Antibacterial and physical properties of a novel sonochemical-assisted Zn-CuO contact lens nanocoating.

PURPOSE: This work examined the antibacterial and physical effects of a novel Zn-CuO nanocoating applied on a silicone hydrogel contact lens. METHODS: Zn-CuO coating of PureVision balafilcon-A soft contact lenses (Bausch&Lomb, Rochester, NY) was performed by sonochemical deposition using a high-intensity ultrasonic horn. Non-coated PureVision lenses served as a control in all experiments. Adhesion assays for P. aerueginosa and S. epidermidis to the coated lenses were performed to identify the minimal coating concentration which still possessed antibacterial activity. Lens water content, oxygen transfer light transfer, leaching, and electron microscopy studies were performed using this concentration. RESULTS: Coated lenses showed 3-5 log reductions in adhesion of both species. The lowest tested coating concentration of 0.02 wt% led to a log reduction of 3.25 ± 1.25 of P. aeruginosa CFU/lens (P = 0.007) and a log reduction of 4.37 ± 0.75 of S. epidermidis (p = 0.0007). Using this coating concentration, water content (36%, 33.6%), oxygen transfer (87.22 ± 10.96, 92.18 ± 2.38, × 10-11(cm2/s)(mlO2)/(ml × mmHg)), p = 0.12), and light transfer properties did not differ significantly between the coated and the control contact lenses. In the range of 380-780 nm wavelength, the coated lenses transmitted 96.47 ± 1.52% while the control lenses transmitted 97.36 ± 1.35%. The corresponding values for the range of 300-380 nm wavelength were 79.343 ± 8.754 and 80.169 ± 1.35. Leaching studies for 0.5 mM coated lenses have demonstrated the excellent stability of the coating with the release of only 0.005% of the coating after 1 week of exposure to the test solution. CONCLUSION: Sonochemical-assisted nanocoating of contact lenses showed significant and consistent antibacterial activity while preserving the basic properties of a silicone hydrogel contact lens.

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.

Effect of Daily Contact Lens Cleaning on Ocular Adverse Events during Extended Wear.

PURPOSE: The purpose of the study was to assess what effect daily cleaning of contact lenses with a multipurpose disinfection solution (MPDS), during 30 nights extended wear, would have on contact lens-related adverse events. METHODS: This was a prospective, open-label, randomized, controlled, parallel-group, 3-month clinical study in which 193 participants were dispensed with lotrafilcon A silicone hydrogel lenses for a 30-day extended-wear schedule and with lenses replaced monthly. Participants were randomized to a control or test group. Test subjects were required to remove lenses daily after waking, clean them with the MPDS, and reinsert the lenses. Control subjects wore lenses without removal for 30 days extended wear. Handling-related lens contamination was assessed at the baseline visit. RESULTS: There was no significant difference between the test and control groups for the incidence of significant corneal infiltrative events (1.3 vs. 4.9%, p = 0.368), total corneal infiltrative events (2.6 vs. 4.9%, p = 0.682), or mechanical events (1.3 vs. 2.5%, p = 1.00). The test group had greater corneal staining (p < 0.047) and fewer mucin balls (p = 0.033). Handling-related lens contamination (unworn lenses) resulted in isolation of Gram-positive bacteria from 92.5% of test lenses compared with 87.5% of control lenses (p = 0.712). Gram-negative bacteria were isolated from 5% of test subjects compared with 2.5% of control subjects (p = 1.00). Fungus was isolated from 2.5% of subjects in both the test and control groups (p = 1.00). CONCLUSIONS: The intervention of daily morning cleaning of the lens surface with an MPDS during extended wear did not significantly influence the incidence of adverse events.

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.

Microbial keratitis secondary to unintended poor compliance with scleral gas-permeable contact lenses.

