Fovea The center of the macula which provides the sharp vision. Iris The colored part of the eye which helps regulate the amount of light entering the eye. When there is bright light, the iris closes the pupil to let in less light. And when there is low light, the iris opens up the pupil to let in more light.
Lens Focuses light rays onto the retina. The lens is transparent, and can be replaced if necessary. Our lens deteriorates as we age, resulting in the need for reading glasses.
Intraocular lenses are used to replace lenses clouded by cataracts. Macula The area in the retina that contains special light-sensitive cells. In the macula these light-sensitive cells allow us to see fine details clearly in the center of our visual field. The deterioration of the macula is a common condition as we get older age related macular degeneration or ARMD.
Optic Nerve A bundle of more than a million nerve fibers carrying visual messages from the retina to the brain. In order to see, we must have light and our eyes must be connected to the brain. Your brain actually controls what you see, since it combines images. The retina sees images upside down but the brain turns images right side up.
The iris regulates the amount of light that enters your eye by adjusting the size of the pupil opening. In bright light, the iris closes or constricts and makes the pupil opening smaller to restrict the amount of light that enters your eye. In dim light, the iris opens or dilates and makes the pupil opening larger to increase the amount of light that enters your eye:. In addition, it is the iris that determines your eye color. People with brown eyes have heavily pigmented irises, while people with blue or lighter-colored eyes have irises with less pigment.
The lens is composed of transparent, flexible tissue and is located directly behind the iris and the pupil.
It is the second part of your eye, after the cornea, that helps to focus light and images on your retina. Because the lens is flexible and elastic, it can change its curved shape to focus on objects and people that are either nearby or at a distance. The ciliary muscles , which are part of the ciliary body , are attached to the lens and contract or release to change the lens shape and curvature. The lens becomes more elongated or stretched to focus on objects that are far away see Figure 2 :.
Over time, the lens loses some of its elasticity and therefore loses some of its ability to focus on near objects. This is called presbyopia and explains why people need reading glasses as they become older.
The choroid is a dark brown membrane that is rich with blood vessels, located between the sclera and the retina. It supplies blood and nutrients to the retina and nourishes all of the other structures within the eye.
The vitreous is the jelly-like substance that fills the inside of the back part of the eye. Over time, the vitreous becomes more liquid and can detach from the back part of the eye, which can create floaters. If you notice new floaters or flashing lights, it is important to see your eye doctor, because a detached vitreous can cause a hole a condition called a macular hole to develop in the retina.
The retina is the light-sensitive tissue that lines the inside surface of the eye, much like wallpaper. Cells in the retina convert incoming light into electrical impulses. Donate now Modern slavery and human trafficking statement Contact Cookies High contrast.
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