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

Rational design of antibiotic-free antimicrobial contact lenses: Trade-offs between antimicrobial performance and biocompatibility

Microbial keratitis associated with contact lenses (CLs) wear remains a significant clinical concern. Antibiotic therapy is the current standard of care. However, the emergence of multidrug-resistant pathogens necessitates the investigation of alternative strategies. Antibiotic-free antimicrobial contact lenses (AFAMCLs) represent a promising approach in this regard. The effectiveness of CLs constructed with a variety of antibiotic-free antimicrobial strategies against microorganisms has been demonstrated. However, the impact of these antimicrobial strategies on CLs biocompatibility remains unclear. In the design and development of AFAMCLs, striking a balance between robust antimicrobial performance and optimal biocompatibility, including safety and wearing comfort, is a key issue. This review provides a comprehensive overview of recent advancements in AFAMCLs technology. The focus is on the antimicrobial efficacy and safety of various strategies employed in AFAMCLs construction. Furthermore, this review investigates the potential impact of these strategies on CLs parameters related to wearer comfort. This review aims to contribute to the continuous improvement of AFAMCLs and provide a reference for the trade-off between resistance to microorganisms and wearing comfort. In addition, it is hoped that this review can also provide a reference for the antimicrobial design of other medical devices.

A Narrative Review of Acanthamoeba Isolates in Malaysia: Challenges in Infection Management and Natural Therapeutic Advancements

Acanthamoeba, a free-living amoeba (FLA) found in diverse ecosystems, poses significant health risks globally, particularly in Malaysia. It causes severe infectious diseases, e.g., Acanthamoeba keratitis (AK), primarily affecting individuals who wear contact lenses, along with granulomatous amoebic encephalitis (GAE), a rare but often life-threatening condition among immunocompromised individuals. AK has become increasingly prevalent in Malaysia and is linked to widespread environmental contamination and improper contact lens hygiene. Recent studies highlight Acanthamoeba's capacity to serve as a "Trojan horse" for amoeba-resistant bacteria (ARBs), contributing to hospital-associated infections (HAIs). These symbiotic relationships and the resilience of Acanthamoeba cysts make treatment challenging. Current diagnostic methods in Malaysia rely on microscopy and culture, though molecular procedures like polymerase chain reaction (PCR) are employed for more precise detection. Treatment options remain limited due to the amoeba's cyst resistance to conventional therapies. However, recent advancements in natural therapeutics, including using plant extracts such as betulinic acid from Pericampylus glaucus and chlorogenic acid from Lonicera japonica, have shown promising in vitro results. Additionally, nanotechnology applications, mainly using gold and silver nanoparticles to enhance drug efficacy, are emerging as potential solutions. Further, in vivo studies and clinical trials must validate these findings. This review highlights the requirement for continuous research, public health strategies, and interdisciplinary collaboration to address the growing threat of Acanthamoeba infections in Malaysia while exploring the country's rich biodiversity for innovative therapeutic solutions.

Biological characteristics and pathogenicity of Acanthamoeba

Acanthamoeba is an opportunistic protozoa, which exists widely in nature and is mainly distributed in soil and water. Acanthamoeba usually exists in two forms, trophozoites and cysts. The trophozoite stage is one of growth and reproduction while the cyst stage is characterized by cellular quiescence, commonly resulting in human infection, and the lack of effective monotherapy after initial infection leads to chronic disease. Acanthamoeba can infect several human body tissues such as the skin, cornea, conjunctiva, respiratory tract, and reproductive tract, especially when the tissue barriers are damaged. Furthermore, serious infections can cause Acanthamoeba keratitis, granulomatous amoebic encephalitis, skin, and lung infections. With an increasing number of Acanthamoeba infections in recent years, the pathogenicity of Acanthamoeba is becoming more relevant to mainstream clinical care. This review article will describe the etiological characteristics of Acanthamoeba infection in detail from the aspects of biological characteristic, classification, disease, and pathogenic mechanism in order to provide scientific basis for the diagnosis, treatment, and prevention of Acanthamoeba infection.

