Scheimpflug backscatter imaging of the fibrillar layer in Fuchs endothelial corneal dystrophy

Am J Ophthalmol. 2021 Sep 9;S0002-9394(21)00437-2. doi: 10.1016/j.ajo.2021.08.019. Online ahead of print.

Abstract

Purpose: 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 if the FL may be visualized by en face Scheimpflug backscatter imaging in vivo.

Design: Retrospective analysis of a prospective observational case series.

Methods: Thirty-four 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. 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 n=26 eyes and was FL-negative in n=8 eyes with deviation compared to immunofluorescence in one case and good agreement of morphology characteristics. Horizontal caliper diameter±standard deviation was 4.84±0.85mm, vertical caliper diameter was 3.92±0.78mm, maximum caliper diameter was 5.12±0.82mm and surface area was 12.43±4.74mm2. Compared to immunofluorescence imaging, mean difference (95% limits of agreement (LOA)) and ICC were for horizontal caliper diameter 0.13mm(-0.81 to 1.1mm) and 0.88, vertical caliper diameter 0.23mm(-0.76 to 1.2mm) and 0.81, maximum caliper diameter 0.06mm(-1.1 to 1.2mm) and 0.86 and surface area 1.4 mm2(-3.9 to 6.7 mm2) and 0.85.

Conclusion: 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.

Keywords: Descemet membrane; Fuchs endothelial corneal dystrophy; Scheimpflug; backscatter; buried guttae; corneal endothelial cell density; densitometry; fibrillar layer.