In Vivo Effects of Preservative-free and Preserved Prostaglandin Analogs: Mouse Ocular Surface Study

Preservatives and ocular surface disease: A review

Ocular surface disease (OSD) is a complex condition that can cause a range of symptoms (e.g, dryness, irritation, and pain) and can significantly impact the quality of life of affected individuals. Iatrogenic OSD, a common finding in patients with glaucoma who receive chronic therapy with topical ocular antihypertensive drugs containing preservatives such as benzalkonium chloride (BAK), has been linked to damage to the ocular surface barrier, corneal epithelial cells, nerves, conjunctival goblet cells, and trabecular meshwork. Chronic BAK exposure activates inflammatory pathways and worsens symptoms, compromising the success of subsequent filtration surgery in an exposure-dependent manner. In eyes being treated for glaucoma, symptomatic treatment of OSD may provide some relief, but addressing the root cause of the OSD often necessitates reducing or, ideally, eliminating BAK toxicity. Strategies to decrease BAK exposure in patients with glaucoma encompass the use of preservative-free formulations or drugs with alternative and less toxic preservatives such as SofZia®, Polyquad, potassium sorbate, or Purite®. Though the benefits of these alternative preservatives are largely unproven, they might be considered when financial constraints prevent the use of preservative-free versions. For patients receiving multiple topical preserved drugs, the best practice is to switch to nonpreserved equivalents wherever feasible, regardless of OSD severity. Furthermore, nonpharmacological approaches, including laser or incisional procedures, should be considered. This review explores the effects of BAK on the ocular surface and reviews strategies for minimizing or eliminating BAK exposure in patients with glaucoma in order to significantly improve their quality of life and prevent complications associated with chronic exposure to BAK.

Benzalkonium chloride greatly deteriorates the biological activities of human corneal stroma fibroblasts in a concentration-dependent manner

BACKGROUND

Corneal tissues indirectly obtain nutritional needs and oxygen to maintain their homeostasis, and therefore, benzalkonium chloride (BAC) containing ocular instillations for medical therapy may, in turn, induce toxic effects more than expected in corneal tissues, especially the inside stroma layer.

METHODS

To evaluate the effects of very low concentrations (10-8%, 10-6%, or 10-4%) of BAC on human corneal stroma, we used two-dimensional (2D) cultures of human corneal stromal fibroblast (HCSF) cells and carried out the following analyses: (1) cell viability measurements, (2) Seahorse cellular bio-metabolism analysis, and (3) the expression of ECM molecules and endoplasmic reticulum (ER) stress-related molecules.

RESULTS

In the absence and presence of 10-8%, 10-6%, or 10-4% concentrations of BAC, cell viability deteriorated and this deterioration was dose-dependent. The results showed that maximal mitochondrial respiration was decreased, the mRNA expression of most of ECM proteins was decreased, and ER stress-related molecules were substantially and dose-dependently down-regulated in HCSFs by the BAC treatment.

CONCLUSIONS

The findings reported herein indicate that the presence of BAC, even at such low concentrations, is capable of causing the deterioration of cellular metabolic functions and negatively affecting the response to ER stress in HCSF cells resulting in a substantially decreased cellular viability.

From Eye Care to Hair Growth: Bimatoprost

BACKGROUND

Bimatoprost has emerged as a significant medication in the field of medicine over the past several decades, with diverse applications in ophthalmology, dermatology, and beyond. Originally developed as an ocular hypotensive agent, it has proven highly effective in treating glaucoma and ocular hypertension. Its ability to reduce intraocular pressure has established it as a first-line treatment option, improving management and preventing vision loss. In dermatology, bimatoprost has shown promising results in the promotion of hair growth, particularly in the treatment of alopecia and hypotrichosis. Its mechanism of action, stimulating the hair cycle and prolonging the growth phase, has led to the development of bimatoprost-containing solutions for enhancing eyelash growth.

AIM

The aim of our review is to provide a brief description, overview, and studies in the current literature regarding the versatile clinical use of bimatoprost in recent years. This can help clinicians determine the most suitable individualized therapy to meet the needs of each patient.

METHODS

Our methods involve a comprehensive review of the latest advancements reported in the literature in bimatoprost formulations, which range from traditional eye drops to sustained-release implants. These innovations offer extended drug delivery, enhance patient compliance, and minimize side effects.

RESULTS

The vast literature published on PubMed has confirmed the clinical usefulness of bimatoprost in lowering intraocular pressure and in managing patients with glaucoma. Numerous studies have shown promising results in dermatology and esthetics in promoting hair growth, particularly in treating alopecia and hypotrichosis. Its mechanism of action involves stimulating the hair cycle and prolonging the growth phase, leading to the development of solutions that enhance eyelash growth. The global use of bimatoprost has expanded significantly, with applications growing beyond its initial indications. Ongoing research is exploring its potential in glaucoma surgery, neuroprotection, and cosmetic procedures.

CONCLUSIONS

Bimatoprost has shown immense potential for addressing a wide range of therapeutic needs through various formulations and advancements. Promising future perspectives include the exploration of novel delivery systems such as contact lenses and microneedles to further enhance drug efficacy and patient comfort. Ongoing research and future perspectives continue to shape its role in medicine, promising further advancements and improved patient outcomes.

Differential Effects of Benzalkonium Chloride on Human Trabecular Meshwork Cells Not Treated or Treated with Transforming Growth Factor-β2 or Dexamethasone

Purpose: The objective of the present study was to evaluate the effects of low concentrations of benzalkonium chloride (BAC) (10-7%, 10-6%, or 10-5%) on healthy and glaucomatous human trabecular meshwork (HTM) cells. For this purpose, we used in vitro models replicating a healthy HTM and HTM with primary open-angle glaucoma (POAG) or steroid-induced glaucoma (SG) using two-dimensional (2D) cultures of HTM cells not treated or treated with a 5 ng/mL solution of transforming growth factor-β2 or 250 nM dexamethasone (DEX). Methods: Analyses were carried out for (1) the intercellular affinity function of 2D HTM monolayers, as determined by transepithelial electrical resistance (TEER) measurements; (2) cell viability; (3) cellular metabolism by using a Seahorse bioanalyzer; and (4) expression of extracellular matrix (ECM) molecules, an ECM modulator, and cell junction-related molecules. Results: In the absence and presence of BAC (10-7% or 10-5%), intercellular affinity function determined by TEER and cellular metabolic activities were significantly and dose dependently affected in both healthy and glaucomatous HTM cells despite the fact that there was no significant decrease in cell viabilities. However, the effects based on TEER values were significantly greater in the healthy HTM. The mRNA expression of several molecules that were tested was not substantially modulated by these concentrations of BAC. Conclusions: The findings reported herein suggest that low concentrations of BAC may have unfavorable adverse effects on cellular metabolic capacity by inducing increases in the intercellular affinity properties of the HTM, but those effects of BAC were different in healthy and glaucomatous HTM cells.

