Microbial contamination of contact lens cases in the west of Scotland

Assessment of patient compliance in orthokeratology and analysis of influencing factors: a cross-sectional study

Background

Patient non-compliance, that is, failure to perform standard wear and care orthokeratology (ortho-k) lenses procedures, has been shown to be a major risk factor for contact lens-associated complications. Therefore, this study aimed to investigate the compliance with wear and care behaviors of ortho-k patients and analyze its influencing factors.

Methods

Patients who were successfully prescribed ortho-k lenses at the Eye Center of the Second Affiliated Hospital of Zhejiang University School of Medicine (ECSAHZU) were enrolled in the study. Patient compliance with wear and care behaviors was examined through a questionnaire.

Results

This study assessed 238 subjects. The subjects’ ages ranged from 7 to 25 (mean ± SD, 11.3 ± 2.5) years. The compliance with wear and care behaviors was 19.7%, and the subjects’ self-assessment compliance was 96.6%. The compliance rate of subjects wearing lenses for less than 1 year was higher than that of subjects wearing lenses for more than 1 year (p < 0.001). In the first year, the compliance rates of wearing experiences for less than 1 month, 1 month, 3 months, 6 months, and more than 6 months were 45, 29, 21.6, 20, and 27.6%, respectively, and there were no statistically significant differences in compliance among these periods (p = 0.314). No correlation was identified between compliance and age (r = − 0.061, p = 0.527) or sex (r = 0.114, p = 0. 751). There was no correlation between compliance and lens care operator (r = − 0.626, p = 0.151).

Conclusions

The compliance of ortho-k patients was poor. After wearing ortho-k lenses for more than 1 year, compliance with wear and care behaviors declined. In clinical practice, measures should be taken to solve these problems and improve the safety of wearing ortho-k lenses.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-021-02148-2.

Exploring microwave irradiation as a method to disinfect contact lens cases

PURPOSE

Biofilm formation caused by infrequent contact lens case replacement and the ineffectiveness of multi-purpose solutions (MPS) on biofilm removal is associated with high rates of bacterial keratitis infections. This study demonstrated biofilm elimination from the contact lens case by microwave irradiation.

METHODS

Staphylococcus aureus biofilms indicative of 3-9 months of contact wear were cultured in contact lens cases and visualized with crystal violet (CV) staining. Biofilms in contact cases were then exposed to four treatment regimens: No treatment (n = 8), 45 s microwave irradiation (n = 8), tap water (n = 6), and MPS (n = 9). Bacterial survival was assessed by colony forming unit (CFU) assay using streak dilutions.

RESULTS

Visualization of the biofilms through CV staining revealed that biofilms coalesce between ribs of the contact case. In 5/8 cases no CFU were cultivated from the case after treatment with microwave irradiation. In tap water and MPS the first dilution averaged 6 ± 2 and 31 ± 13 CFUs per plate, respectively, while microwave irradiation averaged < 1 CFU per plate. In Dilution 2, the average reduced to 0.7 ± 0.7 and 6 ± 5 CFUs per plate for tap water and MPS, respectively, while microwave irradiation had 0 CFUs in Dilution 2.

CONCLUSION

Biofilms that coalesce between the ribs of the contact case pose a threat because this area is difficult to thoroughly scrub and could act as a basis for infection through fouling of contact lenses. Of the four treatment regimens, microwave irradiation displayed the most consistent and highest rate of bacterial eradication. Tap water was less effective compared to microwave irradiation, and poses other harmful side effects, but greatly reduced CFU count compared to no treatment. MPS displayed the poorest bacterial eradication of the treatments. Thus, microwave irradiation is worth further investigation as a viable in-home disinfecting option.

Contact Lens- and Patient-related Factors Associated with Contact Lens Discomfort among Contact Lens Wearers in an African Cohort

SIGNIFICANCE

No information is available on contact lens discomfort in any African population. Such information may be helpful in developing the scope and priorities for intervention.

PURPOSE

The purpose of the study was to examine contact lens- and patient-related factors associated with contact lens discomfort among wearers in Ghana.

