Ocular Microbiology and Immunology Group
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2026 OMIG Abstract

Persistent Cysts in the Explanted Cornea Predict Graft Failure in Acanthamoeba Keratitis

Felipe Echeverri Tribin¹, Helen Song², Wendy Li³, Brandon Chou⁴, Jaime Martinez³, Sander Dubovy³, Darlene Miller^3,5, and Guillermo Amescua^3,5

¹Ophthalmic Biophysics Center, Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida; ²University of Illinois Chicago, Department of Ophthalmology and Visual Sciences, Chicago, Illinois; ³Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida; ⁴Department of Ophthalmology, Yale School of Medicine, New Haven, Connecticut; ⁵Ocular Microbiology Laboratory, Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida

Purpose: To determine whether histopathologic cyst-positivity of the excised cornea predicts graft failure in Acanthamoeba keratitis (AK), and to characterize long-term outcomes.

Methods: A retrospective review was conducted of all patients initially diagnosed with AK at Bascom Palmer Eye Institute (BPEI) from 2015 - 2026. Patients were divided into two groups based on whether their treatment regimen included miltefosine or without. Further subgroups were identified as follows: no corticosteroid use, established corticosteroid use prior to infection, steroids started prior to anti-amoebic therapy, and steroids started after anti-amoebic therapy.

Results: Most patients were contact lens wearers (78%); median age was 49 years and 60% were referred from external providers. Cultures confirmed the diagnosis in 64% of eyes, and corneal histopathology established AK in 11 eyes with non-diagnostic cultures. More than 90% of speciated isolates were A. castellanii (T4 genotype), indicating a microbiologically homogeneous cohort. The competing-risks cumulative incidence of medical cure was 49% at one year, plateauing near 67%, with resolution often protracted (median anti-amoebic therapy, 133 days); approximately one-third of eyes required therapeutic keratoplasty. Penetrating keratoplasty (therapeutic or optical) was performed in 67% of eyes. Among 50 grafts with evaluable follow-up, failure occurred in 13 (26%) and persistent cysts in corneal buttons were strongly associated with failure (53% [8/15] vs 14% [5/35]; HR 4.5, 95% CI 1.5-13.9; log-rank p=0.004). Visual acuity improved overall, from a median of 20/200 to 20/60 (median change -0.37 logMAR; p=0.002).

Conclusions: Corneal histopathology carries both diagnostic and prognostic value in AK. Tissue examination revealed the diagnosis in eyes with non-diagnostic cultures, and persistence of cysts in the excised cornea strongly predicted subsequent graft failure within a genotypically homogeneous cohort. Medical cure was achieved in roughly two-thirds of eyes, though resolution was often prolonged. Two-thirds of eyes underwent keratoplasty. Cyst status at keratoplasty may guide postoperative surveillance, re-grafting decisions, and patient counseling.