Effects of unsteady fixation on multifocal electroretinogram (mfERG)

P. H W Chu, Ho Lung Henry Chan, Susan J. Leat

Research output: Journal article publicationJournal articleAcademic researchpeer-review

14 Citations (Scopus)

Abstract

Purpose: To investigate the effect of unsteady fixation on the multifocal electroretinogram (mfERG) measurement in normal subjects. Methods: The mfERGs of 20 subjects with normal vision (mean age=23.5 years) were recorded with different levels of voluntary eye movements made to mimic unsteady fixation. Subjects were required to move their fixation regularly every 2 s between the center and the ends of a fixation cross, so that 51.2% of the time fixation was at the center and 12.2% of the time it was at each end of the fixation cross. Four different conditions were performed: central fixation (without voluntary eye movements) and with 2°, 4° and 6° magnitude of unsteady fixation. First-order kernel mfERG findings are presented. Results: Analysis of the ring responses indicated that the central mfERG amplitude was most affected by unsteady fixation. There was significantly reduced amplitude for 4° unsteady fixation and as expected, this reduction became larger with 6° unstable fixation. However, there was no significant effect on the center hexagon amplitude for 2° unsteady fixation. The amplitudes of the ring-2 responses were only affected in the 6° unsteady fixation condition. No significant change in implicit time was found for any level of unsteady fixation. Conclusion: These results suggest that mfERG amplitude is notsubstantially affected if fixation is maintained within the central stimulus hexagon. We conclude that, for patients with poor fixation, the accuracy of mfERG results may be difficult to interpret and the use of a fixation-monitoring system is desirable for ideal measurement. The depth of depression at the blind spot area may be another useful parameter to interpret the accuracy of mfERG results in patients with poor fixation.
Original languageEnglish
Pages (from-to)1273-1282
Number of pages10
JournalGraefe's Archive for Clinical and Experimental Ophthalmology
Volume244
Issue number10
DOIs
Publication statusPublished - 1 Oct 2006

Keywords

  • Blind spot
  • Central scotoma
  • Multifocal electroretinogram
  • Unsteady fixation

ASJC Scopus subject areas

  • Ophthalmology

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