The association of contact lens solution use and Acanthamoeba keratitis

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.

Corneal Transplantation for Infectious Keratitis: A Prospective Dutch Registry Study

PURPOSE

The aim of this study was to analyze real-world practice patterns and graft survival after corneal transplantation for infectious keratitis in the Netherlands.

METHODS

All consecutive keratoplasties for infectious keratitis registered in the Netherlands Organ Transplant Registry were included. Graft survival was analyzed using Kaplan-Meier survival curves with Cox regression to compare the 3 most common pathogens with subgroup analysis for type and reason of transplantation, sex, and graft size. Multivariable analysis was performed using the same explanatory factors.

RESULTS

Between 2007 and 2017, 1111 keratoplasties for infectious keratitis were registered in the Netherlands Organ Transplant Registry. The most common pathogens were viruses (n = 437), bacteria (n = 271), and Acanthamoeba (n = 121). Human leukocyte antigen (HLA) matching did not provide a significant survival benefit, whereas emergency procedures showed worse graft survival [hazard ratio (HR) = 0.40, P = 0.120; HR = 2.73, P < 0.001, respectively]. Graft size >8.5 mm was significantly worse than graft size 8.5 mm (HR = 2.062, P = 0.010). In therapeutic keratoplasty, graft survival was significantly worse for Acanthamoeba than viral keratitis (HR = 2.36, P = 0.008). In the multivariable model, adjusting for graft size, type, and reason for transplantation, viral and bacterial keratitis did not differ significantly in graft survival, and Acanthamoeba showed a significantly worse prognosis (vs. viral keratitis, HR = 2.30, P < 0.001; bacterial keratitis, HR = 2.65, P < 0.001).

CONCLUSIONS

Viral keratitis was the most common indication for transplantation, followed by bacterial and Acanthamoeba keratitis. HLA matching did not offer protection over elective non-HLA-matched procedures, whereas emergency procedures and grafts sized >8.5 mm showed poor survival. In optical keratoplasty, survival is high for all pathogens, whereas in therapeutic keratoplasty Acanthamoeba shows poor outcome.

TFOS Lifestyle: Impact of contact lenses on the ocular surface

Several lifestyle choices made by contact lens wearers can have adverse consequences on ocular health. These include being non-adherent to contact lens care, sleeping in lenses, ill-advised purchasing options, not seeing an eyecare professional for regular aftercare visits, wearing lenses when feeling unwell, wearing lenses too soon after various forms of ophthalmic surgery, and wearing lenses when engaged in risky behaviors (e.g., when using tobacco, alcohol or recreational drugs). Those with a pre-existing compromised ocular surface may find that contact lens wear exacerbates ocular disease morbidity. Conversely, contact lenses may have various therapeutic benefits. The coronavirus disease-2019 (COVID-19) pandemic impinged upon the lifestyle of contact lens wearers, introducing challenges such as mask-associated dry eye, contact lens discomfort with increased use of digital devices, inadvertent exposure to hand sanitizers, and reduced use of lenses. Wearing contact lenses in challenging environments, such as in the presence of dust and noxious chemicals, or where there is the possibility of ocular trauma (e.g., sport or working with tools) can be problematic, although in some instances lenses can be protective. Contact lenses can be worn for sport, theatre, at high altitude, driving at night, in the military and in space, and special considerations are required when prescribing in such situations to ensure successful outcomes. A systematic review and meta-analysis, incorporated within the review, identified that the influence of lifestyle factors on soft contact lens dropout remains poorly understood, and is an area in need of further research. Overall, this report investigated lifestyle-related choices made by clinicians and contact lens wearers and discovered that when appropriate lifestyle choices are made, contact lens wear can enhance the quality of life of wearers.

In vitro Evaluation the Efficacy of Some Nnew Plant Extracts and Biocides on the Viability of Acanthamoeba castellanii

The purpose of this study was to assess the efficacy of certain plant extracts and to compare them with current biocides on the viability of Acanthamoeba castellanii cysts and trophozoites in vitro. Amoebicidal and cysticidal assays were performed against both trophozoites and cysts of Acanthamoeba castellanii (ATCC 50370). Ten plant extracts were evaluated alongside the current agents included polyhexamethylene biguanide (PHMB), octenidine and chlorhexidine digluconate. A. castellanii (ATCC 50370) was treated to serial two-fold dilutions of the test compounds and extracts in microtitre plate wells to investigate the effect on trophozoites and cysts of A. castellanii (ATCC 50370). Furthermore, the toxicity of each of the test compounds and extracts were assessed towards a mammalian cell line. Minimum trophozoite inhibitory concentration (MTIC), minimum trophozoite amoebicidal concentration (MTAC), and minimum cysticidal concentration (MCC) were used to establish A. castellanii (ATCC 50370) in vitro sensitivity. The findings of this research revealed that the biguanides PHMB, chlorhexidine, and octenidine all had excellent effectiveness against trophozoites and cysts of A. castellanii (ATCC 50370). The plant extracts testing results showed that, great activity against trophozoites and cysts ofA. castellanii (ATCC 50370) at lower concentrations. This is the first study to demonstrate that the Proskia plant extract had the lowest MCC value, which was 3.9 µg/mL. The time kill experiment confirmed this finding, as this extract reduced cysts of A. castellanii (ATCC 50370) by more than 3-log at 6 hour and by 4-log after 24 hour. The anti-amoebic efficacy of new plant extracts on the viability of A. castellanii (ATCC 50370) cysts and trophozoites was comparable to existing biocide treatments and was not toxic when tested on a mammalian cell line. This could be a promising novel Acanthamoeba treatment by using the tested plant extracts as a monotherapy against trophozoites and cysts.