A Preservative-Free Approach - Effects on Dry Eye Signs and Symptoms After Cataract Surgery

Purpose

To compare the effect of treatment with preservative-free dexamethasone, NSAIDs and trehalose/hyaluronic acid eye drops with the preservative benzalkonium chloride containing dexamethasone and NSAIDs after cataract surgery in dry versus non-dry eyes.

Patients and Methods

In this prospective randomized intervention study, dry eye tests were performed before and 6 weeks after cataract surgery. Patients were considered as having dry eye, SDE (sign of dry eye), if at least one of the following dry eye tests were abnormal; corneal fluorescein staining (CFS), non-invasive keratograph breakup time (NIKBUT) or tear osmolarity. Patients with SDE were randomly assigned to one of two groups. Group 1 patients were treated with dexamethasone and bromfenac eye drops with the preservative benzalkonium chloride (BAC). Group 2 patients were treated with preservative-free dexamethasone and preservative-free diclofenac, as well as a preservative-free lubricant with trehalose and hyaluronic acid both before and after surgery. Patients with normal tear film status acted as the control group (group 3) and received same treatment as group 1.

Results

A total of 215 patients were enrolled six weeks after surgery, the number of patients with SDE decreased significantly in groups 1 and 2 (p <0.001). Subjective symptoms and objective measures including osmolarity, NIKBUT, CFS, and tear film thickness (TFT) improved after surgery, tear production remained unchanged, while corneal sensitivity and meibomian gland dysfunction (MGD) parameters worsened. In the control group with normal tear-film status, SDE increased significantly after the surgery (p <0.001). There were no statistically significant differences in tear film parameters between the three groups after surgery.

Conclusion

After cataract surgery, patients with mild to moderate dry eyes may experience improved tear film status and reduced symptoms. However, we found no additional beneficial effect on dry eye parameters with treatment with preservative-free dexamethasone, NSAIDs, and lubricants compared to preservative-containing eye drops.

Cord blood-derived biologics lead to robust axonal regeneration in benzalkonium chloride-injured mouse corneas by modulating the Il-17 pathway and neuropeptide Y

BACKGROUND

Umbilical cord blood-derived therapeutics, such as serum (UCS) and platelet-rich plasma (UCPRP), are popular treatment options in clinical trials and can potentially be utilized to address a clinically unmet need caused by preservatives, specifically benzalkonium chloride (BAK), present in ophthalmic formulations. As current clinical interventions for secondary injuries caused by BAK are suboptimal, this study will explore the feasibility of utilizing UCS and UCPRP for cornea treatment and investigate the underlying mechanisms associated with this approach.

METHODS

Mice's corneas were administered BAK to induce damage. UCS and UCPRP were then utilized to attempt to treat the injuries. Ocular tests were performed on the animals to evaluate recovery, while immunostaining, RNA-seq, and subsequent bioinformatics analysis were conducted to investigate the treatment mechanism.

RESULTS

BAK administration led to widespread inflammatory responses in the cornea. Subsequent treatment with UCS and UCPRP led to the downregulation of immune-related 'interactions between cytokine receptors' and 'IL-17 signaling' pathways. Although axonal enhancers such as Ngf, Rac2, Robo2, Srgap1, and Rock2 were found to be present in the injured group, robust axonal regeneration was observed only in the UCS and UCPRP treatment groups. Further analysis revealed that, as compared to normal corneas, inflammation was not restored to pre-injury levels post-treatment. Importantly, Neuropeptide Y (Npy) was also involved in regulating immune responses, indicating neuroimmune axis interactions.

CONCLUSIONS

Cord blood-derived therapeutics are feasible options for overcoming the sustained injuries induced by BAK in the cornea. They also have potential applications in areas where axonal regeneration is required.

Challenging the "Topical Medications-First" Approach to Glaucoma: A Treatment Paradigm in Evolution

Topical glaucoma medications are effective and safe, but they have numerous well-documented limitations that diminish their long-term utility and sustainability. These limitations can include high rates of nonadherence (with associated glaucoma progression), concerning side effects, inconsistent circadian intraocular pressure (IOP) control, complex dosing regimens, difficulty with self-administration, costs, and decreased quality of life. Despite these limitations, topical medications traditionally have been first-line in the glaucoma treatment algorithm, as no other minimally invasive treatment alternatives existed. In recent years, however, novel interventional therapies-including sustained-release drug-delivery platforms, selective laser trabeculoplasty, and micro-invasive glaucoma surgery procedures-have made it possible to intervene earlier without relying on topical medications. As a result, the topical medication-first treatment approach is being reevaluated in an overall shift toward earlier more proactive interventions.

Efficacy and Toxicity Evaluation of Bepotastine Besilate 1.5% Preservative-Free Eye Drops Vs Olopatadine Hydrochloride 0.2% Bak-Preserved Eye Drops in Patients with Allergic Conjunctivitis

Purpose

To study the efficacy and toxic effects of bepotastine besilate 1.5% preservative-free (BB-PF) and olopatadine 0.2% BAK-preserved (OL-BAK) drops on the ocular surface of patients with allergic conjunctivitis.

Patients and Methods

Ninety-seven patients with allergic conjunctivitis diagnosis participated in a prospective, multicenter, randomized, double-blind, controlled, parallel-group clinical trial. Patients received either BB-PF (n=48) or OL-BAK (n=49), both administered once daily in the morning. The patients were followed for 60 days. Ocular itching was the primary outcome measure. Secondary outcomes included ocular symptoms, signs, and non-ocular symptoms associated with rhinoconjunctivitis. Conjunctival impression cytology (CIC) was performed to evaluate histopathological changes related to the toxic effects of preservatives.

