve 1% fluorescein formulations. Following topical administration of 35 mg in each eye, tear fluid was collected with capillary tubes at selected times (0, 1, 5, 10, 20, 30, 40, 50, 60, 90, 120, 180 min) and fluorescein concentrations were measured with a computerized scanning ocular fluorophotometer.

RESULTS

Tear fluorescence was significantly greater with Artificial Tears Ointment® compared with other lubricant formulations from 1 to 20 min post-administration. Median (range) precorneal retention times were significantly different among the 5 lubricants, ranging from 40 minutes (20-90 min) for Artificial Tears Ointment®, 35 min (20-90 min) for Systane® Ultra, 30 min (10-60 min) for I-Drop® Vet Plus, 25 min (10-60 min) for Optixcare® Eye Lube Plus, and 10 min (10-20 min) for Artificial Tears Solution®. Precorneal retention time was significantly lower for Artificial Tears Solution® compared with the other 4 formulations.

CONCLUSIONS

This study established normative data for the retention time of common lubricants on the ocular surface of dogs, which may be used to guide clinicians with their choice of lubricant and frequency of administration.

Performance and Safety of a Sodium Hyaluronate Tear Substitute with Polyethylene Glycol in Dry Eye Disease: A Multicenter, Investigator-Masked, Randomized, Noninferiority Trial

Purpose: To compare the performance and safety of 2 tear substitutes containing sodium hyaluronate (SH); one containing 0.15% SH and polyethylene glycol (PEG) 8000, and the other containing 0.18% SH. Methods: In this multicenter, randomized, investigator-masked, noninferiority trial, 83 patients with moderate or severe dry eye disease underwent a 2-week washout, and were then randomly assigned (1:1) to receive SH plus PEG tear substitute (n = 45) or comparator SH tear substitute (n = 38) 3-6 times daily for 3 months. The primary performance endpoint was the change from baseline in the ocular surface fluorescein staining (OSFS) score on day 28 in the per-protocol (PP) population, according to the 15-point Oxford Scheme, with a noninferiority margin of 2. Results: Both groups improved significantly in terms of signs and symptoms. Among the 78 patients without major protocol deviations (the PP population), the OSFS score decreased by 2.9 ± 2.0 on day 28 from 5.4 ± 1.3 at baseline in the SH plus PEG group and by 2.3 ± 2.2 from 5.2 ± 1.4 in the comparator group (95% confidence interval of the difference: -1.2 to 0.3), demonstrating noninferiority. On day 90, the improvement in OSFS scores was significantly greater in the SH plus PEG group (P = 0.0002). The safety profiles were satisfactory in both groups. Conclusion: SH plus PEG tear substitute was noninferior to SH tear substitute in the studied population and may provide additional benefits in the long term. ClinicalTrials.gov ID: NCT02975102.

A bioinspired synthetic soft hydrogel for the treatment of dry eye

Natural soft hydrogels are unique elastic soft materials utilized by living organisms for protecting delicate tissues. Under a theoretical framework derived from the Blob model, we chemically crosslinked high molecular weight hyaluronic acid at a concentration close to its overlap concentration (c*), and created synthetic soft hydrogels that exhibited unique rheological properties similar to a natural soft hydrogel: being dominantly elastic under low shear stress while being viscous when the stress is above a small threshold. We explored a potential application of the hyaluronic acid-based soft hydrogel as a long-acting ocular surface lubricant and evaluated its therapeutic effects for dry eye. The soft hydrogel was found to be biocompatible after topical instillation on experimental animals' and companion dogs' eyes. In a canine clinical study, twice-a-day ocular instillation of the soft hydrogel in combination with cyclosporine for 1 month improved the clinical signs in more than 65% of dog patients previously unresponsive to cyclosporine treatment.

Strategies to prolong the residence time of drug delivery systems on ocular surface

Ocular diseases may be treated via different routes of administration, such as topical, intracameral, intravitreal, oral and parenteral. Among them the topical route is most accepted by patients, although it provides in many cases the lowest bioavailability. Indeed, when a topical formulation reaches the precorneal area, i.e., the drug absorption and/or action site, it is rapidly eliminated due to eye protection mechanisms such as blinking, basal and reflex tearing, and naso-lacrimal draining. To avoid this and to reduce the frequency of dosing, various strategies have been developed to prolong drug residence time after topical administration. These strategies include the use of viscosity increasing and mucoadhesive excipients as well as combinations thereof. From the drug delivery system point of view, liquid and semisolid formulations are preferred over solid formulations such as ocular inserts and contact lenses. Furthermore, liquid and semisolid formulations can contain nano- and microcarrier systems that contribute to a prolonged residence time. Within this review an overview about the different types of excipients and formulations as well as their performance in valid animal models and clinical trials is provided.