The epidemiology of infectious keratitis

Infectious keratitis is a rare but potentially severe sight-threatening disease, associated with considerable societal burden, cost and morbidity. This review summarises the most recent evidence for the incidence, risk factors and impact of disease, all of which vary widely according to region, access to health care, socioeconomic and environmental factors, predisposing conditions and causative organisms. The frequency and societal impact of infectious keratitis are significantly higher in low-income countries. In non-viral infectious keratitis, bacterial causes predominate in most regions. Fungi, particularly linked with agricultural trauma, are more frequently associated with infectious keratitis in low-income regions, particularly in India and certain African countries. The disease impact is compounded by poverty and limited access to services and treatment. Early diagnosis, access to appropriate treatment, prophylaxis in ocular trauma, availability of eye protection, awareness of risk factors may be associated with reduced disease severity and vision loss. Evidence for the incidence and burden of disease is lacking in certain regions and well-designed epidemiological studies to identify independent risk factors for the disease and those associated with more severe outcomes may better identify causation and guide resource allocation and preventative strategies.

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.

The Anti-Amoebic Activity of a Peptidomimetic against Acanthamoeba castellanii

Acanthamoeba is a free-living protozoan known to cause keratitis most commonly, especially among contact lens wearers. Treatment of Acanthamoeba keratitis is challenging as Acanthamoeba can encyst from the active form, a trophozoite, into a hibernating cyst that is refractory to antibiotics and difficult to kill; therefore, there is a need for more effective anti-amoebic strategies. In this study, we have evaluated the anti-amoebic activity of the antimicrobial peptide mimic RK-758 against Acanthamoeba castellanii. RK-758 peptidomimetic was subjected to biological assays to investigate its amoebicidal, amoebistatic, anti-encystation, and anti-excystation effects on A. castellanii. The anti-amoebic activity of the peptide mimic RK-758 was compared with chlorhexidine against the Acanthamoeba castellanii ATCC30868 and Acanthamoeba castellanii 044 (a clinical strain) with the concentrations of both ranging from 125 µM down to 7.81 µM. All experiments were performed in duplicate with three independent replicates. The data were represented as mean ± SE and analysed using a two-sample t-test and two-tailed distributions. A p < 0.05 was considered statistically significant. The peptidomimetic RK-758 had anti-Acanthamoeba activity against both trophozoites and cysts in a dose-dependent manner. The RK-758 had amoebicidal and growth inhibitory activities of ≥50% at a concentration between 125 µM and 15.6 µM against the trophozoites of both Acanthamoeba strains. Inhibitory effects on the cyst formation and trophozoite re-emergence from cysts were noted at similar concentrations. Chlorhexidine had 50% activity at 7.81 µM and above against the trophozoites and cysts of both strains. In the haemolysis assay, the RK-758 lysed horse RBCs at concentrations greater than 50 µM whereas lysis occurred at concentrations greater than 125 µM for the chlorhexidine. The peptidomimetic RK-758, therefore, has activity against both the trophozoite and cyst forms of Acanthamoeba and has the potential to be further developed as an anti-microbial agent against Acanthamoeba. RK-758 may also have use as an anti-amoebic disinfectant in contact lens solutions.

A Review of Contact Lens-Related Risk Factors and Complications

The purpose of this article is to develop a modern strategy for handling difficulties related to contact lenses and their care. A growing number of people throughout the world are currently concerned by eye-related undesirable activities in allergy sufferers and those wearing contact lenses. While many wearers who experience ocular discomfort exhibit dryness as a symptom, many other contact lens-related pain symptoms also include irritation and fatigue, and managing coexisting diseases must be done in accordance with aspects of wearing contact lenses, all of which undoubtedly increase discomfort.

It is typical for contact lens storage containers to have persistent microbial contamination, which has been linked to microbial keratitis (MK) and clear corneal invasion. Contact lens-associated MK is an interesting, potentially sight-threatening complexity arising from wearing soft contact lenses. Estimates show that for every 10,000 persons who wear contact lenses each year, there are 2 to 5 occurrences of MK. Investigating separate determinants for contact lens-associated MK and evaluating their impact on infection load is one of the challenges in their administration. It is hoped that this will offer a useful outline of the complicated issues of contact lens wear that are both infectious and non-infectious. Recent epidemiological studies detailing the risk factors associated with contact lens use, and the effect of pathogen and individual immune profiles on the severity of diseases have enlightened how we might interpret the prophylaxis and prevention of contact lens-related corneal infection. The most dreaded side effect of contact lens use, infectious keratitis linked with contact lenses, will be reviewed, along with the most recent advancements in its diagnosis and treatment.

Potential role of Acanthamoeba Rab7

Acanthamoeba castellanii is a free-living protozoan that causes several severe human parasitic diseases such as Acanthamoeba keratitis and granulomatous encephalitis. A. castellanii feeds on bacteria, yeasts, and other organic particles as food sources, but the mechanisms of digestion in acanthamoebal cells are unclear. Rab GTPases participate in endosomal delivery in eukaryotes after phagocytosis. This study aimed to determine the potential functions of A. castellanii Rab7 (AcRab7), which is involved in phagocytosis, and the relationship between AcRab7 and further cellular physiological phenomena. In this study, the inhibitor CID1067700 (CID) was used to specifically inhibit the binding of nucleotides to confirm the potential functions of AcRab7. Cellular proliferation and ATP assays were also used to detect underlying cellular physiological functions after blocking the phagocytosis pathway. We found that AcRab7 expression increased as the co-culture time with Escherichia coli increased. Immunofluorescence staining showed that AcRab7 colocalized with lysosomes in its GTP-activating form. In addition, AcRab7 inhibition resulted in a reduction in cell proliferation and ATP levels. Our results suggest that AcRab7 participates in endosomal delivery and dominates energy production and cell growth.