METHODS

In this multicenter cross-sectional study, contact lens wearers 18 years and older were recruited. The Contact Lens Dry Eye Questionnaire-8 and a standardized scripted interview were administered to 72 contact lens wearers at five clinical sites, and 40 participants' lens storage cases were collected and cultured. A variety of patient- and contact lens-related factors were examined. Univariate and multivariate logistic regression modeling were used to assess risk factors associated with contact lens discomfort.

RESULTS

Seventy-two contact lens wearers aged 18 to 45 years completed the study. The mean age was 27.5 ± 6.4 years, 65.3% of them were females, 86.1% wore soft contact lens, and 13.9% wore rigid gas-permeable lens. Contact lens discomfort was reported by 66.7% of the subjects. Most frequent lens storage cases isolates were Bacillus species (40%) and fungi (31.1%). Significant association was found between disinfecting with tap water (5.98; 95% confidence interval [CI], 1.22 to 29.27; P = .03), heavy visual display terminal use (3.39; 95% CI, 1.01 to 11.34; P = .05), high water content (1.16; 95% CI, 1.02 to 1.33; P = .03), and contact lens discomfort. Demographic factors, wear modality, and care solutions were not significant (all P > .05).

CONCLUSIONS

In considering the use of contact lenses for refractive correction in this population, strategies for preventing contact lens discomfort that should be targeted include use of low-water-content lenses, disinfecting with multipurpose solutions, and reducing the time spent daily on visual display terminal use.

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

SIGNIFICANCE

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.

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

Contact lens users should be recommended to tissue-wipe and air-dry their lens storage cases after disinfection with regular MPDS.

The effect of a compliance enhancement strategy (self‐review) on the level of lens care compliance and contamination of contact lenses and lens care accessories

PURPOSE

The aims were to determine the level of compliance of contact lens wearers, to identify which procedures have highest levels of non-compliance and to study the effectiveness of a compliance enhancement strategy on the level of compliance.

METHODS

The level of compliance for each subject was evaluated with a self-administered questionnaire together with microbiological examination of their contact lenses, lens cases and lens care solutions. The effect of an intervention to improve the level of compliance was determined by a controlled trial. A regular self-review exercise on proper lens handling was given to the test group once every three months for 12 months. The levels of compliance and contamination of contact lenses and lens care accessories between test and control groups were compared at the end of the 12-month period to evaluate the effect of the intervention.

RESULTS

Sixty-five subjects who were experienced contact lens wearers were recruited and 60 completed the study. All showed some degree of non-compliance in the care of their contact lenses and lens accessories. Most (about 60 per cent) were non-compliant with at least six of a total of 15 lens care procedures. The most common non-compliant behaviour among contact lens wearers was associated with the care of the lens case. By the end of the study period, our compliance enhancement strategy did not appear to have had a significant effect on the behaviour of our subjects, except for improvement in the care of lens cases. Compliance for other procedures improved in both test and control groups.

CONCLUSION

All subjects showed some degree of non-compliance and the spectrum of non-compliance was wide. The poorest levels of compliance were associated with care of the lens case, which was also the most frequently contaminated item. Our compliance enhancement strategy showed a significant difference in improvement in compliance between the intervention and control groups only in the care of lens cases.

Gas-Permeable Contact Lenses and Water Exposure: Practices and Perceptions

SIGNIFICANCE

This study provides insight into the current recommendations, clinical behaviors, and risk assessments of eye care professionals on the topic of rigid contact lens exposure to tap water. This knowledge may motivate professional organizations to develop initiatives to educate eye care professionals on the dangers of contact lens exposure to water.

PURPOSE

The purpose of this study was to investigate the practice patterns and risk perceptions of eye care professionals regarding gas-permeable contact lens exposure to tap water.

METHODS

A branched-logic survey was started by 320 clinicians, vision scientists, and industry personnel and was fully completed by 272 participants. The survey queried participants about their current practices, recommendations, and perceptions of risk regarding exposure of gas-permeable contact lenses to tap water.

RESULTS

Of those who prescribe gas-permeable contact lenses, 57.4% reported rinsing lenses with tap water, whereas only 32.7% reported engaging in this same behavior in front of patients. Of those who reported never rinsing lenses with tap water, 85.6% indicated that rinsing lenses with water increases infection risk, whereas 52.1% of those who rinse lenses with water reported the same perceived risk (P < .001). Of all participants, 60% indicated that wearing contact lenses while showering increases infection risk, and 50.2% of all participants advised patients to avoid this behavior.