Biopharmaceutical Assessment of Dexamethasone Acetate-Based Hydrogels Combining Hydroxypropyl Cyclodextrins and Polysaccharides for Ocular Delivery

We previously developed two optimized formulations of dexamethasone acetate (DXMa) hydrogels by means of special cubic mixture designs for topical ocular administration. These gels were elaborated with hydroxypropyl-β-CD (HPβCD) and hydroxypropyl-γ-CD (HPγCD) and commercial hydrogels in order to enhance DXMa water solubility and finally DXMa's ocular bioavailability and transcorneal penetration. The main objective of this study was to characterize them and to evaluate in vitro, ex vivo, and in vivo their safety, biopermanence, and transcorneal permeation. Gels A and B are Newtonian fluids and display a viscosity of 13.2 mPa.s and 18.6 mPa.s, respectively, which increases their ocular retention, according to the in vivo biopermanence study by PET/CT. These hydrogels could act as corneal absorption promoters as they allow a higher transcorneal permeation of DXMa through porcine excised cornea, compared to DEXAFREE^® and MAXIDEX^®. Cytotoxicity assays showed no cytotoxic effects on human primary corneal epithelial cells (HCE). Furthermore, Gel B is clearly safe for the eye, but the effect of Gel A on the human eye cannot be predicted. Both gels were also stable 12 months at 25 °C after sterilization by filtration. These results demonstrate that the developed formulations present a high potential for the topical ocular administration of dexamethasone acetate.

Trehalose for Ocular Surface Health

Trehalose is a natural disaccharide synthesized in various life forms, but not found in vertebrates. An increasing body of evidence demonstrates exceptional bioprotective characteristics of trehalose. This review discusses the scientific findings on potential functions of trehalose in oxidative stress, protein clearance, and inflammation, with an emphasis on animal models and clinical trials in ophthalmology. The main objective is to help understand the beneficial effects of trehalose in clinical trials and practice, especially in patients suffering from ocular surface disease. The discussion is supplemented with an overview of patents for the use of trehalose in dry eye and with prospects for the 2020s.

Polysaccharides in Ocular Drug Delivery

Polysaccharides, such as cellulose, hyaluronic acid, alginic acid, and chitosan, as well as polysaccharide derivatives, have been successfully used to augment drug delivery in the treatment of ocular pathologies. The properties of polysaccharides can be extensively modified to optimize ocular drug formulations and to obtain biocompatible and biodegradable drugs with improved bioavailability and tailored pharmacological effects. This review discusses the available polysaccharide choices for overcoming the difficulties associated with ocular drug delivery, and it explores the reasons for the dependence between the physicochemical properties of polysaccharide-based drug carriers and their efficiency in different formulations and applications. Polysaccharides will continue to be of great interest to researchers endeavoring to develop ophthalmic drugs with improved effectiveness and safety.

Comparison study of two different topical lubricants on tear meniscus and tear osmolarity in dry eye

PURPOSE

To compare the effect of single-drop administration of two different ophthalmic solutions on tear meniscus and tear osmolarity in patients with mild to moderate dry eye disease.

METHODS

This prospective study comprised of 122 patients with mild to moderate dry eye disease. These patients received a single dose of either unpreserved trehalose 3%, hyaluronic acid 0.15%, carbomer 0.25% (THHA, Thealoz Duo Gel) (Group 1) or hyaluronic acid 0.3% (HA) (Group 2) gel-based lubricants. Tear meniscus (height and depth) were measured using anterior segment optic coherence tomography (AS-OCT) at baseline and 10, 60, 120, and 240 min. after instillation. Tear osmolarity, Schirmer I test, tear break-up time (TBUT), gel properties, and patient comfort were evaluated 240 min. after instillation.

RESULTS

Tear meniscus height (TMH) and tear meniscus depth (TMD) showed a significant increase with both lubricants compared to the baseline (p < 0.001). This effect remained significant for up to 60 min. and 120 min. for the THHA and HA 0.3% solutions, respectively (p < 0.05, for both). Mean comfort duration was 115.1 ± 20.1 min. in Group 1 and 148.3 ± 49.0 min in Group 2 (p < 0.001). Tear osmolarity, Schirmer I test, and TBUT were similar between the baseline and 240 min. for each group.

CONCLUSIONS

The results of this study demonstrate that 0.3% HA remains on the ocular surface for longer than TH-HA. The longer ocular residency time also seems to correlate with a longer patient comfort duration.

Drug-eluting contact lens containing cyclosporine-loaded cholesterol-hyaluronate micelles for dry eye syndrome

A cholesterol-hyaluronate (C-HA) micelle embedded contact lens was developed for efficient hydrophobic drug loading and long-term controlled drug delivery.

Stability, safety, and transcorneal mechanistic studies of ophthalmic lyophilized cyclosporine-loaded polymeric micelles

Introduction

Cyclosporine-A (CsA) is generally used as an immunosuppressant and is also prescribed for some ophthalmic applications such as vernal keratoconjunctivitis and dry eye. However, it is limited clinically due to its low aqueous solubility and ocular bioavailability.

