Simultaneously imaging and quantifying in vivo mechanical properties of crystalline lens and cornea using optical coherence elastography with acoustic radiation force excitation

Abstract

The crystalline lens and cornea comprise the eye’s optical system for focusing light in human vision. The changes in biomechanical properties of the lens and cornea are closely associated with common diseases, including presbyopia and cataract. Currently, most in vivo elasticity studies of the anterior eye focus on the measurement of the cornea, while lens measurement remains challenging. To better understand the anterior segment of the eye, we developed an optical coherence elastography system utilizing acoustic radiation force excitation to simultaneously assess the elasticities of the crystalline lens and the cornea in vivo . A swept light source was integrated into the system to provide an enhanced imaging range that covers both the lens and the cornea. Additionally, the oblique imaging approach combined with orthogonal excitation also improved the image quality. The system was tested through first ex vivo and then in vivo experiments using a rabbit model. The elasticities of corneal and lens tissue in an excised normal whole-globe and a cold cataract model were measured to reveal that cataractous lenses have a higher Young’s modulus. Simultaneous in vivo elasticity measurements of the lens and cornea were performed in a rabbit model to demonstrate the correlations between elasticity and intraocular pressure and between elasticity and age. To the best of our knowledge, we demonstrated the first in vivo elasticity of imaging of both the lens and cornea using acoustic radiation force-optical coherence elastography, thereby providing a potential powerful clinical tool to advance ophthalmic research in disorders affecting the lens and the cornea.

Ultrahigh-sensitive optical coherence elastography

“…The back-reflected light from the compensation arm is detected by the second channel of the balanced photodetector to offset the DC component of the generated interference fringes. A balanced photodetector with a bandwidth from 30 kHz to 1.6 GHz was selected to minimize timing jitters to enhance the phase stability and to enable a long imaging range for retrieving the two OCT interference fringes from different frequency domains 14 .…”

“…Most OCE systems utilizing the acoustic radiation force (ARF) as a tissue excitation method are reported to have the capability of detecting displacements in the range of hundreds of nanometers. In those cases, a relatively strong ARF is necessary to accurately reconstruct the elastic wave propagation, and this force may exceed the ophthalmic mechanical index (MI) safety standard of 0.23 approved by the Food and Drug Administration [13][14][15] . An OCE system with ultrahigh displacement sensitivity will be able to scale down the applied ARF by at least 1 order of magnitude while maintaining a sufficient signal-tonoise ratio (SNR), which will reduce the required ARF such that it is within the range of the MI safety standard to facilitate the clinical translation of OCE in ophthalmology.…”

“…A lambda (λ) trigger using a fiber Bragg grating (FBG) as well as a kclock generated by a Mach-Zehnder interferometer (MZI) have been introduced to improve the phase stability, making SS-OCT a more attractive setup in OCE applications 28 . In recent years, several OCE systems based on conventional SS-OCT (SS-OCE COV ) have been proposed 14,[29][30][31][32][33][34][35] , and their feasibilities have been validated through ex vivo and in vivo experiments, demonstrating great potential towards clinical translation. Although these studies have reported subnanometre displacement sensitivities, this is achieved only in system charaterization where a simple common-path configuration is used.…”

Advances in Doppler optical coherence tomography and angiography

“…(B) Spatial distribution of the cilia beating frequency at 23 C, 26 C, 29 C, and 33 C in which temperature has a positive impact on ciliary activity. Adapted from References [86,87] simultaneously assess the elasticities of the crystalline lens and the cornea in vivo (as shown in Figures 11A-C) [95]. For elasticity measurement of posterior eye, Qu et al reported the first in vivo quantitative elasticity map of the retina by displacement measurement (ie, the compression approach) in which a difference was demonstrated between healthy and damaged rabbit retina in 2018 [45].…”

Multimodal intravascular imaging technology for characterization of atherosclerosis

“…To address this issue, various intravascular imaging technologiesincluding optical coherence tomography (OCT), ultrasound (US), near-infrared°uorescence (NIRF), photoacoustic (PA), and optical coherence elastography (OCE)have been developed to characterize the thin¯brous cap, lipid pool, localized in°ammation, and biomechanical properties related to atherosclerotic plaques by quantifying the layered architecture, compositional data, and mechanical properties of coronary arteries. 2,[6][7][8][9][10][11][12][13][14][15][16][17]75 Intravascular ultrasound (IVUS) is the most commonly used clinical imaging technique for plaque diagnostics. 18,19 IVUS can provide crosssectional structural images of the coronary vessel with a resolution of 100 m and an imaging depth of 7 mm.…”