Differentiation of acanthamoeba keratitis from other non-acanthamoeba keratitis: Risk factors and clinical features.

INTRODUCTION: Infectious Keratitis is one of the most common ocular emergencies seen by ophthalmologists. Our aim is to identify the risk factors and clinical features of Acanthamoeba Keratitis (AK). METHODS: This retrospective chart review study was conducted at King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia, and included all the microbial keratitis cases, male and female patients of all ages. The main outcome is the differentiation between various microbial keratitis types. RESULTS: We included 134 consecutive eyes of 126 persons. We had 24 cases of acanthamoeba keratitis, 22 bacterial keratitis, 24 fungal keratitis, 32 herpetic keratitis, and 32 bacterial co-infection. Contact lens wear was found in 33 eyes (24.6%). Among acanthamoeba keratitis patients, 73% were ≤ 39 years of age, and 73% were females (P <0.001). Also, in AK cases, epithelial defect was found in all cases (100%), endothelial plaques were found in 18 eyes (69.2%), 12 cases had radial keratoneuritis (46.2%), and ring infiltrate was found in 53.8% of AK cases. CONCLUSIONS: We determined the factors that increase the risk of acanthamoeba infection and the clinical characteristics that help distinguish it from other types of microbial keratitis. Our findings suggest that younger females and patients who wear contact lenses are more likely to develop acanthamoeba keratitis. The occurrence of epitheliopathy, ring infiltrate, radial keratoneuritis, and endothelial plaques indicate the possibility of acanthamoeba infection. Promoting education on wearing contact lenses is essential to reduce the risk of acanthamoeba infection, as it is the most significant risk factor for this infection.

Incidence of Acanthamoeba Keratitis in the United Kingdom in 2015: A Prospective National Survey.

PURPOSE: The aims of this study were to quantify the incidence of Acanthamoeba keratitis (AK) in the United Kingdom and investigate risk factors and management parameters. METHODS: This was a prospective population-based study from January to December 2015 through the British Ophthalmic Surveillance Unit. Data were collected on demographics, clinical features, and management. Incidence rates were calculated from estimates of population and contact lens (CL) user numbers. Statistical analysis compared annualized incidences per million and altered risk ratios for AK with the England and Wales 24 months 1997/1998 to 1998/1999 study. RESULTS: The study identified 124 AK cases, an overall incidence of 2.35 per million. CL wearers accounted for 108 of 124 cases (87%), in whom the AK incidence was 26.94 per million. Herpes keratitis was initially misdiagnosed in 25 of 124 cases (20.2%). The highest incidence of AK was among planned replacement soft CL (PRSCL) wearers (50.65 per million), 7-fold greater than for daily disposable CL (DDSCL) users (7.24 per million). There was a significant increase in AK incidence ( P < 0.001) compared with both 1997/1998 [risk ratio 1.92, 95% confidence interval (CI) 1.38-2.66] and 1998/1999 (risk ratio 2.13, 95% CI 1.52-2.98) together with a higher incidence per million CL users of 26.94 versus 21.14 (1997/1998) and 17.53 (1998/1999). CONCLUSIONS: This study provides the first published data on the nationwide incidence of AK in the United Kingdom. The findings confirm an increasing incidence of AK, particularly among contact lens wearers since 1997/1998 to 1998/1999. PRSCLs were identified as a significant risk factor compared with DDSCLs. Misdiagnosis and treatment delays remain an ongoing problem for patients with AK.

A 5-Year Review of Coinfections in Acanthamoeba keratitis From South India.