Methods

In this work, lyophilized methoxy poly(ethylene glycol)-poly(lactide) (mPEG-PLA) polymer micelles were prepared for ophthalmic formulations as a promising nanocarrier for hydrophobic drugs like CsA. A mPEG-PLA diblock polymer was synthesized by ring opening polymerization and CsA was loaded into mPEG-PLA micelles by a simple film dispersion method. A uniform design of experiments was utilized to optimize the final formulation. The obtained formulation was characterized for diameter (57.0±3.2 nm), entrapment efficiency % (98.51±1.4), and in vitro release. Moreover, incorporating the stabilizer mPEG2000 could increase the in vitro stability of the lyophilized CsA-loaded mPEG-PLA micelles.

Results

Results showed a sustained release of CsA from the micelles. Drug concentration and time-dependent cytotoxicity of human corneal epithelial-2 cells was observed. Additionally, the transcorneal mechanism of mPEG-PLA micelles was studied and the results showed that the mPEG-PLA micelles mainly absorbed by a paracellular pathway via corneal epithelial cells.

Conclusion

Taken together, the results proved that this mPEG-PLA diblock polymer can be potentially used as a nanoscopic carrier to deliver hydrophobic drugs in a controlled manner to the ocular region and, thus, deserves further attention.

In Vitro Evaluation of Hybrid Cooperative Complexes of Hyaluronic Acid as a Potential New Ophthalmic Treatment

PURPOSE

The purpose of this in vitro study was to assess the potential benefits of eye drops based on hybrid cooperative complexes (HCCs) obtained from high and low molecular weight hyaluronic acid (HA).

METHODS

Rheological measurements were performed to adjust the HCC concentration toward optimal resistance to drainage from the ocular surface. The viscosity and mucoadhesion profiles of the optimized preparation were derived. Primary porcine corneal epithelial cells were used for biological studies. Cells were exposed to dehydration after being pretreated with the HCC solution, and protection from desiccation was evaluated using cell viability assays. Time-lapse experiments were carried out to evaluate the ability of the HCC preparation to promote corneal wound healing. The characterization studies were performed in comparison with a control HA solution representative of commercial HA-based products.

RESULTS

The HCC formulation is able to deliver twice the amount of biopolymer compared with conventional products while avoiding discomfort due to excessive viscosity. The viscosity and mucoadhesion profiles allowed the authors to predict the longer in vivo retention and, therefore, an improved HCC formulation bioavailability. The new preparation also proved superior in protecting porcine corneal epithelial cells from desiccation and in hastening corneal cell wound repair in vitro.

CONCLUSIONS

The results suggest that the developed formulation may be a promising topical ophthalmic medical treatment.

Effect of Single Instillation of Two Hyaluronic Acid-Based Topical Lubricants on Tear Film Thickness in Patients with Dry Eye Syndrome

PURPOSE

This study investigated the effect of single administration of 2 different hyaluronic acid-based topical lubricants on tear film thickness (TFT) in patients with moderate-to-severe dry eye disease (DED).

METHODS

Sixty patients were randomized to receive eye drops containing unpreserved sodium hyaluronate, triglycerides, and phospholipids (HTP), unpreserved sodium hyaluronate (HA), or unpreserved sodium chloride (NaCl). TFT and lipid layer thickness (LLT) were assessed before and at defined time points after single instillation with a custom-built ultrahigh-resolution optical coherence tomography system and a white light interferometer. Standard tests for DED such as a visual analogue scale (VAS), corneal fluorescein staining (CFS), Schirmer I test, and tear break-up time (BUT) were performed.

RESULTS

The time course in TFT was significantly different between the 3 administered agents (P < 0.001). Single administration of HTP significantly increased TFT over a period of 40 min, an increase in TFT over 20 min was observed after instillation of HA, whereas NaCl had no effect. No significant difference in the change in BUT, CFS, or LLT was observed between the 3 groups (P = 0.57, 0.97, and 0.86, respectively). A significant improvement in subjective symptoms (VAS) was found after single instillation of HTP (P = 0.03 vs. baseline) and HA, but not after administration of NaCl (P = 0.03, P < 0.01, and P = 0.08 vs. baseline, respectively, P = 0.57 between groups).

CONCLUSIONS

Single administration of HTP and HA significantly increased TFT showing a longer residence time and improved subjective symptoms, whereas instillation of NaCl had no effect. Long-term studies with multiple instillations will be necessary to further investigate the effect of the tested products on the clinical outcome. ClinicalTrials.gov ID: NCT03161080.

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.

Influence of Sodium Hyaluronate Concentration on Corneal Aberrations in Soft Contact Lens Wearers

Purpose

This study aimed to evaluate the influence of varying concentrations of sodium hyaluronate (SH) eye drops on corneal aberrations in normal individuals wearing silicone hydrogel contact lenses.