Change in Risk Score and Behaviors of Soft Contact Lens Wearers After Targeted Patient Education

OBJECTIVES

To determine if targeted education can influence the behaviors and scores of soft contact lens (SCL) wearers via the Contact Lens Risk Survey (CLRS).

METHODS

This was a multicenter, prospective, case-control study. Cases were symptomatic red eye SCL wearers (age, 18-39 years), and controls were age , sex, and site matched. Participants completed the CLRS and were provided targeted patient education at three time points: baseline, one, and six months. Change in scores and behaviors were analyzed using the Wilcoxon signed rank test.

RESULTS

Forty-one cases and 71 controls were analyzed. The mean risk score (mean±SE) from baseline to follow-up improved (reduced) for all participants (-1.96±0.73; P=0.01), mostly driven by the improvement among cases (-2.55±1.32; P=0.05). Case subjects reported a decrease in frequency of wearing lenses while showering (-0.32±0.07; P<0.0001), discarding lens solution (-0.13±0.06; P=0.03), and rinsing lenses with tap water (-0.19±0.08; P=0.02) after targeted education.

CONCLUSIONS

Targeted patient education can influence some behaviors of SCL wearers, especially those who experienced a red eye event. Further study is needed to determine how to improve other risk behaviors and whether these changes are sustained long term.

Amoebicidal Activity of Poly-Epsilon-Lysine Functionalized Hydrogels

Purpose

To determine the amoebicidal activity of functionalized poly-epsilon-lysine hydrogels (pɛK⁺) against Acanthamoeba castellanii.

Methods

A. castellanii trophozoites and cysts were grown in the presence of pɛK solution (0–2.17 mM), pɛK or pɛK⁺ hydrogels, or commercial hydrogel contact lens (CL) for 24 hours or 7 days in PBS or Peptone-Yeast-Glucose (PYG) media (nutrient-deplete or nutrient-replete cultures, respectively). Toxicity was determined using propidium iodide and imaged using fluorescence microscopy. Ex vivo porcine corneas were inoculated with A. castellanii trophozoites ± pɛK, pɛK⁺ hydrogels or commercial hydrogel CL for 7 days. Corneal infection was assessed by periodic acid–Schiff staining and histologic analysis. Regrowth of A. castellanii from hydrogel lenses and corneal discs at 7 days was assessed using microscopy and enumeration.

Results

The toxicity of pɛK⁺ hydrogels resulted in the death of 98.52% or 83.31% of the trophozoites at 24 hours or 7 days, respectively. The toxicity of pɛK⁺ hydrogels resulted in the death of 70.59% or 82.32% of the cysts in PBS at 24 hours or 7 days, respectively. Cysts exposed to pɛK⁺ hydrogels in PYG medium resulted in 75.37% and 87.14% death at 24 hours and 7 days. Ex vivo corneas infected with trophozoites and incubated with pɛK⁺ hydrogels showed the absence of A. castellanii in the stroma, with no regrowth from corneas or pɛK⁺ hydrogel, compared with infected-only corneas and those incubated in presence of commercial hydrogel CL.

Conclusions

pɛK⁺ hydrogels demonstrated pronounced amoebicidal and cysticidal activity against A. castellanii. pɛK⁺ hydrogels have the potential for use as CLs that could minimize the risk of CL-associated Acanthamoeba keratitis.

Addressing common myths and misconceptions in soft contact lens practice

Advances in contact lens technology over the past 50 years since the commercialisation of the first soft lenses in 1971 have been incredible, with significant changes in contact lens materials, frequency of replacement, care systems and lens designs occurring. However, despite the widespread availability of contact lenses, penetration rates for those who need vision correction remain in the low single digits and many practitioners seem to hold on to concepts around the potential value of contact lenses that appear based in the dim and distant past and are certainly no longer valid today. This review addresses 10 common 'myths and misconceptions' around soft contact lenses using an evidence-based approach that can hopefully dispel some of these incorrect assumptions.

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.

Acanthamoeba keratitis in contact lens wearers in a tertiary center of Tunisia, North Africa

PURPOSE

To analyze the epidemiological and clinical features of Acanathamoeba keratitis AK and to assess the risk factors of this corneal infection in contact lens CL wearers in a tertiary center of Tunisia, North Africa.

METHODS

We carried out a retrospective study between January 2008 and December 2019 in the ophthtalmology department of a referral center, Sousse, Tunisia. A review of the chart of 248 patients using CL and diagnosed with presumed infectious keratitis was done.Socio demographic, risk behaviors and microbiological findings in case of AK were analyzed. The mean follow-up was 18 months (1 month-4 years).

RESULTS

AK was diagnosed in 29 cases (11.7% of contact lens wearers with infectious keratitis). These 29 cases were analyzed. The mean age at the time of diagnosis was 33, 44 ± 26, 9 years. Almost of the patients (13; 44.82%) used soft monthly disposable contact lenses. Some risk behaviors related to contact lens wearing were found in our study like not washing and drying hands before CL wear, sleeping in CL, topping off, not respecting the adequate replacement frequency and showering or swimming in CL.After treatment, visual acuity improved only in 10 cases (34.48%), remained the same in 11 cases (37.93%) and worsened in 8 cases (27.58%).

CONCLUSION

Clinicians must suspect AK in each CL wearer with suggestive clinical signs to allow earlier treatment and better prognosis. Public prevention messages that encourage CL wearers to respect the hygiene rules should be broadly applicable to each person using any type of CL, to minimize the risk of AK.

