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

Use, Misuse, and Complications of Contact Lens Among the General Population of the Kingdom of Saudi Arabia

PURPOSE

This study aims to assess contact lens usage patterns, complications, knowledge levels, and the impact of psychological factors on misuse among the Saudi population.

METHODS

In this study, we distributed our questionnaire through multiple social media platforms among patients who are using cosmetic or medical contact lenses regardless of the purpose of wearing them. A total of 1,708 contact lens users participated.

RESULTS

Most participants were female (86.4%) and aged 21-40 years (65.7%). The purpose for usage was cosmetic (36.1%) or medical (28.7%), with some using them for both purposes (35.1%). Complications have been faced, with 26.3% experiencing issues due to lens usage, 56.8% facing visual problems, and 45.8% sometimes feeling discomfort with contact lens usage. Allergic reactions were reported by 35.2%. Higher knowledge levels were associated with participants aged 21-40 years (p = 0.009), irregular ophthalmologist visits (p = 0.032), and cosmetic use (p = 0.027). Better practice patterns were observed among urban residents (p = 0.049), higher-income earners (p = 0.002), cosmetic users (p < 0.001), and those with fewer complications (p < 0.001). Psychological factors significantly influenced misuse, with 15.4% of participants indicating its impact. Notably, a subset of these participants (16.2%) perceived prolonged wear of contact lenses as a manifestation of personal insecurity.

CONCLUSIONS

Several sociodemographic factors, including place of residence, income, and difficulty, influence the use of contact lenses. It is also necessary to consider psychological issues such as low self-esteem and social acceptance while encouraging the safe use of contact lenses.

Comfort After Refitting Symptomatic Habitual Reusable Toric Lens Wearers with a New Daily Disposable Contact Lens for Astigmatism

Purpose

To subjectively evaluate comfort with a daily disposable (delefilcon A for astigmatism) contact lens compared to other common weekly/monthly soft toric contact lenses in symptomatic wearers.

Methods

This open-label, single arm study enrolled current reusable soft toric lens wearers with minimum score of 12 on the contact lens dry eye (CLDEQ-8) questionnaire. Subjects were also administered the CLDEQ-8 after 1 replacement schedule of their optimized habitual toric lenses (2 to 4 weeks), and after 2 weeks of wear with delefilcon A toric daily disposable lenses (Dailies Total1 for Astigmatism; Alcon Vision LLC, Fort Worth, Texas).

Results

A total of 85 subjects completed the study. Mean total CLDEQ-8 score was 16.8 ± 8.1 for subjects refit with their optimized habitual toric lenses and 12.4 ± 7.5 for subjects refit with delefilcon A toric lenses, a difference of 4.3 ± 10.4 (p < 0.001). With delefilcon A toric lenses, 78.9% of subjects reported little to no intensity of eye discomfort, compared to 51.7% for the habitual toric lenses (p = 0.005). In addition, 77.7% of subjects reported little to no intensity of dryness for delefilcon A toric lenses, compared to 50.6% for the habitual toric lenses (p = 0.001).

Conclusion

The subjective comfort in symptomatic habitual reusable toric contact lens wearers was improved by refitting with delefilcon A toric lenses.

TFOS Lifestyle: Impact of contact lenses on the ocular surface

Several lifestyle choices made by contact lens wearers can have adverse consequences on ocular health. These include being non-adherent to contact lens care, sleeping in lenses, ill-advised purchasing options, not seeing an eyecare professional for regular aftercare visits, wearing lenses when feeling unwell, wearing lenses too soon after various forms of ophthalmic surgery, and wearing lenses when engaged in risky behaviors (e.g., when using tobacco, alcohol or recreational drugs). Those with a pre-existing compromised ocular surface may find that contact lens wear exacerbates ocular disease morbidity. Conversely, contact lenses may have various therapeutic benefits. The coronavirus disease-2019 (COVID-19) pandemic impinged upon the lifestyle of contact lens wearers, introducing challenges such as mask-associated dry eye, contact lens discomfort with increased use of digital devices, inadvertent exposure to hand sanitizers, and reduced use of lenses. Wearing contact lenses in challenging environments, such as in the presence of dust and noxious chemicals, or where there is the possibility of ocular trauma (e.g., sport or working with tools) can be problematic, although in some instances lenses can be protective. Contact lenses can be worn for sport, theatre, at high altitude, driving at night, in the military and in space, and special considerations are required when prescribing in such situations to ensure successful outcomes. A systematic review and meta-analysis, incorporated within the review, identified that the influence of lifestyle factors on soft contact lens dropout remains poorly understood, and is an area in need of further research. Overall, this report investigated lifestyle-related choices made by clinicians and contact lens wearers and discovered that when appropriate lifestyle choices are made, contact lens wear can enhance the quality of life of wearers.