PURPOSE: To report a case of neurotrophic keratitis in which scleral contact lenses improved vision from 20/100 to 20/20, however, due to poor lens care, an incident of microbial keratitis developed. METHODS: A 64-year-old man with an ocular history of neurotrophic keratitis secondary to herpes simplex in each eye was successfully fit with scleral lenses. He subsequently developed microbial keratitis due to a number of risk factors. RESULTS: The lesion was culture negative, yet was very responsive to treatment with moxifloxacin. The lesion fully healed, and the patient did not suffer additional vision loss. CONCLUSIONS: This case demonstrates the ability of scleral lenses to correct visual impairments secondary to poor epithelial integrity and illustrates the importance of the practitioner providing detailed lens care instruction.

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.

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.

Effect of phospholipid deposits on adhesion of bacteria to contact lenses.

PURPOSE: Protein and lipid deposits on contact lenses may contribute to clinical complications. This study examined the effect of phospholipids on the adhesion of bacteria to contact lenses. METHODS: Worn balafilcon A (n = 11) and senofilcon A (n = 11) were collected after daily wear and phospholipids were extracted in chloroform:methanol. The amount of phospholipid was measured by electrospray ionization mass spectrometry. Unworn lenses soaked in phospholipids were exposed to Pseudomonas aeruginosa and Staphylococcus aureus. After 18 h incubation, the numbers of P. aeruginosa or S. aureus that adhered to the lenses were measured. Phospholipid was tested for possible effects on bacterial growth. RESULTS: A broad range of sphingomyelins (SM) and phosphatidylcholines (PC) were detected from both types of worn lenses. SM (16:0) (m/z 703) and PC (34:2) (m/z 758) were the major phospholipids detected in the lens extracts. Phospholipids did not alter the adhesion of any strain of P. aeruginosa or S. aureus (p > 0.05). Phospholipids (0.1 mg/mL) showed no effect on the growth of P. aeruginosa 6294 or S. aureus 031. CONCLUSIONS: Phospholipids adsorb/absorb to contact lenses during wear, however, the major types of phospholipids adsorbed to lenses do not alter bacterial adhesion or growth.

Effect of cholesterol deposition on bacterial adhesion to contact lenses.

PURPOSE: To examine the effect of cholesterol on the adhesion of bacteria to silicone hydrogel contact lenses. METHODS: Contact lenses, collected from subjects wearing Acuvue Oasys or PureVision lenses, were extracted in chloroform:methanol (1:1, v/v) and amount of cholesterol was estimated by thin-layer chromatography. Unworn lenses were soaked in cholesterol, and the numbers of Pseudomonas aeruginosa strains or Staphylococcus aureus strains that adhered to the lenses were measured. Cholesterol was tested for effects on bacterial growth by incubating bacteria in medium containing cholesterol. RESULTS: From ex vivo PureVision lenses, 3.4 ± 0.3 µg/lens cholesterol was recovered, and from Acuvue Oasys lenses, 2.4 ± 0.2 to 1.0 ± 0.1 µg/lens cholesterol was extracted. Cholesterol did not alter the total or viable adhesion of any strain of P. aeruginosa or S. aureus (p > 0.05). However, worn PureVision lenses reduced the numbers of viable cells of P. aeruginosa (5.8 ± 0.4 log units) compared with unworn lenses (6.4 ± 0.2 log units, p = 0.001). Similarly, there were fewer numbers of S. aureus 031 adherent to worn PureVision (3.05 ± 0.8 log units) compared with unworn PureVision (4.6 ± 0.3 log units, p = 0.0001). Worn Acuvue Oasys lenses did not affect bacterial adhesion. Cholesterol showed no effect on the growth of any test strain. CONCLUSIONS: Although cholesterol has been shown to adsorb to contact lenses during wear, this lipid does not appear to modulate bacterial adhesion to a lens surface.

Corneal erosions, bacterial contamination of contact lenses, and microbial keratitis.

