Multipurpose Contact Lens Solutions Research Articles

Physical properties of soft contact lens multipurpose solutions commercially available in Ghana

PurposeTo investigate the physical properties of commercially available multipurpose soft contact lens solutions in Ghana. MethodspH (Kelilong ICL-099 pH meter, China), osmolality (OSMOMAT 3000, GONOTEC, Germany), surface tension (Sigma 700 Tensiometer, Sweden), and viscosity (CFOC-200 Viscometer, Cannon Company, USA) of various soft contact lens multipurpose solutions (MPS) were measured in triplicates at room temperature. Viscosity measurements were also taken at 34 °C ocular surface temperature. The solutions examined were Opti-Free Replenish (OFR), Trufresh (TF), Avizor (AV), Freshlook (FL), and Refresh (RF). ResultsSeveral solutions were largely hypo-osmotic in the range of 108–231 mOsm/kg, the exception being Avizor, which had osmolality values that were closer to human tears (301 ± 0.58 mOsm/kg). The range of pH values of the solutions (6.33–8.24, mean (SD) = 7.53 ± 0.18) fell within the reported tolerable range for the ocular surface (6.20–9.00). Surface tension values ranged from 35.86 to 42.27 mNm with a mean of 38.49 ± 2.32 mNm. The average viscosity of most solutions at room temperature (25 °C) was 1.44 ± 0.49 cP with a range of 1.04–2.15 cP. Significantly lower values ranging from 0.79 to 1.58 cP were obtained at ocular surface temperature (34 °C), p = 0.0001). ConclusionsThe physical properties of many of the solutions used as MPS in Ghana are markedly variable. Nevertheless, pH, surface tension, and viscosity fall within the acceptable limits of ocular physiological tolerance; except for osmolality, which majority were outside the reported tolerable range for the ocular surface. This information may partly explain the reason some patients exhibit strong preferences for certain care systems and should aid clinical decision-making when prescribing eye care systems to patients.

Could giant viruses be considered as a biotechnological tool for preventing and controlling Acanthamoeba infections?

The aim of the study was to evaluate the efficiency of mimivirus as a potential therapeutic and prophylactic tool against Acanthamoeba castellanii, the etiological agent of Acanthamoeba keratitis, a progressive corneal infection, that is commonly associated with the use of contact lenses and can lead to blindness if not properly treated. Mimivirus particles were tested in different multiplicity of infection, along with commercial multipurpose contact lenses' solutions, aiming to assess their ability to prevent encystment and excystment of A. castellanii. Solutions were evaluated for their amoebicidal potential and cytotoxicity in MDCK cells, as well as their effectiveness in preventing A. castellanii damage in Madin-Darby canine kidney (MDCK) cells. Results indicated that mimivirus was able to inhibit the formation of A. castellanii cysts, even in the presence of Neff encystment solution. Mimivirus also showed greater effectiveness in controlling A. castellanii excystment compared to commercial solutions. Additionally, mimivirus solution was more effective in preventing damage caused by A. castellanii, presented greater amoebicidal activity, and were less cytotoxic to MDCK cells than commercial MPS. Mimivirus demonstrates a greater ability to inhibit A. castellanii encystment and excystment compared to commercial multipurpose contact lens solutions. Additionally, mimivirus is less toxic to MDCK cells than those commercial solutions. New studies utilizing in vivo models will be crucial for confirming safety and efficacy parameters.

Activity of multipurpose contact lens solutions against Staphylococcus aureus, Pseudomonas aeruginosa, Serratia marcescens and Candida albicans biofilms.

