Which layer dilates the pupil

The slight bulge in the sclera at the front of the eye is a clear, thin, dome-shaped tissue called the cornea.

The middle layer is the choroid. The front of the choroid is the colored part of the eye called the iris. In the center of the iris is a circular hole or opening called the pupil. The inner layer is the retina , which lines the back two-thirds of the eyeball.

The retina consists of two layers: the sensory retina, which contains nerve cells that process visual information and send it to the brain; and the retinal pigment epithelium RPE , which lies between the sensory retina and the wall of the eye. The inside of the eye is divided into three sections called chambers. Anterior chamber: The anterior chamber is the front part of the eye between the cornea and the iris.

The iris controls the amount of light that enters the eye by opening and closing the pupil. The iris uses muscles to change the size of the pupil.

These muscles can control the amount of light entering the eye by making the pupil larger dilated or smaller constricted. Posterior chamber: The posterior chamber is between the iris and lens. The lens is behind the iris and is normally clear. The structures and functions of the eyes are complex. Each eye constantly adjusts the amount of light it lets in, focuses on objects near and far, and produces continuous images that are instantly transmitted to the brain.

The orbit is the bony cavity that contains the eyeball, muscles, nerves, and blood vessels, as well as the structures that produce and drain tears.

Each orbit is a pear-shaped structure that is formed by several bones. The outer covering of the eyeball consists of a relatively tough, white layer called the sclera or white of the eye. Near the front of the eye, in the area protected by the eyelids, the sclera is covered by a thin, transparent membrane conjunctiva , which runs to the edge of the cornea.

The conjunctiva also covers the moist back surface of the eyelids and eyeballs. Light enters the eye through the cornea , the clear, curved layer in front of the iris and pupil.

The cornea serves as a protective covering for the front of the eye and also helps focus light on the retina at the back of the eye. After passing through the cornea, light travels through the pupil the black dot in the middle of the eye. The iris —the circular, colored area of the eye that surrounds the pupil—controls the amount of light that enters the eye.

The iris allows more light into the eye enlarging or dilating the pupil when the environment is dark and allows less light into the eye shrinking or constricting the pupil when the environment is bright.

Thus, the pupil dilates and constricts like the aperture of a camera lens as the amount of light in the immediate surroundings changes.

The size of the pupil is controlled by the action of the pupillary sphincter muscle and dilator muscle. Behind the iris sits the lens. By changing its shape, the lens focuses light onto the retina.

This is the natural lens of the eye. Just as a camera has a lens, so does the eye. This lens is clear for most of our lives, and changes shape as we try to focus on things up close and things in the distance. With some medications or diseases, the ability of our lenses to change shape becomes temporarily or permanently impaired. For example, pregnant women may notice that their glasses prescription changes during pregnancy, and then stabilizes after giving birth.

This is due to hormonal changes that affect the shape of the lens during pregnancy. Overtime, and earlier with some medications like steroids and diseases like diabetes , or lifestyle issues such as smoking or excessive exposure to UV radiation , clouding of our lenses develops which we call " cataract ".

Cataracts blur our vision and can be treated with cataract surgery. This is the muscle that enables the iris to move back and forth to change the shape of the pupil.

It also produces the fluid of the eye called "aqueous". Diode laser is a treatment for glaucoma that targets the ciliary body to decrease the production of aqueous thereby decreasing the build-up of fluid and pressure in the eye.

The vitreous is a clear gel that fills the bulk of the eyeball. It is solid when we are born and is attached to the inside of the eye. As we get older, the vitreous becomes loose, and "floaters" are created. These are just pieces of more solid vitreous, floating in the more liquid vitreous, and creating shadows on the retina.

Sometimes the vitreous falls off the back of the eye abruptly posterior vitreous detachment , and creates sudden floaters and flashing light sensation. The flashing is from the vitreous pulling on the retina. This thin layer of tissue is made up almost entirely of blood vessels.

These blood vessels supply oxygen and nutrients to the outer part of the retina. In short, the choroid is the life source that keeps the retina healthy and functioning. The choroid is part of the uvea , which also consists of the iris and the ciliary body. The iris and ciliary body are located in the front of the eye and work together to dilate and constrict the pupils. The choroid layer begins in the peripheral edges of the eyeball and lines the entire back of it, sandwiched between the sclera and the retina.

Choriocapillaris — Layer made up of capillaries tiny blood vessels that connect arteries to veins. The eyes and clear vision depend on sufficient blood supply in order to function. Providing nutrients for the retina, macula and optic nerve. Absorbing light and limiting reflections within the eye that could harm vision. Choroid eye conditions can develop sporadically, genetically or as a result of eye trauma.