PURPOSE: To ascertain the frequency of coinfections in Acanthamoeba keratitis, the nature of copathogens involved, and to analyze the implications in the context of current research on amoebic interactions. METHODS: A retrospective case review from a Tertiary Care Eye Hospital in South India. Smear and culture data for coinfections in Acanthamoeba corneal ulcers were collected from records over a 5-year period. The significance and relevance of our findings in the light of current research on Acanthamoeba interactions were analyzed. RESULTS: Eighty-five cases of culture-positive Acanthamoeba keratitis were identified over a 5-year period (43 of them being coinfections). Fusarium was most commonly identified species, followed by Aspergillus and the dematiaceous fungi. Pseudomonas spp was the commonest bacterial isolate. CONCLUSION: Coinfections with Acanthamoeba are common at our centre, and account for 50% of Acanthamoeba keratitis. The diverse nature of the organisms involved in coinfections suggest that such amoebic interactions with other organisms are probably more widespread than recognized. To the best of our knowledge, this is the first documentation from a long-term study of pathogen diversity in Acanthamoeba coinfections. It is possible that Acanthamoeba itself may be virulence enhanced and secondary to the co-organism, breaching the ocular surface defenses in an already compromised cornea. However, observations from the existing literature on Acanthamoeba interactions with bacteria and certain fungi are based mainly on nonocular or nonclinical isolates. It would be illuminating if such studies are performed on Acanthamoeba and coinfectors from corneal ulcers-to ascertain whether interactions are endosymbiotic or virulence enhanced through amoebic passage.

The global epidemiology and clinical diagnosis of Acanthamoeba keratitis.

Acanthamoeba keratitis is a rare parasitic infection of the cornea that can lead to permanent blindness if not diagnosed and treated promptly. We collected data on the incidences of Acanthamoeba keratitis from 20 countries and calculated an annual incidence of 23,561 cases, with the lowest rates in Tunisia and Belgium, and the highest in India. We analyzed 3755 Acanthamoeba sequences from the GenBank database across Asia, Europe, North America, South America, and Oceania and genotyped them into T1, T2, T3, T4, T5, T10, T11, T12, and T15. Many genotypes possess different characteristics, yet T4 is the most prevalent genotype. As efficient treatment against Acanthamoeba remains lacking, prevention from early diagnosis via staining, PCR, or in vivo confocal microscopy (IVCM) becomes significant for the condition's prognosis. IVCM is the most recommended approach for the early detection of Acanthamoeba. If IVCM is unavailable, PCR should be used as an alternative.

Acanthamoeba Keratitis Risk Factors for Daily Wear Contact Lens Users: A Case-Control Study.

PURPOSE: This study was designed to establish risk factors for the development of Acanthamoeba keratitis (AK) for daily disposable (DD) contact lens (CL) users compared with daily wear (DW) reusable lens users and for risks unique to DD users. This is important because, in many major economies, CL use is the principal cause of microbial keratitis, of which AK accounts for approximately 50% of cases with sight loss. Determining these AK risks informs practitioner advice and consumer behavior. DESIGN: Case-control study. PARTICIPANTS: Cases and controls were recruited from an Accident and Emergency Department serving South-East England. Cases were new CL users with AK recruited retrospectively from January 2011 to February 2013 and prospectively thereafter until August 2014. Controls were recruited prospectively from February 2014 to June 2015. METHODS: Analysis of a self-administered questionnaire. MAIN OUTCOME MEASURES: Independent risk factors and population attributable risk percentage (PAR%) for AK. RESULTS: A total of 83 AK cases and 122 controls were recruited; DD use was reported by 20 (24%) cases and 66 (54%) controls. In multivariable analyses adjusted for potential confounders, the odds of AK was higher for DW reusable soft lenses (odds ratio [OR], 3.84; 95% confidence interval [CI], 1.75-8.43) and rigid lenses (OR, 4.56; 95% CI, 1.03-20.19) than for DD lenses. Within the DD-using subset, AK was associated with the following modifiable risk factors: less frequent professional follow-up visits (OR, 10.12; 95% CI, 5.01-20.46); showering in lenses (OR, 3.29, 95% CI, 1.17-9.23); lens reuse (OR, 5.41; 95% CI, 1.55-18.89); and overnight wear (OR, 3.93; 95% CI, 1.15-13.46). The PAR% estimated that 30% to 62% of cases could be prevented by switching from reusable soft lens to DD lens use. CONCLUSIONS: Acanthamoeba keratitis risks are increased > threefold in DW reusable lens users versus DD lens use. Acanthamoeba keratitis risks for DD lens users can be minimized by adherence to safe use guidelines (no reuse, overnight wear, or contamination by water). Safe CL use can be improved by increasing the prominence of risk avoidance information from manufacturers and regulators. Because AK accounts for half of severe keratitis in CL users, these measures can be expected to have public health benefits.