Addressing common myths and misconceptions in soft contact lens practice

Advances in contact lens technology over the past 50 years since the commercialisation of the first soft lenses in 1971 have been incredible, with significant changes in contact lens materials, frequency of replacement, care systems and lens designs occurring. However, despite the widespread availability of contact lenses, penetration rates for those who need vision correction remain in the low single digits and many practitioners seem to hold on to concepts around the potential value of contact lenses that appear based in the dim and distant past and are certainly no longer valid today. This review addresses 10 common 'myths and misconceptions' around soft contact lenses using an evidence-based approach that can hopefully dispel some of these incorrect assumptions.

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.

Regular soft contact lens wearers' comprehension of graphical symbols labelled on multipurpose solutions

CLINICAL RELEVANCE

Symbols are commonly used to represent information of health care products included multipurpose solutions (MPSs) for contact lens (CL) care.

BACKGROUND

Little knowledge is available about recognition and comprehension by regular soft CL wearers of commonly used symbols in the instructions of CL MPSs marketed worldwide.

METHODS

CL wearers from the UK and Spain were invited to answer an anonymous on-line questionnaire (distributed though Facebook and Twitter) concerning the recognition and comprehension of seven common symbols (ISO 15223:2017 and EN 980:2008) included in MPS package instructions.

RESULTS

Answers of one hundred-ten soft CL wearers who use MPS (27 in the UK and 83 in Spain) were analysed showing low recognition and comprehension of the surveyed symbols even in wearers with > 5 years of CL wear (71.8%). The CE marked was the most recognised (96% in the UK and 88% in Spain, P = 0.29) and understood (78% in the UK and 85% in Spain, P = 0.25) symbol, but other important symbols, such as 'Caution' and 'Do not reuse', were under recognised (22% in the UK and 19% in Spain, P = 0.78 and 11% in the UK and 6% in Spain, P = 0.40 respectively) and understood (close to 30% in both countries P > 0.15). Participants with > 5 years of experience, showed slightly higher comprehension (P < 0.05) in some symbols ('Sterilised'; 'Do not reuse'; 'Use by date' and 'CE marked').

CONCLUSION

These results suggest an insufficient comprehension of seven common symbols included in MPS instructions among regular CL wearers in the UK and Spain without high impact of CL wear experience. Improving the education and symbol comprehension of regular CL wearers could help to get better patients' behaviour and safe use of MPS in soft CLs care.

Contact Lens Use Patterns, Behavior and Knowledge Among University Students in Thailand

Purpose

Little is known about contact lens (CL) use in young generation. This study aimed to investigate the patterns, behavior and knowledge of CL wear and care in Thai university students.

Methods

A cross-sectional study using online questionnaires was conducted during July 2019 to February 2020 in two Rajabhat universities, Bangkok, Thailand. Participant characteristics, CL information, knowledge and behaviors were collected. Factors associated with poor behaviors and CL-related corneal ulcers were analyzed using logistic regression.

Results

Of 493 students participating in the survey, 336 students (66.78%) were current CL users and completed the questionnaires. Mean age was 19.2 ± 1.4 years with female predominance (80.36%). All students wore soft CL with a major replacement schedule of monthly disposable (90.18%). Good CL wear and care behaviors were found in 190 students (56.55%). The most common poor CL behavior and poor CL knowledge were CL overuse (44.64%) and sleeping with lenses (31.85%), respectively. There were no correlations between behaviors and knowledge (r = 0.03). Purchasing lens from internet, wearing experience over one year, and long wear duration (> 12 hours) were significantly associated with poor CL behavior. Male gender and swimming with lens were significantly associated with history of corneal ulcers.

Conclusion

The study pointed out a low compliance of CL wear and care in Thai university students. Good CL practices, awareness of CL-related complications and purchasing place should be carefully informed and regularly stressed to minimize preventable visual damage in young population.

Microbiological Evaluation of Opened Saline Bottles for Scleral Lens Use and Hygiene Habits of Scleral Lens Patients

SIGNIFICANCE

Scleral lenses have become a widely used treatment option for patients with irregular corneas and ocular surface disease. Successful wear entails use of a nonpreserved saline solution to fill the lens before application on the eye.

PURPOSE

The purposes of this study were to evaluate solution from opened bottles of multidose preservative-free saline for microbiological growth and to better understand study participant hygiene habits while handling these bottles for scleral lens wear.

METHODS

Eligible study participants in this single-center prospective study were patients who routinely used multidose preservative-free saline solution for scleral lens rinsing and filling. Study participants completed a 12-question survey regarding their scleral lens hygiene habits and donated their opened multidose preservative-free saline bottle (PuriLens Plus; The Lifestyle Company, Inc., Freehold, NJ), which was processed for bacterial and fungal cultures.

RESULTS

Thirty-five participants (19 males, 16 females) with ages ranging from 6 to 81 years (mean, 47.9 years) were included. Indications for scleral lens wear included those with irregular corneas and ocular surface disease. The overall rate of microbial contamination among saline samples was 62.9% (n = 22). Twenty-one different microorganisms were identified. The survey responses did not differ significantly (P > .05) for any of the questions with regard to likelihood of positive culture. There were no significant age or sex differences between participants with positive or negative culture results. No significant differences were found between isolation of specific microorganisms and any of the survey responses.