OBJECTIVES: To estimate the rate of corneal erosion coupled with gram-negative bacterial contamination of contact lenses and compare this with the rate of microbial keratitis (MK) with contact lenses. METHODS: The rate of corneal erosion and contact lens contamination by gram-negative bacteria were calculated from several prospective trials. These rates were used to calculate the theoretical rate of corneal erosion happening at the same time as wearing a contact lens contaminated with gram-negative bacteria. This theoretical rate was then compared with the rates of MK reported in various epidemiological and clinical trials. RESULTS: Corneal erosions were more frequent during extended wear (0.6-2.6% of visits) compared with daily wear (0.01-0.05% of visits). No corneal erosions were observed for lenses worn on a daily disposable basis. Contamination rates for lenses worn on a daily disposable basis were the lowest (2.4%), whereas they were the highest for low Dk lenses worn on an extended wear basis (7.1%). The estimated rate of corneal erosions occurring at the same time as wearing lenses contaminated with gram-negative bacteria was the lowest during daily wear of low Dk lenses (1.56/10,000 [95% CI: 0.23-10.57]) and the highest during extended wear of high Dk lenses (38.55/10,000 [95% CI: 24.77-60.04]). These rates were similar in magnitude to the rates reported for MK of different hydrogel lenses worn on differing wear schedules. CONCLUSION: The coincidence of corneal erosions during lens wear with gram-negative bacterial contamination of lenses may account for the relative incidence of MK during lens wear with different lens materials and modes of use.

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.

Risk factors for contact lens bacterial contamination during continuous wear.

PURPOSE: Microbial contamination of contact lenses is associated with corneal infection and inflammation. This study determined the microbiological, clinical, and demographic factors that are associated with bacterial contamination of a silicone hydrogel contact lens when worn for continuous wear (CW). METHODS: Two hundred five healthy subjects were enrolled in the Longitudinal Analysis of Silicone Hydrogel Contact Lens Study and were fitted with lotrafilcon A lenses for monthly CW and followed for 1 year. Lenses were aseptically removed after 1 week and 4 months of wear and cultured using an agar sandwich technique. Lids and conjunctiva were routinely cultured at baseline and after 1 week and 4 months of CW. Lenses and ocular sites were considered to have substantial microbial bioburden when they harbored pathogenic organisms or high levels of commensal organisms. Univariate and multivariate logistic regression analyses were conducted to examine whether substantial conjunctival or lid bioburden, subject demographics, lens-wearing history, symptoms, and biomicroscopic signs were associated with lens bioburden. RESULTS: About one third (32.4%) of subjects had substantial bacterial bioburden in either eye across multiple visits. Over half (53.2%) and about one tenth (11.7%) of subjects had substantial lid and conjunctival bioburden, respectively, and 11.2% discontinued because of discomfort. The adjusted odds ratios (and 95% confidence intervals) for presence of substantial lens bioburden were 2.49 (1.17-5.30), 4.24 (1.45-12.40), and 4.11 (1.17-14.46) for substantial lid bioburden, substantial conjunctival bioburden, and lens discomfort, respectively. CONCLUSIONS: Bacterial contamination of silicone hydrogel contact lenses is common during CW. Substantial lens bioburden is associated with discomfort precluding successful CW. The presence of substantial lid and conjunctival bioburden is associated with a 2.5-fold and more than fourfold greater risk of substantial lens bioburden and is likely the major route of contamination.

Adhesion of Pseudomonas aeruginosa to orthokeratology and alignment lenses.

PURPOSE: To determine whether contact lenses designed for orthokeratology (OK) are colonized by greater numbers of bacteria compared with standard (alignment fitted) design rigid gas permeable lenses before and after lens wear. METHODS: Eighteen 1-year-old cats were randomly fitted with an OK lens in one eye and an alignment fitted (AF) lens in the other eye. Both lenses were made in the same diameter and central thickness and of the same material. Two separate wearing periods of 2 weeks and 6 weeks were used. After each wearing period, lenses were soaked in Pseudomonas aeruginosa (6294 or 6206) for 10 min. The lenses were then reinserted onto their respective corneas for a wearing period of 16 hours after which lenses were collected and remaining adhered bacteria quantified. Unworn control lenses were also soaked and bacteria enumerated for comparison. RESULTS: There were no significant differences in the number of bacteria adherent to unworn AF and OK lenses. Analysis of lenses after wear showed OK lenses retained significantly higher numbers of viable bacteria than AF lenses in all studies. CONCLUSIONS: OK lenses retain more bacteria than AF rigid gas permeable lenses after bacteria-loaded overnight lens wear. This may increase the risk for an infection in OK patients should suitable conditions be present. Specific education on the cleaning of OK lenses is essential.

