Successive diffraction model based on Fourier optics as a tool for the studies of light interaction with arbitrary ultrasonic field

In this paper we presented theoretical predictions of light diffraction by complex acoustic fields such as: two adjacent and superposed ultrasonic beams or ultrasound of cylindrical symmetry. The numerical calculations of light intensity of diffraction orders were performed by means of two methods: Nth Order Approximation (NOA) and Successive Diffraction Model (SDM) based on Fourier optics. The latter technique involves dividing the ultrasonic field into several adjacent sections provided that in each section the interaction of light and ultrasound is considered to fulfill Raman-Nath approximation. Propagation of light inside and behind the region with ultrasonic wave was described within the formalism of Fourier optics so that only both transfer and transmission functions had to be appropriately defined. It was revealed that SDM method based on Fourier optics might be applied in the studies of acousto-optic interaction in the cases of complex ultrasonic fields

Acousto-optic lens based on interaction of narrow laser beam with cylindrical ultrasound

Experimental studies of narrow light beam interaction with cylindrical standing ultrasonic wave are presented. As the focusing and defocusing effects are observed, the considered arrangement appears to be an acousto-optic lens. The proposed system acts as an equivalent optical spherical lens whose focal length changes periodically. Additionally, the system based on cylindrical ultrasound serves as an efficient laser light modulator with the rise time of 100 ns. The parameters of both considered modalities (lens and modulator) can be easily controlled

Simultaneously measuring ocular aberration and anterior segment biometry during accommodation

In the human eye, accommodation is essential for functional vision. However, the mechanisms regulating accommodation and the ocular parameters affecting aberrations remain to be explored. In order to measure the alterations of ocular aberration and crystalline lens biometry during dynamic accommodative stimuli, we designed an optical coherence tomography with ultra-long penetration depth (UL-OCT) combined with a Shack–Hartmann wavefront sensor (SHWFS). This integrated set up measures human eye's anterior segment as well as monochromatic high-order aberrations (HOAs) with 6 μm resolution and (1/20) λ accuracy. A total of 10 healthy volunteers without ocular diseases were examined. Upon exposure to accommodative stimuli, the wavefront aberrations became larger. Among the anterior segment biometry, the anterior crystalline lens demonstrated significant curvature during accommodation and was the major cause of high-order aberration. These findings suggest that the front surface of the crystalline lens can significantly affect variation among aberrations, which is a key factor underlying the quality of human vision

In vivo SS-OCT imaging of crystalline lens sutures

©. This manuscript version is made available under the CC-BY 4.0 license http://creativecommons.org/licenses/by /4.0/ This document is the Published Manuscript version of a Published Work that appeared in final form in [Biomedical Optics Express]. To access the final edited and published work see[https://doi.org/10.1364/BOE.401254

Processing-Aware Real-Time Rendering for Optimized Tissue Visualization in Intraoperative 4D OCT

Intraoperative Optical Coherence Tomography (iOCT) has advanced in recent years to provide real-time high resolution volumetric imaging for ophthalmic surgery. It enables real-time 3D feedback during precise surgical maneuvers. Intraoperative 4D OCT generally exhibits lower signal-to-noise ratio compared to diagnostic OCT and visualization is complicated by instrument shadows occluding retinal tissue. Additional constraints of processing data rates upwards of 6GB/s create unique challenges for advanced visualization of 4D OCT. Prior approaches for real-time 4D iOCT rendering have been limited to applying simple denoising filters and colorization to improve visualization. We present a novel real-time rendering pipeline that provides enhanced intraoperative visualization and is specifically designed for the high data rates of 4D iOCT. We decompose the volume into a static part consisting of the retinal tissue and a dynamic part including the instrument. Aligning the static parts over time allows temporal compounding of these structures for improved image quality. We employ a translational motion model and use axial projection images to reduce the dimensionality of the alignment. A model-based instrument segmentation on the projections discriminates static from dynamic parts and is used to exclude instruments from the compounding. Our real-time rendering method combines the compounded static information with the latest iOCT data to provide a visualization which compensates instrument shadows and improves instrument visibility. We evaluate the individual parts of our pipeline on pre-recorded OCT volumes and demonstrate the effectiveness of our method on a recorded volume sequence with a moving retinal forceps

Wavefront Derived Refraction and Full Eye Biometry in Pseudophakic Eyes

To assess wavefront derived refraction and full eye biometry including ciliary muscle dimension and full eye axial geometry in pseudophakic eyes using spectral domain OCT equipped with a Shack-Hartmann wavefront sensor.Twenty-eight adult subjects (32 pseudophakic eyes) having recently undergone cataract surgery were enrolled in this study. A custom system combining two optical coherence tomography systems with a Shack-Hartmann wavefront sensor was constructed to image and monitor changes in whole eye biometry, the ciliary muscle and ocular aberration in the pseudophakic eye. A Badal optical channel and a visual target aligning with the wavefront sensor were incorporated into the system for measuring the wavefront-derived refraction. The imaging acquisition was performed twice. The coefficients of repeatability (CoR) and intraclass correlation coefficient (ICC) were calculated.Images were acquired and processed successfully in all patients. No significant difference was detected between repeated measurements of ciliary muscle dimension, full-eye biometry or defocus aberration. The CoR of full-eye biometry ranged from 0.36% to 3.04% and the ICC ranged from 0.981 to 0.999. The CoR for ciliary muscle dimensions ranged from 12.2% to 41.6% and the ICC ranged from 0.767 to 0.919. The defocus aberrations of the two measurements were 0.443 ± 0.534 D and 0.447 ± 0.586 D and the ICC was 0.951.The combined system is capable of measuring full eye biometry and refraction with good repeatability. The system is suitable for future investigation of pseudoaccommodation in the pseudophakic eye