title: A new method of extrapolating the sweep pattern visual evoked potential acuity.
abstract: OBJECTIVE
  In order to compare the amplitude-spatial frequency (A-SP) regression method with amplitude-logVA (A-logVA) regression methods in extrapolating the sweep pattern visual evoked potential (SPVEP) acuity.
  
  
  METHODS
  We measured SPVEPs in 21 children and three adults using sinusoidally-modulated horizontal gratings as stimuli. The responses were averaged and displayed through discrete Fourier transformations. SPVER acuity was then estimated by using both the SPVEP amplitude- spatial frequency function (A-SP function regression method) and the SPVEP amplitude-log visual-angle function (A-logVA function regression method). Furthermore, the Bailey Lovie logMAR chart was employed to define visual acuity. Curve estimates were calculated to derive a correlation index (R) for each method.
  
  
  RESULTS
  There are significant differences (t = 2.71, P < 0.05) between the correlation indices of curves obtained using the A-logVA function (logarithmic model, 0.95 +/- 0.01) and that obtained by the A-SP function (inverse model, 0.92 +/- 0.02). The overall correlation coefficient (r) between logMAR acuity and acuity calculated by the A-logVA regression method was 0.32 (P < 0.05). The overall correlation coefficient (r) between logMAR acuity and acuity calculated by the A-SP regression method was 0.41 (P < 0.05). Paired t-tests show that SPVEP acuity from the A-logVA function was not significantly different from acuities of the logMAR function (t = 1.77, P = 0.09). The difference in their mean values is 0.14 +/- 0.08. However, SPVEP acuity calculated using the A-SP function regression method is significantly different from the acuity calculated from the logMAR function (t = 10.09, P < 0.01). The difference in their mean values is 0.41 +/- 0.04.
  
  
  CONCLUSIONS
  The amplitude-logVA function regression method is more accurate in estimating SPVEP acuity in normal subjects with good visual acuity.
authors.affiliation: Department of Ophthalmology, Peking University People's Hospital, Beijing, 100044, People's Republic of China.
authors.forename: Peng
authors.initials: P
authors.lastname: Zhou
authors.forename: Ming-Wei
authors.initials: MW
authors.lastname: Zhao
authors.forename: Xiao-Xin
authors.initials: XX
authors.lastname: Li
authors.forename: Xiao-Feng
authors.initials: XF
authors.lastname: Hu
authors.forename: Xi
authors.initials: X
authors.lastname: Wu
authors.forename: Lan-Jun
authors.initials: LJ
authors.lastname: Niu
authors.forename: Wen-Zhen
authors.initials: WZ
authors.lastname: Yu
authors.forename: Xiu-Lan
authors.initials: XL
authors.lastname: Xu
mesh_terms: D000328:Adult; D002648:Child; D002675:Child, Preschool; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009216:Myopia / Q000503:physiopathology; D014792:Visual Acuity / Q000502:physiology*