OBJECTIVE: To provide an overview on the incidence of Acanthamoeba Keratitis (AK).
CONCLUSIONS: Although being a major and sight-threatening cause of infectious keratitis in the population, a comprehensive assessment of the incidence of this condition is lacking.
METHODS: Incidence of AK was computed as the number of AK eyes, per healthcare center, per year (annualized-center-incidence, or ACI). Two meta-analytical ratios were also calculated: a) the ratio of AK eyes to the count of non-viral microbial keratitis (MK) eyes; b) the ratio of AK eyes to the overall population (i.e., the total number of subjects of a nation or region, as indicated by the authors in each study). Center was defined as the healthcare facility (e.g., Hospital, Private Practice, Clinic) where the study took place. Actual and projected estimates of the number of AK eyes in years were calculated multiplying the ratio of AK to the total population and the corresponding present and projected population estimates (age range: 15 to 70), sourced from the United Nations (UN) Population Prospects.
RESULTS: Overall, 105 articles were included, published between 1987 and 2022. The total number of eyes identified was 91,951, with 5,660 affected by AK and 86,291 by non-viral MK. The median ACI was 1.9 new AK eyes per healthcare center per year (95%CI of the median: 1.5 to 2.6), with no statistically significant differences observed among continents. The ratio of AK eyes to the total number of MK eyes was 1.52% (95%CI: 1.02% to 2.24%), while the ratio of AK in relation to the entire population was estimated at 0.0002% (95%CI: 0.0001 to 0.0006), or 2.34 eyes per 1,000,000 subjects (95%CI: 0.98 to 5.55 per 1.000.000 subjects). The projected increase in the numbers of AK eyes indicates a rise of +18.5% (15,356 AK eyes) in 2053 and +25.5% (16,253 AK eyes) in 2073, compared to the baseline of 2023 (12,954 AK eyes) CONCLUSION: AK emerged as a relatively low-incident disorder, and no significant differences in terms of its incidence were found among different continents.

Acanthamoeba, a free-living amoeba, is commonly found in various natural environments, such as rivers and soil, as well as in public baths, swimming pools, and sewers. Acanthamoeba can cause severe illness such as granulomatous amoebic encephalitis and Acanthamoeba keratitis (AK) in humans. AK, the most recognized disease, can cause permanent visual impairment or blindness by affecting the cornea. AK commonly affects contact lens wearers who neglect proper cleaning habits. The symptoms of AK include epithelial and stromal destruction, corneal infiltrate, and intense ocular pain, occasionally necessitating surgical removal of the entire eyeball. Current AK treatment involves the hourly application of eye drops containing polyhexamethylene biocide (PHMB). However, studies have revealed their ineffectiveness against drug-resistant strains. Acanthamoeba can form cysts as a survival mechanism in adverse environments, though the exact mechanism remains unknown. Our experiments revealed that sodium P-type ATPase (ACA1_065450) is closely linked to encystation. In addition, various encystation buffers, such as MgCl2 or NaCl, induced the expression of P-type ATPase. Furthermore, we used ouabain, an ATPase inhibitor, to inhibit the Na+/K+ ion pump, consequently decreasing the encystation rate of Acanthamoeba. Our primary objective is to develop an advanced treatment for AK. We anticipate that the combination of ouabain and PHMB may serve as an effective therapeutic approach against AK in the future.

OBJECTIVE: To compare the outcomes of big-bubble deep anterior lamellar keratoplasty (BB-DALK) and penetrating keratoplasty (PKP) in the management of medically unresponsive Acanthamoeba keratitis (AK).
METHODS: This retrospective study included 27 eyes of BB-DALK and 24 eyes of PKP from a tertiary ophthalmology care centre. Glucocorticoid eye drops were subsequently added to the treatment plan 2 months postoperatively based on the evaluation using confocal laser scanning microscopy. The clinical presentations, best-corrected visual acuity (BCVA), postoperative refractive outcomes, graft survival, and Acanthamoeba recurrence were analyzed.
RESULTS: The AK patients included in the study were in stage 2 or stage 3, and the percentage of patients in stage 3 was higher in the PKP group (P = 0.003). Clinical presentations were mainly corneal ulcers and ring infiltrates, and endothelial plaques, hypopyon, uveitis and glaucoma were more common in the PKP group (P = 0.007). The BCVA and the graft survival rate showed no statistically significant differences between the two groups at 1 year after surgery. However, 3 years postoperatively, the BCVA of 0.71 ± 0.64 logMAR, the graft survival rate of 89.5%, and the endothelial cell density of 1899 ± 125 cells per square millimeter in the BB-DALK group were significantly better than those of the PKP group (P = 0.010, 0.046, and 0.032, respectively). 3 eyes (11.1%) in the BB-DALK group and 2 eyes (8.3%) in the PKP group experienced Acanthamoeba recurrence, but the rates showed no statistically significant difference between the two groups (P = 1.000). In the PKP group, immune rejection and elevated intraocular pressure were observed in 5 and 6 eyes, respectively.
CONCLUSIONS: Corneal transplantation is recommended for AK patients unresponsive to antiamoebic agents. The visual acuity and graft survival can be maintained after BB-DALK surgery. Acanthamoeba recurrence is not related to the surgical approach performed, whereas complete dissection of the infected corneal stroma and delayed prescribing of glucocorticoid eye drops were important to prevent recurrence.