CONCLUSIONS

A discrepancy exists between perceptions of risk concerning exposure of contact lenses to water and both clinical practices and patient education provided by professionals.

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

PURPOSE

To 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.

METHODS

Participants, 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.

RESULTS

Of 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.

CONCLUSIONS

Disinfection 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.

Development of a contact Lens risk survey

PURPOSE

To describe the development and report psychometric properties of the Contact Lens Risk Survey (CLRS) to identify patients at risk for soft contact lens-related complications.

METHODS

Psychometric properties of the CLRS, a web-based survey with branching logic, were determined using data from 5 multi-site fieldings (n = 1059), including re-fielding to sub groups. Responses from participants with and without an active red eye were used to identify risk factors of a red eye event and calculate an overall risk score. A 6th fielding of the CLRS (n = 171) was used to assess discriminate validity.

RESULTS

Participants needed 11-12 min to complete the survey with a negligible difference by age. Internal consistency was excellent (Cronbach's α ≥ 0.70) for 3 of the 5 constructs identified by factor analysis. Twelve of the 17 survey items exhibited excellent within-subject repeatability (Kappa ≥ 0.61). Between-subject agreement, assessed in 18-25 year olds, was high for the majority of items, suggesting good generalizability across different populations of SCL wearers. The ability of the model using individual items of the CLRS to discriminate Controls and participants with a red eye was good with an area under the curve of 0.779.

CONCLUSION

The CLRS tool is a repeatable and valid instrument to standardize documentation of demographic, behavior, and exposure factors which appear to drive the greatest risk of a contact lens related red eye event.

Microbiome analysis of contact lens care solutions and tear fluids of contact lens wearers: Possible involvement of streptococcal antigens in allergic symptoms related to contact lens wear

The present study elucidated the pathogenesis of allergic symptoms (AS) related to contact lens (CL) wear by assaying CL care solutions in lens storage cases and tears from subjects with AS using molecular biology techniques. A total of 15 CL storage cases were collected from subjects with AS (n=9) and healthy, asymptomatic control CL wearers (n=6). Bacterial populations in CL care solutions and tears were assayed by culture and 16S rDNA sequencing. Histamine levels in tears were measured by high-performance liquid chromatography. Western blot analysis was performed to identify the bacteria recognized by tear IgE from subjects with AS. No significant differences were found in the culture results between the subjects with AS and asymptomatic subjects. Histamine was detected in 2 subjects with AS. Meta-16S rDNA sequencing identified a cluster of 4 subjects with AS that were distinguished from others by principal coordinate analysis. Detailed population analysis revealed that the abundance of Gram-positive bacteria in the microbiomes of CL care solutions used by the subjects with AS were higher than those of asymptomatic subjects (42.24±9.47 vs. 16.85±22.76% abundance). Among these, Streptococcus was the dominant genus (12.1-18.3% abundance). Tear microbiome analysis revealed that the abundance of Streptococcus in the subjects with AS was significantly higher than that in other subjects (19.02±5.50 vs. 3.08±3.35%, P<0.01). Western blot analysis demonstrated that the tear IgE in all subjects with AS reacted with Streptococcus (100%), but not with Staphylococcus. On the whole, these results provide novel insight into the pathogenesis of AS and identify Streptococcus as an important factor in AS associated with CL wear.

Acanthamoeba Keratitis: Current Status and Urgent Research Priorities

Background:

First discovered in the early 1970s, Acanthamoeba keratitis has remained a major eye infection and presents a significant threat to the public health, especially in developing countries. The aim is to present a timely review of our current understanding of the advances made in this field in a comprehensible manner and includes novel concepts and provides clear directions for immediate research priorities.

Methods:

We undertook a search of bibliographic databases for peer-reviewed research literature and also summarized our published results in this field.

