title: Assessing spatial and temporal properties of perimetric stimuli for resistance to clinical variations in retinal illumination.
abstract: OBJECTIVE
  To develop perimetric stimuli for which sensitivities are more resistant to reduced retinal illumination than current clinical perimeters.
  
  
  METHODS
  Fifty-four people free of eye disease were dilated and tested monocularly. For each test, retinal illumination was attenuated with neutral density (ND) filters, and a standard adaptation model was fit to derive mean and SEM for the adaptation parameter (NDhalf). For different stimuli, t-tests on NDhalf were used to assess significance of differences in consistency with Weber's law. Three experiments used custom Gaussian-windowed contrast sensitivity perimetry (CSP). Experiment 1 used CSP-1, with a Gaussian temporal pulse, a spatial frequency of 0.375 cyc/deg (cpd), and SD of 1.5°. Experiment 1 also used the Humphrey Matrix perimeter, with the N-30 test using 0.25 cpd and 25 Hz flicker. Experiment 2 used a rectangular temporal pulse, SDs of 0.25° and 0.5°, and spatial frequencies of 0.0 and 1.0 cpd. Experiment 3 used CSP-2, with 5-Hz flicker, SDs from 0.5° to 1.8°, and spatial frequencies from 0.14 to 0.50 cpd.
  
  
  RESULTS
  In Experiment 1, CSP-1 was more consistent with Weber's law (NDhalf ± SEM = 1.86 ± 0.08 log unit) than N-30 (NDhalf = 1.03 ± 0.03 log unit; t > 9, P < 0.0001). All stimuli used in Experiments 2 and 3 had comparable consistency with Weber's law (NDhalf = 1.49-1.69 log unit; t < 2).
  
  
  CONCLUSIONS
  Perimetric sensitivities were consistent with Weber's law when higher temporal frequencies were avoided.
authors.affiliation: Indiana University School of Optometry, Bloomington, Indiana.
authors.forename: William H
authors.initials: WH
authors.lastname: Swanson
authors.forename: Mitchell W
authors.initials: MW
authors.lastname: Dul
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Horner
authors.forename: Tiffany
authors.initials: T
authors.lastname: Liu
authors.forename: Irene
authors.initials: I
authors.lastname: Tran
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D008029:Lighting; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation / Q000379:methods*; D011601:Psychophysics / Q000379:methods*; D012160:Retina / Q000502:physiology*; D012684:Sensory Thresholds; D058609:Visual Field Tests / Q000379:methods; D014794:Visual Fields / Q000502:physiology*; D055815:Young Adult
keywords: perimetry; retinal illumination; temporal vision