title: [Objective assessment of visual acuity with visual evoked potential].
abstract: OBJECTIVE
  To study the technique for objectively assessment of visual acuity with Pattern Visual Evoked Potential (PVEP) and Discrete Fourier Transform (DFT).
  
  
  METHODS
  Thirty-three normal eyes were tested in this study. Reversal square-wave gratings of eight different sizes (30, 20, 18, 12, 10, 6, 4, 2 min. of arc) were used as stimuli. The reversal rate of the stimuli was 10 times/sec. The harmonic amplitudes of VEP at 10 Hz were calculated with Discrete Fourier Transform. A relation curve between the harmonic amplitude and the size of grating was plotted from the data of each tested eye. Regression line was fitted to the data points in the approximately linear section of the curve which is near the threshold of zero amplitude. The threshold of the grating size was obtained by extrapolating of the regression line to zero amplitude, and the visual acuity was assessed with the threshold.
  
  
  RESULTS
  In seventy percent of tested eyes, the visual acuities assessed with VEPs were consistent with those measured with the International Standard Test Chart.
  
  
  CONCLUSIONS
  The VEP technique for visual acuity assessment is reliable.
authors.affiliation: National Ophthalmological Laboratory, Ministry of Public Health and Zhongshan Ophthalmic Center, Sun Yat-sen University of Medical Sciences, Guangzhou 510060, China.
authors.forename: M
authors.initials: M
authors.lastname: Yu
authors.forename: D Z
authors.initials: DZ
authors.lastname: Wu
authors.forename: J
authors.initials: J
authors.lastname: Liang
authors.forename: L
authors.initials: L
authors.lastname: Wu
mesh_terms: D000293:Adolescent; D005074:Evoked Potentials, Visual; D005583:Fourier Analysis; D006801:Humans; D008875:Middle Aged; D014792:Visual Acuity