Haemophilus influenzae adherent to contact lenses associated with production of acute ocular inflammation

The Ocular Microbiome: Micro-Steps Towards Macro-Shift in Targeted Treatment? A Comprehensive Review

A healthy ocular surface is inhabited by microorganisms that constitute the ocular microbiome. The core of the ocular microbiome is still a subject of debate. Numerous culture-dependent and gene sequencing studies have revealed the composition of the ocular microbiome. There was a confirmed correlation between the ocular microbiome and ocular surface homeostasis as well as between ocular dysbiosis and pathologies such as blepharitis, microbial keratitis, and conjunctivitis. However, the role of the ocular microbiome in the pathogenesis and treatment of ocular surface diseases remains unclear. This article reviews available data on the ocular microbiome and microbiota, their role in maintaining ocular homeostasis, and the impact of dysbiosis on several ophthalmic disorders. Moreover, we aimed to discuss potential treatment targets within the ocular microbiota.

Impact of Exposomes on Ocular Surface Diseases

Ocular surface diseases (OSDs) are significant causes of ocular morbidity, and are often associated with chronic inflammation, redness, irritation, discomfort, and pain. In severe OSDs, loss of vision can result from ocular surface failure, characterised by limbal stem cell deficiencies, corneal vascularisation, corneal opacification, and surface keratinisation. External and internal exposomes are measures of environmental factors that individuals are exposed to, and have been increasingly studied for their impact on ocular surface diseases. External exposomes consist of external environmental factors such as dust, pollution, and stress; internal exposomes consist of the surface microbiome, gut microflora, and oxidative stress. Concerning internal exposomes, alterations in the commensal ocular surface microbiome of patients with OSDs are increasingly reported due to advancements in metagenomics using next-generation sequencing. Changes in the microbiome may be a consequence of the underlying disease processes or may have a role in the pathogenesis of OSDs. Understanding the changes in the ocular surface microbiome and the impact of various other exposomes may also help to establish the causative factors underlying ocular surface inflammation and scarring, the hallmarks of OSDs. This review provides a summary of the current evidence on exposomes in various OSDs.

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.

Comparative Evaluation of Pseudomonas aeruginosa Adhesion to a Poly-(2-Methacryloyloxyethyl Phosphorylcholine)-Modified Silicone Hydrogel Contact Lens

Pseudomonas aeruginosa is the most common causative agent associated with microbial keratitis. During contact lens wear, pathogens may be introduced into the ocular environment, which might cause adverse events. Lehfilcon A is a recently developed contact lens with a water gradient surface composed of polymeric 2-methacryloyloxyethyl phosphorylcholine (MPC). MPC is re-ported to impart anti-biofouling properties onto modified substrates. Therefore, in this in vitro experimental study, we tested the capability of lehfilcon A to resist adhesion by P. aeruginosa. Quantitative bacterial adhesion assays using five strains of P. aeruginosa were conducted to compare the adherence properties of lehfilcon A to five currently marketed silicone hydrogel (SiHy) contact lenses (comfilcon A, fanfilcon A, senofilcon A, senofilcon C, and samfilcon A). Compared to lehfilcon A, we observed 26.7 ± 8.8 times (p = 0.0028) more P. aeruginosa binding to comfilcon A, 30.0 ± 10.8 times (p = 0.0038) more binding to fanfilcon A, 18.2 ± 6.2 times (p = 0.0034) more binding to senofilcon A, 13.6 ± 3.9 times (p = 0.0019) more binding to senofilcon C, and 29.5 ± 11.8 times (p = 0.0057) more binding to samfilcon A. These results demonstrate that, for various strains of P. aeruginosa, lehfilcon A reduces bacterial adhesion compared to other contact lens materials.

Effect of Antimicrobial Contact Lenses on Corneal Infiltrative Events: A Randomized Clinical Trial

Purpose

To determine whether Mel4-coated antimicrobial contact lenses (MACLs) can reduce the incidence of corneal infiltrative events (CIEs) during extended wear.

Methods

A prospective, randomized, double-masked, single-center, contralateral, extended contact lens wear clinical trial was conducted with 176 subjects. Each participant was randomly assigned to wear a MACL in one eye and an uncoated control contact lens in the contralateral eye or an extended-wear biweekly disposable modality for 3 months. The main outcome measures were the incidence of CIEs per 100 eye-months, identification of the microbial types colonizing the contact lenses or eyes at the time of the CIEs, and their susceptibility to Mel4.

Results

Nine participants (5.1%) experienced unilateral CIEs; six participants had contact lens acute red eye, and three participants had infiltrative keratitis. The incidence rate for CIEs (0.4 events per 100 participant months; 1.7%) in the Mel4-coated lenses (test) was 69% less than that of the control lenses (1.3 events per 100 participant months; 3.4%; P = 0.29). All Gram-negative bacteria isolated from lenses and lids of participants with CIEs (Citrobacter diversus, Acinetobacter haemolyticus, and Acinetobacter lwoffii) were susceptible to Mel4 peptide; minimum inhibitory concentrations ranged from 15.6 to 62.5 µg/mL. Reduction of adhesion of these bacteria by Mel4-coated lenses ranged from 2.1 to 2.2 log10 colony-forming units/lens.

