THE HUMAN EYE Hailey Pizarro, Marcela Surita, Mikayla Mayo, Jaquan Hemphill, Alexa Bordelon, Emily Roberts, & Baile Jones

The Pupil The pupil is the opening in the center of the iris. The size of the pupil is determined by the amount of light entering the eye. It is controlled by the dilator and sphincter muscles of the iris.

When in a dark environment, your pupil is large, or dilated. This is to let your eye let in more light so you can see more. When in a light environment, your pupil is small or constricted. This is to constrict light that is let in to protect your eye.

Unequal pupils are called anisocoria. This can be caused my multiple things such as aneurysms, bleeding in the skull, brain tumors or abscess, or pressure caused by glaucoma.

The Fovea The fovea is the center most part of the macula. It is responsible for central, sharpest vision and details such as reading, watching TV, and driving.

The fovea has no blood vessels. Instead, it contains cones and rods.

The Cornea The cornea is the clear part of the eye covering the iris and pupil. It lets light into the eye, permitting sight.

Corneal Layers

Aqueous Humor clear fluid in the front of the eye between the cornea and the iris, that provides nutrients to the cornea and the lens. The fluid is produced by the ciliary body. Glaucoma causes a difficulty in draining the fluid, and intraocular pressure builds up. The result is damaged to the optic nerve and loss of vision.

Anterior Chamber The anterior chamber is the part of the eye behind the cornea and in front of the iris and lens. The aqueous Humor is what fills the anterior Chamber

Optic Nerve Also called the second cranial nerve, the optic nerve carries electrical impulses from photoreceptor cells (rod and cones) in the retina to the visual cortex in the brain. It is responsible for transferring visual information from the retina to the vision centers of the brain.

Optic Nerve Head Also called the optic disk, the optic nerve head is the circular area where the optic nerve centers the retina, and the location of the eye’s blind spot.

Vitreous body The vitreous body is the part of the eye between the lens and the retina containing a clear jell called the vitreous humor.

Retina The retina is a thin layer of tissue that lines the back of the eye on the inside. It is located near the optical nerve. Its purpose is to receive light focused from the lens, the retina converts light into neural signals, and sends these signals on the brain. Photoreceptors cells process light, they are light sensitive cells that detect light-intensity and color.

Processes pictures from the focuses light and brain is left to decide what the picture is. Damage to the retina can cause blindness. Retinal detachment- retina is abnormally moved from original position and can prevent the processing of light or receiving light, prevents the brain from receiving information causing blindness.

Sclera Commonly known as the white part of the eye Forms the supporting wall of the eyeball Covered by a conjunctiva, a clear mucus membrane that helps lubricate the eye Thickest in the area surrounding the optic nerve 3 divisions -Episclera: loose connective tissue -beneath the conjunctive: sclera proper, dense white tissue that gives the area color -Lumina fusca: innermost zone made up of elastic fibers

Abnormalities: -Melanosis- excess deposits of melanin on the surface, can be inflamed and uncomfortable -Coloboma- notching and bulging of the sclera -Ectasia- a thinning and bulging of the sclera Treatments: unavailable or unpractical.

Macula The macula is the small area on the retina. It is responsible for seeing straight in front of us. It is the center of our vision field. Light entering the eye is imaged on the retina at the back of the eye. This is the part of the eye that we use to read and see fine detail. The macula consists of several layers of tiny cells.

Small area on the retina Responsible for seeing straight in front of us Center of our vision field Light entering the eye is imaged on the retina at the back of the eye. This is the part of the eye that we use to read and see fine detail.

Iris The iris is a thin, circular structure in the eye. It’s responsible for controlling the diameter and size of the pupil and thus the amount of light reaching the retina. The color of the iris gives the eye its color.

Eye Color It all depends on the genetic material each of the parents have. Usually if you have more melanin, you will have darker colored eyes; if you have less melanin in your body, you will have lighter colored eyes.

Lens The crystalline lens is a transparent structure in the eye that, along with the cornea, helps refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at different distances.

Posterior Chamber The posterior chambers is the space in the eye behind the iris and in front of the lens. It’s filled with a watery fluid known as aqueous humor.

Nearsightedness : visual abnormality in which the resting eye focuses the image of a distant object as a point in front of the retina, resulting in a blurred image -If the eye is to long, light is focused before it reaches the retina, causing nearsightedness -The lens is too steeply curved in relation to the length of the eye and the curvature of the cornea - Image focused in front of the retina

Farsightedness : refractive error or abnormality in which the cornea and lens of the eye focus the image of the visual field at an imaginary point behind the retina (the light sensitive layer of tissue lining the back sides of the eye ) -the lens is too flat, it cause farsightedness

Astigmatism (eye Disorder)- nonuniform curvature of the cornea ( the transparent, dome-shaped tissue located in front of the iris and pupil) that causes the eye to focus images at different distances, depending on the orientation of light as it strikes the cornea - The cornea is not perfectly spherical the image is refracted or focused irregularly

The medial rectus muscle is a muscle in the orbit. As with most of the muscles of the orbit, it is innervated by the inferior division of the oculomotor nerve (Cranial Nerve III). This muscle shares an origin with several other extrinsic eye muscles, the annulus tendineus, or common tendon.

The lateral rectus muscle is a muscle in the orbit. It is one of six extraocular muscles that control the movements of the eye (abduction in this case). Its function is to bring the pupil away from the midline of the body.

The Choroid- Located between the retinal pigment epithelium and the back wall of the eye, the choroid carries nutrients to the retina and the retinal pigment epithelium. The choroid is made up of melanin, which absorbs any extraneous light that may interfere with the image the eye is sending to the brain.

Ciliary body- Releases a transparent liquid (called the aqueous humor) within the eye. The ciliary body also contains the ciliary muscle, which changes the shape of the lens when your eye focus on something. The total process is called accommodation.

Conjunctive and Lacrimal Glands- The conjunctiva is a mucus layer that keeps the eye moist. It covers the sclera and the inner surfaces of the eyelids. Infections in this area are commonly known as “Pink Eye.” Lacrimal glands, which produce tears, are found on the outer part of each eye.