Results:

The present review focuses on novel diagnostic and therapeutic strategies in details which can provide access to management and treatment of Acanthamoeba keratitis. This coupled with the recently available genome sequence information together with high throughput genomics technology and innovative approaches should stimulate interest in the rational design of preventative and therapeutic measures. Current treatment of Acanthamoeba keratitis is problematic and often leads to infection recurrence. Better understanding of diagnosis, pathogenesis, pathophysiology and therapeutic regimens, would lead to novel strategies in treatment and prophylaxis.

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

Purpose

We evaluate the in vitro antibacterial activity of silver-copolymerized barrel cases compared to nonsilver barrel cases in combination with a multipurpose disinfecting solution (MPDS).

Methods

The 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.

Results

Significantly 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.

Conclusions

Silver-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 Relevance

Silver-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.

Level of Compliance in Orthokeratology

OBJECTIVES

To investigate the level of compliance with orthokeratology (ortho-k) guidelines and the main behaviors of poor compliance to guide clinical care.

METHODS

A questionnaire was sent to ortho-k patients in the Eye Hospital of Wenzhou Medical University (EHWMU) in Mainland China who were prescribed ortho-k lenses after January 2013 and have worn ortho-k lenses for more than 1 year to determine the compliance rate for eight wear and care behaviors. Follow-up visit compliance was then investigated among these patients using a retrospective survey.

RESULTS

A total of 1,500 questionnaires were distributed, and 405 patients responded. The mean age of the patients was 13.1±3.9 years (range 9-22 years); 60.5% of the patients were female, and 98.3% were younger than 18 years. The full compliance rate was 14.1%, the compliance rate for wear and care behaviors was 18.5%, and the compliance rate for follow-up visits was 63.3%. The three highest noncompliance categories for wear and care behaviors were exposure to nonsterile solution, not removing lens depositions according to the eye care practitioners' (ECPs) recommendations and inadequate hand washing. No correlation was observed between the compliance for wear and care behaviors and age, sex, and wearing experience. The follow-up visit compliance rate significantly decreased from the third month to the ninth month. The common reasons for discontinuing follow-up were lack of time, no symptoms, and inconvenience.

CONCLUSIONS

The level of compliance with ortho-k lens wear in Mainland China is not high, necessitating ECPs to stress to patients the details of wear and care behaviors, especially avoiding exposing lenses to nonsterile solution. Improving monitoring of follow-up visits, particularly within the first 9 months of wearing ortho-k lenses, is needed.

Bacterial Coaggregation and Cohesion Among Isolates From Contact Lens Cases

Purpose

The aim of this study was to examine cohesion, coaggregation, and coculture between bacteria commonly isolated from contact lens cases.

Methods

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.

Results

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.

Conclusions

Coaggregation, cohesion, and growth promotion may facilitate the process of bacterial colonization of contact lens cases.

Multicenter Testing of a Risk Assessment Survey for Soft Contact Lens Wearers With Adverse Events: A Contact Lens Assessment in Youth Study

PURPOSE

To test the ability of responses to the Contact Lens Assessment in Youth (CLAY) Contact Lens Risk Survey (CLRS) to differentiate behaviors among participants with serious and significant (S&S) contact lens-related corneal inflammatory events, those with other events (non-S&S), and healthy controls matched for age, gender, and soft contact lens (SCL) wear frequency.

METHODS

The CLRS was self-administered electronically to SCL wearers presenting for acute clinical care at 11 clinical sites. Each participant completed the CLRS before their examination. The clinician, masked to CLRS responses, submitted a diagnosis for each participant that was used to classify the event as S&S or non-S&S. Multivariate logistic regression analyses were used to compare responses.

RESULTS

Comparison of responses from 96 participants with S&S, 68 with non-S&S, and 207 controls showed that patients with S&S were more likely (always or fairly often) to report overnight wear versus patients with non-S&S (adjusted odds ratio [aOR], 5.2; 95% confidence interval [CI], 1.4-18.7) and versus controls (aOR, 5.8; CI, 2.2-15.2). Patients with S&S were more likely to purchase SCLs on the internet versus non-S&S (aOR, 4.9; CI, 1.6-15.1) and versus controls (aOR, 2.8; CI, 1.4-5.9). The use of two-week replacement lenses compared with daily disposables was significantly higher among patients with S&S than those with non-S&S (aOR, 4.3; CI, 1.5-12.0). Patients with S&S were less likely to regularly discard leftover solution compared with controls (aOR, 2.5; CI, 1.1-5.6).