CONCLUSIONS

This study suggests that off-label multidose preservative-free saline commonly used to rinse and fill scleral lenses before application on the eye may become contaminated with microorganisms once the bottle has been opened. Eye care practitioners and scleral lens patients should be aware of these potential contaminations and prioritize lens, hand, and environmental hygiene to minimize the risk of ocular complications.

Interactions between contact lenses and lens care solutions: Influence in optical properties

PURPOSE

Investigate changes in optical properties of contact lenses materials (transmittance and reflectance) and lens care solutions (absorption and fluorescence) resulting from its interaction.

METHODS

From an experimental study, triplicate measurements of transmittance and reflectance of five contact lenses (Senofilcon A, Lotrafilcon B, Balafilcon A, Comfilcon A, and Omafilcon A), as well as UV-vis absorption and fluorescence of four lens care solutions (LCS) (ReNu MultiPlus, Biotrue, OPTI-FREE PureMoist, and AOSept Plus), were evaluated before and after 8 h, one day and one week in storage. The outcomes were provided by Shimadzu UV3101-PC UV-vis-NIR spectrophotometer equipped with an integrating sphere, between 200-700 nm, and SPEX-Fluorolog 2 FL3-22 spectrofluorometer.

RESULTS

All variables exhibited statistically significant differences over time. Comfilcon A showed the lowest ultraviolet radiation (UVR) A & B attenuation. Balafilcon A and Lotrafilcon B displayed a slight suppression of UVR. Senofilcon A was effective in UVR protection and showed less effect on the fluorescence of lens care solutions. Overall, the reflectance decreased after storage (p < 0.05). AOSept Plus absorbance and fluorescence demonstrated lower interactions than multipurpose solutions (MPS), and Lotrafilcon B induced more remarkable changes in optical properties of LCS than the other materials.

CONCLUSION

The findings suggest that optical variables of lens care solutions and contact lenses changed mutually after storage, probably associated with biochemical and biophysical interactions between components and the release of some polymer compounds. These findings can provide additional information about the interaction of CL materials and LCS in clinical behavior.

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.

Safety and Efficacy of Scleral Lenses for Keratoconus

SIGNIFICANCE

This study affirms the long-term safety and efficacy of scleral contact lens use in patients with keratoconus.

PURPOSE

This study aimed to evaluate the safety and efficacy of contemporary scleral contact lenses in the visual rehabilitation of the keratoconic population.

METHODS

A retrospective study of keratoconic subjects examined between 2013 and 2018 was conducted. Subjects were included regardless of age, sex, pre-existing morbidity, or scleral lens design. Only eyes fit successfully with scleral contact lenses for ≥1 year were included. Exclusion criteria were prior corneal surgery, dystrophy, degeneration, and trauma.

RESULTS

A total of 157 eyes of 86 subjects met the study criteria. The mean Keratoconus Severity Score at initial fitting was 3.6 ± 1.0. Lenses were gas-permeable and nonfenestrated, with a mean overall diameter of 15.8 ± 0.6 mm and 70.1% toric scleral periphery. Physiological adverse events occurred in 9.6% of eyes, including microbial keratitis (0.6%), phlyctenulosis (0.6%), corneal abrasion (1.3%), contact lens–induced acute red eye (1.3%), corneal infiltrative events (1.3%), pingueculitis (1.3%), and hydrops (3.2%). Lens-related adverse events were documented in 55.4% of eyes. Adverse events related to surface issues included poor wetting in 1.9%, handling in 3.8%, reservoir fogging in 7.0%, lens intolerance in 7.6%, deposit in 8.9%, and broken lenses in 26.1% of eyes. The most common management strategies involved refits (54.0% of interventions), patient reeducation (29.5%), medical treatment (5.5%), surgical referral (6.8%), adjustment to wear time (2.5%), surface treatment (1.2%), and lens replacement (0.6%). Best-corrected distance logMAR visual acuity improved significantly from a mean of 0.50 in spectacles to a mean of 0.08 in scleral lenses (P < .0001). During the study period, 14.6% of eyes lost best-corrected scleral lens visual acuity, all from keratoconus progression.

CONCLUSIONS

Consistent with other groups, our study demonstrates excellent safety and efficacy of scleral contact lenses in subjects with keratoconus.

Risk Factors for Acanthamoeba Keratitis-A Multistate Case-Control Study, 2008-2011

OBJECTIVE

To identify modifiable risk factors contributing to Acanthamoeba keratitis (AK) infection.

METHODS

A case-control investigation was conducted. Case patients were soft contact lens wearers with laboratory-confirmed AK. Control were soft contact lens wearers ≥12 years of age, with no history of AK. Case patients were recruited from 14 ophthalmology referral centers and a clinical laboratory. Control were matched on state of residence and type of primary eye care provider (ophthalmologist or optometrist). Participants were interviewed using a standardized questionnaire. Univariable and multivariable conditional logistic regression analyses were conducted. Matched odds ratios (mORs) were calculated.