Advances in the management of Acanthamoeba keratitis: A review of the literature and synthesized algorithmic approach.

Acanthamoeba keratitis (AK) is a severe cause of infectious keratitis and represents a significant clinical challenge. Recent literature regarding AK epidemiology, diagnosis, treatment modalities, and prognosis is reviewed and synthesized to propose an algorithmic protocol for AK management. Globally, AK outbreaks in developed countries are ongoing, and AK rates have increased. Moreover, current outbreaks may carry a worse prognosis than prior outbreaks. Despite identification of contact lens solutions implicated in AK outbreaks and the consequent market recall of these products, outbreaks persist. Acanthamoeba keratitis afflicts not only refractive soft contact lens users but also cosmetic contact lens users and gas permeable (especially orthokeratology) lens users. Innovations in in vivo confocal microscopy and PCR assays have increased the role for these adjuvant tests alongside corneal smear and culture in a multimodal diagnostic approach to suspected AK. Biguanides (such as chlorhexidine and polyhexamethylene biguanide) and diamidines (propamidine isethionate and hexamidine) remain cornerstones of AK management, and evidence for other treatment modalities continues to evolve. Voriconazole in topical and systemic forms may be useful as adjuvant therapy. The anti-leishmaniasis drug miltefosine, recently given orphan drug status by the United States Food and Drug Administration, has increasing evidence supporting a role in patients with severe/refractory disease. Prior topical corticosteroids have been consistently shown to be associated with worse outcomes in AK. Although not historically thought of as a treatment modality, benzalkonium chloride preservative may be leveraged for its anti-Acanthamoebal properties. The role of Rose-Bengal photodynamic antimicrobial therapy is evolving in selected cases of AK.

Report of rare genotypes of Acanthamoeba from soil source of the Payeh Maga Highland forest, North-eastern Sarawak, Malaysia.

Pathogenic Acanthamoeba species are the causative agents of Acanthamoeba keratitis and granulomatous amoebic encephalitis. Members of this amoeba genus are ubiquitous in the environments. In Malaysia, most environmental studies performed to date have targeted the detection and characterisation of Acanthamoeba sp. in different water sources, dust and soil samples collected near human habitats. However, no local study has yet to examine these amoebae in a forest, an isolated terrestrial environment, where human activity is relatively scarce. Further, there are also limited studies to investigate the same globally. The current study reported the isolation, morphological and genotypic characterisations of eleven Acanthamoeba sp. isolated from soils of the Payeh Maga Highland forest, Sarawak, Malaysia. Morphological analysis revealed that nine isolates belonged to Group II, whereas two isolates belonged to Group III as defined by the criteria of Pussard and Pons. The phylogenetic analysis based on complete 18S rRNA gene sequences showed that the isolates belonged to the rare T1 (six isolates), T6 (two isolates) and T13 (three isolates) genotypes. To the best of our knowledge, this is the first report about the detection of T6 Acanthamoeba sp. in this country. Overall, the current findings have enriched the knowledge pertaining to the occurrence, morphological and genotypic characteristics of Acanthamoeba sp. in an isolated terrestrial environment of Malaysia.

Genotype distribution of Acanthamoeba in keratitis: a systematic review.