Results

BB-PF treatment was associated with a 1.30 more probability of diminished ocular itching than OL-BAK (odds ratio (OR)=1.30; 95% CI=(0.96-1.7); p=0.086). No statistically significant differences were found between treatments in the resolution of other ocular symptoms or signs, except for tearing, which was superior in the BB-PF (OR=1.37; 95% (1.26-1.47); p<0.0001). BB-PF was superior in terms of the resolution of rhinorrhea (p=0.040) and nasal itching (p=0.037). After 60 days of treatment, the BB-PF group exhibited 2.0 times higher probability of having a lower Nelson scale score compared to the OL-BAK group (OR=2.00; 95% CI=(1.19-3.34); p=0.010).

Conclusion

Both medications presented a similar efficacy in terms of the resolution of ocular signs and symptoms associated with ocular conjunctivitis. BB-PF is superior in the resolution of non-ocular symptoms and safer for the ocular surface than OL-BAK.

Ocular surface disease: a known yet overlooked side effect of topical glaucoma therapy

Ocular surface disease (OSD), a disorder affecting the lacrimal and meibomian glands and the corneal and conjunctival epithelium, is a well-known complication of topical glaucoma therapy. OSD can present as a new or pre-existing condition that virtually any anti-glaucoma formulation can exacerbate. As such, both glaucoma and OSD frequently coexist. Typical OSD symptoms include ocular discomfort, redness, burning, and dryness, whereas signs include periorbital and eyelid skin pigmentation, conjunctival scarring, and superficial punctate keratitis. Pressure-lowering eyedrops can cause toxic, allergic, and inflammatory reactions on the ocular surface. The latter can result from either preservatives or direct toxicity from the active molecule. Although usually mild, OSD can cause significant symptoms that lead to poor quality of life, decreased compliance to therapy, glaucoma progression, and worse visual outcomes. Given the chronic nature of glaucoma, lack of curative therapy, and subsequent lifelong treatment, addressing OSD is necessary. This manuscript aims to provide an up-to-date overview of OSD's signs, symptoms, and pathogenic mechanisms from glaucoma therapy toxicity.

Identifying and addressing common contributors to nonadherence with ophthalmic medical therapy

PURPOSE OF REVIEW

To discuss common reasons for nonadherence and review existing and emerging options to reduce nonadherence with ocular medical therapy and optimize therapeutic outcomes.

RECENT FINDINGS

Nonadherence can arise from patient-related issues (e.g. physical, cognitive) and healthcare-related issues (e.g. cost, access to care). Multiple strategies have been developed and evaluated to overcome these barriers to adherence. Identifying nonadherence and its cause(s) facilitates the development of strategies to overcome it.

SUMMARY

Many common causes of nonadherence can be mitigated through a variety of strategies presented.

Norepinephrine as an Enhancer Promoting Corneal Penetration of Riboflavin for Transepithelial Corneal Crosslinking

Purpose

Previously, we found norepinephrine (NE) could affect the corneal epithelial integrity, herein we investigated the feasibility and safety of NE serving as a chemical enhancer to promote corneal penetration of riboflavin during transepithelial corneal crosslinking (CXL).

Methods

The dosage of NE that could promote riboflavin diffusion through the healthy epithelial barrier without inducing epithelial damage in C57BL/6 mice was determined. The safety of NE treatment was confirmed by morphological and histological examinations of the whole cornea. The efficacy of NE in promoting riboflavin penetration was verified by slit lamp and scanning electron microscope (SEM), and corneal biomechanical measurement after CXL. To better fit the clinical scenario, increased NE dosage and shortened riboflavin infiltration time were further evaluated.

Results

The lowest dosage of NE (1 mg/mL) that facilitated transepithelial riboflavin permeation was 2 µL. No visible corneal structure alteration was observed after NE treatment. SEM indicated dissociation of intercellular junctions among corneal epithelial cells. Homogenous distribution of riboflavin throughout corneal stroma was observed. NE-treated corneas reached comparable biomechanical properties after CXL, including stress-relaxation curve and elastic modulus, with corneas treated with the commercially available transepithelial drug Peschke TE. To better fit the clinical scenario, increasing NE up to 5.5 µL helped riboflavin infiltrate the corneal stroma within 30 minutes. After CXL with 9 mW/cm2 ultraviolet-A (UVA) for 2.5 minutes, the cornea showed significantly enhanced corneal biomechanical properties with undisturbed corneal endothelium.

Conclusions

NE serves as an effective enhancer in increasing riboflavin diffusion with limited impairment on corneal epithelium and has great potential for clinical application.

Translation Relevance

NE serves as an effective enhancer for riboflavin penetration and clinical transepithelial CXL.

Benzalkonium Chloride, Even at Low Concentrations, Deteriorates Intracellular Metabolic Capacity in Human Conjunctival Fibroblasts

The objective of this study was to clarify the effects of benzalkonium chloride (BAC) on two-dimensional (2D) and three-dimensional (3D) cultures of human conjunctival fibroblast (HconF) cells, which are in vitro models replicating the epithelial barrier and the stromal supportive functions of the human conjunctiva. The cultured HconF cells were subjected to the following analyses in the absence and presence of 10⁻⁵% or 10⁻⁴% concentrations of BAC; (1) the barrier function of the 2D HconF monolayers, as determined by trans-endothelial electrical resistance (TEER) and FITC dextran permeability, (2) real-time metabolic analysis using an extracellular Seahorse flux analyzer, (3) the size and stiffness of 3D HconF spheroids, and (4) the mRNA expression of genes that encode for extracellular matrix (ECM) molecules including collagen (COL)1, 4 and 6, and fibronectin (FN), α-smooth muscle actin (α-SMA), ER stress related genes including the X-box binding protein-1 (XBP1), the spliced XBP1 (sXBP1) glucose regulator protein (GRP)78, GRP94, and the CCAAT/enhancer-binding protein homologous protein (CHOP), hypoxia inducible factor 1α (HIF1α), and Peroxisome proliferator-activated receptor gamma coactivator 1α (PGC1α). In the presence of BAC, even at low concentrations at 10⁻⁵% or 10⁻⁴%, the maximal respiratory capacity, mitochondrial respiratory reserve, and glycolytic reserve of HconF cells were significantly decreased, although the barrier functions of 2D HconF monolayers, the physical properties of the 3D HconF spheroids, and the mRNA expression of the corresponding genes were not affected. The findings reported herein highlight the fact that BAC, even such low concentrations, may induce unfavorable adverse effects on the cellular metabolic capacity of the human conjunctiva.

