title: Pattern electroretinograms from hemifields in normal subjects and patients with glaucoma.
abstract: OBJECTIVE
  Because glaucomatous visual field loss predominantly occurs in one hemifield, a baseline ratio of pattern electroretinogram (PERG) hemifield amplitudes (upper field:lower field) was determined in normal subjects and then examined in patients with glaucoma.
  
  
  METHODS
  In 26 normal subjects and eight patients with glaucoma with typical arcuate field loss involving the test area (central 20 degrees), hemifield PERGs were recorded using checkerboard screens of check size 0.5 degrees and frequency 3.75 reversals per second (transient) and 15 reversals per second (steady state).
  
  
  RESULTS
  The ratios obtained for normal central upper:lower amplitudes were 0.95 +/- 0.13 (transient) and 0.93 +/- 0.10 (steady state Fourier second harmonic). Wide nasal-field (52 degrees x 42 degrees) PERG ratios recorded on two subjects confirmed that the ratio held across large retinal areas. The ratio did not change with age or check size. The ratio showed less variability between patients than PERG amplitudes. In the patients with glaucoma, the hemifield PERG amplitude correlated with summed visual field thresholds for that area. Patients with glaucoma could be discriminated from normals by an abnormal ratio (> 2 SD) in seven of the eight patients. In two additional patients with more peripheral scotomas, the ratio remained normal.
  
  
  CONCLUSIONS
  In normals, the upper:lower hemifield PERG ratio is slightly < 1.0 and remains stable with age. In glaucoma, visual field defects are associated with PERG reductions in the corresponding hemifield. An abnormal PERG hemifield ratio can be found in many patients, although more peripheral and symmetrical losses may still be missed.
authors.affiliation: Department of Ophthalmology, University of British Columbia, Vancouver, Canada.
authors.forename: S L
authors.initials: SL
authors.lastname: Graham
authors.forename: V A
authors.initials: VA
authors.lastname: Wong
authors.forename: S M
authors.initials: SM
authors.lastname: Drance
authors.forename: F S
authors.initials: FS
authors.lastname: Mikelberg
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology; D004566:Electrodes; D004596:Electroretinography; D005260:Female; D005902:Glaucoma, Open-Angle / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010364:Pattern Recognition, Visual; D012160:Retina / Q000502:physiology*; D014794:Visual Fields