Pseudomonas Keratitis Associated With Continuous Wear Silicone-Hydrogel Soft Contact Lens

Biomimetic Functional Surfaces towards Bactericidal Soft Contact Lenses

The surface with high-aspect-ratio nanostructure is observed to possess the bactericidal properties, where the physical interaction between high-aspect-ratio nanostructure could exert sufficient pressure on the cell membrane eventually lead to cell lysis. Recent studies in the interaction mechanism and reverse engineering have transferred the bactericidal capability to artificial surface, but the biomimetic surfaces mimicking the topographical patterns on natural resources possess different geometrical parameters and surface properties. The review attempts to highlight the recent progress in bactericidal nanostructured surfaces to analyze the prominent influence factors and cell rupture mechanism. A holistic approach was utilized, integrating interaction mechanisms, material characterization, and fabrication techniques to establish inclusive insights into the topographical effect and mechano-bactericidal applications. The experimental work presented in the hydrogel material field provides support for the feasibility of potentially broadening applications in soft contact lenses.

Polymicrobial Infection of the Cornea Due to Contact Lens Wear

A 38-year-old male presented with pain and redness in his left eye. He had a history of wearing contact lenses. His ophthalmic examination revealed a large corneal ulcer with surrounding infiltrate. Cultures were isolated from the contact lenses, lens solutions, storage cases, and conjunctivae of both eyes and also corneal scrapings of the left eye. Fortified vancomycin and amikacin drops were started hourly. Culture results of conjunctivae of each eye and left cornea were positive for Pseudomonas aeruginosa; cultures from the contact lenses, lens solution and storage case of both eyes revealed Pseudomonas aeruginosa and Alcaligenes xylosoxidans. Polymerase chain reaction of the corneal scraping was positive for Acanthameoba. The topical antibiotics were changed with ones that both bacteria were sensitive to and anti-amoebic therapy was added. The patient had two recurrences following initial presentation despite intensive therapy. Keratitis occurred due to multiple pathogens; the relapsing course despite adequate therapy is potentially associated with this polymicrobial etiology.

Microbial contamination of contact lenses after scaling and root planing using ultrasonic scalers with and without protective eyewear: A clinical and microbiological study

Background:

Ultrasonic scaler is a preferential treatment modality among the clinicians. However, the aerosol/splatter generated is a concern for patients and practitioners. Therefore, the purpose of this study was to evaluate contamination of contact lenses of the dentist after scaling and root planing using ultrasonic scalers with and without protective eyewear.

Materials and Methods:

Thirty patients were randomly selected for scaling and root planing and divided into 2 groups of 15 each. Group A – dentist wearing contact lenses and protective eyewear. Group B - dentist wearing only contact lenses. After scaling and root planing using ultrasonic scalers, the lenses were subjected to culture and 16S rRNA (16S ribosomal RNA) gene sequencing.

Results:

In Group A – 15 out of thirty samples were contaminated, in Group B – all the thirty samples were contaminated. Most of the samples showed Gram-positive bacteria and 5 samples were contaminated with fungi. 16S rRNA gene sequencing of forty contaminated samples showed that 31 were contaminated with Streptococcus mutans and 9 with Staphylococcus aureus.

Conclusion:

Keeping in mind the limitation of the study for the absence of negative control, we would like to conclude that dental practitioners should better avoid contact lenses in a dental setup because of the risk of contamination of the contact lenses from the various dental procedures which can produce aerosol/splatter and if worn, it is recommended to wear protective eyewear.

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.

Diabetes and contact lens wear

The literature suggests that diabetic patients may have altered tear chemistry and tear secretion as well as structural and functional changes to the corneal epithelium, endothelium and nerves. These factors, together with a reported increased incidence of corneal infection, suggest that diabetic patients may be particularly susceptible to developing ocular complications during contact lens wear. Reports of contact lens-induced complications in diabetic patients do exist, although a number of these reports concern patients with advanced diabetic eye disease using lenses on an extended wear basis. Over the past decade or so, there have been published studies documenting the response of the diabetic eye to more modern contact lens modalities. The results of these studies suggest that contact lenses can be a viable mode of refractive correction for diabetic patients. Furthermore, new research suggests that the measurement of tear glucose concentration could, in future, be used to monitor metabolic control non-invasively in diabetic patients. This could be carried out using contact lenses manufactured from hydrogel polymers embedded with glucose-sensing agents or nanoscale digital electronic technology. The purpose of this paper is to review the literature on the anterior ocular manifestations of diabetes, particularly that pertaining to contact lens wear.

