Abstract
Purpose :
To investigate the ultrastructural changes in the corneas of patients with Fuchs’ endothelial corneal dystrophy (FECD) using in vivo confocal microscopy through focusing (CMTF). Using CMTF, we measured anterior stromal haze and quantified subbasal nerve plexus parameters in subjects with variable disease severity of FECD. Since a CTG trinucleotide repeat expansion in the TCF4 gene has been implicated in 70% of Caucasian patients, we performed subgroup analysis on patients with and without the expansion.
Methods :
A cohort of patients with Krachmer grades 1-6 FECD was recruited and genotyped for the triplet repeat expansion using short tandem repeat and triplet repeat-primed polymerase chain reaction assays. The Krachmer grade at the time of imaging was assigned by a single fellowship trained corneal specialist. CMTF was performed on 52 eyes of 28 subjects. Anterior stromal haze was measured in confocal backscatter units (CBU) as the area under the curve of the first 50 microns of stroma. Nerve plexus analysis was performed manually and reported as the average obtained from eight nonoverlapping images per eye. Corneal nerve fiber length (CNFL) was measured using a tracing tool and defined as the total length of all nerves in a given image. Corneal nerve branch density (CNBD) was defined as number of nerve branch points in a given image. Corneal nerve fiber density (CNFD) equals the number of individual nerve fibers in a given image excluding branches of less than 50% in length of the original nerve.
Results :
Anterior stromal haze increases with increasing Krachmer grade, and this correlation remains true in patients with and without the triplet repeat expansion. In the entire cohort, CNFL and CNBD decrease with increasing Krachmer grade. On subgroup analysis, these correlations remain true only in patients in whom the triplet expansion is present. CNFD decreases with increasing Krachmer grade only in expansion positive patients (Table).
Conclusions :
Anterior stromal haze correlates to FECD disease severity irrespective of the genotype. Loss of corneal nerve fiber length, branch density, and fiber density with increasing disease severity was detected only in patients with the triplet repeat expansion. Loss of the subbasal nerve plexus may represent a novel imaging biomarker for FECD mediated by the triplet repeat expansion and contribute to disease pathogenesis.
This is a 2020 ARVO Annual Meeting abstract.