RESULTS

Participants included 88 case patients and 151 matched control. Case patients were more likely to be aged <25 years (unadjusted mOR 2.7, 95% confidence interval 1.3-5.5) or aged >53 years (mOR 2.5, 1.1-5.7), and more likely to be men (mOR 2.6, 1.4-4.8). Unadjusted analyses identified multiple risk factors: rinsing (mOR 6.3, 1.3-29.9) and storing lenses in tap water (mOR 3.9, 1.2-12.3), topping off solution in the lens case (mOR 4.0, 2.0-8.0), having worn lenses ≤5 years (mOR 2.4, 1.3-4.4), rinsing the case with tap water before storing lenses (mOR 2.1, 1.1-4.1), and using hydrogen peroxide (mOR 3.6, 1.1-11.7) versus multipurpose solution. Significant risk factors in multivariable modeling included age >53 years, male sex, topping off, and using saline solution.

CONCLUSIONS

Numerous modifiable risk factors for AK were identified, mostly involving hygiene practices. To reduce the risk of AK, lens wearers should observe recommended lens care practices.

Physico-chemistry of bacterial transmission versus adhesion

Bacterial adhesion is a main problem in many biomedical, domestic, natural and industrial environments and forms the onset of the formation of a biofilm, in which adhering bacteria grow into a multi-layered film while embedding themselves in a matrix of extracellular polymeric substances. It is usually assumed that bacterial adhesion occurs from air or by convective-diffusion from a liquid suspension, but often bacteria adhere by transmission from a bacterially contaminated donor to a receiver surface. Therewith bacterial transmission is mechanistically different from adhesion, as it involves bacterial detachment from a donor surface followed by adhesion to a receiver one. Transmission is further complicated when the donor surface is not covered with a single layer of adhering bacteria but with a multi-layered biofilm, in which case bacteria can be transmitted either by interfacial failure at the biofilm-donor surface or through cohesive failure in the biofilm. Transmission through cohesive failure in a biofilm is more common than interfacial failure. The aim of this review is to oppose surface thermodynamics and adhesion force analyses, as can both be applied towards bacterial adhesion, with their appropriate extensions towards transmission. Opposition of surface thermodynamics and adhesion force analyses, will allow to distinguish between transmission of bacteria from a donor covered with a (sub)monolayer of adhering bacteria or a multi-layered biofilm. Contact angle measurements required for surface thermodynamic analyses of transmission are of an entirely different nature than analyses of adhesion forces, usually measured through atomic force microscopy. Nevertheless, transmission probabilities based on Weibull analyses of adhesion forces between bacteria and donor and receiver surfaces, correspond with the surface thermodynamic preferences of bacteria for either the donor or receiver surface. Surfaces with low adhesion forces such as polymer-brush coated or nanostructured surfaces are thus preferable for use as non-adhesive receiver surfaces, but at the same time should be avoided for use as a donor surface. Since bacterial transmission occurs under a contact pressure between two surfaces, followed by their separation under tensile or shear pressure and ultimately detachment, this will affect biofilm structure. During the compression phase of transmission, biofilms are compacted into a more dense film. After transmission, and depending on the ability of the bacterial strain involved to produce extracellular polymeric substances, biofilm left-behind on a donor or transmitted to a receiver surface will relax to its original, pre-transmission structure owing to the viscoelasticity of the extracellular polymeric substances matrix, when present. Apart from mechanistic differences between bacterial adhesion and transmission, the low numbers of bacteria generally transmitted require careful selection of suitably sensitive enumeration methods, for which culturing and optical coherence tomography are suggested. Opposing adhesion and transmission as done in this review, not only yields a better understanding of bacterial transmission, but may stimulate researchers to more carefully consider whether an adhesion or transmission model is most appropriate in the specific area of application aimed for, rather than routinely relying on adhesion models.

Antimicrobial Efficacy of Contact Lens Care Solutions Against Neutrophil-Enhanced Bacterial Biofilms

Purpose

Neutrophil-derived extracellular debris has been shown to accelerate bacterial biofilm formation on hydrogel and silicone hydrogel contact lens surfaces compared to lenses inoculated with bacteria alone. The purpose of this study was to evaluate the disinfection efficacy of four standard commercial contact lens cleaning regimens against neutrophil-enhanced bacterial biofilms formed on silicone hydrogel contact lenses.

Methods

Four reference strains were used: Pseudomonas aeruginosa,Serratia marcescens,Stenotrophomonas maltophilia, and Staphylococcus aureus. Human neutrophils were isolated from peripheral blood by venipuncture. Unworn Lotrafilcon B lenses were incubated overnight in each respective strain with stimulated neutrophils. Contact lenses were then cleaned using one of four contact lens care solutions according to manufacturer instructions. Bacterial viability was assessed by colony counts and confocal microscopy. Volume of residual debris on lens surfaces after cleaning was quantified using IMARIS software.

