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Michael D Twa, Gongpu Lan, Manmohan Singh, Kirill Larin; In-vivo human corneal elasticity imaging: a phase sensitive optical coherence elastography method. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4324. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Non-invasive high-resolution corneal elasticity assessment is essential for detection and treatment of ocular diseases (e.g. keratoconus, corneal cross-linking, etc.); however, there is no widely accepted standard for in vivo measurements of human corneal elasticity. Because of its high spatio-temporal resolution, phase sensitive optical coherence elastography (PhS-OCE) is an emerging technique that has been previously validated with tissue phantoms, ocular tissues ex vivo, and with animal eyes in situ. Here, we describe a newly developed common-path PhS-OCE imaging method with enhanced phase stability and detection sensitivity, and demonstrate its first use for measurements of sub-micron corneal displacements in human eyes in vivo.
Elastography corneal imaging (Fig. 1a) was performed by combining common-path phase-sensitive OCT imaging and low-force micro-air-pulse tissue stimulation to detect sub-micron corneal tissue displacements. Phase stability of this common-path OCT was measured with a mirror. Tissue excitation (150 µm diameter spot, 20-60 Pa) was applied and the resulting dynamic displacements (pointwise, M-mode) were measured at the corneal apex in two healthy subjects.
Displacement sensitivity for this common path PhS-OCE system was determined by the phase stability (SD=0.24 nm). Corneal displacement increased with increasing force as shown in Fig. 1b. The response to stimulation (median ± IQR) was –0.23±0.02μm (20 Pa), –0.42±0.03μm (40 Pa), and –0.62±0.05μm (60 Pa) respectively. The repeatability of displacement measurements (IQR) ranged from ±0.02 to ±0.05μm.
Sub-micron tissue deformations (–0.2 to –0.8μm) were induced, detected and quantified for the human cornea in vivo with high measurement repeatability. These preliminary results demonstrate the potential for common-path PhS-OCE to resolve subtle variations of corneal stiffness in vivo. Elastography imaging has several possible clinical applications for diagnosis, treatment and detection of disease progression.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Fig. 1. Common-path PhS-OCE (a) enables in vivo corneal elastography measurement for human subjects (b).
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