Therapeutic penetrating keratoplasty for acanthamoeba keratitis: a review of cases, complications and predictive factors

Understanding Acanthamoeba Keratitis: An In-Depth Review of a Sight-Threatening Eye Infection

Acanthamoeba keratitis (AK) is a rare but potentially sight-threatening corneal infection caused by the Acanthamoeba parasite. This microorganism is found ubiquitously in the environment, often in freshwater, soil, and other sources of moisture. Despite its low incidence, AK presents significant challenges due to delayed diagnosis and the complex nature of therapeutic management. Early recognition is crucial to prevent severe ocular complications, including corneal ulceration and vision loss. Diagnostic modalities and treatment strategies may vary greatly depending on the clinical manifestation and the available tools. With the growing reported cases of Acanthamoeba keratitis, it is essential for the ophthalmic community to thoroughly understand this condition for its effective management and improved outcomes. This review provides a comprehensive overview of AK, encompassing its epidemiology, risk factors, pathophysiology, clinical manifestations, diagnosis, and treatment.

Comparison of therapeutic effects between big-bubble deep anterior lamellar keratoplasty and penetrating keratoplasty for medically unresponsive Acanthamoeba keratitis

PURPOSE

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.

CONCLUSION

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.

New Frontiers in Acanthamoeba Keratitis Diagnosis and Management

Acanthamoeba Keratitis (AK) is a severe corneal infection caused by the Acanthamoeba species of protozoa, potentially leading to permanent vision loss. AK requires prompt diagnosis and treatment to mitigate vision impairment. Diagnosing AK is challenging due to overlapping symptoms with other corneal infections, and treatment is made complicated by the organism's dual forms and increasing virulence, and delayed diagnosis. In this review, new approaches in AK diagnostics and treatment within the last 5 years are discussed. The English-language literature on PubMed was reviewed using the search terms "Acanthamoeba keratitis" and "diagnosis" or "treatment" and focused on studies published between 2018 and 2023. Two hundred sixty-five publications were initially identified, of which eighty-seven met inclusion and exclusion criteria. This review highlights the findings of these studies. Notably, advances in PCR-based diagnostics may be clinically implemented in the near future, while antibody-based and machine-learning approaches hold promise for the future. Single-drug topical therapy (0.08% PHMB) may improve drug access and efficacy, while oral medication (i.e., miltefosine) may offer a treatment option for patients with recalcitrant disease.

The role of the calcofluor white staining in the diagnosis of Acanthamoeba keratitis

PURPOSE

Acanthamoeba keratitis is often misdiagnosed at disease onset. This study presents data to confirm the diagnosis using calcofluor white (CFW) staining.

METHODS

Forty three patients were retrospectively included who presented to the Department of Ophthalmology at the University Hospital Ulm with keratitis between 2000 and 2022. Condition positive cases were diagnosed based on the typical clinical presentation of Acanthamoeba keratitis with a positive polymerase chain reaction (PCR). Condition negative were patients with ulcers due to other causing pathogens with a negative Acanthamoeba PCR result. The condition was compared with the CFW test results.

RESULTS

After symptom onset, time until presentation was 17 ± 12 days and until diagnosis 27 ± 13 days in the 15 condition positive patients. Among the 35 patients with additional CFW test, 7 patients were condition positive and 28 negative. 5 of the 7 patients were true positive, 2 were false negative. In the 28 condition negative patients, 1 was false positive. Sensitivity of CFW was 71% and specificity 96%. The positive PCR results were available 3.4 ± 2.3 days after corneal scraping, the positive CFW test results on the same day in each case.

CONCLUSION

Our data demonstrate that diagnosis of Acanthamoeba keratitis remains difficult and therapy is initiated late. A positive CFW test confirms the diagnosis as there are almost no false positive results and it was available faster than PCR. In case of a negative CFW test, Acanthamoeba keratitis cannot be ruled out because of a high false negative rate.