Conclusions

MACLs had the capacity to reduce CIEs by at least 50% compared with uncoated control lenses during extended wear over 3 months; however, due to the relatively low rates of CIEs, the reduction was not statistically different compared with control lenses.

Translational Relevance

This study provides evidence that antimicrobial contact lenses have the potential to reduce the incidence of corneal infiltrative events during extended wear.

CLEAR - Evidence-based contact lens practice

Evidence-based contact lens -->practice involves finding, appraising and applying research findings as the basis for patient management decisions. These decisions should be informed by the strength of the research study designs that address the question, as well as by the experience of the practitioner and the preferences and environment of the patient. This reports reviews and summarises the published research evidence that is available to inform soft and rigid contact lens history and symptoms taking, anterior eye health examination (including the optimised use of ophthalmic dyes, grading scales, imaging techniques and lid eversion), considerations for contact lens selection (including the ocular surface measurements required to select the most appropriate lens parameter, lens modality and material selection), evaluation of lens fit, prescribing (teaching self-application and removal, adaptation, care regimen and cleaning instructions, as well as -->minimising risks of lens wear through encouraging compliance) and an aftercare routine.

Current understanding and therapeutic management of contact lens associated sterile corneal infiltrates and microbial keratitis

Contact lenses are widely prescribed in clinical practice with multiple applications and advantages. However, contact lenses can be associated with various complications which range from innocuous to severe. Clinicians thus not only need to possess the ability to prescribe the most appropriate contact lenses for each individual patient but also be able to recognise and manage any associated complications. This review examines the existing literature on the management of corneal infiltrative events associated with soft contact lenses, including microbial keratitis, particularly in the context of practising in Australia. The definitions and diagnosis of corneal infiltrative events, as well as the current understanding of their aetiologies, will be explored. The various aspects of a successful management will be discussed, including the applications of therapeutic agents such as antimicrobial and anti-inflammatory agents, the role of microbiological investigations, and strategies to improve long-term prognosis. The currently available evidence supporting management options will be presented, highlighting the relative abundance of high-level evidence on management protocols, antimicrobial selection and treatment duration for microbial keratitis; and the relative paucity of studies and trials for sterile corneal infiltrative events, despite this condition being much more commonly encountered in clinical practice.

Ocular microbiota and lens contamination following Mel4 peptide-coated antimicrobial contact lens (MACL) extended wear

PURPOSE

The purpose of this study was to investigate the effect of Mel4 antimicrobial peptide-coated contact lenses (MACL) on the microbiota of the conjunctiva and lenses during three months of extended wear.

METHODS

One hundred and seventy-six participants were recruited into a randomised, contralateral, double masked, biweekly extended wear MACL and uncoated control lens trial. At the one month and 3-month visit, the conjunctival microbiota was sampled using sterile cotton swabs and contact lenses were collected aseptically. Standard microbiological procedures were employed for culture of the swabs and contact lenses and identification of the isolated microorganisms.

RESULTS

Gram-positive bacteria (predominantly coagulase-negative staphylococci) were the most frequently isolated microbes from both contact lenses and conjunctiva. There was no difference in the frequency of isolation of most bacteria or fungi from the conjunctival swabs of eyes wearing either MACL or control lenses. The only exception was a higher frequency of eyes harbouring Staphylococcus arlettae when wearing control lenses (5%) versus MACL (<1%) (p = 0.002). There was no significant difference in the frequency of microbes isolated from MACL or control contact lenses. There were also no differences between lens types in the frequency of isolation of >1 microbial type per sampling occasion for either conjunctiva swabs or contact lenses.

CONCLUSION

MACL wear did not change the conjunctival microbiota during extended wear, and the types of microbes isolated from MACL were similar to those isolated from control lenses.

Ocular Surface Microbiome in Health and Disease

The ocular surface is exposed continuously to the environment and, as a consequence, to a variety of different microbes. After the results of the Human Microbiome Project became publicly available, international research groups started to focus interest on exploring the ocular surface microbiome and its physiopathological relationship to the eye. For example, numerous research studies the existence of the ocular surface's bacterial flora, typically gathering cultures from healthy patients and finding few variations in the bacterial species. More recently, culture-independent methods, including 16S ribosomal ribonucleic acid (rRNA) gene sequencing, are being used to define the ocular microbiome. These newer methods suggest that the microbial communities have a greater diversity than previously reported. These communities seem to serve an immune-modulating function and maintain relationships with other microbes and organs, even distant ones. This review summarizes the literature exploring the ocular microbiome, both in health and in different diseases.