A Narrative Review of Ocular Surface Disease Related to Anti-Glaucomatous Medications

Topical anti-glaucomatous medications are still the most important measure to lower intraocular pressure. Large number of studies have confirmed that long-term use of anti-glaucomatous eye drops, especially containing benzalkonium chloride, a preservative, can cause or aggravate ocular surface injury. Ocular surface diseases damage the ocular microenvironmental health status, reduce the patients’ compliance with the treatment, and finally affect the treatment result. Therefore, the ocular surface management of patients with glaucoma is very important. This includes the selection of drugs that are better tolerated according to individual conditions, preservative-free formulations, drugs that protect against ocular surface disease, or selecting surgery and laser treatment, to prevent the damage to the ocular surface by topical anti-glaucomatous drugs.

SCD1-Fatty Acid Desaturase Inhibitor MF-438 Alleviates Latent Inflammation Induced by Preservative-Free Prostaglandin Analog Eye Drops

INTRODUCTION

Prostaglandin analogs are the first line of treatment in patients with glaucoma. Recently, many preservative-free prostaglandin analogs have been marketed to increase their tolerance in chronic use. However, potentially safer formulations have been reported to induce inflammation within ocular surface and adnexa, associated with pronounced activation of tissue macrophages.

AIM

We aimed to evaluate the effect of a Stearoyl-CoA desaturase-1 (SCD1) inhibitor, MF-438, on the differentiation of monocytes exposed to eye drop detergents, representing saturated fatty acid derivatives.

METHODS

A culture of human peripheral blood monocytes was exposed to eye drops containing fatty acid derivatives (eye drop detergents), pf-latanoprost (Monoprost®, hydroxystearate macrogolglycerol - MGHS40) or pf-tafluprost (Taflotan®, polysorbate 80 - PS80), as well as pf-latanoprost+MF-438, MGHS40, and PS80. For the negative control C(-), monocytes were cultured in basal medium, and for the positive controls, monocytes were stimulated with Lipopolysaccharide (LPS) and Interferon γ (IFNγ) (M1 macrophages) or Interleukin-4 (IL-4) (M2 macrophages). The concentration of desaturase in the cell homogenates was determined by ELISA. The number of cells was counted under a microscope at 20x magnification.

RESULTS

The following concentrations of SCD1 (ng/mL) were measured: 7.8±0.3 - pf-latanoprost group; 1.5±0.4 - pf-tafluprost group; 6.8±0.7 - MGHS40 group; 0.4±0.002 - PS80 group; 0.9±0.02 - pf-latanoprost+MF-438 group; 5.4±1.6 - C(-) control; 0.5±0.04 - M1 control; 2.2±0.13 - M2 control. The percentages of macrophages in culture were 33.6%, 17.6%, 33%, 0%, 13.5%, 18.6%, 36.3%, and 39.3% for the pf-latanoprost, pf-tafluprost, MGHS40, PS80, pf-latanoprost+MF-438, C(-), M1, and M2 cultures, respectively. There was a strong correlation between SCD1 concentration and macrophage count in the culture (r=0.8, p<0.05).

CONCLUSION

Inhibition of SCD1 in monocytes prevents their transformation into macrophages after exposure to saturated fatty acid derivatives contained in eye drops, which may contribute to the limitation of latent inflammation within ocular adnexa and could possibly translate into better tolerability of the topical treatment.

Ocular benzalkonium chloride exposure: problems and solutions

Preservatives in multidose formulations of topical ophthalmic medications are crucial for maintaining sterility but can be toxic to the ocular surface. Benzalkonium chloride (BAK)-used in approximately 70% of ophthalmic formulations-is well known to cause cytotoxic damage to conjunctival and corneal epithelial cells, resulting in signs and symptoms of ocular surface disease (OSD) including ocular surface staining, increased tear break-up time, and higher OSD symptom scores. These adverse effects are more problematic with chronic exposure, as in lifetime therapy for glaucoma, but can also manifest after exposure as brief as seven days. Multiple strategies are available to minimize or eliminate BAK exposure, among them alternative preservatives, preservative-free formulations including sustained release drug delivery platforms, and non-pharmacological therapies for common eye diseases and conditions. In this paper, we review the cytotoxic and clinical effects of BAK on the ocular surface and discuss existing and emerging options for ocular disease management that can minimize or eliminate BAK exposure.

Efficacy and safety of newly developed preservative-free latanoprost 0.005% eye drops versus preserved latanoprost 0.005% in open angle glaucoma and ocular hypertension: 12-week results of a randomized, multicenter, controlled phase III trial

AIM

To evaluate the therapeutic efficacy, safety and tolerability of newly developed preservative-free (PF) latanoprost generic [TJO-002] and compare it with benzalkonium chloride (BAK)-preserved latanoprost [Xalatan^®] in patients with primary open angle glaucoma (POAG) and ocular hypertension (OHT).

METHODS

Included patients were aged ≥19y with POAG/OHT. After a washout period, patients with IOP 21-35 mm Hg at 9 a.m. were enrolled. After a full ophthalmic and glaucoma examination, 144 patients with POAG and OHT participated in this study. Subjects were randomly assigned either PF latanoprost (74 eyes) or BAK-preserved latanoprost (70 eyes). All subjects were examined at 4, 8, and 12wk after first administration. At each follow-up visit, IOP was measured at 9 a.m. and 5 p.m. and compliance was assessed. Throughout the study, all adverse events were recorded and monitored by the masked investigators who measured IOP.

