Extended-wear contact lenses, microbial keratitis, and public health

The comparison of antimicrobial effectiveness of contact lens solutions

PURPOSE

The aim of this study was to compare the effects of widely used multipurpose contact lens solutions against Staphylococcus aureus and Pseudomonas aeruginosa, in addition to cystic and trophozoite forms of Acanthamoeba castellanii and A. polyphaga, that cause microbial keratitis.

METHODS

Three multipurpose solutions were tested: SOLO-care, ReNu, and Opti-Free Express. The test solutions were challenged with P. aeruginosa (ATCC 27853) and S. aureus (ATCC 2913) based on the ISO stand-alone and regiment test procedure for disinfecting products, A. polyphaga (ATCC 30871) and A. castellanii (1501/1A) cystic and trophozoite forms. Multipurpose solutions were sampled for surviving microorganisms at manufacturer's minimum recommended disinfection time. The number of viable organisms was determined, and log reductions were calculated.

RESULTS

ReNu and SOLO-care resulted in a reduction greater than the required mean 3.0 logarithmic reduction against S. aureus, and SOLO-care and Opti-Free Express resulted in a reduction more than the required mean 3.0 logarithmic reduction against P. aeruginosa. Against the cystic and trophozoite forms of A. castellanii, the log reduction provided by SOLO-care was 1.01 and 1.31 log, respectively. ReNu provided a 0.83 log reduction of the cystic form and a 1.21 log reduction of the trophozoite form. Using Opti-Free Express, the log reduction for both forms was 1.31. SOLO-care led to a 0.61 log reduction of the cystic form of A. polyphaga and a 1.01 log reduction of the trophozoite form. ReNu provided a 0.41 log reduction of the cystic form and a 4.99 log reduction of the trophozoite form. Opti-free Express resulted in a 0.89 log reduction of the cystic form and a 3.11 log reduction of the trophozoite form.

CONCLUSIONS

Multipurpose contact lens solutions using similar regimens can show different disinfection abilities.

Tear exchange and contact lenses: a review

Tear exchange beneath a contact lens facilitates ongoing fluid replenishment between the ocular surface and the lens. This exchange is considerably lower during the wear of soft lenses compared with rigid lenses. As a result, the accumulation of tear film debris and metabolic by-products between the cornea and a soft contact lens increases, potentially leading to complications. Lens design innovations have been proposed, but no substantial improvement in soft lens tear exchange has been reported. Researchers have determined post-lens tear exchange using several methods, notably fluorophotometry. However, due to technological limitations, little remains known about tear hydrodynamics around the lens and, to-date, true tear exchange with contact lenses has not been shown. Further knowledge regarding tear exchange could be vital in aiding better contact lens design, with the prospect of alleviating certain adverse ocular responses. This article reviews the literature to-date on the significance, implications and measurement of tear exchange with contact lenses.

Contact lens disinfecting solutions antibacterial efficacy: comparison between clinical isolates and the standard ISO ATCC strains of Pseudomonas aeruginosa and Staphylococcus aureus

PURPOSE

To evaluate the disinfectant properties of the three multipurpose contact lens disinfecting solutions available in Iran, against clinical isolates and the standard ISO ATCC strains of Pseudomonas aeruginosa and Staphylococcus aureus, based on the international organization for standardization (ISO) 14729 guidelines.

METHODS

Three multipurpose solutions that were tested were ReNu Multiplus, Solo Care Aqua and All-Clean Soft. The test solutions were challenged with clinical isolates and the standard strains of P. aeruginosa(ATCC 9027) and S. aureus(ATCC 6538), based on the ISO Stand-alone procedure for disinfecting products. Solutions were sampled for surviving microorganisms at manufacturer's minimum recommended disinfection time. The number of viable organisms was determined and log reductions calculated.

RESULTS

All of the three test solutions in this study provided a reduction greater than the required mean 3.0 logarithmic reduction against the recommended standard ATCC strains of P. aeruginosa and S. aureus. Antibacterial effectiveness of Solo Care Aqua and All-Clean Soft against clinical isolates of P. aeruginosa and S. aureus were acceptable based on ISO 14729 Stand-alone test. ReNu MultiPlus showed a minimum acceptable efficacy against the clinical isolate of S. aureus, but did not reduce the clinical isolate by the same amount.

