title: Photopic negative response of the human ERG: losses associated with glaucomatous damage.
abstract: OBJECTIVE
  To evaluate in glaucomatous eyes the photopic electroretinogram (ERG) negative response (PhNR), a component that follows the b-wave peak and is thought to be correlated with inner retinal activity.
  
  
  METHODS
  Eleven patients with open-angle glaucoma (OAG) and moderate field loss (Humphrey 30-2 [Humphrey Instruments, San Leandro, CA] mean deviation < or = -6 dB), eight with ocular hypertension (OHT), and eight age-matched normal subjects were tested. Optic discs of patients and control subjects were evaluated by confocal scanning laser ophthalmoscopy. ERGs were recorded to long-duration stimuli (250 msec) of photopic luminance (78 candelas [cd] /m2), presented in the macular region (12 degrees x 12 degrees field size) on a steady, adapting background. Amplitudes of the a-wave and b-wave and the PhNR were measured. Pattern reversal ERGs to 30-minute checkerboards were also recorded from patients and control subjects.
  
  
  RESULTS
  Compared with control subjects, patients with OAG showed reduced PhNR (average reduction: 62%, P < 0.01), but normal a- and b-wave amplitudes. In patients with OHT, PhNR and a- and b-wave amplitudes did not differ from control values. In individual patients with OAG, PhNR amplitudes were correlated positively with pattern ERG amplitudes (r = 0.80; P < 0.01) and central (12 degrees) perimetric mean deviations (r = 0.68; P < 0.05) and negatively with cup-to-disc area ratios (r = -0.79; P < 0.01) and cup shape measures (r = -0.78; P < 0.01).
  
  
  CONCLUSIONS
  Similar to that found in monkeys with experimentally induced glaucoma, the PhNR is selectively altered in human glaucoma. The correlation between PhNR losses and clinical parameter abnormalities suggests that this component depends on inner retina integrity and may be of clinical value for detecting glaucomatous damage.
authors.affiliation: Institute of Ophthalmology, Catholic University, Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Colotto
authors.forename: B
authors.initials: B
authors.lastname: Falsini
authors.forename: T
authors.initials: T
authors.lastname: Salgarello
authors.forename: G
authors.initials: G
authors.lastname: Iarossi
authors.forename: M E
authors.initials: ME
authors.lastname: Galan
authors.forename: L
authors.initials: L
authors.lastname: Scullica
mesh_terms: D000328:Adult; D004596:Electroretinography; D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D007429:Intraocular Pressure; D007834:Lasers; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000175:diagnosis / Q000503:physiopathology; D009887:Ophthalmoscopy; D009898:Optic Disk / Q000473:pathology; D010775:Photic Stimulation; D017949:Retinal Cone Photoreceptor Cells / Q000503:physiopathology*; D058609:Visual Field Tests; D014794:Visual Fields / Q000502:physiology