Lens Case Contamination Research Articles

Compliance of Soft Contact Lens Care and Bacterial Contamination Among University Students in Palestine.

This study investigated the contact lens care compliance, noncompliance reasons, bacterial contamination rate, and the behaviors associated with contamination among university students in Palestine. 133 Habitual soft contact lens wearers were recruited in this study and interviewed using a face-to-face questionnaire, to obtain data on demographics, contact lenses, modifiable lens care behaviors and the reasons for non-compliance. High, moderate, and low lens care behaviors were identified. Additionally, a sample of the participant's storage cases was collected for bacterial contamination testing. The participants' mean age was 22.4±4.4, with female predominance (62.4%). The average compliance rate was 76.8%. Total CL care compliance (100%) was found in filling the case with adequate solution, not sharing the lenses or storage case with others, while the poorest compliance (>40%) was found in attending after-care visits, checking the solution's expiry, and re-disinfecting the lenses with a fresh solution before insertion after prolonged storage. Poor understanding of the instructions contributed significantly to a low level of compliance (P≤0.05). Gram-positive and gram-negative bacteria were detected in 19.55% of the participants' cases. Poor hand and case hygiene, no replacement of lens cases (monthly), and water exposure were linked to bacterial contamination of storage cases. This study indicated moderate to high compliance in CL care, averaging 76.8%. Poor compliance was found in attending after-care visits, checking the solution's expiry, and re-disinfecting the lenses with a fresh solution after an extended storage interval. 19.55% of the cases had bacterial contamination, with Staphylococcus Aureus being the most common. Poor hand and lens case hygiene and water exposure are found to be associated with lens case contamination. These findings emphasize the importance of patient education on safer lens wear modalities, proper wearing schedules, and hygiene regimens to reduce the risks of developing contact lens complications.

Effect of Hygiene Procedures on Lens Case Contamination with Povidone-Iodine or Multipurpose Disinfecting Solutions.

A multipurpose disinfecting solution (MPDS), which contains povidone-iodine (PI) as a disinfectant, has high disinfecting efficacy not only on planktonic bacterium but also on the case biofilms. The addition of case hygiene practice removed more bacteria from cases than MPDS alone. This study compared the ability of two MPDSs, one containing PI and another containing polyaminopropyl biguanide and polyquaternium, to reduce bacterial numbers in solution or adhered to the cases following case hygiene procedures. Bacterial strains (Delftia acidovorans, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Serratia marcescens, Staphylococcus aureus, and Staphylococcus epidermidis) were exposed to the MPDSs for the recommended disinfection times, and the viable number evaluated according to ISO 14729. Cases were inoculated with bacterial strains and incubated for 24 hours to allow for biofilm formation. Cases were disinfected with both disinfecting solutions for 4 hours and rinsed, followed by recapping or air-drying, or tissue-wiping and air-drying for 18 hours. The number of survivors was counted using standard culture techniques. Both products exceeded the recommended 3-log reduction against planktonic bacteria. Regarding biofilm, after rinsing and recapping wet, the numbers of D. acidovorans (mean difference [95% confidence interval] log10 colony-forming units per case, -2.9 [0.8 to -4.6], P < .01), P. aeruginosa (-2.0 [0.5 to -3.1], P < .01), S. marcescens (-1.7 [0.8 to -3.5], P < .05), and S. epidermidis (-2.1 [0.6 to -3.5], P < .05) in PI cases were significantly lower than in the dual-disinfectant MPDS storage cases. After air-drying, the PI storage cases had significantly lower numbers of S. maltophilia (-2.6 [0.6 to -4.0], P < .01), D. acidovorans (-1.6 [0.7 to -3.3], P < .05), and S. aureus (-1.6 [0.7 to -3.1], P < .05). The addition of tissue-wiping reduced the bacterial numbers in the MPDS storage cases to levels in the PI storage cases. Contact lens users should be recommended to tissue-wipe and air-dry their lens storage cases after disinfection with regular MPDS.