CONCLUSIONS

Although the contact lens disinfecting solutions meet/exceed the ISO 14729 Stand-alone primary acceptance criteria for standard strains of P. aeruginosa and S. aureus, their efficacy may be insufficient against clinical isolates of these organisms.

Microbial keratitis as a foreseeable complication of cosmetic contact lenses: a prospective study

PURPOSE

A recent study shows that the relative risk of contact lenses (CL)-related microbial keratitis (MK) is highly increased with cosmetic contact lenses (CosCL). The aim of our study is to illustrate the implications of the CosCL on the occurence of MK and to describe the subpopulation of CosCL wearers.

METHODS

A prospective multicenter study was conducted in 12 French University Hospitals on all lenses wearers presenting with MK between July 2007 and July 2009, including CosCL wearers. Patients had a complete ophthalmological examination and were interviewed by a 50 items anonymous 'questionnaire' to determine subject demographics and lenses wear history. The CosCL-related MK subpopulation (case) was described and finally compared to (noncosmetic) CL-related MK (control).

RESULTS

Two hundred and fifty-six patients were included for contact lenses-related MK. Thirty-two of them (12.5%) were seen for MK after wearing CosCL. Compared with CL, CosCL wearers are younger (21 versus 27 years of age) and recent wearers (3 versus 9 years). CosCL were rarely dispensed by eye care professionals increasing the risk of MK (OR, 12.3). Education about lens care and handling was deficient for most of CosCL wearers (OR, 26.5). Sixty per cent of CosCL cases versus 13% of CL-related MK had a final visual acuity less than 20/200.

CONCLUSION

Patients who acquire CosCL are less likely to be instructed on appropriate lenses use and basic hygiene rules. Consequently, CosCL wearers are experiencing acute vision-threatening infections.

[Study and prevention of contact lens-related microbial keratitis with a standardized questionnaire]

INTRODUCTION

microbial keratitis is a significant health concern for the one million wearers of contact lenses and their ophthalmologists, with some potentially modifiable risk factors. The number of risk factors for contact lens-related microbial keratitis has been described, but many of them still remain assumed or unknown.

PATIENTS AND METHODS

a multicenter prospective case-control study was conducted in 12 French university hospitals (Besançon, Bordeaux, Dijon, Fort-de-France, Grenoble, Limoges, Lyon, Nancy, Nantes, Paris, Marseille and Strasbourg) beginning in July 2007 on contact lens wearers presenting with microbial keratitis and on healthy contact lens wearers. Patients and healthy wearers were interviewed using a 51-item anonymous standardized questionnaire to determine subject demographics and contact lens wear history.

RESULTS

two hundred and fifty-six patients with microbial keratitis were included. One hundred and thirteen healthy contact lenses wearers were surveyed. Cosmetic contact lens wear highly increased the relative risk (RR) of microbial keratitis (RR, 16.5). Time since the last visit to an ophthalmologist longer than 1 year (RR, 3.4) or prescription by someone other than an ophthalmologist (RR, 7.6) also increased the risk of microbial keratitis. Education on lens care and handling was deficient (hand washing: RR, 2.2; rub and rinse: RR, 2.7).

DISCUSSION

a standardized questionnaire is a powerful tool to determine risk factors for contact lens-related microbial keratitis, but also to analyze individual mistakes in contact lenses use and care.

[Soft-contact-lenses-induced complications]

BACKGROUND/AIM

Soft contact lenses occupy significant place in ophthalmology, both in the correction of refraction anomalies and in the treatment of many eye diseases. The number of patients that wear soft contact lenses for the purpose of correcting ametropia is constantly increasing. Due to the increasing number of wearers, the percentage of complications that can lead to serious eye damage and serious vision loss is also increasing. The aim of this study was to point out the most common complications related to soft contact lens use.

METHODS

In the period from 1995-2004 this prospective study included 510 patients wearing soft contact lenses for correcting ametropia. None of the patients wore contact lenses before and none suffered from any system or local diseases that could affected the development of eventual complications. The study took seven years with the patients who wore conventional lenses and three years with those who wore replacement contact lenses. All the necessary ophthalmologic examinations were done (visual acuity, refractokeratometry, the quantity of tear film, biomicroscopic examination of anterior eye segment). All the complications were filmed by video camera.

