Clinical and genetic investigation of amantadine-associated corneal edema

Purpose: Amantadine use has been temporally associated with bilateral corneal edema in a series of cases; however, its pathophysiological mechanisms have yet to be elucidated. We sought to rule out subclinical Fuchs dystrophy as a contributor, characterize its pattern of corneal edema, and describe the long-term outcome of concurrent topical steroids while resuming amantadine. Patient and methods: After a 44-year-old woman presented with new acute onset bilateral corneal edema, amantadine was discontinued, with clinical improvement. However, neurological decompensation required restarting amantadine, which she did concurrently with topical loteprednol. To determine whether subclinical Fuchs dystrophy might be present, triplet-primed polymerase chain reaction was conducted to measure copy number of the CTG18.1 trinucleotide repeat in TCF4. Specular microscopy and Scheimpflug imaging were conducted and followed for 32 months to assess for resolution and stability. Literature review was conducted to assess for consistency of the clinical phenotype. Results: Corneal edema resolved clinically 4 weeks after discontinuation of amantadine. Serial Scheimpflug imaging demonstrated resolution of posterior and central corneal edema and specular microscopy revealed intracellular opacities with loss of endothelial cell density. Despite resuming amantadine, Scheimpflug imaging and specular microscopy measurements remained stable at 32 months. Triplet-primed PCR of CTG18.1 in TCF4 revealed no trinucleotide repeat expansion. Conclusions: Amantadine-associated corneal edema is characteristically posterior and central and appears unlikely to represent early or subclinical decompensation of Fuchs dystrophy. We describe the unique outcome of continued corneal clearance after restarting amantadine concurrently with steroids, a pattern that has persisted over 32 months to date.