Polyhexamethylene biguanide hydrochloride (PHMB)-properties and application of an antiseptic agent. A narrative review

The prevention and management of ocular surface infections is still one of the great challenges for ophthalmologists. The spread of antimicrobial resistance makes it necessary to use antiseptic substances with a broad antimicrobial spectrum. Polyhexamethylene biguanide hydrochloride (Polyhexanide, PHMB) is a broad-spectrum antiseptic with excellent tolerance and a low-risk profile. Its physicochemical action on the phospholipid membrane and DNA replication or repair mechanism, prevents or impedes the development of resistant bacterial strains. PHMB revealed its effective against numerous organisms like viruses, Gram-negative and Gram-positive bacteria, and fungi. Polyhexanide is commonly used as preservative in commercially available disinfecting solutions for contact lens care and in ophthalmic formulations at different concentrations ranging from 1 µg/ml to 50 µg/ml. The administration of 0.02% (200 µg/ml) PHMB is often the first-line therapy of Acanthamoeba keratitis. However, to date, only one close-out randomized controlled study tested the efficacy of 0.02% PHMB in Acanthamoeba keratitis and a phase III study is still ongoing. This paper reviews the antiseptic agent PHMB, focusing on biochemical mechanisms, safety profile and applications in ophthalmology.

Oral Miltefosine as Salvage Therapy for Refractory Acanthamoeba Keratitis

PURPOSE

To report a case series of patients with treatment-resistant Acanthamoeba keratitis (AK) using oral miltefosine, often as salvage therapy.

DESIGN

Descriptive, retrospective multicenter case series.

METHODS

We reviewed 15 patients with AK unresponsive to therapy who were subsequently given adjuvant systemic miltefosine between 2011 and 2017. The main outcome measures were resolution of infection, final visual acuity, tolerance of miltefosine, and clinical course of disease.

RESULTS

All patients were treated with biguanides and/or diamidines or azoles without resolution of disease before starting miltefosine. Eleven of 15 patients retained count fingers or better vision, and all were considered disease free at last follow-up. Eleven of 15 patients had worsening inflammation with miltefosine, with 10 of them improving with steroids. Six patients received multiple courses of miltefosine. Most tolerated oral miltefosine well, with mild gastrointestinal symptoms as the most common systemic side effect.

CONCLUSIONS

Oral miltefosine is a generally well-tolerated treatment adjuvant in patients with refractory AK. The clinician should be prepared for a steroid-responsive inflammatory response frequently encountered during the treatment course.

Challenges in Acanthamoeba Keratitis: A Review

To review challenges in the diagnosis and management of Acanthamoeba keratitis (AK), along with prognostic factors, in order to help ophthalmologists avoid misdiagnosis, protracted treatment periods, and long-term negative sequelae, with an overarching goal of improving patient outcomes and quality of life, we examined AK studies published between January 1998 and December 2019. All manuscripts describing clinical manifestations, diagnosis, treatment, prognosis, and challenges in short- and long-term management were included. The diagnosis of AK is often challenging. An increased time between symptom onset and the initiation of appropriate therapy is associated with poorer visual outcomes. The timely initiation of standardized antiamoebic therapies improves visual outcomes, decreases the duration of treatment, and reduces the chances of needing surgical intervention. In clinical practice, AK diagnosis is often missed or delayed, leading to poorer final visual outcomes and a negative impact on patient morbidity and quality of life.

Parasitic keratitis - An under-reported entity

Parasitic keratitis (PK) is unique entity among parasitic infections where corneal involvement could result from direct inoculation of the parasite via exogenous environment or spread via endogenous neighboring organs or as a result of immune-mediated damage secondary to a systemic parasitic infection. Most cases of PK are caused by Acanthamoeba spp. and Microsporidia spp. though few other parasitic agents can also lead to corneal involvement. Mimicking as other infectious and non-infectious causes of keratitis, PK often escapes detection. This review summarizes the predominant causes of PK along with the epidemiological, clinical and microbiological details of each. Though several gaps exist in our understanding of the prevalence of PK, the one thing for sure is that PK is on the rise. With advanced diagnostic modalities and enough literature on optimal management of cases of PK, it is now imperative that a strong clinical suspicion of PK is kept when examining a case of corneal pathology and adequate investigations are ordered.