title: Standard Automated Perimetry: Determining Spatial Summation and Its Effect on Contrast Sensitivity Across the Visual Field.
abstract: OBJECTIVE
  To establish Ricco's critical area (Ac) using the 30-2 Humphrey visual field analyzer (HVFA) and thereby identify Goldmann test sizes that are within or outside complete spatial summation at all visual field testing locations. We also determined the suitability of using age normative data for different test sizes. Finally, by modifying current output measures (dB values), we provide a new method that allows comparison of contrast sensitivity when testing with different Goldmann test sizes within complete spatial summation.
  
  
  METHODS
  We used the HVFA in full threshold mode and measured thresholds for all five Goldmann test sizes in 12 observers. Normative data of Heijl et al. were used for age transformation and comparison.
  
  
  RESULTS
  All the data converted to a 50-year-old equivalent lie within 1 SD of expected variance for all test locations of the 30-2 paradigm. We established Ac values at all locations of the 30-2 paradigm and showed a systematic increase in Ac as a function of increased visual field eccentricity, consistent with previous studies. Age does not appear to affect Ac or the slope of partial summation for a wide range of visual field eccentricities tested using the HVFA. By equating spatial summation, we propose a new metric, dB*, that returns a uniform sensitivity value for different test sizes that are operating within complete spatial summation (i.e., follow Ricco's law).
  
  
  CONCLUSIONS
  We established that converting to age-equivalent thresholds and application of dB* principle advantageously allows comparison of data sets across age and test size at different locations of the visual field. By identifying the Ac across the visual field, it is now possible to systematically determine threshold changes across the 30-2 locations in ocular disease and further characterize the importance of testing within complete spatial summation in standard automated perimetry.
authors.affiliation: The School of Optometry and Vision Science, University of New South Wales, Kensington, New South Wales, Australia.
authors.forename: Sieu K
authors.initials: SK
authors.lastname: Khuu
authors.affiliation: The School of Optometry and Vision Science, University of New South Wales, Kensington, New South Wales, Australia 2Centre for Eye Health, University of New South Wales, Kensington, New South Wales, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Kalloniatis
mesh_terms: D000328:Adult; D000367:Age Factors; D000704:Analysis of Variance; D015350:Contrast Sensitivity / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012684:Sensory Thresholds / Q000502:physiology; D014785:Vision, Ocular / Q000502:physiology*; D058609:Visual Field Tests / Q000379:methods*; D014794:Visual Fields / Q000502:physiology*; D055815:Young Adult