To investigate the relationship between Acanthamoeba genotypes, clinical manifestations, and outcomes in Acanthamoeba keratitis (AK) patients.
This retrospective study included 159 culture-confirmed AK patients. Patients\' data were collected, including demographics, initial diagnosis, treatments, and clinical features. The genotype of Acanthamoeba was identified through sequencing the Diagnostic Fragment 3 (DF3) region in the small ribosomal subunit RNA genes. The phylogenetic tree was constructed using the ClustalW model and maximum likelihood method. Cases with \"poor outcome\" were defined based on specific clinical criteria, including corneal perforation, keratoplasty, other eye surgery, duration of anti-amoebic therapy ≥8.0 months, and final visual acuity ≤20/80. \"Better outcome\" cases were the remainder. The correlation between T4 subtypes, clinical phenotypes, and clinical prognosis were further analyzed.
In this study, AK was primarily attributed to the T4A genotype, with a positive correlation between geographical and genetic distances. The primary clinical associated with T4 subtypes was deep stromal infiltration. Results was also showed a significant association between T4 subtypes and clinical outcomes (P = 0.021). Further analysis revealed that T4C was closely associated with a better prognosis (P = 0.040) and T4D with worse outcomes (P = 0.013).
In China, AK was predominantly caused by the T4A subtype. Geographical distance positively correlated with genetic distance. Clinical prognosis varied among different subtypes, notably in T4C and T4D.
This study demonstrated the association between T4 subtypes and clinical phenotypes, as well as the effects of T4 subtypes on clinical prognosis.

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 (AK) is an intractable infection of the cornea. Penetrating keratoplasty is widely used for the management of severe AK but suffers from complications like graft rejection, endophthalmitis, and glaucoma. Herein, we aimed to describe the surgical technique and the results of elliptical deep anterior lamellar keratoplasty (eDALK) for the management of severe AK. In this retrospective case series, records of consecutive patients with AK poorly responsive to medical treatment who underwent eDALK from January 2012 to May 2020 were reviewed. The largest diameter of infiltration was ≥8 mm and did not involve the endothelium. The recipient bed was made by an elliptical trephine, and big bubble or wet-peeling technique was performed. Postoperative best spectacle-corrected visual acuity, endothelial cell density, corneal topographic data, and complications were evaluated. Thirteen eyes of thirteen patients (eight men and five women, 45.54 ± 11.78 years old) were included in this study. The mean follow-up interval was 21.31 ± 19.59 months (range, 12-82 months). At the last follow-up, the mean best spectacle-corrected visual acuity was 0.35 ± 0.27 logarithm of the minimum angle of resolution. The mean refractive and topographic astigmatism were - 3.21 ± 1.77 and 3.08 ± 1.14 D, respectively. Intraoperative perforation was encountered in one case and double anterior chambers occurred in two cases. One graft developed stromal rejection and one eye developed amoebic recurrence. eDALK can serve as the first-line surgical management of severe AK poorly responsive to medical treatment.

Acanthamoeba keratitis (AK) is a blinding corneal infection caused by the protozoan Acanthamoeba. The long-term course of AK suggests the host immunity could not kill Acanthamoeba rapidly. The immune status is still unclear in the late stage of AK. The comparative transcriptome analysis was made based on the bulk RNA sequencing of cornea tissues from AK patients and donors. Differentially expressed genes and enriched signaling pathways were calculated. CIBERSORT algorithm was used for immune infiltration analysis of cornea tissue between AK and normal controls. A total of 2668 differentially expressed genes, including 1477 upregulated genes and 1191 downregulated genes, were detected. Gene Ontology analysis revealed that the pathways were significantly enriched in leukocyte migration, regulation of T-cell activation, the external side of plasma membrane, collagen-containing extracellular matrix, immune receptor activity, and cytokine binding. The Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that the pathways were significantly enriched in the cytokine-cytokine receptor interaction, hematopoietic cell lineage, and Staphylococcus aureus infection pathway. The immune infiltration profiles varied little between AK and normal controls. Compared with normal tissue, cornea tissue of AK contained a higher proportion of M0 macrophages and CD8 T cells, while resting memory CD4 T cells contributed to a relatively lower portion (p < 0.05). Finally, the expression levels of cell markers and SLAMF7/STAT6 pathway were confirmed by histopathology examinations, RT-qPCR, and Western blot.

