The Structure of the Eye:
The human eye is encased in a skull bone and is round. The walls of the eyeball have three layers, namely – the neurosensory inner lining, the central vascular coat and the outer coat of fibers.
Coat with outer straps – It is a thick and strong cover that protects the eyeball and helps maintain its shape. It has two areas – the cornea and the sclera
Sclera – Consists of dense white connective tissue, in which only the white eye is visible, most of which is left around. The white of the eye is made up of fibers of collagen.
Role – To maintain and prevent eye formation.
Cornea – It is an invisible part of the blood vessels of the outer layer with visible fibers and covered with a thin, transparent layer of bound epithelium arteries known as the conjunctiva. It is a continuation of the eyelids.
Role – The cornea also illuminates the light that enters the eye and converts it into a lens.
Middle vascular vein – Consists of three regions – choroid, ciliary body, and iris.
Choroid – The upper extremities are also made of loose, fibrous tissue. It is a continuation of the inner part of the sclera. It cracks nicely over a third of the rear ball and tends to thicken forward, giving it a blue appearance. It contains some colored cells.
Role – Nourishes the retina which gives it oxygen. Colored cells absorb excess light to avoid exposure to the eyeball.
Ciliary body – It is thick and forms the inner part of the choroid. By comparison, it is thinner and more vascular and is made up of ciliary muscles and ciliary processes.
1. Ciliary Muscle – It is a smooth muscle and has two types – circular muscles and joint muscles.
2. Ciliary processes – the inner part of the ciliary body has many tissues known as ciliary processes.
Role – Secretes aqueous humour
Iris – Beautiful, opaque organization with a colorful structure, located at the junction of the sclera and cornea. The color of the iris is given by choroid colored cells. The color varies between black, brown, brown or green. It consists of a reader in the middle, as a hole. The iris has two types of smooth muscles – circular muscles and elastic muscles.
Role – Controls eye size which is why light enters. When the radial muscle contracts, the pupil grows with less light. When the muscle contract is circular, the pupil decreases with a brighter light.
Inner neurosensory coat:
The retina forms the finest internal, neurosensory layer of the eyeball. The surface of the retina interacts with the choroid and the interior interacts with the vitreous humor.
The outer surface has four layers:
Colored layer – Made up of a single layer of cells that contain a dark brown color.
Layers of photoreceptors – Consists of two types of cells – rods and tubes
Rods- Rod shaped and contains a reddish-brown protein known as rhodopsin or visible purple. Contains the content of vitamin A. Rods do not react with color and are sensitive to dim light. They offer vision in the dark, which is why it is known as evening vision or scotopic vision
Cones – Sensitive to colors and bright lights, providing daytime or visual imagery. The pigment found in lump cells is known as iodopsin. Three types of con cells respond to green, red, and blue light. Some colors are detected by a one-time trigger of more than one type of cell. White light sensation is performed when all three types of cells are triggered simultaneously.
Cone cells are not sensitive to low light and therefore in the dark, color cannot be seen.
A layer of bipolar neurons, a layer of ganglionic cells are the two layers. This layer contains the bodies of ganglion cells that form optic nerves.
Blind Spot – The optic nerve exits the brain, the retinal blood vessels enter the brain at a time when the photoreceptor cells are absent, and this is the blind area.
Macula lutea – It is a yellow spot that is simultaneously in a blind spot. It is located directly towards the center of the cornea. It has a central cavity known as the fovea that lacks rods and blood vessels. It has only lump cells and is a very different field of vision.
Lens – Stretchy, transparent and biconvex in the environment found just behind the iris. It is covered with a thin, elastic, transparent membrane known as a lens capsule. The lens is in the right place because of the suspensory ligaments. These lines and lenses separate the eyeball into two chambers known as the water chamber and the vitreous chamber.
Liquid chamber – The space between the cornea and the lens that contains a small liquid fluid known as aqueous humor.
Vitreous chamber – The space between the lens and the retina filled with a clear gel known as vitreous humor.