The role of Acanthamoeba spp. in biofilm communities: a systematic review

Acanthamoeba spp. have always caused disease in immunosuppressed patients, but since 1986, they have become a worldwide public health issue by causing infection in healthy contact lens wearers. Amoebae of the Acanthamoeba genus are broadly distributed in nature, living either freely or as parasites, and are frequently associated with biofilms throughout the environment. These biofilms provide the parasite with protection against external aggression, thus favoring its increased pathogeny. This review aims to assess observational studies on the association between Acanthamoeba spp. and biofilms, opening potential lines of research on this severe ocular infection. A systematic literature search was conducted in May 2020 in the following databases: PubMed Central^®/Medline, LILACS, The Cochrane Library, and EMBASE^®. The studies were selected following the inclusion and exclusion criteria specifically defined for this review. Electronic research recovered 353 publications in the literature. However, none of the studies met the inclusion criterion of biofilm-producing Acanthamoeba spp., inferring that the parasite does not produce biofilms. Nonetheless, 78 studies were classified as potentially included regarding any association of Acanthamoeba spp. and biofilms. These studies were allocated across six different locations (hospital, aquatic, ophthalmic and dental environments, biofilms produced by bacteria, and other places). Acanthamoeba species use biofilms produced by other microorganisms for their benefit, in addition to them providing protection to and facilitating the dissemination of pathogens residing in them.

Evaluation of commercial soft contact lenses for ocular drug delivery: A review

Soft contact lenses have generated growing interest in ocular drug delivery due to their potential to enhance drug bioavailability in ocular tissues. Commercially available soft contact lenses offer several advantages for ocular drug delivery as they are manufactured on a large scale, which guarantees the availability of a consistent and reproducible product, and their favorable safety profile is well-established through broad clinical use. Here we review the rationale for using commercially available soft contact lenses for ocular drug delivery; summarize the evolution of the materials used in contact lens fabrication; and explore various methods used to improve the drug release characteristics and its tissue penetration. While significant progress has been made, several issues still require further attention for the commercial launch of a viable drug-eluting contact lens product, including control of initial burst release, shelf-life stability, and drug loss during processing or storage.

Silver Nanoparticles as a Novel Potential Preventive Agent against Acanthamoeba Keratitis

Free living, cosmopolitan amoebae from Acanthamoeba genus present a serious risk to human health. As facultative human parasites, these amoebae may cause Acanthamoeba keratitis (AK). Acanthamoeba keratitis is a severe, vision-threatening corneal infection with non-specific symptoms. The number of reported AK cases worldwide has been increasing every year. Moreover, 90% of Acanthamoeba keratitis cases are related to contact lens use. Wearing and storage contact lenses not in accordance with the physicians and manufacturers recommendations are the primary key risk factors of this disease. Amoebae can easily adhere to the contact lens surface and transmit to the corneal epithelium. Preventing amoebae adhesion to the contact lens surface could significantly decrease the number of AK infections. Until now, the effective therapy against AK is still under development. Currently proposed therapies are mainly limited to the chlorhexidine digluconate combined with propamidine isethionate or hexamidine applications, which are insufficient and very toxic to the eye. Due to lack of effective treatment, looking for new potential preventive agents is crucial to decrease the number of Acanthamoeba keratitis infections, especially among contact lens users. Nanoparticles have been already included in several novel therapies against bacteria, viruses, fungi, and protist. However, their anti-amoebic potential has not been fully tested yet. The aim of this study was to assess silver nanoparticles (AgNPs) and platinum nanoparticles (PtNPs) anti-amoebic activity and influence on the amoebae adhesion to the surface of four different groups of contact lenses-classified according to the Food and Drugs Administration (FDA) guidelines. The obtained results show that both tested nanoparticles were effective against Acanthamoeba trophozoites and decreased the amoebae adhesion to the contact lens surface. AgNPs showed better anti-amoebic activity to cytotoxicity dependence and reduced amoebae adhesion in a wider spectrum of the tested contact lenses. Our studies also confirmed that ionization next to hydration of the contact lens material is a crucial parameter influencing the Acanthamoeba adhesion to the contact lens surface. In conclusion, silver nanoparticles might be considered as a novel preventive agent against Acanthamoeba keratitis infection.

In Vitro Evaluation of Adhesion of Two Acanthamoeba Strains to Cosmetic Contact Lenses

PURPOSE

To evaluate the factors affecting the adhesion of Acanthamoeba trophozoites to the surface of cosmetic contact lenses (CCLs).