The use of contact lenses has progressively increased around the world, thereby increasing the risk of complications. The most serious complication is microbial keratitis (corneal infection) that can progress to a corneal ulcer. Fourteen multipurpose contact lens solutions were tested on mature biofilms comprising Staphylococcus aureus, Pseudomonas aeruginosa, Serratia marcescens and Candida albicans, using the minimum disinfection times recommended by the manufacturers. The biofilm was induced in the lens case, and 24 h later, the solutions were added. Activity against planktonic and sessile cells was evaluated and quantified as colony forming units per millilitre. The minimum concentration for biofilm eradication was defined as a 99.9% reduction in viable cells. Although most solutions exhibited activity against planktonic cells, only five of the 14 solutions produced a significant reduction in the S. marcescens biofilm. No solution achieved the minimal biofilm eradication of S. aureus, P. aeruginosa and C. albicans. Multipurpose contact lens solutions provide greater bactericidal and/or fungicidal activity on planktonic cells than biofilms. The minimal eradication biofilm concentration was only achieved for S. marcescens.

Antimicrobial Activity Comparison of Multipurpose Solutions

Purpose: This study compares the antimicrobial activity of seven multipurpose contact lens multipurpose solutions (MPS) available in European markets by microbiological test methods ISO 14729 and ISO 18259.

Cytotoxicities and wound healing effects of contact lens multipurpose solution on human corneal epithelial cell

ABSTRACT Clinical Relevance Contact lens multipurpose solutions (MPSs) contain several components that have the potential to cause corneal epithelial cell toxicity. Evaluating the components and the toxic effect of MPS should be considered for effective eye care. Background The cytotoxic and wound healing effects of five commercially available MPSs on human corneal epithelial cells (HCECs) are is investigated. Methods The following commercially available MPSs were used: Queen’s PLURISOL®, Frenz®, Boston SIMPLUS®, DL+PLUS EYE® (DL), and NEW YORK DEFINE® (NY). The proliferation of HCECs exposed to each MPS for 1, 6, and 24 h and the cytotoxicity of these solutions were analyzed using methyl thiazolyl tetrazolium-based colorimetric and lactate dehydrogenase leakage assays, respectively. The cellular morphology was evaluated by inverted phase-contrast and electron microscopy. A scratch-wound assay was performed to measure wound widths 24 h after confluent HCEC monolayers were scratch-wounded. Results The tested MPS had a time-dependent inhibitory effect on HCEC proliferation and cytotoxicity, significantly at 24 h after exposure (p< 0.05 in all MPSs). HCECs exposed to MPS detached from the bottom of the culture dishes, showed degenerative changes such as loss of microvilli, cytoplasmic vacuole formation and nuclear condensation, and decreased wound healing, compared to the controls (p< 0.001 in Boston, DL and NY). Among the tested MPS, DL and NY were more cytotoxic and showed less wound healing. Conclusion MPS has a toxic effect on HCECs, which is dependent on the concentration of the disinfecting component. Since the components that constitute the MPS are absorbed and retained in the lens, cautious scrutiny of the concentration and attention to lens cleaning are warranted to mitigate the related cytotoxicity.

Common Ophthalmic Preservatives in Soft Contact Lens Care Products: Benefits, Complications, and a Comparison to Non-Preserved Solutions.

PurposePreservatives are essential for preventing contact lens (CL)-related microbial keratitis (MK). The purpose of this review is to summarize the current knowledge related to the use of common ophthalmic preservatives in CL care products with respect to both safety and efficacy.MethodsManuscripts written in English were obtained by searching PubMed.gov with the term contact lens plus antimicrobial, benzalkonium chloride, biguanide, Aldox, polyquaternium, preservative, thimerosal, EDTA (ethylenediaminetetraacetic acid), chlorhexidine, or blister pack.ResultsThis review found that first-generation preservatives are no longer used in CL multipurpose solutions (MPS) due to their high levels of ocular toxicity. Modern, high-molecular-weight preservatives, including polyquaternium-1 (PQ-1) and biguanides (PHMB), are generally effective against bacteria, minimally effective against fungi, and not effective against Acanthamoeba. PQ-1 and PHMB are likely safe when used with CLs, but they may cause ocular adverse events, with roughly equal risk between the two preservatives. Some CL MPS contain both PQ-1 and PHMB, but no increased risk of adverse events has been reported when combining the two. Hydrogen-peroxide (H2O2) solutions are effective against all common ocular microbes, including Acanthamoeba, and they have been proven safe with proper compliance. Povidone-iodine (P-I) solutions are not currently commercially available in North America, but they have been shown in other countries to be safe and effective.ConclusionPatients should be monitored when using PQ-1 or PHMB-containing solutions since they have been associated with ocular adverse events. If events are detected, patients should be switched to an alternative solution. H2O2 or P-I solutions are preferred for any patient who may expose their CLs to water because they are the only solution categories effective against Acanthamoeba.