Microbiologic study of soft contact lenses after laser subepithelial keratectomy for myopia

PURPOSE

To evaluate the extent and agents of bacterial contamination of bandage disposable soft contact lenses after laser subepithelial keratectomy (LASEK) and to correlate the findings with clinical data.

METHODS

Disposable soft contact lenses were collected from 52 eyes of 26 consecutive patients treated with LASEK for myopia. The patients were treated with a fixed combination of tobramycin and diclofenac until epithelial closure. The lenses were removed on the fourth or fifth postoperative day with sterile forceps and immediately placed in sterile tubes containing culture media brain-heart infusion broth. The lenses were evaluated for microbial colonization.

RESULTS

Of the 52 contact lenses analyzed, six (11.5%) had positive cultures. However, no clinical finding of infection was noted. Isolated microorganisms were coagulase-negative staphylococci (two lenses), Stenotrophomonas maltophilia (two lenses), Acinetobacter species (one lens), and Aeromonas hydrophila (one lens). Except for one case, the microorganisms were sensitive to the administered antibiotic.

CONCLUSIONS

The risk of infectious keratitis after LASEK seems to be low. Except for staphylococci, the isolated microorganisms have not been previously reported to colonize the ocular surface or cause keratitis after refractive surgery. These findings may suggest a changing trend of potentially infectious agents after surface ablation.

Chronic morbidity of corneal infiltrative events associated with contact lens wear

PURPOSE

To determine the chronic morbidity of corneal infiltrative events (CIEs) associated with contact lens wear.

METHODS

The central corneas of both eyes of 13 subjects who had suffered a CIE 27 +/- 4 months previously were examined by using slit-lamp biomicroscopy, confocal microscopy, and ultrasound pachometry. Snellen visual acuity was recorded in both eyes. A questionnaire was administered to ascertain the type and extent of changes in contact lens wear and care since suffering from the CIE.

RESULTS

Slit-lamp biomicroscopy revealed the presence of a circular scar, approximately 1.5 mm in diameter, in the central cornea of the right eye of the patient who had suffered the most clinically severe CIE; no residual scar, or any other abnormality, was detected in any of the other 12 patients. No significant difference between the 2 eyes was found with respect to basal epithelial cell density; anterior or posterior keratocyte density; endothelial cell density, polymegethism, or pleomorphism; corneal thickness; or visual acuity. Anecdotally, however, markedly reduced pan-corneal cell counts, increased endothelial polymegethism, and reduced corneal thickness were observed in the affected eye of the patient who had suffered the most clinically severe CIE. After having suffered from a CIE, many patients changed lens type or brand, ceased to routinely sleep in lenses, or wore lenses less often.

CONCLUSIONS

In general, contact lens-associated CIEs do not compromise the long-term integrity of the cornea. Changes in lens-related behaviors of patients who have suffered from a CIE seem to be aimed at reducing the risk of a further occurrence. Anecdotally, more severe CIEs may be associated with chronic tissue morbidity.

The immunomodulatory Pseudomonas aeruginosa signalling molecule N ‐(3‐oxododecanoyl)‐ l ‐homoserine lactone enters mammalian cells in an unregulated fashion

The Pseudomonas aeruginosa quorum-sensing signal molecule N-3-oxododecanoyl)-L-homoserine lactone (OdDHL) has been reported to affect the function of a wide range of mammalian cell types, including cells of the immune system. In T cells, it has been reported to inhibit the production of most cytokines, and it has been reported to inhibit the function of antigen-presenting cells. The intracellular target of OdDHL in these cells remains to be identified, although the lipophilic nature of the molecule suggested that the target could be membrane associated. We explored the association of radiolabelled OdDHL with the membrane and cytoplasm of Jurkat T-cell lines and of primary murine T cells and dendritic cells. We found that not only did 3H-OdDHL enter the cytoplasm of Jurkat cells without disproportionate association with the cell membrane, it also reached maximum levels in the cytoplasm very quickly, and that the intracellular concentration was proportional to the extracellular concentration. Similar results were obtained when 3H-OdDHL was incubated with primary murine T cells or cultured dendritic cells. In addition, we show that the cellular distribution of OdDHL does not significantly alter after stimulation of Jurkat cells or primary murine CD4 T cells with immobilized anti-CD3, with little activity being associated with nuclear fractions. Together, these data strongly suggest that OdDHL enters mammalian cells by passive mechanisms, and that it does not preferentially associate with the membrane or nucleus upon T-cell receptor ligation.

