China 
Africa 
Explore chapters and articles related to this topic
Driver Capabilities in the Resumption of Control
Published in Donald L. Fisher, William J. Horrey, John D. Lee, Michael A. Regan, Handbook of Human Factors for Automated, Connected, and Intelligent Vehicles, 2020
Sherrilene Classen, Liliana Alvarez
Glaucoma refers to a group of degenerative eye diseases that compromise the integrity of the optic nerve, often associated with elevated intraocular pressure (Cohen & Pasquale, 2014). The most common type of glaucoma is open-angle glaucoma, which accounts for nearly 90% of all glaucoma cases (Glaucoma Research Foundation, n.d.). Open-angle glaucoma is a result of a progressive clogging of the eye’s drainage canals, which in turn increases pressure on the optic nerve. This clogging develops in spite of an adequately wide and open angle where the cornea and the iris meet, and the symptoms emerge only after the disease advances (Cohen & Pasquale, 2014). Angle-closure glaucoma, on the other hand, develops when the drainage canals are blocked due to the angle closure between the iris and the cornea. Angle-closure glaucoma develops rapidly and leads to severe noticeable symptoms (See: Aquino et al., 2011). Other types of glaucoma include normal-tension glaucoma, where the optic nerve is damaged in spite of relatively normal intra ocular pressure—the cause of which remains poorly understood (Anderson, 2011), and secondary glaucoma, which results from an injury around the eye that increases pressure on the optic nerve (Papadopoulos, Loh, & Fenerty, 2015). Figure 10.3 illustrates a scene as viewed by a person diagnosed with glaucoma.
Medical and Mathematical Background
Published in Arwa Ahmed Gasm Elseid, Alnazier Osman Mohammed Hamza, Computer-Aided Glaucoma Diagnosis System, 2020
Arwa Ahmed Gasm Elseid, Alnazier Osman Mohammed Hamza
Eye doctors usually use several tests to detect glaucoma. These are usually categorized as functional or image-based assessments. Functional assessment includes measurement of IOP (tonometry) and visual field examination. Image-based evaluation relies on optic nerve head imaging devices to determine optic nerve head structural damage or thinning of the retinal nerve fiber layer (RNFL). Examples of such imaging devices are Retinal Fundus Camera, Heidelberg Retinal Tomography (HRT), and Optical Coherence Tomography (OCT). Nonetheless, most of these methods have their own limitations. Measurement of IOP was reported to have a poor sensitivity of around 50% (Sommer et al., 1991). This is partially due to cases of normal tension glaucoma, where patients have a condition in which optic nerve damage and vision loss have developed even with a normal pressure inside the eye. The visual field examination is often time-consuming and found to be unreliable due to factors such as the patient’s fatigue and learning effects. Image-based evaluation using HRT and OCT are highly costly and are usually only available at tertiary hospitals, thus limiting its outreach.
Use of XyCAM RI for Noninvasive Visualization and Analysis of Retinal Blood Flow Dynamics During Clinical Investigations
Published in Expert Review of Medical Devices, 2021
Delia Cabrera DeBuc, Abhishek Rege, William E. Smiddy
Current treatment strategies of these common conditions are based on initiating treatment only after detection of substantial, irreversible damage has occurred. Earlier stage detection may permit treatment and management of these diseases before clinical signs of damage and, thus, may be highly effective in preventing vision impairment or vision loss in a majority of the cases. The efficacy of advanced functional imaging technologies to screen for early disease requires not only improved accuracy, but also easy-to-use platforms and robust performance in clinical settings. For example, some of the most commonly used clinical diagnostic tools may still be insufficient to accurately diagnose glaucoma. In most glaucoma cases, an increase in intraocular pressure (IOP) leads to decreased retinal blood flow (RBF), causing ischemic damage to retinal ganglion cells and the optic nerve. While IOP is an important diagnostic biomarker for glaucoma, and is accurate for 90% of the patients, its utility is diminished in normal tension glaucoma where the damage is not associated with elevated IOP but rather attributed to reduced or abnormal blood flow in the eye or other factors [15,16]. The methods which rely on anatomical assessment of the retinal nerve fiber layer thickness, such as using optical coherence tomography (OCT), capture evidence at fairly advanced stages, not early enough to prevent damage to the optic nerve [17,18]. Imaging of RBF and optic disc blood flow may, therefore, provide crucial insights for early and more specific diagnoses of diseases such as glaucoma[4].
Swept-source optical coherence tomography imaging of the retinochoroid and beyond
Published in Expert Review of Medical Devices, 2020
Jayesh Vira, Alessandro Marchese, Rohan Bir Singh, Aniruddha Agarwal
SS-OCT can better image the interior details in a case of optic disc melanocytoma (ODM) which, on conventional dye-based angiography systems are blocked due to the dense pigmentation. Features described include an anterior nodularity of the region and a marked posterior optical shadowing ‘comet with a tail.’ On en-face OCT projection, the lesion appears like a ladybug with ‘black dots seen on the round body of the insect.’ Bright hyper-reflective dots may also be seen within the lesion and have been attributed to either densely collected tumor cell aggregates or melanophages. Peripapillary choroidal invasion of the tumor can also be detected as thickening, hyperreflectivity, or hyporeflectivity of the choroid [49]. In the region of the mass, the SS-OCTA was able to pick up a dense vasculature both in the superficial and deep layers of melanocytoma. In a case of ODM with normal-tension glaucoma, the SS-OCTA showed reduced peripapillary perfusion in areas glaucomatous RNFL bundle defects helping differentiate glaucomatous damage from compression by ODM [50].