Brillouin Microscopy Visualizes Centralized Corneal Edema in Fuchs Endothelial Dystrophy

Abstract

Purpose-To investigate the feasibility of using Brillouin microscopy for assessment of corneal edema in patients with Fuchs' Endothelial Corneal Dystrophy (FECD). Brillouin microscopy analyzes the frequency shift of light inelastically scattered by naturally occurring acoustic waves in a small volume of tissue. The resulting frequency shift is a measure of the local hydromechanical properties of the tissue.Methods-Participants were scanned using a clinical Brillouin imaging system (780 nm laser, 5 mW) and a color-coded map of the mean Brillouin shift laterally across the corneal stroma was created.Results-Brillouin maps of normal subjects (n = 8) were relatively homogeneous, while FECD patients' (n = 7) maps exhibited significantly reduced Brillouin shifts (unpaired t test, P < .001) centrally. The mean difference of 83 MHz corresponds to approximately 3.9% higher water content (percentage difference in volume fraction) in central corneas of FECD group relative to normal subjects. The Brillouin scan of a FECD patient 1-month after Descemet membrane endothelial keratoplasty (DMEK) measured a 62 MHz increase in Brillouin shift relative to preoperative level, indicating normalization of corneal hydration.Conclusions-All FECD patients scanned exhibited a centralized reduction in Brillouin shift, distinct from the normal subjects measured, and consistent with centralized edema characterized by pachymetry. Brillouin scans revealed substantially reduced water content after DMEK. These results suggest that Brillouin microscopy could aid treatment planning and assessment of FECD. Moreover, corneal hydration mapping may be useful in understanding fluid pump function dynamics of the cornea and developing early interventions for FECD.

Advances in Imaging Technology of Anterior Segment of the Eye

“…Brillouin frequency shift was shown to have negative correlation with corneal hydration, [ 52 ] which might be helpful in evaluating abnormal hydration change associated with endothelial dysfunction. Eltony et al [ 53 ] revealed that patients with Fuchs' endothelial dystrophy showed a centralized reduction in Brillouin shift, which was consistent with central corneal edema. Brillouin microscopy also detected substantially reduced corneal hydration after Descemet membrane endothelial keratoplasty (DMEK) [ 53 ].…”

“…Eltony et al [ 53 ] revealed that patients with Fuchs' endothelial dystrophy showed a centralized reduction in Brillouin shift, which was consistent with central corneal edema. Brillouin microscopy also detected substantially reduced corneal hydration after Descemet membrane endothelial keratoplasty (DMEK) [ 53 ].…”

“…Brillouin microscopy can be useful in the management of corneal endothelial disorders and monitoring the disease severity [ 52 , 53 ]. Brillouin frequency shift was shown to have negative correlation with corneal hydration, [ 52 ] which might be helpful in evaluating abnormal hydration change associated with endothelial dysfunction.…”

Detecting Mechanical Anisotropy of the Cornea Using Brillouin Microscopy

“…30 Recently, the effects of water content on frequency shift have been investigated, 31 and Brillouin microscopy has been used to detect the changes in corneal hydration that accompany Fuchs Corneal Dystrophy. 32 From a mechanical standpoint, Brillouin microscopy probes micron-level unit volumes. In this scale, Brillouin microscopy measurements of anisotropy are not sensitive to macro-level changes in hydration unless such changes in hydration affect fiber distribution at a micron-scale level.…”