Confocal microscopy as an early relapse marker for acanthamoeba keratitis

Diagnosing and monitoring the characteristics of Acanthamoeba keratitis using slit scanning and laser scanning in vivo confocal microscopy

INTRODUCTION

Acanthamoeba keratitis (AK) is a serious and potentially blinding ocular infection caused by the free-living amoeba, Acanthamoeba. In vivo confocal microscopy (IVCM) is a non-invasive device which has been proven of great use to diagnose Acanthamoeba infections immediately. The aim of this review was to establish different patterns and signs of AK that appear on the IVCM both before and after treatment.

METHODS

A systematic review of the literature from 1974 until September 2021 was performed using Embase and PubMed, following The Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

Twenty different signs of AK were observed using IVCM. The included studies used vastly different criteria to diagnose infections, ranging from just 1 to 13 of the signs, demonstrating the current lack of a standardised diagnosis of this infection using the IVCM. The appearance of double wall cysts, trophozoites, signet rings, target signs and clusters were shown to be pathognomonic to AK infections. Bright spots located in the corneal epithelium were demonstrated as non-reliable predictors of AK. The presence of cysts in clusters and single file can predict the need for corneal transplantation. The morphological changes in cysts using the IVCM following treatment were described as breaking down to hollow forms and occasionally surrounded by black cavities. Using this information, a visual guideline for identifying AK signs in diagnosis and follow-up using IVCM was created.

CONCLUSION

Increased awareness of the different signs and patterns of AK that appear on the IVCM is crucial in order to correctly identify an infection and increase the potential of this device. Our guidelines presented here can be used, but further studies are needed in order to determine the relationship and aetiology of these signs and cellular changes on the IVCM both before and after anti-amoeba treatment.

[Modern corneal diagnostics as the key for the correct classification of the disease and optimal treatment decisions]

Corneal diseases include a wide spectrum of different manifestations (inflammatory/noninflammatory) that need to be accurately classified for precise diagnosis and targeted treatment. In addition to the anamnesis and slit lamp biomicroscopy, further device-based examinations can be performed to narrow down the diagnosis. Nowadays, modern corneal imaging provides a variety of technologies, such as topography, tomography, in vivo confocal microscopy and analysis of biomechanics, which are able to reliably classify different pathologies. Knowledge of the available examination modalities helps to guide differential diagnostic considerations, facilitating the indication for stage-appropriate microsurgical intervention.

Novel Map Biopsy Technique to Define the Extent of Infection Before Penetrating Keratoplasty for Acanthamoeba Keratitis

PURPOSE

The purpose of this study was to report a novel approach of prepenetrating keratoplasty (PKP) corneal map biopsies to define the extent of Acanthamoeba cyst infiltration in recalcitrant Acanthamoeba keratitis.

METHODS

Corneal map biopsies were performed 1 week before PKP. Four biopsies, 1 from each peripheral corneal quadrant, were obtained to delineate the extent of microscopic infection. Histological results of these map biopsies were used to determine the size and location of the subsequent PKP.

RESULTS

In our first case, map biopsies revealed Acanthamoeba cysts in 2 of the 4 biopsies. This led to an inferotemporally eccentric 8.5-mm PKP. The final histology report indicated that the closest resection margin was 0.08 mm. In our second case, the peripheral map biopsies were clear and an inferiorly eccentric 8.25-mm PKP was performed. The final histology report indicated that the closest resection margin was 2.3 mm. Both grafts have remained clear at 6 months postoperatively.

CONCLUSIONS

Map biopsies of the cornea can achieve total removal of the corneal tissues infested with Acanthamoeba cysts and prevent reinfection of the donor graft.

Impact of implementation of polymerase chain reaction on diagnosis, treatment, and clinical course of Acanthamoeba keratitis

PURPOSE

Acanthamoeba keratitis (AK) is a painful and possibly sight-threatening ocular infection. While the correct diagnosis and specific treatment in the early stages significantly improve the prognosis, the disease is often misdiagnosed and in clinical examination confused with other forms of keratitis. Polymerase chain reaction (PCR) for the detection of AK was first introduced in our institution in December 2013 to improve the timely diagnosis of AK. The aim of this study was to assess the impact of implementation of Acanthamoeba PCR on the diagnosis and treatment of the disease in a German tertiary referral center.

PATIENTS AND METHODS

Patients treated for Acanthamoeba keratitis between 1st of January 1993 and 31st of December 2021 in the Department of Ophthalmology of the University Hospital Duesseldorf were identified retrospectively via in-house registries. Evaluated parameters include age, sex, initial diagnosis, method of correct diagnosis, duration of symptoms until correct diagnosis, contact lens use, visual acuity, and clinical findings as well as medical and surgical therapy by keratoplasty (pKP). In order to assess the impact of implementation of Acanthamoeba PCR, the cases were divided into two groups (before (pre-PCR group) and after PCR implementation (PCR group).