Contact Lens- and Patient-related Factors Associated with Contact Lens Discomfort among Contact Lens Wearers in an African Cohort

SIGNIFICANCE

No information is available on contact lens discomfort in any African population. Such information may be helpful in developing the scope and priorities for intervention.

PURPOSE

The purpose of the study was to examine contact lens- and patient-related factors associated with contact lens discomfort among wearers in Ghana.

METHODS

In this multicenter cross-sectional study, contact lens wearers 18 years and older were recruited. The Contact Lens Dry Eye Questionnaire-8 and a standardized scripted interview were administered to 72 contact lens wearers at five clinical sites, and 40 participants' lens storage cases were collected and cultured. A variety of patient- and contact lens-related factors were examined. Univariate and multivariate logistic regression modeling were used to assess risk factors associated with contact lens discomfort.

RESULTS

Seventy-two contact lens wearers aged 18 to 45 years completed the study. The mean age was 27.5 ± 6.4 years, 65.3% of them were females, 86.1% wore soft contact lens, and 13.9% wore rigid gas-permeable lens. Contact lens discomfort was reported by 66.7% of the subjects. Most frequent lens storage cases isolates were Bacillus species (40%) and fungi (31.1%). Significant association was found between disinfecting with tap water (5.98; 95% confidence interval [CI], 1.22 to 29.27; P = .03), heavy visual display terminal use (3.39; 95% CI, 1.01 to 11.34; P = .05), high water content (1.16; 95% CI, 1.02 to 1.33; P = .03), and contact lens discomfort. Demographic factors, wear modality, and care solutions were not significant (all P > .05).

CONCLUSIONS

In considering the use of contact lenses for refractive correction in this population, strategies for preventing contact lens discomfort that should be targeted include use of low-water-content lenses, disinfecting with multipurpose solutions, and reducing the time spent daily on visual display terminal use.

Effect of Water Exposure on Contact Lens Storage Case Contamination in Soft Lens Wearers

SIGNIFICANCE

Water exposure during contact lens wear can transfer pathogenic microorganisms to the eye, causing ocular complications. This study determined that water exposure is prevalent among lens wearers and is independently associated with higher case contamination. Contact lens compliance education to minimize water exposure should be reenforced by contact lens organizations and practitioners.

PURPOSE

Given the increasing association between water exposure and contact lens disease, this study aimed to explore the effect of water exposure and storage case contamination in soft contact lens users.

METHODS

A total of 165 daily soft lens wearers completed a self-administered questionnaire on contact lens hygiene. Lens cases were collected, and microbial analysis was conducted using an adenosine triphosphate assay (for overall microbial bioburden) and limulus amebocyte lysate assay (for endotoxin levels). The lens hygiene (excellent, >35; moderate, 28 to 35; poor, <28) and water contact (≤1, good; >1, poor) scores measured the compliance and water exposure during lens wear, respectively. Multiple regression determined the association between water behaviors and case contamination.

RESULTS

The average (standard deviation) age of participants was 28 (13.5) years (18 to 78 years), and 65% were female. The average overall microbial bioburden of storage cases was 3.10 (0.98) log colony-forming unit/mL (1.09 to 5.94 log colony-forming unit/mL). Forty-five percent of participants reported showering, 49.7% reported swimming while wearing lenses (65.4% of whom swam without goggles), 27.8% used wet hands to handle lenses, and 17.5% used tap water to rinse storage cases. Showering with lenses significantly increased the risk of higher storage case bioburden (P = .001), whereas using wet hands (P = .01) doubled the risk of higher case endotoxin levels (odds ratio, 2.41; confidence interval 1.19 to 4.86).

CONCLUSIONS

Water contact behavior while wearing lenses is prevalent among soft lens wearers and is associated with higher case contamination. Practitioners may improve contact lens education to reduce water exposure and case contamination to reduce the risk of lens-related adverse events.

Regular soft contact lens wearers' comprehension of graphical symbols labelled on multipurpose solutions

CLINICAL RELEVANCE

Symbols are commonly used to represent information of health care products included multipurpose solutions (MPSs) for contact lens (CL) care.

BACKGROUND

Little knowledge is available about recognition and comprehension by regular soft CL wearers of commonly used symbols in the instructions of CL MPSs marketed worldwide.

METHODS

CL wearers from the UK and Spain were invited to answer an anonymous on-line questionnaire (distributed though Facebook and Twitter) concerning the recognition and comprehension of seven common symbols (ISO 15223:2017 and EN 980:2008) included in MPS package instructions.

RESULTS

Answers of one hundred-ten soft CL wearers who use MPS (27 in the UK and 83 in Spain) were analysed showing low recognition and comprehension of the surveyed symbols even in wearers with > 5 years of CL wear (71.8%). The CE marked was the most recognised (96% in the UK and 88% in Spain, P = 0.29) and understood (78% in the UK and 85% in Spain, P = 0.25) symbol, but other important symbols, such as 'Caution' and 'Do not reuse', were under recognised (22% in the UK and 19% in Spain, P = 0.78 and 11% in the UK and 6% in Spain, P = 0.40 respectively) and understood (close to 30% in both countries P > 0.15). Participants with > 5 years of experience, showed slightly higher comprehension (P < 0.05) in some symbols ('Sterilised'; 'Do not reuse'; 'Use by date' and 'CE marked').

CONCLUSION

These results suggest an insufficient comprehension of seven common symbols included in MPS instructions among regular CL wearers in the UK and Spain without high impact of CL wear experience. Improving the education and symbol comprehension of regular CL wearers could help to get better patients' behaviour and safe use of MPS in soft CLs care.

The Risks and Benefits of Myopia Control

PURPOSE

The prevalence of myopia is increasing around the world, stimulating interest in methods to slow its progression. The primary justification for slowing myopia progression is to reduce the risk of vision loss through sight-threatening ocular pathologic features in later life. The article analyzes whether the potential benefits of slowing myopia progression by 1 diopter (D) justify the potential risks associated with treatments.