Acanthamoeba spp. are among the most worldwide prevalent protozoa. It is the causative agent of a disease known as Acanthamoeba keratitis, a painful and severe sight-threatening corneal infection that can lead to blindness. In recent years, the prevalence of Acanthamoeba keratitis has rapidly increased, growing its importance to human health. This systematic review aims to assess the distribution of Acanthamoeba sp. genotypes causing keratitis around the world, considering the sample collected type and the used identification method. Most of the cases were found in Asia and Europe. Not surprisingly, the T4 genotype was the most prevalent worldwide, followed by T3, T15, T11, and T5. Furthermore, the T4 genotype contains a higher number of species. Given the differences in pathology, susceptibility to treatment, and clinical outcome between distinct genotypes, it is essential to genotype isolates from Acanthamoeba keratitis cases to help to establish a better correlation between in vitro and in vivo activities, resulting in better drug therapies and successful treatment in cases of this important ocular infection.

Incidence and Risk Factors of Ocular Hypertension and Glaucoma in Patients With Acanthamoeba Keratitis.

OBJECTIVES: To determine the incidence of ocular hypertension (OHT) and glaucoma in patients with acanthamoeba keratitis (AK) and to outline the risk factors for the development of glaucoma. METHODS: A retrospective review of patients diagnosed with AK at our institute during the period from 2000 to 2018. The main outcome measures were the incidence of OHT and glaucoma, and risk factors for the development of glaucoma. RESULTS: Fifty-two eyes diagnosed with AK were included. The incidence of OHT and glaucoma was 51.9% and 32.7%, respectively. The mean duration from disease onset to the first attack of elevated intraocular pressure was 8.4±16.6 months. The use of corticosteroids in the treatment regimen was significantly associated with the development of glaucoma (odds ratio, 3.93; 95% confidence interval, 0.96-16.15; P=0.049). At the last follow-up visit, both patients with glaucoma and nonglaucoma patients had improved visual acuity without a difference in the mean amount of logarithm of the minimum angle of resolution acuity improvement among them (0.56±0.91 vs. 0.67±0.87, P=0.686). CONCLUSION: Our findings confirm that OHT and glaucoma are frequent complications in AK. Patients treated with a regimen containing corticosteroids are at a higher risk; thus, they should receive close intraocular pressure monitoring.

American Academy of Optometry Microbial Keratitis Think Tank.

SIGNIFICANCE: Think Tank 2019 affirmed that the rate of infection associated with contact lenses has not changed in several decades. Also, there is a trend toward more serious infections associated with Acanthamoeba and fungi. The growing use of contact lenses in children demands our attention with surveillance and case-control studies. PURPOSE: The American Academy of Optometry (AAO) gathered researchers and key opinion leaders from around the world to discuss contact lens-associated microbial keratitis at the 2019 AAO Annual Meeting. METHODS: Experts presented within four sessions. Session 1 covered the epidemiology of microbial keratitis, pathogenesis of Pseudomonas aeruginosa, and the role of lens care systems and storage cases in corneal disease. Session 2 covered nonbacterial forms of keratitis in contact lens wearers. Session 3 covered future needs, challenges, and research questions in relation to microbial keratitis in youth and myopia control, microbiome, antimicrobial surfaces, and genetic susceptibility. Session 4 covered compliance and communication imperatives. RESULTS: The absolute rate of microbial keratitis has remained very consistent for three decades despite new technologies, and extended wear significantly increases the risk. Improved oxygen delivery afforded by silicone hydrogel lenses has not impacted the rates, and although the introduction of daily disposable lenses has minimized the risk of severe disease, there is no consistent evidence that they have altered the overall rate of microbial keratitis. Overnight orthokeratology lenses may increase the risk of microbial keratitis, especially secondary to Acanthamoeba, in children. Compliance remains a concern and a significant risk factor for disease. New insights into host microbiome and genetic susceptibility may uncover new theories. More studies such as case-control designs suited for rare diseases and registries are needed. CONCLUSIONS: The first annual AAO Think Tank acknowledged that the risk of microbial keratitis has not decreased over decades, despite innovation. Important questions and research directions remain.

