Contact Lens Cases Research Articles

Sol-Gel Nanocomposite Coatings for Preventing Biofilm Formation on Contact Lens Cases.

PurposeTo evaluate the efficacy of a nanosilver-based sol–gel coating in preventing biofilm formation on contact lens cases.MethodsAn organic–inorganic hybrid silica–zirconia sol formulation with immobilized silver nanoparticles was deposited on contact lens case coupons. The coated and uncoated coupons were subjected to biofilm formation to Gram-negative and Gram-positive keratitis isolates and ATCC strains using a standard protocol. The biofilms were evaluated using crystal violet, MTT assay, and scanning electron microscope (SEM) examination. The duration of efficacy of the coating was evaluated by exposing the coated and uncoated coupons to a multipurpose lens cleaning solution for various durations up to 30 days and comparing their biofilm characteristics. The cytotoxicity of the coated surface was assessed using cell culture studies.ResultsCross-hatch tests and SEM confirmed the presence of a uniform, well-adhered coating on the surface. The coating resulted in a nearly 95% reduction in biofilm formation of the tested bacteria and was effective despite exposures of up to 30 days to a multipurpose lens cleaning solution. The coating did not exhibit cytotoxicity to human corneal epithelial cells.ConclusionsThe silver nanoparticle-based coating exhibits a good antibiofilm property for both Gram-negative bacilli and Gram-positive cocci and is promising for commercial use in preventing contact lens-related infections.Translational RelevanceBiofilm formation on lens cases continues to be an important concern. The proposed coating will help reduce such formations, thus reducing the risk of lens-associated microbial keratitis.

Microbiological analysis of contact lens cases and effective health behaviors

Introduction: Contact lenses are increasingly being used for cosmetic or therapeutic purposes, followed by subsequent contamination and complications such as keratitis. The lens case is one of the most common places to find the cause of contamination. Objectives: This study was designed to evaluate the health behaviors affecting the lens case contamination and its relationship with the result of lens case culture which can help in prevention of complications. Patients and Methods: In this cross-sectional study that was performed in northwest of Iran, 150 asymptomatic participants were assessed for health behaviors affecting the lens case contamination and their lens cases were sampled for culture and antibiogram. Data were analyzed with SPSS-16 software. Results: The frequency of positive microbial culture in medical and cosmetic contact lens cases was 30.7% and 66.8%, respectively and 32.7% in general. Among the isolated bacteria observed in positive cultures, Alcaligenes,Enterobacter aerogenes, gram-positive Diphtheroid bacilli, Pseudomonas aeruginosa and Staphylococcus epidermidis were the most common microorganisms, respectively. Conclusion: A significant proportion of contact lens cases, especially those used for cosmetic purposes had bacterial contamination. Failure to replace the lens case for more than 9 months and the mismatch of the lens solution brand with its storage case will increase bacterial contamination. Washing the lens case with soap and water, and drying it after washing, will reduce bacterial contamination.

Presence of Acanthamoeba and diversified bacterial flora in poorly maintained contact lens cases

Acanthamoeba can cause visually destructive Acanthamoeba keratitis (AK) in contact lens (CL) users. The purpose of this study was to determine whether Acanthamoeba was present in the CL cases of CL wearers and to develop techniques to prevent the contaminations. To accomplish this, 512 CL case samples were collected from 305 healthy CL wearers. Using real-time PCR, Acanthamoeba DNA was detected in 19.1% of CL cases, however their presence was not directly associated with poor CL case care. Instead, the presence of Acanthamoeba DNA was associated with significant levels of many different bacterial species. When the CL cases underwent metagenomic analysis, the most abundant bacterial orders were Enterobacteriales followed by Burkholderiales, Pseudomonadales, and Flavobacteriales. The presence of Acanthamoeba was characterized by Propionibacterium acnes and Rothia aeria and was also associated with an increase in the α diversity. Collectively, Acanthamoeba contamination occurs when a diversified bacterial flora is present in CL cases. This can effectively be prevented by careful and thorough CL case care.