Fast versus gradual adaptation of soft monthly contact lenses in neophyte wearers

AimTo determine if a gradual adaptation period is necessary for neophytes when fitted with modern hydrogel or silicone hydrogel reusable disposable contact lenses. MethodAcross four sites, 74 neophytes (18–28 years) were randomly assigned to a reusable lens cleaned nightly with Opti-Free® Puremoist® multi-purpose contact lens solution: Proclear® (hydrogel) or Biofinity® (silicone hydrogel) and an adaptation schedule: fast (10 h wear from the first day) or gradual (4 h on the first day, increasing their wear time by 2 h on each subsequent day until they had reached 10 h). Masked investigators graded ocular surface physiology and non-invasive tear breakup time (NIBUT) and a range of comfort, vision and lens handling subjective ratings (0–100 visual analogue scales) were recorded at the baseline visit and after 10 h of lens wear, 4–6 days and 12–14 days after lens fitting. Subjective scores were also repeated after 7 days. ResultsThere was no difference (p > 0.05) in ocular surface physiology or NIBUT between fast and gradual adaptation groups at any time point in either lens type with the exception of increased corneal staining (p = 0.019) in the silicone hydrogel fast adaptation group after 4–6 days, but was similar by 12–14 days. Subjective scores were also similar across the visits and lens types with the exception of ‘lens awareness’ (p = 0.019) which was less in the gradual versus the fast adaptation silicone hydrogel lens group at 12–14 days. ConclusionThere seems to be no clinical benefit for recommending a gradual adaptation period in new wearers fitted with modern soft reusable disposable contact lenses. The findings of this work add to a growing body of evidence suggesting that such advice is unnecessary in regular soft contact lens wear, which has important ramifications for the initial clinical management of these patients.

Silver Nanoparticles Conjugated with Contact Lens Solutions May Reduce the Risk of Acanthamoeba Keratitis.

Acanthamoeba keratitis (AK), a severe sight-threatening corneal infection, has become a significant medical problem, especially among contact lens wearers. The disease manifests as eye pain, congestion, blurred vision, lachrymation, and ring-shaped infiltrates of the cornea, and can lead to permanent blindness. Inappropriate habits of contact lens users may result in an increased risk of AK infection. The anti-amoebic efficiency of popular multipurpose contact lens solutions is insufficient to reduce this risk. An effective and non-toxic therapy against AK has not yet been developed. The prevention of AK is crucial to reduce the number of AK infections. Nanoparticles are known to be active agents against bacteria, viruses, and fungi and were also recently tested against protozoa, including Acanthamoeba spp. In our previous studies, we proved the anti-amoebic and anti-adhesive activity of silver nanoparticles against Acanthamoeba castellanii. The aim of this study is to evaluate the activity, cytotoxicity, and anti-adhesive properties of silver nanoparticles conjugated with five commonly used multipurpose contact lens solutions against the Acanthamoeba castellanii NEFF strain. The obtained results show a significant increase in anti-amoebic activity, without increasing the overall cytotoxicity, of Solo Care Aqua and Opti Free conjugated with nanoparticles. The adhesion of Acanthamoeba trophozoites to the contact lens surface is also significantly reduced. We conclude that low concentrations of silver nanoparticles can be used as an ingredient in contact lens solutions to decrease the risk of Acanthamoeba keratitis infection.