Imagenología diferencial por microscopia confocal in vivo entre la epiteliopatía por acanthamoeba y la queratitis por herpes simple / In vivo confocal microscopy imaging for the differential diagnosis of Acanthamoeba epitheliopathy and herpes simplex keratitis

La queratitis por Acanthamoeba es una infección corneal de baja incidencia, condicionada por varios factores, pero con manifestación clínica variada y sintomatología típica. En su fase epitelial debe ser diferenciada de otras queratitis, específicamente de la queratitis por herpes simple, por la similitud entre ambas en cuanto a las características de la lesión corneal. La microscopia confocal in vivo constituye una alternativa diagnóstica. Es una biopsia fotográfica en cuyas imágenes podemos describir los quistes y trofozoítos de Acanthamoeba desde etapas iniciales, que nos ayudan a diferenciarla de otros tipos de queratitis e iniciar el tratamiento precoz. Se realizó una búsqueda de artículos publicados, con el objetivo de mostrar las imágenes por microscopia confocal de la fase epitelial de la infección corneal por Acanthamoeba y herpes simple. Se utilizó la plataforma Infomed, específicamente la Biblioteca Virtual de Salud(AU)

Acanthamoeba keratitis is a low-incidence corneal infection caused by several factors and characterized by a variety of clinical manifestations and typical symptoms. In its epithelial phase, it should be differentiated from other keratitis, particularly from herpes simplex keratitis, due to the similar characteristics of the corneal lesion. In vivo confocal microscopy is a diagnostic alternative consisting in a photographic biopsy showing images of Acanthamoeba cysts and trophozoites since their initial stages, thus allowing differentiation from other types of keratitis and the initiation of early treatment. A search was conducted of published papers with the purpose of showing confocal microscopy images of the epithelial phase of Acanthamoeba and herpes simplex corneal infection. Use was made of the platform Infomed, specifically the Virtual Health Library(AU)

Delayed diagnoses of Acanthamoeba keratitis at a tertiary care medical centre.

PURPOSE: To determine the prevalence and reasons for delays in diagnosis in patients with Acanthamoeba keratitis (AK) presenting to Wilmer Eye Institute, Baltimore, Maryland. METHODS: This retrospective study analysed all patients with culture-positive AK seen between 2012 and 2019 at a tertiary referral centre. Patient demographic information, clinical history, risk factors, symptom duration, referral patterns, slit lamp examination findings, visual acuity and need for surgery were collected. RESULTS: The study included 45 eyes of 43 patients. On average, patients were symptomatic for 52.6 days before culture collection. Thirty-one percent of patients were diagnosed within 28 days of symptom onset while 69% were diagnosed after 28 days. Before presentation to a tertiary care centre, 69% of patients were evaluated by an ophthalmologist outside of this institution and 27% were evaluated by a provider other than an ophthalmologist. AK was most commonly misdiagnosed as herpetic keratitis, occurring in 38% of patients. The strongest risk factor for AK was contact lens use. Only 11% of patients presented with the classic ring infiltrate and 82% had pain. Patients with an early versus late diagnosis had a mean Snellen visual acuity (VA) of 20/224 versus 20/296 at presentation (p = 0.33) and a mean Snellen VA of 20/91 versus 20/240 at final visit (p = 0.07). 11% of patients required a therapeutic penetrating keratoplasty. CONCLUSION: Delayed diagnosis of AK in our cohort occurred due to a misdiagnosis as herpetic keratitis, non-specific clinical signs including the lack of pain in a number of patients, and a delay in referral to a tertiary care centre. Any contact lens wearer with an atypical keratitis should be referred promptly for Acanthamoeba cultures.

Microbiological diagnosis of Acanthamoebic keratitis: experience from tertiary care center of North India.