Compliance behaviour change in contact lens wearers: a randomised controlled trial.

Water exposure during contact lens wear has been associated with contact lens disease including microbial keratitis and sterile corneal infiltrates. Despite the documented risks, water exposure is common amongst lens wearers. This study aimed to determine the effect of water education in the form of "no-water" lens case stickers on water-contact behaviours and storage case contamination. In a prospective, masked, randomised controlled trial, 200 daily lens wearers were randomised to either receive a storage case with a "no-water" sticker (test) or without a "no-water" sticker (control). Both groups received written compliance information. Participants completed a self-administered lens hygiene questionnaire at baseline and after 6 weeks. Microbial analysis of used storage cases, collected at both study visits, was conducted using ATP and limulus amebocyte lysate (LAL) assays for overall microbial contamination and endotoxin levels, respectively. A one-way ANCOVA and multiple logistic regression determined the change in water-contact behaviours and storage case contamination over time. A total of 188 lens wearers completed both study visits; 128 females and 60 males; average age 29 ± 13 (range 18-78 years); 95 test and 93 control participants. After 6 weeks, the overall water exposure score and endotoxin levels reduced significantly in the test group compared with the control group (p < 0.05). There were no significant changes in individual water-contact behaviours or overall storage case contamination. A no-water infographic on the contact lens case improved overall water-contact behaviours and reduced storage case endotoxin. Refining the messaging may be beneficial in future to improve other aspects of compliance.

Different contact lens case treatment methods for the elimination of pathogen biofilms associated with contact lens related microbial keratitis

Objective To investigate the biofilm-forming abilities of pathogens associated with contact lens related microbial keratitis and to compare the efficacies of different treatments in eliminating biofilms in contact lens cases (CLCs). Methods Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Candida albicans biolm formation in polypropylene CLCs was examined by using a static biofilm formation model, which was incubated at 37 ℃ for 24 hours.According to the CLC treatment methods, the experimental groups were divided into a control group, a room temperature air-drying group, a contact lens care solution soaking group, a heat-drying group and a soaking-heating group.A pathogen colony counting-based serial dilution micro-counting method was applied to evaluate the biofilm elimination efficacies and pathogen killing rates of treatments. Results All four tested strains formed biofilms on the inner walls of the CLC, and the biomasses of S. aureus, P. aeruginosa, E.coli and C. albicans biofilm were (10.78±2.12), (9.19±0.57), (8.03±0.30), and (7.50±0.07)lg CFU/ml, respectively.The S. aureus biofilm biomass was significantly higher than those of the other strains (P<0.05). The biofilm biomasses of all the tested strains in the heat-drying and the soaking-heating groups were significantly lower than those in the control group (all at P<0.05); and the biofilm biomasses of S. aureus and E. coli in the soaking group were significantly lower than that in the control group (all at P<0.05). The heat-drying treatment resulted in a killing rate of (51.76±16.75)% for S. aureus, (68.63±4.43)% for P. aeruginosa, (83.51±13.97)% for E. coli, and (97.13±5.19)% for C. albicans, respectively (F=31.806, P<0.001). Significant differences were observed between the killing rates for each bacterium (all at P<0.05). The E. coli and C. albicans killing rates of the soak-heating treatment were (100.00±0.00) % and (97.79±7.67)%, respectively, and were significantly higher than (81.13±14.86)% of S. aureus and (74.22±11.91)% of P. aeruginosa (all at P<0.05). Conclusions Heating alone or combined with the use of contact lens care solution treatment can improve the pathogen killing rates and effectively eliminate the bacterial and fungal contaminations in CLCs. Key words: Microbial keratitis; Contact lens cases; Biofilm; Heating

The efficacy of povidone-iodine, hydrogen peroxide and a chemical multipurpose contact lens care system against Pseudomonas aeruginosa on various lens case surfaces