Methods

Normal individuals wearing silicone hydrogel contact lenses were enrolled in this study. Subjects were classified into two groups depending on the concentration of the preservative-free SH used (group 1, 0.1% SH; group 2, 0.3% SH). All subjects were asked to blink five times after instillation of the SH eye drop and before the Galilei measurements. Corneal aberrations were measured over the contact lenses before and after SH eye drop instillation. Visual acuity (VA) over the contact lenses was also measured both before instillation of the SH eye drop and after the subjects completed the five blinks.

Results

There was no change in VA after SH instillation in group 1; however, group 2's VA significantly deteriorated after SH instillation. Changes in VA after SH instillation compared to baseline were significantly higher in group 2 than in group 1. Similarly, the increase in corneal aberrations after SH instillation was significant in group 2 but not significant in group 1. Among the significantly increased corneal aberration parameters, defocus was the main type in group 2. Changes in corneal aberrations after SH instillation compared to baseline were significantly higher in group 2 than in group 1.

Conclusions

A 0.3%-concentration of SH increases corneal aberration and decreases VA in soft contact lens wearers. Defocus is the main type of aberration that increased in the 0.3% SH instillation group.

Investigating the potential benefits of a new artificial tear formulation combining two polymers

PURPOSE

Artificial tear formulations typically contain a water-soluble polymer to enhance residence time, moisture retention, and binding to the mucin coat of the ocular surface, which facilitate corneal healing. This study investigated the potential advantages of combining carboxymethylcellulose (CMC) and hyaluronic acid (HA) polymers in a single formulation.

MATERIALS AND METHODS

Individual CMC and HA solutions were prepared and tested for bulk viscosity in comparison to a solution that combined CMC and HA. Rheometry determined the differences between solutions at increasing shear rates, simulating eye movement and blinking.

RESULTS

The bulk viscosity of the individual 0.5% CMC and 0.1% HA solutions was 2.5 and 5.7 cP, respectively. The viscosity of the combined solution (13.1 cP) was 60% higher than predicted by additive effects. Rheometry revealed shear rates between 10/second (open eye) and 10,000/second (blinking eye). At these rates, viscosity ranged from 2.7 to 3.5 cP for 0.5% CMC, 2.8 to 6.8 cP for 0.1% HA, and 5.2 to 15.3 cP for the 0.5% CMC-0.1% HA combination. Low-shear viscosity of the CMC-HA combination increased 48% over the sum of the individual solutions, but high-shear viscosity remained virtually unchanged. Data from CMC and HA solutions at higher concentrations were consistent with these results.

CONCLUSION

Combining CMC and HA polymers produced a synergistic increase in low-shear viscosity (which cannot be fully explained by simple molecular entanglement), while the high-shear viscoelasticity of the combined solution remained unaffected. These data suggest that CMC-HA combinations have properties that may be used to formulate artificial tears that optimize ocular retention (through higher low-shear viscosity), while minimizing blur and stickiness during blinking (through lower high-shear viscosity).

Effect of different lubricant eye gels on tear film thickness as measured with ultrahigh-resolution optical coherence tomography

PURPOSE

To compare the effect of a single drop of different lubricant eye gels on tear film thickness (TFT) as measured with ultrahigh-resolution optical coherence tomography (UHR-OCT) in patients with mild-to-moderate dry eye disease (DED).

METHODS

The study followed a randomized, single-masked, observer-blinded parallel group design. Patients received a single dose of either unpreserved trehalose 3% + hyaluronic acid 0.15% (TH), hyaluronic acid 0.2% (HA) or polyethylene glycol 0.4% + propylene glycol 0.3% (PP) eye drops. In total, 60 patients were included and TFT was measured using a custom-built UHR-OCT system.

RESULTS

The mean TFT at baseline was 3.5 ± 0.7 μm. There was a significant difference in the time-course of TFT between the three groups (p = 0.001 between groups). Ten minutes after instillation, TFT increased by 155.8 ± 86.6%, 65.7 ± 71.5% and 33.4 ± 19.6% in the PP, TH and HA group, respectively (p < 0.001 between groups). Thirty minutes after instillation, the effect of all three different agents on TFT was comparable. Sixty and 120 min after administration, a significant increase in TFT was only seen for the TH group, but not for the other products (60 min: p < 0.021 between groups; 120 min: p < 0.037 between groups).

CONCLUSION

In conclusion, we observed differences in TFT after administration of the lubricant gels. Ten minutes after instillation, a pronounced increase in TFT was observed in all groups. As compared to the other products, the combination of trehalose 3% + hyaluronic acid 0.15% offers a significantly longer increase in TFT indicating for a longer residence time.