Use of silicone hydrogel material for daily wear

Silicone hydrogel contact lenses were initially developed to optimise oxygen transmissibility for extended wear use. The concerns with such contact lenses have been their higher elastomeric and hydrophobic characteristics associated with the incorporation of silicone type monomers. The use of silicone hydrogel has most recently been suggested for daily wear to eliminate all hypoxic related problems. The primary aim of the investigation was to test in vivo wetting performance and subjective acceptance of the first silicone hydrogel contact lens developed for daily wear, ACUVUE ADVANCE with HYDRACLEAR (galyfilcon A), compared to a conventional hydrogel contact lens for the same application SofLens 66 (alphafilcon A). The investigation was a randomised, subject masked bilateral cross over investigation testing of the two contact lens materials over their approved replacement periods (galyfilcon A 2 weeks and alphafilcon A 2 weeks (USA) and 4 weeks (Europe)). In all cases ReNu Multiplus lens care system was used. The investigation carried out on 24 contact lens wearers showed that: (i) in vivo wettability was superior for galyfilcon A which had a thicker lipid layer (thin layer incidence: galyfilcon A 54%; alphafilcon A 70-86%, p<0.05), a thicker aqueous layer (thick layer incidence: galyfilcon A 88%; alphafilcon A 35-64%, p<0.05) and a more stable tear film (galyfilcon A 7.8s; alphafilcon A 2 weeks 5.6s, p=0.022; 4 weeks 7.4s, p=0.276); (ii) for the intended replacement period, comfort was better with galyfilcon A (2 weeks) compared to alphafilcon A (4 weeks) at insertion (p=0.001) and, throughout the day (daytime and evening p=0.008). Contact lenses made from galyfilcon A and replaced two weekly achieved better in vivo wettability than contact lenses made from alphafilcon A and replaced either two and four weekly; the better wettability was associated with an overall better comfort for galyfilcon A.

Scalloped Channels Enhance Tear Mixing Under Hydrogel Contact Lenses

PURPOSE

Tear exchange under a soft contact lens is directly related to the amount of lateral and transverse lens motion. Hydrodynamic modeling suggests that channels placed on the back surface of a soft lens will reduce fluid resistance and increase transverse lens movement. This study measured the effect of posterior lens surface scalloped channels on tear exchange.

METHODS

Tear exchange in the postlens tear film (PoLTF) was estimated using a fluorometer to measure the exponential depletion of high-MW fluorescein under the lens expressed as the time to deplete 95% of dye (T95). A total of 32 subjects wore two pairs of identical lenses except that the experimental lens had 12 scalloped channels placed radially in the midperiphery of the posterior lens surface, whereas lenses without channels served as controls.

RESULTS

The mean +/- standard error T95 values for the channel lenses was 28 +/- 2 minutes compared with 32 +/- 2 minutes for the control lenses (p = 0.107). There was a marginally significant difference in T95 between two lens groups in Asian eyes (p = 0.054).

CONCLUSION

Placing scallop-shaped channels on high-H2O content soft lenses improved the postlens tear pumping in Asian eyes.

Pseudomonas aeruginosa-induced inflammation in the rat extended-wear contact lens model

PURPOSE

To examine the early host response to Pseudomonas aeruginosa challenge in the extended contact lens-wearing rat model.

METHODS

Lewis rats were fitted with extended-wear lotrafilcon A hydrogel lenses in the left eye, and the right eye served as the control. Bacterial challenge was initiated in the experimental eye by fitting a bacteria-soaked contact lens and by topical delivery of the bacteria. On first detection of corneal opacity, slitlamp examination, histopathologic examination, viable bacteria counts, enzyme-linked immunosorbent assay, myeloperoxidase, Langerhans cell detection, and multiprobe ribonuclease protection assays were used to evaluate the early corneal response.

