title: An amplitude ratio of pattern visually evoked cortical potentials.
abstract: OBJECTIVE
  We evaluated the amplitude of steady state pattern visually evoked cortical potentials (St PVECP) by comparing the amplitude ratio to transient PVECP (Tr PVECP) with the latency of Tr PVECP in macular, optic nerve, and chiasmal lesions.
  
  
  METHODS
  PVECPs were obtained by pattern reversal stimulation of both 3 times and 12 times per second from normal subjects and patients. The peak latency of the P100 component of Tr PVECP and the amplitude ratio (St PVECP/ Tr PVECP) were studied.
  
  
  RESULTS
  Ratio abnormalities were specifically found in patients with optic and chiasmal lesions who had normal Tr PVECP latency, but not in those with macular lesions. The ratio increased with visual improvement in optic nerve disease and chiasmal lesions.
  
  
  CONCLUSIONS
  The amplitude ratio was useful in detecting and monitoring optic nerve and chiasmal lesions, and in differentiating optic nerve and chiasmal lesions from macular lesions.
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015862:Choroid Diseases / Q000175:diagnosis*; D003937:Diagnosis, Differential; D005074:Evoked Potentials, Visual; D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009897:Optic Chiasm / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000175:diagnosis*; D010364:Pattern Recognition, Visual; D012164:Retinal Diseases / Q000175:diagnosis*; D014793:Visual Cortex