Assessment of tomographic parameters and detection of subclinical edema in Fuchs' endothelial corneal dystrophy pre-cataract surgery

Abstract

Aim: To assess tomographic changes and subclinical edema detection in Fuchs' endothelial corneal dystrophy (FECD) through Scheimpflug tomography in a group of phakic patients contemplating cataract surgery.

Methods: A retrospective study was conducted on 30 phakic eyes from patients diagnosed with FECD but without clinical edema, and 59 phakic eyes from a control group without corneal alterations. Comprehensive ophthalmic examinations were conducted, including slit-lamp biomicroscopy, corneal specular microscopy (CSM), and Scheimpflug tomography.

Results: The study encompassed 30 phakic eyes with FECD (mean age 59.8±13.1y) and 59 control eyes (mean age 61.3±7.7y). The best-corrected visual acuity was higher in the control group compared to the FECD group [0 (0, 0.08) vs 0.05 (0, 0.15) logMAR; P=0.042]. CSM revealed significant differences between the FECD and control groups in several parameters: number of analyzed cells (26±13 vs 135±42, P<0.001), cell density (2049±376 vs 2479±225 cells/mm², P<0.001), mean cell area [463 (434, 544) vs 397 (383, 431) µm²; P<0.001], coefficient of variation (54.8%±18.7% vs 41.0%±7.2%, P<0.001), and hexagonal cells [0 (0, 47%) vs 47% (40%, 53%), P<0.001]. Although often used as a clinical parameter for detecting edema, central corneal thickness measured by CSM showed no significant difference between the FECD and control groups (530±57 vs 546±30 µm, P=0.179). Significant differences were noted in various Pentacam measurements between the groups. Specifically, parameters like loss of parallel isopachs (13 vs 0 eyes, P<0.001), displacement of the thinnest point (11 vs 0 eyes, P<0.001), posterior focal depression (25 vs 7 eyes, P<0.001), and increased light scatter [21.4 (17.6; 23.9) vs 18.0 (16.8, 21.8), P=0.01] were significantly more prevalent in FECD eyes, reflecting the presence of subclinical edema and loss of corneal transparency.

Conclusion: Scheimpflug tomography allows for an objective assessment of FECD, offering the capability to detect subclinical edema at an early stage, monitor disease progression, and serve as a predictor of corneal decompensation following cataract surgery.

Keywords: Fuchs'; anterior eye segment; cornea; corneal; endothelial dystrophy; endothelium; tomography.

Figure 1. Mayo Clinic classification-tomographic features of corneal edema in Fuchs' endothelial corneal dystrophy

The tomography maps of a left cornea affected by Fuchs' endothelial corneal dystrophy, utilizing Pentacam's “4 Maps Refractive” output. Key observations include 1) the loss of parallel and circular/oval isopachs and 2) the displacement of the cornea's thinnest point (indicated by a small black circle), both visible in the pachymetry map (lower left). Additionally, 3) a focal posterior depression of the posterior corneal surface (down to -19 relative to the best fit sphere) is evident in the posterior elevation map (lower right). The axial power (upper left) and anterior elevation (upper right) maps predominantly show oblique astigmatism. A large central black circle, with a diameter of 4 mm, is superimposed on the center of the lower maps for reference. The pupil center is denoted by a plus sign.

Figure 2. Densitometry analysis of Pentacam Scheimpflug images–general overview display

This image depicts the left eye of a patient with Fuchs' endothelial corneal dystrophy, featuring a characteristic pattern resembling two spiking humps similar to a hanging hammock (yellow circle).