Results

All four solutions tested showed effective antimicrobial activity against each bacterial strain; however, substantial amounts of nonviable bacteria and cellular debris remained on the lens surface despite concomitant digital cleaning.

Conclusions

Necrotic cellular debris that accumulates under the posterior lens surface during wear of an inoculated contact lens is not fully removed during routine cleaning and disinfection.

Translational Relevance

The accumulation of residual cellular debris on the contact lens surface may contribute to new colonization of the lens and represents a significant risk factor for a contact lens–related adverse event. Additional studies are needed to correlate these findings with risk for corneal infiltrative and/or infectious events in a standard animal model.

Marine Sponge-Derived Streptomyces sp. SBT343 Extract Inhibits Staphylococcal Biofilm Formation

Staphylococcus epidermidis and Staphylococcus aureus are opportunistic pathogens that cause nosocomial and chronic biofilm-associated infections. Indwelling medical devices and contact lenses are ideal ecological niches for formation of staphylococcal biofilms. Bacteria within biofilms are known to display reduced susceptibilities to antimicrobials and are protected from the host immune system. High rates of acquired antibiotic resistances in staphylococci and other biofilm-forming bacteria further hamper treatment options and highlight the need for new anti-biofilm strategies. Here, we aimed to evaluate the potential of marine sponge-derived actinomycetes in inhibiting biofilm formation of several strains of S. epidermidis, S. aureus, and Pseudomonas aeruginosa. Results from in vitro biofilm-formation assays, as well as scanning electron and confocal microscopy, revealed that an organic extract derived from the marine sponge-associated bacterium Streptomyces sp. SBT343 significantly inhibited staphylococcal biofilm formation on polystyrene, glass and contact lens surfaces, without affecting bacterial growth. The extract also displayed similar antagonistic effects towards the biofilm formation of other S. epidermidis and S. aureus strains tested but had no inhibitory effects towards Pseudomonas biofilms. Interestingly the extract, at lower effective concentrations, did not exhibit cytotoxic effects on mouse fibroblast, macrophage and human corneal epithelial cell lines. Chemical analysis by High Resolution Fourier Transform Mass Spectrometry (HRMS) of the Streptomyces sp. SBT343 extract proportion revealed its chemical richness and complexity. Preliminary physico-chemical characterization of the extract highlighted the heat-stable and non-proteinaceous nature of the active component(s). The combined data suggest that the Streptomyces sp. SBT343 extract selectively inhibits staphylococcal biofilm formation without interfering with bacterial cell viability. Due to absence of cell toxicity, the extract might represent a good starting material to develop a future remedy to block staphylococcal biofilm formation on contact lenses and thereby to prevent intractable contact lens-mediated ocular infections.

Risk Factors for Contact Lens-Related Microbial Keratitis: A Case-Control Multicenter Study

PURPOSE

The most feared complication of contact lens (CL) wear is microbial keratitis (MK), even though its incidence remains low. This study aimed to identify the risk factors of CL-related MK in a large, prospective, multicenter case-control study.

METHODS

A multicenter case-control study was designed. The CL-related MK subpopulation (Case) was compared with healthy CL wearers (Control) using a 52-item anonymous questionnaire designed to determine subject demographics and lens wear history. Univariate and multivariate logistic regression analyses were performed to compare both groups.

RESULTS

The study enrolled 499 cases and 508 controls. The risk factors associated with the greatest increased odds of CL-related MK were as follows: using disinfecting solution more than 3 months (odds ratio [OR]=1.94), cosmetic CL wear and use of multipurpose disinfection solution (1.37 each), overnight wear, and soft lens use (OR=1.24 each). The protective factors associated with the greatest reduction in OR were fitting by an ophthalmologist (OR=0.73) and hyperopia versus myopia (OR=0.75).

CONCLUSIONS

The infectious determinants were linked to the type of lenses, hygiene routine, CL handling, disinfecting solution, and storage case. This study aimed to highlight the increasingly CL-related MK, which likely occurs because of lack of patient information regarding basic rules of hygiene and CL care and handling.

Effect of the osmolarity change in multipurpose solutions induced by an improper contact lens case cleaning procedure

PURPOSE

To determine whether variations in multipurpose disinfecting solution (MPDS) storage osmolarity from inappropriate contact lens (CL) case cleaning affect ocular surface integrity and wearer comfort.

METHODS

There were twenty contact lens cases (study CLCs) in the study group. Ten were filled with ReNu Multiplus(®) and 10 with SoloCare Aqua™ (MPDS-1 and -2, respectively) and kept closed for 8h; the cases were then emptied and kept open for air-drying for 16h. This procedure was carried out every day for two months. Storage solution osmolarity was measured on days 0, 15, 30, 45 and 60. Ten subjects were then fitted with both month-old lenses stored in the study CLCs and with new lenses stored in new cases with fresh solution for 24h (control CLCs). Symptoms, tear osmolarity and percentage of subjects whose conjunctival hyperaemia and ocular surface staining scores changed were determined after 1h of wear.

