title: Quantifying effects of retinal illuminance on frequency doubling perimetry.
abstract: OBJECTIVE
  To measure and quantify effects of variation in retinal illuminance on frequency doubling technology (FDT) perimetry.
  
  
  METHODS
  A Zeiss-Humphrey/Welch Allyn FDT perimeter was used with the threshold N-30 strategy. Study 1, quantifying adaptation: 11 eyes of 11 subjects (24-46 years old) were tested with natural pupils, and then retested after stable pupillary dilation with neutral density filters of 0.0, 0.6, 1.2, and 1.6 log unit in front of the subject's eye. Study 2, predicting effect of reduced illuminance: 17 eyes of 17 subjects (26-61 years old) were tested with natural pupils, and then retested after stable pupillary miosis (assessed with an infrared camera). A quantitative adaptation model was fit to results of Study 1; the mean adaptation parameter was used to predict change in Study 2.
  
  
  RESULTS
  Study 1: Mean defect (MD) decreased by 10 dB over a 1.6 log unit range of retinal illuminances; model fits for all subjects had r2> 95%. Study 2: Change in MD (DeltaMD) ranged from -7.3 dB to +0.8 dB. The mean adaptation parameter from Study 1 accounted for 69% of the variance in DeltaMD (P <0.0005), and accuracy of the model was independent of the magnitude of DeltaMD (r2< 1%, P >0.75).
  
  
  CONCLUSIONS
  The results confirmed previous findings that FDT perimetry can be dramatically affected by variations in retinal illuminance. Application of a quantitative adaptation model provided guidelines for estimating effects of pupil diameter and lens density on FDT perimetry.
authors.affiliation: Glaucoma Institute, SUNY State College of Optometry, New York, New York 10036, USA. bswanson@sunyopt.edu
authors.forename: William H
authors.initials: WH
authors.lastname: Swanson
authors.forename: Mitchell W
authors.initials: MW
authors.lastname: Dul
authors.forename: Susan E
authors.initials: SE
authors.lastname: Fischer
mesh_terms: D000221:Adaptation, Ocular / Q000502:physiology; D000328:Adult; D005260:Female; D006801:Humans; D007908:Lens, Crystalline / Q000502:physiology; D008029:Lighting; D008297:Male; D008875:Middle Aged; D008916:Miotics / Q000008:administration & dosage; D009184:Mydriatics / Q000008:administration & dosage; D017410:Practice Guidelines as Topic; D011680:Pupil / Q000187:drug effects / Q000502:physiology; D012160:Retina / Q000502:physiology*; D012680:Sensitivity and Specificity; D058609:Visual Field Tests / Q000379:methods*; D014794:Visual Fields / Q000502:physiology*
chemical_list: D008916:Miotics; D009184:Mydriatics