PurposeTo determine the antimicrobial efficacy of a povidone-iodine system (PVP-I; cleadew, OPHTECS Corporation, Kobe, Japan), a peroxide system (AOSEPT Plus with HydraGlyde, Alcon, Fort Worth, TX), and a chemical multipurpose system (renu fresh, Bausch & Lomb, Rochester, NY) on contact lens case surfaces that are both in contact and not in contact with the solutions during lens disinfection. MethodsThe surfaces of the inner walls, underside of the lid, and lens holder (if applicable) of the cases were inoculated with P. aeruginosa ATCC 27853. The cases were disinfected with the solutions as per their manufacturer instructions. After disinfection, the inoculated surfaces were swabbed and the amount of surviving P. aeruginosa was determined. Following this experiment, separate cases were inoculated and disinfected as before. This time the cases were agitated after recommended disinfection time and the amount of P. aeruginosa in the disinfecting solution was quantified immediately, and again after resting for 7 days. Experiments were conducted in triplicate (n = 3). ResultsUnits are expressed in log CFU. All three solutions significantly reduced P. aeruginosa on direct-contact surfaces (all p < 0.039). On non-contact surfaces, the reduction of P. aeruginosa in the PVP-I system (pre-disinfection: 6.8 ± 0.5, post-disinfection: 1.0 ± 0.0; p < 0.001) was significant, but not for the hydrogen peroxide system (pre-disinfection: 6.3 ± 0.6, post: 5.5 ± 0.5; p = 0.194) and the chemical multipurpose system (pre-disinfection: 6.6 ± 0.1, post-disinfection: 5.6 ± 0.8; p = 0.336). After 7 days post-disinfection, no P. aeruginosa regrowth was observed in the PVP-I system (Day 1: 1.0 ± 0.0, Day 7: 1.0 ± 0.0; p = 1) and the chemical multipurpose system (Day 1: 4.2 ± 0.2, Day 7: 1.8 ± 0.9; p = 0.012), however regrowth was observed in the hydrogen peroxide system (Day 1: 3.4 ± 0.6, Day 7: 6.1 ± 0.4; p = 0.003). ConclusionThe PVP-I system was more effective against P. aeruginosa on non-contact surfaces than the hydrogen peroxide system or the chemical multipurpose system and is capable of inhibiting regrowth of P. aeruginosa for at least 7 days post-disinfection.

Study of biofilm formation in bacterial isolates from contact lens wearers.

Purpose:To detect biofilm forming capacity of bacterial isolates obtained from the conjunctiva, contact lens and accessories of contact lens wearers using phenotypic and genotypic methods.Methods:Bacterial strains were collected from the conjunctiva, contact lens and lens storage cases of contact lens wearers. The phenotypic detection of biofilm production was done using the tube method and congo red agar method. The biofilm-forming related genes, icaA, of Coagulase negative Staphylococcus (CONS) and Staphylococcus aureus, and pslA, of P. aeruginosa, were detected using PCR.Results:A total of 265 bacterial isolates which included S. aureus, CONS, Pseudomonas, Nil-fermenter Gram-negative bacilli (NFGNB), Bacillus spp, Diphtheroids, Micrococci, Klebsiella pneumonia, Klebsiella oxytoca, E. coli, Proteus mirabilis, Proteus vulgaris, Citrobacter koseri, Citrobacter freundii, Enterobacter cloacae, Moraxella were obtained. Of the 265 isolates, 53.5% were moderately positive, 33.2% strongly positive and 13.2% negative for biofilm production by tube method and 36.6% were moderately positive, 40% strongly positive and 23.3% negative for biofilm production by congo red agar method. Of the four S. aureus isolates, two (50%) showed the presence of icaA gene. Of the 23 CONS isolates, three (13%) showed the presence of icaA gene. All the Pseudomonas isolates were negative for presence pslA (1119 bp) gene though most of them were phenotypically positive for biofilm formation.Conclusion:Most of the bacterial isolates obtained from contact lens wearers had the potential to produce biofilms. Tube method and Congo red agar method exhibited significant statistical correlation (P-value = 0.006) and picked up a good number of biofilm-forming isolates, hence may be used for detection of biofilm production. The absence of biofilm-forming gene did not rule out the possibility for phenotypic biofilm production by bacteria.