RESULTS

Analysis of bacterially challenged contact lens-wearing versus control rats showed Langerhans cells and polymorphonuclear neutrophils only in the experimentally challenged cornea. In addition, in the experimentally challenged cornea, ribonuclease protection and enzyme-linked immunosorbent analyses showed an upregulation of proinflammatory cytokines, including interleukins 1beta and 6, suggesting that with contact lens wear, these cytokines contribute to the early corneal response and, potentially, disease.

CONCLUSIONS

The contact lens-wearing rat model allows a unique analysis of the early effects of bacterial challenge in extended-wear contact lenses in the absence of corneal scarring, used in most rodent models. The rat model should be valuable to delineate further the effects of contact lens wear, including the testing of additional contact lens-related complications.

Staphylococcus aureus Ulcer Associated With Continuous Wear of Silicone Hydrogel Contact Lenses

PURPOSE

To report a case of culture-positive Staphylococcus aureus keratitis associated with continuous wear of lotrafilcon A lenses.

METHODS

The case report of a patient who developed microbial keratitis while wearing lotrafilcon A contact lenses is presented.

RESULTS

A 41-year-old white man had worn polymacon contact lenses successfully for at least 10 years. He habitually replaced the lenses every 1 to 2 years and frequently wore them continuously for up to 3 months. He was refitted with silicone hydrogel lenses and was advised to remove and replace the lenses monthly. Approximately 18 months later, he developed a midperipheral, culture-positive S. aureus ulcer in his right eye. He was treated with fortified cefazolin and gentamicin for 2 weeks, followed by ciprofloxacin for 2 weeks. The ulcer resolved completely. The patient's final visual acuity was 20/20 in the affected eye.

CONCLUSIONS

The increased oxygen permeability of silicone hydrogel contact lens materials may reduce the risk of hypoxic complications of continuous contact lens wear. As this case shows, however, even patients who have continuously worn lenses with very low oxygen permeability without incident can develop microbial keratitis when wearing silicone hydrogel lenses. Contact lens practitioners should inform patients of the potential risks of continuous wear and of factors that may increase those risks.

Attachment of Acanthamoeba to first- and second-generation silicone hydrogel contact lenses

PURPOSE

To investigate the attachment of Acanthamoeba to first- and second-generation silicone hydrogel contact lenses, and to determine if patient wear or the presence of a bacterial biofilm coating affects attachment characteristics.

DESIGN

Experimental study.

PARTICIPANTS AND CONTROLS

Attachment to the silicone hydrogel lenses was compared with that to a conventional hydrogel control lens. Sixteen replicates (n = 16) were carried out for unworn, worn, and biofilm-coated lenses of each type.

METHODS

Unworn, worn, and Pseudomonas aeruginosa biofilm-coated first-generation (lotrafilcon A) and second-generation (galyfilcon A) silicone hydrogel and conventional hydrogel (etafilcon A) lens quarters were incubated for 90 minutes in suspensions of plate-cultured Acanthamoeba castellanii trophozoites.

MAIN OUTCOME MEASURES

Trophozoites attached to one surface of each lens quarter were counted by direct light microscopy. Logarithmic transformation of data allowed the use of parametric analysis of variance for statistical analysis.

RESULTS

Attachment of Acanthamoeba was affected significantly by lens material type (P<0.001), with higher numbers of trophozoites attaching to the first-generation lotrafilcon A silicone hydrogel lens, compared with the second-generation galyfilcon A lens and the conventional hydrogel lens. Attachments to the latter 2 lenses did not differ significantly from each other (P = 0.126). Patient wear and the presence of a bacterial biofilm had no significant effect on attachment to the lotrafilcon A lens (P = 0.426) but did significantly increase attachment to the galyfilcon A (P<0.001) and the etafilcon A (P = 0.009) lenses; attachment to the latter 2 lenses was still significantly less than that found with the first-generation silicone hydrogel (P<0.001).

CONCLUSIONS

Acanthamoeba demonstrated a significantly greater affinity for the first-generation silicone hydrogel lens as compared with the second-generation silicone hydrogel and the conventional hydrogel. If exposed to Acanthamoeba (e.g., when showering or swimming, through noncontinuous wear and ineffective lens care regimes), first-generation silicone hydrogel lenses may promote a greater risk of Acanthamoeba infection due to the enhanced attachment characteristics of this lens material. However, prospective studies in patients are required to determine if these experimental results are clinically significant.

