Looking Into the Eye Understanding Anatomy, Normal Vision, and Vision Problems By: Deniz Harland
Fact or Fiction? <ul><li>Fact: </li></ul><ul><ul><li>Eating Carrots Will Improve Your Sight </li></ul></ul><ul><ul><li>Looking Straight at the Sun Will Damage Your Sight </li></ul></ul><ul><ul><li>Using Artificial Sweeteners Will Make Your Eyes More Sensitive to Light </li></ul></ul><ul><li>Fiction: </li></ul><ul><ul><li>Reading in the Dark Will Weaken Your Eyesight </li></ul></ul><ul><ul><li>Sitting Too Close to the TV Will Damage Your Vision </li></ul></ul><ul><ul><li>There's Nothing You Can Do to Prevent Vision Loss </li></ul></ul>
Outermost Layer The Sclera maintains the shape of the eye The Cornea is the front sixth of the sclera and is clear . All light must first pass through the cornea when it enters the eye. Extraocular Muscles Sclera Cornea The Extraocular Muscles are attached to the sclera and move the eye
Second Layer The Choroid (or Uveal Tract) is the second layer of the eye . It contains the blood vessels that supply blood to structures of the eye. The Iris is the colored part of the eye . The color is determined by the color of the connective tissue and pigment cells. The iris is an adjustable diaphragm around an opening called the pupil . The Ciliary Body is a muscular area that is attached to the lens. It contracts and relaxes to control the size of the lens for focusing. The Dilator Muscle makes the iris smaller and therefore the pupil larger, allowing more light into the eye. The Sphincter Muscle makes the iris larger and the pupil smaller , allowing less light into the eye. Choroid Ciliary Body Sphincter Muscle Dilator Muscle Iris
Innermost Layer Retina Rod Cells Fovea Centralis Macula Cone Cells The Rod Cells are responsible for vision in low light The Cone Cells are responsible for color vision and detail The Retina is the light-sensing portion of the eye The Macula is in the back of the eye and in the center of the retina The Fovea Centralis is in the center of the macula, contains only cones, and is responsible for seeing fine detail clearly.
Muscles Six muscles attached to the sclera that control the movements of the eye Rotates eye Rotates eye Lowers eye Raises eye Moves eye away from nose Moves eye towards nose Primary Function Inferior oblique Superior oblique Inferior rectus Superior rectus Lateral rectus Medial rectus Muscle
Activity Slide <ul><li>What muscle are you using when you… </li></ul><ul><ul><li>Move eyes towards nose…? </li></ul></ul><ul><ul><li>Move eyes away from nose…? </li></ul></ul><ul><ul><li>___________ raises the eye while the </li></ul></ul><ul><ul><li>___________ lowers the eye </li></ul></ul><ul><li>Which muscles rotate the eyes? </li></ul><ul><ul><li>___________ -and- __________ </li></ul></ul>
Understanding Vision <ul><li>Light enters the eye </li></ul><ul><li>Passes through the cornea, aqueous humor lens, and vitreous humor </li></ul><ul><li>Reaches the retina, where </li></ul><ul><li>rods handle vision in low light and </li></ul><ul><li>cones handle color vision and detail. </li></ul>20/20 Vision If you have 20/20 vision , it means that when you stand 20 feet away from the chart you can see what a "normal" human being can see. 20 feet
Color Vision <ul><li>Cone Pigments: </li></ul><ul><ul><li>color-responsive chemicals in the cones </li></ul></ul><ul><ul><li>very similar to chemicals in the rods </li></ul></ul><ul><ul><li>made up of retinal and photopsins </li></ul></ul><ul><li>The Three Kinds of Pigments: </li></ul><ul><ul><li>Red-sensitive </li></ul></ul><ul><ul><li>Blue-sensitive </li></ul></ul><ul><ul><li>Green-sensitive </li></ul></ul>What pretty colors! Fact: The Human eye can sense almost any gradation of color when red, green, and blue are mixed
Blind Spot Activity Test the presence of the blind spot by 1- Covering your right eye with your hand 2- Staring at the yellow circle as you move closer to the screen Or cover your left eye and stare at the red square as you move. Result: the square (or circle depending on which eye in covered) will disappear
Vision Problems <ul><li>Astigmatism is an uneven curvature of the cornea and causes a distortion in vision. </li></ul><ul><li>Night Blindness is when there is severe vitamin D deficiency which causes levels of light-sensitive molecules to be low </li></ul>
Blindness & Its Beginnings <ul><li>Legal blindness is usually defined as visual acuity less than 20/200 with corrective lenses </li></ul><ul><li>Causes: </li></ul><ul><ul><li>Cataracts - Cloudiness in the lens blocks light from reaching the retina. It becomes more common as we age, but babies can be born with a cataract. Glaucoma - If the aqueous humor does not drain out correctly, then pressure builds up in the eye. Cells and nerve fibers die from the pressure Can be treated with medications and surgery. </li></ul></ul>
Other Vision Problems <ul><li>Macular Degeneration - when the macula deteriorates with age for unknown reasons. This causes loss of central vision. Laser surgery can sometimes help with this condition </li></ul><ul><li>Trauma - Direct trauma or chemical injuries can cause enough damage to the eyes to prevent adequate vision </li></ul><ul><li>Retinitis Pigmentosa – An inherited disease that causes a degeneration of the retina and excess pigment. First causes night blindness and then tunnel vision, often gradually progressing into total blindness. No known treatment </li></ul><ul><li>Trachoma - An infection caused by an organism called Chlamydia trachomatis. A common cause of blindness worldwide but is rare in the United States. Can be treated with antibiotics </li></ul>
Bibliography <ul><li>"The Human Eye." 19 December 2006 02 MAR 2008 <http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/V/Vision.html>. </li></ul><ul><li>"Eye Health." WebMD 01 OCT 2005 02 MAR 2008 <http://www.webmd.com/eye-health/fact-fiction-myths-about-eyes>. </li></ul><ul><ul><li>More information about Fact or Fiction: see this site </li></ul></ul>
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