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Conducting Polymers for Ophthalmic Applications
Published in Ram K. Gupta, Conducting Polymers, 2022
The eye can be split into two parts, called the anterior and posterior segments. The anterior segment includes the cornea, the iris, the ciliary body, the conjunctiva, the crystalline lens, and a chamber filled with aqueous humor [5]. The cornea is the outermost surface of the eye and consists of five layers, transparent to allow light refraction and transmission to the retina. In addition, it covers the eye surface to provide a protective layer. The iris is the colored circular part surrounding the pupil. The pupil changes its size in response to light levels, allowing the proper amount of light to reach the retina through muscular contraction and relaxation. The ciliary body produces the aqueous humor that has immunological and nutritional tasks as well as maintaining a 10–21 mmHg intraocular pressure (IOP) in a healthy eye. The conjunctiva is a clear mucous membrane that covers the front of the eye up to the cornea and the inner surfaces of the eyelids, responsible for tear production and preservation of the tear film. The human crystalline lens has a clear and biconvex shape that helps in focusing light onto the retina. The lens is flexible and can vary its shape and focusing power based on the distance between the object and the eye thanks to muscles called zonules.
Imaging the Living Eye
Published in Margarida M. Barroso, Xavier Intes, In Vivo, 2020
Brian T. Soetikno, Lisa Beckmann, Hao F. Zhang
An understanding of the ocular anatomy is required to grasp the principles of ophthalmic imaging. Refractive elements of the eye focus parallel rays of light to the light-sensitive posterior layers of the eye, and, therefore, the optical system of the eye must be considered when designing an ocular imaging system. Figure 14.1a illustrates the human eye, which can be divided into anterior and posterior segments. The anterior segment contains the curved surfaces of the cornea and lens, which focus light onto the retina. In addition, the iris dilates and constricts, controlling the amount of light reaching the retina. The posterior segment consists of the vitreous, retina, choroid, and optic nerve head. Most of the ophthalmic imaging modalities focus on capturing the posterior segment and, more specifically, the retina.
Anterior segment OCT
Published in Pablo Artal, Handbook of Visual Optics, 2017
The human eye is a complex and dynamic optical structure enabling visual perception, that is, conversion of light into electrical signals that are later processed by the brain. Anatomically, the front of the eye constitutes its anterior segment (AS) and includes the elements spanning from the cornea to the posterior surface of the crystalline lens. The main function of the AS of the eye is to perform and control light focusing on the retina since it contains all refracting surfaces leading to the sharp image of the object on the retina. Therefore, from the physical (optical) point of view, the AS of the eye is composed of the optical elements of different refractive properties, thus forming a compound optical system (Atchison and Smith, 2000, Grosvenor, 2007).
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
The assessment of different anterior segment parameters is essential for diagnosis, prevention, and treatment of glaucoma. Gonioscopy, specifically for the angle, has been considered relatively subjective and variable between examiners (requiring the expertise of a trained examiner) [1]. The use of new noninvasive techniques such as Optical Coherence Tomography (OCT) has provided clinicians an in-vivo reproducible objective imaging of different anterior chamber angle structures. High-resolution scans of the anterior segment of the eye allow identification and measurement of some metrics useful for clinical diagnosis. In addition, some of these parameters are necessary for cataract and refractive surgery procedures.