METHODS

First, the known risks associated with various methods of myopia control are summarized, with emphasis on contact lens wear. Based on available data, the risk of visual impairment and predicted years of visual impairment are estimated for a range of incidence levels. Next, the increased risk of potentially sight-threatening conditions associated with different levels of myopia are reviewed. Finally, a model of the risk of visual impairment as a function of myopia level is developed, and the years of visual impairment associated with various levels of myopia and the years of visual impairment that could be prevented with achievable levels of myopia control are estimated.

RESULTS

Assuming an incidence of microbial keratitis between 1 and 25 per 10 000 patient-years and that 15% of cases result in vision loss leads to the conclusion that between 38 and 945 patients need to be exposed to 5 years of wear to produce 5 years of vision loss. Each additional 1 D of myopia is associated with a 58%, 20%, 21%, and 30% increase in the risk of myopic maculopathy, open-angle glaucoma, posterior subcapsular cataract, and retinal detachment, respectively. The predicted mean years of visual impairment ranges from 4.42 in a person with myopia of -3 D to 9.56 in a person with myopia of -8 D, and a 1-D reduction would lower these by 0.74 and 1.21 years, respectively.

CONCLUSIONS

The potential benefits of myopia control outweigh the risks: the number needed to treat to prevent 5 years of visual impairment is between 4.1 and 6.8, whereas fewer than 1 in 38 will experience a loss of vision as a result of myopia control.

Uptake and Release of a Multipurpose Solution Biocide (MAP-D) From Hydrogel and Silicone Hydrogel Contact Lenses Using a Radiolabel Methodology

PURPOSE

The purpose of this study was to evaluate the uptake and release of radiolabelled myristamidopropyl dimethylamine (MAP-D) on reusable daily wear contact lenses (CLs) over 7 days.

METHODS

Three silicone hydrogel (SH) CL materials (lotrafilcon B, balafilcon A, senofilcon A) and two conventional hydrogel (CH) materials (etafilcon A, omafilcon A) were tested. A short-term (experiment 1, N=4) and a longer-term (experiment 2, N=3) study was conducted. In experiment 1, the CLs were incubated in 2 mL of phosphate buffered solution (PBS) containing 14C MAP-D (5 μg/mL) for 8 hrs. The release of 14C MAP-D was measured at t=0.25, 0.5, 1, 2, 4, 8, and 24 hr in PBS. In experiment 2, the CLs were incubated in the 14C MAP-D solution for 8 hrs followed by a 16-hr release in PBS. This cycle was repeated daily for 7 days. At the end of both experiments, lenses were extracted to determine the total uptake of MAP-D. The radioactivity was measured using a beta scintillation counter.

RESULTS

In experiment 1, all three SH lenses sorbed similar amounts of MAP-D (P=0.99), all of which were higher than the two CH materials (P<0.01). However, the CH materials released a greater amount of MAP-D than the SH materials (P<0.01). In experiment 2, the uptake of MAP-D in SH materials increased over 7 days, whereas the amount of MAP-D remained constant in the CH materials (P=0.99). Similar to experiment 1, the CH lenses released more MAP-D than SH lenses after 7 days (P<0.01).

CONCLUSION

The SH materials absorbed greater amounts of MAP-D compared to CH materials. However, the CH materials released the greatest amount of MAP-D. Radioactive labelling of MAP-D offers a highly sensitive method of assessing the uptake and release profiles of biocides to CL materials.

Acanthamoeba Keratitis in Egypt: Characteristics and Treatment Outcomes

Purpose

To study the predisposing factors, clinical manifestations, and treatment outcome of patients with Acanthamoeba keratitis (AK) at Tanta University’s Ophthalmology Hospital in Tanta, Egypt.

Methods

A retrospective study of 42 patients (44 eyes) with Acanthamoeba keratitis who had medical records available for review over 4 years.

Results

Forty-four eyes of 42 patients were treated for AK over the study period. In 29 eyes (65.8%), AK was related to contact lens wear. Severe ocular pain was the main presenting symptom in 38 eyes (86.3%). The most common ocular signs were radial perineural corneal infiltrates (65.9%), pseudo-dendrites (43.2%), ring infiltrates (45.5%), and diffuse stromal infiltration (59%). Acanthamoeba was detected by culture, smear, and in-vivo confocal microscopy (IVCM) in 25 eyes (56.8%), while in 19 eyes (43.2%) the diagnosis was based solely on the clinical findings. IVCM was effective in detection of Acanthamoeba in cases with early presentation, while culture was more sensitive in late presentation with corneal melting. The mean duration of treatment was 73.3 ± 23.7 days. Surgical intervention in the form of tectonic grafts or amniotic membrane transplant was required in five cases (11.3%) due to progressive corneal thinning and perforation. Seventeen patients (38.6%) had 0.2 or better final best-corrected visual acuity after treatment.

Conclusion

The diagnosis of AK remains a major challenge for most ophthalmologists. Contact lens abuse is the major risk factor. Early diagnosis and appropriate treatment of AK with biocidal agents can improve the final outcome and help avoid surgical intervention. IVCM is an excellent tool for early diagnosis of AK.