Safety and Efficacy of Cortisol Phosphate in Hyaluronic Acid Vehicle in the Treatment of Dry Eye in Sjogren Syndrome

PURPOSE

Evaluation of 0.3% cortisol phosphate eye drops in hyaluronic acid vehicle in the treatment of dry eye in Sjogren Syndrome.

METHODS

This prospective, single-center, masked (single blind), randomized controlled study included 40 female patients divided into 2 groups, group 1 treated with Idracemi, 0.3% cortisol phosphate eye drops twice a day, and group 2 treated with Cortivis, 0.3% cortisol phosphate in hyaluronic acid vehicle, with the same posology. Screening (day -7), randomization (day 0), follow-up (day 7), and termination (day 28) visits were conducted. Symptoms (VAS) questionnaire, tear film breakup time, corneo-conjunctival stain, intraocular pressure (IOP) measurement, and fundus examination were performed at each visit. Conjunctival impression cytology for human leukocyte antigen-DR (HLA-DR) expression at visit 1 and 4 was also performed.

RESULTS

No changes in IOP or fundus examination were observed in either group at each time point. Group 1 showed at day 28 a statistically significant amelioration of symptoms and reduction of HLA-DR expression. Group 2 showed at day 7 statistically significant improvement of corneal and conjunctival stain versus baseline and versus group 1; the symptom score was statistically significantly better than baseline and versus group 1 after 28 days too. The HLA-DR expression and the epithelial cell area were statistically significantly reduced versus baseline and versus group 1 at the same time.

CONCLUSIONS

Cortisol phosphate proved to be safe and effective in treating dry eye in Sjogren Syndrome patients in both formulations. However, the formula with hyaluronic acid vehicle proved to be more effective. Both formulations were very well tolerated.

Increased concentration of hyaluronan in tears after soaking contact lenses in Biotrue multipurpose solution

Purpose

This study was conducted to determine 1) the concentration of hyaluronan (HA) in the tear films of contact lens (CL) wearers versus non-CL wearers and 2) whether HA sorbed from Biotrue, an HA-containing multipurpose solution (MPS), onto senofilcon A lenses affects the concentration of HA in tears after 2 hours of wear.

Patients and methods

Tears of habitual CL wearers and non-CL wearers were collected on Schirmer strips at baseline and after 2 hours of wear of senofilcon A CLs that had first been either rinsed with Sensitive Eyes Saline or soaked in Biotrue MPS for 14 hours. HA concentrations were measured by enzyme-linked immunosorbent assay (ELISA) and adjusted for sample volumes.

Results

No difference in baseline concentrations of HA in tears was found between CL wearers and non-CL wearers (P=0.07), nor between males and females (P=0.06). However, age was significantly negatively associated with HA concentration (P<0.01), and mostly, CL wear contributed to a significant association (P<0.01). Among saline-rinsed CL wearers, no change in HA concentration in tears was observed after 2 hours of wear (P=0.38). By contrast, a significant increase in HA concentration was observed in the tears from eyes that had worn CLs soaked in Biotrue MPS when compared to baseline (P=0.01) or to saline-rinsed control (P=0.03).

Conclusion

1) In this study population, no difference in baseline concentration of HA was observed between CL wearers and non-CL wearers, and 2) after 2 hours of wear of senofilcon A lenses that were soaked in Biotrue MPS, HA concentrations in the tear films of CL wearers increased.

Development of a UPLC-MS/MS method for the determination of lomefloxacin in rabbit aqueous humor and its application to a pharmacokinetic study

Lomefloxacin is a kind of synthetic fluoroquinolone antibiotic, which is used for the treatment of infectious diseases. In this study, a rapid and efficient liquid chromatography-tandem mass spectrometric assay was developed to determine the concentration of lomefloxacin in rabbit aqueous humor quantitatively. Aqueous humor samples were extracted by protein precipitation. Ofloxacin was chosen as internal standard. The chromatographic separation was achieved on a Kinetex C18 (50mm×2.10mm, 2.6μm, Phenomenex Corp, USA) column, with a gradient of methanol (0.1% formic acid) and water (0.1% formic acid). Multiple reaction monitoring (MRM) with positive ionization mode was used for the mass analysis. The validation of this method was based on the European Medicines Agency (2011) [1] and US FDA Guidelines (2001) [2]. The calibration range of aqueous humor samples was 5-1200ng/mL with r=0.9990 (n=6). For all QC samples, Inter-and intra-run precisions were less than 15% and accuracies were between 80%-120%. In conclusion, the assay was rapid, sensitive and able to determinate the lomefloxacin in rabbit aqueous humor accurately. At the same time, this method was successfully applied to study the pharmacokinetics of lomefloxacin hydrochloride eye drops and lomefloxacin hydrochloride ophthalmic gel in rabbit aqueous humor.

