Inner retina contribution to the flicker electroretinogram: A comparison with the pattern electroretinogram

V. Porciatti, B. Falsini

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

1. The macular ERG in response to luminance modulation of a uniform field [flicker ERG (FERG)] consists of two main harmonic components: a fundamental (IF) and a second harmonic (2F). Previous experimental and clinical evidence indicated that IF has a photoreceptoral origin, whereas 2F originates from postreceptoral sources. 2. To investigate the contribution of the inner retina to the FERG 2F in man, we evaluated this component in normal subjects and in patients with presumed inner retina dysfunctions. In addition, the FERG 2F data were compared with corresponding data of the pattern ERG (PERG second harmonic 2P), which is believed to originate from the innermost retina. 3. Macular (9 x 9 deg) steady-state (8 Hz) responses to both sinusoidal flicker and counterphasemodulated sinusoidal gratings (1.7 c/deg) were recorded from a cohort of normal subjects (n = 51) and from different optic nerve disorders: (i) optic nerve compression due to idiopathic intracranial hypertension (n = 22); (ii) multiple sclerosis with or without optic neuritis (n = 23); (iii) ocular hypertension and early glaucoma (n = 25). Fourier analysis of FERGs and PERGs was performed to evaluate I F, 2F and 2P amplitude and phase. 4. In normal subjects, 2F and 2P had comparable amplitudes but 2F phase was shorter by about O.5π rad (corresponding to 15ms at 8 Hz). The function relating 2F amplitude with stimulus area saturated at a relatively smaller area as compared to both IF and 2P. 5. In all patient groups, the IF was unaltered, whereas 2F and 2P were differently altered in amplitude. The 2F phase, unlike 2P phase, was considerably delayed in a substantial number of patients. 6. These results are in keeping with the view of a photoreceptoral origin for the FERG I F and multiple, postreceptoral sources for the FERG 2F, including a significant contribution from the inner retina. The FERG may have clinical value in subjects with opacities of the optical media.

Original languageEnglish (US)
Pages (from-to)435-447
Number of pages13
JournalClinical Vision Sciences
Volume8
Issue number5
StatePublished - Dec 20 1993
Externally publishedYes

Keywords

  • ERG
  • Flicker stimulus
  • Harmonic analysis
  • Optic nerve disease
  • Pattern stimulus

ASJC Scopus subject areas

  • Ophthalmology

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