title: Near heterophoria in early childhood.
abstract: OBJECTIVE
  The purpose of this study was to measure near heterophoria in young children to determine the impact of early growth and development on the alignment of the eyes.
  
  
  METHODS
  Fifty young children (≥2 and <7 years of age; range of spherical equivalent refractive error -1.25 diopters [D] to +3.75 D) and 13 adults participated. Their eye position and accommodation responses, in the absence of optical correction, were measured using simultaneous Purkinje image tracking and photorefraction technology (MCS PowerRefractor, PR). The resulting heterophorias, and both accommodative convergence/accommodation (AC/A) and convergence accommodation/convergence (CA/C) ratios were then computed as a function of age, refractive error, and an alternating cover test.
  
  
  RESULTS
  The mean heterophoria after approximately 60 seconds of dissociation at a 33-cm viewing distance was 5.0 prism diopters (pd) of exophoria (SD ± 3.7) in the children (78% of children > 2 pd exophoric) and 5.6 pd of exophoria (SD ± 4.7) in adults (69% of adults > 2pd exophoric; a nonsignificant difference), with no effect of age between 2 and 6 years. In these children, heterophoria was not significantly correlated with AC/A (r = 0.25), CA/C (r = 0.12), or refractive error (r = 0.21). The mean difference between heterophoria measurements from the PR and the clinical cover test was -2.4 pd (SD = ±3.4), with an exophoric bias in the PR measurements.
  
  
  CONCLUSIONS
  Despite developmental maturation of interpupillary distance, refractive error, and AC/A, in a typical sample of young children the predominant dissociated position is one of exophoria.
authors: Indiana University School of Optometry, Bloomington, Indiana, United States.
authors: Erin
authors: E
authors: Babinsky
authors: Indiana University School of Optometry, Bloomington, Indiana, United States.
authors: Vidhyapriya
authors: V
authors: Sreenivasan
authors: Indiana University School of Optometry, Bloomington, Indiana, United States.
authors: T Rowan
authors: TR
authors: Candy
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D000328:Adult; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D009216:Myopia / Q000150:complications / Q000453:epidemiology / Q000503:physiopathology*; D009801:Oculomotor Muscles / Q000503:physiopathology*; D012307:Risk Factors; D013285:Strabismus / Q000453:epidemiology* / Q000209:etiology / Q000503:physiopathology; D014481:United States / Q000453:epidemiology; D055815:Young Adult
keywords: accommodation; heterophoria; refractive error; vergence; young children
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