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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.
Electromagnetic Energy and Cataracts
Published in Andrew A. Marino, Modern Bioelectricity, 2020
It is appropriate to define the manner in which the lens is involved with normal visual function. The lens is suspended by circumferentially located zonules attached to the peripherally located ciliary muscle which controls focussing by its state of tonus. The lens lies immediately behind and in the plane of the iris whose posterior surface rests against the suspended lens’s anterior capsular surface. The center of the pupillary aperture in the iris is practically co-axial with the optical axis of the lens.
Repeatability and reproducibility of anterior lens zonule length measurement using ArcScan insight 100 very high-frequency ultrasound
Published in Expert Review of Medical Devices, 2023
Zehui Zhu, Han Zou, Hongzhe Li, Xueer Wu, Yiyi Wang, Zhangliang Li, Yune Zhao
Lens zonules are essential for maintaining the natural position of the crystalline lens. Relaxation or partial dehiscence of zonules causes lens subluxation, tilt, and forward or backward movements. The forward movement of the displaced lens can decrease the anterior chamber depth, resulting in acute secondary angle closure and possibly in pupillary block [14]. Zonular support plays an essential role in cataract surgeries. A lack of zonular support can complicate intraocular procedures, disturb stable postoperative vision, and increase the risk of postoperative complications. It is usually difficult to directly observe the lens zonule during slit lamp examination preoperatively.