Realisation and assessment of a low-cost LED device for contact lens disinfection by visible violet light.

This study presents a device for efficient, low-cost and eye-friendly overnight disinfection of contact lenses by visible violet light as an alternative to disinfection with biocide-containing solutions. Bacterial solutions with one Pseudomonas and one Staphylococcus strain each were irradiated for up to 8 h in commercial transparent contact lens cases by the presented light-emitting diode (LED) device. Samples were taken at different intervals and distributed on agar plates. The surviving bacteria were determined by counting of colony-forming units and compared to the specific requirements of the stand-alone test for contact lens disinfection of the hygiene standard ISO 14729. The concentration of both microorganisms was reduced by three orders of magnitude after less than 4 h of irradiation. The LED current and intensity have not yet been at maximum and could be further increased if necessary for other microorganisms. The presented device fulfils the requirement of the stand-alone test of the contact lens hygienic standard ISO 14729 for the tested Pseudomonas and Staphylococcus strains. According to literature data, the inactivation of Serratia marcescens, Candida albicans and Fusarium solani seems also possible, but may require increased LED current and intensity.

Comparison of microbiome isolated from the conjunctiva, contact lens and lens storage case of symptomatic and asymptomatic contact lens users

Contact lenses (CLs) are increasingly being used for cosmetic or therapeutic purposes. Lack of compliance and poor hygiene towards lens care is strongly associated with microbial contamination and has been proved to result in eye infections. The present study was done to compare the microbial flora between symptomatic and asymptomatic contact lens users. The study also attempts to analyze the contact lens hygiene practices of CL users. Six samples each were collected from both the eyes, CLs and lens cases of 40 CL users (n=240) divided into two groups based on symptoms present asasymptomatic CL users and symptomatic CL users. Organisms were identified using standard microbiological techniques. The proportion GNB obtained in symptomatic CL users was significantly higher when compared to asymptomatic CL users (p-value= <0.003). In 56.2% eyes, the microbial flora of conjunctiva was similar to either the contact lens isolate/storage case. Enterococcal microbial keratitis was seen in one case. There was significant microbial contamination present in CL users despite compliance to contact lens hygiene practices. There were a significant number of bacteria (p-value <0.001) present which were resistant to ampicillin, amoxicillin-clavulanate, and cefotaxime in both the groups.

Bacterial biofilm in silver-impregnated contact lens cases

PurposeThis study investigated the efficacy of pre-conditioning lens cases on bacterial biofilm formation and removal. MethodsSilver impregnated (MicroBlock / ProGuard™ & i-Clean) and control storage cases were pre-conditioned for 24 h with their respective multipurpose solutions (MPDSs). Cases were then inoculated with 2 ml of 106 CFU/mL of ocular isolates of either P. aeruginosa or S. aureus and incubated for 48 h. Cases were subsequently disinfected (4−6 hours) as per the manufacturer’s recommended disinfecting time (MRDT) followed by the recommended case hygiene procedures - recapping wet (MicroBlock / ProGuard™ cases only) or rinse and air-dry or rinse, tissue-wipe and air dry (mechanical disruption). Surviving bacteria were enumerated using standard techniques. ResultsPre-conditioning the MicroBlock / ProGuard™ cases with MPDS significantly reduced biofilm formation (-1.1 log10 CFU, p < 0.01 for P. aeruginosa & -1.3 log10, p < 0.001, CFU for S. aureus) compared to the i-Clean lens cases. Maintaining the MicroBlock / ProGuard™ lens cases wet after the MRDT resulted in partial removal of bacterial biofilms (-2.9 log10 CFU, p < 0.001 for P. aeruginosa and -2.6 log10 CFU, p < 0.001 for S. aureus). Air-drying of all three types of lens storage cases after MRDT significantly reduced the bacterial biofilm (-5.4 log10 CFU, p < 0.001 for P. aeruginosa and -3.5 log10 CFU, p < 0.001 for S. aureus). Mechanical disruption produced the greatest reduction in the levels of bacterial biofilm in all 3 types of lens cases tested (-6.8 log10 CFU, p < 0.001 for P. aeruginosa and -4.5 log10 CFU, p < 0.001 for S. aureus). Synergi MPDS was significantly better than AQuify MPDS in removing bacterial biofilm from all 3 lens case types for case hygiene treatments with an air-drying step. ConclusionPre-conditioning of silver-impregnated ProGuard™ lens cases inhibited initial bacterial biofilm formation. Synergi MPDS was more effective than AQuify MPDS in removing bacterial biofilm in silver impregnated cases and tissue-wiping significantly improved biofilm removal.

