Anisometropia

• Anisometropia


  Condition in which the refractive status of one eye differs from that the other
• Components of the term 'anisometropia'

  • an- (not)
  • -iso- (equal)
  • -metr- (measure)
  • -opia (vision)
• Isometropia


  Condition in which the refractive status is equal in the two eyes
• Antimetropia


  A form of anisometropia in which one eye is myopic and the other hyperopic
• Classification of anisometropia


  • By Type
  • By Degree
  • By Etiology
• Types of anisometropia by type

  • Anisometropia - different amount of the same error of refraction
  • Antimetropia - different type of errors such as hyperopia vs. myopia or spherical vs. astigmatic
• Types of anisometropia by degree

  • Low - differences in error totaling no more than 2.00 D
• Types of anisometropia by etiology


  • Congenital Anisometropia - differential growth of the eyeball of both eyes, hereditary
  • Acquired Anisometropia - created by trauma, pathology or the results of systemic changes, uniocular aphakia, wrong IOL power, trauma, keratoplasty
• Types of absolute anisometropia

  • Simple - one eye normal, other hypermetropic or myopic
  • Compound - both eyes ametropic, one higher refractive error
  • Mixed - one eye hyperopic, other myopic (antimetropia)
  • Simple Astigmatic - one eye normal, other has myopic or hyperopic astigmatism
  • Compound Astigmatic - both eyes astigmatic but unequal degree
• Binocular vision in anisometropia

  • In small degrees, binocular vision occurs
  • If difference >5D, patient loses binocularity
• Alternating vision in anisometropia

  • Patient uses hypermetropic eye for distance, myopic eye for near
• Amblyopia in anisometropia


  • If defect in one eye high and visual acuity not good, eye can be excluded from vision and become amblyopic
• Strabismus in anisometropia


  • Concomitant convergent squint occurs in children, eye with defect becoming convergent
• Anisometropia is a serious concern in newborns and young children because it can lead to amblyopia (impaired vision in one eye)
• Symptoms of anisometropia


  • Amblyopia (lazy eye)
  • Strabismus (cross-eyed)
  • Diplopia (double vision)
  • Eye strain
  • Headaches
  • Sensitivity to light
  • Complexity in reading
  • Nausea
  • Fainting
  • Sheer tiredness
  • Impaired depth perception
• Causes of anisometropia


  • Uneven growth in both eyes
  • Miscalculation of lens power during cataract surgery
  • Inborn defects in the eye
• Worth Four Light Test

  Clinical test used for assessing a patient's degree of binocular vision and binocular single vision. Also used to detect suppression of either the right or left eye.
• LEA Vision Test System


  Tests for amblyopia
• iScreen Vision


  Photoscreening technology that can detect anisometropia by creating a digital red reflex image of the eye
• Treatments for anisometropia


  • Spectacles
  • Contact lenses
  • Refractive laser (LASIK)
  • Phakic IOL
  • Clear lens extraction with IOL implantation
• Spectacles


  Can be tolerated up to maximum difference of 4D, higher than that diplopia may occur
• Contact lenses


  Advised for higher degrees of anisometropia
• IOL implantation


  For uniocular aphakia
• Refractive corneal surgery


  For unilateral high myopia, astigmatism, and hypermetropia