title: Optotype and grating visual acuity in patients with ocular and cerebral visual impairment.
abstract: OBJECTIVE
  To investigate the discrepancy between grating and optotype visual acuity in children with visual impairment due to brain and/or ocular abnormalities.
  
  
  METHODS
  Better eye acuity at 114 cm was studied in 81 patients (ages, 5-24 years) attending special schools for the visually handicapped. Fourteen patients had a brain abnormality, 48 had an ocular disorder, and 19 had both. Three acuity tasks were administered: detecting gratings in one of two positions, discriminating the orientation of single gratings, and discriminating the orientation of uncrowded Landolt-C optotypes. The three paradigms were similar in stimulus contrast, luminance, presentation mode, and psychophysical procedure.
  
  
  RESULTS
  Overall, grating acuity was better than optotype acuity, and the disparity increased with poorer optotype acuity. The largest discrepancies occurred in patients with brain abnormality, but disparities were also large in patients with optic nerve disorder. In patients with ocular and brain abnormality, grating acuities were only mildly better and not different from patients with only ocular abnormality. Grating orientation and grating detection tasks yielded similar thresholds, except in patients with cerebral visual impairment and with optic nerve disorder, whose grating detection acuity was better than grating orientation acuity.
  
  
  CONCLUSIONS
  Grating-to-optotype acuity superiority is typically large in visual disorders involving the brain. The closely matched test paradigms point to stimulus characteristics as the explanation. However, because the discrepancy decreased with grating orientation acuity instead of grating detection acuity, the complexity of the response required also plays a role.
authors.affiliation: Laboratorium voor Neuropsychologie, K. U. Leuven, Campus Gasthuisberg, Herestraat 49 BUS 504, B-3000 Leuven, Belgium. peter.stiers@med.kuleuven.ac.be
authors.forename: Peter
authors.initials: P
authors.lastname: Stiers
authors.forename: Ria
authors.initials: R
authors.lastname: Vanderkelen
authors.forename: Erik
authors.initials: E
authors.lastname: Vandenbussche
mesh_terms: D000293:Adolescent; D000328:Adult; D001927:Brain Diseases / Q000150:complications*; D002648:Child; D004192:Discrimination, Psychological; D005128:Eye Diseases / Q000150:complications*; D006801:Humans; D009901:Optic Nerve Diseases / Q000150:complications; D014786:Vision Disorders / Q000209:etiology* / Q000503:physiopathology*; D014787:Vision Tests / Q000379:methods; D014792:Visual Acuity