Effect of povidone iodine contact lens disinfecting solution on orthokeratology lens and lens case contamination and organisms in the microbiome of the conjunctiva

PurposeTo compare lens cleaning routines using a povidone iodine-based rigid lens disinfecting solution and its effect on conjunctival colonisation, and lens and lens case contamination. MethodsParticipants, aged 6–10 years, receiving orthokeratology treatment were randomised to four lens cleaning routines: with and without the use of daily and/or weekly cleaners, which were performed by their parents. Conjunctival colonisation was compared before lens wear and at 1-, 3-, and 6-month after commencement of lens wear. Contamination of lenses and lens cases was investigated at these times. Organisms were identified using MALDI-TOF mass spectrometry. ResultsOf the 76 participants who completed the study, conjunctival colonization was present in 24 (32 %) at baseline. Of the remaining 52 participants, 34 consistently yielded no growth. Participants positive at baseline were statistically more likely to be colonized after commencement of lens wear (p = 0.020). Overall, colonization rate was reduced to 15 % (11/72) after 6-month lens wear, which reached significance for initially colonized participants (p < 0.001). Few cultures yielded potential ocular pathogens, with notably no Pseudomonas aeruginosa. Contamination rates of both lenses and lens cases were also low, with few isolations of ocular pathogens. No significant differences were observed between cleaning regimes for conjunctival colonization or contamination of lenses or cases. ConclusionsDisinfection for rigid and ortho-k lens wearers may be effectively achieved with the use of povidone iodine-based solution, apparently regardless of cleaning routine adopted in the current study. The absence of pathogens in the conjunctiva, lenses, and lens cases in the great majority of samples indicates that it can improve the safety of overnight lens wear.

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.

Microbial Contamination of Rigid Gas Permeable (RGP) Trial Lenses and Lens Cases in China

ABSTRACTPurpose: This study aimed to evaluate the microbial contamination level and its influencing factors of rigid gas permeable (RGP) trial lenses and lens cases in China.Materials and Methods: A total of 107 RGP trial lenses and lens cases were collected from 7 main hospitals or optometric centers in China. Three sites including the lenses, case interiors and case screw tops were sampled for bacterial and fungal culture and identification. The contamination rates of these three sites and their relationship with lens care regimes were further analyzed.Results: The overall contamination rate was 73.8% for either lenses or cases, and 43.0% of lenses, 57.0% of case interiors and 65.4% of case screw tops respectively. The most frequently isolated microorganisms were Serratia spp., Burkholderia spp., Pandoraea spp., and Achromobacter spp. from all three sites. The contamination rate was positively related to the lens use frequency. Compared with dry-stored lenses, the contamination rate was significantly higher in wet-stored group (P < .001*). Inadequate disinfection and improper lens and case care regimes were also associated with higher contamination rates.Conclusions: Our study reported that the RGP trial lenses and cases used for fittings had a considerably high contamination rate. The safe use of RGP trial lenses and education of optometrists on the regular maintenance of trial lenses should be emphasized.

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.

Bacterial contamination of lens cases whilst using a povidone iodine based disinfection system

Bacterial contamination of lens cases whilst using a povidone iodine based disinfection system

Contact lens hygiene compliance and lens case contamination: A review.

A contaminated contact lens case can act as a reservoir for microorganisms that could potentially compromise contact lens wear and lead to sight threatening adverse events. The rate, level and profile of microbial contamination in lens cases, compliance and other risk factors associated with lens case contamination, and the challenges currently faced in this field are discussed. The rate of lens case contamination is commonly over 50%. Coagulase-negative Staphylococcus, Bacillus spp., Pseudomonas aeruginosa and Serratia marcescens are frequently recovered from lens cases. In addition, we provide suggestions regarding how to clean contact lens cases and improve lens wearers' compliance as well as future lens case design for reducing lens case contamination. This review highlights the challenges in reducing the level of microbial contamination which require an industry wide approach.

The effect of contact lens hygiene behavior on lens case contamination.