The impact of patient behaviour and care system compliance on reusable soft contact lens complications

Reusable soft daily wear contact lenses (CLs) remain popular and were fit to just over half of all wearers in the most recent international CL prescribing survey. Unlike daily disposable CLs, reusables require cleaning and disinfecting after every use, along with storage in a CL case. These additional requirements add a number of steps to the daily wear and care routine, increasing the opportunities for CL wearers to exhibit non-compliant behaviour. The impact of non-compliance ranges from poor lens comfort through to potentially sight-threatening infective keratitis. The coronavirus pandemic has refocused the profession on the importance of hand hygiene in particular, and the need for promoting safe CL wear in general. This review summarises typical non-compliant behaviour related to reusable CLs, and examines strategies and opportunities to better support wearers. Patient education has a central role in encouraging compliant behaviour, although patient recall of information is low, and personal belief systems may result in continuation of non-compliant behaviour despite awareness of the risks. CL care solutions are required for the daily disinfection of lenses, however misuse of multipurpose solutions (MPS) and hydrogen peroxide (H₂O₂)-based care systems can challenge their ability to be fully efficacious. Standard efficacy testing is reviewed, with consideration of how well current protocols model real-world use of CL solutions. Although some recommendations are in place for the inclusion of additional variables such as lens cases, CL materials, organic soil and efficacy against Acanthamoeba, opportunity still exists to reevaluate global standards to ensure consistency of testing in all markets. Finally, potential future innovations are discussed which may further support increased safety in reusable lens wear through novel antimicrobial additions to both CL materials and cases.

Gas-Permeable Contact Lenses and Water Exposure: Practices and Perceptions

SIGNIFICANCE

This study provides insight into the current recommendations, clinical behaviors, and risk assessments of eye care professionals on the topic of rigid contact lens exposure to tap water. This knowledge may motivate professional organizations to develop initiatives to educate eye care professionals on the dangers of contact lens exposure to water.

PURPOSE

The purpose of this study was to investigate the practice patterns and risk perceptions of eye care professionals regarding gas-permeable contact lens exposure to tap water.

METHODS

A branched-logic survey was started by 320 clinicians, vision scientists, and industry personnel and was fully completed by 272 participants. The survey queried participants about their current practices, recommendations, and perceptions of risk regarding exposure of gas-permeable contact lenses to tap water.

RESULTS

Of those who prescribe gas-permeable contact lenses, 57.4% reported rinsing lenses with tap water, whereas only 32.7% reported engaging in this same behavior in front of patients. Of those who reported never rinsing lenses with tap water, 85.6% indicated that rinsing lenses with water increases infection risk, whereas 52.1% of those who rinse lenses with water reported the same perceived risk (P < .001). Of all participants, 60% indicated that wearing contact lenses while showering increases infection risk, and 50.2% of all participants advised patients to avoid this behavior.

CONCLUSIONS

A discrepancy exists between perceptions of risk concerning exposure of contact lenses to water and both clinical practices and patient education provided by professionals.

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.

Variables Affecting the Recovery of Acanthamoeba Trophozoites

While the results of Acanthamoeba testing have been extensively published, laboratories conducting such testing are left to develop their own methods in the absence of a standardized methodology. The wide disparity of methods has resulted in equally inconsistent reported results for contact lens care (CLC) products. This study's objective was to determine the source of these discrepancies by evaluating basic Acanthamoeba biology and their impact on antimicrobial efficacy testing, including the ability of a recovery method to stimulate a single trophozoite to proliferate. Antimicrobial efficacy testing was conducted using well-published Acanthamoeba strains, storage conditions, and growth-based recovery methods. To identify variables that influence results, test solutions with low Acanthamoeba disinfection rates were utilized to prevent differences from being masked by high log reductions. In addition, single-cell proliferation assays were executed to understand the growth requirements to stimulate trophozoite propagation in two recovery methods. These studies indicated that both nutrient density (>106 CFU) and the length of plate incubation (at least 14 days) could significantly influence the accurate recovery of trophozoites. Together, this study emphasizes the need to understand how Acanthamoeba trophozoites biology can impact test methods to create divergent results.

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.

Development of a contact Lens risk survey

PURPOSE

To describe the development and report psychometric properties of the Contact Lens Risk Survey (CLRS) to identify patients at risk for soft contact lens-related complications.

METHODS

Psychometric properties of the CLRS, a web-based survey with branching logic, were determined using data from 5 multi-site fieldings (n = 1059), including re-fielding to sub groups. Responses from participants with and without an active red eye were used to identify risk factors of a red eye event and calculate an overall risk score. A 6th fielding of the CLRS (n = 171) was used to assess discriminate validity.

RESULTS

Participants needed 11-12 min to complete the survey with a negligible difference by age. Internal consistency was excellent (Cronbach's α ≥ 0.70) for 3 of the 5 constructs identified by factor analysis. Twelve of the 17 survey items exhibited excellent within-subject repeatability (Kappa ≥ 0.61). Between-subject agreement, assessed in 18-25 year olds, was high for the majority of items, suggesting good generalizability across different populations of SCL wearers. The ability of the model using individual items of the CLRS to discriminate Controls and participants with a red eye was good with an area under the curve of 0.779.

CONCLUSION

The CLRS tool is a repeatable and valid instrument to standardize documentation of demographic, behavior, and exposure factors which appear to drive the greatest risk of a contact lens related red eye event.

Is Hydrogen Peroxide Disinfection Effective for Cleaning Pollen Particles Attached to Contact Lenses?

PURPOSE

It has been proven that wearing soft contact lenses (SCLs) can make pollen-induced allergic conjunctivitis worse. We investigated the cleaning effect of disinfectants and rinsing solution on cedar pollen attached to SCLs.

METHODS

Two-week replacement disposable SCLs, to which pollen particles were experimentally attached, were washed and cleaned with either saline of rinsing solution (n = 10) or 3% hydrogen peroxide (n = 10). We observed, under a microscope, the cedar pollen adhered to the SCLs after washing.