This study aimed to develop a miltefosine-eluting contact lens (MLF-CL) device that would allow sustained and localized miltefosine release for the treatment of Acanthamoeba keratitis. MLF-CLs were produced in three different miltefosine doses by solvent-casting a thin miltefosine-polymer film around the periphery of a methafilcon hydrogel, which was then lathed into a contact lens. During seven days of in vitro testing, all three formulations demonstrated sustained release from the lens at theoretically therapeutic levels. Based on the physicochemical characterization of MLF-CLs, MLF-CL\'s physical properties are not significantly different from commercial contact lenses in terms of light transmittance, water content and wettability. MLF-CLs possessed a slight reduction in compression modulus that was attributed to the inclusion of polymer-drug films but still remain within the optimal range of soft contact lenses. In cytotoxicity studies, MLF-CL indicated up to 91% viability, which decreased proportionally as miltefosine loading increased. A three-day biocompatibility test on New Zealand White rabbits revealed no impact of MLF-CLs on the corneal tissue. The MLF-CLs provided sustained in vitro release of miltefosine for a week while maintaining comparable physical features to a commercial contact lens. MLF-CL has a promising potential to be used as a successful treatment method for Acanthamoeba keratitis.

OBJECTIVE: To investigate the effect of therapeutic keratoplasty (TKP) in patients with severe Acanthamoeba keratitis (AK) and to analyse the clinical features and risk factors for recurrence.
METHODS: Clinical data of patients with severe AK treated with lamellar keratoplasty (LK) or penetrating keratoplasty (PK) due to ineffective drug therapy were analysed in this retrospective study. The effects of keratoplasty, clinical features, and risk factors for recurrence were analysed.
RESULTS: The cohort comprised of 58 patients (59 eyes). Of these, 36 eyes were treated with PK and 23 were treated with LK. The probabilities of successful globe salvage were 91.7% and 91.3%, respectively. The final visual acuity (VA) was ≥ 20/60 in 14 eyes (38.9%) that underwent PK and 15 eyes (65.2%) that underwent LK. Postoperative recurrence of Acanthamoeba infection was detected in 10 eyes; 6 eyes (16.7%) showed recurrence after PK, and 4 eyes (17.4%) showed recurrence after LK. Recurrence occurred between 3 and 80 days (median, 14.5 days) after the operation. The risk factors for recurrence after LK were topical corticosteroid use before diagnosis (p = 0.040) and hypopyon (p = 0.009), while those after PK were topical corticosteroid use before diagnosis (p = 0.045). Clinical manifestations of postoperative recurrence include greyish-white infiltration of the recipient bed, anterior chamber inflammation, graft oedema, and keratic precipitate.
CONCLUSIONS: TKP is a treatment option for severe AK that responds poorly to antiamoebic therapy (AAT), although Acanthamoeba infection may relapse, and the visual prognosis is guarded. Topical corticosteroid use before AAT and hypopyon is the two risk factors for recurrence.

We examined the anti-acanthamoebic efficacy of green tea Camellia sinensis solvent extract (SE) or its chemical constituents against Acanthamoeba castellanii by using anti-trophozoite, anti-encystation, and anti-excystation assays. C. sinensis SE (625-5000 µg/mL) inhibited trophozoite replication within 24-72 h. C. sinensis SE exhibited a dose-dependent inhibition of encystation, with a marked cysticidal activity at 2500-5000 µg/mL. Two constituents of C. sinensis, namely epigallocatechin-3-gallate and caffeine, at 100 μM and 200 μM respectively, significantly inhibited both trophozoite replication and encystation. Cytotoxicity analysis showed that 156.25-2500 µg/mL of SE was not toxic to human corneal epithelial cells, while up to 625 µg/mL was not toxic to Madin-Darby canine kidney cells. This study shows the anti-acanthamoebic potential of C. sinensis SE against A. castellanii trophozoites and cysts. Pre-clinical studies are required to elucidate the in vivo efficacy and safety of C. sinensis SE.