To assess the association between the levels of lens case contamination and lens wearers' hygiene behaviors. Contact lens wearers were surveyed for information on wearer demographics and contact lens hygiene behavior. Microbial analysis of lens cases was performed. Multivariate analysis was used to identify factors associated with contact lens storage case contamination. One hundred nineteen contact lens wearers responded. The mean (±SD) age of the participant was 32 (±1) years (range, 18 to 69 years). Seventy percent of the participants were female. Sixty-six percent of lens cases were contaminated (median, 25; range, 0 to 10⁷ colony-forming units [CFUs]). In the multivariate analysis, washing hands with soap and water (1.8 ± 2.0 log10 CFU/case) rather than just water or no washing was associated with lower levels of lens case contamination (2.4 ± 2.1 log10 CFU/case; p = 0.005). Lens cases received wet had higher levels of contamination than dry cases (1.5 ± 1.5 vs. 2.4 ± 2.5 log10 CFU/case; p = 0.015). Mismatching lens case and disinfecting solution was a risk factor for lens case contamination (p = 0.019). Lens wearers who had more than 2 years of wearing experience had higher levels of contamination than those who had less than 2 years of wearing experience (2.1 ± 2.1 vs. 1.1 ± 1.5 log10 CFU/case; p = 0.04). Major factors that can reduce lens case contamination were washing hands with soap and water, air-drying lens cases, and matching of the disinfecting solution with lens case (i.e., from the same manufacturer). This information is beneficial when advising lens wearers in clinical practice.

The Effect of Compliance on Contact Lens Case Contamination

To determine the efficacy of written instructions on contact lens case hygiene and to quantify the effect of noncompliance on contact lens case contamination. Data were retrospectively analyzed from 16 prospective, 3-month daily-wear studies during which six commercially available silicone hydrogel contact lenses and seven lens care solutions (LCS) were tested following a similar protocol. Verbal instructions regarding case hygiene (rinse case with LCS, not tap water) were given in nine studies, while the same instructions were given verbally and in written format in seven studies. A survey on contact lens, LCS, and lens case hygiene was completed at 1- and 3-month visits and compliance with case hygiene instructions was determined. Regular contact lens cases were used for 1 month and collected for microbial analysis at the 1- and 3-month visits. The rate of case contamination and the types of microbes contaminating cases were evaluated. Participants given verbal and written instructions were more likely to be compliant with case hygiene instructions than those just given verbal instructions (odds ratio [OR]: 2.19, p < 0.001, 95% confidence interval [CI]: 1.40-3.44). The overall case contamination rate was 79%. Use of tap water to rinse contact lens cases was associated with significantly more cases contaminated with Gram-negative bacteria (GNB) (30% vs. 10%, p < 0.001), a greater risk of GNB case contamination (OR: 2.91, p < 0.001. 95% CI: 1.72-4.92), and a higher quantity of GNB in cases (mean colony-forming unit/case ± SD: 28,286 ± 131,935 vs. 6477 ± 60,447, p < 0.001). Lens case hygiene can be improved by effective communication of instructions. Contact lens wearers should be actively discouraged from rinsing contact lens cases with tap water because of the increased risk of GNB contamination.

The effect of contact lens solutions on membrane permeability of Staphylococcus aureus aggregates

Purpose: Contact lens case contamination with biofilms occurs often due to the resistance of bacterial aggregates to the disinfectants in contact lens care solutions. Microbial keratitis and corneal infiltrates have been associated with the development of bacterial aggregates (biofilms) in lens cases. This study investigated the antimicrobial efficacy of contact lens solutions against Staphylococcus aureus aggregates by assessing the damage to the microbial membranes using fluorescent dyes and confocal microscopy.

Lens wearers non-compliance—Is there an association with lens case contamination?

This study aims to investigate the association of compliance amongst lens wearers and lens case contamination as assessed by the microbial profile of lens cases. Fifty-two asymptomatic lens wearers filled out questionnaires seeking demographic data and several aspects of compliance to lens wear. Subsequently, contamination profiles of the inside bottom and rim of their lens cases was obtained for bacteria, fungi and Acanthamoeba. The association of the self-reported responses in the questionnaire with contamination profile of the lens case was then analyzed. Based on compliance criteria, 21% of the participants were described as fully compliant lens wearers. Contamination of lens case was prevalent in 42% of the cases. Frequent non-compliant behaviours reported by study participants included, showering and sleeping with contact lenses, and irregular lens case replacement. In comparison to soft contact lens wearers prevalence of non-compliance and contamination amongst rigid gas permeable (RGP) lens wearers was significantly greater. There was a statistically significant correlation between bacterial contamination and current case age. These results suggest that majority of lens wearers do not fully comply with recommendations for lens wear and case care. Crucially, none of the fully compliant patients had contaminated lens cases. However it would appear that several non-compliant behaviours significantly increase the risks of case contamination. These results suggest that greater efforts should be invested with lens wearers to ensure enhanced compliance as this is likely to reduce the possibility of case contamination.

