Method for optical coherence elastography of the cornea

Abstract

Abstract. The material properties of the cornea are important determinants of corneal shape and refractive power. Corneal ectatic diseases, such as keratoconus, are characterized by material property abnormalities, are associated with progressive thinning and distortion of the cornea, and represent a leading indication for corneal transplantation. We describe a corneal elastography technique based on optical coherence tomography (OCT) imaging, in which displacement of intracorneal optical features is tracked with a 2-D cross-correlation algorithm as a step toward nondestructive estimation of local and directional corneal material properties. Phantom experiments are performed to measure the effects of image noise and out-of-plane displacement on effectiveness of displacement tracking and demonstrated accuracy within the tolerance of a micromechanical translation stage. Tissue experiments demonstrate the ability to produce 2-D maps of heterogeneous intracorneal displacement with OCT. The ability of a nondestructive optical method to assess tissue under in situ mechanical conditions with physiologic-range stress levels provides a framework for in vivo quantification of 3-D corneal elastic and viscoelastic resistance, including analogs of shear deformation and Poisson's ratio that may be relevant in the early diagnosis of corneal ectatic disease. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

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.…”

“…Alonso-Caneiro et al [45] and Dorronsoro et al [46] studied the dynamics of the cornea during an air puff, where the temporal characteristics of the corneal response are selected to qualitatively represent the mechanical properties of the whole cornea. 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.…”

Observation of sound-induced corneal vibrational modes by optical coherence tomography

“…Air-puff can be combined with Scheimpflug camera [7] or optical coherence tomography (OCT) [8] for image-based analysis and estimates of corneal viscoelastic parameters [9]. Other emerging techniques for measuring elastic modulus with spatial resolution include supersonic shear imaging [10], optical coherence elastography [11][12][13][14][15][16], and Brillouin microscopy [17].…”

Magnetomotive optical coherence elastography for microrheology of biological tissues

“…[9][10][11][12][13][14][15][16] OCE measurements have been used to assess the biomechanical properties of a wide variety of tissues of interest, such as measuring the stiffness of arteries, 17 different skin layers, 18 tissue engineering constructs, 19 and the cornea. 20,21 OCE requires the application of a mechanical load (stress) on the sample, and by measuring the resulting displacements, the viscoelastic properties of the sample can be extracted. Mechanical stresses are induced in the samples of interest through either dynamic or static methods.…”