RESULTS

Both groups showed a statistically significant decrease of average diurnal IOP at 12wk compared to baseline (-7.21±3.10 mm Hg in the PF latanoprost group and -7.02±3.17 mm Hg in the BAK latanoprost group, both P<0.0001). There was no statistically significant diurnal IOP variation between the groups. In terms of tolerability, pruritus, burning/stinging, and sticky eye sensation, severity was significantly lower in the PF latanoprost group than in the BAK latanoprost group (P<0.05).

CONCLUSION

PF latanoprost has at least similar efficacy in terms of IOP reduction and better tolerability compared with BAK latanoprost.

Benzalkonium Chloride-Preserved Anti-Glaucomatous Eye Drops and Their Effect on Human Conjunctival Goblet Cells in vitro

Introduction

Most intraocular pressure (IOP)-lowering eye drops are preserved with benzalkonium chloride (BAK). This can increase side effects and decrease adherence. Particularly, damage to the mucin-producing conjunctival goblet cells may be an issue due to instability of the tear film. We aimed to investigate the effect of IOP-lowering eye drops preserved with BAK on cultured human conjunctival goblet cells.

Methods

Eye drops Brimonidine Tartrate Teva (BT) with 0.005% BAK, Dorzolamide Stada (DS) with 0.0075% BAK, Optimol^® (OP) with 0.01% BAK, and Latanoprost Teva (LT) with 0.02% BAK were included. Human primary cultured goblet cell survival was evaluated using a lactate dehydrogenase assay on human goblet cells after treatment for 30 min and 6 h with the different anti-glaucoma drug formulations.

Results

All eye drops examined, except BT, reduced goblet cell survival. The impact of eye drops on goblet cell viability was correlated with the time of exposure as well as to the concentration of BAK. After 30 min of exposure, cell viability was 93% for BT (0.005% BAK; p = 0.93), 71% for DS (0.0075% BAK; p = 0.067), 70% for OP (0.01% BAK; p = 0.054), and 69% for LT (0.02% BAK; p = 0.022), and exposure for 6 h reduced cell survival to 74% for BT (p = 0.217), 52% for DS (p = 0.011), 34% for OP (p = 0.017), and 31% for LT (p = 0.0007).

Conclusion

LT, OP, and DS reduced human goblet cell survival in a time-dependent manner. BT did not affect goblet cell survival. Cell survival was correlated with the BAK concentration in the eye drops making 0.02% BAK-preserved LT most toxic and 0.005% BAK-preserved BT least toxic. Based on the present study, decreasing BAK in eye drops for chronic use seems important to reduce damage to the goblet cells. However, future studies are needed to further explore this finding.

Comparison of BAK-preserved latanoprost and polyquad-preserved travoprost on ocular surface parameters in patients with glaucoma and ocular hypertension

BACKGROUND

To compare the effect of two different prostaglandin analogues (Travatan® vs. Xalatan®) on ocular surface parameters.

METHODS

This study includes 44 eyes of 44 patients with newly diagnosed primary open-angle glaucoma (POAG) or ocular hypertension (OHT). Patients were randomly divided into two groups and treated with either benzalkonium chloride (BAK)-preserved latanoprost and polyquad-preserved travoprost. Changes in intraocular pressure (IOP) levels and ocular surface parameters including ocular surface disease index (OSDI) questionnaire, tear breakup time (TBUT), ocular surface staining scores, and Schirmer test scores of patients were performed at baseline, 1, 3, 6, and 12 months of treatment and compared.

RESULTS

The age, sex ratio, visual acuity, central corneal thickness, and cup/disc ratio were similar between the groups. A decrease in IOP levels (23.3 ± 2.5 to 15.5 ± 2.3), TBUT (5.5 ± 2.3 to 4.1 ± 1.7 s), Schirmer test values (11.3 ± 5.9 to 8.6 ± 4.7 s), and a worsening in OSDI scores (44.6 ± 15.2 to 55.1 ± 13.1) and staining scores (1.7 ± 1.6 to 2.3 ± 1.8) were observed in all patients in the first month of treatment (p < 0.05, for all). No further worsening was detected during the 1-year follow-up. There was no difference between the groups in terms of alterations in IOP levels and ocular surface parameters.

CONCLUSION

Travatan® and Xalatan® have a similar effect on IOP levels and ocular surface parameters in patients with POAG and OHT.

Comparison of the Safety and Efficacy between Preserved and Preservative-Free Latanoprost and Preservative-Free Tafluprost

In this study, we investigated the effect of preservative-free (PF) 0.0015% tafluprost (TA), to the preservative containing (PC) and the PF 0.005% latanoprost (LA) in Korean subjects. This study was conducted as a multi-center, randomized, investigator-blind, active controlled, parallel-group, clinical trial in adult patients (≥19 years) with open-angle glaucoma (OAG) and ocular hypertension (OHT). After a washout period, patients with an IOP between 15 and 35 mmHg were enrolled and evaluated the efficacy, safety, and compliance at 4, 8 and 12 weeks after the first administration. A total of 137 OAG and OHT patients were randomized. Statistically significant reductions in IOP were observed in all groups. Twelve weeks after each eye drop instillation, the mean IOP reduction was −4.59 ± 2.70 mmHg (−24.57 ± 13.49%) in the PC-LA group, −4.52 ± 2.17 mmHg (−24.41 ± 11.38%) in the PF-LA, and −3.14 ± 2.83 mmHg (−17.22 ± 14.57%) in the PF-TA group. The PF-LA showed significantly better responsiveness than did PF-TA. PF-LA was better tolerated than was PC-LA. There were no adverse events that led to cessation of eye drop use in any of the groups. In conclusion, IOP decreased similarly across the groups. PF-LA may provide a good choice for OAG patients with ocular surface diseases.

Comparison of preserved bimatoprost 0.01% with preservative-free tafluprost: A randomised, investigator-masked, 3-month crossover, multicentre trial, SPORT II

IMPORTANCE

This study compares the efficacy and tolerability of a preservative-free prostaglandin analogue (tafluprost 15 mg/ml) to a prostaglandin analogue that uses 0.02% of benzalkonium chloride (bimatoprost 0.1 mg/ml).

BACKGROUND

Different prostaglandin analogues have been commercially approved, with differences in tolerability.