CONCLUSIONS

The CLRS is a clinical survey tool that can be used to identify risky behaviors and exposures directly associated with an increased risk of S&S events.

Bacterial Bioburden Decrease in Orthokeratology Lens Storage Cases After Forewarning: Assessment by the DNA Dot Hybridization Assay

Background:

The aim of this study was to measure the changes in the bacterial bioburden in orthokeratology (OK) lens storage cases using the DNA dot hybridization assay (DHA) after forewarning patients about their bacterial contamination severity.

Methods:

Thirty-one OK lens wearers were prospectively enrolled in this study. Dot hybridization assay was used for serial measurements of bacterial bioburden in OK storage cases after lenses had been soaked for approximately 6 hr. After the first assessment, the lens wearers were informed of the extent of case contamination and the possible risk of microbial keratitis (MK), and best practices for lens care and lens case hygiene were reviewed and reinforced. A second assessment by the same DHA method was performed after approximately 6 months.

Results:

Two universal bacterial probes confirmed a significant decrease in bacterial bioburden at the second assessment (P<0.01 and P<0.001). Genus-specific probes showed significant reductions in Acinetobacter and Klebsiella (P=0.02 and P=0.01), but not in Pseudomonas (P=0.42).

Conclusions:

Making OK lens wearers aware of the bacterial bioburden in their lens cases resulted in improved quality of case care and reduced bioburden. Our results suggest that a strategy of bioburden assessment with forewarning could be a useful method to decrease the incidence of OK-related MK.

Microwave Irradiation as a Promising Method of Sterilization for Acanthamoeba polyphaga in Cultures

PURPOSE

To determine the killing effect of microwave irradiation on Acanthamoeba polyphaga.

METHODS

The trophozoites and cysts of A. polyphaga both in water and on agar were exposed to microwave irradiation with a capacity of 750 W for 0, 1, 3, 5, and 10 minutes, respectively. Furthermore, the trophozoites and cysts of A. polyphaga in water were exposed to microwave irradiation with a capacity of 100, 300, and 500 W for 1 minute, respectively.

RESULTS

The trophozoites and cysts of A. polyphaga on agar were completely killed by 3 minutes of microwave irradiation with a capacity of 750 W. The trophozoites and cysts of A. polyphaga in water were completely killed by microwave irradiation with a capacity of 300 W for 1 minute.

CONCLUSIONS

We demonstrate that microwave treatment is effective in killing A. polyphaga both in water and on agar and may be a helpful modality to prevent Acanthamoeba keratitis.

PCR analysis for assessment of bacterial bioburden in orthokeratology lens cases

PURPOSE

To develop a PCR gel analysis method for assessing the bacterial bioburden in orthokeratology contact lens (OK) case fluid determined by culture.

METHODS

A prospective study with the participation of 41 OK wearers (20 girls, 21 boys) was performed. The mean OK-wearing experience was 3.5±1.9 years. PCR was used to assess the bacterial bioburden (colony-forming units per milliliter) of OK after removal and soaking in the storage case for 6 h. The signal intensity of the PCR bands was analyzed after grayscale image transformation. The difference (cPCR-d) and ratio (cPCR-r) between a PCR signal and its background were used as two standardized indices of PCR signals. The association between the two indices of the PCR signals and the bacterial bioburden determined by culture were analyzed with Pearson's correlation coefficient (r) and receiver operating characteristic (ROC) plots.

RESULTS

At least one microbe was isolated from the OK lens case from 38 of the 41 subjects. Both cPCR-d and cPCR-r showed strong correlations with the bacterial bioburden (r>0.7, p<0.0001). ROC analysis enabled good determination of the cutoff values for the two PCR indices with acceptable sensitivity and specificity (78-89%) to assess the degree of bacterial contamination.

CONCLUSIONS

The high microbial contamination rate of the OK lens cases revealed the general inappropriate lens care by OK wearers. PCR analysis provides an alternative and rapid method for assessing the bacterial bioburden of OK lens cases, and these results should serve as a warning to OK wearers to follow appropriate lens care procedures to prevent infection.