METHODS

Acanthamoeba castellanii and A. hatchetti trophozoites were inoculated onto CCLs (hema copolymer [HM] [38.5% H2O], phemfilcon [PF] [55% H2O], polymacon [PM] [38% H2O], polyhema [PH] [%42 H2O], and hema [HM55] [55% H2O]), and the number of trophozoites adhered to the lens surfaces was assessed over time, that is, at 15 min, 1, and 24 hr. In addition, scanning electron microscopy (SEM) analysis of the lens surfaces was performed to evaluate the effect of lens surface topology on adhesion.

RESULTS

The number of amoeba adhered to the contact lens surface was found lower with PF and PH production materials, than lenses with HM, PM, and HM55 production materials (P<0.05). No significant difference was detected in amoebic strains adhered in all the contact lens types (P>0.05). No significant difference was found on average amoeba adhesion between contact lenses with hema production material but with different water contents (45%, 55%), to see the effect of water content on amoebic adhesion (P>0.05). As a result of SEM analysis, surface topology showed no effect on adhesion.

CONCLUSION

(1) Chemical composition of lenses seemed to be mostly responsible for the adhesion of Acanthamoeba. (2) Different numbers of trophozoites, obtained after the adhesion experiment, could also indicate that adherence capacity can also differ among Acanthamoeba species.

Acanthamoeba keratitis: confirmation of the UK outbreak and a prospective case-control study identifying contributing risk factors

BACKGROUND/AIMS

Acanthamoeba keratitis (AK) is a chronic debilitating corneal infection principally affecting contact lens (CL) users. Studies were designed to test claims that the UK incidence may have increased in 2012-2014 and to evaluate potential causes.

METHODS

Annualised incidence data were collected from January 1984 to December 2016. Case-control study subjects were recruited between 14 April 2011 and 05 June 2017. Reusable CL users with AK were recruited retrospectively and prospectively. Controls were reusable CL users, recruited prospectively, with any disorder other than AK. Multivariable analysis of questionnaire data measured independent risk factors for AK.

RESULTS

The current outbreak of AK started in 2010-2011 with an incidence threefold higher than in 2004-2009. Risk factors for AK were: Oxipol disinfection, CLs made of group IV CL materials, poor CL hygiene, deficient hand hygiene, use of CLs while swimming or bathing, being white British, and for those in social classes 4-9.

CONCLUSION

AK is a largely preventable disease. The current outbreak is unlikely to be due to any one of the identified risk factors in isolation. Improving CL and hand hygiene, avoiding CLs contamination with water and use of effective CL disinfection solutions, or daily disposable CLs, will reduce the incidence of AK. In the longer-term, water avoidance publicity for CL users can be expected to reduce the incidence further. Ongoing surveillance of AK numbers will identify changes in incidence earlier. Evaluation of Acanthamoeba contamination in end-user drinking water would contribute to our understanding of regional variations in the risk of exposure.

Knowledge, Behavior, and Free-Living Amoebae Contamination of Cosmetic Contact Lens Among University Wearers in Thailand: A Cross-Sectional Study

OBJECTIVE

To assess the general knowledge, behavior, and presence of potentially pathogenic amoebae in cosmetic contact lens (CCL) wearers.

METHODS

One hundred CCL asymptomatic wearers were randomly selected. A questionnaire regarding their lens use, and a pair of their CCL was obtained. Identification of free-living amoeba (FLA) strains was based on morphological diagnosis, enflagellation tests (for non-Acanthamoeba strains), and sequencing of the small-subunit rRNA gene fragments.

RESULTS

Most (92%) of the participants surveyed were women, and the average age of the participants was 21.5±0.2 years. The CCL wearers generally showed a moderate (47%) or good (35%) level of knowledge, and good (51%) or excellent (40%) use of CCL. Two CCL samples were positive for Acanthamoeba genotype T3 or Vahlkampfia. The Acanthamoeba-contaminated CCL was from a wearer who used saline for treating lenses, and the Vahlkampfia-contaminated CCL was from a wearer who used CCL while swimming.

CONCLUSIONS

This is the first report of the presence of potentially pathogenic FLA in used CCL from asymptomatic wearers in Thailand. Although there was satisfactory knowledge and practice of lens care use, the public should be aware of CCL contaminated with potentially pathogenic FLA that can directly or indirectly cause keratitis.

Adhesion of Acanthamoeba on Silicone Hydrogel Contact Lenses

PURPOSE

To evaluate adhesion of Acanthamoeba trophozoites to different silicone hydrogel contact lens (SHCL) generations with and without multipurpose contact lens care solution (MPS) treatment.