DESIGN

Prospective, randomised, investigator-masked, 3-month crossover, multicentre trial.

PARTICIPANTS

Sixty-four patients with ocular hypertension or open-angle glaucoma were randomised to two groups, after a 4-week washout period from their current topical drop regimen.

METHODS

Participants were randomised to tafluprost (Group 1; n = 33) or bimatoprost (Group 2; n = 31). At month 3, each group switched to the opposite treatment. IOP was evaluated at multiple timepoints.

MAIN OUTCOME MEASURES

The primary outcome was difference in mean IOP between the two groups at the final visit. Secondary outcomes included change from baseline IOP at month 3 and month 6, difference in mean IOP at month 3 and difference in IOP at all timepoints. Safety outcomes included best-corrected visual acuity (BCVA), adverse events, ocular tolerability, optic nerve assessment and slit lamp biomicroscopy.

RESULTS

Both medications significantly lowered IOP at month 6 compared to baseline: 5.4 mmHg (27%) for tafluprost and 6.8 mmHg (33%) for bimatoprost (p < 0.0001). No significant differences in any of the safety measures (including conjunctival hypearemia) were detected.

CONCLUSIONS AND RELEVANCE

Bimatoprost produced a statistically significant greater IOP reduction compared to tafluprost with minimal to no difference in side effects. This should be borne in mind when weighing up the pros and cons of preserved versus preservative-free prostaglandin analogue therapy.

CLINICALTRIALS.GOV IDENTIFIER

NCT02471105.

Comparison of the Intraocular Pressure-Lowering Effect and Safety of Preservative-Free And Preservative-Containing Brimonidine/Timolol Fixed-Combination Ophthalmic Solutions in Patients with Open-Angle Glaucoma

Purpose: To compare the therapeutic efficacy and safety of newly developed preservative-free (PF) brimonidine/timolol fixed-combination (BTFC) ophthalmic solutions and a preservative-containing (PC) BTFC ophthalmic solution in patients with open-angle glaucoma.Methods: This study was conducted as a multicenter, randomized, open-label, parallel-group clinical trial to evaluate the efficacy and safety of PF BTFC as compared with PC BTFC in adult patients (aged ≥ 19 years) with open-angle glaucoma (OAG) and ocular hypertension (OHT). A total of the 106 patients were enrolled, with 53 patients each randomized to the two treatment groups and included in the analysis of the safety set (SS).After a washout period, patients with an IOP below 35 mmHg at 9 a.m. were enrolled. After a full ophthalmic and glaucoma examination, a total of 106 OAG and OHT patients were randomized to the PF group or PC group.All subjects were examined 4 and 12 weeks after first administration. At each follow-up visit, IOP was measured at 9 a.m. and 11 a.m. and the efficacy, safety, and compliance were evaluated. Throughout the study, all adverse events were recorded and monitored by the investigators.Results The mean IOP changes from baseline to 12 weeks at 11:00 a.m. were -3.45 ± 2.53 mmHg in the PF group and -3.65 ± 2.76 mmHg in the PC group (p < .0001 for both). The difference in mean IOP change between the two groups was 0.20 ± 2.65 mmHg, which was not significantly different. The proportion of patients with IOP reductions of ≥ 15% and ≥ 20% and IOP at all-time points in the PF group were not significantly different when compared with in the PC group. There were no specific differences between the two groups regarding the incidence of adverse events.Conclusions PF BTFC ophthalmic solution shows a similar efficacy and safety profile to that of PC BTFC.

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

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

Shape Memory Tube Plug for Fine-control of Intraocular Pressure by Glaucoma Devices

As a standard approach to treating glaucoma, a silicone tube device is inserted into the eye to drain water and thereby lower the intraocular pressure (IOP). However, the fixed diameter of the tube often results in too much initial water drain. Suture-sheaving of the outer tube wall also leads to random IOP drops over time. In this study, self-expansion of the inner tube diameter was achieved by inserting a shape memory tube into the silicone tube. The difference in controlling small to large IOP drops before and after tube diameter expansion was demonstrated via computational modeling, a flow pumping system, and rabbit experiments.

Effects of Benzalkonium Chloride and Preservative-Free Composition on the Corneal Epithelium Cells

Purpose: Benzalkonium Chloride (BAK) is reported to have the potential to damage the cornea. We developed a composition with broad-spectrum antimicrobial activity without preservatives by combining trometamol, boric acid, and ethylenediaminetetraacetic acid (TBE). This study aimed at evaluating the corneal damage caused by TBE and comparing it with that caused by BAK. Methods: SV40-immortalized human corneal epithelial cell line (HCE-T) was treated with BAK or TBE, and the cell viability was measured. The exposure time that caused 50% cell death (CDT₅₀) was calculated. Transepithelial electrical resistance (TEER) was measured before and after treatment with BAK or TBE. Occludin was detected with immunostaining and Western blotting after treatment with BAK or TBE. The effect of BAK or TBE on membrane-associated mucins was evaluated with rose bengal (RB) staining. Results: In the BAK group, cell viability decreased in a dose-dependent manner. The viability of the TBE group was significantly greater than that of the BAK group. The CDT₅₀ of the TBE group is greater than that of the BAK groups. In the BAK groups, the recovery of TEER was delayed in a dose-dependent manner, whereas in the TBE group, the recovery occurred earlier. Localization of occludin was disrupted, and the amount of occludin was significantly reduced among the cells exposed to BAK. The area stained with RB in the BAK groups increased, whereas that in the TBE group did not increase. Conclusion: These results suggest that the application of TBE would be useful for developing preservative-free ophthalmic preparations that offer both sufficient safety and antimicrobial activity.

Meibomian gland dropout rate as a method to assess meibomian gland morphologic changes during use of preservative-containing or preservative-free topical prostaglandin analogues

PURPOSE

To investigate the usefulness of meibomian gland (MG) dropout rate in the evaluation of MG morphological change associated with the use of prostaglandin for glaucoma treatment through the association between MG and the ocular surface parameters and medication duration and presence of preservative.