Acanthamoeba keratitis: improving the Scottish diagnostic service for the rapid molecular detection of Acanthamoeba species

Acanthamoeba species are responsible for causing the potentially sight-threatening condition, Acanthamoeba keratitis, which is commonly associated with contact lens use. In this report, we highlight the challenges faced using conventional laboratory identification methods to identify this often under-reported pathogen, and discuss the reasons for introducing the first national service in Scotland for the rapid and sensitive molecular identification of Acanthamoeba species. By comparing culture and molecular testing data from a total of 63 patients (n = 80 samples) throughout Scotland presenting with ocular eye disease, we describe the improvement in detection rates where an additional four positive cases were identified using a molecular assay versus culture. The testing of a further ten patients by confocal imaging is also presented. This report emphasizes the importance of continuing to improve clinical laboratory services to ensure a prompt, correct diagnosis and better prognosis, in addition to raising awareness of this potentially debilitating opportunistic pathogen.

Contact Lens Care among Teenage Students in Italy: A Cross-Sectional Study

AIM

To assess the attitude and practice of contact lens (CL) wearers among teenage school students and to evaluate how much the teenagers adhere to the CL care procedures according to the proper care of CL guidelines.

METHODS

A cross-sectional descriptive study of Italian teenagers from high schools in Rome who wear CL. We inquired about the different aspects of CL care through a questionnaire.

RESULTS

We investigated 3,106 students from high schools in Rome (2% of all Roman high school students), 293 of whom wore CL (9%); 151 (52%) of participants responded, 42 (27.8%) male and 109 (72.8%) female. The mean age was 16.4 ± 1.6 years. 79.5% of students were daily users. 45.7% wore CL more than nine hours/day. 87.4% wore soft CL. 33.1% wore disposable CL; 7.9% weekly CL, 55% monthly CL. Thirty-four percent wore disposable lenses twice or more. 14.5% of students did not wash their hands before handling CL and 52.3% wore CL after it had fallen in the sink. 39.7% rubbed and cleaned CL before storing it. 10% used expired lens care solutions. Only 31.1% changed CL cases every three months. 38.4% wore CL in a swimming pool. 61.6% were having problems: redness (13.9%), itching (7.9%), and foreign body sensation (29.1%).

CONCLUSION

Many students don't properly care for their CL. Education regarding proper care and management of CL among users is advised in view of frequency of symptoms and complications reported.

Microbial contamination of soft contact lenses & accessories in asymptomatic contact lens users

BACKGROUND & OBJECTIVES

With increasing use of soft contact lenses the incidence of contact lens induced infections is also increasing. This study was aimed to assess the knowledge of new and existing contact lens users about the risk of microbial contamination associated with improper use and maintenance of contact lenses, type of microbial flora involved and their potential to cause ophthalmic infections.

METHODS

Four samples each from 50 participants (n=200) were collected from the lenses, lens care solutions, lens care solution bottles and lens cases along with a questionnaire regarding their lens use. The samples were inoculated onto sheep blood agar, Mac Conkey's agar and Sabouraud's dextrose agar. Organisms were identified using standard laboratory protocols.

RESULTS

Overall rate of microbial contamination among the total samples was 52 per cent. The most and the least contaminated samples were found to be lens cases (62%) and lens care solution (42%), respectively. The most frequently isolated contaminant was Staphylococcus aureus (21%) followed by Pseudomonas species (19.5%). Majority (64%) of the participants showed medium grade of compliance to lens cleaning practices. Rate of contamination was 100 and 93.75 per cent respectively in those participants who showed low and medium compliance to lens care practices as compared to those who had high level of compliance (43.75%) (P<0.05).

INTERPRETATION & CONCLUSIONS

Lens care practices amongst the participants were not optimum which resulted into high level contamination. Hence, creating awareness among the users about the lens care practices and regular cleaning and replacements of lens cases are required.

Microbial contamination of contact lens care accessories and compliance with care regimens in Nepal

PURPOSE

To determine the rates of microbial contamination and identify contaminants associated with contact lens (CL) care accessories. To investigate self-reported compliance levels with care of CL accessories and its association with contamination level.