METHODS

Acanthamoeba lugdunensis L3a trophozoites were inoculated onto discs trimmed from SHCLs: first generation, Air Optix (Lotrafilcon B) with a plasma surface treatment, second generation, Acuvue Oasys (Senofilcon A), which contains an internal wetting agent (Hydraclear), and third generation, Biofinity (Comfilcon A) with no surface treatment. After 18-hour inoculation, the number of adherent trophozoites on SHCLs was counted as the control under phase contrast microscopy. The effects of the 3 different MPSs, Opti-Free Express, ReNu Fresh, and Biotrue, soaking SHCLs for 6 hours, on Acanthamoeba adhesion were analyzed. Scanning electron microscopic examination was performed for assessment of Acanthamoeba attached on the lens surface.

RESULTS

Acanthamoeba trophozoites showed greater adhesion to Air Optix than to Acuvue Oasys and Biofinity (P < 0.05). On Air Optix and Acuvue Oasys, the number of adherent Acanthamoeba was significantly reduced compared with the control after treatment with Opti-Free Express (P < 0.05), but not significantly reduced by treatment with ReNu Fresh and Biotrue (P > 0.05). Acanthamoeba did not adhere to Biofinity regardless of MPSs treatment. Attachment of the acanthopodia of Acanthamoeba on the curved ridge of the Air Optix lens surface was observed.

CONCLUSIONS

Acanthamoeba showed greater affinity for the first-generation SHCL and seemed to be more attached on SHCLs with more ridges. MPS with myristamidopropyl dimethylamine reduced the adhesion rate.

In vitro adhesion of Acanthamoeba castellanii to soft contact lenses depends on water content and disinfection procedure

PURPOSE

To compare the potential of different soft contact lenses to be contaminated with Acanthamoeba castellanii as a function of material parameters and cleaning procedures.

METHODS

Different unworn soft hydrogel and silicone hydrogel contact lenses were incubated with human pathogenic A. castellanii. The adhesion of the acanthamoebae was investigated on the contact lenses and put into relation to their material parameters. The efficacy of a recommended contact lens cleaning procedure in reducing A. castellanii adhesion was investigated.

RESULTS

We found that material parameters such as elastic modulus, silicone content, ionic properties and swelling do not influence the adhesion of acanthamoebae to soft contact lenses. A material parameter that influenced adhesion significantly was the water content of the lens. With increasing water content, the adhesion of acanthamoebae increased. By following the cleaning instructions of the manufacturer the contamination of the lenses with A. castellanii could be reduced to a minimum, as shown both on contact lenses and in control experiments.

CONCLUSION

With this study we show that for the tested lenses, the adhesion of A. castellanii to contact lenses is independent of the silicone content of the lens, but depends nonlinearly on the water content of the lens. Furthermore, we demonstrate that applying proper lens cleaning procedures minimizes the risk of acanthamoebae adhesion to contact lenses.

Microbial adhesion to silicone hydrogel lenses: a review

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Salicylate inhibition of acanthamoebal attachment to contact lenses

PURPOSE

Sodium salicylate has shown potential as a component of contact lens care solutions designed to reduce Acanthamoebal attachment to contact lenses. This study determined the minimum effective concentration required to significantly reduce amoebal attachment.

METHODS

Different concentrations of sodium salicylate (10, 15, and 20 mM) were applied during exposure of unworn or bacterial biofilm-coated hydrogel contact lenses to Acanthamoeba castellanii trophozoites. Salicylate was applied at stage 1 intervention during biofilm formation on lenses, at stage 2 intervention during amoebal exposure, or at both stages.

RESULTS

A significant reduction in amoebal attachment was achieved when 10 mM salicylate was included during stage 1 alone; however, 15 mM was required for stage 2 intervention to significantly reduce attachment to clean or biofilm-coated lenses. For stages 1 and 2 combined intervention, 10 mM sodium salicylate produced a significant reduction in amoebal attachment.

CONCLUSIONS

In situ, within a contact lens case, biofilm formation and amoebal attachment would occur concurrently; therefore, stages 1 and 2 intervention would be closest to the real-life situation, thus indicating that 10 mM of salicylate would be an effective minimum concentration for reducing amoebal attachment to hydrogel contact lenses. Inclusion of components in contact lens care solution, such as sodium salicylate, which reduce Acanthamoebal attachment, has the potential to enhance effectiveness, particularly where amoebicidal efficacy may be limited, thus reducing the risk of contact lens-associated Acanthamoebal infection.

