Retention and Retention of Effect of Topical Formulations in Dry Eye Subjects

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.

Evaluation of different treatment modalities on the efficacy of hydroxypropyl Guar (HP-Guar) formulation on tear film stability (TFS) in subjects exposed to adverse environmental conditions

The study aimed to assess the efficacy of hydroxypropyl guar (HP) formulation (Systane) to protect tear film parameters under desiccating environment using protection and relief treatment modalities. The subjects were exposed to adverse environmental conditions using a Controlled Environment Chamber (CEC) where the relative humidity (RH) was 5% and the ambient temperature was 21 °C and screened for Tear break-up time (TBUT), Tear film evaporation rate (TFER) and lipid layer thickness (LLT) using the HIRCAL grid, Servomed EP3 Evaporimeter and Keeler's TearScope-Plus respectively. Significant improvement in LLT was noticed in the protection modality. The mean tear film evaporation rate doubled after exposure to the humidity of 5% to a value of 105.37 g/m²/h (0.29 µl/min). All subjects displayed a significant reduction in non-invasive tear break-up time (NITBUT) with a mean NITBUT of 7.7 s after exposure to a desiccating environment for 15 min. A significant increase in NITBUT after the instillation of the drops was recorded in both methods. The results obtained from this study showed that a solution containing HP-Guar significantly improves tear film parameters under a desiccating environment. Apart from the tear evaporation rate, all tear parameters showed improvement after the use of HP-Guar eye drops. It is evident that tear film parameters respond differently to the management modalities and using CEC has the potential to provide researchers with a readily available method to evaluate the efficiency of tear supplementation.

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.

Does the temperature of an artificial tear affect its comfort?

BACKGROUND

Refrigerated eye-drops have been advocated in cases of ocular allergies to provide a soothing effect upon instillation. This notion continues to be promoted by practitioners for artificial tears (AT) in the management of dry eye (DE) with little support in the literature. To further substantiate claims of a soothing effect of cold eye-drops, the aim of this study was to determine if refrigeration of an AT enhanced the subjective comfort upon instillation.

METHODS

Participants with mild to moderate DE participated in an open label contralateral study of two weeks duration. Each participant instilled Systane Ultra (Alcon Laboratories) in the morning (between 6.00-10.00 hours) and in the evening (between 18.00-22.00 hours). Participants were asked to report the subjective comfort immediately after both of these instillations, on a scale from 1 (poor) to 10 (excellent). This was done for ambient (aAT) and refrigerated (rAT) drops. An in vitro study evaluated if there were any changes in eye-drop pH and osmolarity with refrigeration.

RESULTS

Participants (n = 18, three male, 15 female, age 22-28 years, average 24.4 ± 1.6) reported mean comfort scores (± standard deviation) of 7.8 ± 0.9 and 7.6 ± 1.4, for the aAT and the rAT, respectively. Mean comfort scores (± standard deviation) for morning and evening, were 7.7 ± 1.2 and 7.8 ± 1.1, respectively. A non-parametric Friedman test of differences among repeated measures was conducted and rendered a chi-squared value of 3.74, which was not statistically significant (p = 0.29). The pH remained stable at 8.0 and the osmolality did not vary significantly with refrigeration.

CONCLUSION

There is no advantage, with respect to patient perceived comfort, in refrigerating the Systane Ultra (Alcon Laboratories) AT for mild to moderate DE.

Lacosamide diminishes dryness-induced hyperexcitability of corneal cold sensitive nerve terminals