Tannic acid-modified silver nanoparticles enhance the anti-Acanthamoeba activity of three multipurpose contact lens solutions without increasing their cytotoxicity

BackgroundFree-living amoebae of the genus Acanthamoeba are cosmopolitan, widely distributed protozoans that cause a severe, vision-threatening corneal infection known as Acanthamoeba keratitis (AK). The majority of the increasing number of AK cases are associated with contact lens use. Appropriate eye hygiene and effective contact lens disinfection are crucial in the prevention of AK because of the lack of effective therapies against it. Currently available multipurpose contact lens disinfection systems are not fully effective against Acanthamoeba trophozoites and cysts. There is an urgent need to increase the disinfecting activity of these systems to prevent AK infections. Synthesized nanoparticles (NPs) have been recently studied and proposed as a new generation of anti-microbial agents. It is also known that some plant metabolites, including tannins, have anti-parasitic activity. The aim of this study was to evaluate the anti-amoebic activity and cytotoxicity of tannic acid-modified silver NPs (AgTANPs) conjugated with selected multipurpose contact lens solutions.MethodsThe anti-amoebic activities of pure contact lens care solutions, and NPs conjugated with contact lens care solutions, were examined in vitro by a colorimetric assay based on the oxido-reduction of alamarBlue. The cytotoxicity assays were performed using a fibroblast HS-5 (ATCC CRL-11882) cell line. The results were statistically analysed by ANOVA and Student-Newman-Keuls test using P < 0.05 as the level of statistical significance.ResultsWe show that the NPs enhance the anti-Acanthamoeba activities of the tested contact lens solutions without increasing their cytotoxicity profiles. The activities are enhanced within the minimal disinfection time recommended by the manufacturers.ConclusionsThe conjugation of the selected contact lens solutions with AgTANPs might be a novel and promising approach for the prevention of AK infections among contact lens users.Graphical

Biofilm modelling on the contact lenses and comparison of the in vitro activities of multipurpose lens solutions and antibiotics.

During the contact lens (CL) usage, microbial adhesion and biofilm formation are crucial threats for eye health due to the development of mature biofilms on CL surfaces associated with serious eye infections such as keratitis. For CL related eye infections, multi drug resistant Pseudomonas aeruginosa or Staphylococcus aureus (especially MRSA) and Candida albicans are the most common infectious bacteria and yeast, respectively. In this study, CL biofilm models were created by comparing them to reveal the differences on specific conditions. Then the anti-biofilm activities of some commercially available multipurpose CL solutions (MPSs) and antibiotic eye drops against mature biofilms of S. aureus, P. aeruginosa, and C. albicans standard and clinical strains were determined by the time killing curve (TKC) method at 6, 24 and 48 h. According to the biofilm formation models, the optimal biofilms occurred in a mixture of bovine serum albumin (20% v/v) and lysozyme (2 g/L) diluted in PBS at 37 °C for 24 h, without shaking. When we compared the CL types under the same conditions, the strongest biofilms according to their cell density, were formed on Pure Vision ≥ Softens 38 > Acuve 2 ∼ Softens Toric CLs. When we compared the used CLs with the new ones, a significant increase at the density of biofilms on the used CLs was observed. The most active MPS against P. aeruginosa and S. aureus biofilms at 24 h was Opti-Free followed by Bio-True and Renu according to the TKC analyses. In addition, the most active MPS against C. albicans was Renu followed by Opti-Free and Bio-True at 48 h. None of the MPSs showed 3 Log bactericidal/fungicidal activity, except for Opti-Free against S. aureus and P. aeruginosa biofilms during 6 h contact time. Moreover, all studied antibiotic eye drops were active against S. aureus and P. aeruginosa biofilms on CLs at 6 h and 24 h either directly or as 1/10 concentration, respectively. According to the results of the study, anti-biofilm activities of MPSs have changed depending on the chemical ingredients and contact times of MPSs, the type of infectious agent, and especially the CL type and usage time.