Antimicrobial susceptibility of isolated pathogens from patients with contact lens-related bacterial keratitis in Crete, Greece: A ten-year analysis

PURPOSE

To evaluate the bacterial spectrum and antimicrobial susceptibilities of pathogens isolated from contact lens-related bacterial keratitis cases in a large academic Greek hospital.

METHODS

All adult patients with positive corneal scrapings or contact lens culture between 2007 and 2016 at the University Hospital of Heraklion, Greece, were retrospectively identified through a local microbiology database and their medical records were reviewed.

RESULTS

A total of 240 isolates were recovered from 131 patients with culture-proven contact lens-associated bacterial keratitis. The most common microorganism identified was Serratia marcescens (17.1% of total isolates), followed by Pseudomonas aeruginosa, Klebsiella spp. and coagulase-negative staphylococci (CoNS). Rates of aztreonam-resistant P. aeruginosa and erythromycin-resistant CoNS decreased in recent years, while the decrease in oxacillin-resistant CoNS was statistically significant (p=0.009). More than 90% of the isolated organisms (S. marcescens, P. aeruginosa, Klebsiella spp. and CoNS) were susceptible to ciprofloxacin or gentamicin.

CONCLUSION

Gram-negative microorganisms are the most common causative pathogens of contact lens-related keratitis in the region of Crete. Topical antibacterials containing quinolones or gentamicin represent an effective empirical treatment for the majority of the cases. This is quite encouraging, considering that the present study was conducted in a country characterised by high antimicrobial resistance rates. However, culture-driven antimicrobial treatment is mandatory for this sight-threatening infection.

Toll-like receptor gene polymorphisms in patients with keratitis

OBJECTIVE

To investigate differences in SNPs in TLR genes between people who had keratitis and controls in an Indian population.

METHODS

145 cases of keratitis and 189 matched controls were recruited. DNA was extracted from peripheral blood. Single nucleotide polymorphisms (SNP) in TLR2 (n = 6), TLR4 (n = 15), TLR5 (n = 13) and TLR9 (n = 10) were analysed. The risk of developing keratitis was assessed based on allele, genotype and haplotype associations.

RESULTS

For all cases of keratitis, the TLR4 SNP rs4986791 TC genotype frequency was significantly higher in cases (p = 0.006, OR = 1.96, 95 % CI 1.19-3.2). Including cases of only microbial keratitis (MK) revealed that genotypes in TLR2 SNP rs5743706 TA (p = 0.0001; OR = 8.61; 95 % CI 2.59-28.56)), TLR4 SNP s4986791 TC (p = 0.002; OR = 2.65; 95 % CI 1.39-5.07) were significantly more common for MK, whereas the TLR5 SNP rs2241096 A allele (p = 0.00316, OR = 0.42, 95 % CI 0.2-0.9286) and GA genotype (p = 0.016; OR = 0.45; 95 % CI 0.23-0.86) was significantly less common in MK cases. The TLR2 SNP rs5743706 genotype TA was significantly less common in the sterile keratitis (SK) group (p = 0.004, OR = 0.43, 95 %CI 0.24-0.77). Haplotype analysis of MK compared to controls showed that TLR2 AT was more common in controls (p = 0.003); TLR4 ACAC was more common in cases (p = 0.004); TLR5 TGGCA was more common in controls (p = 0.001).

CONCLUSION

The present study revealed multiple associations between variants across TLR genes, which may have implications for understanding the underlying host factors, risk of developing keratitis and molecular pathogenesis in keratitis.

Thirty years of 'quiet eye' with etafilcon A contact lenses

Frequent replacement contact lenses made from the etafilcon A hydrogel lens material were introduced onto the market over 30 years ago, and etafilcon A remains the most widely used hydrogel lens material today. Although the prescribing of silicone hydrogel lenses is increasing, millions of lens wearers globally have been wearing hydrogel lenses for many years and exhibit a physiologically-stable 'quiet eye', with a low profile of adverse events. Hydrogel lenses are demonstrated to maintain a low inflammatory response and infection risk profile during daily wear, which in the case of etafilcon A, may be related to its low modulus, and the naturally-protective, anti-microbial, non-denatured lysozyme absorbed into the lens from the tear fluid. Although improved corneal physiology from decreased hypoxia with silicone hydrogel lenses is well accepted, equivalent levels of corneal oxygenation are maintained during daily wear of low to medium powered hydrogel lenses, which do not impede the daily corneal de-swelling process, and do not induce clinically significant changes in ocular health. Therefore, hydrogel lenses remain an important alternative for daily wear in modern contact lens practice.