RESULTS

Study CLC osmolarity increased in both solutions after two months (p<0.05). For MPDS-1 there were differences in stinging between study CLCs and control CLCs after 10min of CL wear (p=0.04), and in comfort after 10 (p=0.035) and 60min wear (p=0.042). Significant (p<0.05) differences between study CLC and control CLC groups were also found for MPDS-2 in limbal hyperaemia (study: 50% change; control: 0% change) and bulbar and corneal staining (study: 80% change; control: 20% change).

CONCLUSION

The stored-MPDS osmolarity increase caused by air-drying the CLCs could affect the ocular surface. This increase might reduce lens wear comfort.

"Chemical nose" for the visual identification of emerging ocular pathogens using gold nanostars

Ocular pathogens can cause serious damages in the eye leading to severe vision loss and even blindness if left untreated. Identification of pathogens is crucial for administering the appropriate antibiotics in order to gain effective control over ocular infection. Herein, we report a gold nanostar based "chemical nose" for visually identifying ocular pathogens. Using a spectrophotometer and nanostars of different sizes and degrees of branching, we show that the "chemical nose" is capable of identifying the following clinically relevant ocular pathogens with an accuracy of 99%: S. aureus, A. xylosoxidans, D. acidovorans and S. maltophilia. The differential colorimetric response is due to electrostatic aggregation of cationic gold nanostars around bacteria without the use of biomolecule ligands such as aptamers or antibodies. Transmission electron microscopy confirms that the number of gold nanostars aggregated around each bacterium correlates closely with the colorimetric response. Thus, gold nanostars serve as a promising platform for rapid visual identification of ocular pathogens with application in point-of-care diagnostics.

Identification of coagulase-negative staphylococci in daily disposable contact lens wearers

This study aimed to identify and quantify the number of contaminating organisms on daily disposable (DD) soft contact lenses, which may be responsible for mild cases of keratitis that occur with this lens wear modality. Ten participants wore DD lenses, and 10 participants wore planned replacement (PR) lenses. Lenses were collected aseptically and analysed for microbial contamination. Colony-forming units (CFU) were recorded, and representative colonies were used for identification using the API identification system. The DD lenses evaluated in this study were contaminated with coagulase-negative staphylococcus (CNS), ranging from 1 to 653 CFU. PR lenses showed more diversity in the types of contaminating micro-organisms and consisted of CNS, Gram-negative bacteria (Pseudomonas), a yeast (Candida) and a mould (Aspergillus), ranging from 1 to 230 CFU. CNS was the only type of micro-organism found on DD contact lenses and therefore may be the cause of any form of keratitis observed in DD lens wearers.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first study to determine the frequency and identify the contaminating organisms found on daily disposable (DD) soft contact lenses. The contaminating organisms identified on DD contact lenses were solely coagulase-negative staphylococcus (CNS), suggesting that CNS may be the causative organism associated with infectious keratitis that occurs with DD contact lens wear.

The use of daily disposable lenses in problematic reusable contact lens wearers

PURPOSE

Replacing soft contact lenses (CLs) on a daily basis brings a number of advantages, most notably, reduced exposure to deposits, disinfectants, allergens, and other contaminants. This retrospective study estimated the prevalence of problems in current wearers of reusable soft CLs and tested the effect of refitting "problem" patients with daily disposable (DD) hydrogel lenses.

METHODS

Prevalence was estimated from 398 current reusable CL wearers for: frequent/constant discomfort or dryness, ≥2 h of uncomfortable wear, ≥grade 2 conjunctival hyperaemia (0-4), or ≥grade 3 corneal staining (0-15). In the second part of the study, 217 reusable CL wearers classified as problem patients were randomly refitted with DD lenses manufactured from one of two materials: etafilcon A (n=96) or nelfilcon A (n=121) and reassessed 1 week later.

RESULTS

Thirty-nine percent (154/398) had some qualifying criterion: reduced comfortable wearing time (CWT), 20%; dryness, 20%; irritation, 5%; corneal staining, 8%; and hyperaemia, 7%. After refitting with DDs, the prevalence of reduced CWT was decreased from 65% to 51% (P=0.0039), dryness from 60% to 41% (P < 0.0001) and corneal staining from 28% to 21% (P=0.04). There was no significant change in the prevalence of irritation, or hyperaemia. Some differences were noted between the two lens materials.

CONCLUSIONS

A high proportion of reusable soft lens wearers encounter clinically relevant signs or symptoms with their current CLs. This study provides evidence that refitting with DD lenses is a useful strategy for alleviating some of the common problems of CL wear.

