What Is an Iridology Chart?

Oblate circular membrane in the middle layer of the eyeball wall. Located between the cornea and the lens, it can be seen through the cornea, commonly known as "black eyeball". There is a small circular hole in the center, called the pupil, from which light enters the eye. Iris is mainly composed of connective tissue, which contains pigment, blood vessels, and smooth muscle. The color of the iris varies depending on the amount and distribution of the pigment, and there are generally black, blue, gray, and brown.

Oblate circular membrane in the middle layer of the eyeball wall. Located between the cornea and the lens, it can be seen through the cornea, commonly known as "black eyeball". There is a small circular hole in the center, called the pupil, from which light enters the eye. Iris is mainly composed of connective tissue, which contains pigment, blood vessels, and smooth muscle. The color of the iris varies depending on the amount and distribution of the pigment, and there are generally black, blue, gray, and brown.

Chinese name

Iris

Location

The middle part of the eyeball

Nature

Human tissue

Affiliation

eyeball

Iris Overview

Inside the iris, there are smooth muscles arranged around the pupil, called the pupil shrinking muscle (pupil sphincter), and smooth muscles arranged radially from the periphery of the pupil, called mydriasis (pupil dilatator). The former is dominated by parasympathetic nerves, and the latter is dominated by sympathetic nerves. When the strong light illuminates the eye, the pupil sphincter contracts, restricting light entry; when the light is weak, the pupil opens the great muscle to enlarge the pupil, increasing the light entry. Normal pupil size is also related to many factors such as age and refractive status. The pupils of infants under 1 year of age have the smallest pupils, which gradually increase afterwards, and then gradually decrease after puberty. Myopia has larger pupils than farsighted eyes. When a person is in pain or panic, their pupils dilate, and when they sleep, they dilate.

Iris Anatomy Explanation

The foremost part of the middle membrane of the eyeball, located between the cornea and the lens, divides its cavity into a disc-shaped anterior chamber and posterior chamber iris, with a circular hole in the center, called the pupil. There are two kinds of smooth muscle fibers in the iris tissue around the pupil: one is radially arranged to the periphery of the iris, which is called dila-tor pupillae, which is dominated by sympathetic nerve fibers. When shrinking, the pupil is enlarged and more Weak light absorption; the other is around the pupil, called the pupillary sphincter (sphincter pupillae), is dominated by parasympathetic nerve fibers in the oculomotor nerve, shrinks the pupil during contraction to reduce strong light stimulation. The iris inner epithelial cells contain melanocytes. Due to their number and distribution, human irises appear in various colors such as black, blue or gray.

Also known as iridescent. It is the uveal tissue located in the foremost part of the eye. It is developed from the neuroectodermal and anterior mesodermal tissues in the anterior segment of the optic cup. Its starting point is continuous with the leading edge of the ciliary body, extending to the center to the free edge in front of the lens, becoming an important diaphragm that separates the anterior and posterior chambers of the eyeball. A circular hole (or approximately a circle) at the center or slightly nasal side is called a pupil, and has the function of adjusting the brightness of the light into the eye by adapting to the intensity of external light. The iris has front and back sides, and the front is divided into the pupil of the iris and the ciliary part of the iris. The root of the iris is attached to the center of the front of the ciliary body and forms a part of the posterior wall of the anterior chamber angle. Therefore, the forward and backward movement of the iris root position will directly affect the width of the chamber angle. The thickness of the iris varies, and the root is thin (so the root of the iris often breaks due to eye contusion), and gradually thickens inward until the iris ring is the thickest part of the iris, about 0.5 mm (due to the existence of the pupil sphincter). Therefore), the pupil edge becomes thinner inward. The color of the iris mainly depends on the amount of pigment in the parenchyma of the iris, and it is related to the race. European and American people lack the pigment cells in the parenchyma of the iris, while the pigment epithelium cells behind the iris are normal in pigment, and the iris is blue. The iris parenchyma and pigment epithelium of patients with albinism lack pigment cells and appear pink due to the reflection of the fundus. The iris in our country is rich in pigment, but it is tan. Histologically, the iris can be divided into six layers from front to back: endothelial cell layer, anterior boundary membrane, parenchymal layer, muscle layer, pigment epithelium layer and inner boundary membrane layer. From the perspective of embryology, the anterior iris layer is the uveal layer, which originates from the mesoderm tissue, including the endothelial cell layer, the anterior boundary layer, and the vascular layer (anterior and posterior leaves); the posterior layer of the iris is the omental portion and originates. In the neuroectodermal tissue, including the muscular layer (sphincter and dilated muscle), pigment epithelium and inner limiting membrane layer (some people think that this layer does not exist).