Abstract
Purpose :
In vivo confocal microscopy (IVCM) has become a key method of diagnosing infectious keratitis, with Acanthamoeba having a distinct appearance on confocal scans. Our retrospective, observational case series investigates the utility and ability of IVCM, after the initial diagnosis and during treatment of Acanthamoeba keratitis (AK), to differentiate active versus resolved infection.
Methods :
Three patients were seen in the outpatient clinic setting with AK cysts visualized via IVCM and confirmed through PCR. All 3 cases were treated with a prolonged course of topical chlorhexidine, topical polyhexamethylene biguanide, and at least one course of oral miltefosine. Case 1 is a 57-year-old female who was diagnosed in September 2021 and underwent corneal biopsy and ocular surface reconstruction with amniotic membrane graft in October 2023. Case 2 is a 53-year-old male who was diagnosed with AK in July 2022 and received a corneal transplant in March 2023. Case 3 is a 42-year-old female diagnosed with AK in May 2023 who underwent lamellar keratectomy in September 2023. IVCM scans were used to diagnose and monitor treatment progression of AK. Histopathologic examination of excised corneal tissue was used to clinically correlate the presence on confocal microscopy with disease activity. All 3 patients were still receiving low dose topical AK treatment at the time of imaging and corneal tissue sampling.
Results :
Prior to surgery, the three patients were treated for AK pharmacologically for between 6 and 26 months (mean = 16 months). Despite appropriate treatment, IVCM results showed continued cyst visualization at depths between 100 and 500 microns. The histopathologic examination of corneal surgical specimens demonstrated necrotic stroma containing degenerate cysts in Case 1 and Case 2, and cysts in both viable and degenerative stages in Case 3.
Conclusions :
The visualization of pathology confirmed degenerate Acanthamoeba cysts on in vivo confocal microscopy has not been previously documented. Confocal microscopy may not be a reliable method of diagnosing active disease with regards to Acanthamoeba keratitis. This finding significantly challenges the current understanding of this disease’s management and the role of confocal microscopy in diagnosis, ultimately emphasizing the importance of corneal cultures and biopsies in diagnosis and monitoring.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.