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VISION CORRECTION

VISION CORRECTION. April 19. Vision problems. Many people have trouble focusing clearly at some point (e.g. teens as they grow, adults as they age) Almost any focusing problem can be improved by placing a lens in front of the eyes. Far-sightedness.

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VISION CORRECTION

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  1. VISION CORRECTION April 19

  2. Vision problems • Many people have trouble focusing clearly at some point (e.g. teens as they grow, adults as they age) • Almost any focusing problem can be improved by placing a lens in front of the eyes

  3. Far-sightedness • You can see distant objects clearly, but not nearby objects • The image comes into focus behind the retina because the ciliary muscles cannot make the lens thick enough to refract more sharply

  4. Correction • Adding a converging lens in front of the eye helps the light rays to form the image correctly on the retina

  5. Near-sightedness • The eye can see nearby objects clearly but not distant objects • Occurs because the eye cannot make the lens thin enough to refract light rays on the retina so image forms in front of the retina

  6. correction • A diverging lens causes light rays to diverge as they approach the eye • The eye itself then causes the light rays to converge properly and the light rays fall correctly on the retina

  7. astigmatism • The eye has an irregularly-shaped cornea or lens (e.g. football shaped) • Causes an image to be formed on more than one place on the retina, leading to blurry vision • Common symptoms: headache/fatigue

  8. Laser surgery • Reshapes the cornea, eliminating (or reducing) need for glasses • Risks include: long-term effects not yet known, poor night vision, dry eyes

  9. Colour blindness • True colour blindness (ability to see only in shades of grey) is very rare • More common is red-green colour vision deficiency (green/red look the same due to lack of red cone receptors)

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