title: Assessment of the reliability of standard automated perimetry in regions of glaucomatous damage.
abstract: OBJECTIVE
  Visual field testing uses high-contrast stimuli in areas of severe visual field loss. However, retinal ganglion cells saturate with high-contrast stimuli, suggesting that the probability of detecting perimetric stimuli may not increase indefinitely as contrast increases. Driven by this concept, this study examines the lower limit of perimetric sensitivity for reliable testing by standard automated perimetry.
  
  
  METHODS
  Evaluation of a diagnostic test.
  
  
  METHODS
  A total of 34 participants with moderate to severe glaucoma; mean deviation at their last clinic visit averaged -10.90 dB (range, -20.94 to -3.38 dB). A total of 75 of the 136 locations tested had a perimetric sensitivity of ≤ 19 dB.
  
  
  METHODS
  Frequency-of-seeing curves were constructed at 4 nonadjacent visual field locations by the Method of Constant Stimuli (MOCS), using 35 stimulus presentations at each of 7 contrasts. Locations were chosen a priori and included at least 2 with glaucomatous damage but a sensitivity of ≥ 6 dB. Cumulative Gaussian curves were fit to the data, first assuming a 5% false-negative rate and subsequently allowing the asymptotic maximum response probability to be a free parameter.
  
  
  METHODS
  The strength of the relation (R(2)) between perimetric sensitivity (mean of last 2 clinic visits) and MOCS sensitivity (from the experiment) for all locations with perimetric sensitivity within ± 4 dB of each selected value, at 0.5 dB intervals.
  
  
  RESULTS
  Bins centered at sensitivities ≥ 19 dB always had R(2) >0.1. All bins centered at sensitivities ≤ 15 dB had R(2) <0.1, an indication that sensitivities are unreliable. No consistent conclusions could be drawn between 15 and 19 dB. At 57 of the 81 locations with perimetric sensitivity <19 dB, including 49 of the 63 locations ≤ 15 dB, the fitted asymptotic maximum response probability was <80%, consistent with the hypothesis of response saturation. At 29 of these locations the asymptotic maximum was <50%, and so contrast sensitivity (50% response rate) is undefined.
  
  
  CONCLUSIONS
  Clinical visual field testing may be unreliable when visual field locations have sensitivity below approximately 15 to 19 dB because of a reduction in the asymptotic maximum response probability. Researchers and clinicians may have difficulty detecting worsening sensitivity in these visual field locations, and this difficulty may occur commonly in patients with glaucoma with moderate to severe glaucomatous visual field loss.
authors.affiliation: Devers Eye Institute, Legacy Research Institute, Portland, Oregon. Electronic address: sgardiner@deverseye.org.
authors.forename: Stuart K
authors.initials: SK
authors.lastname: Gardiner
authors.affiliation: Optometry and Vision Science, Indiana University, Bloomington, Indiana.
authors.forename: William H
authors.initials: WH
authors.lastname: Swanson
authors.affiliation: Devers Eye Institute, Legacy Research Institute, Portland, Oregon.
authors.forename: Deborah
authors.initials: D
authors.lastname: Goren
authors.affiliation: Devers Eye Institute, Legacy Research Institute, Portland, Oregon.
authors.forename: Steven L
authors.initials: SL
authors.lastname: Mansberger
authors.affiliation: Devers Eye Institute, Legacy Research Institute, Portland, Oregon.
authors.forename: Shaban
authors.initials: S
authors.lastname: Demirel
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D005188:False Negative Reactions; D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009901:Optic Nerve Diseases / Q000175:diagnosis*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014786:Vision Disorders / Q000175:diagnosis*; D058609:Visual Field Tests / Q000592:standards*; D014794:Visual Fields