RESULTS

The number of residual pollens attached to SCLs was 23.7 ± 25.7 with rinsing solution and 0.2 ± 0.6 with 3% hydrogen peroxide solution per single area (100 µm × 100 µm). The percentage of adhesion area of pollen to the SCLs was 0.9 ± 1.1% with rinsing solution and 0.0 ± 0.0% with 3% hydrogen peroxide solution. There were significant differences in the number of pollen and adhesion areas of pollen between the two groups (p < 0.05 and p < 0.05, respectively).

CONCLUSION

These results suggest that hydrogen peroxide solution is superior in cleaning effect of cedar pollen attached to SCLs compared to saline.

Alkyl-carbon chain length of two distinct compounds and derivatives are key determinants of their anti-Acanthamoeba activities

The opportunistic pathogen, Acanthamoeba castellanii is the causative agent for the sight threatening infection Acanthamoeba keratitis (AK). It is commonly associated with contact lens wearers, and prevalence is increasing at an alarming rate due to an inadequate preventive strategy to protect the lens from this protist. This problem is compounded by the lack of an effective acanthamoebocide, particularly with cysticidal activity in the contact lens solutions. We have used cytotoxicity assays and a variety of biophysical approaches to show that two molecules with tails made of alkyl carbon, alkylphosphocholines (APCs) and quaternary ammonium compounds (QACs) had significant chain-length dependent efficacy against A. castellanii trophozoites, the latter producing death via permeabilization, and DNA complexing. QACs were more effective than APCs and had activity against cysts. Conversely, the QAC with 12 alkyl carbon chain, was non toxic, its presence increased A. castellanii trophozoites biomass and delayed encystation by 96 h. Interestingly, it was unable to induce excystation and increased trophozoite sensitivity to APC16. These results present a mono- and multi-inhibitor management strategy effective against trophozoites and cysts that may be useful for formulating into contact lense cleaning solutions and reducing AK incidence.

Acanthamoeba keratitis in Australia: demographics, associated factors, presentation and outcomes: a 15-year case review

PURPOSE

To report the demographics, frequency of potential predisposing factors, presentation and outcomes of Acanthamoeba keratitis (AK) at a quaternary eye hospital in Sydney, Australia over a 15-year period.

METHODS

A retrospective review of all patients diagnosed with AK at the Sydney Eye Hospital, Sydney, Australia between January 2002 and December 2016 was conducted.

RESULTS

A total of 52 patients with AK at the quaternary referral hospital in Sydney, Australia, between January 2002 and December 2016, were included. The most commonly documented potential predisposing factors were contact lens wear (83%) and organic trauma (10%) in the non-contact lens wearers. An initial misdiagnosis of herpetic eye disease was made in 37% of patients. The presenting clinical features in order of frequency included; punctate epitheliopathy in 65% (n = 34), perineural infiltrate 46% (n = 24), stromal infiltrates 46% (n = 24), anterior uveitis 39% (n = 20), epithelial defect 35% (n = 18), limbitis 31% (n = 16), pseudo-dendrite 19% (n = 10), and ring infiltrate 4% (n = 7). Twenty-seven of the patients completed their follow-up at the Sydney Eye Hospital, improving their vision from 1.02 logMAR at presentation to 0.57 logMAR at last follow-up. Thirty-nine complications developed in 32 eyes and included corneal scarring and vascularisation, three patients experienced recurrences of AK and one patient developed a late-onset scleritis.

CONCLUSION

In Australia, AK occurred predominantly in contact lens wearers with typical clinical features including epitheliopathy and perineural infiltrates. The patient demographics, frequency of potential predisposing factors and clinical presentation of AK were similar to case series from the UK and New Zealand.

Water Exposure and the Risk of Contact Lens-Related Disease

PURPOSE

To describe the association of water exposure with contact lens (CL)-related disease and explore the guidelines regarding water exposure to CL wearers, provided by CL manufacturing industry, global public health, and CL-related professional associations.

METHODS

A review of the literature was conducted by searching PubMed, MEDLINE, and Web of Science databases up to September 2017 for articles published or translated in English using keywords: contact lens* AND tap water OR swimming OR showering OR water exposure AND microbial keratitis OR Acanthamoeba keratitis OR corneal infiltrate* OR ocular adverse event*. References in all relevant publications were also reviewed.

RESULTS

Water exposure during CL wear is associated with complications ranging from sterile corneal infiltrative events to sight-threatening infections. Despite the documented risks due to water exposure, water-related habits are common among CL wearers. This suggests a lack of awareness and understanding regarding the risks among CL wearers and potentially CL practitioners. Discrepancies exist in guidelines for CL hygiene and compliance provided by the CL manufacturing industry, global public health, and CL-related professional associations. There is also widespread use of water imagery within CL marketing and packaging materials. These factors may give rise to confusion among wearers and may contribute toward risk-taking behaviors.

CONCLUSIONS

Consensus among stakeholders about water and CL care is needed. Guidelines should unequivocally advocate for the avoidance of any water exposure including handling CLs with wet hands, rinsing CLs or storage cases in tap water, showering while wearing CLs and swimming with CLs without wearing goggles.

Review of Contact Lens-Related Complications

The purpose of this article is to provide a review of existing literature describing complications with contemporary contact lenses and their management. It is envisioned that this will serve as a useful summary of noninfectious and infectious complications associated with contact lens wear.

Risk factors and clinical signs of severe Acanthamoeba keratitis

Purpose

To determine risk factors and clinical signs for severe Acanthamoeba keratitis (AK) by comparing severe cases with mild cases with good prognosis.

Patients and methods

We reviewed medical records of ten cases of AK (five males and five females) referred to our hospital and classified cases into two groups. One eye that required therapeutic keratoplasty and three eyes with a poor visual acuity (<0.2) on last visit were included in the severe group. Six eyes that had good prognosis with a visual acuity of 1.2 on last visit were classified as mild group. We compared patients’ age, the time required for diagnosis, visual acuity on first visit, the history of steroid eye drops use, and other clinical findings.