Bacterial cell surface deformation under external loading

Viscoelastic deformation of the contact volume between adhering bacteria and substratum surfaces plays a role in their adhesion and detachment. Currently, there are no deformation models that account for the heterogeneous structure and composition of bacteria, consisting of a relatively soft outer layer and a more rigid, hard core enveloped by a cross-linked peptidoglycan layer. The aim of this paper is to present a new, simple model to derive the reduced Young’s modulus of the contact volume between adhering bacteria and substratum surfaces based on the relationship between deformation and applied external loading force, measured using atomic force microscopy. The model assumes that contact is established through a cylinder with constant volume and does not require assumptions on the properties and dimensions of the contact cylinder. The reduced Young’s moduli obtained (8 to 47 kPa) and dimensions of the contact cylinders could be interpreted on the basis of the cell surface features and cell wall characteristics, i.e., surfaces that are more rigid (because of either less fibrillation, less extracellular polymeric substance production, or a higher degree of cross-linking of the peptidoglycan layer) had shorter contact cylinders and higher reduced Young’s moduli. Application of an existing Hertz model to our experimental data yielded reduced Young’s moduli that were up to 100 times higher for all strains investigated, likely because the Hertz model pertains to a major extent to the more rigid peptidoglycan layer and not only to the soft outer bacterial cell surface, involved in the bond between a bacterium and a substratum surface.

The viscoelastic properties of the bond between an adhering bacterium and a substratum surface play a role in determining bacterial detachment. For instance, removal of an oral biofilm proceeds according to a viscoelastic failure model, and biofilm left behind after toothbrushing has been found to possess expanded bond lengths between adhering bacteria due to viscoelastic deformation. Current elastic deformation models are unable to distinguish between the soft outer bacterial cell surface and the hard core of a bacterium, enveloped by a peptidoglycan layer. Therefore, here we present a simple model to calculate the Young’s modulus and deformation of the contact volume between an adhering bacterium and a substratum surface that accounts for the heterogeneous structure of a bacterium.

Effects of VIP on corneal reconstitution and homeostasis following Pseudomonas aeruginosa induced keratitis

PURPOSE

Studies from our laboratory have demonstrated that vasoactive intestinal peptide (VIP) directly converts the normally susceptible C57BL/6J (B6) mouse to resistant after ocular infection through modulation of the inflammatory response. This study examines mechanisms by which VIP influences the healing phase following infection--specifically reconstitution of the extracellular matrix (ECM).

METHODS

B6 mice received daily intraperitoneal (IP) injections of VIP, while control mice were similarly injected with sterile phosphate buffered saline (PBS). Real-time RT-PCR, ELISA, and immunofluorescent staining were used to assess the effects of VIP treatment on ECM molecule expression after Pseudomonas aeruginosa-induced keratitis. We also compared the effect of VIP treatment on lipopolysaccharide (LPS)-stimulated B6- and BALB/c-derived fibroblasts.

RESULTS

In vivo analyses revealed that VIP treatment of P. aeruginosa-infected B6 corneas led to a significant increase in ECM molecules associated with healing/homeostasis, while those associated with ECM degradation were significantly down-regulated when compared to wild-type (WT) controls. In vitro studies revealed that VIP treatment of lipopolysaccharide-stimulated fibroblasts derived from susceptible B6 and resistant BALB/c mice expressed distinct differences in ECM molecule expression, whereby the latter expressed higher levels of ECM molecules aimed at reconstitution. Furthermore, differential expression of VIP receptor-1/VIP receptor-2 (VIPR1/VIPR2) was observed between B6 and BALB/c after VIP treatment of LPS-stimulated fibroblasts.

CONCLUSIONS

VIP treatment functions to enhance ECM reconstitution, which appears to be carried out in large part by fibroblasts via VIPR2. Overall, the data from this study suggest that VIP not only regulates disease pathogenesis, but also functions to restore integrity of the corneal stroma.

New strategy for rapid diagnosis and characterization of fungal infections: the example of corneal scrapings

Purpose

The prognosis of people infected with Fungi especially immunocompromised depends on rapid and accurate diagnosis to capitalize on time administration of specific treatments. However, cultures produce false negative results and nucleic-acid amplification techniques require complex post-amplification procedures to differentiate relevant fungal types. The objective of this work was to develop a new diagnostic strategy based on real-time polymerase-chain reaction high-resolution melting analysis (PCR-HRM) that a) detects yeasts and filamentous Fungi, b) differentiates yeasts from filamentous Fungi, and c) discriminates among relevant species of yeasts.

Methods

PCR-HRM detection limits and specificity were assessed with a) isolated strains; b) human blood samples experimentally infected with Fungi; c) blood experimentally infected with other infectious agents; d) corneal scrapings from patients with suspected fungal keratitis (culture positive and negative) and e) scrapings from patients with suspected bacterial, viral or Acanthamoeba infections. The DNAs were extracted and mixed with primers diluted in the MeltDoctor® HRM Master Mix in 2 tubes, the first for yeasts, containing the forward primer CandUn (5'CATGCCTGTTTGAGCGTC) and the reverse primer FungUn (5'TCCTCCGCTT ATTGATATGCT) and the second for filamentous Fungi, containing the forward primer FilamUn (5'TGCCTGTCCGAGCGTCAT) and FungUn. Molecular probes were not necessary. The yields of DNA extraction and the PCR inhibitors were systematically monitored.

