Documenta Ophthalmologica

, Volume 113, Issue 3, pp 145–153 | Cite as

Utility in clinical practice of standard vs. high-intensity ERG a-waves

  • Mira Marcus
  • Lorella Cabael
  • Michael F. Marmor


Purpose: Standard ERG a-waves represent contributions from both photoreceptor and inner retinal cells, while the leading edge of the high-intensity a-wave is produced only by photoreceptors. This has raised questions about the value of the a-wave as an indicator of photoreceptor disease, and has led to suggestions for standardizing higher-intensity stimuli. Our objective was to compare the behavior of standard and high-intensity a-waves in clinical practice. Methods: Standard ISCEV (International Society for Clinical Electrophysiology of Vision) a-waves and high-intensity a-wave responses were recorded under scotopic and photopic conditions from normal subjects and from patients with photoreceptor dystrophies and other diseases. Results: The standard scotopic a-wave amplitude followed the high-intensity a-wave closely among patients with different diagnoses, and the results did not change significantly when cone a-waves were subtracted to isolate rod signals. The only exception was one patient with the enhanced S cone syndrome (ESCS) whose dark-adapted responses were cone-driven. Initial peak times clustered in a small range for both standard and high-intensity responses, and were not very sensitive to disease. Conclusion: High-intensity a-waves can show photoreceptor characteristics directly, and may help analyze some rare disorders. However, in our study the amplitude of conventional scotopic a-waves mirrored that of the high-intensity responses quite closely over a wide range of patients. This suggests that for practical purposes even if it is not perfect, the standard ERG is an excellent indicator of photoreceptor disease.


a-wave electroretinogram ERG high-intensity a-wave ISCEV standard 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    Marmor MF, Holder GE, Seeliger M and Yamamoto S (for the International Society for Clinical Electrophysiology of Vision). Standard for clinical electroretinography (2004 update). Doc Ophthalmol 2004; 108: 107–114Google Scholar
  2. 2.
    Hood DC and Birch DG (1993). Light adaptation of human rod receptors: the leading edge of the human a-wave and models of rod receptor activity. Vis Res 33: 1605–18PubMedCrossRefGoogle Scholar
  3. 3.
    Hood DC and Birch DG (1993). Human cone receptor activity: the leading edge of the a-wave and models of receptor activity. Vis Neurosci 10: 857–71PubMedCrossRefGoogle Scholar
  4. 4.
    Bush RA and Sieving P (1994). A proximal retinal component in the primate photopic ERG a-wave. Invest Ophthalmol Vis Sci 35: 635–44PubMedGoogle Scholar
  5. 5.
    Cideciyan AV and Jacobson SG (1996). An alternative phototransduction model for human rod and cone ERG a-waves: normal parameters and variation with age. Vis Res 36: 2609–21PubMedCrossRefGoogle Scholar
  6. 6.
    Jamison JA, Bush RA, Lei B and Sieving PA (2001). Characterization of the rod photoresponse isolated from the dark-adapted primate ERG. Vis Neurosci 18: 445–55PubMedCrossRefGoogle Scholar
  7. 7.
    Hood DC and Birch DG (1996). Assessing abnormal rod photoreceptor activity with the a-wave of the electroretinogram: applications and methods. Doc Ophthalmol 92: 253–67PubMedGoogle Scholar
  8. 8.
    Birch DG, Hood DC, Locke KG, Hoffman DR and Tzekov RT (2002). Quantitative electroretinogram measures of phototransduction in cone and rod photoreceptors: normal aging, progression with disease, and test–retest variability. Arch Ophthalmol 120: 1045–51PubMedGoogle Scholar
  9. 9.
    Marmor MF, Serrato A and Tzekov R (2003). Comparison of conventional ERG parameters and high-intensity a-wave analysis in a clinical setting. Doc Ophthalmol 106: 281–7PubMedCrossRefGoogle Scholar
  10. 10.
    Marmor MF, Jacobson SG, Foerster MH, Kellner U and Weleber RG (1990). Diagnostic clinical findings of a new syndrome with night blindness, maculopathy and enhanced S cone sensitivity. Am J Ophthalmol 110: 124–34PubMedGoogle Scholar
  11. 11.
    Gouras P, Eggers M and Mackay C (1983). Cone dystrophy, nyctalopia and supernormal rod responses. Arch Ophthalmol 101: 718–24PubMedGoogle Scholar
  12. 12.
    Hood DC, Cideciyan AV, Halevy DA and Jacobson SG (1996). Sites of disease action in a retinal dystrophy with supernormal and delayed rod electroretinogram b-waves. Vis Res 36: 889–901PubMedCrossRefGoogle Scholar

Copyright information

© Springer 2006

Authors and Affiliations

  • Mira Marcus
    • 1
    • 2
  • Lorella Cabael
    • 1
  • Michael F. Marmor
    • 1
  1. 1.Department of OphthalmologyStanford University Medical CenterStanfordUSA
  2. 2.Department of OphthalmologySoroka Medical Center and Ben-Gurion University of the NegevBeer-ShevaIsrael

Personalised recommendations