Risk factors associated with contamination of orthokeratology lens cases

PurposeTo evaluate the risk factors associated with contamination of lens cases in a group of orthokeratology (ortho-k) lens wearers. MethodOrtho-k patients attending the Contact Lens Clinic of the Hospital were required to complete a checklist about their routine daily care and handling of lens cases. Their cases were then collected for analysis. Contamination was evaluated by determining the optical density (OD) of crystal violet stained biofilm present in the cases. OD values were divided into three groups, lower, middle, and upper tertiles, and associations between risk factors were determined by multivariate analysis. ResultsA total of 194 subjects were recruited. Twenty-five subjects used cylindrical lens cases (CC), 98 flat cases with ridges (FCR), and 71 flat cases without ridges (FC). FCRs were the most heavily contaminated and CC showed least contamination (FCR > FC, OR 2.16, CI 1.11–4.18, p = 0.023; FCR > CC, OR 8.86, CI 2.97–26.44, p <0.001; FC > CC, OR 2.33, CI 1.35–12.45, p = 0.013). Replacing lens cases monthly significantly reduced the risk of high contamination (OR 0.013, CI 0.06-0.30, p < 0.001), compared to those used for three months. Cases that were not rinsed (OR 3.44, CI 1.50–7.86, p = 0.003) or rinsed by other methods (OR 4.07, CI 1.67–9.92, p = 0.002) had significantly more contamination, compared to those rinsed with multipurpose solution. Lens cases, which were not dried (OR 11.36, CI 2.06–62.93, p = 0.005) or air-dried (OR 8.71, CI 1.16–65.56, p = 0.036), showed more contamination compared to those wiped with tissue daily. ConclusionCase design (cylindrical), monthly replacement, daily rinsing with MPS, and wiping with tissue daily can effectively reduce biofilm formation in contact lens cases.

Evaluation of prevention and disruption of biofilm in contact lens cases.

The presence of biofilm in the lens case has been shown to be a risk factor for contamination of lenses and consequently microbial keratitis. This study aimed to evaluate effectiveness of solutions for rigid contact lenses in prevention and disruption of biofilm in lens cases and methods for biofilm detection. This study adopted a stepwise approach to evaluate effectiveness of four rigid lens disinfecting solutions against biofilm. These included two polyhexamethylene bigiuanide (PHMB) solutionsand a chlorhexidine/PHMB-based solution, as well as a novel povidone-iodine formulation. The presence of biofilm following exposure to the solutions was assessed using both crystal violet (CV) staining and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) viability assay, taking into account the effect of lens case design. Three lens case designs, conventional flat, large bucket type, and cylindrical cases, were investigated for the ability to trap stain and allow biofilm formation. Considerable differences were noted between solutions in their ability to prevent and disrupt biofilm (p<0.001). Lens case design greatly influenced optical density (OD) measurements even in negative controls, as cylindrical cases trapped more stain, increasing OD readings. Correcting for this factor reduced variations, but could not differentiate between residues and biofilm. MTT assay revealed that both povidone-iodine and chlorhexidine-containing solutions could effectively kill>95% of organisms, whilst PHMB-based solutions were less effective with up to 55% of staphylococci and 41% of Pseudomonas surviving at 24h. Biofilm can rapidly form in lens cases and may not be killed by disinfecting solutions. Of the solutions tested, none were able to prevent biofilm formation or disrupt established biofilm, but those containing chlorhexidine or povidone iodine were able to penetrate the biofilm and kill organisms. Assessment of biofilm by CV assay may be confounded by lens case design. Whilst CV assay can demonstrate presence of biofilm, this technique should be accompanied by viability assay to determine bactericidal activity.

