title: Visual evoked potential and psychophysical contrast thresholds in glaucoma.
abstract: OBJECTIVE
  We compared the diagnostic power of electrophysiologically and psychophysically measured contrast thresholds for the diagnosis of glaucoma. Additionally, we investigated whether combining results from the two methods improved diagnostic power.
  
  
  METHODS
  Seven-eight subjects between 40 and 88 years formed the main study group: 21 normal controls (9 males) and 57 glaucoma patients (30 males) were tested. Twenty-two younger control subjects were also tested. Contrast thresholds were determined for a 1 cpd sinusoidal grating, subtending 41° × 52° modulated at 14.3 rps. The thresholds were based on the same staircase method applied to visual evoked potential (VEP) and psychophysical responses (Psyc). Diagnostic power was assessed by the percent area under the curve (%AUC) of receiver operating characteristic plots.
  
  
  RESULTS
  Psyc showed significant age dependence, -0.10 ± 0.02 dB, while VEPs did not. Diagnostic performance for moderate and severe eyes combined was modest: Psyc 74 ± 9.0 % and VEP 72 ± 9.1 %, but improved significantly (p < 0.05) for a simple combined method, up to 90 ± 6.0 % for moderate disease. The combined method improved %AUC for all severities on average (p < 0.03). Canonical correlation analysis indicated that the four threshold measures contained independent information and that these independent dimensions were each correlated with glaucoma severity (p < 0.0015).
  
  
  CONCLUSIONS
  Combining the VEP and Psyc thresholds appeared to improve diagnostic power. Canonical correlation analysis indicated that they measured statistically independent aspects of glaucoma possibly related to disease severity. Adding the 20-s psychophysical test to a VEP test produced a significant benefit for a small time cost.
authors.affiliation: School of Optometry and Vision Science, University of New South Wales, Sydney, Australia.
authors.forename: Siti Nurliyana
authors.initials: SN
authors.lastname: Abdullah
authors.forename: Gordon F
authors.initials: GF
authors.lastname: Sanderson
authors.forename: Andrew C
authors.initials: AC
authors.lastname: James
authors.lastname: Vaegan
authors.forename: Ted
authors.initials: T
authors.lastname: Maddess
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015350:Contrast Sensitivity / Q000502:physiology*; D042241:Early Diagnosis; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D005901:Glaucoma / Q000175:diagnosis* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000175:diagnosis / Q000503:physiopathology; D011601:Psychophysics; D012372:ROC Curve; D012684:Sensory Thresholds / Q000502:physiology*