Investigation of the performance of the Menifocal Z gas-permeable bifocal contact lens during continuous wear

PURPOSE

The Menifocal Z is an alternating vision, concentric, bifocal gas-permeable (GP) contact lens; center distance is connected to near periphery by a smooth transition zone. The lens is produced using tisilfocon A (Menicon Z material), which is approved for up to 30 days of continuous wear (CW). The aim of this study was to evaluate the clinical performance of the Menifocal Z when worn for up to 30 days of CW for 6 months.

METHODS

Thirty-five existing GP lens wearers were enrolled in the study. Subjects were fitted with Menifocal Z lenses and follow-up visits were conducted after 2 weeks of daily wear and 1 day, 1 week, 6 weeks, 3 and 6 months of CW. A range of objective and subjective clinical performance measures were assessed, including distance and near visual acuity, the physiological response to CW, and subjective evaluation of vision and comfort.

RESULTS

Twenty-seven subjects (77%) completed the study and eight (23%) discontinued: five (14%) as a result of lens-related problems (four vision, one comfort) and three (9%) as a result of non-lens related reasons. Average CW time achieved by the subjects was 22 +/- 2 days. Mean binocular logarithm of the minimum angle of resolution (logMAR) acuities at 6 months were: high contrast distance 0.03 (20/20-), low contrast distance 0.63 (20/80-), and high contrast near 0.26 (20/25, N4). Adverse responses and lens binding were minimal, and there were no significant increases in corneal staining, corneal vascularization, or superior palpebral conjunctival papillae over time (p > 0.05). Problems with night vision (distance and near) with the lenses were the most common difficulties reported by the subjects.

CONCLUSIONS

The Menifocal Z appears to be a promising option for presbyopic vision correction, providing successful correction of distance and near vision in a group of experienced GP lens wearers. The hyper Dk tisilfocon A (Menicon Z) material allowed for safe wear of the lenses on a CW basis.

Pseudomonas aeruginosa Keratitis in an Atopic Silicone Hydrogel Lens Wearer With Rosacea

PURPOSE

This case report documents Pseudomonas aeruginosa corneal infection associated with daily wear of a silicone contact lens in a patient who also had bilateral, preexisting biomicroscopic findings of ocular rosacea, seborrheic blepharitis, keratoconjunctivitis sicca, and chronic punctate corneal epitheliopathy.

CONCLUSIONS

Collectively, these problems produce increased risk of infection for wear of any contact lens; and underscore the importance of proper patient selection, education and post-fit monitoring even when hyper-oxygen transmitting silicone hydrogels are utilized.

Adhesion of Pseudomonas aeruginosa and Staphylococcus epidermidis to Silicone???Hydrogel Contact Lenses

PURPOSE

The purpose of this study is to compare the adhesion capabilities of the most important etiologic agents of microbial ocular infection to the recently available silicone-hydrogel lenses with those to a conventional hydrogel lens.

METHODS

In vitro static adhesion assays of Pseudomonas aeruginosa 10,145, Staphylococcus epidermidis 9142 (biofilm-positive), and 12,228 (biofilm-negative) to two extended-wear silicone-hydrogel lenses (balafilcon A and lotrafilcon A), a daily wear silicone-hydrogel lens (galyfilcon A) and a conventional hydrogel (etafilcon A) were performed. To interpret the adhesion results, lens surface relative hydrophobicity was assessed by water contact angle measurements.

RESULTS

P. aeruginosa and S. epidermidis 9142 exhibited greater adhesion capabilities to the extended wear silicone-hydrogel lenses than to the daily wear silicone- and conventional hydrogel lenses (p < 0.05). No statistical differences were found between the adhesion extent of these strains to galyfilcon A and etafilcon A. The biofilm negative strain of S. epidermidis adhered in larger extents to the silicone-hydrogel lenses than to the conventional hydrogel (p < 0.05), but in much lower amounts than the biofilm-positive strain. The water contact angle measurements revealed that the extended wear silicone-hydrogel lenses are hydrophobic, whereas the daily wear silicone- and conventional hydrogel lenses are hydrophilic.

CONCLUSIONS

As a result of their hydrophobicity, the extended wear silicone-hydrogel lenses (lotrafilcon A and balafilcon A) may carry higher risk of microbial contamination than both the hydrophilic daily wear silicone-hydrogel lens, galyfilcon A and the conventional hydrogel lens, etafilcon A.