Results

The average age of the severe group was older than the mild group (P=0.04). The duration between onset and diagnosis of AK and visual acuity on first visit was not statistically different. A history of steroid eye drop use was found in four eyes of the severe group (100%) and four eyes of the mild group (67%). Keratoprecipitates were found in all severe group eyes and one mild group eye during follow-up (P=0.01). One case in the severe group was diagnosed with diabetes mellitus at initial examination. We detected Staphylococcus epidermis by palpebral conjunctival culture in one case of the severe group.

Conclusion

Aging may be a possible risk factor for severe AK. The presence of keratoprecipitates is a possible sign of severe AK. Attention is also required in patients with comorbidities such as diabetes mellitus and bacterial infection.

Risk Factors for Acanthamoeba Keratitis-A Multistate Case-Control Study, 2008-2011

OBJECTIVE

To identify modifiable risk factors contributing to Acanthamoeba keratitis (AK) infection.

METHODS

A case-control investigation was conducted. Case patients were soft contact lens wearers with laboratory-confirmed AK. Control were soft contact lens wearers ≥12 years of age, with no history of AK. Case patients were recruited from 14 ophthalmology referral centers and a clinical laboratory. Control were matched on state of residence and type of primary eye care provider (ophthalmologist or optometrist). Participants were interviewed using a standardized questionnaire. Univariable and multivariable conditional logistic regression analyses were conducted. Matched odds ratios (mORs) were calculated.

RESULTS

Participants included 88 case patients and 151 matched control. Case patients were more likely to be aged <25 years (unadjusted mOR 2.7, 95% confidence interval 1.3-5.5) or aged >53 years (mOR 2.5, 1.1-5.7), and more likely to be men (mOR 2.6, 1.4-4.8). Unadjusted analyses identified multiple risk factors: rinsing (mOR 6.3, 1.3-29.9) and storing lenses in tap water (mOR 3.9, 1.2-12.3), topping off solution in the lens case (mOR 4.0, 2.0-8.0), having worn lenses ≤5 years (mOR 2.4, 1.3-4.4), rinsing the case with tap water before storing lenses (mOR 2.1, 1.1-4.1), and using hydrogen peroxide (mOR 3.6, 1.1-11.7) versus multipurpose solution. Significant risk factors in multivariable modeling included age >53 years, male sex, topping off, and using saline solution.

CONCLUSIONS

Numerous modifiable risk factors for AK were identified, mostly involving hygiene practices. To reduce the risk of AK, lens wearers should observe recommended lens care practices.

Effect of 2, 6-Dichlorobenzonitrile on Amoebicidal Activity of Multipurpose Contact Lens Disinfecting Solutions

Multipurpose contact lens disinfecting solutions (MPDS) are widely used to cleanse and disinfect microorganisms. However, disinfection efficacy of these MPDS against Acanthamoeba cyst remain insufficient. 2, 6-dichlorobenzonitrile (DCB), a cellulose synthesis inhibitor, is capable of increasing the amoebical effect against Acanthamoeba by inhibiting its encystation. In this study, we investigated the possibility of DCB as a disinfecting agent to improve the amoebicidal activity of MPDS against Acanthamoeba cyst. Eight commercial MPDS (from a to h) were assessed, all of which displayed insufficient amoebicidal activity against the mature cysts. Solution e, f, and h showed strong amoebicidal effect on the immature cysts. Amoebicidal efficacy against mature cysts remained inadequate even when the 8 MPDS were combined with 100 μM DCB. However, 4 kinds of MPDS (solution d, e, f, and h) including 100 μM DCB demonstrated strong amoebicidal activity against the immature cysts. The amoebicidal activity of solution d was increased by addition of DCB. Cytotoxicity was absent in human corneal epithelial cells treated with either DCB or mixture of DCB with MPDS. These results suggested that DCB can enhance the amoebicical activity of MPDS against Acanthamoeba immature cyst in vitro.

Effect of ethanol pretreatment in Acanthamoeba keratitis: a long-term follow-up study

Purpose

The aim of this study was to evaluate the long-term outcomes of ethanol pretreatment in Acanthamoeba keratitis (AK).

Patients and methods

This single-center, retrospective, interventional study included 22 patients (24 eyes) who developed AK and underwent ethanol pretreatment between 2009 and 2015. Samples for smears, polymerase chain reaction, and culture for evidence of Acanthamoeba were collected. After ethanol pretreatment, the patients were treated with corneal epithelial debridement, topical 0.02% polyhexamethylene biguanide, and 0.1% propamidine isethionate. The primary outcomes were a clinically stable ocular surface, complete recovery from corneal infection, and acceptable corneal haze. The secondary outcome measure was improvement in best-corrected visual acuity. Complications and predictors of the visual outcome were also recorded.

Results

Ethanol pretreatment was successful in 20 (83.3%) of the 24 eyes, and no further optical keratoplasty was required. Four eyes required rescue therapeutic keratoplasty because of rapid progression of AK. Patients in whom ethanol pretreatment was successful achieved good final visual outcomes regardless of sex, age, or causative Acanthamoeba species. Patients with worse initial best-corrected visual acuity and rigid gas permeable lens-related AK had better improvement in vision.

Conclusion

Ethanol as a pretreatment for AK is safe and effective. Combined with corneal epithelial debridement, ethanol pretreatment may preclude the need for optical and therapeutic keratoplasty. This technique is suitable for all stages of AK presenting within 3 weeks of symptom onset and achieves favorable results especially in early AK.