METHODS

This cross-sectional study was conducted on 88 eyes of 88 patients who were diagnosed with glaucoma and used only Tafluprost as treatment. The patients were divided into four "user" groups: 1) 23 patients used preservative-free (PF) Tafluprost for 6 months; 2) 21 patients used preservative-containing (PC) Tafluprost for 6 months; 3) 23 patients used PF-Tafluprost for 24 months; 4) 21 patients used PC-Tafluprost for 24 months. Ocular surface parameters and the MG condition, including MG dropout rate and meiboscale, were evaluated. Multiple regression was used to identify associations.

RESULTS

There were significant differences in age (p = 0.003), tear breakup time (p = 0.016), lid margin abnormality (p = 0.016), expressibility (p = 0.039), meiboscale (p<0.001), and MG dropout rate (p<0.001) among the 4 groups. MG dropout rate and meiboscale showed significant differences in all post hoc analyses, except for the comparison between the PF-Tafluprost and PC-Tafluprost 6-month user groups. Medication duration, preservative status, and meiboscale were significantly correlated with MG dropout rate (p<0.001, p = 0.024, p<0.001, respectively). In the 6-month user group, preservative status significantly correlated with MG dropout rate (p = 0.015). However, in the 24-month user group, meiboscale was the only parameter significantly associated with MG dropout rate (p<0.001).

CONCLUSION

MG dropout rate in patients using Tafluprost showed a significant correlation with medication duration and preservative status. This result indicates MG dropout rate reflects MG morphologic change associated with prostaglandin.

Tear biomarkers in latanoprost and bimatoprost treated eyes

Purpose

Prostaglandin analogues (PGA’s) are the mainstay and first line of treatment in current glaucoma practise. Though latanoprost and bimatoprost are the most commonly used PGA’s with minimal side effects at lower concentrations like bimaotoprost 0.01%, direct comparison of their cytokine/MMP profile in tears has not been evaluated earlier. The study intends to ascribe PGA to the upregulation of MMPs, Cytokines and Chemokines mediating varied pathways to result in side effects of the drugs.

Methods

Tear sample collection was done from outer canthus of 30 eyes of 30 patients (primary open angle glaucoma (n = 26 and n’ = 20), normal tension glaucoma (n = 4 and n’ = 10), in latanoprost (n) 0.005% and bimatoprost (n’) 0.01% group respectively, with a mean age of 62±10.5 years) on >6 months of PGA use using Tear flo^TM Schirmer filter strip. Tear samples from 30 eyes of 30 cataract patients without drug treatment were used as the control. Gelatinolytic activity of MMP-9 and MMP-2 were examined by substrate gelatine zymography MMP-1 and TIMP-1 concentrations from tears samples with PGAs were evaluated by ELISA while cytokine concentration in the eluted tears was evaluated using a convenient bioplex kit assay (Milliplex MAP kit, HCYTMAG-60K-PX41, Millipore, Massachusetts, United States). The mean duration of use of PGA in both groups did not differ significantly (median 1.3 years in bimatoprost and 1.1 years in latanoprost eyes, p = 0.6).

Results

The tear MMP-9 expression was higher in eyes receiving latanoprost while the MMP-2 expression was higher in eyes receiving bimatoprost with MMP1 protein levels being higher in the former. Latanoprost treated eyes had marginally elevated tear cytokines involved in tissue remodelling while bimatoprost eyes showed elevated cytokines regulating allergic pathways.

Conclusion

Differential cytokine and MMP expression indicates differential signalling pathways mediating different cellular effects (evident as clinical and side effects) with the two drugs which can be explored further.

Comparison of Efficacy and Ocular Surface Disease Index Score between Bimatoprost, Latanoprost, Travoprost, and Tafluprost in Glaucoma Patients

Aim

The purpose of this study is to evaluate and compare the efficacy of 4 prostaglandin analogues (PGAs) and to determine the incidence of ocular surface disease in newly diagnosed, primary open-angle glaucoma (POAG) patients started on one of those 4 PGAs: bimatoprost (benzalkonium chloride, BAK, 0.3 mg/mL), latanoprost (BAK 0.2 mg/mL), travoprost (polyquad), and tafluprost (BAK-free).

Patients and Methods

In this single-center, open-label trial, 32 patients newly diagnosed with POAG were randomly started on one of the four PGAs. All patients underwent a complete ophthalmological exam at presentation and at 1, 3, and 6 months of follow-up. Dry eye disease (DED) was assessed using the original Ocular Surface Disease Index (OSDI) questionnaire, in order to evaluate the impact of the drops on the quality of life of patients.

Results

The mean age was 60.06 years ± 11.76. All four drugs equally and significantly reduced the intraocular pressure (IOP) with respect to the baseline IOP. There was a trend for a slightly greater reduction of IOP with bimatoprost, but the difference was not found to be statistically significant when compared to other PGAs. OSDI scores were significantly superior for travoprost (10.68 ± 5.73) compared to the other three drugs (p < 0.05). Latanoprost caused the most significant eyelash growth and iris discoloration. Conjunctival hyperemia and superficial keratitis occurrence were similar in the four groups.

Conclusion

All prostaglandin analogues equally and significantly reduce the IOP in patients with POAG. According to the results of the OSDI score, latanoprost seems to be the least tolerated among the four drugs.

Association between meibomian gland dysfunction and compliance of topical prostaglandin analogs in patients with normal tension glaucoma

PURPOSE

The aim of this study was to investigate the association between tear film and meibomian gland parameters in patients with normal tension glaucoma (NTG), who underwent topical prostaglandin analog (PGA) monotherapy, and medication compliance.

METHODS

Ocular surface disease index (OSDI), Schirmer's test, tear film break-up time (TBUT), keratoepitheliopathy (KEP) score with fluorescein, and meibomian gland parameters were assessed in 45 eyes of 45 patients with NTG (NTG group), who received topical PGA monotherapy for more than 1 year. The results were compared to those of 40 eyes of 40 normal subjects (control group). Medication compliance was assessed by an 8-item Morisky Medication Adherence Scale (MMAS-8). Multiple logistic regression analysis was used to identify the factors associated with medication compliance.