Acanthamoeba keratitis (AK) is a painful vision-threatening infection caused by pathogenic free-living Acanthamoeba. Due to the non-specific clinical presentation, this condition tends to be misdiagnosed by clinicians. A timely diagnosis is crucial for favorable visual outcome. Three hundred patients with suspected microbial keratitis presenting to the Advanced Eye Center at our tertiary care center in North India during the period from 2014 to 2018 were included. Patient's corneal scrapings, contact lens, lens solution, lens case, and tears were processed for microscopic examination by Giemsa and Calcofluor staining, non-nutrient agar (NNA) culture and molecular diagnosis by conventional PCR (cPCR) and Real-time PCR (qPCR). 18S rDNA gene sequencing was done to assess phylogenetic relationship. AK was found in 3.6% (11/300) of non-bacterial non-fungal keratitis patients. Among microbiological techniques, microscopy for Acanthamoeba was positive in 7 cases, NNA culture was positive in 9 cases and 11 cases were detected both by cPCR and qPCR. The sensitivity of microscopy, culture, cPCR and qPCR was 63.64%, 81.82 %, 100%, and 100% respectively whereas specificity was 100% for all the tests. 18S rDNA sequencing revealed that A. castellanii was the predominant species and isolates were genetically distinct. AK should be considered in the differential diagnosis of infectious keratitis. Molecular tests are useful for rapid, sensitive and specific diagnosis and must be included in workup of keratitis.

Infectious keratitis: an update on epidemiology, causative microorganisms, risk factors, and antimicrobial resistance.

Corneal opacity is the 5th leading cause of blindness and visual impairment globally, affecting ~6 million of the world population. In addition, it is responsible for 1.5-2.0 million new cases of monocular blindness per year, highlighting an ongoing uncurbed burden on human health. Among all aetiologies such as infection, trauma, inflammation, degeneration and nutritional deficiency, infectious keratitis (IK) represents the leading cause of corneal blindness in both developed and developing countries, with an estimated incidence ranging from 2.5 to 799 per 100,000 population-year. IK can be caused by a wide range of microorganisms, including bacteria, fungi, virus, parasites and polymicrobial infection. Subject to the geographical and temporal variations, bacteria and fungi have been shown to be the most common causative microorganisms for corneal infection. Although viral and Acanthamoeba keratitis are less common, they represent important causes for corneal blindness in the developed countries. Contact lens wear, trauma, ocular surface diseases, lid diseases, and post-ocular surgery have been shown to be the major risk factors for IK. Broad-spectrum topical antimicrobial treatment is the current mainstay of treatment for IK, though its effectiveness is being challenged by the emergence of antimicrobial resistance, including multidrug resistance, in some parts of the world. In this review, we aim to provide an updated review on IK, encompassing the epidemiology, causative microorganisms, major risk factors and the impact of antimicrobial resistance.

Evaluation of Acanthamoeba keratitis cases in a tertiary medical care centre over 21 years.

To report on Acanthamoeba keratitis cases in a tertiary university eye-hospital in Graz, Austria, over a 21-year period. Retrospective study. Parameters included demographics, diagnostics, clinical courses, medical therapies, surgical interventions, secondary complications, and best spectacle-corrected visual acuity (BSCVA). Patient records for 44 eyes of 42 patients were analysed; 2 bilateral infections. Mean age at presentation was 31 ± 13 (16-65) years; contact lenses were used in 41 of 44 eyes (93.2%). Symptoms at initial presentation were mainly pain (41/43, 95.3%) and photophobia (16/43, 37.2%). Most frequent morphological findings were stromal infiltrates (30/44, 68.2%). Diagnosis was mainly confirmed by smears (40/42, 95.2%) and polymerase chain reaction (8/42, 19%). Antiamoebic treatment comprised biguanides and diamidines. Penetrating keratoplasty was performed in 10/44 (22.7%) eyes. Median time from symptom onset to initial visit was 2 (0-26) weeks; median follow-up was 30 (2-1008) weeks. BSCVA improved in 23/36 (63.9%) eyes, remained unchanged in 6/36 (16.7%) eyes and deteriorated in 7/36 (19.4%) eyes. Acanthamoeba keratitis predominantly occurs in young contact lens wearers. Diagnosis should be considered in patients with pain and stromal infiltrates. In the majority of cases, BSCVA can be improved. Early diagnosis and adequate treatment should be implemented to prevent complications.