In Vitro Antimicrobial Efficacy of Silver Lens Cases Used With a Multipurpose Disinfecting Solution.

PurposeWe evaluate the in vitro antibacterial activity of silver-copolymerized barrel cases compared to nonsilver barrel cases in combination with a multipurpose disinfecting solution (MPDS).MethodsThe ability of silver and nonsilver cases to reduce the number of adherent Gram-positive and Gram-negative bacteria was assessed. Additionally, the efficacy of silver cases along with MPDS was investigated in the presence of organic soil and contact lenses. Contact lens cases were challenged with 106 colony-forming units (CFU)/mL of five bacterial species. Adherent bacteria were dislodged from lens cases and surviving organisms enumerated.ResultsSignificantly lower numbers of microbes were recovered from silver cases compared to controls, for all bacterial strains (P < 0.005). The combination of silver case along with MPDS showed added efficacy against Gram-positive and -negative bacteria with a maximum reduction of 3.00 ± 0.5 Log10 CFU/mL, compared to the efficacy of silver cases alone (1.97 ± 0.4 Log10 CFU/mL). The addition of organic soil and a contact lens resulted in a significant (P < 0.005) decrease (a maximum of 1.68 ± 0.2 log10 CFU/mL) in disinfection efficacy when MPDS and either silver or control cases were used.ConclusionsSilver-copolymerized barrel cases work on conjunction with a hypochlorite producing MPDS in the presence of contact lenses and organic soil to reduce microbial contamination of lens cases.Transitional RelevanceSilver-copolymerized barrel contact lens cases show promising in vitro antibacterial activity against bacterial types commonly implicated in contact lens-related corneal infections. This intervention may limit storage case contamination during use and reduce the frequency of contact lens-related microbial disease.

A study of contact lens compliance in a non-clinical setting

PurposeTo evaluate soft contact lens replacement, overnight (ON) wear, and contact lens case compliance in a non-clinical sample. MethodsSubjects (n = 297) were recruited at the Center for Science and Industry (COSI) in Columbus, Ohio. Adult (≥ 18 years) soft contact lens wearers completed a survey about contact lens replacement, ON contact lens wear, and contact lens case replacement habits. ResultsTwo-week replacement lenses (according to the manufacturer’s replacement schedule [MRS]) were most common (45.5%), followed by monthly (34.3%) and daily replacement (20.2%). Non-compliance with replacement schedule was reported in 38.7% of subjects. Age (p = 0.02), years of lens wear (p = 0.02), and MRS (p <0.0001) affected replacement compliance. Post-hoc analysis showed daily replacement wearers were more compliant than two-week (p <0.0001) and monthly (p <0.0001) replacement wearers with prescribed lens replacement. Non-compliance with prescribed ON wear was reported in 23.9% of subjects. Subjects who were non-compliant with lens replacement were more likely to be non-compliant with ON wear (p = 0.02) and had worn contact lenses for less time (p = 0.02). Of the subjects who used contact lens cases, 74.6% were unsure when they should replace their case. Frequency of case replacement was not associated with age (p = 0.5), gender (p = 0.5), years of contact lens wear (p = 0.7), MRS (p = 0.4), replacement compliance (p = 0.3), or ON wear compliance (p = 0.7). ConclusionsDaily replacement wearers were most likely to be compliant with contact lens replacement, but all subjects, including daily replacement wearers, had similar ON wear non-compliance. Non-compliant lens replacement was associated with non-compliant ON wear, but contact lens case replacement was not related to either compliance category. The majority of subjects had no knowledge of proper contact lens case replacement, despite compliance in other categories.

