Acquired Corneal Subepithelial Hypertrophy: First Ultrastructural Characterization by Transmission Electron Microscopy

ABSTRACT: Acquired corneal subepithelial hypertrophy (ACSH) is a rare corneal condition whose ultrastructural features have not previously been characterized. We report the first detailed ultrastructural analysis of ACSH in a 57-year-old man with a history of penetrating keratoplasty for corneal trauma followed by Descemet stripping automated endothelial keratoplasty who presented with progressive visual decline due to a superficial corneal opacity. Clinical evaluation included slitlamp biomicroscopy, anterior segment optical coherence tomography, corneal topography, and pachymetry, which localized the lesion to the subepithelial compartment. The lesion was managed with selective surgical peeling, and the excised tissue was examined by light microscopy and transmission electron microscopy. Surgical removal led to restoration of best-corrected visual acuity with no recurrence at 1-year follow-up. Histopathological analysis demonstrated irregular epithelial thickening, complete absence of Bowman layer, and subepithelial fibrosis with myofibroblast proliferation, without evidence of inflammation or neovascularization. Ultrastructural examination revealed epithelial mitochondrial damage with mitophagy, disruption of intercellular junctions, and subepithelial myofibroblasts containing abundant rough endoplasmic reticulum, consistent with active fibrotic remodeling. These findings support ACSH as an acquired corneal fibrotic process driven by wound healing mechanisms, with clinical, epidemiological, and histopathological features distinct from other corneal degenerations and confirmed that surgical peeling of the thickened epithelial and subepithelial tissue can be curative.