[Pseudomonas aeruginosa keratitis associated with the use of last generation contact lens made of silicone hydrogel: case report]. / Queratitis por Pseudomonas aeruginosa asociada al uso de lentes de contacto de hidrogel de silicona de última generación: Reporte de un caso.

We report the case of a female patient, 56-year-old housewife, for the first time user of last generation contact lenses: Lotrafilcon B, which presented a severe corneal ulcer by Pseudomonas aeruginosa in hev left eye and subsequently required keratoplasty. Initially she reported pain and arrived at the emergency department with red eye, corneal central ulcer of three days of evolution and hypopion. Initially she received topic mydriatic drugs and prednisolone at 1%. At the next day the ophthalmologycal exam showed hypopion at 5% and a central severe ulcer greater than 3 mm in diameter with sharp edges and mucopurulent secretion. The treatment was changed to moxifloxacin and natamycin. The microbiological analysis performed in two laboratories yielded Aspergillus sp. and Pseudomonas aeruginosa sensitive to ciprofloxacin, tobramycin, gentamicin and moxifloxacin. The presence of Aspergillus was interpreted as a pollution lens case and likely colonization of the cornea because of the patient good performance. After four months although improving she required corneal transplantation. Photographic documentation of the case under illumination with slit lamp is presented.

Queratitis por Pseudomonas aeruginosa asociada al uso de lentes de contacto de hidrogel de silicona de última generación: Reporte de un caso / Pseudomonas aeruginosa keratitis associated with the use of last generation contact lens made of silicone hydrogel: case report

We report the case of a female patient, 56-year-old housewife, for the first time user of last generation contact lenses: Lotrafilcon B, which presented a severe corneal ulcer by Pseudomonas aeruginosa in hev left eye and subsequently required keratoplasty. Initially she reported pain and arrived at the emergency department with red eye, corneal central ulcer of three days of evolution and hypopion. Initially she received topic mydriatic drugs and prednisolone at 1 percent. At the next day the ophthalmologycal exam showed hypopion at 5 percent and a central severe ulcer greater than 3 mm in diameter with sharp edges and mucopurulent secretion. The treatment was changed to moxifloxacin and natamycin. The microbiological analysis performed in two laboratories yielded Aspergillus sp. and Pseudomonas aeruginosa sensitive to ciprofloxacin, tobramycin, gentamicin and moxifloxacin. The presence of Aspergillus was interpreted as a pollution lens case and likely colonization of the cornea because of the patient good performance. After four months although improving she required corneal transplantation. Photographic documentation of the case under illumination with slit lamp is presented.

Se comunica el caso de una paciente mujer, de 56 años de edad, ama de casa, usuaria por primera vez de lentes de contacto de última generación: lotrafilcon B, que presentó una úlcera corneal grave por Pseudomonas aeruginosa en su ojo izquierdo y posteriormente requirió quera toplastía. Inicialmente reportó dolor y llegó a la unidad de urgencia con ojo rojo, úlcera corneal central de tres días de evolución e hipopión. El tratamiento farmacológico inicial fue con midriático y prednisolona al 1 por ciento. La valoración oftalmológica del día siguiente demostró hipopión al 5 por ciento y úlcera central grave mayor a 3 mm de diámetro con bordes definidos y secreción mucopurulenta. Se cambió tratamiento a moxifloxacina y natamicina. El análisis microbiológico en dos laboratorios, confirmó el aislado de Aspergillus sp y Pseudomonas aeruginosa; esta última sensible a ciprofloxacina, tobramicina, gentamicina y moxifloxacina. La presencia de Aspergillus se interpretó como contaminación del estuche y probable colonización de la cornea por la clínica y buena evolución. A los cuatro meses de evolución, aunque presentó mejoría, requirió trasplante corneal. Se incluye documentación fotográfica del caso bajo iluminación con lámpara de hendidura.

Isolation of coagulase-negative staphylococci from extended-wear soft contact lenses in asymptomatic patients.

