Change In Corneal Thickness After Descemet Membrane Endothelial Keratoplasty In Fibrillar Layer Positive Vs Negative Fuchs Endothelial Corneal Dystrophy Eyes

Central geographic subendothelial collagen deposits termed fibrillar layer (FL), are found in approximately 80% of eyes with advanced Fuchs' endothelial corneal dystrophy (FECD).  A previous study showed that FL-positive FECD eyes have increased central corneal thickness (CCT) values compared to FL-negative eyes preoperatively. However, the effect of FL status on CCT after successful Descemet's membrane endothelial keratoplasty (DMEK) has not been investigated. The aim of this study was to compare whether the postoperative CCT change after successful DMEK differs according to the FL status of the cornea.

Tertiary referral center.

Advanced FECD eyes (modified Krachmer grade 5 or 6) scheduled for DMEK or triple DMEK surgery and with high-quality preoperative Scheimpflug imaging and 6 months of follow-up were included in this retrospective single center study. Corneal densitometry maps were exported and pre- and postoperative CCT values were recorded. FL status was determined through corneal densitometry maps and FL areas were segmented. Pre- and postoperative CCT values were compared between cases. For FL-positive cases, FL area and FL caliper diameters were correlated with CCT change.

100 FL-positive and 24 FL-negative patients were included. Preoperative CCT was 633.4 ± 50.9 μm in FL-positive eyes vs. 577.8 ± 34.8 μm in FL-negative eyes. Postoperative CCT was 525.3 ± 39.0 μm in FL-positive eyes vs. 542.9 ± 35.9 μm in FL-negative eyes, resulting in a mean CCT change of 108.1 ± 43.2 μm in FL-positive eyes vs. 34.9 ± 25.2 μm in FL-negative eyes (p<0.0001). Correlation analysis showed moderate to strong correlations of FL area and dimensions with change in CCT (FL area – ΔCCT r=0.517, p<0.001; maximum caliper diameter -  ΔCCT r=0.578, p<0.001; horizontal caliper diameter -  ΔCCT r=0.566, p<0.001; vertical caliper diameter - ΔCCT r=0.468, p<0.001).

The presence of FL is associated with increased preoperative corneal thickness and more corneal edema The presence of an FL may therefore be predictive of increased postoperative CCT reduction despite preoperative CCT variations in physiological corneal thickness in the patient population. Successful DMEK may result in a greater decrease in corneal thickness in FL-positive eyes, which may lead to a greater refractive change. FL identified by Scheimpflug backscatter imaging may therefore be a morphological marker of more edematous/advanced FECD status and should be considered in the surgical planning for refractive outcome after DMEK. Further studies are needed to evaluate the diagnostic and prognostic value of FL in FECD.