title: The association between nonstrabismic anisometropia, amblyopia, and subnormal binocularity.
abstract: OBJECTIVE
  To determine if thresholds exist for the development of amblyopia and subnormal binocularity with various types of anisometropia and to compare these with existing guidelines for the treatment or observation of anisometropia.
  
  
  METHODS
  The records of all previously untreated patients evaluated for isolated refractive error during a 42-month period were reviewed to assess the association between anisometropia, amblyopia, and subnormal binocularity.
  
  
  METHODS
  Three hundred sixty-one (361) patients with anisometropia and 50 nonanisometropic control participants, examined over a 42-month period, with no history of treatment for refractive error, amblyopia, or other ocular pathologic characteristics were evaluated.
  
  
  METHODS
  Uncorrected visual acuity in each eye, monofixation response, and degree of stereopsis were recorded for each patient. Patients with unequal or subnormal uncorrected visual acuity were retested with cycloplegic refraction. If the visual acuity was still abnormal, patients were retested while wearing spectacles.
  
  
  METHODS
  Degree and type of anisometropia were compared with incidence and severity of amblyopia and subnormal binocularity.
  
  
  RESULTS
  Spherical myopic anisometropia (SMA) of more than 2 diopters (D) or spherical hypermetropic anisometropia (SHA) of more than 1 D results in a significant increase in the incidence of amblyopia and decrease in binocular function when compared with nonanisometropic patients (P = 0.05). Increasing levels of SMA and SHA beyond these thresholds result in increased incidence and severity of amblyopia. Cylindrical myopic anisometropia (CMA) or cylindrical hyperopic anisometropia (CHA) of more than 1.5 D results in a significant increase in amblyopia and a decrease in binocular function (P = 0.05). Levels of CMA and CHA more than 1.5 D result in an increased incidence and severity of amblyopia.
  
  
  CONCLUSIONS
  This study supports existing guidelines for the treatment or observation of anisometropia and characterizes the association between the type and degree of anisometropia and the incidence and severity of amblyopia and subnormal binocularity.
authors.affiliation: Department of Ophthalmology, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas.
authors.forename: D R
authors.initials: DR
authors.lastname: Weakley
mesh_terms: D000293:Adolescent; D000550:Amblyopia / Q000209:etiology*; D015858:Anisometropia / Q000150:complications* / Q000175:diagnosis / Q000628:therapy; D002648:Child; D002675:Child, Preschool; D003867:Depth Perception; D005139:Eyeglasses; D005403:Fixation, Ocular; D006801:Humans; D015994:Incidence; D017410:Practice Guidelines as Topic; D014786:Vision Disorders / Q000209:etiology*; D015348:Vision, Binocular; D014792:Visual Acuity