BACKGROUND: Coagulase-negative staphylococci and diphtheroids are normal inhabitants of the outer surface of the human eye. These microorganisms serve as part of the defense mechanism of the ocular anatomy in preventing colonization and infection by pathogenic bacteria. Nevertheless, infections associated with contaminated solutions and cases became serious problems for people who wear soft contact lenses. The aim of this study is to isolate and identify aerobic bacteria, particularly, gram-negative species associated with the use of extended-wear soft contact lenses. METHODS: Extended-wear contact lenses were collected, using aseptic technique, from the eyes of individuals after 30 days of extended wear (5-7 day intermittent periods) and were examined for adhered aerobic bacteria. RESULT: Coagulase-negative staphylococci were isolated from 74% of the lenses. Serratia marcescens was found at an incidence of 10% and Pseudomonas aeruginosa at an incidence of 6%. CONCLUSIONS: The presence of species of bacteria, including P. aeruginosa and S. marcescens, which have been associated with daily wear soft contact lenses, solutions, and cases also seem to be associated with extended-wear lenses.

Infectious keratitis.

PURPOSE OF REVIEW: Infectious keratitis is a medical emergency. Improper management can lead to marked loss of vision. This review identifies recent trends in the study of infectious keratitis. RECENT FINDINGS: A multicountry outbreak of Fusarium keratitis emphasizes that contact lens wear is a major risk factor for infectious keratitis. Acanthamoeba and fungal keratitis are the most expensive forms of infectious keratitis to treat. Noninvasive methods and molecular techniques have improved diagnosis of infectious keratitis. Fortified topical antibiotics and fluoroquinolones are still the mainstay of bacterial keratitis therapy. Voriconazole and new routes of administration of conventional antifungals appear promising for fungal keratitis. Antivirals and amelioration of host inflammatory response are promising for viral keratitis; the host response is also crucial in pathogenesis of Pseudomonas aeruginosa keratitis. Trauma-induced bacterial and fungal keratitis and contact lens-associated keratitis are preventable entities. SUMMARY: Improved modalities of diagnosis and treatment have improved the outcome of infectious keratitis, but therapy of acanthamoebal, fungal and P. aeruginosa keratitis is still a challenge. Effective strategies must neutralize potential risk factors and counter host response overactivity without impairing killing of infecting microorganisms. Trauma-induced bacterial and fungal keratitis can be prevented.

Pseudomonas aeruginosa infection and inflammation during contact lens wear: a review.

Infection and inflammation during contact lens wear is often associated with microbial contamination of lenses. Several different types of microbes that colonize lenses can lead to infection and inflammation, but the most common cause of infection (microbial keratitis; MK) remains the Gram-negative bacterium Pseudomonas aeruginosa. P. aeruginosa has a battery of cell-associated and extracellular virulence factors it can use to initiate and maintain infection. Its ability to produce proteases, to either invade or kill corneal cells, and to coordinate expression of virulence factors via quorum-sensing have been shown to be important during MK. Another important factor that contributes to the destruction of the cornea during MK is excessive activation of the host defense system. P. aeruginosa can activate several pathways of the immune system during MK, and activation often involves receptors on the corneal epithelial cells called toll-like receptors (TLRs). These TLRs recognize e.g., lipopolysaccharide or flagella from P. aeruginosa and activate the epithelial cells to produce inflammatory mediators such as cytokines and chemokines. These cytokines or chemokines recruit white blood cells, predominantly polymorphonuclear leukocytes, to the infection in order that they can phagocytose and kill the P. aeruginosa. However, continued recruitment and presence of these polymorphonuclear neutrophils and other white blood cells in the corneal tissue leads to destruction of corneal cells and tissue components. This can ultimately lead to scarring and vision loss.

Contact lenses: optimal vision--sub-optimal carrier?

The development of silicone hydrogel contact lenses with high oxygen permeabilities is a major step forward in vision correction. This advance in contact lenses material technology provides breakthrough levels of oxygen to the cornea. However, there are still important issues yet to be addressed by researchers, practitioners, and industry. Factors such as adequate correction for all refractive errors, microbial keratitis, comfort, and suitable lens care and lens biocompatibility are discussed from the authors' perspective.