Solutions for Care of Silicone Hydrogel Lenses

During wear of contact lenses on a daily wear basis, it is necessary to disinfect the lens overnight before reinserting the lens the next day. The ability of the solutions used for this to disinfect lenses and lens cases is important for safe lens wear. The literature on the disinfecting ability of multipurpose disinfecting solutions (MPDS) commonly used with silicone hydrogel lenses reported during the period 2000 to 2012 is reviewed, as this is the period of time during which these lenses have been commercially available. Particular emphasis is placed on the ability of disinfecting solutions to control colonization of lens cases by microbes and changes in composition and use of the solutions. In addition, the literature is reviewed on ways of minimizing lens case microbial contamination. Maintaining the hygiene of contact lenses and lens cases is important in minimizing various forms of corneal infiltrative events that occur during lens wear. Although lens case contamination is not associated with different lenses, it is determined by use of different MPDS. MPDS that allow more frequent or heavy contamination of cases by Gram-negative bacteria are associated with a higher incidence of corneal infiltrative events. MPDS are now available that contain dual disinfectants. Wiping lens cases with tissues or using lens cases that incorporate silver are associated with reductions in contamination in clinical trials. Similarly, using MPDS to rub and rinse lenses before disinfection may reduce levels of microbes on lenses. The MPDS also contain surfactants that help reduce deposition and denaturation of proteins on lenses. Improvements in MPDS formulations and hygiene practices may help to reduce the incidence of adverse events that are seen during use with silicone hydrogel lenses.

Effect of a Warming Device on Contact Lens Case Contamination

To examine the effectiveness of heating contact lens cases after disinfection on reducing microbial contamination. One strain each of Pseudomonas aeruginosa (071) and Staphylococcus aureus (31) were used to set up robust biofilms in polypropylene contact lens cases. The effect of dilutions (from 1:10 to 1:1000) of trypticase soy broth (TSB) in phosphate-buffered saline and incubation time (24 to 48h) on the ability of strains to from biofilms with high levels of bacteria were first examined. Then the effect of increasing the temperature of incubation (from 14°C to 60°C) of biofilms during drying was examined. In the final set of experiments, biofilms of strains were subjected to heating in a warming device set to deliver 60°C for 3 hours, and the effect of this temperature after disinfection with a multipurpose disinfecting solution (MPDS; containing polyquat and Aldox) was examined by culturing the number of viable bacterial cells remaining. A dilution of 1:100 TSB for S. aureus 31 and 1:1000 TSB for P. aeruginosa 071 together with an incubation time of 24 hours gave high numbers of viable cells of these 2 strains adhered to the contact lens cases. Having established the biofilms of bacteria, heating these to 60°C for 3 hours resulted in significant reductions in the number of viable cells that could be cultured (1 log reduction for S. aureus 31, P=0.0003; 3.5 log reduction for P. aeruginosa 071, P=0.002). Exposing the biofilms of cells to a disinfection cycle (6h at ambient temperature) in the presence of the MPDS and air drying at ambient temperature resulted in 2441±1237 colony-forming units/lens well for S. aureus 31 and 7401±4374 colony-forming units/lens well for P. aeruginosa 071. Increasing the drying temperature to 60°C resulted in zero viable cells (i.e., ≥4log reduction) for either bacterial type. Using a warming device for contact lens cases after a disinfection cycle with an MPDS during drying for 3 hours results in substantial kill of biofilms of P. aeruginosa and S. aureus that have been formed in the wells of the cases.

Effect of Multipurpose Solutions on Cell Morphology and Cytokine Production by Corneal Epithelial Cells

