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ObjectivesObjectives

By the end of this presentation you will By the end of this presentation you will be able to:be able to: Recognize major components of the eyeRecognize major components of the eye Have a basic understanding of how the eye Have a basic understanding of how the eye

worksworks Understand how eye disease affects the Understand how eye disease affects the

components of the eyecomponents of the eye

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The EyeThe Eye The eye allows us to see The eye allows us to see

and interpret the shapes, and interpret the shapes, colors colors and dimensions of and dimensions of objects in the world by objects in the world by processing the light they processing the light they reflect or emit reflect or emit

The eye is able to see in The eye is able to see in bright or dim light, but it bright or dim light, but it cannot see objects when cannot see objects when light is absentlight is absent

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The EyeThe Eye

When you look at any object When you look at any object

Light waves from that object enter the eye first through the Light waves from that object enter the eye first through the cornea,cornea, which is the clear dome at the front of the eye which is the clear dome at the front of the eye

Light waves progress through the Light waves progress through the pupilpupil, the circular , the circular opening in the center of the coloredopening in the center of the colored irisiris

Immediately behind the iris (and pupil) is the Immediately behind the iris (and pupil) is the crystalline crystalline lens,lens, and light passes through that also and light passes through that also

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The EyeThe Eye Light waves are bent (converged) first by the cornea, then Light waves are bent (converged) first by the cornea, then

even more so by the crystalline lens, to a even more so by the crystalline lens, to a nodalnodal pointpoint which which is immediately behind the lensis immediately behind the lens

At the nodal point, the light waves (image) become reversed At the nodal point, the light waves (image) become reversed (turned backwards) and inverted (turned upside down)(turned backwards) and inverted (turned upside down)

Light waves continue through the Light waves continue through the vitreous humorvitreous humor, the clear , the clear gel that makes up about 80% of the eye’s volume, and then gel that makes up about 80% of the eye’s volume, and then back to a clear focus on the back to a clear focus on the retinaretina behind the vitreous behind the vitreous

The small, central area of the retina is the The small, central area of the retina is the maculamacula; it ; it provides the best vision of any location in the retinaprovides the best vision of any location in the retina

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The EyeThe Eye

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The EyeThe Eye The The light impulses are changed into electrical light impulses are changed into electrical

signals,signals, then sent through the then sent through the optic nerve optic nerve along along the the visual pathway visual pathway to the to the occipital cortex,occipital cortex, or or posterior (back), of the brainposterior (back), of the brain

This is where the electrical signals are seen by This is where the electrical signals are seen by the brain as a visual imagethe brain as a visual image

When light entering the eye is bright enough, the When light entering the eye is bright enough, the pupils will get smaller (constrict) due to pupils will get smaller (constrict) due to pupillary pupillary light responselight response

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The EyeThe Eye

Extraocular MusclesExtraocular Muscles

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The EyeThe Eye Cardinal positions of gazeCardinal positions of gaze

Up/rightUp/right Up/leftUp/left RightRight LeftLeft Down/rightDown/right Down/leftDown/left

In each position of gaze, one muscle of each eye is the In each position of gaze, one muscle of each eye is the primary mover of that eye, and is “yoked” to the primary primary mover of that eye, and is “yoked” to the primary mover of the other eyemover of the other eye

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The EyeThe EyeStrabismus, (cont’d)Strabismus, (cont’d)With strabismus, while one eye is fixating on a particular With strabismus, while one eye is fixating on a particular object, the other eye is turned in another direction, either object, the other eye is turned in another direction, either inward (cross-eyed), outward (wall-eyed), upward, or inward (cross-eyed), outward (wall-eyed), upward, or downwarddownward

As a result, the person either experiences “diplopia” As a result, the person either experiences “diplopia” (double vision) or (double vision) or the brain learns to turn off (suppress) the image of the the brain learns to turn off (suppress) the image of the strabismic eye to maintain single visionstrabismic eye to maintain single vision

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The EyeThe Eye

Hyperopia

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When the cornea is oblong shaped, it When the cornea is oblong shaped, it causes light rays to focus on two different causes light rays to focus on two different points on the retina, instead of just one. points on the retina, instead of just one. As a result, people with significant As a result, people with significant astigmatism may have distorted or blurry astigmatism may have distorted or blurry vision. vision.

AstigmatismAstigmatism Unequal curvatures Unequal curvatures

in cornea & lensin cornea & lens

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The EyeThe EyeMiscellaneous tidbits about the eyes Miscellaneous tidbits about the eyes

A newborn’s eyeball is about 18 millimeters in A newborn’s eyeball is about 18 millimeters in diameter, from front to back. It grows gradually diameter, from front to back. It grows gradually to a length of approximately 24-25 millimeters to a length of approximately 24-25 millimeters (about 1”), or just smaller than a 1 1/2” ping (about 1”), or just smaller than a 1 1/2” ping pong ball!pong ball!

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Diseases of the EyeDiseases of the EyeDiabetic RetinopathyDiabetic RetinopathyThis is a complication of diabetes in which This is a complication of diabetes in which long-term exposure to high glucose levels in long-term exposure to high glucose levels in the blood has damaged retinal blood the blood has damaged retinal blood vessels. vessels. This results in new growth of abnormal This results in new growth of abnormal blood vessels, fluid buildup in the macula blood vessels, fluid buildup in the macula (fovea), inadequate blood supply to the (fovea), inadequate blood supply to the retina and possibly blood and fluid leakage retina and possibly blood and fluid leakage into the retina and the vitreous bodyinto the retina and the vitreous body

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Diseases of the EyeDiseases of the Eye A A cataractcataract is a clouding of the eye's natural lens, which is a clouding of the eye's natural lens, which

lies behind the iris and the pupil lies behind the iris and the pupil

The lens is mostly made of water and protein. The lens is mostly made of water and protein. Protein may clump together and cloudProtein may clump together and cloud This is a cataract, and over time, it may grow larger and This is a cataract, and over time, it may grow larger and

cloud more of the lens, making it harder to seecloud more of the lens, making it harder to see

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Diseases of the EyeDiseases of the Eye

Researchers are identifying factors that may Researchers are identifying factors that may cause cataracts such as:cause cataracts such as: People with diabetesPeople with diabetes Users of steroids, diuretics, and major Users of steroids, diuretics, and major

tranquilizerstranquilizers Users of a lot of saltUsers of a lot of salt Cigarette smokeCigarette smoke Air pollutionAir pollution Heavy alcohol consumptionHeavy alcohol consumption

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Diseases of the EyeDiseases of the EyeGlaucomaGlaucoma Glaucoma represents injury to the optic nerve Glaucoma represents injury to the optic nerve

secondary to elevated pressure inside the eye. secondary to elevated pressure inside the eye.

                           

  Conventional surgery to treat glaucoma makes a new opening in the meshwork. This new opening helps fluid to leave the eye and lowers intraocular pressure.

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The EyeThe EyeResources:Resources:

http://www.cms.hhs.gov/MLNProducts/65_ophthalmology.asphttp://www.cms.hhs.gov/MLNProducts/Downloads/

internet_only_manuals.pdfInternet only manuals, coding

http://www.visionchannel.net/diabeticretinopathy/ Great website for information

http://www.bertscope.com/Literature/Lit_Requests/info_poster.htmlFree eye posters and online stuff

http://www.optima-hyper.com/eyetests/fitness.htmOptima’s Eye Fitness Tests