Assessment of a Multipurpose Solution by Video Gamers and Non-gamers

Purpose: Video gaming is popular worldwide, and its benefits and risks have come to the attention of health care providers across disciplines. Blink rate, blink amplitude, and tear film stability are compromised during dynamic, prolonged use of digital devices, which can result in symptoms of discomfort with contact lens wear. In addition to lens material and design, the choice of lens care cleaning and disinfecting solution can affect wearer satisfaction. The purpose of this evaluation was to compare real world experiences with a hyaluronan-containing contact lens multipurpose solution (MPS) among subjects classified as video gamers and non-gamers. Methods: This study was a prospective, single arm, open label survey of contact lens wearers who used a computer, smartphone, or tablet for a minimum of three hours daily. Contact lens-wearing gamers (subjects who reported that they play electronic games while wearing contact lenses 2-hours or more daily) and non-gamers were provided Biotrue MPS to use for at least seven-days while wearing a fresh pair of their respective habitual contact lenses. Subjects rated performance attributes via an online survey using a 6-point Likert scale. Results: At baseline, gamers were younger than non-gamers, more likely male, spent more time using digital devices daily, and were more likely to report they suffer from eyestrain, sensitive eyes, and red eyes. Both groups rated all queried lens-wearing performance attributes positively; gamers gave higher mean ratings than did non-gamers to 23 of 24 queried attributes, including all four pertaining to long durations of digital device use. After adjusting for both age and gender, significant differences favoring gamers were noted for all 24 attributes. Conclusions: Contact lens wearing gamers and non-gamers rated Biotrue MPS highly based upon various performance attributes. Biotrue MPS remains a good choice for general lens wear, as well as during tear film-challenging video game play.

Effect of multipurpose care solutions upon physical dimensions of silicone hydrogel contact lenses.

Interactions between contact lens multipurpose solution (MPS) components and the contact lenses with which they are used are both lens and solution dependent. As such, lens dimensional changes may arise after cleaning and immersion cycling in different lens care solutions over different time courses. In this study, the dimensional stability of five planned-replacement silicone hydrogel lenses (lotrafilcon B, comfilcon A, senofilcon A, senofilcon C, and samfilcon A) over 30 cycles in three different MPSs (Biotrue, OPTI-FREE Express, and OPTI-FREE Puremoist) was evaluated. Measurements of diameter, sagittal depth, power, roundness, and center thickness were obtained prior to, during, and after 30 cycles of cleaning and storage. Diameters of all lenses increased when soaked in Express or Biotrue but held the International Standards Organization (ISO) tolerance over the full course of 30 disinfection cycles; however, the diameters of comfilcon A, senofilcon A, senofilcon C, and samfilcon A lenses soaked in Puremoist exceeded ISO tolerance after between 4 and 9 immersion cycles. In contrast, the diameter of lotrafilcon B held tolerance. Similarly, all lenses cycled in Express or Biotrue held tolerance for sagittal depth, while in Puremoist only lotrafilcon B held tolerance. All lenses became less round in all MPSs but held tolerance for both power and central thickness. Given the lack of reported clinical issues with Puremoist when used with lenses other than lotrafilcon B, we propose that it may be appropriate to revisit the ISO test methods and tolerances to determine if they are still applicable for silicone hydrogel lenses.

