Astigmatism

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Astigmatism

• Aetiology
• Change in refractive index of the lensindex
  astigmatism
• Decentration of lens or IOL
• Change in curvature of lens lenticonus
• Change in curvature of cornea causes
• Eyelids pressurewith the rule/against the rule
  astigmatism
• Pterygium
• Corneal scar
• Corneal degenerations
• Keratoconus

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Types of astigmatism

• Regular astigmatism2 principal
  meridianssimple,compound and mixed
• Irregular astigmatismmultiple meridians

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optics

• Conoid of Sturm
• Focal interval of Sturm
• Circle of least diffusion

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Sign and symptoms of astigmatism

• Blurred vision/running together of letters
• Asthenopia
• Head tilt in oblique astigmatism in children
• Half closure of the eyelids
• Keratoconus/pterygium/scarring of cornea
• Decentration of lens/IOL
• Optic nervehead oval or tilted in high
  astigmatism

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Investigations

• Retinoscopy
• Keratometry
• Keratoscopy with placidos disc
• Computerised corneal topography/videography

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Treatment of astigmatism

• Glassesspherocylindrical lenses
• Contact lens
• Surgery
• Suture cutting
• Astigmatic cuts
• Penetrating keratoplasty
• LaserPRK/LASIK