Optimization of hyaluronan-based eye drop formulations

Hyaluronan (HA) is frequently incorporated in eye drops to extend the pre-corneal residence time, due to its viscosifying and mucoadhesive properties. Hydrodynamic and rheological evaluations of commercial products are first accomplished revealing molecular weights varying from about 360 to about 1200kDa and viscosity values in the range 3.7-24.2mPa s. The latter suggest that most products could be optimized towards resistance to drainage from the ocular surface. Then, a study aiming to maximize the viscosity and mucoadhesiveness of HA-based preparations is performed. The effect of polymer chain length and concentration is investigated. For the whole range of molecular weights encountered in commercial products, the concentration maximizing performance is identified. Such concentration varies from 0.3 (wt%) for a 1100kDa HA up to 1.0 (wt%) for a 250kDa HA, which is 3-fold higher than the highest concentration on the market. The viscosity and mucoadhesion profiles of optimized formulations are superior than commercial products, especially under conditions simulating in vivo blinking. Thus longer retention on the corneal epithelium can be predicted. An enhanced capacity to protect corneal porcine epithelial cells from dehydration is also demonstrated in vitro. Overall, the results predict formulations with improved efficacy.

Mechanistic modeling of ophthalmic drug delivery to the anterior chamber by eye drops and contact lenses

Ophthalmic drug for the anterior chamber diseases are delivered into tears by either eye drops or by extended release devices placed in the eyes. The instilled drug exits the eye through various routes including tear drainage into the nose through the canaliculi and transport across various ocular membranes. Understanding the mechanisms relevant to each route can be useful in predicting the dependency of ocular bioavailability on various formulation parameters, such as drug concentration, salinity, viscosity, etc. Mathematical modeling has been developed for each of the routes and validated by comparison with experiments. The individual models can be combined into a system model to predict the fraction of the instilled drug that reaches the target. This review summarizes the individual models for the transport of drugs across the cornea and conjunctiva and the canaliculi tear drainage. It also summarizes the combined tear dynamics model that can predict the ocular bioavailability of drugs instilled as eye drops. The predictions from the individual models and the combined model are in good agreement with experimental data. Both experiments and models predict that the corneal bioavailability for drugs delivered through eye drops is less than 5% due to the small area of the cornea in comparison to the conjunctiva, and the rapid clearance of the instilled solution by tear drainage. A contact lens is a natural choice for delivering drugs to the cornea due to the placement of the contact in the immediate vicinity of the cornea. The drug released by the contact towards the cornea surface is trapped in the post lens tear film for extended duration of at least 30min allowing transport of a large portion into the cornea. The model predictions backed by in vivo animal and clinical data show that the bioavailability increases to about 50% with contact lenses. This realization has encouraged considerable research towards delivering ocular drugs by contact lenses. Commercial contacts are, however, not ideal for drug delivery due to the short release durations which may necessitate wearing multiple lenses each day, reducing the viability of this approach. Recent research has focused on designing contacts that retain all critical properties while increasing the release durations to a few hours or a few days. Beagle dog studies with contact lenses containing vitamin E nanobarriers to attenuate drug transport have shown promising results. Human studies using contacts for drug delivery have also been conducted for allergy therapy but drug eluting contacts are not available in the market for any therapy.

Hyaluronic acid-coated niosomes facilitate tacrolimus ocular delivery: Mucoadhesion, precorneal retention, aqueous humor pharmacokinetics, and transcorneal permeability

Tacrolimus (FK506) was used to prevent corneal allograft rejection in patients who were resistant to steroids and cyclosporine. However, the formulation for FK506 ocular delivery remained a challenge due to the drug's high hydrophobicity, high molecular weight, and eye's physiological and anatomical constraints. The aim of this project is to develop an ocular delivery system for FK506 based on a combined strategy of niosomes and mucoadhesive hyaluronic acid (HA), i.e., FK506HA-coated niosomes, which exploits virtues of both niosomes and HA to synergistically improve ophthalmic bioavailability. The FK506HA-coated niosomes were characterized with particle size, zeta potential, and rheology behavior. Mucoadhesion of FK506HA-coated niosomes to mucin was investigated through surface plasmon resonance in comparison with non-coated niosomes and HA solution. The results showed that niosomes possessed adhesion to mucin, and HA coating enhanced the adhesion. The in vivo precorneal retention was evaluated in rabbit, and the results showed that HA-coated niosomes prolonged the residence of FK506 significantly in comparison with non-coated niosomes or suspension. Aqueous humor pharmacokinetics test showed that area under curve of HA-coated niosomes was 2.3-fold and 1.2-fold as that of suspension and non-coated niosomes, respectively. Moreover, the synergetic corneal permeability enhancement of the hybrid delivery system on FK506 was visualized and confirmed by confocal laser scanning microscope. Overall, the results indicated that the hybrid system facilitated FK506 ocular delivery on mucoadhesion, precorneal retention, aqueous humor pharmacokinetics and transcorneal permeability. Therefore, HA-coated niosomes may be a promising approach for ocular targeting delivery of FK506.

