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How The Eye Works Insert name/ Practice name/ Logo here if desired.
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Transcript of How The Eye Works Insert name/ Practice name/ Logo here if desired.
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How The Eye Works Insert name/
Practice name/
Logo here if desired
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The healthy eye
• Light rays enter the eye through the clear cornea, pupil and lens.
• These light rays are focused directly onto the retina, the light-sensitive tissue lining the back of the eye.
• The retina converts light rays into impulses; sent through the optic nerve to your brain, where they are recognized as images.
• 70% of the eye's focusing power comes from the cornea.
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Refractive errors
• Inability to see clearly is often caused by refractive error.
• Four types of refractive error: Myopia (nearsightedness) Hyperopia (farsightedness) Astigmatism Presbyopia
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Refractive errors
• In myopia (nearsightedness), the distance between the cornea and the retina may be too long.
• Light rays focus in front of the retina instead of on it.
Myopia
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Refractive errors
• Close objects will look clear, but distant objects will appear blurred.
Myopia, or nearsightedness
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Refractive errors
• In hyperopia (farsightedness), the distance between the cornea and the retina may be too short.
• Light rays are focused behind of the retina instead of on it.
Hyperopia
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Refractive errors
• In adults (but not children), distant objects will look clear, but close objects will appear blurred.
Hyperopia, or farsightedness
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Refractive errors
• In astigmatism, the cornea is curved unevenly—shaped more like a football than a basketball.
• Light passing through the uneven cornea is not properly focused on the retina.
• Distance and close vision may appear blurry.
Astigmatism occurs when light passes through uneven cornea
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Refractive errors
• Presbyopia is a normal condition in which your eyes gradually lose the ability to see things up close.
• When we are young, the lenses in our eyes are flexible and are able to change focus easily between near and far objects.
• At around age 40, this flexibility begins to gradually decrease, making it more difficult to see objects up close.
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Correcting refractive errors
• Eyeglasses are the most common methods of correcting refractive errors; they refocus light rays on the retina.
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Correcting refractive errors
• Contact lenses: float on the tear film that coats the cornea—they refocus light rays on the retina.
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Correcting refractive errors
• Refractive surgery: surgical procedure that alters the shape of your cornea to refocus light rays on the retina to improve vision.
LASIK refractive surgery
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Common causes of vision loss
• Many kinds of eye disease can affect your sight; vision changes are not always evident right away.
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Common causes of vision loss
Age-related macular degeneration (AMD)
• A leading cause of severe vision loss in people over 65 years of age.
• Part of the natural aging process; the macula may lose effectiveness over time, or abnormal blood vessels grow under retina, affecting your central vision.
• Early stage AMD may be hardly noticeable, and may only occur in one eye.
• Symptoms: blurry vision; dark or empty areas in central vision; straight lines look wavy.
• No treatment for “dry” form of AMD; laser or photodynamic therapy (PDT) may treat “wet” form.
With AMD, dark areas may appear in your
central vision
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Common causes of vision loss
Glaucoma
• Leading cause of blindness in the United States, especially for older people.
• Disease of the optic nerve; usually due to increased intraocular pressure (IOP). When optic nerve fibers are damaged, blind spots develop.
• Blind spots usually go undetected until optic nerve is significantly damaged.
• Treatment: eyedrops, laser surgery or conventional surgery may be required, depending on the type of glaucoma and its stage.
• Early detection and treatment are keys to preventing vision loss from glaucoma.
Normal vision
Vision as it might be affected by glaucoma
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Common causes of vision loss
Diabetic retinopathy
• Diabetes Mellitus is the inability of the body to use and store sugar properly, resulting in high blood sugar levels.
• Results in changes in veins, arteries and capillaries in the body, including the eyes. Damage occurs to the fragile blood vessels inside the retina.
• Symptoms: blurred or decreased vision.
• Treatment: usually laser surgery; occasionally conventional surgery.
• You can significantly lower your risk of vision loss by maintaining strict control of your blood sugar level and making frequent visits to your ophthalmologist.
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Common causes of vision loss
Cataract
• Age-related cataract is most common form.
• Eye’s normally clear lens becomes cloudy, preventing light from focusing sharply on the retina.
• Symptoms: blurry vision; glare or sensitivity; poor night vision; yellowing or fading of colors.
• Treatment: surgery that removes the cloudy lens and replaces it with an artificial intraocular lens implant (IOL).
• If cataract symptoms are not adversely affecting your daily activities, you may not need surgery (simply have eyeglass prescription changed as needed).
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Preserve good vision with regular visits to an ophthalmologist or other medical professional
• Infants and young children should visit an ophthalmologist or other medical professional at the following intervals: Newborn to 3 months 6 months to one year 3 to 3 1/2 years
• Other medical professionals include pediatricians, family physicians, nurse practitioners or physician assistants.
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Preserve good vision with regular visits to an ophthalmologist
Visit your ophthalmologist at the following intervals:
• Age 20-29 years: At least once during this period. Those with risk factors for glaucoma (people of African
descent or those who have a family history of glaucoma) should be seen every 3-5 years.
• Age 30-39 years: At least twice during this period. Those with risk factors for glaucoma (people of African
descent or those who have a family history of glaucoma) should be seen every 2-4 years.
• Age 40-64 years: Every 2-4 years.
• Age 65 years or older: Every 1-2 years.