Adhesion of Pseudomonas aeruginosa, Achromobacter xylosoxidans, Delftia acidovorans, Stenotrophomonas maltophilia to contact lenses under the influence of an artificial tear solution

Corneal infection is a devastating sight-threatening complication that is associated with contact lens (CL) wear, commonly caused by Pseudomonas aeruginosa. Lately, Achromobacter xylosoxidans, Delftia acidovorans, and Stenotrophomonas maltophilia have been associated with corneal infection. This study investigated the adhesion of these emerging pathogens to CLs, under the influence of an artificial tear solution (ATS) containing a variety of components commonly found in human tears. Two different CL materials, etafilcon A and senofilcon A, either soaked in an ATS or phosphate buffered saline, were exposed to the bacteria. Bacterial adhesion was investigated using a radio-labeling technique (total counts) and plate count method (viable counts). The findings from this study revealed that in addition to P. aeruginosa, among the emerging pathogens evaluated, A. xylosoxidans showed an increased propensity for adherence to both CL materials and S. maltophilia showed lower viability. ATS influenced the viable counts more than the total counts on CLs.

The Development of an Antimicrobial Contact Lens - From the Laboratory to the Clinic

Contact lens wear is generally safe and provides excellent vision. However, contact lens wear is often associated with the risk of developing ocular surface infection and inflammation, and in severe cases, the infection can result in loss of vision. Antimicrobial peptide-coated contact lenses have been made to help reduce the incidence of infection and inflammation. This paper reviews the research progress from conception, through the laboratory and preclinical tests to the latest information on clinical testing of an antimicrobial contact lens. We provide insights into the pathways followed and pitfalls that have been encountered. The journey has not always been linear or smooth, but has resulted in some of the first published clinical testing of antimicrobial peptide-coated contact lenses in humans. We hope this may help lead to the development and commercialisation of antimicrobial contact lenses in the future.

Tear film, contact lenses and tear biomarkers

This article summarises research undertaken since 1993 in the Willcox laboratory at the University of New South Wales, Sydney on the tear film, its interactions with contact lenses, and the use of tears as a source of biomarkers for ocular and non-ocular diseases. The proteome, lipidome and glycome of tears all contribute to important aspects of the tear film, including its structure, its ability to defend the ocular surface against microbes and to help heal ocular surface injuries. The tear film interacts with contact lenses in vivo and interactions between tears and lenses can affect the biocompatibility of lenses, and may be important in mediating discomfort responses during lens wear. Suggestions are made for follow-up research.

Relationship between the microbiome and ocular health

The microbiome is important to the host as a whole, both in maintenance of health and in the pathophysiology of disease. The purpose of this review is to explore the relationship between the gut, ocular microbiome, and ocular disease states. We will also discuss how the microbiome can serve as a potential target for treatment, by methods such as modulation of diet, probiotics and fecal microbiota transplantation. The information discussed in the review has been gathered using literature published from 2004 to November 2018, as indexed in PubMed.

Review of Contact Lens-Related Complications

The purpose of this article is to provide a review of existing literature describing complications with contemporary contact lenses and their management. It is envisioned that this will serve as a useful summary of noninfectious and infectious complications associated with contact lens wear.

A review of cosmetic contact lens infections

This paper provides a comprehensive review of the existing literature surrounding cosmetic contact lens infections. In this paper, lens-related, dispensing-related and patient-related factors are examined in detail.

Comparative Analysis of Adverse Events From a Series of Proof-of-Principle Extended Wear Studies

AIM

A series of proof-of-principle extended wear (EW) contact lens studies were conducted to assess what effect different interventions had on adverse events (AEs). Comparative analysis of AEs across studies was conducted to determine whether some interventions were more effective at reducing inflammatory AEs.

METHOD

Multiple logistic regression analysis of AEs from 30-day EW studies each with a different intervention including (1) nightly replacement (NR) of lenses, (2) morning replacement (MR) of lenses, (3) instillation of prophylactic antibiotic drops (AB) each morning/evening, (4) daily lens cleaning (LC) each morning. All studies conducted at the same site using same lens type (lotrafilcon A) and EW schedule.

RESULTS

Comparison of the different interventions to the individual control groups showed no difference in significant corneal infiltrative event (CIE) or mechanical events. Replacing lenses nightly, during an EW schedule, had the highest incidence of significant CIEs (4.9% [NR] vs. 2.5% [MR] vs. 1.8% [AB] vs. 0% [LC]); however, adjusted logistic regression analysis of the combined control data compared with the individual interventions showed no difference in significant CIEs (P=0.086) or mechanical AEs (P=0.140).

CONCLUSIONS

Replacing lenses each night seemed to be inferior compared with the other interventions of replacing lenses each morning, daily lens cleaning, and daily antibiotic drop instillation during EW. The results of the collective studies and additional analysis suggest that overnight wear of contact lenses seems to create an adverse environment that remains, despite the various interventions intended to improve this adverse environment.

Epidemiology of contact lens-induced infiltrates: an updated review

Corneal infiltrative events (CIEs) are well established as a risk associated with soft contact lens wear. The incidence of symptomatic CIEs during extended soft lens wear ranges from 2.5 to six per cent; when asymptomatic CIEs are included, the incidence can be as high as 20-25 per cent. In daily soft lens wear, the annual incidence of symptomatic CIEs is about three per cent. There are various accepted methods of categorising CIEs, and a scoring system based on clinical signs and symptoms is a good approach to grade severity. Lens-related risk factors include extended wear, silicone hydrogel material, the use of multipurpose solutions, bacterial bioburden and reusable lenses. Recent studies report that daily disposable lenses reduce the risk of CIEs.

