Imaging improvements reveal guttae development and posterior fibrillar layer formation in fuchs endothelial corneal dystrophy

Guttae are a hallmark of Fuchs endothelial corneal dystrophy (FECD) and the disease’s progression. A posterior fibrillar layer (PFL) that covers central guttae has been previously described, but its formation and progression remain unclear. This study aims to further investigate the characteristics of guttae and the PFL in FECD. In a well-characterized prospective FECD patient cohort, a total of 43 DMEK (Descemet membrane endothelial keratoplasty) specimens were immunostained for ZO1 or COL1, flat-mounted, and analyzed using differential interference contrast (DIC), autofluorescence (excited at 480 nm), and polarized light microscopy. Guttae and PFL were quantified and correlated with clinical data. Guttae were visualized by DIC and autofluorescence imaging and classified into two types with gradual transition: peripheral, knob-like guttae and central, flat guttae. Guttae with low autofluorescence often were covered by corneal endothelial cells (CEnC). Central guttae were found to be covered by a PFL that contained COL1 and was visualized using polarized light microscopy. The PFL displayed a fibrous structure that blurred guttae in DIC illumination. Its presence correlated with clinical parameters, such as anterior scatter and post-operative corneal edema resolution providing insight into the relation of PFL and FECD severity. The combination of DIC, autofluorescence, and polarized light microscopy provides a robust method for investigating guttae and the PFL. This could facilitate preoperative assessment of corneal donor tissue and enhance postoperative clinical diagnostics by detailed detection of guttae and PFL in patients.