Eye Tumors
Dongyou Liu in Tumors and Cancers, 2017
The eyeball (globe) is mostly filled with a jelly-like material called vitreous humor, and comprises three main layers: the sclera, the uvea, and the retina. The sclera is the tough, white, outer wall of the eyeball. In the front of the eye it is continuous with the cornea, which is clear to let light through. The uvea is the middle layer of the eyeball that nourishes the eye. It is where most melanomas of the eye develop. The uvea has three main parts: the iris, the choroid, and the ciliary body. The iris is the colored part of the eye (blue or brown) surrounding the pupil. The choroid is a thin, pigmented layer (consisting of connective tissue and melanocytes) underneath the retina. The ciliary body contains the muscular tissue that produces aqueous humor—a clear fluid—in the front of the eye between the cornea and the lens and also helps the eye focus. The retina is a thin-layered structure that lines the eyeball. It contains specialized nerve cells that are sensitive to light as well as blood vessels.
Retinal image enhancement and analysis for diabetic retinopathy assessment
Ahmad Fadzil Mohamad Hani, Dileep Kumar in Optical Imaging for Biomedical and Clinical Applications, 2017
The choroid is a layer of blood vessels that supplies oxygen and nutrients to the outer layers of the retina. The innermost choroid, called the choriocapillaris, is a dense net of flattened capillaries that forms a blood-filled shell lying parallel to the basal side of the RPE. Bruch's membrane separates the blood vessels of the choroid from the RPE layer. The rest of the choroid is filled with larger blood vessels and melanin-containing melanocytes. The melanin content of the RPE varies among individuals. However, only the melanin content of the choroid depends on skin pigmentation. The final layer of significance is the sclera, the fibrous, thick, white outer covering of the eye. Therefore, a reflectance of the fundus can be understood as a ratio of a total amount of reflected light to the total incident light propagating through several fundus layers. Figure 5.6 depicts a model of ocular fundus showing possible pathways of the remitted light.
The uveal tract
Mary E. Shaw, Agnes Lee in Ophthalmic Nursing, 2018
The choroid lies between the sclera and retina and extends from the optic nerve forward to the ora serrata where it joins the ciliary body. The choroid is composed of four layers: The suprachoroid, containing pigment cells, elastic tissue and collagen.The vascular layer, comprising large and small blood vessels, with pigment cells contained in the stroma surrounding the vessels; the large vessels are mainly veins.The choriocapillaries, comprising fenestrated capillary vessels.Bruch’s membrane, which is a barrier with fenestrations which allow nutrients through to the underlying retina; it is also a supportive membrane.
Does using topical latanoprost affect subfoveal choroidal thickness?
Published in Cutaneous and Ocular Toxicology, 2019
Zeynep Duru, Cemal Özsaygılı, Döndü Melek Ulusoy, Atılım Armağan Demirtaş, Ayşe Çiçek, Necati Duru
Choroid is the vascular layer of the eye containing connective tissue and situated between the retina and the sclera. Main functions of the choroid are to nourish the outer layers of the retina, to regulate retinal heat, to absorb excess light via pigment, and to assist in the control of IOP19,20. It is also part of the uveoscleral outflow pathway, which passes from the anterior chamber to the ciliary muscle before proceeding to the suprachoroidal space adjacent to the choroid21,22. By enhancing uveoscleral outflow, PGAs reduce IOP and may also affect vascular permeability by mimicking vascular endothelial growth factor and vascular permeability factor. The metabolic products of arachidonic acid, PGAs are the most extensively studied chemical transmitters that contribute to general edema in systemic tissues, including eye tissue23–25. Considering all of the above, we hypothesized that therapy with a particular PGA, latanoprost, can affect choroidal thickness.
Use of choroidal vascularity index for choroidal structural evaluation in smokers: an optical coherence tomography study
Published in Cutaneous and Ocular Toxicology, 2020
Nurullah Koçak, Volkan Yeter, Mustafa Subaşı, Özlem Eşki Yücel, Ertuğrul Can
The choroid is a densely vascularised structure contributing to the supply of oxygen and other nutrients to the retina. It is one of the body tissues with the highest blood flow and plays a key role in the pathophysiology of many chorioretinal diseases7 .With the improvements of optical coherence tomography (OCT) and its application for enhanced depth imaging (EDI), researchers have been able to accurately evaluate choroidal tissue in vivo in a non-invasive manner. Many of these studies have primarily assessed choroidal thickness (CT) as a parameter to represent the state of the choroid. The effect of smoking on CT has been investigated in several studies2,8–10. CT was among the first surrogate markers proposed; however, CT is influenced by multiple factors, including age, gender, systolic blood pressure, and refractive error11.
Sex-Dependent Choroidal Thickness Differences in Healthy Adults: A Study Based on Original and Synthesized Data
Published in Current Eye Research, 2018
Wei Wang, Miao He, Xingwu Zhong
Since the first report on choroidal imaging in vivo using optical coherence tomography (OCT), an increasing number of studies have measured choroidal thickness (CT) in normal and diseased eyes.1 As a highly vascular structure, the choroid supplies oxygen and nutrients to the outer layer of the retina and the retinal pigment epithelium. An abnormal choroid was related to the pathogenesis of myopia as well as certain retinal and choroidal diseases.1,2 For example, central serous chorioretinopathy (CSC) is associated with an abnormally thick choroid.3 In contrast, an abnormally thin choroid is found in eyes with myopia, idiopathic macular hole (IMH), and age-related macular degeneration (AMD).4–6 The increased CT in patients with CSC has been linked to hyperperfusion, hyperpermeability, and increased osmotic pressure in the choroidal vasculature.7 Likewise, it was indicated that the thin choroid in eyes with AMD involved all of choroidal vascular layers and affected the risk of progression.8 The choroid in vivo has a variable thickness and is regulated by various factors, such as age, axial length (AL), cerebrospinal fluid pressure, menstrual cycle, time of day, and body position.9–13 The Beijing Eye Study found that subfoveal CT decreased by 4 µm per year of age and by 0.46 per mm increase in AL.13
Related Knowledge Centers
- Uvea
- Blood Vessel
- Eye
- Connective Tissue
- Retina
- Sclera
- Oxygen
- Ciliary Body
- Iris
- Sattler'S Layer