Refractive errors

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REFRACTIVE ERRORS
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Emmetropia

• The emmetropic eye is normal eye
• Emmetropic eye parallel rays of light come to
• focus on the retina

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Ametropia

• Ametropia (Refractive error)
• Mismatch between axial length and refractive
  power
• Parallel light rays dont fall on the retina (no
  accommodation)
• Hyperopia hypermetropia
• Myopia
• Astigmatism

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Hyperopia/ Hypermetropia

• The parallel rays coming from infinity focus at
  point behind the retina ( unaccommodative eye)
• Axial hyperopia
• Curvature hyperopia
• Index hyperopia
• Positional hyperopia

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Symptoms and Treatment

• Young may not cause symptoms
• Eye strain
• Headaches
• Earlier presbyopia
• Corrected with convex lenses
• Spectacle
• Contact lens
• Surgery

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Myopia

• Is near-sightedness is that condition on in which
  parallel rays of light come to focus at point
  just in front of the retina
• Axial myopia
• Curvature myopia
• Index myopia
• Positional myopia

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Symptoms and Treatment

• Inability to see objects clearly at distance
• ? Squeeze eyes
• ? Burning sensation
• Corrected with concave lens
• ? Spectacle
• ? Contact lens
• ? Surgery

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Astigmatism

• Astigmatism is the condition in which rays of
  light are not refracted equally in all directions
  so that point focus on the retina is not attained
• Regular astigmatism
• Irregular astigmatism

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Regular Astigmatism

• Regular astigmatism is that refractive condition
  in which the axes of the principal meridians of
  the astigmatism are right angles to each other.
• Types
• Simple Astigmatism
• Simple Hyperopic / Myopia Astigmatism
• Compound Hyperopic / Myopic Astigmatism
• Mixed Astigmatism

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Regular Astigmatism, Types
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Irregular Astigmatism

• It is a refractive condition in which excess of
  the principal meridian are not right angle to
  each other.
• If the cornea has damaged by Trauma or
  inflammation or scar tissue.
• Irregularity of the corneal surface.

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Symptoms and Treatment

• Blurred vision
• Eye strain
• Corrected with concave/convex cyl
• Spectacle
• Contact lens
• Surgery

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Presbyopia

• Everyone becomes presbyopic with age
• Decreases accommodative ability of the ciliary
  muscle

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Symptoms and Treatment

• Inability to do near work
• Some patient complain that they have to hold the
  print farther away
• Fatigue
• Trouble with Threading a needle
• Corrected with convex lens
• ? Spectacle
• ? Contact lens

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• End..