Mucin Balls Influence Corneal Infiltrative Events

PURPOSE

To determine whether mucin ball (MB) formation is protective against corneal infiltrative events (CIEs) as previously reported.

METHODS

Two hundred eighty-two eligible participants were enrolled at three sites in the USA. Participants began a 1-month continuous wear run-in period with high modulus lotrafilcon A lenses to assess their ability to form MBs (phase 1). Subsequently, they were stratified by this characteristic and randomized to balafilcon A or comfilcon A lenses for 7-day extended wear and followed for 1 year (phase 2). MB formation in each phase was defined as repeated presence of any MBs on a person level. Multivariable Cox proportional hazards regression was used to model the probability of a CIE as a function of MB formation in each phase and other covariates.

RESULTS

Of the 282 participants who entered phase 1, 218 of them entered the phase 2 randomized trial during which 33 CIEs occurred. Overall, 74%, 61%, and 79% of participants repeatedly produced MBs in lotrafilcon A, balafilcon A, and comfilcon A lenses, respectively. Early repeated MB presence in phase 1 with lotrafilcon A lenses significantly increased the rate of CIEs in phase 2 (12-month follow-up) by 466% (HR 4.66, 95% confidence interval 1.10-19.79, P = .0372). Repeated, longer-term MB presence during wear of balafilcon A or comfilcon A in phase 2 did not significantly reduce the incidence of CIEs; however, it significantly decreased the rate of CIEs by 62% (hazard ratio (HR) 0.380, 95% confidence interval 0.145-0.998, P = .0494).

CONCLUSIONS

The overarching hypothesis that MB formation is protective against CIEs throughout extended wear was not supported. Although a protective effect of longer-term MB presence on rate of CIEs was detected, early-onset MB formation substantially increased the hazard for CIE in subsequent wear with different lens types.

Biocidal efficacy of multipurpose solutions against Gram-negative organisms associated with corneal infiltrative events

Background

Because corneal infiltrative events (CIEs) may result from bacterial components on contact lenses, which can come from contaminated lens cases, we evaluated the biocidal efficacy of five multipurpose solutions against Gram‐negative commonly isolated and CIE‐associated organisms.

Methods

Of the multipurpose solutions tested, one contained polyhexamethylene biguanide (PHMB)/polyquaternium‐1 (PQ‐1; Bausch & Lomb Incorporated: Biotrue), one contained alexidine dihydrochloride (alexidine)/PQ‐1 (AMO: RevitaLens OcuTec) and three contained PQ‐1/myristamidopropyl dimethylamine (MAPD; Alcon: Opti‐Free PureMoist, PQ‐1/MAPD‐1; Opti‐Free RepleniSH, PQ‐1/MAPD‐2; Opti‐Free Express, PQ‐1/MAPD‐3). Challenge organisms were CIE‐associated Achromobacter xylosoxidans, Delftia acidovorans and Stenotrophomonas maltophilia at manufacturer‐recommended durations (stand‐alone), in lens cases without lenses (up to seven days) and in lens cases with etafilcon A lenses (up to 30 days).

Results

In stand‐alone testing against CIE‐associated organisms, PHMB/PQ‐1 and alexidine/PQ‐1 were significantly superior versus MAPD‐based multipurpose solutions against A. xylosoxidans (all p ≤ 0.01), D. acidovorans (all p ≤ 0.001) and S. maltophilia (all p ≤ 0.05). In lens cases, PHMB/PQ‐1 and alexidine/PQ‐1 achieved greater than 3‐log reductions against all challenge organisms at all times evaluated. PQ‐1/MAPD‐1 achieved a greater than 3‐log reduction against D. acidovorans at 24 hours; PQ‐1/MAPD‐1 and PQ‐1/MAPD‐3 achieved greater than 3‐log reductions at seven days against all organisms. In lens cases with lenses, PHMB/PQ‐1 and alexidine/PQ‐1 achieved greater than 3‐log reductions against all organisms at all times. PQ‐1/MAPD‐1 and PQ‐1/MAPD‐3 achieved greater than 3‐log reductions at seven or more days against all organisms. PQ‐1/MAPD‐2 did not achieve a greater than 3‐log reduction at any time; some regrowth was observed.

Conclusions

PHMB‐ and alexidine‐based multipurpose solutions demonstrated significantly greater biocidal activity compared with PQ‐1/MAPD‐based agents against Gram‐negative organisms commonly isolated and CIE‐associated pathogens.

Effect of antibiotic drops on adverse events during extended lens wear

PURPOSE

Overnight lens wear is associated with increased lens contamination and risk of developing a corneal infiltrate or infectious event. Antibacterial lenses have been proposed as a potential strategy for reducing lens contamination. A proof-of-principle study was conducted to investigate what effect control of potential pathogens, through the use of antibiotic eye drops, would have on the incidence of corneal infiltrative events (CIEs) and on the ocular microbiota and lens contamination.

