Quantitative assessment of corneal elasticity distribution after FS-LASIK using optical coherence elastography.

Quantifying corneal elasticity after femtosecond laser-assisted in situ keratomileusis (FS-LASIK) procedure plays an important role in improving surgical safety and quality, since some latent complications may occur ascribing to changes in postoperative corneal biomechanics. Nevertheless, it is suggested that current research has been severely constrained due to the lack of an accurate quantification method to obtain postoperative corneal elasticity distribution. In this paper, an acoustic radiation force optical coherence elastography system combined with the improved phase velocity algorithm was utilized to realize elasticity distribution images of the in vivo rabbit cornea after FS-LASIK under various intraocular pressure levels. As a result, elasticity variations within and between the regions of interest could be identified precisely. This is the first time that elasticity imaging of in vivo cornea after FS-LASIK surgery was demonstrated, and the results suggested that this technology may hold promise in further exploring corneal biomechanical properties after refractive surgery.

Two-dimensional elastic distribution imaging of the sclera using acoustic radiation force optical coherence elastography.

The scleral elasticity is closely related with many ocular diseases, but the relevant research is still insufficient. Here, we utilized optical coherence elastography to carefully study biomechanical properties of the sclera at different positions and under different intraocular pressures. Meanwhile, elastic wave velocity and Young's modulus of each position were obtained using a phase velocity algorithm. Accordingly, the two-dimensional elasticity distribution image was achieved by mapping the Young's modulus values to the corresponding structure based on the relationship between the position and its Young's modulus. Therefore, elastic information in regions-of-interest can be read and compared directly from the scleral structure, indicating that our method may be a very useful tool to evaluate the elasticity of sclera and provide intuitive and reliable proof for diagnosis and research.

Quantitative evaluation of biomechanical properties of optic nerve head by using acoustic radiation force optical coherence elastography.

Significance: Previous studies have demonstrated that the biomechanical properties of the optic nerve head (ONH) are associated with a variety of ophthalmic diseases; however, they have not been adequately studied. Aim: We aimed to obtain a two-dimensional (2D) velocity distribution image based on the one-to-one correspondence between velocity values and position using the acoustic radiation force optical coherence elastography (ARF-OCE) technique combined with a 2D phase velocity algorithm. Approach: An ARF-OCE system has the advantages of non-invasive detection, high resolution, high sensitivity, and high-speed imaging for quantifying the biomechanical properties of the ONH at different intraocular pressures (IOPs) and detection directions. The 2D phase velocity algorithm is used to calculate the phase velocity values at each position within the imaging region, and then the 2D velocity distribution image is realized by mapping the velocity values to the corresponding structure based on the one-to-one relationship between velocity and position. The elasticity changes can be read directly according to the quantitative relationship between Lamb wave velocity and Young's modulus. Results: Our quantitative results show that the phase velocity and Young's modulus of the ONH increase by 32.50% and 129.44%, respectively, with increasing IOP, which is in general agreement with the results of previous studies, but they did not produce large fluctuations with the constant change of the ONH direction. These results are consistent with the changes of elastic information in the 2D velocity distribution image. Conclusions: The results suggest that the ARF-OCE technology has great potential in detecting the biomechanical properties of the ONH at different IOPs and directions, and thus may offer the possibility of clinical applications.

Acoustic radiation force optical coherence elastography: A preliminary study on biomechanical properties of trabecular meshwork.

Evaluating biomechanical properties of trabecular meshwork (TM) is of great significance for understanding the mechanism of aqueous humor circulation and its relationship to some eye diseases such as glaucoma; however, there is almost no relevant study due to the lack of clinical measurement tool. In this paper, an acoustic radiation force optical coherence elastography (ARF-OCE) system is developed with the advantages of noninvasive detection, high resolution, high sensitivity, and high-speed imaging, by which elastic modulus of the porcine and human TMs is accurately quantified. As the first OCE imaging of TM, our study demonstrates that ARF-OCE may be an effective approach to advance the research of diseases related to aqueous humor circulation.

Quantification of biomechanical properties of human corneal scar using acoustic radiation force optical coherence elastography.

Biomechanical properties of corneal scar are strongly correlated with many corneal diseases and some types of corneal surgery, however, there is no elasticity information available about corneal scar to date. Here, we proposed an acoustic radiation force optical coherence elastography system to evaluate corneal scar elasticity. Elasticity quantification was first conducted on ex vivo rabbit corneas, and the results validate the efficacy of our system. Then, experiments were performed on an ex vivo human scarred cornea, where the structural features, the elastic wave propagations, and the corresponding Young's modulus of both the scarred region and the normal region were achieved and based on this, 2D spatial distribution of Young's modulus of the scarred cornea was depicted. Up to our knowledge, we realized the first elasticity quantification of corneal scar, which may provide a potent tool to promote clinical research on the disorders and surgery of the cornea.

Quantification of iris elasticity using acoustic radiation force optical coherence elastography.

Careful quantification of the changes in biomechanical properties of the iris can offer insight into the pathophysiology of some ocular diseases. However, to date there has not been much information available regarding this subject because clinical detection for iris elasticity remains challenging. To overcome this limitation, we explore, for the first time to our knowledge, the potential of measuring iris elasticity using acoustic radiation force optical coherence elastography (ARF-OCE). The resulting images and shear wave propagation, as well as the corresponding shear modulus and Young's modulus from ex vivo and in vivo rabbit models confirmed the feasibility of this method. With features of noninvasive imaging, micrometer-scale resolution, high acquisition speed and real-time processing, ARF-OCE is a promising method for reconstruction of iris elasticity and may have great potential to be applied in clinical ophthalmology with further refinement.