Survey of Contact Lens-Wearing Habits and Attitudes Toward Methods of Refractive Correction: 2002 versus 2004

PURPOSE

The purpose of this study is to measure patient attitudes toward methods of refractive correction among cross-sectional populations of contact lens wearers in 2002 and 2004 at the School of Optometry contact lens clinic at Indiana University. We also assessed the role of age and gender on these attitudes.

METHODS

Attitudes toward methods of refractive correction were surveyed among 349 consecutive contact lens wearers in the spring of 2002 and compared with surveyed attitudes among 99 contact lens wearers in the winter of 2004. The 23 questions in the survey queried attitudes on the health and safety, cost, and interest in methods of refractive correction in addition to questions about the wearing schedule for the subjects' current contact lenses (CL). Refractive methods that were compared included glasses, daily wear CL (DW), 7-day extended wear (EW) CL, 30-day continuous wear (CW) CL, LASIK, and orthokeratology (OK). The proportion of answers citing "agree" or "strongly agree" were combined and analyzed by chi-squared tests comparing the results for stratified groups in the previous and the current survey. The groups were stratified by gender and age over of under 30 years. Significance level was set at p < or = 0.05.

RESULTS

In the 2004 survey, the age of the subjects was significantly younger. Subjects' interest in EW increased significantly in 2004 (59% vs. 45% with high level of interest 2004 vs. 2002, respectively; p = 0.015) and the proportion of subjects reporting overnight wear increased significantly (DW = 58% vs. 69% 2004 vs. 2002, p = 0.0017, controlling for age and gender). In 2004, glasses and EW CL were rated as more healthy compared with 2002 (glasses 95% vs. 88%, p = 0.05; EW CL 48% vs. 34%, p = 0.005). Males are now less likely in 2004 to rate EW as healthy compared with females (38% vs. 53%, p = 0.01). In the 2004 survey, subjects over age 30 were significantly less interested in LASIK compared with those under age 30 (59% vs. 33%, p = 0.02) and less interested than they were in 2002.

CONCLUSIONS

In the 2004 survey, significantly more subjects reported overnight lens wear, an increased interest in, and opinion of overnight wear as a healthy method of refractive correction compared with the 2002 survey. There was some dampening of enthusiasm for LASIK among subjects over 30 years of age in the 2004 survey. Age and gender can influence attitudes toward refractive correction, with females in this sample showing the most change over time, most probably as a result of different health information sources used by various demographic groups.

Bacterial Populations on Silicone Hydrogel and Hydrogel Contact Lenses after Swimming in a Chlorinated Pool

PURPOSE

A number of reports have indicated an association between swimming with contact lenses and subsequent eye infection. This study tests whether a hydrophilic contact lens worn while swimming accumulates bacteria present in the water. It was of interest to determine whether lens type (silicone hydrogel vs. hydrogel) affected the result.

METHODS

Fifteen healthy noncontact lens wearers swam for 30 minutes with a silicone hydrogel lens (PureVision, Bausch & Lomb, Rochester, NY) on one eye and a hydrogel lens (Acuvue 2, Vistakon Inc., Jacksonville, FL) on the other. Lenses were removed aseptically and placed in sterile vials 10 minutes after the subjects left the water. Microbial growth was enumerated for total numbers of colonies and categorized by species present. Numbers of colonies were compared between the two lens groups and with a water sample taken from the pool at the time of the experiment. Eight of the subjects returned on a different day and wore new lenses for 50 minutes in normal room conditions.

RESULTS

Two lenses were lost while swimming. Twenty-seven of the remaining 28 lenses worn while swimming showed colonization, principally with Staphylococcus epidermidis, which was also by far the most common species identified from the water itself. Small numbers of Staphylococcus aureus and Streptococcus salivarius were also present in the water and on the lenses. Numbers of colonies varied among subjects (range, 0 to 230), but no differences were observed between the two lens groups. Lenses removed after 30 minutes of wear without swimming were mostly sterile, with 3 of 16 lenses showing just two colonies each.

CONCLUSION

It appears that wearing a hydrophilic lens while swimming allows accumulation of microbial organisms on or in the lens, regardless of lens material. Swimmers should be advised to wear tight-fitting goggles if lenses are worn while swimming, and thorough disinfection of the lenses before overnight wear seems prudent.