We sought to determine whether human corneal limbal epithelial cells (HCLE) differ in their physiological response and production of inflammatory mediators during exposure to two multipurpose disinfecting solutions that differ in only four excipients. HCLE were exposed to dilutions (1%-20%) of OPTI-FREE Express and OPTI-FREE RepleniSH for 2, 6, or 18 h. Cell numbers were measured using CyQuant and metabolic activity assays. Morphology, viability, and apoptotic changes were examined by confocal microscopy after staining with Calcein AM/propidium iodide or Hoechst 33,342/propidiun iodide/YO-PRO-1. Cytokine responses and arachidonic acid metabolites were examined by enzyme-linked immunosorbent assay. OPTI-FREE Express showed greater reductions in corneal cell metabolic activity (up to 3-fold) than OPTI-FREE RepleniSH over 18 h. Cells exposed to OPTI-FREE Express were highly vacuolated, whereas those exposed to OPTI-FREE RepleniSH had morphology consistent with a presumed apoptotic response. OPTI-FREE Express elicited higher levels of interleukin (IL)-6 (maximum 4225 ± 300 pg/mL) and IL-8 (maximum 1094 ± 250 pg/mL) from cells than OPTI-FREE RepleniSH (maximum of 1717 ± 225 pg/mL and 930 ± 300 pg/mL, respectively) at all concentrations tested after 18 h. HCLE did not produce leukotriene B4 or prostaglandin E2 on stimulation, and IL-1β was produced in low levels, but its production was not different between multipurpose disinfecting solution types. The findings reported here are the first to describe the pattern of cytokine production produced in corneal epithelial cells in response to contact lens solutions. Alteration of only four excipients in the formulations had such effects on corneal epithelia; however, these differences do not explain differences in the incidences of corneal infiltrative events between these solutions. This might indicate that changes in the rates of infiltrative events result from interactions of the solutions with the contact lens surface, or directly with the corneal immune system, or as the result of gram-negative contamination of lens cases.

Impact of Lens Case Hygiene Guidelines on Contact Lens Case Contamination

Lens case contamination is a risk factor for microbial keratitis. The effectiveness of manufacturers' lens case cleaning guidelines in limiting microbial contamination has not been evaluated in vivo. This study compared the effectiveness of manufacturers' guidelines and an alternative cleaning regimen. A randomized cross-over clinical trial with two phases (n = 40) was performed. Participants used the lens types of their choice in conjunction with the provided multipurpose solution (containing polyhexamethylene biguanide) for daily wear. In the manufacturers' guideline phase, cases were rinsed with multipurpose solution and air dried. In the alternative regimen phase, cases were rubbed, rinsed with solution, tissue wiped, and air-dried face down. The duration of each phase was 1 month. Lens cases were collected at the end of each phase for microbiological investigation. The levels of microbial contamination were compared, and compliance to both regimens was assessed. The case contamination rate was 82% (32/39) in the manufacturers' guideline group, compared with 72% (28/39) in the alternative regimen group. There were significantly fewer (p = 0.004) colony forming units (CFU) of bacteria from cases used by following the alternative regimen (CFU range of 0 to 10, and median of 12 CFU per well) compared with that of the manufacturer's guidelines (CFU range of 0 to 10, and median of 28 CFU per well). The compliance level between both guidelines was not significantly different (p > 0.05). The alternative guidelines are more effective in eliminating microbial contamination from lens cases than that of the current manufacturer's guideline. Simply incorporating rubbing and tissue-wiping steps in daily case hygiene reduces viable organism contamination.

Impact of Air-Drying Lens Cases in Various Locations and Positions

To determine the rate and type of microbial contamination when contact lens cases are air-dried in two different positions (face up and face down) and in four different locations (toilet, bathroom, office, and bedroom). Unused contact lens cases (n = 97) were rinsed with 2-ml sterile phosphate buffered saline and then placed on facial tissue paper in different locations: humid (toilet and bathroom) and non-humid (office and bedroom) and air-dried at room temperature. After 24 h, the contact lens cases were collected and sampled for microbial numbers and microbial types identified using standard techniques. The microbial profile and the rate of contamination between different locations and positions were compared. Irrespective of the air-drying location, contact lens cases positioned face up had a significantly higher contamination rate (34/48, 71%) compared with contact lens cases air-dried face down (6/49, 12%) (p < 0.001). For those contact lens cases air-dried face up, there was more contamination when placed in humid environments (toilet and bathroom) than in the non-humid environments (office and bedroom) (p = 0.01). However, the contact lens case contamination rate among various locations was similar when contact lens cases were air-dried face down. Total microorganisms recovered from contact lens cases ranged from 0 to 275 colony forming unit per well. The most frequently recovered microorganisms from the contaminated contact lens cases were coagulase-negative Staphylococci, fungi, and Bacillus spp. Thirty-three percent (13/40) of contact lens cases were contaminated with multiple species. Small numbers of microorganisms from the environment may contaminate contact lens cases while cases are air-dried face up. Cases air-dried in humid environments have higher levels of microbial contamination; this is particularly true when contact lens cases are positioned face up. On the basis of this limited study, we would recommend contact lens cases be air-dried face down.