METHODS

This is a prospective, open-label, controlled, parallel-group, 1-month clinical study in which 241 subjects were dispensed with lotrafilcon A silicone hydrogel lenses for 30 days of continuous wear. Subjects were randomized into either test (moxifloxacin 0.5%) or control (rewetting solution) group. One drop was instilled into each eye on waking and before sleeping, while lenses were on-eye. Follow-ups were conducted after one night and 1 month. Lid margin swabs were taken at baseline and at 1 month and worn lenses were aseptically collected at 1 month.

RESULTS

The incidence of CIEs was not significantly different between the test (2.6%) and control (3.9%) groups (p = 0.72). Microorganism levels from the test group swabs were significantly lower than those from the control group (p = 0.001). Gram-positive bacteria were less frequently recovered from lower lid swabs from the test group (39.6% vs. 66.0% [p < 0.001], test vs. control, respectively) or from contact lens samples (1.9% vs. 10.5% [p = 0.015], test vs. control, respectively), but there was no difference in gram-negative bacteria (GNB). Corneal infiltrative events were associated with higher levels of lens contamination (p = 0.014) and contamination of lenses with GNB (CIE: 7.3% vs. 0.6% [p = 0.029], GNB contamination vs. no GNB contamination, respectively).

DISCUSSION

Twice-daily antibiotic instillation during continuous wear of lenses did not significantly influence the rate of inflammatory events. Corneal infiltrative events were associated with higher levels of lens contamination in general and with contamination by GNB specifically.

The effect of daily lens replacement during overnight wear on ocular adverse events

PURPOSE

Compared with daily disposable wear schedule, continuous wear (CW) or extended wear of contact lenses has been associated with an increased risk of developing an ocular infection. Proof-of-principle studies were conducted to investigate the impact of daily replacement of lenses on the rate of contact lens-related ocular adverse events (AEs) during 30-night CW.

METHODS

A total of 215 subjects were dispensed with silicone hydrogel lenses on a 30-night CW schedule but replaced lenses daily either each night before sleeping (n = 178 eyes) or each morning after waking (n = 252 eyes). Scheduled clinic visits were conducted at 1 week and 1 month. Neophytes were required to complete 1 week of daily wear before commencing CW. A historical control (n = 191 eyes) using the same site, subject demographics, and visit schedule but monthly lens replacement was used for AE rates.

RESULTS

Logistic regression analysis showed a significant reduction in mechanical AEs (0.8 vs 5.2%, p = 0.01) and overall AEs (inflammatory and mechanical events) (4.0 vs 8.9%, p = 0.04) when lenses were replaced each morning compared with being replaced monthly. Estimation of handling-related lens contamination of unworn lenses in a subgroup of subjects showed isolation of Staphylococcus aureus from the lenses of 35% of subjects, and 65% of subjects had more than 1000 colony-forming units per lens of gram-positive bacterial contamination.

CONCLUSIONS

Morning lens replacement during CW reduced mechanical and overall ocular AEs. Replacing lenses at night had no beneficial effects perhaps because the benefit of a fresh lens at night might be partially negated by contamination of the contact lens caused by lens handling before overnight eye closure. Contact lens wearers on an extended wear or CW schedule should be advised to minimize lens handling before sleep to reduce the risk of complications.

Microbial adhesion to silicone hydrogel lenses: a review

PURPOSE

Microbial adhesion to contact lenses is believed to be one of the initiating events in the formation of many corneal infiltrative events, including microbial keratitis, that occur during contact lens wear. The advent of silicone hydrogel lenses has not reduced the incidence of these events. This may partly be related to the ability of microbes to adhere to these lenses. The aim of this study was to review the published literature on microbial adhesion to contact lenses, focusing on adhesion to silicone hydrogel lenses.

METHODS

The literature on microbial adhesion to contact lenses was searched, along with associated literature on adverse events that occur during contact lens wear. Particular reference was paid to the years 1995 through 2012 because this encompasses the time when the first clinical trials of silicone hydrogel lenses were reported, and their commercial availability and the publication of epidemiology studies on adverse events were studied.

RESULTS

In vitro studies of bacterial adhesion to unworn silicone hydrogel lens have shown that generally, bacteria adhere to these lenses in greater numbers than to the hydroxyethyl methacrylate-based soft lenses. Lens wear has different effects on microbial adhesion, and this is dependent on the type of lens and microbial species/genera that is studied. Biofilms that can be formed on any lens type tend to protect the bacteria and fungi from the effects on disinfectants. Fungal hyphae can penetrate the surface of most types of lenses. Acanthamoeba adhere in greater numbers to first-generation silicone hydrogel lenses compared with the second-generation or hydroxyethyl methacrylate-based soft lenses.

CONCLUSION

Microbial adhesion to silicone hydrogel lenses occurs and is associated with the production of corneal infiltrative events during lens wear.

