title: Heterochromatic flicker electroretinograms reflecting luminance and cone opponent activity in glaucoma patients.
abstract: OBJECTIVE
  To measure heterochromatic flicker electroretinograms (ERGs) at high (36 Hz) and intermediate (12 Hz) temporal frequencies to evaluate luminance and cone opponent responses, respectively, in glaucoma eyes with (perimetric) and without (preperimetric) visual field defects.
  
  
  METHODS
  Flicker ERGs were recorded from one randomly chosen dilated eye of 32 patients (mean age, 61 ± 11 years; 15 men, 17 women) from the Erlangen Glaucoma Registry and from 24 healthy volunteers (mean age, 43 ± 11 years; 14 men, 10 women). Red and green light-emitting diodes in a Ganzfeld stimulator were sine wave-modulated in counterphase. The responses were measured at 36 Hz, the frequency at which ERGs reflect activity of the luminance pathway, and at 12 Hz, the frequency at which ERGs reflect chromatic activity.
  
  
  RESULTS
  Response amplitudes were similar in glaucoma patients and controls. Phase differences were observed in patients with visual field defects (perimetric) compared with the control group at 36 and 12 Hz in the first harmonic and second harmonic responses. Patients without visual field defects (preperimetric) showed phase differences for the second harmonic component at 36 Hz. No age effect on response amplitudes and phases was found in any of the subject groups (controls and patients).
  
  
  CONCLUSIONS
  The responses displayed phase differences but not amplitude differences in perimetric glaucoma patients at both 36 and 12 Hz, suggesting that both magnocellular and parvocellular pathways are affected. Preperimetric glaucoma patients also showed phase differences. The response phase may be sensitive to early dysfunction of the inner retina. (ClinicalTrials.gov number, NCT00494923).
authors.affiliation: Department of Ophthalmology, University Hospital Erlangen, Erlangen, Germany.
authors.forename: Mirella Telles Salgueiro
authors.initials: MT
authors.lastname: Barboni
authors.forename: Gobinda
authors.initials: G
authors.lastname: Pangeni
authors.forename: Dora Fix
authors.initials: DF
authors.lastname: Ventura
authors.forename: Folkert
authors.initials: F
authors.lastname: Horn
authors.forename: Jan
authors.initials: J
authors.lastname: Kremers
mesh_terms: D000328:Adult; D055253:Color Vision; D004596:Electroretinography; D005260:Female; D005500:Follow-Up Studies; D005902:Glaucoma, Open-Angle / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D008029:Lighting; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D058609:Visual Field Tests; D014794:Visual Fields