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Glaucoma
Published in Ching-Yu Cheng, Tien Yin Wong, Ophthalmic Epidemiology, 2022
Zhi Da Soh, Victor Koh, Ching-Yu Cheng
In clinic, glaucoma is classified according to the configuration of the anterior-chamber angle, and the presence of an identifiable cause (Figure 11.1).4 Glaucoma is classified as open angle in cases where the anterior-chamber angle space is unobstructed, and aqueous humor can flow freely into the trabecular meshwork. In contrast, angle closure is diagnosed when there is a physical impediment to aqueous outflow (e.g., irido-trabecular contact). In open-angle glaucoma, raised IOP is commonly attributed to outflow resistance from within the trabecular meshwork itself. Primary glaucoma is used to describe cases with no discernible cause, and vice versa for secondary. Secondary glaucoma often results as a sequela to neovascularization, uveitis, trauma, or lens-related complications.4 Angle closure is further classified into primary angle closure suspect (PACS), primary angle closure (PAC), and primary angle closure glaucoma (PACG) (Table 11.1).
The Special Sense Organs and Their Disorders
Published in Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss, Understanding Medical Terms, 2020
Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss
Other diseases can also impair vision. Glaucoma is characterized by an increase in intraocular pressure (IOP). Most cases of primary glaucoma are of the open-angle type (primary open-angle glaucoma or POAG), where IOP may fluctuate but the aqueous humor outflow is consistently decreased. Angle-closure or narrow-angle glaucoma occurs when the anterior chamber angle is blocked by the root of the iris, causing severe pain and loss of vision along with the increase in IOP. Complications include cataracts, atrophy (tissue wasting) of the retina and optic nerve, and blindness (amaurosis, typhlosis).
Anterior segment OCT
Published in Pablo Artal, Handbook of Visual Optics, 2017
The measurements of anterior chamber depth and anterior chamber angle are used in diagnosing glaucoma and planning of surgical interventions. OCT goniometry is based on measurements of several parameters characterizing the anterior chamber angle (Karandish et al., 2004, 2006, Radhakrishnan et al., 2005, Meinhardt et al., 2006, Nolan, 2008a, Fukuda et al., 2011, Leung and Weinreb, 2011, Tian et al., 2011, Radhakrishnan and Yarovoy, 2014).
Analyzing Anatomical Factors Contributing to Angle Closure Based on Anterior Segment Optical Coherence Tomography Imaging
Published in Current Eye Research, 2022
Bingsong Wang, Kai Cao, Zhiheng Wang, Ye Zhang, Nathan Congdon, Tao Wang
A crowded anterior chamber angle is caused directly by adjacent anatomic structures in the anterior segment of the eye. As mentioned above, many interrelated parameters are involved in determining angle configuration. Although the relationship of these anatomic parameters has been evaluated, and several predominant parameters have been identified in angle closure, it is still not clear how these parameters work together to determine angle structure. We hypothesize that some parameters might be more essential and indispensable, while others might be contributory. Thus, we can select some key parameters to guide clinical practice. With the introduction of anterior segment optical coherence tomography (AS-OCT), it is now possible to capture in a single image the entire anterior segment of the eye and to elaborate the relationships among biometric parameters more precisely. The aim of the study is to investigate the anatomical factors associated with angle closure using mathematical techniques, elucidating their relationship and identifying the most clinically meaningful parameters for determining angle closure.
Assessment of anterior segment measurements using a high-resolution imaging device
Published in Expert Review of Medical Devices, 2020
Robert Montés-Micó, Pedro Tañá-Rivero, Salvador Aguilar-Córcoles, Ramón Ruíz-Mesa
Specifically, anterior chamber angle (ACA) at 500 and 750 (defined as the perpendicular distance from a point on the posterior corneal surface that is 500 and 750 μm anterior to the scleral spur and the anterior surface of the iris, respectively), scleral spur angle (SSA) at 500 and 750 (defined as the angle measured at the conjunction of the line connecting the scleral spur to the AOD 500 or AOD 750 iris endpoint and the line connecting the scleral spur to the AOD 500 or AOD 750 corneal endpoint, respectively), angle opening distance (AOD) at 500 and 750 (defined as the perpendicular distance from a point on the posterior corneal surface that is 500 or 750 μm anterior to the scleral spur and the anterior surface of the iris, respectively) and trabecular iris space area (TISA) at 500 and 750 (trapezoidal area that is defined by the following boundaries: AOD 500 or AOD 750, the inner corneoscleral wall and the perpendicular distance between the scleral spur and the iris, respectively). Figure 2 was created showing the different angles, distances, and areas.
Combination of Simple Diagnostic Tests to Detect Primary Angle Closure Disease in a Resource-constrained Region
Published in Ophthalmic Epidemiology, 2019
Nikhil S. Choudhari, Ronnie George, Rashima Asokan, Rohit Khanna, Lingam Vijaya, Chandra Sekhar Garudadri
The diagnosis and management of primary angle closure disease is based on the assessment of anterior chamber angle. While gonioscopy is considered to be the reference standard to assess the angle of the anterior chamber, it requires high skill and experience. Moreover, in eyes with narrow angles, the ambient illumination and the amount of indentation on the cornea can adversely affect assessment of the angle.7 Advanced optical-based systems, such as Anterior Segment Optical Coherence Tomography (AS-OCT),8–10 Scheimpflug Photography11,12 and Scanning Peripheral Anterior Chamber Depth Analyzer (SPAC)13–15 are being considered to overcome the limitations of gonioscopy in diagnosing angle closure disease. However, these systems are bulky and expensive, and are not practical for resource-constrained regions.