RESULTS

There was a significant difference in OSDI (P = 0.043), Schirmer's test (P < 0.001), TBUT (P < 0.001), KEP score (P = 0.015) and all meibomian gland parameters (all P < 0.001) between two groups. When the NTG group was divided into compliant and non-compliant groups based on the scores of MMAS-8, 30 (75%) patients were classified into the compliant group. Multiple logistic regression analysis revealed that the lid margin score (OR, 0.256; 95% CI, 0.072-0.908, P = 0.035), meibum score (OR, 0.144; 95% CI, 0.023-0.915, P = 0.04), and meibo score (OR, 0.344; 95% CI, 0.140-0.845, P = 0.02) were significant factors associated with compliance in patients with NTG. The meibomian gland parameters showed a negative correlation with medication compliance (all P < 0.005).

CONCLUSIONS

Malfunction of the meibomian glands can be an important clinical finding associated with compliance of PGA monotherapy in patients with NTG.

Herbal Supplement in a Buffer for Dry Eye Syndrome Treatment

Dry eye syndrome (DES) is one of the most common types of ocular diseases. There is a major need to treat DES in a simple yet efficient way. Artificial tears (AT) are the most commonly used agents for treating DES, but are not very effective. Herbal extractions of ferulic acid (FA), an anti-oxidant agent, and kaempferol (KM), an anti-inflammatory reagent, were added to buffer solution (BS) to replace ATs for DES treatment. The cytotoxicity and anti-inflammatory effects were examined in vitro by co-culture with human corneal epithelial cells (HCECs) to obtain the optimal concentration of KM and FA for treating HCECs. Physical properties of BS, such as pH value, osmolality, and refractive index were also examined. Then, rabbits with DES were used for therapeutic evaluation. Tear production, corneal damage, and ocular irritation in rabbits’ eyes were examined. The non-toxic concentrations of KM and FA for HCEC cultivation over 3 days were 1 µM and 100 µM, respectively. Live/dead stain results also show non-toxicity of KM and FA for treating HCECs. Lipopolysaccharide-stimulated HCECs in inflammatory conditions treated with 100 µM FA and 1 µM KM (FA100/KM1) showed lower IL-1B, IL-6, IL-8, and TNFα expression when examined by real-time PCR. The BS with FA100/KM1 had neutral pH, and a similar osmolality and refractive index to human tears. Topical delivery of BS + FA100/KM1 showed no irritation to rabbit eyes. The corneal thickness in the BS + FA100/KM1 treated group was comparable to normal eyes. Results of DES rabbits treated with BS + FA100/KM1 showed less corneal epithelial damage and higher tear volume than the normal group. In conclusion, we showed that the combination of FA (100 µM) and KM (1 µM) towards treating inflamed HCECs had an anti-inflammatory effect, and it is effective in treating DES rabbits when BS is added in combination with these two herbal supplements and used as a topical eye drop.

N-hydroxymethylglycinate with EDTA is an efficient eye drop preservative with very low toxicity: an in vitro comparative study

PURPOSE

Preservatives are used in multi-dose ophthalmic topical medications in order to prevent contamination by bacteria and fungi. However, prolonged use of preserved eye drops, as it may happen in dry eye or glaucoma, may damage cells of the ocular surface. Therefore, an important goal is to find preservatives with low toxicity which are mild to host cells, still able to prevent drug contamination so to maintain their sterility and efficacy. Hence, aim of this study has been to compare the relative toxicity on a rabbit corneal cell line of a new preservative, made by the association of N-hydroxy-methyl-glycinate (NIG) with disodium-ethylene diamine tetra-acetate (EDTA), with other known and widely used eye-drops preservatives.

MATERIALS AND METHODS

Rabbit corneal cells (SIRC) were tested either in 96-well plates or in suspension culture. Treatments with preservatives (used at known bacteriostatic concentrations) included: benzalkonium chloride (BAK), polyquaternium-1 (PQ-1), sodium perborate (SP: NaBO_{3 *} H₂O), and NIG ± EDTA at different concentrations (0.001% and 0.002%), and different treatment times (from 30 minutes to 120 hours). At the end of treatment, cell survival was evaluated by a specific spectrophotometric method through the metabolic conversion of MTT [3-(4,5-dimethylthiazol-2-yl) 2, 5-diphenyltetrazolium bromide] into formazan crystals.

RESULTS

Almost no cell toxicity was evident for NIG and SP at either concentration (0.001% or 0.002%), while a low toxicity was observed for PQ-1 (62% at the highest dose at 120 hours). BAK, as expected, showed the highest toxicity (60-80% at 30 minutes, and over 90% from eight hours onward). EDTA 0.1% alone or in combination with NIG 0.002%, showed no toxicity at 24 hours, and even resulted in cell growth promotion (46% and 38%, respectively), after 48 hours of treatment.

CONCLUSIONS

These data show that the new preservative NIG/EDTA, at doses known to have effective antimicrobial properties, has a very low toxicity on corneal cells, and so it can be safely used in multi-dose eye drops.

A Comparison of the Effects of Benzalkonium Chloride on Ocular Surfaces between C57BL/6 and BALB/c Mice

Models of benzalkonium chloride (BAC)-induced ocular disruption have been created and are widely used in various animals. This study aimed to compare the effects of BAC on the ocular surfaces of C57BL/6 and BALB/c mice. C57BL/6 and BALB/c mice were treated separately with BAC eye-drops at different concentrations. Eyes were evaluated by scoring epithelial disruption, corneal opacity and neovascularization in vivo, and by histological assays with hematoxylin/eosin (H/E) and periodic acid-Schiff stainings and by determining the expression of inflammatory factors in vitro on Days 7 and 14. The in vivo corneal epithelial disruption, corneal edema/opacity and neovascularization, which were in accordance with the results of the H/E staining and peaked at Day 7, were observed in a dose-dependent manner in the BAC-treated mice, with more severe signs in the C57BL/6 mice than the BALB/c mice. The loss of conjunctival goblet cells in the conjunctivas and the increasing expression of monocyte chemoattractant protein 1 (MCP-1), growth-regulated protein alpha (GROa) and macrophage inflammatory protein-1 alpha (MIP-1a) in the corneas were found in a dose-dependent manner in both strains of mice. Topical application of BAC can dramatically disrupt the ocular surfaces of C57BL/6 and BALB/c mice, and the disruptions were much more severe in the C57BL/6 mice that received high doses of BAC.