Analysis of polyhexamethylene biguanide and alexidine in contact lens solutions using capillary electrophoresis, ultra-performance liquid chromatography and quadrupole time of flight mass spectrometry

Polymeric biguanides, as well as quaternary ammonium compounds, are ubiquitous antimicrobial agents in healthcare. Due to the highly cationic and polymeric nature of these compounds and the complex matrices in which they are found, the analytical characterization of products containing them remains challenging. In this work an efficient, sensitive, and high-resolution separation protocol was developed to perform quantitative measurements (sub-mg L−1) of alexidine dihydrochloride (ADH) and polyhexamethylene biguanide (PHMB) in commercial multipurpose contact lens solutions (MPS). Initially, contactless conductivity (C4D) detection was explored, but lacked adequate selectivity and sensitivity to quantify PHMB or ADH in commercial MPS. To overcome these limitations, an alternative approach using solid phase extraction (SPE) followed by separation with reversed phase ultra-performance liquid chromatography (RP-UPLC) was developed for both ADH and PHMB separation and detection. The most sensitive and reliable method investigated utilized standard additions to compensate for matrix effects. For ADH, concentration values measured with the presented method were consistent with data provided by the MPS manufacturer (1.6 mg L−1) within 0.10 mg L−1. PHMB quantification in MPS products was successful at concentrations <1 mg L−1 with quantitative reproducibility better than 2% RSD. Comparison of blind sample testing using the RP-UPLC method showed strong correlation (R2 = 0.939) of PHMB concentrations with results obtained by the United States Food and Drug Administration using a published HPLC-Evaporative light scattering detection (ELSD) assay. A significant advantage of this method is the ability to partially resolve PHMB polydispersity, which to date has been minimally studied and explained. By coupling with electrospray mass spectrometry (MS), a general trend was observed for increased retention as a function of PHMB chain length. The improved robustness and reproducibility of UV detection versus ELSD coupled with the superior resolving power of UPLC is an asset to the detection and characterization of PHMB and ADH. In addition to quality control of MPS, this method has potential application to the analyses skin wipes, wound dressings and other medical products where understanding how manufacturing processes lead to differences in polydispersity is important to maximize the antimicrobial properties while minimizing toxicologic effects.

Optimized Protocol for Testing Multipurpose Contact Lens Solution Efficacy Against Acanthamoeba.

To evaluate the interlaboratory and intralaboratory reproducibility of a proposed protocol for multipurpose contact lens solution (MPS) disinfection efficacy against Acanthamoeba. Acanthamoeba castellanii and Acanthamoeba polyphaga and four MPS with different biocidal agents were used to evaluate the protocol in two different laboratories. In addition to the negative control, a positive control and neutralization control were used. One experiment was performed in triplicate, and all other experiments were performed in duplicate in each laboratory. Acanthamoeba trophozoites were grown axenically, and cysts were generated using the starvation method. Trophozoites and cysts at a concentration of 2.0 × 10 to 2.0 × 10 organisms per milliliter were exposed to the test MPS for 0, 4 or 6 (manufacturer's recommended soak time [MRST]), 8, and 24 hr. Survivors were determined by a limiting dilution method that used a most probable number evaluation. The positive and negative controls displayed consistent results and trends both within each laboratory and between each laboratory for trophozoites and cysts of both A. castellanii and A. polyphaga. The neutralization control consistently demonstrated the ability of the neutralizing agents to neutralize the MPS and the positive control and demonstrated no inhibition of Acanthamoeba by the negative control. Testing in triplicate and duplicate demonstrated the reproducibility of the protocol both within each laboratory and between the laboratories. Our results demonstrated that the MPS at the MRST and at 8 hr (likely overnight soak time) are generally more effective against trophozoites than they are against cysts. Only the MPS with hydrogen peroxide as the biocidal agent was able to provide a greater than three-log kill of cysts at the MRST and longer. Among the MPS we tested, trophozoites of A. castellanii and A. polyphaga showed similar responses. Some variability was observed when testing cysts of both species. In both laboratories, one nonhydrogen peroxide containing MPS had some effect (>1 log kill) on A. polyphaga cysts. This solution had no effect (<1 log kill) on A. castellanii cysts, A. castellanii trophozoites, and A. polyphaga trophozoites. The protocol that we have revised and evaluated is a well-controlled and reproducible procedure that can effectively evaluate the efficacy of MPS against Acanthamoeba trophozoites. Some variability was observed when testing the cyst stage.