RESULTS

Of all the patients, 19 had blepharitis, 73 suffered from "dry eye", 57 had conjunctival hyperemia, 12 had conjunctivitis, 34 had gigantopapillary conjunctivitis (GPC), 93 had punctiform epitheliopathy, 20 had corneal infiltra tion, one patient had keratitis, 91 had corneal vascularisation, and 95 patients had corneal deposits.

CONCLUSION

Both the type and frequency of complications related to soft contact lens use in our group of patients, proved to be significant. Some of this complications (keratitis) can significantly damage vision and lead to loss of vision and sometimes can require operative treatment.

Microbial contamination of contact lenses and lens care accessories of soft contact lens wearers (university students) in Hong Kong

PURPOSE

This study aimed to examine the rates of microbial contamination, and identify contaminants associated with contact lenses and lens care accessories used by a group of young contact lens wearers.

METHODS

Collected contact lenses, lens cases, and lens care solutions were studied by bacterial culture. Contamination rates of these samples were recorded and compared with those reported in previous studies.

RESULTS

Of the samples tested, 9% of lens extracts, 34% of case extracts and 11% of solution samples were contaminated with ocular pathogenic microorganisms. Serratia spp., Staphylococcus aureus and coagulase-negative staphylococci were the most common microorganisms isolated. Lens cases were the most frequently contaminated item. Lens cases also yielded the widest range of bacterial isolates. Contact lenses used by occasional wearers were associated with a higher contamination rate. Using either saline or multipurpose solution to rinse lenses before use appeared to be effective in reducing incidence of contamination.

CONCLUSION

Our findings demonstrate that contact lenses and lens care accessories are not well maintained by contact lens wearers. Regular reviews and reinforcement of lens care procedures for the usage and care of contact lenses and lens care accessories is therefore important and essential.

A fluorometric study of relative ocular lens cytosensitivity to multipurpose contact lens solutions using the resazurin assay method

This study investigated the relative ocular lens cytosensitivity to three multipurpose contact lens solutions using lens culture and resazurin microplate assay method. Comparison in the cell viability levels of the cultured bovine lenses as influenced by 3h experimental exposure to three contact lens multipurpose solutions (OPTI-FREE Express, Alcon; ReNu MultiPlus, Bausch & Lomb; and COMPLETE Comfort Plus, Allergan) was performed. The pre- and post-exposure fluorescence emission levels of the lenses were obtained, and findings were compared to baseline and control measurements. The solutions demonstrated varying levels of sensitivity (P<0.1), exhibiting non-significant to significant reversible disruption of the lenses'cell viability levels as revealed by the fluorescence intensity levels in the following ranked order (COMPLETE< ReNu< OPTI-FREE solutions). The findings show that OPTI-FREE Express and ReNu MultiPlus solutions exhibited more cytosensitive effect compared to COMPLETE Comfort Plus. These results suggest that the resazurin assay together with lens culture would be a reliable system for in vitro investigation of the effect of contact lens solutions and other ophthalmic formulations on ocular tissues.

Efficacy of multipurpose solutions for rigid gas permeable lenses

The use of multipurpose solutions for cleaning and disinfecting rigid gas permeable lenses has replaced single purpose solutions, but there are no reports of the efficacy of these multipurpose solutions, or of the effects of storage conditions on their disinfecting capacities. This study investigated activity against four bacterial and two fungal species, and the effects of storage in a refrigerator, at room temperature, at elevated temperature in both dry and humid conditions and with exposure to sunlight. The disinfecting solutions were challenged with the micro-organisms initially upon opening and then at 2-weekly intervals up to 12 weeks after being stored under the different conditions. Solutions were opened daily to simulate use. One solution failed to meet Food and Drug Administration (FDA) criteria to reduce numbers of bacteria by three log dilutions and of fungi by one log dilution. Storage reduced activity of all solutions over the 12-week period, but not below the requirements of the FDA. Storage in the refrigerator tended to reduce disinfecting capacity more quickly. Multipurpose solutions for rigid gas permeable (RGP) lenses lose activity over the 3 months recommended time of use but remain satisfactory for use over this time in the conditions tested. Practitioners need to remind patients to replace their solutions regularly and should advise against storage in the refrigerator. Multipurpose solutions for RGP lenses have simplified cleaning and disinfecting processes and the current formulations have improved disinfecting capacity compared to former disinfecting solutions, which is particularly important for wearers of orthokeratology lenses.

