Correlation of Clinical Fibrillar Layer Detection and Corneal Thickness in Advanced Fuchs Endothelial Corneal Dystrophy

Central subendothelial geographic deposits are formed as a fibrillar layer (FL) in advanced Fuchs endothelial corneal dystrophy (FECD). Previous studies demonstrated a significant decrease in corneal endothelial cell (CEC) density and an increase in focal corneal backscatter in the FL area. The present study investigated the association of the FL with edema formation and its localization. Patients (n = 96) presenting for Descemet membrane endothelial keratoplasty (DMEK) for advanced FECD were included. Slit-lamp biomicroscopy with FECD grading was followed by Scheimpflug imaging with en face backscatter analysis and pachymetric analysis. FL dimensions were measured, and correlation with pachymetric values was performed. An FL was detected in 74% of all eyes (n = 71). Pachymetric values in FL-positive versus FL-negative eyes were for corneal thickness at the apex (ACT) 614 ± 52 µm and 575 ± 46 µm (p = 0.001), for peripheral corneal thickness at 1 mm (PCT_1mm) 616 ± 50 µm and 580 ± 44 µm (p = 0.002), for PCT_2mm 625 ± 48 µm and 599 ± 41 µm (p = 0.017), for PCT_3mm 651 ± 46 µm and 635 ± 40 µm (p = 0.128) and for PCT_4mm 695 ± 52 µm and 686 ± 43 µm (p = 0.435), respectively. Correlation analysis indicated a weak correlation for the FL maximum vertical caliper diameter with ACT and PCT_1mm values but no further relevant correlations. In FL-positive eyes, increased focal corneal backscatter and increased corneal thickness showed primarily central and inferotemporal localization. In conclusion, Scheimpflug imaging shows an association of the FL with increased corneal thickness in advanced FECD and shows localization of the FL and increased corneal thickness in the central and inferotemporal region. This may provide important information for progression assessment and therapeutic decision making in FECD patients in the future.

Scheimpflug Backscatter Imaging of the Fibrillar Layer in Fuchs Endothelial Corneal Dystrophy

A central collagen-rich subendothelial fibrillar layer (FL) correlates with areas of accentuated loss of corneal endothelial cells in advanced Fuchs endothelial corneal dystrophy (FECD). The present study sought to investigate whether the FL may be visualized by en face Scheimpflug backscatter imaging in vivo.

DESIGN

Retrospective analysis of a prospective observational case series.

METHODS

A total of 34 eyes (34 subjects) undergoing Descemet membrane endothelial keratoplasty (DMEK) surgery with preoperative high-quality Scheimpflug backscatter imaging data were included. The Descemet endothelium complex (DEC) was retrieved during DMEK surgery, and immunofluorescence staining was performed for collagens I, III, and IV. The FL morphology in en face Scheimpflug backscatter and immunofluorescence imaging was compared and agreement of FL parameters was analyzed using intraclass correlation coefficients (ICC) and Bland-Altman plots.

RESULTS

Scheimpflug backscatter imaging delineated the FL in 26 eyes and was FL negative in 8 eyes with deviation compared to immunofluorescence in 1 case and good agreement of morphology characteristics. Horizontal caliper diameter ± SD was 4.84 ± 0.85 mm, vertical caliper diameter was 3.92 ± 0.78 mm, maximum caliper diameter was 5.12 ± 0.82 mm, and surface area was 12.43 ± 4.74 mm². Compared to immunofluorescence imaging, mean difference (95% limits of agreement) and intraclass correlation coefficients were for horizontal caliper diameter 0.13 mm (-0.81 to 1.1 mm) and 0.88, vertical caliper diameter 0.23 mm (-0.76 to 1.2 mm) and 0.81, maximum caliper diameter 0.06 mm (-1.1 to 1.2 mm) and 0.86, and surface area 1.4 mm² (-3.9 to 6.7 mm²) and 0.85.

CONCLUSIONS

Scheimpflug backscatter imaging facilitates visualization of the FL in advanced FECD eyes, offering the potential to identify particularly diseased areas of the FECD endothelium in vivo.