Noncontact all-optical measurement of corneal elasticity

Abstract

We report on a noninvasive and noncontact all-optical method to measure the elasticity of the cornea. We use a pulsed laser to excite surface acoustic waves (SAW) that propagate on the corneal surface, then use a phase-sensitive optical coherence tomography system to remotely record the SAWs from which the corneal elasticity is estimated. In addition, the system is able to provide real-time tomographic images of the cornea being examined, an important consideration for clinical studies. While precisely maintaining a range of intraocular pressures (IOP), a series of measurements is performed on ex vivo intact primate eyes. The measurement results not only demonstrate the feasibility of the proposed system to remotely measure the corneal elasticity, but also suggest a strong correlation between the corneal stiffness and the true IOP.

Noncontact depth-resolved micro-scale optical coherence elastography of the cornea

“…Compared with the existing OCE methods for corneal biomechanics [45][46][47][48][49], the proposed method has the feature of noncontact depth-resolved detection, which has not been achieved in cornea with OCE before. Also, the loading with a low-pressure short-duration puff of air significantly reduces the safety concerns compared with the use of pulsed laser and acoustic radiation force for the potential clinical practice.…”

“…With static loading of the cornea through a glass window, Ford et al [47] and Nahas et al [38] measured the amplitude of corneal deformation and utilized the mapping of the strain to provide depthresolved elastographic information of the cornea. Based on the detection of the elastic wave propagation inside the cornea, Li et al [48] and Manapuram et al [49] assessed the wave group velocity that can be used to quantitatively estimate the elasticity of the cornea.…”

Quantitative elasticity measurement of urinary bladder wall using laser-induced surface acoustic waves

“…Wang et al was the first to describe the application of laserinduced SAWs to clinical dental disease diagnosis [30,31]. Our group pioneered the use of shaker-and laser-induced SAWs to evaluate the Young's modulus of heterogeneous soft tissue and phantoms [32][33][34][35][36][37]. In the laser-induced SAW method, the deformation experienced by the target sample is less than 1 µm (typically ~100 nm) [37], which ensures linear behavior of the soft tissue.…”

“…Our group pioneered the use of shaker-and laser-induced SAWs to evaluate the Young's modulus of heterogeneous soft tissue and phantoms [32][33][34][35][36][37]. In the laser-induced SAW method, the deformation experienced by the target sample is less than 1 µm (typically ~100 nm) [37], which ensures linear behavior of the soft tissue. Our previous works proved that SAWs can be used to accurately evaluate the mechanical properties of layered viscoelastic soft tissues such as those in the skin, liver, and cornea [32][33][34][35][36][37].…”

“…In the laser-induced SAW method, the deformation experienced by the target sample is less than 1 µm (typically ~100 nm) [37], which ensures linear behavior of the soft tissue. Our previous works proved that SAWs can be used to accurately evaluate the mechanical properties of layered viscoelastic soft tissues such as those in the skin, liver, and cornea [32][33][34][35][36][37]. On the other hand, optical coherence tomography (OCT) is a promising noninvasive, noncontact imaging technique capable of providing microstructural information on tissue with high resolution.…”