Optical coherence tomography (OCT) is a non-invasive diagnostic method that offers real-time visualization of the layered architecture of the skin in vivo. The 1.7-micron OCT system has been applied in cardiology, gynecology and dermatology, demonstrating an improved penetration depth in contrast to conventional 1.3-micron OCT. To further extend the capability, we developed a 1.7-micron OCT/OCT angiography (OCTA) system that allows for a visualization of both morphology and microvasculature in the deeper layers of the skin. Using this imaging system, we imaged human skin with different benign lesions and described the corresponding features of both structure and vasculature. The significantly improved imaging depth and additional functional information suggest that the 1.7-micron OCTA system has great potential to advance both dermatological clinical and research settings for characterization of benign and cancerous skin lesions.
We characterized the stiffness and anisotropy of the equatorial sclera and its dependence on intraocular pressure (IOP). Porcine eyes were tested using ultrasound elastography under IOP control. Shear waves were induced using a mechanical shaker, and an off-axis 17.8 MHz transducer used to track the wave propagation in the equatorial and anterior-posterior directions. Wave speed was measured and used to estimate directional Young’s moduli. Anisotropy was defined as the ratio of the equatorial moduli to the anterior-posterior moduli. Sclera was stiffer in the equatorial direction, with anisotropy decreasing with IOP, from, 5.1 at 10 mmHg to 3.7 at 30 mmHg.
Most soft tissues, such as cornea and sclera, exhibit mechanical anisotropy. Obtaining the anisotropy properties of the sclera can be helpful in understanding the mechanical properties of the eyes in the development and progression of glaucoma and myopia. In this work, we have demonstrated a method of quantifying the anisotropic Young’s modulus values for sclera, using a confocal Lamb wave based acoustic radiation force optical coherence elastography (ARF-OCE). We have measured mechanical anisotropy in porcine sclera by measuring the Young’s modulus along both the equator direction and anterior to posterior direction. The results demonstrate the Young’s modus in the equator direction is 15-30% higher than that in the anterior to posterior direction.
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