Effect of prophylactic antibiotic drops on ocular microbiota and physiology during silicone hydrogel lens wear

PURPOSE

Bacterial contamination of the contact lens surface has been demonstrated to cause corneal infiltrative events. A reduction in the rate of bacterially driven corneal infiltrative events associated with lens wear is one of the major goals of the contact lens industry. There is a concern over the potential of any antimicrobial strategy that there will be unwanted changes to the ocular microbiota or the development of resistance to the antimicrobial. The aim of this study was to investigate the effect of prophylactic topical antibiotic instillation during continuous wear of silicone hydrogel lenses on the normal ocular microbiota, the throat microbiota, and the ocular physiology.

METHODS

Forty-two male subjects were dispensed with lotrafilcon A silicone hydrogel contact lenses for a 3-month, 30 night continuous wear, monthly replacement trial. Subjects were randomized into either tobramycin 0.3% (test) or saline (control) drop group. Two drops were instilled into each eye on waking and before sleep. At monthly visits, lenses were collected aseptically, and ocular and throat swabs were performed, followed by standard microbial recovery and identifications. Any corneal infiltrative event at scheduled or unscheduled visits was recorded.

RESULTS

Numbers of microbes recovered from eye swabs from the tobramycin (test) group were significantly lower than the control (p = 0.01). Gram-positive cocci were recovered less frequently from the test group (p = 0.001). There were no significant differences in the numbers and types of microbes recovered from lens samples, or the contamination rate of the lenses between the two groups. There were no changes in the numbers of fungi or bacteria from throat swabs. There was no evidence of changes to resistance profile of microbes in the throat. More eye swabs from the test group (68.5%) were culture-negative than swabs from control (46.5%; p = 0.002). The test group had less corneal staining superiorly (0.0 ± 0.0 vs. 0.3 ± 0.4; p = 0.025) but increased bulbar redness (2.2 ± 0.5 vs. 1.5 ± 0.4; p < 0.001) at the 3-month visit only, compared with control group.

CONCLUSIONS

Overall, there appeared to be a minimal safety risk with 3-month's prophylactic antibiotic drop use during continuous wear of silicone hydrogel lenses. Clinically, antibiotic drop use induced a mild to moderate increase in bulbar redness by the 3-month time-point. Antibiotic use reduced microbiota on lids but did not affect the microbiota of the throat or change resistance to tobramycin.

External ocular surface and lens microbiota in contact lens wearers with corneal infiltrates during extended wear of hydrogel lenses

OBJECTIVES

To determine whether carriage of microbes on the contact lens or ocular surfaces during extended wear (EW) with soft hydroxyethyl methacrylate (HEMA)-based contact lenses predisposes the wearer to adverse events.

METHODS

Participants (non-contact lens wearers) were enrolled in a clinical study involving wear of HEMA-based hydrogel lenses on a six night EW basis with weekly replacement. Type and number of bacteria colonizing the lower lid margins, upper bulbar conjunctiva, and contact lenses during EW after one night, 1 week, 1 month, and thereafter every 3 months for 3.5 years were determined. The association of bacteria with adverse responses was compared between carriers (defined as having significant microbes cultured from two or more samples with 1 year) and noncarriers, and the strength of the association was estimated using multivariate logistic regression.

RESULTS

Carriers of gram-positive bacteria on lenses (particularly coagulase negative staphylococci or Corynebacterium spp.) were approximately three and eight times more likely to develop contact lens-induced peripheral ulcers (CLPUs) and asymptomatic infiltrates (AIs), respectively. Staphylococcus aureus was most frequently isolated from lenses during CLPU. Carriers of gram-negative bacteria on lenses were five times more likely to develop contact lens-induced acute red eye (CLARE). Haemophilus influenzae was isolated most frequently from lenses during CLARE and AI events.

CONCLUSIONS

Bacterial carriage on contact lenses during EW predisposes the wearer to the development of corneal inflammatory events including CLARE, CLPU, and AI.

Risk factors for corneal inflammatory and mechanical events with extended wear silicone hydrogel contact lenses

PURPOSE

To identify risk factors for contact lens-related corneal inflammatory events and mechanical events in wearers of silicone hydrogel lenses on a 30-night extended wear (EW) schedule in India.

METHODS

An interventional study with 188 subjects wearing silicone hydrogel lenses bilaterally on a 30-night EW schedule. Subjects were dispensed with lenses and reviewed at scheduled visits up to 6 months of EW. Multivariate logistic regression, after adjusting for within subject correlation, was used to develop the statistical model.