Mikrobielle Keratitis

PURPOSE

To determine the risk factors and the influence of complementary/alternative medicines (CAM) for infectious keratitis in a monsoon-free region of the Sultanate of Oman.

STUDY DESIGN

Retrospective single center cohort study.

OUTCOME MEASURES

Demographic data, risk factors, and pathogens.

METHODS

Patients with purulent stromal keratitis admitted from 2001-2004 were evaluated for clinical and microbiological data, CAM use, duration of hospitalization, and outcome of treatment.

STATISTICS

chi(2)-test, Z-test.

RESULTS

A total of 320 patients (326 eyes) out of 7,524 admissions had severe infectious stromal keratitis requiring inpatient treatment. The average age was 35.1+/-2.5 years (range 1.5-63 years), the male:female ratio was 2:3 in the age group >or=13 years and 2:1 in the age group <or=12 years. Unsuccessful treatment by traditional healers prior to presentation was recorded for 203 patients (62.3%). Ocular risk factors included severe trachomatous dry eye conditions, meibomianitis and soft contact lens overwear. Systemic compromising risk factors were diabetes mellitus and medical immunosuppression. A total of 215 patient eyes (66%) had delayed or no healing (therapy drop-outs), and hospitalization (45 days) was significantly prolonged compared to the 111 antibiotic responders (26 days) (p<0.001). All eyes of patients with prior CAM had worse vision at admission and after therapy (p<0.001), and 97 eyes of patients with uncontrolled diabetes (p<0.001) and 68 eyes of patients with immunosuppression (p<0.001) had a poor visual outcome (vision <0.1). Thirteen eyes perforated. A negative microbiological result correlated with worse final vision (p<0.05). All 13 perforated eyes had received prior CAM (p<0.001).

CONCLUSIONS

Trachoma, trauma and contact lens overwear are significant risk factors for infectious keratitis in Oman and correlate with specific age groups. Delay in treatment due to the first-line utilization of CAM showed a significant adverse impact on outcome.

Influence of Day and Night Wear on Surface Properties of Silicone Hydrogel Contact Lenses and Bacterial Adhesion

PURPOSE

The aim of this study was to determine the effect of continuous wear on physicochemical surface properties of silicone hydrogel (S-H) lenses and their susceptibility to bacterial adhesion.

METHODS

In this study, volunteers wore 2 pairs of either "lotrafilcon A" or "balafilcon A" S-H contact lenses. The first pair was worn continuously for a week and the second pair for 4 weeks. One lens of each pair was used for surface characterization and the other one for bacterial adhesion experiments. Lens surfaces were characterized by examination of their wettability, roughness, elemental composition, and proteins attached to their surfaces. Adhesion of Staphylococcus aureus 835 and Pseudomonas aeruginosa #3 to a lens was studied using a parallel plate flow chamber.

RESULTS

Before use, the lotrafilcon A lens was rougher than the balafilcon A lens and had a lower water contact angle and a higher affinity for S. aureus 835. After wear, both lens types had similar water contact angles, whereas the differences in elemental surface composition decreased as well. S. aureus 835 adhered in higher numbers to worn balafilcon A lenses, whereas the opposite was seen for P. aeruginosa #3. The initial deposition rates of both bacterial strains to lotrafilcon A lenses decreased by wearing and were found to correlate significant (P < 0.001) with the surface roughness of worn lenses.

CONCLUSIONS

In this study, the differences in surface properties between 2 types of S-H lenses were found to change after 1 week of continuous wear. Generally, bacteria adhered in lower numbers and less tenaciously to worn lenses, except S. aureus 835, adhering in higher numbers to worn balafilcon A lenses.

Microbial keratitis in ITU staff: an occupational hazard?

Microbial keratitis is a potentially blinding corneal infection; the infection may progress rapidly if untreated and result in corneal perforation. The breakdown of the innate ocular defences is known to predispose to corneal infection. We present three cases of microbial keratitis in intensive therapy unit (ITU) staff each of whom had compromised corneal immunity. Anaesthetists and nurses regularly perform high-risk procedures, such as tracheal suctioning, which have been known to cause ocular infections by aerosol inoculation. We suggest that although the absolute risk of infection is low, susceptible individuals may be at increased risk of corneal infection from exposure to potentially pathogenic organisms in such environments. We stress the need for ITU staff, particularly those who wear contact lenses, to wear eye protection when performing procedures likely to cause infected aerosols.