Hand hygiene is linked to microbial keratitis and corneal inflammatory events.

Lack of or inadequate hand washing is a risk factor in the development of contact lens related microbial keratitis and corneal inflammatory events. In the public health domain there is compelling evidence that proper hand washing with soap can save lives. The purpose of this review is to draw attention to some of the public health literature in support of hand washing and how education can influence patients' hand hygiene behavior. Contact lens wearers are also guilty of poor hand washing behavior but there is scant evidence that education of hand washing procedures of lens wearers alters patient non-compliance. It is well known that pathogenic microbial contamination of contact lenses, lens cases, care solutions and anterior ocular components have been found with contact lens wear. However while the originating source may be hands or water, it is most likely both of these. Besides proper hand washing this paper will include mitigating strategies for avoiding microbial contamination.

Adhesion of Stenotrophomonas maltophilia, Delftia acidovorans, and Achromobacter xylosoxidans to Contact Lenses.

Contact lens cases become contaminated with microbes during use. We wished to compare the adhesion of uncommon bacterial contaminants isolated from lens cases to contact lenses with and without organic soil. Strains of Delftia acidovorans (001), Stenotrophomonas maltophilia (002 and 006), and Achromobacter xylosoxidans (001) isolated from contact lens cases (test strains) and Pseudomonas aeruginosa (Paer1) isolated from eyes at the time of infiltrative response (control strain) were used. Bacteria were grown and resuspended in phosphate-buffered saline (PBS) or 10% organic soil (heat-killed Saccharomyces cerevisiae resuspended in complement inactivated bovine serum). Two silicone hydrogel (senofilcon A and comfilcon A) and one hydrogel lens (etafilcon A) lens materials were used. Bacteria (1.0×10 and 1.0×10 colony-forming units/mL; CFU/mL) adhered to lenses for 24 hr and the numbers of bacteria adherent to each lens type (with and without organic soil) were estimated by culture. All the four test strains adhered in significantly greater numbers to contact lenses after incubation in inoculum prepared with organic soil compared with PBS-D. acidovorans 001 (0.7 log10 CFU; P<0.05), S. maltophilia 002 (1.7 log10 CFU; P<0.05), S. maltophilia 006 (0.9 log10 CFU; P<0.05), and A. xylosoxidans 001 (0.4 log10 CFU; P<0.05). However, the presence of organic soil did not increase adhesion of P. aeruginosa Paer1 (-0.1 log10 CFU; P>0.05). Achromobacter xylosoxidans 001 (P<0.01), D. acidovorans 001 (P<0.01), and S. maltophilia 002 (P<0.01) significantly differed in their adhesion to the three contact lens materials. Bacteria that are commonly found in contact lens cases adhered to contact lenses in relatively high numbers in the presence of organic soil. This might indicate that a similar phenomenon occurs in the presence of tears. This may facilitate their transfer from the lens to the cornea and the production of corneal infiltrates.

In Vitro Evaluation of a Hypochlorous Acid Hygiene Solution on Established Biofilms.