Clinical outcomes and prognostic factors associated with acanthamoeba keratitis

PURPOSE

To describe the clinical characteristics, time of presentation, risk factors, treatment, outcomes, and prognostic factors on a recent series of Acanthamoeba keratitis (AK) treated at our institution.

METHODS

Retrospective case series of 59 patients diagnosed with AK from January 1, 2004 to December 31, 2008. Of these 59 patients, 51 had complete follow-up data and were analyzed using univariate and multivariate logistic regression analyses performed with "failure" defined as requiring a penetrating keratoplasty (PKP) and/or having (1) best-corrected visual acuity (BCVA) < 20/100 or (2) BCVA < 20/25 at the last follow-up. A single multivariate model incorporating age, sex, steroid use before diagnosis, time to diagnosis, initial visual acuity (VA), stromal involvement, and diagnostic method was performed.

RESULTS

Symptom onset was greatest in the summer and lowest in the winter. With failure defined as requiring PKP and/or final BCVA < 20/100, univariate analysis suggests that age > 50 years, female sex, initial VA < 20/50, stromal involvement, and patients with a confirmed tissue diagnosis had a significant risk for failure; however, none of these variables were significant using multivariate analysis. Univariate analysis, with failure defined as requiring PKP and/or final BCVA < 20/25, showed stromal involvement and initial VA < 20/50 were significant for failure-only initial VA < 20/50 was significant using multivariate analysis.

CONCLUSIONS

Symptom onset for AK is greatest in the summer. Patients with confirmed tissue diagnosis and female patients may have a higher risk for failure, but a larger prospective population-based study is required to confirm this. Failure is likely associated with patients who present with stromal involvement and patients presenting with an initial BCVA worse than 20/50.

Temporal and seasonal trends in Acanthamoeba keratitis

PURPOSE

The purpose of this study was to assess the incidence and risk factors of Acanthamoeba keratitis (AK) over an 8-year period in a Canadian tertiary care setting.

METHODS

We retrospectively reviewed the medical records of 41 patients (42 eyes), who were diagnosed as having AK between January 1999 and December 2006 in the cornea clinic at the Toronto Western Hospital. The incidence and risk factors of AK were evaluated.

RESULTS

The number of cases per year increased from between 0 and 4 in the first 5 years to 9, 14, and 8 in the last 3 years. The annual increasing trend was statistically significant (P = 0.04). The month of onset of disease symptoms showed a trend toward onset in summer and fall and was statistically significant for the difference between January and August (P = 0.0094). The season of onset of disease symptoms showed a trend toward summer onset, and the difference between winter and summer was statistically significant (P = 0.02). 92.9% of cases occurred in contact lens wearers, particularly in soft contact lens wearers (82.1%).

CONCLUSIONS

The incidence of AK in Canada may be increasing since 2004. There is a seasonal trend toward disease onset in the warmer months.

On Acanthamoeba keratitis

Az Acanthamoeba-infekciók száma világszerte, így hazánkban is növekvő tendenciát mutat. A diagnosztikus és terápiás lehetőségek bővülése ellenére ez a betegség súlyosan károsíthatja a látást. A kórkép jellemzőit foglaljuk össze és mutatjuk be. A betegség elsősorban kontaktlencsét viselőkön alakul ki a nem megfelelő higiénia miatt. Szubjektív tünetei a fájdalom, vörös szem, könnyezés és szemhéjduzzanat. A klinikai képben jellegzetes a gyűrű alakú cornea stromájába terjedő infiltrátum. Differenciáldiagnosztikai szempontból a bakteriális, gombás és herpeses keratitistől kell elkülöníteni. Diagnózisában, a részletes anamnézis mellett, elsősorban konfokális corneamikroszkópia és speciális mikrobiológiai vizsgálatok javasoltak. A kórkép kezelésére többféle konzervatív és sebészi terápia létezik. Az eredményes gyógyuláshoz időben történő felismerés és hosszan tartó adekvát terápia szükséges. A legfontosabb azonban a megelőzés, amely az illesztők feladata, a páciensek felvilágosítása a megfelelő higiénés szabályok betartásáról, a korszerű lencsék és ápolószerek használatáról.