RESULTS

Seventy-five patients with Acanthamoeba keratitis were included (69.3% female, median age 37 years). Eighty-four percent (63/75) of all patients were contact lens wearers. Until PCR was available, 58 patients with Acanthamoeba keratitis were diagnosed either clinically (n = 28), by histology (n = 21), culture (n = 6), or confocal microscopy (n = 2) with a median duration until diagnosis of 68 (18; 109) days. After PCR implementation, in 17 patients, the diagnosis was established with PCR in 94% (n = 16) and median duration until diagnosis was significantly shorter with 15 (10; 30.5) days. A longer duration until correct diagnosis correlated with a worse initial visual acuity (p = 0.0019, r = 0.363). The number of pKP performed was significantly lower in the PCR group (5/17; 29.4%) than in the pre-PCR group (35/58; 60.3%) (p = 0.025).

CONCLUSIONS

The choice of diagnostic method and especially the application of PCR have a significant impact on the time to diagnosis and on the clinical findings at the time of confirmation of diagnosis and the need for penetrating keratoplasty. In contact lens-associated keratitis, the first crucial step is to take AK into consideration and perform a PCR test as timely confirmation of diagnosis of AK is imperative to prevent long-term ocular morbidity.

A Review of Imaging Biomarkers of the Ocular Surface

A biomarker is a "characteristic that is measured as an indicator of normal biological processes, pathogenic processes, or responses to an exposure or intervention, including therapeutic interventions." Recently, calls for biomarkers for ocular surface diseases have increased, and advancements in imaging technologies have aided in allowing imaging biomarkers to serve as a potential solution for this need. This review focuses on the state of imaging biomarkers for ocular surface diseases, specifically non-invasive tear break-up time (NIBUT), tear meniscus measurement and corneal epithelial thickness with anterior segment optical coherence tomography (OCT), meibomian gland morphology with infrared meibography and in vivo confocal microscopy (IVCM), ocular redness with grading scales, and cellular corneal immune cells and nerve assessment by IVCM. Extensive literature review was performed for analytical and clinical validation that currently exists for potential imaging biomarkers. Our summary suggests that the reported analytical and clinical validation state for potential imaging biomarkers is broad, with some having good to excellent intra- and intergrader agreement to date. Examples of these include NIBUT for dry eye disease, ocular redness grading scales, and detection of corneal immune cells by IVCM for grading and monitoring inflammation. Further examples are nerve assessment by IVCM for monitoring severity of diabetes mellitus and neurotrophic keratitis, and corneal epithelial thickness assessment with anterior segment OCT for the diagnosis of early keratoconus. However, additional analytical validation for these biomarkers is required before clinical application as a biomarker.

In Vivo Confocal Microscopy and Anterior Segment Optical Coherence Tomography Analysis of the Microcystic Keratitis

Purpose

To describe the findings of in vivo confocal microscopy (IVCM) and anterior segment optical coherence tomography (AS-OCT) in a case of bilateral acute microcystic epitheliopathy after daily soft contact lens wear.

Methods

IVCM and AS-OCT were used in the course of the bilateral epitheliopathy of a 23-year-old patient at the acute stage of the disease and at recovery after four days of treatment. The images were analyzed and compared.

Results

On AS-OCT of the right eye, general hyperreflectivity and the increased thickness of the central corneal epithelium to 150 μm with numerous hyporeflective small, oval cysts were revealed and resolved completely at day 4 after diagnosis and treatment. AS-OCT scans of the left eye revealed oval shaped, hyperreflective material within the corneal epithelium. IVCM of both eyes showed numerous microcysts of different sizes filled with hyperreflective material mostly within superficial epithelial layers. Epithelial cells showed a polymorphism along with disruption of a cytoarchitecture. Basal epithelial cells and anterior stroma showed inflammatory changes. Posterior corneal stroma and endothelium presented normal morphology.

Conclusions

Microcystic keratitis appeared as localized microcystic inflammation of epithelium on AS-OCT, which was confirmed by IVCM. Both IVCM and AS-OCT are helpful diagnostic instruments in case of cystic inflammation of corneal epithelium.

Development and Assessment of a Simulator for in Vivo Confocal Microscopy in Fungal and Acanthamoeba Keratitis

BACKGROUND AND PURPOSE

In vivo confocal microscopy (IVCM) is a non-invasive imaging technique that allows morphological analysis as a diagnostic approach of the cornea in real time, thus providing a suspected diagnosis of fungal or amoebic keratitis immediately, whereas culture or PCR require several days or even weeks. Since these infections are rare, it is difficult for ophthalmologists to gain the experience necessary to differentiate infection from normal findings or artefacts. The purpose of this project was to establish a simulator, on which physicians could practice as well as acquiring a database of IVCM images of fungal or amoebic keratitis and respective analyses.