Acanthamoeba Keratitis in Minors With Orthokeratology (OK) Lens Use: A Case Series.

OBJECTIVES: Myopia progression is a significant public health issue. Methods to halt myopia progression in minors continue to gain momentum. Orthokeratology, with market penetrance estimates approximating 1%, is a corneal reshaping therapy and potential myopia progression treatment. Our objective was to explore whether orthokeratology may increase the frequency of Acanthamoeba keratitis compared with other lens modalities. METHODS: Individuals less than 18 years diagnosed with Acanthamoeba keratitis (AK) at the University of Illinois at Chicago (UIC) Cornea Service between January 1st, 2003, and December 31st, 2016, were retrospectively reviewed. Subjects were grouped by lens modality (soft, rigid gas permeable [RGP], and orthokeratology), and all cases with orthokeratology lens use were reviewed. The primary outcome was a history of orthokeratology lens use in minors diagnosed with AK. RESULTS: Forty-seven contact lens users less than 18 years were diagnosed with AK. The mean age was 15.0 years (range 12-17), 26 (55%) were women, and 4 (8.5%) had bilateral disease. Lens modality included 6 (13%) with orthokeratology, 39 (83%) with soft contact lenses, 0 with nonorthokeratology RGP (0%), and 2 (4%) unknown. CONCLUSIONS: The proportion of orthokeratology cases among AK minors (13%) in our case series exceeds the expected proportion of orthokeratology cases expected based on orthokeratology market penetrance (1%). Results from this case series suggest a potential increased risk of AK in orthokeratology users compared with other lens modalities. In the context of the current myopia epidemic and concerns for halting myopia progression in minors, caution should be exercised when selecting appropriate treatment options to minimize the risk of AK.

Acanthamoeba keratitis: a review of biology, pathophysiology and epidemiology.

Acanthamoeba keratitis is an infection caused by a unicellular protozoan of the genus Acanthamoeba that is universally widespread. Until now, most cases were reported in contact lens wearers, although it is also a reality for non-wearers, mostly connected to corneal trauma. There is also a variation in incidence regarding the aetiology of the disease between developed and developing countries. PURPOSE: This work is based on a literature review, and the main goal is to deepen the knowledge about Acanthamoeba keratitis, presenting the main risk factors and focusing on prevention actions for this type of corneal infection since the treatments are not always effective. It targets specialists in visual health to strengthen their knowledge in this area, as well as to allow them to better inform their patients about hygiene care, appropriate measures of disinfection and ways to minimise the risk of infection. At this stage, it is important to highlight the essential role that practitioners play in fitting, monitoring and following-up patients to minimise the danger of infection. RECENT FINDINGS: It is well recognised that corneal trauma facilitates invasion by leaving an open door for microorganisms to penetrate the cornea. In addition to trauma, risk factors are mostly associated with patients' behaviours, such as interaction of contact lenses with contaminated water in the shower, swimming pools and beaches, etc., lack of hygiene habits with contact lenses and respective cases, and the use of ineffective disinfecting solutions. The fact that a disinfecting solution is not completely effective against trophozoites and/or cysts, both forms of Acanthamoeba's lifecycle, can cause the infection since one cyst alone leads to the emergence of a whole new population of Acanthamoeba. SUMMARY: It is necessary to reduce the risk of infection and, beyond the need to promote patient education to encourage correct CL hygiene behaviours, it should also be highlighted that there is an urgent need to enhance the efficacy of CL disinfection systems against all strains and both stages of Acanthamoeba through the creation of standardised methods. The ease of purchasing CLs without any supervision must also be considered a concern, and, in the near future, it is also important to develop and implement effective diagnostic methods and treatments for Acanthamoeba keratitis.