Contact lens solution efficacy against Acanthamoeba castellani

PURPOSE

Acanthamoeba castellani, ATCC 30234, cysts, and trophozoites after a 6-hour exposure.

METHODS

Trophozoite cultures were prepared at Bio-Concept Laboratories in vented tissue culture flasks containing peptone yeast glucose broth by incubation (35 degrees C +/- 1 degrees C for 11 days). Cyst suspensions were prepared by incubation of trophozoites in phosphate-buffered saline plus heat-killed yeast on Page's saline agar plates (35 degrees C +/- 1 degrees C for 14 days). The solutions were inoculated in triplicate in respective lens cases. After the 6-hour exposure, aliquots of challenged solutions were transferred to Dey-Engley neutralizing broth and further diluted in peptone yeast glucose broth in tissue culture plates to the -7 dilution. Flasks and plates were incubated for 14 days at 35 degrees C +/- 1 degrees C and were examined with an inverted light microscope at day 14 for the presence of viable trophozoites. The most probable number method was used for approximate enumeration of the number of survivors.

RESULTS

Mean log reductions for cysts were 1.8 for Clear Care/AOSEPT Plus, 2.0 for BLUE Vision/BLUE SEPT, 0.7 for Oxysept 1 Step, 0.5 for OPTI-FREE Express with Aldox, and 0.2 for easyvision one step+. Mean log reductions for trophozoites were 2.2 for Clear Care/AOSEPT Plus, 2.7 for BLUE Vision/BLUE SEPT, 2.5 for Oxysept 1 Step, 2.5 for OPTI-FREE Express with Aldox, and 1.8 for easyvision one step+.

CONCLUSIONS

Only Clear Care/AOSEPT Plus and BLUE Vision/BLUE SEPT showed high levels of antimicrobial activity against the cyst form of A. castellani. Oxysept 1 Step showed mild activity against the cysts and easyvision one step+ and OPTI-FREE Express with Aldox showed virtually no antiacanthamoeba activity against the cyst form after 6 hours of exposure.

The association of contact lens solution use and Acanthamoeba keratitis

PURPOSE

To investigate Acanthamoeba keratitis (AK) risk factors. Diagnosis of AK, a rare but serious corneal infection, has recently increased significantly at the University of Illinois at Chicago (UIC) Cornea Service.

DESIGN

Retrospective case-control study.

METHODS

settings: University, tertiary care hospital. patients: Fifty-five AK cases with contact lens use were diagnosed between May 1, 2003 and September 15, 2006. Clinic-matched controls with contact lens use were recruited. Subjects completed surveys targeting lens hygiene, contact lens solution use, and water exposure. main outcome measure: Acanthamoeba keratitis.

RESULTS

Thirty-nine (73.6%) cases and 113 (65.3%) controls participated; 38 cases had complete contact lens data. Thirty-five of 38 cases (92.1%) and 47 of 100 controls (47.0%) used soft lenses. Analysis was performed on 30 cases and 39 controls with matched pairs with soft lens use. Exclusive use of Advance Medical Optics (AMO) Complete MoisturePlus Multi-Purpose Solution was independently associated with AK in multivariable analysis (55.2% vs 10.5%; odds ratio [OR], 16.67; 95% confidence interval [CI] 2.11 to 162.63; P = .008). However, 38.8% of cases reported no use of AMO Complete MoisturePlus Multi-Purpose Solution either alone or in combination with other solutions. Although not statistically significant, additional hygiene-related variables (solution "reuse," lack of "rubbing," and showering with lenses) suggest a pattern of risk.

CONCLUSIONS

AMO Complete MoisturePlus Multi-Purpose Solution use is independently associated with AK among soft contact lens users. However, it does not explain all cases, suggesting additional factors. Further research into environmental risk factors and hygiene practices is warranted, especially considering this is the second outbreak of an atypical, contact lens-related infection.

Acanthamoeba Keratitis

PURPOSE

To report a recent significant increase of the number of patients diagnosed with Acanthamoeba keratitis (AK) at Wills Eye Hospital between 2004 and 2005. To determine the risk factors, clinical characteristics, treatments, and outcomes of patients with AK.

