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Updated: Jul 4, 2026

Multifocal Electroretinograms
16:49

Multifocal Electroretinograms

Published on: December 4, 2011

Porcine global flash multifocal electroretinogram: possible mechanisms for the glaucomatous changes in contrast

Patrick H W Chu1, Henry H L Chan1, Yiu-Fai Ng1

  • 1Laboratory of Experimental Optometry (Neuroscience), School of Optometry, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China.

Vision Research
|June 25, 2008
PubMed
Abstract

Insights

This study dissects the cellular origins of the porcine global flash multifocal electroretinogram (mfERG). Inner retinal activity shapes the direct component (DC) and dominates the induced component (IC), offering insights into retinal disease mechanisms.

Area of Science:

  • Ophthalmology
  • Neuroscience
  • Retinal Physiology

Background:

  • The multifocal electroretinogram (mfERG) is crucial for assessing retinal function, particularly in conditions like glaucoma.
  • Understanding the cellular contributions to the global flash mfERG in animal models is essential for interpreting human studies.
  • Pharmacologic dissection offers a method to differentiate neural pathway contributions to retinal electrical responses.

Purpose of the Study:

  • To elucidate the cellular origins of the porcine global flash mfERG using pharmacologic agents and contrast variation.
  • To differentiate the roles of the inner and outer retina in generating mfERG components.
  • To investigate the impact of stimulus contrast on mfERG waveform characteristics.

Main Methods:

  • Global flash mfERGs were recorded from Yorkshire pigs under varying stimulus contrast conditions (99%–29%).
  • Pharmacologic agents, including isoflurane (ISO), tetrodotoxin (TTX), and N-methyl-d-aspartic acid (NMDA), were used to suppress inner retinal activity.
  • Specific pathway responses were isolated using 2-amino-4-phosphonobutyric acid (APB) and cis-2,3-piperidinedicarboylic acid (PDA) to isolate ON- and OFF-pathway signals.

Main Results:

  • The porcine mfERG comprises a direct component (DC) and an induced component (IC).
  • Inner retinal activity, including oscillatory wavelets (W1-W3), contributes significantly to the DC and shapes the IC.
  • After pharmacologic isolation of inner retinal contributions, the mfERG waveform resembles conventional mfERG, with remaining signals attributed to photoreceptors and bipolar cells.

Conclusions:

  • The DC of the porcine global flash mfERG is primarily generated by photoreceptors and ON/OFF-bipolar cells, modulated by inner retinal wavelets.
  • The IC is predominantly driven by inner retinal activity.
  • Contrast response functions are influenced by both outer retinal responses and inner retinal wavelets, with potential alterations in linearity upon loss of inner retinal cells.

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