Documenta Ophthalmologica

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

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

Article

Abstract

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.

Keywords

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

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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

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