METHODS

Retrospective consecutive case series of 20 eyes with AK. The information included the incidence from 1995 to 2005, initial and final best-corrected visual acuity (BCVA) at 3-month follow-up, risk factors [contact lenses (CL) history, history of swimming with CL, and exposure to well water and/or contaminated water], clinical characteristics, methods of diagnosis, and treatments.

RESULTS

A statistically significant increased incidence of AK was seen in 2004 and 2005 compared with cases from 1995 to 2003 (P < 0.01). All patients wore CL; 19 of 20 wore frequent-replacement soft CL and used multipurpose disinfecting solutions. Other risk factors were exposure to well water in 40%, swimming with CL in 25%, and overnight wear in 25%. The diagnosis was made by histopathology in 50%, by microbiology in 15%, and by initial classic clinical signs and response to treatments in 35%. Herpes simplex virus was the misdiagnosis in 70%. Patients who presented with dendritiform keratitis or radial keratoneuritis had a BCVA better than 20/30 in 8 of 9 (89%) and patients with ring ulcers or stromal disease who had a BCVA less than finger counting in 5 of 8 (62.5%).

CONCLUSIONS

We observed an increased incidence of AK. Patients with proper use of frequent-replacement CL and multipurpose solutions can develop AK. Advanced stromal disease at diagnosis is associated with worse outcome.

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.

Diagnosis and management of Acanthamoeba keratitis

PURPOSE OF REVIEW

This paper reviews the literature generated on Acanthamoeba keratitis since 1998.

RECENT FINDINGS

Acanthamoeba infections may be on the rise. Contact lenses are the biggest risk factor for their development. Silicone hydrogel lenses are increasingly prescribed and may be 'more sticky' to Acanthamoeba organisms. Orthokeratology for the treatment of myopia has been associated with many new cases of Acanthamoeba keratitis. Daily disposable contact lenses are the safest form of soft contact lens. Patients continue to be misdiagnosed as having herpetic keratitis. Impression cytology and confocal microscopy are newer diagnostic modalities. Topical polyhexamethylene biguanide, chlorhexidine and propamidine are the mainstay of medical therapy. Amniotic membrane may be used for cases of persistent epithelial defect and to control inflammation. Penetrating keratoplasty in a medically treated eye affords a good chance of positive outcome.

SUMMARY

Acanthamoeba keratitis continues to be a difficult infection to diagnose and manage. The frequency of these infections may be on the rise, most commonly associated with frequent replacement soft contact lenses. The best chance for a good outcome is based on early diagnosis, so it is important for ophthalmologists consider it in patients, especially in the contact lens wearer with suspected herpes simplex keratitis.

Epidemiological characteristics of a Chicago-area Acanthamoeba keratitis outbreak

PURPOSE

To characterize Acanthamoeba keratitis (AK) cases and analyze the geographical distribution within the Chicago-Gary-Kenosha metropolitan area, Chicago, Illinois, USA.

DESIGN

Retrospective, population-based cohort study.

METHODS

All AK cases diagnosed at the University of Illinois at Chicago Cornea Service from June 1, 2003, to November 30, 2005, were included in analysis. Patients with keratitis were defined as cases through confocal microscopy, histology, and/or positive cultures. Exploratory analyses were performed to evaluate whether AK cases were unequally distributed geographically. County population data were extracted from US Census 2000 data, and rates were age-standardized to Cook County. Poisson regression analysis was used to estimate the age-standardized rate ratio (RR) between AK cases and county of residence. Current cases (June 1, 2003 to November 30, 2005) were compared with historical cases (June 1, 2000 to November 30, 2002) to determine if the current rate of AK diagnosis differed from historical rates.

RESULTS

Forty AK cases were diagnosed between June 1, 2003 and November 30, 2005. The average (+/-SD) age of patients with AK was 28.0 +/- 15.0 years (range, 13 to 70 years), 52.5% were men, and 95.0% wore contact lenses. Estimated RR measures demonstrated increased rates for all counties relative to Cook, and were significant for both DuPage County (RR 3.59; 95% confidence interval [95% CI] 1.44, 8.39) and Will County (RR 3.66; 95% CI 1.18 to 9.56). Current AK diagnosis rates were significantly higher than historical rates (RR 6.67; 95% CI 3.05 to 17.52).

CONCLUSIONS

AK cases are increasing in frequency. The increased rates are unevenly distributed in the study area. Further research is warranted to better understand the increase and unusual geographical distribution.