PATIENTS AND METHODS

An IVCM simulator was set up with cadaver human corneas, infected with either acanthamoeba, candida or aspergillus. Twenty-one ophthalmologists were trained in IVC microscopy first in a Dry Lab, then practically on the simulator. For evaluation, the participants were asked to fill out a standardized questionnaire, with a pre- and post-course self-assessment.

RESULTS

The self-assessed theoretical and practical skills in differentiating infectious from non-infectious keratitis in IVCM significantly increased (p = 0.0001, p = 0.0002, respectively). The barrier to use this technique decreased (p = 0.0474).

CONCLUSION

A very simple protocol based on a model of ex vivo corneal mycotic and amoebic infections can be used to train novices in the structured approach and diagnostic use of IVCM for corneal infections.

Clinical diagnosis and treatment of rare painless keratitis caused by three pathogens: clinical practice and experiential discussion

There have been numerous reports regarding the occurrence of keratitis in patients with soft contact lenses, but few reports in patients with rigid gas permeable contact lenses. To the best of our knowledge, the occurrence of infection associated with three species of pathogens has never been reported. Here, we describe a patient who exhibited refractory painless keratitis caused by three pathogens (Staphylococcus epidermidis, Acanthamoeba, and herpes simplex virus) and summarize similar reports published at multiple centers worldwide, with the aim of providing guidance for clinicians who might encounter mixed-type corneal infections. We describe the results of many ophthalmologic and laboratory investigations, which guided our treatment selection. We achieved good treatment efficacy, such that the patient exhibited a corrected visual acuity of 20/20 in the affected eye after a series of treatments, including curettage of ulcer lesions. Corneal infections caused by multiple pathogens are challenging in clinical practice. This summary of our experience in patient diagnosis and treatment can help clinicians to achieve a favorable prognosis in treatment of future patients.

Early Penetrating Keratoplasty À Chaud May Improve Outcome in Therapy-Resistant Acanthamoeba Keratitis

INTRODUCTION

Long-standing acanthamoeba keratitis (AK) may result in corneal neovascularization, extension of the infiltrate to the limbus or sclera, broad peripheral synechiae, mature cataract or ischemic posterior segment inflammation. We investigated the impact of early emergency penetrating keratoplasty (PKP) in therapy-resistant cases among the patients of a highly specialized tertiary care center.

METHODS

In this retrospective, observational cohort within a single institution, we collected data on best-corrected visual acuity (BCVA), epithelial wound healing, graft survival and secondary complications of AK patients who underwent PKP. A total of 23 eyes of 23 patients diagnosed with acute, therapy-resistant AK between 2006 and 2015 were enrolled. Postoperative combined topical treatment was tapered for 6-9 months.

RESULTS

Eyes were grouped based on preoperative disease duration as shorter (group 1) or longer (group 2) than the median. The median was 5.3 (0.66-36) months. The BCVA in group 1 (20/44 ± 20/18; 0.32 ± 0.18 logMAR) was significantly better than in group 2 (20/1200 ± 20/1133; 1.28 ± 0.89; logMAR); p = 0.015. Persisting epithelial defects occurred in 5 patients (50%) of group 1 and in 10 patients (77%) of group 2. In 5 eyes (group 2), no epithelial healing could be achieved. After 36 months, graft survival (Kaplan-Meier) was 78% (18 grafts) for all patients (90% in group 1 and 44% in group 2).

CONCLUSION

PKP à chaud within 5.3 months after first symptoms of therapy-resistant AK seems to result in better final BCVA than delayed graft surgery if the disease is resistant to a classical topical triple therapy. In addition, early PKP may have a favorable impact on epithelial healing and graft survival.

FUNDING

We thank the Alexander von Humboldt Foundation for supporting the work of Prof. N. Szentmáry at the Department of Ophthalmology of Saarland University Medical Center in Homburg/Saar, Germany. We thank the University of Saarland for funding the medical writing assistance and the Rapid Service Fees. The funding organisation had no role in the design or conduct of this research.

Reduction of Acanthamoeba Cyst Density Associated With Treatment Detected by In Vivo Confocal Microscopy in Acanthamoeba Keratitis

PURPOSE

Acanthamoeba keratitis (AK) is a severe vision-threatening ocular infection that is frequently a diagnostic challenge. Treatment course is lengthy and often not fully effective. Contact lens wear has been recognized as the prime risk factor for AK. In vivo confocal microscopy (IVCM) is a noninvasive imaging modality that allows direct visualization of potential causative pathogens in real time with an established utility in the diagnosis of AK. In this study, we aim to assess the utility of IVCM in monitoring disease progression in contact lens wearers with culture-confirmed keratitis.