Lacosamide is an anti-epileptic drug that is also used for the treatment of painful diabetic neuropathy acting through voltage-gated sodium channels. The aim of this work was to evaluate the effects of acute application of lacosamide on the electrical activity of corneal cold nerve terminals in lacrimo-deficient guinea pigs. Four weeks after unilateral surgical removal of the main lachrimal gland in guinea pigs, corneas were excised and superfused in vitro at 34°C for extracellular electrophysiological recording of nerve terminal impulse activity of cold thermosensitive nerve terminals. The characteristics of the spontaneous and the stimulus-evoked (cooling ramps from 34°C to 15°C) activity before and in presence of lacosamide 100µM and lidocaine 100µM were compared. Cold nerve terminals (n=34) recorded from dry eye corneas showed significantly enhanced spontaneous activity (8.0±1.1 vs. 5.2±0.7imp/s; P<0.05) and cold response (21.2±1.7 vs. 16.8±1.3imp/s; P<0.05) as well as reduced cold threshold (1.5±0.1 vs. 2.8±0.2 Δ°C; P<0.05) to cooling ramps compared to terminals (n=58) from control animals. Both lacosamide and lidocaine decreased spontaneous activity and peak response to cooling ramps significantly (P<0.05). Temperature threshold was increased by the addition of lidocaine (P<0.05) but not lacosamide (P>0.05) to the irrigation fluid. In summary, the application of lacosamide results in a significant decrease of the augmented spontaneous activity and responsiveness to cold of corneal sensory nerves from tear-deficient animals. Based on these promising results we speculate that lacosamide might be used to reduce the hyperexcitability of corneal cold receptors caused by prolonged ocular surface dryness due to hyposecretory or evaporative dry eye disease.

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.

Artificial tears potpourri: a literature review

Numerous brands and types of artificial tears are available on the market for the treatment of dysfunctional tear syndrome. Past literature has focused on comparing the components of these products on patient’s clinical improvement. The wide array of products on the market presents challenges to both clinicians and patients when trying to choose between available tear replacement therapies. Different formulations affect patients based on etiology and severity of disease. In order to provide an unbiased comparison between available tear replacement therapies, we conducted a literature review of existing studies and National Institutes of Health clinical trials on commercially available, brand name artificial tears. Outcomes evaluated in each study, as well as the percent of patients showing clinical and symptomatic improvement, were analyzed. Fifty-one studies evaluating different brands of artificial tears, and their efficacy were identified. Out of the 51 studies, 18 were comparison studies testing brand name artificial tears directly against each other. Nearly all formulations of artificial tears provided significant benefit to patients with dysfunctional tear syndrome, but some proved superior to others. From the study data, a recommended treatment flowchart was derived.

Mucoadhesive chitosan-dextran sulfate nanoparticles for sustained drug delivery to the ocular surface

PURPOSE

To characterize nanoparticles produced by self-assembly of oppositely charged polymers, cationic chitosan (CS), and anionic dextran sulfate (DS), for drug delivery to the ocular surface. The goal is to overcome the short residence time of topical drugs through their sustained release from mucoadhesive nanoparticles.

METHODS

Chitosan-dextran sulfate nanoparticles (CDNs) were produced by mixing CS and DS; polyethylene glycol-400 was used as a surface stabilizing agent. Fourier transform infrared spectroscopy (FTIR) spectra of CS, DS, and CDNs were determined in the wavenumber range of 4,000-700 cm(-1) to assess the ionic interactions in the formation of CDNs. The physicochemical properties, entrapment efficacy, and dissolution profile of CDNs were investigated using Rhodamine B (RhB) and Nile Red (NR) as drug analogs. The mucoadhesiveness of the CDNs was assessed by imaging the retention of the fluorescein isothiocyanate-labeled CDNs on the cornea ex vivo, which was subjected to shear stress by a steady stream of saline solution.

RESULTS

CDNs were obtained by the polyelectrolyte complexation technique. The FTIR spectra of CDNs showed spectral shifts in the amine and sulfate regions, confirming an involvement of electrostatic interactions between cationic CS and anionic DS. The CDNs were spherical in shape and segregated. They possessed a particle size of ~400 nm with a polydispersity index of 0.3 and exhibited a zeta potential of ~40 mV. A high entrapment efficacy of up to 80% was observed with both RhB and NR. In the dissolution experiments, NR was released from CDNs within 60 min, but RhB was not released. This indicates that the release of drugs could depend on their molecular interactions with the particle. Exposure of CDNs to lysozyme, which is found in tears, had no effect on the mean particle size or the surface charge. Instillation of NR, RhB, and FITC in the presence of saline irrigation resulted in their rapid disappearance (<5 min) from the corneal surface. In contrast, fluorescent CDNs showed retention on the cornea even after 60 min.