Physicochemical factors influencing bacterial transfer from contact lenses to surfaces with different roughness and wettability

The aim of this study was to determine the transfer of Pseudomonas aeruginosa No. 3 and Staphylococcus aureus 835 from contact lenses to surfaces with different hydrophobicity and roughness. Bacteria were allowed to adhere to contact lenses (Surevue, PureVision, or Focus Night & Day) by incubating the lenses in a bacterial suspension for 30 min. The contaminated lenses were put on a glass, poly(methylmethacrylate), or silicone rubber substratum, shaped to mimic the eye. After 2 and 16 h, lenses were separated from the substrata and bacteria were swabbed off from the respective surfaces and resuspended in saline. Appropriate serial dilutions of these suspensions were made, from which aliquots were plated on agar for enumeration. Bacterial transfer varied between 4 and 60%, depending on the combination of strain, contact time, contact lens, and substratum surface. For P. aeruginosa No. 3, transfer was significantly higher after 16 h than after 2 h, whereas less increase with time was seen for S. aureus 835. Bacterial transfer from all tested contact lenses was least to silicone rubber, the most hydrophobic and roughest substratum surface included.

Effect of storage temperatures and time on the efficacy of multipurpose solutions for contact lenses

PURPOSE

To determine the effect of storage time and temperature on the efficacy of four multipurpose solutions for soft contact lenses.

METHOD

Aliquots of multipurpose solutions (OPTI-FREE Express, ReNu MultiPlus, COMPLETE and SOLO-care) stored at different temperatures over a 3-month period, were challenged with contact lens-related ocular pathogens, Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans.

RESULTS

The results showed that OPTI-FREE Express had the best activity against Ps. aeruginosa at all temperatures; ReNu MultiPlus performed well at 25 degrees C; COMPLETE barely achieved activity requirements at all temperatures, and lost efficacy after 2 months. SOLO-care maintained its activity best against Ps. aeruginosa at 30 degrees C. Storage at fridge temperature reduced activity of all solutions. Regardless of storage temperature, activities of all solutions against S. aureus markedly decreased by 2 months. Only OPTI-FREE Express met FDA requirements against C. albicans.

CONCLUSION

Performance of multipurpose solutions is affected by time and temperature of storage. Contact lens users should be aware that the efficacy of opened solutions may not be sustained for as long as 3 months. Manufacturers should reconsider their recommendations to further safeguard the ocular health of contact lens wearers.

Continuous wear silicone hydrogel contact lenses and microbial keratitis

Like other lens types, the new generation of silicone hydrogel contact lenses can be associated with a spectrum of ocular complications. Most tend to be very minor, but serious and sight-threatening complications can occur. We present four such cases with microbial keratitis following extended wear of these lenses. Cultures were positive for Pseudomonas aeruginosa in three cases and all three of these suffered lasting visual impairment. We describe our findings and discuss possible risk factors.

Effects of daily and overnight wear of a novel hyper oxygen-transmissible soft contact lens on bacterial binding and corneal epithelium: a 13-month clinical trial

OBJECTIVE

To test prospectively a new biologic rationale for an advanced hyper oxygen-transmissible lens (HOTL) providing prospects for safer daily (DW) or extended (EW) contact lens wear.

DESIGN

Prospective, randomized, double-masked, single-center, 13-month clinical trial.

PARTICIPANTS

One hundred sixty-eight patients completed the DW study (1 month): control lens (n = 70); HOTL (n = 98). One hundred thirty-six patients finished 1 year of EW: controls (n = 56), HOTL (n = 25, 6 nights; n = 55, 30 nights).

TESTING

Irrigation chamber to collect corneal surface cells, confocal microscopy, tear collection at baseline, 2, and 4, weeks of DW, and 24 hours, 1, 3, 6, 9, and 12 months of EW.

MAIN OUTCOME MEASURES

(1) Pseudomonas aeruginosa (PA) binding to exfoliated corneal surface cells; (2) central epithelial thickness (CET); (3) superficial cell area (SCA); (4) epithelial surface cell exfoliation (DESQ); and (5) tear lactate dehydrogenase (LDH).