RESULTS

Occupations in non-ideal environments were found to predispose a lens wearer to inflammatory events (p = 0.003). Wearers in the non-ideal group, who had varying degrees of exposure to ocular irritants in their work environment had highest incidence of inflammatory events (19.2%). Wearers in a controlled, ideal environment had lowest levels of events (3.3%). Students occupied a position between the two groups (9.3%). Inflammatory rate was higher among wearers with increased microbial contamination of lenses (p = 0.002). Wearers with an inflammatory event had mean colony forming unit of 1.97 log compared with mean colony forming unit of 1.45 log in group with no inflammatory event. Corneal vascularization was associated with the development of inflammatory events (p = 0.001) with 50% of wearers with vascularization experiencing events compared with 7.6% of subjects with no vascularization. Reduced lens movement was associated with inflammatory events with subjects more likely to develop inflammatory events compared with those wearers with optimal lens movement (p = 0.027).

CONCLUSIONS

A multitude of factors, including environmental influences, lens contamination, ocular characteristics, and lens fit, contributes to the development of inflammatory events, information that is of clinical relevance to practitioners worldwide. Occupational environment was also a contributory factor, confirming that a duty of clinicians is to ascertain the nature of the work environment of lens wearers (and potential wearers) and to balance the needs of the wearer with the potential risks.

Identification of unknown ocular pathogens in clinically suspected eye infections using ribosomal RNA gene sequence analysis

DNA sequence-based identification of pathogens from ocular samples of patients with clinically suspected eye infections was accomplished using 16S and internal transcribed spacer (ITS) ribosomal RNA gene sequence analysis. PCR was positive for 24 of 99 samples tested. Both culture and 16S rDNA sequence analysis identified Pseudomonas aeruginosa, streptococci and Enterobacteriaceae. Isolates misidentified as Burkholderia cepacia by biochemical tests were identified as Ralstonia mannitolilytica by 16S rDNA sequence analysis. Sequence analysis identified the following microorganisms from 19 culture-negative samples: Haemophilus influenzae, Sphingomonas sp., Klebsiella pneumoniae, Staphylococcus haemolyticus, Morganella morganii, Mycobacterium sp., Chryseobacterium sp., Pseudomonas saccharophila (Xanthomonas) and the fungus, Phaeoacremonium inflatipes.

Contact lens case contamination during daily wear of silicone hydrogels

PURPOSE

Contamination of contact lens cases has been associated with the production of adverse responses in the eye during contact lens wear. This study aimed to evaluate the contamination rate and types of microbes contaminating cases during use of contact lens disinfecting solutions and silicone hydrogel lenses.

METHODS

Two hundred thirty-two participants were allocated to one or more groups. The participants wore one or more of three silicone hydrogel lenses and used one or more of four contact lens disinfecting solutions. Cases were collected after use for 1 month and sent for routine microbial testing. The rate of contamination of cases and the types of microbes contaminating cases were evaluated.

RESULTS

Between 76 and 92% of all cases were contaminated. Use of different contact lenses did not affect contamination rate or the types of microbes isolated from cases. Use of AQuify (PHMB as disinfectant) was associated with the highest contamination rate (92%; p = 0.015) of cases for any microbe. Level and type of contamination with use of ClearCare (H2O2) was similar to use of PHMB (polyhexamethylene biguanide)- or Polyquat/Aldox-containing solutions. There was no difference in contamination rate of cases by fungi or Gram-positive bacteria, but for Gram-negative bacteria, use of Opti-Free Express (Polyquat and Aldox as disinfectants) resulted in a lower contamination rate (7% vs. 29 to 45%; p < 0.001). The average number of microbes contaminating a case was significantly less for Opti-Free Express (223 +/- 1357 cfu/case) compared with Opti-Free RepleniSH (Polyquat and Aldox as disinfectants; 63,244 +/- 140,630 cfu/case; p < 0.001), driven mostly by differences in numbers of Gram-negative bacteria, particularly contamination by Delftia acidovorans in cases exposed to Opti-Free RepleniSH.

CONCLUSIONS

Different disinfecting solutions used during storage in cases result in different levels of contamination and contamination by different types of microbes. These differences are not simply because of the types of disinfectants used, suggesting that other excipients in, or formulation of, the solution affect contact lens storage case contamination.

Ability of silver-impregnated contact lenses to control microbial growth and colonisation

Purpose

To examine the ability of silver nano-particles to prevent the growth of Pseudomonas aeruginosa and Staphylococcus aureus in solution or when adsorbed into contact lenses. To examine the ability of silver nano-particles to prevent the growth of Acanthamoeba castellanii.

Methods

Etafilcon A lenses were soaked in various concentrations of silver nano-particles. Bacterial cells were then exposed to these lenses, and numbers of viable cells on lens surface or in solution compared to etafilcon A lenses not soaked in silver. Acanthamoeba trophozoites were exposed to silver nano-particles and their ability to form tracks was examined.

Results

Silver nano-particle containing lenses reduced bacterial viability and adhesion. There was a dose-dependent response curve, with 10 ppm or 20 ppm silver showing > 5 log reduction in bacterial viability in solution or on the lens surface. For Acanthamoeba, 20 ppm silver reduced the ability to form tracks by approximately 1 log unit.

Conclusions

Silver nanoparticles are effective antimicrobial agents, and can reduce the ability of viable bacterial cells to colonise contact lenses once incorporated into the lens.