CONCLUSIONS

Cationic and biocompatible mucoadhesive CDNs have been developed for sustained drug delivery to the ocular surface. The CDNs were stable to lysozyme and showed prolonged adherence to the corneal surface.

Cytotoxic and Inflammatory Effects of Contact Lens Multipurpose Solutions on Human Corneal Epithelial Cells

Multipurpose solutions (MPSs) are the leading method for cleaning and disinfecting soft contact lenses (CLs). During recent years, numerous clinical studies have evaluated the MPS damage to the ocular surface. This study examined the cytotoxic and the inflammatory effects of MPSs and hydrogen peroxide disinfection system (H202) compared to appropriate controls on human corneal epithelial (HCE) cells. Primary cultured HCE cells were exposed to eight different commercially available MPS products (MPS A, ReNu MultiPlus®; MPS B, Opti Free® EverMoist; MPS C, Solo-care Aqua®; MPS-D, Complete®; MPS-E, Unica Sensitive®; MPS-F, Options Multi®; MPS-G, Biotrue®; MPS-H, COMPLETE® RevitaLens). Morphological changes and cytotoxic effects were examined with FITC-Annexin V/PI and MTT assays. The protein contents of the inflammatory cytokines interleukin (IL)-1β, TNF-α, IL-6 and IL-8 were examined by multiplex fluorescent bead immunoassay (FBI), and the mRNA expression was examined by real time PCR. Lipopolysaccharide (LPS) with 500 ng/ml CD14 and 500 ng/ml LBP (LPS complex), polyinosinic: polycytidylic acid (Poly I:C) and un-neutralized H202 served as positive controls, respectively. Phosphate-buffered saline (PBS) was added as a negative control. The study demonstrated that most of the MPSs induced varying degrees of cytotoxicity to HCE cells, and increased production of pro-inflammatory cytokines compared to the negative control. In addition, several MPS increased the mRNA level of inhibitory factor-κBα (1-κBα). Among the various MPSs, MPS-H induced the highest protein contents of the pro-inflammatory cytokines (14.37±2.2-fold for TNF-α, 41.39±2.5-fold for IL-1β and 5.24±0.6-fold for IL-6) compared to the negative control (p<0.05). In contrast, no significant differences were noted between the neutralized H202 and the negative control. We conclude that most of the currently used MPSs induce significant damage and inflammatory response in corneal epithelial cells. MPS-induced inflammation was mediated through NF-κB signal transduction. This study demonstrates for the first time inflammatory responses at the molecular level in primary HCE cells following exposure to a large series of commercially available and commonly used MPSs. These findings strongly suggest that certain MPSs may be partially involved in the pathogenesis of contact lens intolerance. Therefore, we recommend that practitioners advise patients as to the preferable disinfecting contact lens solutions, and to consider using the hydrogen peroxide disinfection systems instead.

Systane lubricant eye drops in the management of ocular dryness

The understanding of dry eye disease has advanced recently through increasing recognition that the etiology of the condition involves both tear evaporation and insufficient tear production, and that tear film instability and inflammation play roles in the various stages of the disease. Of significance, it has been recognized that lipid layer thickness correlates with tear film stability. The management of dry eye involves various strategies and therapeutic approaches that address one or more etiopathological components of the disease. The purpose of this review is to outline the characteristics and clinical utility of the Systane(®) ocular lubricants that contain hydroxypropyl-guar and one or both of the demulcents, ie, polyethylene glycol 400 and propylene glycol. Clinically, these products are safe and are indicated for the temporary relief of burning and irritation due to dryness of the eye. In particular, this review describes the formulations, mechanisms of action, and clinical utility of the newest additions to this topical ocular lubricant family, Systane Ultra(®) and Systane Balance(®). Both of these ocular products are formulated with an intelligent delivery system and both provide symptomatic relief to patients with dry eye. However, Systane Balance is a novel formulation that contains both polymer and lipid components designed to protect the ocular surface and replenish tear film lipids simultaneously, a factor that is of particular relevance to patients who have dry eye associated with meibomian gland dysfunction.