METHODS

A total of 46 CL cases and care solutions from asymptomatic soft contact lens wearers were collected. Samples from the CL cases and care solutions were cultured for microbiological identification and enumeration. A questionnaire regarding compliance to care and hygiene procedures were administered to each subject on their visit.

RESULTS

The percentage of microbial contamination for CL cases and care solutions was 50% and 10.9%, respectively. All the contaminants were bacterial. Staphylococcus aureus (37.0%, 17 of 46 cases) and Escherichia coli (8.7%, 4 of 46 cases) were the most common microorganisms detected in CL cases. In care solutions, S. aureus (8.7%, 4 of 46 samples), Pseudomonas aeruginosa (2.2%, 1 of 46 samples) were common contaminants. CL cases and care solutions that were used for <3 months were significantly less contaminated than those used for >3 months (10.9% versus 39.1%, p<0.05). Polyquad and Aldox based MPS solution showed no contamination. Subjects with medium or low compliance had highly significant rates of contaminations both in CL cases and solutions than for subjects with high compliance (p<0.05).

CONCLUSIONS

Nepalese Soft CL wearers are at high risk of developing ocular complications due to high CL case and solution contamination. Frequent replacement of CL cases and solutions, as well as good compliance is recommended to reduce risk of contamination.

Amoebicidal effects of contact lens disinfecting solutions

PURPOSE

To compare the traditional manual hemacytometer method and an automated counter (Vi-cell) to enumerate and distinguish between viable and non-viable amoeba, and to determine the efficacies of contact lens (CL) disinfecting solutions against three species of Acanthamoeba. The efficacies in the presence of a bacterial food source and bovine serum albumin (BSA) were investigated.

METHODS

Four brands of multipurpose solutions and a hydrogen peroxide disinfecting system (Oxysept) for soft CLs, and four disinfecting solutions for Rigid Gas Permeable (RGP) lenses were tested against three species of Acanthamoeba. Page's amoebic saline was included as a negative control and standard solutions of disinfecting agents, 6% hydrogen peroxide and 0.5% chlorhexidine, as positive controls. The effects of the presence of Pseudomonas aeruginosa and BSA on effectiveness were assessed.

RESULTS

None of the CL solutions tested achieved a 1-log reduction in viability of all three Acanthamoeba species within the manufacturer's recommended disinfection times. The presence of P. aeruginosa did not significantly affect disinfecting capacity of multipurpose solution solutions but reduced activity of RGP solutions and the hydrogen peroxide system. BSA reduced trophozoicidal activity of all solutions. Bland and Altman analysis showed good agreement between Vi-cell and hemacytometer.

CONCLUSIONS

The Vi-Cell analyzer offers a simple and effective method of determining amoebicidal activity. Our results show that the CL solutions tested could not satisfactorily kill Acanthamoeba.

Non-compliance with contact lens wear and care practices: a comparative analysis

PURPOSE

To compare the effects of existing patient awareness of lens-related complications and underlying risk factors on actual patient behavior during contact lens wear and care practices in two different clinical study populations.

METHODS

Established contact lens wearers (n = 281) completed an anonymous written questionnaire on presenting to their habitual eye care practitioner in the Dallas-Fort Worth metroplex. Data were analyzed and compared against a second study population, which comprised established contact lens wearers (n = 152) who were sequentially evaluated after their routine contact lens examination at the University of Texas Southwestern Medical Center at Dallas, TX (UTSW). All patients were questioned regarding his or her lens care practices and knowledge of complications and risk factors associated with contact lens wear.

RESULTS

Fifty-eight percent of patients in the general community could identify by name a complication associated with lens wear compared with 91% within the medical center. The most frequent complications reported were related to comfort and handling (72%, Dallas-Fort Worth) and infection (47%, UTSW). The majority of patients could correctly identify risk factors associated with lens-related complications; awareness for topping-off solutions, tap water exposure, and hygiene varied between groups. Overall, 85% of patients perceived themselves as compliant with their lens wear and care practices. Using a standard scoring model to determine actual compliance, 2% of patients demonstrated good compliance; however, only 0.4% of patients were fully compliant with contact lens wear and care practices.

