Morphological Distinction of Descemet's Membrane Protrusions in Bullous Keratopathy and Guttae in Fuchs Endothelial...

To characterize dome-shaped protrusions (DSPs), a previously unrecognized alteration of Descemet's membrane (DM) in bullous keratopathy (BK), and to determine how DSPs differ from classic guttae in Fuchs endothelial corneal dystrophy (FECD).

DM specimens were collected from 75 eyes with BK during endothelial keratoplasty. A subset of eyes with sufficiently dense protrusions (≥50 per field at ×200 magnification) was selected for detailed analyses. Flat-mounted DMs were examined by phase-contrast microscopy, scanning electron microscopy, and immunofluorescence staining. Quantitative analyses included measurements of protrusion area, centroid spacing, and density. Texture characteristics were assessed using fast Fourier transform, gray-level co-occurrence matrix metrics, and local binary pattern profiling.

DSPs appeared as small, blurred-edge elevations lacking the halo and fusion typical of guttae. Compared with guttae, DSPs showed smaller areas (mean of 69.5 µm² vs. 148.7 µm²), greater centroid spacing (21.8 µm vs. 15.3 µm), and lower density (161 protrusions/mm² vs. 359 protrusions/mm²) (P < 0.01 for all). Scanning electron microscopy demonstrated smooth, nodular excrescences in FECD, whereas DSPs displayed fine fibrillar surfaces. Immunohistochemistry revealed strong periguttae fibronectin and collagen I deposition in FECD, whereas DSPs were negative for both markers and were instead surrounded by diffuse staining across the DM surface. The fast Fourier transform, gray-level co-occurrence matrix, and local binary pattern analyses showed that DSPs exhibited smoother, more homogeneous, and less anisotropic microtexture signatures than were observed for FECD guttae.

DSPs may represent a previously unrecognized pattern of DM remodeling in BK. Their discovery provides new insight into endothelial stress responses.