METHODS

Fourteen eyes from 11 patients with culture-confirmed AK were included in this retrospective study. IVCM was performed during the patient's initial visit and all follow-up visits. All available confocal sequences were reviewed and graded in a masked fashion. Density of Acanthamoeba cyst infiltration and changes in the cyst density as a percentage of baseline cyst density measured at each patient's initial visit were calculated. A univariate regression analysis was performed to assess the association between treatment and changes in cyst density per month of treatment.

RESULTS

Acanthamoeba cysts were identified by IVCM in all of these culture-confirmed cases of keratitis. Mean cyst density in the central cornea at presentation was 99 ± 64.9 cells per square millimeter (range, 38-255/mm). Cyst density in our study population significantly decreased by approximately 5.3% with each month of antiamebic treatment (P = 0.001; R = 0.41).

CONCLUSIONS

Reduction in Acanthamoeba cyst density with treatment can be monitored by IVCM, which in turn can be used clinically in prognostication and disease monitoring of AK.

Acanthamoeba keratitis - Clinical signs, differential diagnosis and treatment

PURPOSE

To summarize actual literature data on clinical signs, differential diagnosis, and treatment of acanthamoeba keratitis.

METHODS

Review of literature.

RESULTS

Clinical signs of acanthamoeba keratitis are in early stages grey-dirty epithelium, pseudodendritiformic epitheliopathy, perineuritis, multifocal stromal infiltrates, ring infiltrate and in later stages scleritis, iris atrophy, anterior synechiae, secondary glaucoma, mature cataract, and chorioretinitis. As conservative treatment, we use up to one year triple-topical therapy (polyhexamethylene-biguanide, propamidine-isethionate, neomycin). In therapy resistant cases, surgical treatment options such as corneal cryotherapy, amniotic membrane transplantation, riboflavin-UVA cross-linking, and penetrating keratoplasty are applied.

CONCLUSION

With early diagnosis and conservative or surgical treatment, acanthamoeba keratitis heals in most cases.

Effectiveness of sampling methods employed for Acanthamoeba keratitis diagnosis by culture

PURPOSE

This retrospective, observational study was designed to evaluate the effectiveness of the sampling methods commonly used for the collection of corneal scrapes for the diagnosis of Acanthamoeba keratitis (AK) by culture, in terms of their ability to provide a positive result.

METHODS

A total of 553 samples from 380 patients with suspected AK received at the Parasitology Section of the Public Health Institute of Chile, between January 2005 and December 2015, were evaluated. A logistic regression model was used to determine the correlation between the culture outcome (positive or negative) and the method for sample collection. The year of sample collection was also included in the analysis as a confounding variable.

RESULTS

Three hundred and sixty-five samples (27%) from 122 patients (32.1%) were positive by culture. The distribution of sample types was as follows: 142 corneal scrapes collected using a modified bezel needle (a novel method developed by a team of Chilean corneologists), 176 corneal scrapes obtained using a scalpel, 50 corneal biopsies, 30 corneal swabs, and 155 non-biological materials including contact lens and its paraphernalia. Biopsy provided the highest likelihood ratio for a positive result by culture (1.89), followed by non-biological materials (1.10) and corneal scrapes obtained using a modified needle (1.00). The lowest likelihood ratio was estimated for corneal scrapes obtained using a scalpel (0.88) and cotton swabs (0.78).

CONCLUSION

Apart from biopsy, optimum corneal samples for the improved diagnosis of AK can be obtained using a modified bezel needle instead of a scalpel, while cotton swabs are not recommended.

[Diagnostics and treatment of infectious keratitis]

We summarize up-to-date diagnostic and treatment of infectious keratitis using literature data and some clinical examples. In the clinical practice, most commonly bacterial, herpetic, mycotic and acanthamoeba keratitis occur. Beside slitlamp examination, for diagnostic purpose, we analyse corneal sensitivity, perform in vivo confocal microscopy, polymerase-chain-reaction (PCR), in vitro culture and histological examination of the corneal sample. As conservative treatment we use primarily topical moxifloxacin or cephasolin with fortified tobramycin or gentamycin in bacterial, topical antiviral gel (in some cases in combination with systemic antiviral treatment) in part in combination with topical corticosteroids in herpetic, voriconasole or amphotericin-B in mycotic, and topical-triple-therapy (diamidine, biguanid and antibiotics) in acanthamoeba keratitis. In case of early diagnosis and initiation of topical therapy, most cases of infectious keratitis recover successfully. However, beside conservative treatment, penetrating keratoplasty, amniotic membrane transplantation and crosslinking therapy may be necessary. Crosslinking is solely contraindicated in herpetic keratitis. Orv Hetil. 2017; 158(31): 1203-1212.