RESULTS

Daily wear with control lens increased PA binding from 5.90 +/- 2.60 to 7.81 +/- 3.04 bacteria per cell (P < 0.01); HOTL wear increased PA binding significantly less (5.31 +/- 1.87-5.98 +/- 2.26; P < 0.01). Daily wear produced no significant changes in CET or SCA. Significant decreases in DESQ were seen with both lenses with no significant intergroup differences. Tear LDH increased significantly in DW with HOTL wear versus control (P = 0.0017), but not after 1 month of subsequent EW (P = 0.533). One to 3 months of EW with control lens showed significantly higher PA binding than HOTL wear (P < 0.01); binding adaptively decreased thereafter, returning to baseline at 9 to 12 months. Lens EW produced significantly enlarged SCA, thinning of CET (except 6-night HOTL wear), and decreased DESQ (P < 0.01). Some adaptive recovery was seen with CET and DESQ, but not SCA; importantly, the data indicated no significant difference between 6- or 30-night EW for all outcomes.

CONCLUSIONS

Hyper oxygen-transmissible lens wear (DW or EW) produced significantly decreased PA binding compared with control lens wear, with no significant difference in wearing schedule (6 nights vs. 30 nights); additionally, there was a remarkable and unexpected adaptive recovery in the first 6 months of all soft lens wear, with a return to baseline PA binding levels and partial recovery for the other outcomes except SCA at 1 year. These results suggest that HOTL use should result in a decrease in the incidence of and risk(s) for lens-related microbial keratitis and that further epidemiologic studies should consider time in adapted EW in future risk and incidence analyses.

Is there a question of safety with continuous wear?

The availability of silicone-containing hydrogel contact lenses (SCHCLs) has refocused attention on the risks associated with continuous wear (CW). The major barrier to optometrists prescribing CW in Western societies is a perceived danger of microbial keratitis (MK). This perception has been shaped largely by educators who have developed their opinions from case reports in the ophthalmic literature, sensationalist lay press reports and later epidemiological studies and from prominent physicians in tertiary referral centres, following an increased incidence of MK with extended wear (EW) of traditional hydrogel materials. The basis for the perceived lack of safety is the higher risk of MK with EW compared to daily wear and incidence figures that suggest an unacceptable level of MK in a population at risk, albeit a small risk on an individual basis. In this paper, I re-evaluate the validity of the previous data and challenge the conclusions regarding the nature of the risk with traditional hydrogel lens materials. Areas under scrutiny include diagnostic criteria, morbidity caused by different micro-organisms, potential bias in studies and reports, analysis of visual outcomes and cost to the community, and improvements over time in the understanding and handling of contact lens-related complications. Significant loss of vision with EW appears to be less frequent than is the common perception. When the risks are placed in the perspective of other data such as that for refractive surgery, the arguments against EW do not seem so compelling. The high oxygen transmissibility of SCHCLs may enable safe CW but a large-scale epidemiological study is needed to allay remaining doubts. Any such future studies should note the points outlined in this document.

A novel phosphorylcholine-coated contact lens for extended wear use

The preparation and characterisation of a new phosphorylcholine (PC)-coated silicone hydrogel contact lens for use in extended wear is described. The Michael-type addition of amines to acrylates forms the basis of the synthesis of a novel silicone-based macromer with hydrophilic functionality. It is demonstrated that this macromer can be combined with other silicone-based monomers, hydrophilic monomers and crosslinker to produce a contact lenses formulation. Examples of lenses with water contents of 33% and 46% are illustrated and their properties compared to other commercially available lenses. Materials with comparatively low modulus (<0.3 MPa) and adequate tear strength (>2-4MPa) with excellent elongation to break (>200%) can be obtained using this technology. In addition to the mechanical aspects. both the oxygen and solute permeabilities of the material can be controlled by the hydrophilic: hydrophobic monomer balance in the formulation. to obtain materials with attributes suitable for extended wear use. The PC coating is achieved by means of an in-mould coating (IMC) technique that produces a uniform and stable surface as determined by staining and XPS. The coating imparts both improved lens wettability (advancing contact angle of approximately 50 with virtually no hysteresis) and lower protein adsorption relative to the uncoated lens.