title: Visual acuity deficits in children with nystagmus and Down syndrome.
abstract: OBJECTIVE
  To investigate the association between visual acuity deficits and fixation instability in children with Down syndrome and nystagmus.
  
  
  METHODS
  Prospective cross-sectional study.
  
  
  METHODS
  setting: Institutional. study population:Sixteen children (aged 10 months-14 years) with Down syndrome and nystagmus, and a control group of 93 age-similar children with unassociated infantile nystagmus. observation procedures: Binocular Teller acuity card testing and eye-movement recordings. Fixation stability was quantified using the nystagmus optimal fixation function (NOFF). An exponential model based on results from the control group with unassociated infantile nystagmus was used to relate fixation stability to age-corrected visual acuity deficits. main outcome measures: Binocular grating visual acuity and NOFF.
  
  
  RESULTS
  Visual acuity was 0.2-0.9 logMAR (20/30-20/174 Snellen equivalent) and corresponded to a 0.4 logMAR (4 lines) mean age-corrected visual acuity deficit. Fixation stability ranged from poor to mildly affected. Although visual acuity deficit was on average 0.17 logMAR larger (P = .005) than predicted by the model, most children had visual acuity deficit within the 95% predictive interval.
  
  
  CONCLUSIONS
  There was a small mean difference between the measured visual acuity deficit and the prediction of the nystagmus model. Although other factors also contribute to visual acuity loss in Down syndrome, nystagmus alone could account for most of the visual acuity deficit in these children.
authors: Retina Foundation of the Southwest, Dallas, Texas. Electronic address: jfelius@retinafoundation.org.
authors: Joost
authors: J
authors: Felius
authors: Pediatric Ophthalmology and Center for Adult Strabismus, Dallas, Texas.
authors: Cynthia L
authors: CL
authors: Beauchamp
authors: Pediatric Ophthalmology and Center for Adult Strabismus, Dallas, Texas.
authors: David R
authors: DR
authors: Stager
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D004314:Down Syndrome / Q000150:complications* / Q000503:physiopathology; D005133:Eye Movements / Q000502:physiology; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D009759:Nystagmus, Pathologic / Q000150:complications* / Q000503:physiopathology; D011446:Prospective Studies; D014786:Vision Disorders / Q000175:diagnosis / Q000209:etiology*; D014792:Visual Acuity