Hypoxia increases corneal cell expression of CFTR leading to increased Pseudomonas aeruginosa binding, internalization, and initiation of inflammation

PURPOSE

To investigate the effect of hypoxia-induced molecular responses of corneal epithelial cells on the surface of rabbit and human corneas and corneal cells in culture on interactions with Pseudomonas aeruginosa that may underlie increased susceptibility to keratitis.

METHODS

Organ cultures of rabbit and human corneal tissue, primary rabbit and human corneal cells, and transformed human corneal cells from a patient with cystic fibrosis and the same cell line corrected for expression of wild-type cystic fibrosis transmembrane conductance regulator (CFTR), the cellular receptor for P. aeruginosa, were exposed to hypoxic conditions for 24 to 72 hours. Changes in binding and internalization of P. aeruginosa were measured using cellular association and gentamicin-exclusion assays, and expression of CFTR and activation of NF-kappaB in response to hypoxia were determined by confocal laser microscopy and quantitative measurements of NF-kappaB activation.

RESULTS

Hypoxia induced in a time- and oxygen-concentration-dependent manner increased association and internalization of clinical isolates of P. aeruginosa in all cells tested. Hypoxia increased CFTR expression and NF-kappaB nuclear translocation in rabbit and human cells with wild-type CFTR. Corneal cells lacking CFTR had reduced NF-kappaB activation in response to hypoxia. Hypoxia did not affect the increase in corneal cell CFTR levels or NF-kappaB activation after P. aeruginosa infection.

CONCLUSIONS

Hypoxic conditions on the cornea exacerbate the binding and internalization of P. aeruginosa due to increased levels of CFTR expression and also induce basal NF-kappaB activation. Both of these responses probably exacerbate the effects of P. aeruginosa infection by allowing lower infectious doses of bacteria to induce disease and promote destructive inflammatory responses.

Non-compliance with lens care and maintenance in diabetic contact lens wearers

We hypothesize that diabetic contact lens wearers may represent a special group displaying higher levels of compliance with their lens care regimens as a result of learned behaviour relating to maintenance of their diabetic condition. To test this hypothesis, a prospective, single centre, controlled, masked study was performed whereby 29 diabetic contact lens patients and 29 non-diabetic control subjects were issued with disposable hydrogel contact lenses and a multipurpose lens care regimen. All participants were given identical instruction on lens care and maintenance. Compliance levels were assessed at a 12-month aftercare appointment by demonstration and questionnaire. Twenty-four different aspects of compliance were scored, 12 by observation and 12 by questionnaire report, of which only two showed a significant difference between the diabetic and control groups. Although the combined population of contact lens wearers was generally compliant, there were examples of non-compliance in both groups. Neither the duration of diabetes nor the degree of metabolic control appeared to have a significant effect on compliance. The results suggest that eye care practitioners cannot assume that diabetic patients will be more compliant with contact lens care and maintenance than non-diabetic patients.

Evaluation of surveillance methods for an epidemiological study of contact lens related microbial keratitis

PURPOSE

To evaluate surveillance methods in a pilot epidemiological study of contact lens related microbial keratitis (MK) cases identified by ophthalmic practitioners in Australia and New Zealand between May and August 2003 inclusive.

METHODS

Twelve ophthalmologists and 55 optometrists from rural and metropolitan locations were sent a study information pack with postal reporting forms. After 2 months, practitioners were emailed a link to a website for Internet reporting. After 4 months, practitioners were prompted by email and then by telephone if a response was not received. Passive response rates were the rate of returns after posting information and emailing the website link. Active response rates included personalized email and telephone follow-up.

RESULTS

Ten cases of MK were identified by optometrists and five by ophthalmologists. The passive response rates were 79% and 58% for the first and second reporting periods, respectively. There was a lower response rate in the second reporting period compared to the first (P = 0.02). With active surveillance the response rate increased to 97% and 96%. A large proportion of optometrists (62%) and ophthalmologists (55%) used the website for at least one reporting period. Internet reporting was used by all New Zealand practitioners (5/5).

CONCLUSIONS

A surveillance study to estimate the incidence of contact lens related MK in Australia and New Zealand is feasible and acceptable. Internet-based reporting offers a reliable, rapid and cost-effective means of running a large scale, international surveillance study. Active surveillance methods are necessary to enhance reporting rates.