The Effect of Tear Supplementation on Ocular Surface Sensations during the Interblink Interval in Patients with Dry Eye

PURPOSE

To investigate the characteristics of ocular surface sensations and corneal sensitivity during the interblink interval before and after tear supplementation in dry eye patients.

METHODS

Twenty subjects (41.88±14.37 years) with dry eye symptoms were included in the dry eye group. Fourteen subjects (39.13±11.27 years) without any clinical signs and/or symptoms of dry eye were included in the control group. Tear film dynamics was assessed by non-invasive tear film breakup time (NI-BUT) in parallel with continuous recordings of ocular sensations during forced blinking. Corneal sensitivity to selective stimulation of corneal mechano-, cold and chemical receptors was assessed using a gas esthesiometer. All the measurements were made before and 5 min after saline and hydroxypropyl-guar (HP-guar) drops.

RESULTS

In dry eye patients the intensity of irritation increased rapidly after the last blink during forced blinking, while in controls there was no alteration in the intensity during the first 10 sec followed by an exponential increase. Irritation scores were significantly higher in dry eye patients throughout the entire interblink interval compared to controls (p<0.004). NI-BUT significantly increased after HP-guar (p = 0.003) but not after saline drops (p = 0.14). In both groups, either after saline or HP-guar the shape of symptom intensity curves remained the same with significantly lower irritation scores (p<0.004), however after HP-guar the decrease was significantly more pronounced (p<0.004). Corneal sensitivity to selective mechanical, cold and chemical stimulation decreased significantly in both groups after HP-guar (p<0.05), but not after saline drops (p>0.05).

CONCLUSION

Ocular surface irritation responses due to tear film drying are considerably increased in dry eye patients compared to normal subjects. Although tear supplementation improves the protective tear film layer, and thus reduce unpleasant sensory responses, the rapid rise in discomfort is still maintained and might be responsible for the remaining complaints of dry eye patients despite the treatment.

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.

Tear break-up time for tear film evaluation: Are moistening solutions interchangeable?

PURPOSE

It was the main purpose of this study to investigate the influence of the moistening solution on TBUT measurements in an asymptomatic population.

METHODS

An online survey was employed to determine the compliance of Spanish eye care practitioners with the recommended normalized procedure to administer TBUT. For the purpose of examining the clinical relevance of discrepancies from the recommended procedure, a randomized, double-masked, bilateral study was designed in which a micropipette was used to moisten fluorescein strips with a controlled volume of six different solutions, commonly available in the contact lens office, and TBUT was measured in 58 non-dry eye (OSDI<15) subjects (age from 19 to 32 years).

RESULTS

Results from the online survey revealed that 64% of Spanish practitioners frequently use (or have used) different solutions to moisten fluorescein strips during TBUT assessment. Statistically significant differences in TBUT values were found between the various solutions as a whole (χ(2)=198.384, p<0.001), as well as between all solutions when explored pair-wise (all p<0.001), except for the two saline solutions.

CONCLUSIONS

The present findings support the relevance of selecting the appropriate solution when conducting TBUT for the evaluation of the tear film. Deviations from the recommended procedure may result in misdiagnosis of dry eye and unnecessary patient referral.

Assessment of dry eye signs and symptoms and ocular tolerance of a preservative-free lacrimal substitute (Hylabak®) versus a preserved lacrimal substitute (Systane®) used for 3 months in patients after LASIK

Laser-assisted in situ keratomileusis (LASIK) is commonly used to correct refractive defects. The procedure frequently results in dry eye symptoms, usually of short but sometimes longer duration. This study was designed to assess dry eye and ocular tolerability after LASIK in patients treated with a preservative-free lacrimal substitute (Hylabak®) or preserved lacrimal substitute (Systane®). In a single-center, investigator-masked, prospective, noninferiority, clinical study, patients undergoing LASIK surgery were randomized to receive Hylabak or Systane eye drops (one drop in each eye four times daily for 3 months). Fluorescein test scores were the primary efficacy variable and were similar on day 1 (mean 0.26 and 0.28 for Hylabak and Systane, respectively). At the final visit (day 84 ± 3) the fluorescein scores had improved to 0.11 and 0.04, respectively. The difference was not significant and thus noninferiority was established. A trend of more rapid improvement in the Hylabak group was evident. Both treatments were well tolerated and there were no serious adverse events, discontinuations for adverse events or other safety-related reasons, and no systemic adverse events. The results suggest that Hylabak is not less effective than Systane in reducing the symptoms of dry eye after LASIK surgery.

The effect of pH, dilution, and temperature on the viscosity of ocular lubricants--shift in rheological parameters and potential clinical significance

OBJECTIVE

To investigate the effect of temperature, dilution, and pH on the viscosity of ocular lubricants.

