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Imaging the Living Eye
Published in Margarida M. Barroso, Xavier Intes, In Vivo, 2020
Brian T. Soetikno, Lisa Beckmann, Hao F. Zhang
Since the dawn of photography in the 1800s, scientists and physicians have pursued techniques to capture images from inside the living eye. Capturing the fundus, or the interior surface of the retina, initially proved to be challenging. Indeed, early fundus photographs suffered from motion artifacts, overlapping corneal reflections, and long exposure times (Jackman and Webster, 1886). Since these early explorations, however, significant advances in eye imaging have emerged, owing to innovative modalities, including the fundus camera, scanning laser ophthalmoscope (SLO), and optical coherence tomography (OCT). Of note, OCT has enabled three-dimensional (3D) imaging of the living retina and provided images that closely resembled the quality of ex vivo histology. More recently, techniques such as photoacoustic ophthalmoscopy (PAOM) and adaptive optics (AO) have made an additional impact by providing new optical absorption imaging contrast and aberration correction for much improved spatial resolution, respectively. Each of these technologies has provided new avenues toward better understanding of vision and eye diseases.
Adaptive optics ophthalmoscopes
Published in Pablo Artal, Handbook of Visual Optics, 2017
The fundus camera, introduced in the early twentieth century by the Zeiss company in Germany (Van Cader 1978), essentially combined an ophthalmoscope with a camera and allowed ophthalmologists to image the living human retina. Today, several other modalities, for example, scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT), are also used to routinely image the living retina in clinical practice. Because the optics of the eye also induce higher-order aberrations and the majority of these modalities only correct for defocus, they are limited in their ability to image the finer details of the living retina. Retinal structures such as cones, rods, and the smallest retinal blood vessels (capillaries) cannot be resolved, and significant structural damage has often occurred by the time pathology becomes visible. It is therefore necessary to measure and compensate for both lower- and higher-order aberrations in order to overcome this resolution limit and image the smallest retinal structures that are of the order of a few microns in size. The introduction of adaptive optics (AO) into ophthalmic photography has made this possible.
Visual Inspection of Tissues with Certain Endoscopes and Other Optical Devices
Published in Robert B. Northrop, Non-Invasive Instrumentation and Measurement in Medical Diagnosis, 2017
The ophthalmoscope is a simple optical instrument that permits the NI visualization of the front surface of the eye's retina (also known as the fundus), showing blood vessels, general color, surface smoothness, any tears or detachments, and the condition of the macula, etc. These features are normally viewed by the eye of the examining ophthalmologist, and in modern instruments can also be photographed or recorded as digital color images.
An experimental training support framework for eye fundus examination skill development
Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2019
Minh Nguyen, Alvaro Quevedo-Uribe, Bill Kapralos, Michael Jenkin, Kamen Kanev, Norman Jaimes
Despite the importance of fundoscopy, it is a skill that trainees struggle to learn (Schulz et al. 2016), and competency is difficult to assess since only the examiner can see the fundus (McCarthy et al. 2012). Furthermore, the discrete anatomy of the eye’s intricate oculomotor system is conceptually difficult for novice trainees to grasp, and this can be very problematic given that this group of muscles is one of the most common sites of clinical intervention in the treatment of a variety of eye disorders (Allen et al. 2014). There is a concern regarding the competence and proficiency of medical professionals to properly diagnose the eye fundus (Yusuf et al. 2015). It has been suggested that this low competency and proficiency is due to the limited time dedicated to eye examination training, and the complexity associated with interpreting eye fundus images. Furthermore, as noted by (Yusuf,Salmon and Patel, 2015), the use of the ophthalmoscope is decreasing given the availability of other more modern diagnostic tools. Despite the current decline in ophthalmoscopy skills, the use of the ophthalmoscope still represents a relevant diagnostic technique to identify anomalies in a primary care setting where no advanced equipment may be available. This limited competency and proficiency is not specific to novice trainees, but rather on occasion, expert ophthalmologists have also provided varying diagnoses when presented with identical images of a diseased eye. This has been attributed to a lack of confidence resulting from poor training and lack of skill maintenance (Shuttleworth and Marsh 1997; Mottow-Lippa 2009).
Recent advances in wide field and ultrawide field optical coherence tomography angiography in retinochoroidal pathologies
Published in Expert Review of Medical Devices, 2021
Gagan Kalra, Francesco Pichi, Nitin Kumar Menia, Daraius Shroff, Nopasak Phasukkijwatana, Kanika Aggarwal, Aniruddha Agarwal
In a study by Kolb et al., the authors analyzed 85 degrees FOV, 100 degrees FOV (single scan), and 100 degrees FOV (montage or mosaic) using SS-OCT scans. The authors observed that the 100 degree FOV OCT scans obtained via montage had better quality compared to the single scan while maintaining a better acquisition time [14]. Zhang et al. in their study highlighted the use of wide-field OCTA with motion tracking through an auxiliary real-time line scan ophthalmoscope. This system made it clinically feasible to image functional retinal vasculature in patients with various retinal vascular diseases. A coverage of more than 60 degrees of retina while still maintaining high definition and resolution was achieved [15].