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Keloysius Mak

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Keloysius Mak. Blurred truth about glasses. Non-Myopic Eye. Light converges on the retina, producing a clear and sharp image. Myopic Eye. Light converges before the retina, thus the image formed on the retina is blurred. Myopic Eye. - PowerPoint PPT Presentation


Page 1: Blurred truth about glasses

Keloysius Mak

Page 2: Blurred truth about glasses

Non-Myopic Eye Light converges on the retina, producing

a clear and sharp image

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Myopic Eye Light converges before the retina, thus

the image formed on the retina is blurred

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Myopic Eye If the cornea is too curved, or if the

eyeball too broad, light rays from distant objects converge in front of the retina. This makes objects seem fuzzy or blurred.

Nearby objects don't look blurred because the light rays enter the eye at a slight angle. This means they focus on the retina properly.

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What can be done? Glasses LASIK

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Glasses For nearsightedness, the glasses offer a

concave lens that bends light rays outward, which normalizes the eyeball.

For farsightedness, the glasses use a convex lens that bends the light inward before it reaches the eye's lens, thereby correcting vision.

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LASIK procedure The patient receives topical anesthesia, and if desired a

mild sedative - however, the patient is awake during the procedure.

1. Cleansing of the eyelid area, then paper taping the eyelashes to prevent infection.

2. A portable device called a speculum is positioned in the eye to prevent blinking. A suction ring is then placed on the eye, and a momentary blackness occurs.

3. An instrument called a microkeratome glides across the top layer of the cornea, making a thin incision - and creating a flap of tissue.

4. The physician lifts back this flap, then proceeds to position the laser and directs the laser energy. The patient will hear a series of pulses as the laser reshapes the cornea.

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Why LASIK Sophisticated technology has made

LASIK a fast, virtually painless and very popular procedure. By 2001, over 2 million people world-wide had chosen LASIK for vision correction.

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Advantages of rigid lenses Gas-permeable rigid lenses have several

advantages over soft lenses: Visual acuity is better, especially in the

persons with corneal astigmatism. Allergic or toxic reactions to lens care

solutions are less frequent. Gas-permeable lenses last longer because

they are more durable than soft lenses. The cost of these lenses is usually less

because of the longer lens life and lower cost of the material.

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Why Rigid Lenses? Correction of refractive errors such as

myopia (nearsightedness) Prescribed to patients who have

suffered trauma to the cornea or who have corneal diseases such as keratoconus. 

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Why Rigid Lenses are bad Inability to transmit oxygen from the air

to the cornea. Risk of corneal swellingOther complications

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Electronic Bifocals The new glasses could benefit people

suffering from presbyopia, a condition in which faraway objects are in focus but those nearby appear blurry.

Spectacles that change prescriptions with the flick of a switch.

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Future Glasses : TV Glasses  Light-guide Optical

Element (LOE) technology, which sends an image through a lens as thin as 3mm. The result is a personal display that looks like ordinary eyeglasses but provides the wearer with a virtual large-screen television.