Contact Lens Solutions and Contact Lens Discomfort: Examining the Correlations Between Solution Components, Keratitis, and Contact Lens Discomfort.

This article will examine the current literature, as it relates to contact lens discomfort (CLD) secondary to contact lens solutions. The reader will better understand the characteristics of contact lenses, as they uniquely interact with each type of contact lens solution and also gain a better comprehension of the components of contact lens solution such as preservatives, surfactants, and chelating agents, which may contribute to discomfort. By investigating corneal staining theory and the mechanisms that contribute to its presence, the reader will gain insight into this clinical finding, which relates to selection of contact lens solutions. The FDA standards for testing solutions and how this relates to contact lens keratitis will also be appraised in regards to current ISO recommendations. Finally, better selection of multipurpose contact lens solution (MPS) and hydrogen peroxide-based solutions for patients should be accessible to the clinician based on this review and preexisting clinical findings or diagnoses. A review of current published literature from peer reviewed journals and online journals was conducted to gain an understanding of contact lens solution's impact on contact lens discomfort. Many studies have been conducted comparing comfort between various types of contact lens solutions. It is challenging to decipher this information and apply it clinically when selecting solutions for patients. By comparing solution components, how contact lens solutions interact with different types of lenses, keratitis related to contact lenses, and preexisting ocular conditions, this review will improve a clinician's ability to eliminate CLD.

Comparative in vitro effectiveness of a novel contact lens multipurpose solution on Acanthamoeba castellanii

BackgroundA multipurpose contact lens cleaning solution (MPS) containing novel active ingredients under development was compared to two commercially available MPS solutions for effectiveness against Acanthamoeba isolates.MethodsThe Acanthamoeba isolate A. castellanii was propagated for trophozoite or cyst-containing cultures for the purpose of assessment of effectiveness of each MPS. An alamar blue-based cellular respiration assay was used to assess effectiveness against trophozoites; Trypan blue hemocytometer-based microscopic counts measured cysticidal effects. To assess the general antimicrobial potency of each solution as controls for the anti-amoebic assays, comparative bactericidal effectiveness using Serratia marcenses was also performed.ResultsMinimal effectiveness against either Acanthamoeba form was observed from either commercial MPS. In contrast, the novel MPS achieved complete kill within 1 h contact time for both Acanthamoeba trophozoite and cysts. Each commercial MPS required 6 h contact time to achieve a two to three log reduction in S. marcenses. In contrast, the experimental MPS achieved disinfection in 60 min contact time, and complete kill (< 1 CFU) at 90 min.ConclusionsResults suggest that the inclusion of a novel ingredient combination within the MPS under development clearly is required and is ideal for rapid and effective killing of Acanthamoeba species in the context of contact lens disinfection systems. The representative commercially available MPS used in this testing provided minimal effectiveness against the protozoa regardless of contact time. In addition, comparative results with the bacterial agent in the control study show distinct differences in the speed to disinfection with the novel MPS. Future MPS development should consider inclusion of novel chemical entities that are effective against Acanthamoeba species to speed disinfection and further reduce the exposure potential of users of contact lenses and cleaning systems.

Correlations of In Vitro Assays for Assessing Cytotoxicity and Biocompatibility of Contact Lens Multipurpose Solutions

To demonstrate correlations among in vitro assays used for assessing cytotoxicity of contact lens multipurpose solution (MPS) and propose the use of multiple assays as a part of preclinical evaluation for MPS biocompatibility assessment. The effect of four different MPS on cell cytotoxicity, metabolic activity, and membrane integrity was performed by evaluating toxicity, expression of tight junction protein zonula occludens-1, and transepithelial electrical resistance in human corneal epithelial cells and Chinese hamster fibroblast cells. Cytotoxicity of four MPS was assayed with five different experimental systems at various concentrations. In vitro MPS-induced cytotoxicity was dependent on assay choice, concentration of MPS used, and duration of treatment. Overall, MPS-1 and MPS-2 were comparable to MPS-4 and better than MPS-3 in maintaining corneal barrier integrity and cell viability. In vitro cytotoxicity testing with MPS exposure to monolayer of cells in culture could be used as a tool to understand the potential cytotoxicity profiles of MPS and possibly a predictor of clinical outcome. Furthermore, MPS effects on in vitro cytotoxicity are best demonstrated by performing multiple assays to evaluate cell viability, metabolic activity, and membrane integrity during development.

