Delayed flicker ERG in CSNB suggests a post-photoreceptor contribution to the 30Hz response

S. H. Kim, P. A. Sieving

Research output: Contribution to journalArticlepeer-review

Abstract

Purpose. Although night blindness is the prominent feature in congenital stationary night blindness, the unusual photopic single flash ERG waveform suggests an abnormality in the cone to ON-bipolar pathway also exists. Cone flicker shows an unusual waveform but has normal implicit time. We studied cone flicker in CSNB by harmonic analysis to explore whether a delay in the fundamental component might be present which would suggest a post-synaptic contribution to this response. Methods. Cone 30Hz flicker ERGs were elicited with 4.2 cd-sec/m2 Ganzfeld xenon flashes. Eight Shubert-Bornshein type complete CSNB patients and 31 normal subjects were studied. The fundamental response was obtained by discrete Fourier transforms. Results. In normals, the fundamental 30Hz component had peak-to-peak amplitude of 51.2μv, SD=16.4 and phase of 331°, SD=13.9° (equivalent to 30.6 ms after each flash); 30 of 31 normals had phase < 360°. In CSNB, the cone flicker waveform showed broadened peaks and troughs, with mean amplitude 44.3μv, SD=18.0 (p=0.346). Although the flicker implicit time was within the normal range in 7 of 8 CSNB subjects, analysis of the fundamental component showed a significant delay to 361°, SD=16.1° (p<0.001), and 4 of 8 CSNB subjects had phase > 360°. Conclusions. The temporal delay in the fundamental component of the cone 30 Hz flicker ERG in CSNB was not apparent by traditional criteria of peak timing. The fundamental flicker component has been attributed to photoreceptors, but the temporal delay found for CSNB suggests that post-synaptic elements may also contribute. Caution is warranted when using the 30 Hz flicker ERG to localize pathology to a specific neural component of the retina.

Original languageEnglish (US)
Pages (from-to)S706
JournalInvestigative Ophthalmology and Visual Science
Volume37
Issue number3
StatePublished - Feb 15 1996
Externally publishedYes

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience

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