Contact Lens Case Contamination During Daily Wear of Silicone Hydrogels

Contamination of contact lens cases has been associated with the production of adverse responses in the eye during contact lens wear. This study aimed to evaluate the contamination rate and types of microbes contaminating cases during use of contact lens disinfecting solutions and silicone hydrogel lenses. Two hundred thirty-two participants were allocated to one or more groups. The participants wore one or more of three silicone hydrogel lenses and used one or more of four contact lens disinfecting solutions. Cases were collected after use for 1 month and sent for routine microbial testing. The rate of contamination of cases and the types of microbes contaminating cases were evaluated. Between 76 and 92% of all cases were contaminated. Use of different contact lenses did not affect contamination rate or the types of microbes isolated from cases. Use of AQuify (PHMB as disinfectant) was associated with the highest contamination rate (92%; p = 0.015) of cases for any microbe. Level and type of contamination with use of ClearCare (H2O2) was similar to use of PHMB (polyhexamethylene biguanide)- or Polyquat/Aldox-containing solutions. There was no difference in contamination rate of cases by fungi or Gram-positive bacteria, but for Gram-negative bacteria, use of Opti-Free Express (Polyquat and Aldox as disinfectants) resulted in a lower contamination rate (7% vs. 29 to 45%; p < 0.001). The average number of microbes contaminating a case was significantly less for Opti-Free Express (223 +/- 1357 cfu/case) compared with Opti-Free RepleniSH (Polyquat and Aldox as disinfectants; 63,244 +/- 140,630 cfu/case; p < 0.001), driven mostly by differences in numbers of Gram-negative bacteria, particularly contamination by Delftia acidovorans in cases exposed to Opti-Free RepleniSH. Different disinfecting solutions used during storage in cases result in different levels of contamination and contamination by different types of microbes. These differences are not simply because of the types of disinfectants used, suggesting that other excipients in, or formulation of, the solution affect contact lens storage case contamination.

Contact Lens Cases: The Missing Link in Contact Lens Safety?

To summarize a variety of issues associated with contact lens case contamination and discuss appropriate methods that can limit this. A literature review was undertaken investigating the major factors associated with case contamination, with specific reference to the major pathogens associated with contamination, the role of bacterial biofilms, and methods that can limit contamination. The use of antimicrobial cases, regular case cleaning and case replacement, avoidance of topping up solutions, and not using tap water to rinse cases all appear to be important in avoidance of significant case contamination. Contact lens case contamination is a significant public health concern and may contribute significantly to the development of microbial keratitis in contact lens wearers. Patients should be reminded that they must clean and disinfect their lens cases daily, should avoid the use of tap water for rinsing them, must not top up their solutions, must take into careful consideration where and how the cases are stored during the time that lenses are being worn and that they must be replaced regularly. The adoption of these methods will substantially reduce the levels of contamination of cases with pathogenic microbes.

Dark secrets behind the shimmer of contact lens : the Indian scenario

BackgroundWe studied the bacteriological profile of soft contact lens and its accessories among the asymptomatic subjects and monitored the compliance level with the lens use and its cleaning protocol.FindingsA total of 115 (104 daily wear and 11 extended wear) subjects using contact lens were studied. Data regarding the duration of use and frequency and method of cleaning were recorded. Contact lens, lens cases, preserving solutions and tips of solution bottles were the samples collected. The isolates were identified on the basis of their phenotypic characters. Samples from 24 subjects (21 daily wear and 3 extended wear) were found contaminated. Of the 24 contaminated cases, 23 showed medium adherence to the cleaning protocol. Contamination rate was higher among the 56 daily wear lens users who used same lens for 2 years and more, than the 48 users who used their lenses for less than 2 years. Lens case contamination was found in all the 24 cases. The bacteria isolated were Citrobacter freundii, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus epidermidis and Streptococcus pneumoniae. In extended wear lens users, there was no change in microbial flora on repeating the cultures on day 7 and 14.ConclusionNon-compliance with contact lens use may lead to invitation of microbial flora. The accumulation of these bacteria may act as a precursor to biofilm formation, thus colonizing the lens accessories as well. The bacteria isolated in this study were similar to the ones causing microbial keratitis thus, predisposing the otherwise asymptomatic subjects to permanent visual damage.