Results

PCR-HRM detected 0.1 Colony Forming Units (CFU)/µl of yeasts and filamentous Fungi, differentiated filamentous Fungi from yeasts and discriminated among relevant species of yeasts. PCR-HRM performances were higher than haemoculture and sensitivity and specificity was 100% for culture positive samples, detecting and characterizing Fungi in 7 out 10 culture negative suspected fungal keratitis.

Conclusions

PCR-HRM appears as a new, sensitive, specific and inexpensive test that detects Fungi and differentiates filamentous Fungi from yeasts. It allows direct fungal detection from clinical samples and experimentally infected blood in less than 2.30 h after DNA extraction.

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.

New strategy for rapid diagnosis and characterization of keratomycosis

PURPOSE

The first-line therapy for patients with keratitis is different for bacteria, filamentous fungi, and yeasts. The timely onset of treatments depends on rapid and accurate diagnosis. However, fungal cultures produce high rates of false-negative results. Nucleic acid amplification techniques (polymerase chain reaction [PCR]) improve fungal diagnosis performance, but they require complex postamplification procedures to differentiate filamentous fungi from yeasts or to identify the agent. The objective of this work was to develop a new diagnostic strategy based on real-time PCR high-resolution melting (HRM) analysis that in 1 run (a) detects and semiquantifies yeasts and filamentous fungi, (b) differentiates yeasts from filamentous fungi, and (c) discriminates among relevant species of yeasts.

DESIGN

Experimental study to compare HRM diagnosis performances with microscopic examination of corneal scrapings and fungal culture.

PARTICIPANTS AND CONTROLS

High-resolution melting detection limits and specificity were assessed with (a) isolated strains; (b) agents (other than fungi) producing keratitis; (c) corneal scrapings from fungal keratitis (culture positive and negative); and (d) corneal scrapings from bacterial, viral, or Acanthamoeba keratitis.

METHODS

The DNA extracted from cornea specimens was mixed with primers diluted in the MeltDoctor HRM Master Mix (Applied Biosystems, Paris, France) in 2 tubes, the first for yeasts, containing the forward primer CandUn (5'CATGCCTGTTTGAGCGTC) and the reverse primer FungUn2 (5'TCCTCCGCTTATTGATATGCT), and the second for filamentous fungi, containing the forward primer FilamUn1 (5'TGCCTGTCCGAGCGTCAT) and FungUn2. Molecular probes were not necessary. The yields of DNA extraction and the PCR inhibitors were monitored by adding internal controls to each sample.

MAIN OUTCOME MEASURES

Detection of fungi in corneal samples by HRM.

RESULTS

High-resolution melting consistently detects the equivalent of 0.1 colony-forming units /ml of yeasts and filamentous fungi, differentiates filamentous fungi from yeasts, and discriminates among relevant species of yeasts. High-resolution melting sensitivity and specificity were 100% for culture-positive samples, detecting and characterizing fungi in 7 of 10 culture-negative suspected fungal keratitis.

CONCLUSIONS

High-resolution melting is a new, sensitive, specific, and inexpensive test that detects fungi and differentiates filamentous fungi from yeasts directly from clinical specimens in less than 2.30 hours after DNA extraction.

Patient compliance during contact lens wear: perceptions, awareness, and behavior

OBJECTIVES

Patient noncompliance with recommended hygienic practices in contact lens wear is often considered a significant risk factor for microbial keratitis and adverse contact lens-related events. Despite advancements in lens materials and care solutions, noncompliant behavior continues to hinder efforts to maximize contact lens safety. The objective of this pilot study was to assess the relationship between perceived and actual compliance with awareness of risk and behavior.

METHODS

One hundred sixty-two established contact lens wearers were sequentially evaluated after their routine contact lens examination at the Optometry Clinic at the University of Texas Southwestern Medical Center at Dallas, TX. Each patient was questioned by a single trained interviewer regarding his or her lens care practices and knowledge of risk factors associated with lens wear.

RESULTS

Eighty-six percent of patients believed they were compliant with lens wear and care practices; 14% identified themselves as noncompliant. Using a scoring model, 32% demonstrated good compliance, 44% exhibited average compliance, and 24% were noncompliant; age was a significant factor (P = 0.020). Only 34% of patients who perceived themselves as compliant exhibited a good level of compliance (P<0.001). Eighty percent of patients reported an awareness of risk factors, but awareness did not influence negative behavior. Replacing the lens case was the only behavior associated with a positive history for having experienced a prior contact lens-related complication (P = 0.002).

CONCLUSIONS

Perceived compliance is not an indicator for appropriate patient behavior. A large proportion of patients remain noncompliant despite awareness of risk. Education alone is not a sufficient strategy to improve behavior; newer approaches aimed at improving compliance with lens care practices are urgently needed.