Clinical Evolution and Multimodal Imaging of Late Onset Severe Focal Stromal Degeneration After Corneal Collagen Cross-Linking for Keratoconus

Purpose: To report 2 cases of severe focal stromal degeneration (SFSD) in keratoconic eyes after corneal collagen cross-linking (CXL) with a later onset than previously described. Method: Single-center report of 2 cases. Results: A 46-year-old woman and a 39-year-old man underwent bilateral CXL using the Dresden protocol for progressive keratoconus. SFSD developed bilaterally in the male patient and in the left eye of the female patient 14 and 9 years post-CXL, respectively. Clinically, SFSD presented as localized stromal thinning with a surrounding demarcation line containing round, whitish lesions resembling post-LASIK epithelial pearls. Anterior segment optical coherence tomography demonstrated focal Bowman layer disruption with an underlying rectangular anterior stromal defect, bordered by a thin, hyperreflective contour containing round hyperreflective structures. In vivo confocal microscopy revealed stromal disruption populated by hyperreflective, polymorphic polygonal epithelioid cells. Five months later, anterior segment optical coherence tomography showed progression in depth and width of the defects, and corneal topography indicated ectasia progression at the lesion site in the female patient. Best-corrected visual acuity declined from 0.5 to 1.0 LogMAR, necessitating deep anterior lamellar keratoplasty. In the male patient, asymmetric progression of the lesions and ectasia was observed, with stable best-corrected visual acuity (0.2 LogMAR in the right eye and 0.1 LogMAR in the left eye). Conclusions: SFSD may present later than previously reported. Corneal multimodal imaging provides a characteristic profile of SFSD, aiding in its identification and monitoring.