DESIGN

Laboratory based investigation of viscosity.

PARTICIPANTS

No human subjects.

METHODS

Hypromellose 0.3%, sodium hyaluronate 0.4%, carboxymethylcellulose sodium 0.5%/glycerin 0.9%, and carmellose sodium 0.5% were investigated. Ostwald capillary viscometers were utilised for viscosity measurements. The kinematic viscosity of each lubricant was tested quantitatively from 22 to 40 °C, and over a pH range of 5-8 under isothermal conditions. The kinematic viscosity of each eye drop was also tested under dilution by varying the mass fraction of each eye drop under isothermal conditions.

MAIN OUTCOME MEASURE

Changes in kinematic viscosity.

RESULTS

Hypromellose 0.3% had an initial pH of 8.34, while the other lubricants had a pH close to neutral. From 22 to 35 °C, the kinematic viscosity of sodium hyaluronate 0.4 fell by 36% from 37.8 to 24.4 mm(2)/s, carboxymethylcellulose sodium 0.5%/glycerin 0.9% fell by 35% from 16.98 to 11.1 mm(2)/s, hypromellose fell by 37% from 6.89 to 3.69 mm(2)/s, and carmellose sodium 0.5% fell by 25% from 2.77 to 1.87 mm(2)/s. At 32 °C only sodium hyaluronate 0.4%, and carboxymethylcellulose sodium 0.5%/glycerin 0.9% retained sufficient kinematic viscosity to maintain precorneal residence. Kinematic viscosities of all the topical lubricants were unaffected by pH but decreased significantly with dilution.

CONCLUSIONS

This study suggests that currently used ocular lubricants have limited bioavailability due to reductions in viscosity by temperature and dilutional changes under physiological conditions. Developing lubricants with stable viscosities may maximise therapeutic efficacy.

Tear Dynamics Model

PURPOSE

Quantitative understanding of tear dynamics may help in developing better ophthalmic drug delivery vehicles and dry eye treatments. This paper attempts to develop a comprehensive model that can predict the effect of physiological parameters on various issues related to tear dynamics.

METHODS

The model is based on mass balances of water and solutes such as glucose, sodium, potassium, and chloride. The mass balances require models for the drainage of fluid through the canaliculi and the transport of tears and solutes through the conjunctiva. The model parameters are obtained by simulating Ussing-chamber experiments. The differential equations for the unsteady balances are solved numerically.

RESULTS

The model predicts that under normal conditions, the tear volume, tear osmolarity and potential are 7.1 microl, 297.6 mM, and -15.1 mV, respectively. The model also predicts that the conjunctiva is secretory and contributes about 25% of the total tear production. We also predict the effect of evaporation on tear physiology and show that an increase in evaporation increases osmolarity, reduces tear volume, and increases conjuctival secretion. Additionally, the new tear dynamics model helps assess the effect of osmolarity of the instilled drops, insertion of punctum plugs and use of moisture chamber as treatments for dry eyes. Furthermore, the model is used to predict the effect of modulation of specific transport pathways, which is proposed as a potential remedy for dry eyes, on conjuctival secretion and total tear volume.

CONCLUSIONS

Most of the predicted results agree with the reported experimental results, at least qualitatively. However, some predictions disagree with experiments suggesting that further improvements in the model are needed. The model developed in this paper can improve our understanding of tear dynamics and also serve as a tool to evaluate the efficacy of various modalities at treating dry eyes.

A Mathematical Model for Ocular Tear and Solute Balance

PURPOSE

In this paper we develop a mathematical model that can predict the steady-state tear film thickness and the dynamic tear film thickness and the solute concentration after instillation of a solute-laden fluid in the eye.

METHODS

The mathematical model developed in this paper is based on a balance between the inflow and outflow of tears into the tear film. It incorporates a tear drainage model and a model that relates the tear film thickness to the meniscus radius of curvature. To predict the solute concentrations, the tear balance is coupled with the solute balance. The differential equations for the unsteady balances are solved numerically.

RESULTS

The model predicts that the tear film thickness depends on a number of physiological factors, such as rates of tear production and evaporation, geometry and modulus of the canaliculi, and surface tension and viscosity of tears, and varies from about 3 to 15 microm. The model also predicts that the drainage time for an instilled volume of 15 microl is 1283 s. Additionally, the time required for the tracer concentration to decay to 1% of the value immediately after instillation of a drug-laden 40 microl drop is about 2480 s. Similarly, the time for intensity decay for a radioactive tracer after 25 microl instillation is about 1566 s. Also, the model predicts that the fraction of the instilled drug that reaches the cornea is about 1.3% for topical application of timolol.

CONCLUSIONS

The predicted results agree reasonably with the reported experimental results, at least qualitatively. The model developed here can serve as a useful tool to develop a more precise understanding of various issues related to tears and also evaluate the effect of various parameters on the tear volume.