CONCLUSIONS

The data reveal some study bias in complication and risk awareness between populations; however, despite this limitation, a significant proportion of patients exhibited actual non-compliant behavior despite acknowledged awareness of risk. Although most patients consider themselves to be complying with standard practitioner guidelines for lens wear and care practices, essentially all contact lens wearing patients exhibit behavioral non-compliance with resulting increased risk for significant complications.

Salicylate inhibition of acanthamoebal attachment to contact lenses

PURPOSE

Sodium salicylate has shown potential as a component of contact lens care solutions designed to reduce Acanthamoebal attachment to contact lenses. This study determined the minimum effective concentration required to significantly reduce amoebal attachment.

METHODS

Different concentrations of sodium salicylate (10, 15, and 20 mM) were applied during exposure of unworn or bacterial biofilm-coated hydrogel contact lenses to Acanthamoeba castellanii trophozoites. Salicylate was applied at stage 1 intervention during biofilm formation on lenses, at stage 2 intervention during amoebal exposure, or at both stages.

RESULTS

A significant reduction in amoebal attachment was achieved when 10 mM salicylate was included during stage 1 alone; however, 15 mM was required for stage 2 intervention to significantly reduce attachment to clean or biofilm-coated lenses. For stages 1 and 2 combined intervention, 10 mM sodium salicylate produced a significant reduction in amoebal attachment.

CONCLUSIONS

In situ, within a contact lens case, biofilm formation and amoebal attachment would occur concurrently; therefore, stages 1 and 2 intervention would be closest to the real-life situation, thus indicating that 10 mM of salicylate would be an effective minimum concentration for reducing amoebal attachment to hydrogel contact lenses. Inclusion of components in contact lens care solution, such as sodium salicylate, which reduce Acanthamoebal attachment, has the potential to enhance effectiveness, particularly where amoebicidal efficacy may be limited, thus reducing the risk of contact lens-associated Acanthamoebal infection.

The impact of cellular debris on Pseudomonas aeruginosa adherence to silicone hydrogel contact lenses and contact lens storage cases

OBJECTIVES

To evaluate neutrophil-enhanced Pseudomonas aeruginosa (PA) biofilm formation on silicone hydrogel contact lenses and to determine the effect of epithelial biodebris on PA adherence in contact lens storage cases.

METHODS

A fully invasive PA corneal isolate stably conjugated to green fluorescent protein was used. Unworn lotrafilcon A contact lenses were incubated at various ratios of PA to polymorphonuclear neutrophil (PMN) for 24 hours at 37°C. Lens-associated PA was evaluated using laser scanning confocal microscopy and nonviable PA were visualized using propidium iodide. Viable bacteria were enumerated by colony-forming unit (CFU) analysis. For acute epithelial cell studies, PA viability was determined after coincubation with freeze-thaw epithelial cell lysates in 96-well polystyrene plates. Levels of residual cellular debris and bacterial viability were further assessed in used contact lens storage cases.

RESULTS

Laser scanning confocal microscopy demonstrated that cotreatment with PMA-stimulated neutrophils increased PA adherence over 24 hours to lens surfaces with a striking alteration of PA architecture. Propidium iodide staining showed that the adherent bacteria consisted of a mixture of viable and nonviable PA; a PMN-associated increase in viable PA was confirmed by CFU (PA:PMN 0.1:1, P = 0.025; PA:PMN 1:1, P = 0.005). Acute epithelial cell debris studies revealed a significant increase in viable PA in 96-well plates in the presence of epithelial freeze-thaw lysates (PA:debris 1:1, P = 0.002; PA:debris 100:1, P = 0.002). Crystal violet staining of used lens storage cases revealed residual cellular debris at all time points, which was independent of microbial contamination; all lens cases used for periods of 9 months or more were uniformly associated with high levels of viable microorganisms.

CONCLUSION

These results demonstrate that prolonged corneal inflammation with the presence of PMNs when confronted with simultaneous PA challenge in extended contact lens wear has the potential to stimulate biofilm formation on silicone hydrogel contact lenses. These findings further suggest that a persistent buildup of extracellular debris in lens storage cases may contribute to the heavy biofilms reported on these surfaces.