The purpose of this study was to determine whether a commercial formulation of hypochlorous acid hygiene solution (0.01%), Avenova, can destroy existing biofilms formed by ocular clinical bacterial isolates, including blepharitis isolates of Staphylococcus aureus and coagulase-negative staphylococci, and a keratitis isolate of Pseudomonas aeruginosa. Biofilms grown in bacterial growth media on disposable contact lens cases were challenged with hypochlorous acid hygiene solution. At various time points, surviving bacteria were quantified by serial dilution and colony counts. Staphylococcus aureus biofilms formed on glass were challenged using a hypochlorous acid hygiene solution and imaged using vital staining and confocal laser scanning microscopy. Bactericidal activity (≥3 Log10; 99.9%) was observed for all tested bacterial species after a 30-min exposure. Staphylococcus aureus biofilms had a bactericidal level of killing by 10 min (P<0.01), Staphylococcus capitis by 5 min (P<0.001), Staphylococcus epidermidis by 30 min (P<0.001), and P. aeruginosa by 10 min (P<0.01). Confocal microscopy and crystal violet staining analysis of bacterial biofilms treated with hypochlorous acid solution both demonstrated that biofilm bacteria were readily killed, but biofilm structure was largely maintained. Hypochlorous acid (0.01%) hygiene solution was able to achieve bactericidal levels of killing of bacteria in biofilms but did not disrupt biofilm structures. Susceptibility of tested staphylococcal blepharitis isolates varied by species, with S. capitis being the most susceptible and S. epidermidis being the least susceptible.

A Survey on the status of contact lens cases hygiene compliance in the Orthokeratology Lens wearers

Objective To investigate the current situation of contact lens cases′ contamination and contact lens hygiene compliance in Wenzhou, so as to provide a basis for further improvement of hygiene for wearers. Methods The general data of the wearer and the present condition of the lens cases hygiene compliance were investigated by the questionnaire, and the contamination was judged by the microbiological culture. Results The positive rate of bacterial culture in the contact lens cases was 43.96%(40/91). Compared with the positive culture group, the negative group performed better in hand hygiene (χ2=17.624, P<0.01), and the frequency of the case sterilization in the negative group (χ2=43.754, P<0.01), cleaning frequency (χ2=69.737, P<0.01) were higher than the positive group. In the choice of cleaning methods, the proportion of using brushing (χ2=65.441, P<0.01) and re-rinsing (χ2=59.663, P<0.01) in the negative group was higher than that of the positive group. The results were all statistically different. Conclusion The present condition of hygiene compliance of the orthokeratology lens wearers in Wenzhou is not so well, and it needs to be further improved. And agents, scrubbing, rinsing and drying are effective for reducing microbes. Key words: Orthokeratology Lens; Contact lens cases hygiene compliance

Bacterial Coaggregation and Cohesion Among Isolates From Contact Lens Cases.

The aim of this study was to examine cohesion, coaggregation, and coculture between bacteria commonly isolated from contact lens cases. Staphylococcus epidermidis, Staphylococcus haemolyticus, Micrococcus luteus, and Acinetobacter radioresistens (two strains each) isolated from contact lens cases of two asymptomatic wearers were used in this study. In the cohesion assay, bacteria were grown, washed, and examined by incubating lens cases with two different types of bacteria sequentially and assessing the number of adhered cells of each isolate. The ability of isolates to interfere with the growth of other isolates was tested by growing strains in cocultures for 24 hours and determining the numbers of cells of individual strains. For coaggregation, equal proportions of two bacterial suspensions were mixed and allowed to coaggregate for 24 hours. Inhibition of coaggregation was tested by the addition of lactose (0.06 M) or sucrose (0.06 M) or pronase. The initial adhesion of M. luteus or A. radioresistens significantly (P < 0.05) enhanced the subsequent adhesion of the staphylococci. The addition of A. radioresistens in liquid media significantly (P < 0.05) enhanced the growth of staphylococci. S. epidermidis or S. haemolyticus coaggregated with M. luteus or A. radioresistens. The degree of coaggregation varied between 30% and 54%. The highest coaggregation (54% ± 5%) was seen between A. radioresistens 22-1 and S. epidermidis 22-1, isolated from the same lens case. Only lactose or sucrose treatment of staphylococci could partly inhibit coaggregation of some pairs. Coaggregation, cohesion, and growth promotion may facilitate the process of bacterial colonization of contact lens cases.

Impact on gas-permeable contact lens parameters after storage in a non-neutralized hydrogen peroxide case during 1 to 30 days

Purpose: This study was conducted to evaluate the impact of storing large gas permeable lenses in a regular soft contact lens case, filled with non-neutralized hydrogen peroxide, during 1 to 30 days.