Is contact lens multipurpose solution dual-disinfection associated with additional clinical risk?

Is contact lens multipurpose solution dual-disinfection associated with additional clinical risk?

Comparison of the Antimicrobial Efficacy of Various Contact Lens Solutions to Inhibit the Growth of Pseudomonas aeruginosa and Staphylococcus aureus.

Soft contact lenses provide perfect conditions for the breeding of pathogens. The study is a prospective, experimental study, conducted to know the antimicrobial ability of multipurpose contact lens solution against standard strains of Staphylococcus aureus and Pseudomonas aeruginosa by the stand-alone test. The test method is based on the procedures in the ISO 14729 standard primary stand-alone test. Three multipurpose contact lens care solutions commercially available in Mangalore markets, namely, Biotrue (Bausch & Lomb), Opti-Free Replenish (Alcon), and Aquasoft (Stericon Pharma), were tested for its antimicrobial effect in the microbiology lab at Kasturba Medical College, Mangalore. According to this study, the solutions named “Biotrue” and “Aquasoft” met the primary stand-alone and reached the 3log reduction and 5log reduction criteria in the manufacturer recommended time, respectively. No conclusion could be drawn for Opti-Free Replenish since the minimum recommended disinfection time was overnight, whereas it was noted for 6 hr only, and it should have been experimented further. The effectiveness of multipurpose solutions varies against different bacterial species. We have observed that the antimicrobial activity of different solutions varies with respect to time of incubation, and also there was a marked difference in the activity of some solutions against S. aureus and P. aeruginosa. So, it is necessary for the contact lens users to store their lenses in solutions for longer duration of hours. It is also recommended to use solutions that clear the ISO 14729 standards for better health conditions of the eye.

Cellular fluorescein hyperfluorescence is dynamin-dependent and increased by Tetronic 1107 treatment.

Sodium fluorescein ('fluorescein') staining of the ocular surface is frequently an indicator of compromised ocular health, and increases in the presence of certain contact lens multi-purpose solutions (MPS), a phenomenon known as solution induced corneal staining (SICS). The mechanism(s) underpinning fluorescein hyperfluorescence are uncertain, though may reflect increased cellular uptake of fluorescein by corneal epithelial cells. We have developed an in vitro model to study fluorescein uptake in both 'generic' mammalian cells (murine fibroblasts) and human corneal cells. Fluorescein hyperfluorescence increased after treatment with two MPS associated with clinical corneal fluorescein staining, yet there was no cellular hyperfluorescence for two MPS that do not cause this staining. Increased fluorescein uptake did not correlate with presence of a necrotic or an apoptotic marker (propidium iodide and caspase-3 respectively). Incubation of MPS-treated cells with dynasore (an inhibitor of dynamin, implicated in endocytic pathways) reduced fluorescein uptake irrespective of MPS treatment. The non-ionic surfactant Tetronic 1107 (present in both MPS associated with corneal fluorescein staining) increased uptake of fluorescein for both cell types, whereas an unrelated surfactant (Triton X-100) did not. We conclude that the clinical hyperfluorescence profile observed after exposure to four MPS can be reproduced using a simple model of cellular fluorescein uptake, suggesting this is the biological basis for SICS. Fluorescein entry does not correlate with necrosis or apoptosis, but instead involves a dynamin-dependent active process. Moreover the surfactant Tetronic 1107 appears to be a key MPS constituent triggering increased fluorescein entry, and may be the major factor responsible for SICS.