Acanthamoeba keratitis: A 4-year review from a tertiary care hospital in North India.

INTRODUCTION: Acanthamoeba keratitis (AK) is a blinding condition reported from both developed and developing countries. Limited knowledge on the clinical characteristics of AK and scarce laboratory diagnostic facilities in such countries poses difficulties in the accurate diagnosis. OBJECTIVE: To describe the epidemiological and clinical characteristics as well as management of Acanthamoeba keratitis in a tertiary care hospital in North India. METHODS: All clinically suspicious cases of Acanthamoeba keratitis (AK) presenting to our centre were screened for Acanthamoeba. All patients diagnosed as Acanthamoeba on microscopic examination, culture and polymerase chain reaction (PCR) were given Polyhexamethylene biguanide (PHMB) eye drops 0.02% half hourly for 1 week, then hourly for 1 week and then gradually tapered according to the response. Out of 300 consecutive patients evaluated, Acanthamoeba was detected in 11(3.6%) patients. A history of trauma was elicited in majority of the patients, 6 (55%). The most common complaints were eye pain, redness and watering in all of the patients, diminution of vision (8, 72.7%), photophobia (7, 63.6%) and foreign body sensation (2, 18.2%). Complete healing with vascularization and scarring was observed in 7 patients (63.6%) patients whereas progression to perforation of corneal ulcer and corneal melt was seen in 3 (27.3%) cases and these patients underwent therapeutic keratoplasty later. One patient did not come for follow up examination. CONCLUSION: The most common risk factor for the occurrence of Acanthamoeba Keratitis is trauma followed by contact lens use.

The relationship between environmental sources and the susceptibility of Acanthamoeba keratitis in the United Kingdom.

PURPOSE: To determine whether Acanthamoeba keratitis (AK) patients have higher rates of Acanthamoeba and free-living amoeba (FLA) colonising domestic sinks than control contact lens (CL) wearers, and whether these isolates are genetically similar to the corneal isolates from their CL associated AK. METHODS: 129 AK patients from Moorefield Eye Hospital, London and 64 control CL wearers from the Institute of Optometry were included in this study. The participants self-collected home kitchen and bathroom samples from tap-spouts, overflows and drains using an instructional kit. The samples were cultured by inoculating onto a non-nutrient agar plate seeded with Escherichia coli, incubated at 32°C and examined for amoebae by microscopy for up to 2 weeks. Partial sequences of mitochondrial cytochrome oxidase genes (coxA) of Acanthamoeba isolates from four AK patients were compared to Acanthamoeba isolated from the patient's home. The association between sampling sites was analysed with the chi-square test. RESULTS: A total of 513 samples from AK patients and 189 from CL controls were collected. The yield of FLA was significantly greater in patients' bathrooms (72.1%) than CL controls' bathrooms (53.4%) (p<0.05). Spouts (kitchen 6.7%, bathroom 11%) had the lowest rate of Acanthamoeba isolation compared to drains (kitchen 18.2%, bathroom 27.9%) and overflow (kitchen 39.1%, bathroom 25.9%) either in kitchens or bathrooms (p<0.05). There was no statistically significant difference between the average prevalence of Acanthamoeba in all three sample sites in kitchens (16.9%) compared to all three sample sites in bathrooms (21.5%) and no association for Acanthamoeba prevalence between AK patients and CL controls. All four corneal isolates had the same coxA sequence as at least one domestic water isolate from the patients' sink of the kitchen and the bathroom. CONCLUSION: The prevalence of Acanthamoeba and FLA was high in UK homes. FLA colonisation was higher in AK patients compared to controls but the prevalence of Acanthamoeba between AK patients and CL controls domestic sinks was similar. This study confirms that domestic water isolates are probably the source of AK infection. Advice about avoiding water contact when using CL's should be mandatory.