title: Elevated vernier acuity thresholds in glaucoma.
abstract: OBJECTIVE
  In 1993, Piltz et al. observed that foveal vernier acuity thresholds for achromatic targets are elevated in patients with glaucoma. This study was undertaken to explore whether such elevated thresholds are present when subject groups are measured with targets of effectively equivalent contrast. Vernier acuity measures were also obtained with short-wavelength and frequency-doubled stimuli, to assess spatial hyperacuity performance in the short-wavelength-sensitive and magnocellular pathways, respectively.
  
  
  METHODS
  Twenty patients with glaucoma and 19 subjects with normal vision participated. All subjects had visual acuity of 20/25 or better. Achromatic two-dot vernier thresholds were obtained for 90% contrast dots. In addition, individual contrast thresholds to the achromatic dots were measured for each subject, and vernier thresholds were measured at 4, 8, 12, and 16 times contrast threshold. Short-wavelength vernier acuity thresholds were measured for blue dots presented on a bright yellow background. The stimulus for the frequency-doubling grating vernier acuity task was a 90% contrast, 1-cyc/deg, 25-Hz sinusoidal grating.
  
  
  RESULTS
  The glaucoma group demonstrated significantly higher foveal vernier acuity thresholds than control subjects for the blue-on-yellow stimulus (P = 0.002) and frequency-doubling grating stimulus (P < 0.001). No significant difference in vernier acuity between groups was found for the 90% contrast achromatic dots (P = 0.09), however a significant difference was found for the normalized contrast targets (P = 0.04).
  
  
  CONCLUSIONS
  Vernier acuity tasks can be used to demonstrate abnormal foveal function in glaucoma. Testing with visual-function-specific stimuli may be effective in identifying such dysfunction. Vernier acuity, or other similar hyperacuity tasks that assess spatial sampling, may be useful in the detection of early glaucomatous damage, before it is detected with traditional perimetric tests.
authors: Discoveries in Sight, Devers Eye Institute, Legacy Clinical Research and Technology Center, Portland, OR 97208-3950, USA.
authors: Allison M
authors: AM
authors: McKendrick
authors: Chris A
authors: CA
authors: Johnson
authors: Andrew J
authors: AJ
authors: Anderson
authors: Brad
authors: B
authors: Fortune
mesh_terms: D000368:Aged; D015350:Contrast Sensitivity / Q000502:physiology; D005902:Glaucoma, Open-Angle / Q000503:physiopathology*; D006801:Humans; D007429:Intraocular Pressure; D008875:Middle Aged; D012684:Sensory Thresholds / Q000502:physiology; D014792:Visual Acuity / Q000502:physiology*